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Project Log 84: Screw it, let's freaking do it.⁵
06/21/2024 at 16:43 • 5 comments
Tuesday, 18/06/2024, 19:06

Well, I’m writing this in a google docs first and then later posting on hackaday.io because it is having a lot of trouble staying up.

Power Source:

So I will write what is in my mind right now:

So, I’m kinda pissed off because it seems like the molten carbonate fuel cells and molten hydroxide fuel cells kinda fricking suck and are equally dangerous. Plus, I don’t really need lithium carbonate in a lot of quantities because it is more of a catalyser for the carbonate solution. Most of the articles that I could find on the subject said that they used a nickel anode and a cathode with a layer of lithium while only using potassium carbonate and sodium carbonate.

On top of that, one of the recurring problems is that the molten carbonate fuel cell also needs the CO2 from the exhaust of its own reaction to be mixed back for whatever reason. And it also can suffer from layer separation, since the carbonates have different densities (akin to what happens to water and oil).

And well, I also revisited the idea of using magnetohydrodynamic generators, but I’m really not confident on its resulting performance and on its viability while building it homemade.

The idea is simple:
1. First, using the plasma jet engine to power a tip-jet rotor.
2. The tip-jet rotor will rotate an axial compressor.
3. The air from the air compressor will go to a plasma jet rocket engine.
4. On top of the plasma, a fuel (gaseous, liquid or powder) will be introduced, increasing the performance of the plasma jet rocket engine.
5. On the combustion chamber and nozzle there will be a Magnetohydrodynamic generator coil that will turn the flow of air and combustion into electricity.
6. The electricity will be used to maintain the reaction going just like in a conventional jet engine and the excess used to power the other systems.
7. This will be an Air-Breathing Plasma Jet Magnetohydrodynamic Rocket Engine Generator (ABPJMREG).
- The plasmatron turns hydrocarbons into hydrogen and CO/CO2, so MAYBE the plasma can end up doing something similar on either making more complex reactions and/or more toxic byproducts.
- Another problem is the amount of noise, heat, vibration, fumes etc.
Obviously there will be a LOT of variables and a LOT of thought on the type of material required to make this beast to work continuously, and on top of that, dealing with this kind of machine can easily cause my own death.

Source: https://www.researchgate.net/publication/343747256_Electrical_properties_of_gadolinia-doped_ceria_for_electrodes_for_magnetohydrodynamic_energy_systems?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6Il9kaXJlY3QiLCJwYWdlIjoiX2RpcmVjdCJ9fQ

And although ChatGPT (that f*cking stupid chat bot) keeps saying the efficiency of the MHD systems is “90%” the own sources it shows to me prove otherwise, this article (which gpt itself sent to me as the said source) said the magnetohydrodynamic generator on the rocket engine achieved a maximum of:

“There are energy losses in the MHD channel. These include friction with the wall, heat transfer, electrical resistance of the gas, and electrical losses at the ends of the channel and the conductor walls (17:331). These losses give linear MHD channels using gases at 2000-3000K only a 15% efficiency (35:31).“

The pancake type is more efficient, but it is said to be 30% efficient. I don’t see the appeal of working my butt off on a glorified plasma furnace that will blow up in my face, melting years of work and thousands of moneys into a giant pile of molten slag.

Source: https://en.wikipedia.org/wiki/Magnetohydrodynamic_generator

Source: https://www.researchgate.net/publication/358260240_Existence_of_an_optimized_stellarator_with_simple_coils?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6Il9kaXJlY3QiLCJwYWdlIjoiX2RpcmVjdCJ9fQ

This image is from a supposedly “optimized Stellarator fusion reactor”, only god can tell me if any fusion reactor structure would be practical/useful for MHD generators…

This article is about a nuclear enchanced MHD generator which uses molten metal, and it still only achieves maximum 30% alone. The metal it uses is Rubidium, but I could use Tin, Indium, Bismuth and Lead. And through that, I would increase the surface area in which the liquid moves, probably increasing the efficiency.

Actually, this gave me the idea of using a molten metal magnetohydrodynamic heat engine. The liquid metal would be heated by a furnace and move through some piping, turning the motion into electricity. I found this article about an open cycle coal powered MHD generator that is said to achieve 60% of efficiency, however, the thing was designed for 1.5 Megawatts (1,500,000 watts). Five times more power than the peak power designed for the mech. The magnet used in this was 5000 tons alone (dunno if it is a typo mistake or it is actually 5 million kilograms), so you can imagine how heavy this thing would’ve been.

It would be really fucking nice (and cool) if I could fit a MHD generator in my backpack and produce enough energy to power up a city, but unfortunately, reality isn’t that convenient.

The Molten Fuel Cells aren’t any better and the safer solution would be to use a conventional combustion engine generator.

And a conventional hydrogen fuel cell would be my first choice in ages, but there is absolutely no practical way of storing hydrogen gas in any shape or form. Even the best metal hydrides can only store 10% of its own weight in hydrogen, and assuming an efficiency of 50% in conversion to electricity, I would need 4,2kg of hydrogen per hour at 100hp. This would require 400kg of metal hydrides for 10 hours of activity.

What made me think of using molten fuel cells and magnetohydrodynamic generators in the first place is fuel cost and accessibility.

100 liters of fuel (whatever type) to make this mech going would be the cost of a minimum salary (or more), and the only fuels that are somewhat possible to make at home are Wood-Methane, Methanol and Ethanol. Unless I suddenly find a charcoal powered piston engine or a way of making “liquid charcoal”, I don’t think that the combustion engine will be a good option.

And yes, there are “charcoal” engines that were popular during the war, but in reality, those engines had a SynGas generator using wood or charcoal, which has half of the energy density of butane.

There is liquid coal or “coal to liquid” process in which coal is converted into diesel or gasoline using a huge fricking plant.

Lastly, the only combustion engine that I could find that uses charcoal without a chemical process or extra steps are turbine engines. And those aren’t as simple and cheap as making a piston engine.

I like all the ideas I presented, but when it comes to power-to-weight ratio, practicality, efficiency, cost, complexity and safety, all of them fall short.

Well, personal note: if it was this simple to make a portable power source, there wouldn’t be a concept such as “world energy crisis”.

And all of this fucking sucks.

However, before we delve into the next and last option, let me try to check the possibility of making the thermoelectric generators one last time.

The only reason that I got the will to try to design a TEG with around 30% to 40% is because I didn’t care enough to understand how it works at the first time because it used gold.

Source: https://www.nature.com/articles/s41586-022-04473-y

The gold is used because it is a great reflector of infrared light, that is why the hobbes telescope uses it. And the materials were tuned to both work as a thermoelectric device and as a photovoltaic device, a literal solar cell-TEG hybrid. That is why it uses germanium and GaAs (gallium arsenide) and other types of materials, they are meant to filter all other frequencies and only let infrared radiation pass through.

The article says that it achieved higher efficiency because of this filtering, but I want to understand why only allowing infrared to pass and not other bandwidths, I mean, the more sources the better, no?

Well, the idea for now is to do the following:
1. Make a thermoelectric and thermophotovoltaic using cheaper materials.
2. Make reflectors with cheaper materials
3. Structure the TEG/TPV materials in a way that maximizes absorption of heat and radiation (there are a lot of papers on that).
4. Add a magnetohydrodynamic generator and a plasma source to make it as hot as possible (3000 to 5000ºC). The MHD will stop the flames/plasma from destroying the materials.
5. Use a blanket of air between the heat source and the actual contact with the TEG/TPV.
6. Make a really long path for both MHD, TEG and TPV to absorb as much as possible.
7. Add tin as a liquid metal coolant in the primary radiators.
8. Connect the primary radiator to TEG/TPV and then connect to the secondary oil radiators (the oil/liquid could be conductive to allow MHD generation).
9. Connect the secondary oil radiators with TEG/TPV to the tertiary air radiators.
10. Vent the heat from the tertiary radiators into the air input, recycling heat into the system.
11. Pass the already heated air through the exhaust heat exchanger to recycle even more heat.
12. Introduce the heated air into the turbocharger into the combustion chamber and add a plasma source for the MHD generator.
13. And maybe making everything in a circle, just like the stellarator.
I also need to find what would be the best size for the plasma flame, too big and it may not allow the TEG/TPV/MHD to fully absorb the energy, too little and numerous and the heat source may not be hot enough to make the system work.

And then make it 3D printable…

All of this is starting to sound more complicated than the charcoal engine, to be honest…

Well… I was expecting to find cheaper materials that have similar properties to the ones that the article has, like using aluminium and/or tin as the heat/infrared reflector (because mirrors can reflect infrared too), but… Well, the problem is that there really isn’t any other material that can reach the heights of the ones used in the TPV (thermophotvoltaic) with 40% of efficiency.

MAYBE by using a little more expensive materials like silicon carbide, boron based compounds, nitride related materials and sulfide materials (like Lead Sulfide), I could increase the efficiency from less than 5% to around 15% that is the normal efficiency of non-precious materials TEG/TPV cells using optimized surface area for better absorption (which I was able to find articles saying they reached even 23% efficiency only doing that).

Then, MAYBE by using the MHD would add another 15% of efficiency, with pseudo-photovoltaic cells (like DIY solar panels) and any other type of thermoelectric generation device, just MAYBE I could increase the efficiency to a maximum 30% or even 40%.

And I did find out that plasma is a type of “blackbody” that can absorb any kind of wavelength/frequency and emit it as thermal radiation, but it needs to be really opaque in order to work, unlike in a Tokamak which works in near vacuum. So, maybe an additional 2% of efficiency? lol

Taking into consideration all the nuisances that would come with a charcoal engine electric generator and the compound thermoelectric generator (this aberration I’m suggesting), I don’t really know which to choose.
1. An experimental never tested thermal to electrical energy conversion/generation
2. A well understood diesel converted to charcoal engine with a conventional electric generator.
Just now I discovered that there are other thermoelectric effects that can be used to generate power:
- Thermionic Converter:
  A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization or electron impact ionization in a plasma) to neutralize the electron space charge.
  Maybe this is a simpler example to understand, you don't necessarily need to make the gaseous media to be some weird exotic chemical or vacuum, just working on air/plasma can work.
  It is said that Thermionic Converters have higher effiicencies (around 20%) than TEGs, but need higher temperatures and a medium of vacuum, rarefied conductive gases (like mercury) or plasma to work properly.
- Pyroelectric generator:
  Pyroelectricity is a property of certain crystals which are naturally electrically polarized and as a result contain large electric fields. Pyroelectricity can be described as the ability of certain materials to generate a temporary voltage when they are heated or cooled. The change in temperature modifies the positions of the atoms slightly within the crystal structure, so that the polarization of the material changes. This polarization change gives rise to a voltage across the crystal. If the temperature stays constant at its new value, the pyroelectric voltage gradually disappears due to leakage current. The leakage can be due to electrons moving through the crystal, ions moving through the air, or current leaking through a voltmeter attached across the crystal.
There was actually more designs and machines designed to convert heat to electricity, but the google results lead me to weird websites and videos. That is how I found out about the "blackbody" property of plasma, because it lead me to a scam/conspiracionist website of a guy that claimed making a 100% efficient way of converting infrared radiation into electricity by using plasma.
... Which would break the laws of thermodynamics... And the author/weird fans were convinced that the "scientist groups" were "persecuting" him because they did not accept his "free energy generator". :|

Anyway, the idea would be to add mutiple types of thermal to electric generators/converters in order to squeeze as much electricity as possible from the heat source.

... But I feel like this is just an stupid idea for some reason... My guts tell me that I can't simply add up the efficiency of different types of generators in order to absorb more power... Well... MAYBE stacking the copper/copper oxide photovoltaic cells with the thermoelectric generators would work, since you don't necessarily need the TEGs to be in direct contact with the heat source. So stacking them would actually work.
But I don't know about the pyroelectric and thermionic generators, not to mention that I don't know crap about a cheaper way of making thermophotovoltaic cells.

Also, I forgot to say, but I saw a few articles that had some charts about thermoelectric, magnetohydrodynamic and stirling engines that had really high efficiencies based on the temperature.
So all of these generators actually had effiicencies increasing from a single number to even 40% with higher temperatures.

Diesel Engine to Charcoal Engine:

Well, well, well, look at that, after 2 days looking at random crap spilled by google, it finally shows what I wanted.

There is research on the performance of diesel engines using charcoal/coal slurry, now I “just” need to read all the 29032993232 pages.

“Charcoal emulsification
In order to be pumped, the charcoal powder had to be mixed into an emulsion of diesel and fatty acids to produce a slurry. The target of these studies was to obtain a charcoal slurry with viscosity less than 100 cP at 25 C and high calorific value.
Charcoal Charcoal type: cedar.
The particle’s median diameter 10.33 microm, Fig. 5
Water Distilled water
Diesel Summer type, 6.5 cSt at 25 C
Weight ratio: Charcoal:diesel:water 25:72.2:2.8 (with surfactant)
Mix speed Mixed by homogenizer at average speed: 6000 rpm, Fig. 5
Viscosity For measurements, a rotor type viscometer was used.
Viscosity was measured at spindle’s speeds: 60 rpm, 6 rpm, 0.3 rpm. Temp.
Both production and measurements took place at room temperature.”

Source: https://www.researchgate.net/publication/251581755_Combustion_characteristics_of_a_charcoal_slurry_in_a_direct_injection_diesel_engine_and_the_impact_on_the_injection_system_performance

In the end the project said that it would be more efficient to use indirect injection of charcoal powder instead of slurry.

Well, since we are already here, then why not use compression ignition anyway?

It still needs a spark plug for controlled ignition.

Now, I need to learn it and find a 4 stroke diesel engine that is best for this job, especially if it is a single cylinder. Just like one of those super high compression ratio engines for ships. On top of all that, building it to be an adiabatic engine.

Well, it seems like compression ratio isn’t everything when it comes to engine horsepower… It is possible to double the output of a combustion engine by simply increasing the air input pressure with a few PSI.

I was intending on making the engine with the fastest rpm possible, so the piston would need to be as small as possible, but… It is said that the maximum speed diesel engines can is 5500 rpm because diesel doesn’t burn fast enough, although I would like to doubt that if the engine in question is adiabatic (and using charcoal), which could lead to fast combustion… Maybe?

Source: https://www.researchgate.net/publication/369666852_The_influence_of_thermal_barrier_coating_on_an_LHR_engine_fueled_by_soybean_biodiesel_blended_with_various_additive_spectrums_Performance_combustion_and_emission_analysis

Obviously, I’m not going to simply coat a polymer engine with ceramic, but make an insulated composite base material for the engine and then add the polymer on the outside.

The electric generator will be just like I was planning before:

A brushless stator and an electromagnetic rotor, the brushless stator will increase its amperage, thus, its resistance to torque gradually until the speed of the motor is slightly reduced, then, through that you can tune it whenever you like. For example, you could lower the amperage when the motor is rising and increase it when it is descending, allowing the motor to only experience resistance on its power stroke.

Well, f*ck.

As always, it took me a while to figure out the obvious: It is really fricking hard to design an engine and generator from scratch, so now I need to find a diesel engine that can output 100 to 300 horsepower with as few cylinders as possible. I was thinking of a single cylinder because (supposedly) it would be easier to make, but I doubt I will find a single cylinder engine (and a generator at that) with 300hp that isn’t as big as a building…

Well, I kinda found it, but it is not that simple (as always).

The thing is: I’m going after the biggest engines out there and divide the number of cylinders by the output power, and even if a single cylinder produces too much power, then I will “just” reduce its size. Or take an already existing engine and increasing its size x amount of times

I'm still procrastinating, but for some reason I went to check on batteries and the like.

Not because I found a crazy battery that has thousands of watt-hours, but because I went calculating its weight based on the amount of joules it would provide.

Wattage is like kilometers per hour and Joules are the exact distance you travelled, so even though you went to 100 km/h, you only went that fast for around 100 meters. If you were to keep going for 100 km/h for an entire hour, then yes, you would have travelled 100 kilometers.
The same apply to wattage and amount of joules.

So, an Iron Air battery that could supply around 1,000 watt-hour per kilogram, would store around 1000 x 3600 joules per hour in each kilogram.
So, 3,600,000 or 3 MJ per kilogram (gasoline can provide 46 MJ/kg).
- 100 horsepower hour = 268,451,953 joules, or 268 MJ
- 268,451,953 joules / 3,600,000 joules = 74.5699869444
- I would need an iron air battery with at least 74 kilograms for every hour consuming 100 horsepower.
However, my interest peaked because I was wondering if I could throw away the oxided iron in order to be lighter and consume less energy for every moment.

Then, I also thought about supercapacitors and my little research that I've made with dielectric elastomers, which are the same thing.

For some reason unknown to me, supercapacitors use an electrolyte to store the charge as both ions and electrons, unlike dielectric elastomers.

And it got me wondering:

How much energy I could store with those dielectric materials?

I was talking about materials with dielectric strength/voltage breakdowns around 50 KV or even more, with dielectric constants around 80 to 300 using titanium dioxide and lead zirconate titanate (which have 500 to 6000).

So I got to a capacitance calculator and I inserted these values, however, I don't know how correct these values are.

So, I found this:

"And so, the dielectric constant for teflon is 2.1, and we multiply that by permittivity of free space 8.85 times ten to the minus 12 farads per meter. And then, multiply by the area of five square meters and divided by 0.01 millimeters, which is 0.01 times ten to the minus three meters. And, this gives 0.93 microfarads as the capacitance."

Source: https://collegephysicsanswers.com/openstax-solutions/find-capacitance-parallel-plate-capacitor-having-plates-area-500-m2-are

So, doing the same thing with the supposedly material with 300 as dielectric constant:
- 300 x 8.85x10^-12 = 2.655e-9 farads per meter
- Capacitance calculator: 0.00000331875 farads
The area was around 1.25 m² because I took a cylinder volume calculator and made a cable with 10cm of length and 4cm of thickness, which would be a cable for 1000 amps. Then I've input the values of a rectangle volume caculator and matched the volume from teh cylinder with the rectangle with 1mm of length, 10cm of height and around 125cm ofwidth.

Which when I've inputed on the rectangle area calculator, gave me around 1.25 m² of surface area.
(this thing would weight around 10kg btw)

I inserted then the separation distance of 1mm and the calculator gave me a capacitance of 0.00000331875 Farads.

When I inserted the capacitance and the voltage (50,000 volts) on the capacitor energy calculator, it gave me the value of: 4,148.4 joules for every 10 kilograms of capacitor.

Even if I changed it from copper to conductive polymer, it would still be 4 kilojoules per kilogram (10 times lighter). :|

By the way, 8.85x10^-12 = 0.00000000000885.

So I would need to increase the capacitance by 112,994,350,282 times in order to increase its capacitance to 1 farad per meter. :|

Well, now I know why the electrolyte is required alright...

A conventional supercapacitor stores around 20,000 Joules of energy per kilogram, and it normally uses aluminium oxide as the dielectric material, which in turn, has a dielectric constant of around 10.

Assuming that I use the diamond powder to increase the dielectric constant to 1000, then I would store 100 times more energy, which would be around 2 MJ (2 million joules) per kilogram.

The dielectric consant is related to the temperature of the material, some increase with heat, some decrease with heat.

Maybe using these changes could increase the energy density of supercapacitors, although, the electrolyte would need to be comfortable in these conditions in order to work.

Well, I don't know if I can even approximate how much energy it would be stored, since the thickness of the aluminium oxide layer in aluminium supercapacitors is around 4 nanometers (or 0.00004 millimeters). And on top of that, it is highly porous to increase its surface area without increasing its size.

It is really a complex science and at the moment google doesn't show me a single article about the effect of temperature and dielectric material on the energy density of supercapacitors. :/

... And I doubt this would change too much, a graphene supercapacitor (the most energy dense supercapacitor) was able to achieve 88,1 wh/l, or 317,160 joules per liter (which is probably per kilogram too).

... So, another useless detour. lol

Well, I was mentioned in a Mech video (not as this account's name) and I saw a bunch of comments talking about a variety of different manners of storing energy.

For example, there are molten batteries and molten-air batteries. Which I never heard about.

Molten-air battery's storage capacity among the highest of any battery type (phys.org)

Accordingly to this news article, a carbon molten air battery would have around 28 MJ (megajoules = 1 million joules) per kilogram of mass.
I would need around 10 kilograms of this stuff for every 100 horsepower-hour that I would consume.

The page links to an article on the subject, I gotta study about it to check if is going to work in a practical manner.

I do hope they don't need some acidic/toxic electrolyte to work tho...

Well, too bad, in this specific article they use lithium carbonate and barium carbonate for both the iron and carbon battery (I didn't care about the vanadium battery because it is expensive).

So, if I'm going to use molten lithium carbonate at 800ºC at the risk of losing charge to the formation of CO2, then why not just use the Molten Carbonate Carbon Fuel Cell?

(I just checked, most articles still use molten carbonates based on lithium, sodium and potassium, just like molten carbonate fuel cells)

... For some reason I feel less pro-active these days, I don't have energy for anything at the moment. Maybe I should stick with Molten Carbonate or Molten Hydroxide fuel cells instead of making the adiabatic carbon-diesel engine with the brushless generator.

Before writing about the new coil actuator down below the off-topic section, I do think this project log in specific is pretty useless, I just complain that other methods aren't that viable and jump straight to a combustion engine. Which is the one of the most complex systems I suggested.

Besides, I could also use the TEG generators to recycle some of the wasted heat of the Molten carbonate fuel cells.

Source: (PDF) FUEL CELLS – MOLTEN CARBONATE FUEL CELLS | Materials and Life Considerations (researchgate.net)

I just found this concept for a molten carbonate fuel cell, it looks just like a conventional fuel cell and I do think this way it could allow for a system to properly control the electricity output.

Source: (PDF) Temperature influence on six layers samaria doped ceria matrix impregnated by lithium/potassium electrolyte for Molten Carbonate Fuel Cells (researchgate.net)

While looking for other molten carbonate fuel cell structures I found out you can literally use anything that is carbon based, even wood and hydrocarbons, but I'm not really going to test inserting gasoline in a 700-800 ºC furnace, lol

Actually, if I'm not mistaken, they process the fossil fuels in order to take out elements like sulfur and then insert into the fuel cell just like that. :|

Now I'm doubt which one I should choose: molten air carbon battery or molten carbonate fuel cell.
- Both need to be at 650-800ºC to work
- Both need carbon.
- Both need energy heat itself up and mantain functionality
- Only Molten carbonate needs air intake and co2 recycling
- I would need to find an energy source to charge the batteries
- I would need need to find fuel for the carbonate
- The molten battery could have multiple cells around the body, both risky and redundant
- The molten carbonate would only need a single cell
- The battery needs to carry all the 200kg of carbon while the fuel cell consumes it
Oh well, I guess this is settled

Just found this video, common table salt can become a ionic liquid until its molten (around 800ºC). So maybe this could be an useful material for the carbonate fuel cell, of course, assuming that the carbonates aren't working as an ionic fluid already, since these are considered "salts".

Source: https://www.sciencedirect.com/science/article/abs/pii/S0378775301009429

This is a 250 KW Molten Carbonate Fuel Cell that uses hydrocarbon gas fuel by the way...

Is the idea of maintaining the electrolyte solution in a ceramic bucket even remotely viable?

I was even thinking on mixing the carbonates with their equivalent carbonates: sodium silicate, potassium silicate and lithium silicate and using a sacrificial fiber material, so it becomes some kind of huge sponge-like cell.

Why do they need such immense sizes for a 250 KW fuel cell?

Hydrogen fuel cells can be this smaller too:

I also just found out about molten chloride fuel cells, which use things like table salt (sodium chloride). Dunno what is the difference between these two in the matter of performance and efficiency, but I suppose there are many, many types of molten fuel cells.

Off-topic:

So, I just scrolling on youtube shorts (definitely not procrastinating) and I saw this little video here:

The spheres are magnetic (can lift 9 kilograms), which is interesting, but anyway.

I was thinking: could you make a "disactivation" coilgun with this?

I've made a rough estimative with that by inputing the weight of a possible projectile and the thrust required to accelerate it towards mach 4 in 0.001 seconds (the length of a 60cm barrel), and basically, it would need a thrust of 6000kg.

Well, I don't necessarily need to start with 6 tons of electromagnetic force, but you you get what I mean.

Basically, I thought on lining up those holding electromagnets (since they are just like permanent magnets) launch the electromagnetic projectile in its direction and once it gets more or less in the middle of each section, the electromagnet is disactivated and its remaining electricity is pumped into the next electromagnet until the thing is launched.

A 100kg holding electromagnet only uses 14 watts, but I do know that I would probably need to increase its output power severely, since the "trick" to these electromagnets is that they complete the magnetic field using the ferromagnetic target (the object it attaches itself to).

However, the idea would be to put the nort and south poles of electromagnets in a "C" along the tube of the gun.

Kinda like this:

Insert a tube in the air gap and it is pretty much what I thought.
I just couldn't find any kind of coilgun like that, the closest I found was a "quench coilgun" that instead of disactivating the coils, it quenches/heats up superconductors in a sequence.

I just said that, and it seems this is a "reluctance coilgun", which would be better with aircore solenoids instead of iron core electromagnets because the core has a limit on the amount of magnetic flux it can allow to pass through itself.

Source: https://4hv.org/e107_plugins/forum/forum_viewtopic.php?id=83108

There is a lot of interesting concepts would there, for example:

Source: https://www.semanticscholar.org/paper/Design-and-Analysis-of-a-Novel-Three-Coil-Launcher-Guangcheng-Wang/a123efb779e8911f5a824420d3d09626ba456833

Wait a minute, wouldn't this be actually great for pilebunkers?

The magnetic rod wouldn't scape the solenoid's insane electromagnetic field and would go back and forth just like the first video of the magnetic sphere.

Pilepunkers are always depicted as a combustion/detonation machine, but I don't think anything would be able to survive the detonation and be cheap enough for its use.

... But if that is the case, then why not just use it to push a projectile really fricking fast instead of launch it with a coil gun?

There was actually a silenced projectile/gun like that, but with combustion instead.

It is called a "captive piston cartridge".

Not Off-topic - Revisiting Actuators:

Now that I ended up procrastinating and researching about railguns, I found out that the lower the speed of the railgun, the higher its efficiency.

So, a 1000 m/s (Mach 2.9) railgun has efficiencies around 40% while a 3500 m/s (Mach 10) to 5000 m/s (Mach 14) has efficiencies around 30% to 20%.

So, this made me think: what if the speeds were actually 1.33 meters per second just like the mech needs?

If the efficiency raises up to 80% to 90% at these speeds, then I could make an actuator that is super light, effiicent, strong, cheap, simple and fast.

Even better than artificial muscles and electric motors.

Just now I found out that the maximum efficiency would be 50%, but I asked chatGPT to make the calculation on how efficient it would be for a railgun to push a 3000kg projectile at 2 m/s and it said it would be around 1% to 0.2%...

I went asking around to see if there is something like this, but people normally just scoffs at the question, just says it is idiot or plainly ignores it.

... Which is kinda frustrating... I just want to understand if it works or not... And I don't think I have the resources to test this out...

I just found a few articles about it, and they don't even mention the efficiency of the system...

Source: https://www.researchgate.net/publication/317596343_Large_Displacement_Bi-Directional_Out-of-Plane_Lorentz_Actuator_Array_for_Surface_Manipulation

Source: https://www.researchgate.net/publication/283643918_Design_and_Simulation_of_A_MEMS_Based_Horseshoe_Shaped_Low_Current_Lorentz_Deformable_Mirror_LCL-DM

Do I really need a railgun actuator tho?

The coilgun actuator could do the same work, an 1 ton solenoid holding magnet uses around 1 to 3 kilowatts of power and weighting 3kg to 5kg.

Of course, the holding solenoid isn't that powerful because it needs a ferromagnetic material to close its magnetic loop, but would a solenoid be able to pull up this much power by also using an electromagnetic inner rod/plunger?

... But the solenoid rod has less moving force the further it is from the center, so you would need it to be stronger X amount of times.

... No matter how much I feel I learned with this project, I always learn that I know nothing.

I'm in the right path? I'm making real progress? I actually checked every option properly?

I should've been in an engineering college or something like that... Or else I can't see this project being completed... 🤔

I just now found something similar to the railgun-coilgun hybrid, but for actuation porpuses.

And stopping to think about it, I don't think this is an "hybrid" like the templin institute said, but just a coilgun with a commutator...

Source: https://lifeboat.com/em/chapter.4.pdf

As you can imagine, the idea is pretty simple: make the sliding contact coilgun, but use it as an actuator instead.

Could this finally mean that I could have an efficient, simple, cheap, practical that outputs force proportional to the energy input?

You could also built it with flexible tubes/fibers in order to work just like a muscle, which would be a pain in the butt to maintain and verify for defects and wear. But at least you would have the first and only electric artificial muscle with efficiencies above 80%.

Well, the only problem would be the wear and friction of the commutator/sliding contact, which is also a source of inefficiencies and cost of maintenance on normal brushed motors.

MAYBE this time it will be easier to find the energy input and efficiency because both are coils/solenoids.

... But I think I'm looking at it in the incorrect manner... Should I make it brushless instead?

You see, the first idea I had for this was the linear brushless motor... And I discarded it because it would be too heavy and expensive.

Maybe it didn't work at first because I've made a brushless motor with a rotor (the moving part) with too many slots? Just like in the image above?

... And also because I couldn't possibly make an ESC controller with hundreds of amps and hundreds of volts.

... Which I wouldn't worry about while building the brushed linear motor.

Sorry for not calculating this thing right now.

For some reason I'm feeling indisposed...

But goddang it, it kinda a pain in the butt to convert joules to watts.

Supposedly, accordingly to kinect energy calculators, I woud need around 2,665 joules to move the 3000kg load at 1.33 m/s target. But the problem is that joules can't be directly converted to watts because watts is a matter of work over time.

So I can't just convert joules to watts and watts to volts and amps. It would be so much easier this way tho...

So, basically, I need to make coils on Blender and measuring their height, diameter, number of turns and thickness of wires in order to use a solenoid force calculator.
And even then it is not that easy, because the calculator probably only shows the force at the center of the solenoid, not on its outside.

... But I could just use a back iron plate to redirect the electromagnetic field...

I guess one way of looking at it would be thrust to move an object to certain speed.

If we use a speed calculator to move something at 1.33 m/s with a 30 cm distance, it would take 0.22556 seconds.

If we take an acceleration calculator, to move from 0 to 1.33 m/s would need an acceleration of 5.896 m/s².

If we take a thrust to acceleration calculator, to move a 3000kg mass to 1.33 m/s with an acceleration of 5.896 m/s², it would need a thrust of 17,688 newtons or 1,803.8 kg-force.

If we want to quadruple the speed (let's say, when jumping), you would need 7,215.2 kg-force.

Obviously, the transmission of power isn't perfect and it would require more energy, but at least I think it will be easier to find a result for said brushed coil actuator.

Also, let's remember that the reduction in the transfer of the lever limbs (aka, where the actuator is attached to the limbs in the body will work like a lever) will be 3:1, an increment of 3 times the speed and decrease of 3 times in its strength, reaching the speeds the human body reaches.
From stationary to even 12 meters per second or 43 km/h while carrying 1 ton of weight.

A kind soul told me that I should start calculating the inductance first and then calculate how the solenoid should be.

Well, I roughly calculated the inductance, magnetic field strength etc. And I still can't tell how strong the electromagnet would be, neither if this electromagnet would be strong enough to lift 3 to 10 tons.

I'm mcfuckin losing it my guy, I can't find a way of predicting the force output of the coils no matter how much I look into it.

Also, I think the previous estimative that the actuators would need to accelerate masses to 1,33 m/s is incorrect because I didn't take into consideration the gravity of earth, which is 9,8 m/s².
So, essentially I need to counter that acceleration of gravity and then add the 1,33 m/s to the mix.

No matter what, the results are never consistent.

I ask to chatgpt and it says it will have less than a single newton of force, I go to solenoid force calculators and they say my coil would have 10 million newtons of force.

Here is the question that I copy paste for every ChatGPT:

I need an electromagnet solenoid coil to pull up an outer electromagnetic with an X amount of force.
How I can calculate its force?
The outer diameter of the inner coil is 190mm, the inner diameter is 110mm, the space between the turns is 1mm, the height is 82mm, number of turns is 2, the length of the wire itself is 1193.8mm, the ampearge is 1000 amps, the voltage 200 volts, it has a distance of 1mm between this coil and the outer coil and is at 10mm above the inner electromagnet.
The outer coil has a wire thickness of 40mm, a spacing of 1mm between the turns, 2 turns and an inner diameter of 194mm, so an outer diameter of 274mm, the amperage is 1000 amps, the voltage is 200 volts, the length of the wire itself is 1721.6mm

Mistra-medium from PoeGPT said the following:

Sure, here are the calculations for the force exerted by each solenoid coil with 400 V and 500 A:
For the inner solenoid coil:
The cross-sectional area of the inner solenoid is:
A = π * (190/2)^2 - π * (110/2)^2 = 14,094 square millimeters

The force exerted by the inner solenoid can be calculated using the formula:
F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 500^2 * 14,094) / (2 * 1^2)
F = 88,220 Newtons

For the outer solenoid coil:
The cross-sectional area of the outer solenoid is:
A = π * (274/2)^2 - π * (194/2)^2 = 39,377 square millimeters

The force exerted by the outer solenoid can be calculated using the same formula as above:
F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 500^2 * 39,377) / (2 * 11^2)
F = 37,364 Newtons

Now, let's try the same thing again:

If you increase the voltage to 500 volts and the amperage to 400 amps in both coils with the 40mm wire thickness, the force exerted by the solenoids will increase significantly due to the increased current flowing through the coils.

The force exerted by an electromagnetic solenoid is proportional to the square of the current, so doubling the current will result in a four-fold increase in the force. Using the same calculation as before, the force exerted by the inner solenoid coil at 500 volts and 400 amps would be:
F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 400^2 * 14,094) / (2 * 1^2)
F = 352,880 Newtons

Similarly, the force exerted by the outer solenoid coil at 500 volts and 400 amps would be: F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 400^2 * 39,377) / (2 * 11^2)
F = 149,456 Newtons

Well, this value is unnusually high, so I asked it to recalculate with an wire with the proper diameter for 400 amps, but it got way less force, so I asked why that was the case.

And the answer from the Mistra-medium was:

I apologize for the confusion in my previous responses. You are correct that the forces I calculated earlier for the 40mm thick coils were much higher than the forces I calculated in my latest response for the 14mm thick coils.

The force exerted by an electromagnetic solenoid coil is proportional to the current flowing through the coil, the number of turns in the coil, and the cross-sectional area of the coil. Since the current and number of turns are the same in both cases, the difference in force can be attributed to the difference in cross-sectional area.
For the 40mm thick coils, the cross-sectional area of the inner coil was approximately 14,094 square millimeters, while the cross-sectional area of the outer coil was approximately 39,377 square millimeters. In contrast, for the 14mm thick coils, the cross-sectional area of the inner coil is approximately 1,848 square millimeters, while the cross-sectional area of the outer coil is also approximately 1,848 square millimeters.

Therefore, it is not surprising that the forces exerted by the 14mm thick coils are much lower than the forces exerted by the 40mm thick coils. In general, larger coils with more turns and a larger cross-sectional area will be able to produce a stronger magnetic field and exert a greater force.
I hope this clarifies any confusion. Please let me know if you have any further questions or concerns.

No, seriously, this doesn't make any sense. I asked around and people told me I'm stupid.

I mean, they aren't wrong, but I guess it is useful tho...

Dunno if this is useful at all, but I was only expecting an approximation, not an absolute answer. But I guess it is better than start with absolutely nothing.

Also, like I said before: I can't buy anything for the next 7 months because that is how much I divided the cintiq style table.

So I don't know if I will be able to continue this project until next year.
In fact, I don't even know how to start.

Just now I decided to calculate the weight.

The weight of a single aluminium coil actuator in the molds I just talked about would weight around 28kg.
840kg in total for all 30 actuators.

The 14mm thick wire would weight around 5kg per actuator, 150kg in total.

Maybe sticking with the HASEL artificial muscles is a better idea?

Of course, that is the weight of all actuators that can output 10 tons to 50 tons (accordingly to the chatbots), I could make the upper limbs lighter (and weaker).

It took me almost an entire month just to figure this idea wouldn't work...🥲

(assuming ChatGPT is correct)

Project Log 83: Screw it, let's freaking do it.⁴

06/10/2024 at 12:56 • 2 comments

Monday, 10/06/2024, 09:44

(is Hackaday.io going down to all of you or just me? Some times I need to wait an entire day for the website to be accessible)

Well, I feel like it is a bit too soon to be worrying about design, and specially since I literally didn't start working on it at all even though I name the project logs exactly to do that. :|

But here we go again with my shenanigans...

Design of the Artificial muscles:

Materials for dielectric elastomers:

Well, since I'm intending on making dielectric elastomer fibers with 1mm of thickness, I can't really just make it whatever way I want and leave at it.

I could simply connect a single fiber and be done, since very high voltages and very low amperages can travel kilometers in materials without any loss, but if any fiber is damaged, well, you could have the entire thing stop working. Of course, I still could make the fibers slightly bigger and just connect new muscles whenever some fiber is damaged, and I do intend on doing that if this idea shows itself to not be viable.

(I want to make it as small as possible because I'm afraid that the contraction ratio of the muscle will force me to change the proportions, right now the idea is that the muscle is attached to 1/3 of the limbs length, if I'm reguired to increase it, then it would make the muscles even heavier)

I need polymers that are soluale in a material, but not in other. At least for the outside layer.

Polyvinyl alcohol is soluable in water and alcohol, but not in acetone or gasoline.

Polystyrene (styrofoam) is soluable in acetone and gasoline, but not in alcohol or water. (Funnily enough, polystyrene is even cheaper than PVA)

Poly(methyl methacrylate) (PMMA) is soluable in acetone, but not in alcohol, water or gasoline.

Polyvinyl chloride (PVC) is soluable in acetone, but not in alcohol, water or gasoline.

So, if my brain isn't being stupid: for half of the outer layer of PVC/PMMA that dissolve in acetone and for another half, I would need a material that dissolves in gasoline, but not in acetone, alcohol or water. I could only find a few forum questions saying that PET and LDPE can be damaged by gasoline over time, but not something that can actually dissolve.

I found out that if I mix PVA with dielectric silicone grease, it becomes resistant to water, but also that there are waterproof PVA glues in the market. So I "just" need to mix it with PVA and make it hydrophobic.

So, the design of the actuator:

Outer layer of negative electrode side = Dielectric Soluble Polymer 1 + low friction material + other additvies if required.

Negative Compliant Electrode = fumed silica powder + graphene + polymer.

Dielectric Elastomer Layer = Dielectric Elastomer Polymer + titanium dioxide + other additives if required.

Positive Compliant Electrode = fumed silica powder + graphene + polymer.

Outer layer of positive electrode side = Dielectric soluble Polymer 2 + low friction material + other additvies if required.

I don't know what polymer to use on the electrodes yet, I was thinking on just using PVA. I also don't know which low friction material I should use for the outer layers, I was thinking that they should have low friction for better actuation of the artificial muscles...

So the idea is to:

Make a 1 mm (less or more) fiber with this structure.
when deciding to attach to a limb, over the attachment places of the skeleton/limb with dielectric material.
Roll the dielectric elastomers up in a loop.
Hold them in place with a really tight cable.
Making the "tendons" by going with another rope through the loops.
Use one solvent in one tip of the muscles and the other solvent in the other tip.
Cover the tips in a conductive polymer (probably PVA) with the negative and positive electrodes.
Connect everything to the electronic system.
Then wrap everything in another layer of dielectric material to avoid the electrical current to arc.
Done.
Optional: I also thought on surrounding the muscles with a plastic bag and fill it up with a dielectric liquid, grease or gel for extra safety if any fiber muscle comes to be damaged.

"Just" that, god, I whish there was an electric artificial muscle that didn't need a positive and negative end...

You could just have a dielectric elastomer in which you just insert the electricity, but doesn't need the other electrode to be connected to anything, the difference in energy potential alone would make the dielectric elastomer actuate. However, I do think that the difference in voltage of the powersource is bigger than the difference in voltage of the material alone. But I don't know who to ask.

For some reason I can't find the goddang dielectric values of polyvinyl alcohol, it is said it is high, but never how much.

And I'm not talking about dielectric constant, but dielectric strength and breakdown voltage.

Well, after 2 hours I actually found it, in this paper it says that:

"The dielectric strength of polyvinyl alcohol (PVA) is potentially very high i.e >1000 kV/mm. "

Ok... But I think that using cheap off-the-shelf PVA glue with waterproof PVA glue mix won't give such insane results, I guess that I will literally need to buy the equipment and test it to failure...

Now I need to find out how to make a power source that reaches high values of Kilovolts and high values of Hertz...

Actually, I found power supplies like that, but they cost thousands of bucks, so I will need to build everything homemade, which I'm not capable right now since I bought a new table and a new drawing tablet...

Just now GPT actually answered me other materials that actually are soluable in different solvents than PVA and Polystyrene.

Like Polyoxymethylene (POM) or Polyacetal that aren't soluable in acetone nor water or alcohol, but it is soluable in Benzyl Alcohol, but although I couldn't find how it affects PVA and Polystyrene, it probably dissolves one of them.

In any case, I will keep trying to find new options.

On a side note, the dielectric constant is the value of how much charge a given material can store, so the higher the dielectric constant, the higher the energy density of the material.

HOWEVER, this can also decreases its breakdown voltage (depending on the material), so you can't just take a material that has insane high dielectric breakdown voltage if it can't store that much charge...

So, making a list:

I will make it later, right now I'm reading manga, lol

The manga is a generic tutor isekai crap, it is not that big of a deal, I just like to read something silly and dumb to forget a little about our burning world full of horros beyond our comprehension.

Now I finished it:

Name (for some reason this part of the table is squished):	Dissolves in:	Insoluble in (for some reason this part of the table is squished):	Dielectric Breakdown Voltage:	Dielectric Constant (it can change severely based on hertz):	Tensile strength:
Polyvinyl Alcohol	Water, Ethanol	Acetone	45 (source), 420 (source) to 1000 (source) KV/mm	1.01	8-40 MPa depending on the source.
Polystyrene	Acetone, Gasoline	Water, Ethanol	24, 25, 400–600 KV/mm	2.6	5-50 MPa
Polyoxymethylene (POM) or Polyacetal	Benzyl Alcohol	Water, Ethanol, Acetone	19.5 to 50 KV/mm	3.02	69 MPa
Titanium dioxide	Not required	Not required	12-270 KV/mm (Depending on the source 1, 2)	85-173	Not required
Aluminium Oxide/alumina	not required	not required	14 KV/mm (source)	8.6-10	not required
FiberGlass	Not required	not required	2,000 KV/mm	6.2	not required
Silicone Rubber	Acetone, Mineral spirits, tuolene, white vinegar, Isopropyl Alcohol, Methyl Ethyl Ketone (MEK)	Water, Ethanol	39.5 KV/mm	3	3-5 MPa
Dielectric Silicone Grease	Same ones	Same ones	0.350-1.5 KV/mm	2.6-2.9	Not required
Polyurethane rubber	Acetone, toluene, xylene or MEK	Water, Ethanol	70-90 KV/mm	13.5	3-5 MPa
Polyethylene (HDPE/LDPE etc)	Tuolene, Xylene	Water, Ethanol, Acetone	50, 500–700, 18 KV/mm	2.2	20-45 MPa
Polypropylene	Xylene, Tetralin and Decalin	Water, Ethanol, Acetone	30-40 KV/mm	2.1	30-45 MPa
ABS	Ester, Acetone, Chloroform	Water, Ethanol	20-25 KV/mm	20-25	30-60 MPa
Nylon	Phenols, calcium chloride-saturated methanol solution and concentrated formic acid	Water, Ethanol, Acetone	25 KV/mm	3.5	85 MPa
Polycarbonate	Ethylene chloride, chloroform, tetrachloroethane, m-cresol, and pyridine	Water, ethanol, acetone	15-67 KV/mm	2.9	39-120 MPa
Teflon	Virtually none	Virtually all	60 KV/mm	2.05	41 MPa
Lead zirconate titanate	not required	not required	25 KV/mm	500-6000	Not required
Talc Powder	not required	not required	200-500 KV/mm	3-15	not required
Cellulose Acetate	acetone, spirits and ethanol.	water	11-15 KV/mm	3.6	26-33 MPa
Polyvinyl Acetate	acetone, spirits and ethanol.	water	(not found)	3-15	3-10 MPa

Now that I finally finished the list I end up finding this PDF archive that pretty much lists all of the polymers out there... There is also this textbook and this one.

There is also this list of the highest dielectric constant (aka permitivity) materials.

Funnily enough, I could find Lead-Zirconate-Titanate piezoelectric devices in a reasonable price on aliexpress. Even if I bought them and broke them back to powder, I don't know how much of their original properties would be left...

I also thought on adding diamond powder to the composite of the dielectric layer, since it has such high breakdown voltage. But I don't know if the diamond powders out there are really diamond or just zirconia.

Well then... I've made this huge list, now what?

Hum...

First:

maybe the 1mm thick fibers aren't a realistic goal for this project, maybe I should aim for a dielectric elastomer layer with 1mm of thickness.

Second:

I need to find a way of making the restrained DEA with the mesh, I mean, I don't know how to mass-produce at home these braided mesh for a 1mm of thickness dielectric elastomer actuator.

I also don't know if other shapes could work, for example, the McKibben muscle works in a similar way with the braided mesh, but they also use linear meshes. If the linear meshes are viable, then would them work in the fiber 3D printed DEA?

Restricted DEA with a braided mesh:

McKibben muscle with a similar mesh:

McKibben muscle with linear mesh:

Would any of these work with the fibrous 3d printed DEA?

If this was to work, then it woud way easier to make the actuator in a mass-produced manner, and it would probably be possible to make it smaller than 1mm.

Although the dissolving the opposite electrodes idea will be in the trashcan after this... Or maybe not, the image shows that you could print the fibers without one of the electrodes, so every X meters I would go switching which electrode can be accessed by simply not printing one of the four parts (outer dielectric layer > outer electrode > Inner dielectric layer > inner electrode)

Also, I was considering making the electrodes liquid (or even a gel), so it would be easier to simply remove the extra fluid of one of the concentric tubes. Some even use room temperature liquid metals like galinstan.

Source: https://www.mdpi.com/2073-4360/13/24/4310

The use of liquid electrodes also doesn't solve the problem that I would need to connect thousands of fibers, I really need to solve this problem, even if it where the conventional sandwich of dielectric elastomer layers, it would still be a problem to wire thousands of fibers.

Just now I remembered that there is the option of a spiral fiber dielectric elastomer actuator:

Source: https://www.researchgate.net/publication/228824825_Theoretical_description_and_fabrication_of_a_new_dielectric_elastomer_actuator_showing_linear_contractions

Maybe with this design I could turn the inner hole a continuous connector and the outer tube also a continuous connector, let's say, you can only access the negative electrode from the outside and the positive through the inner side. Although... I still don't know how well this would work... I can still use the idea of covering the different electrodes with different plastics that dissolve in different solvents.

There is also this design:

Source: https://www.researchgate.net/publication/337164497_3D_Printing_of_Interdigitated_Dielectric_Elastomer_Actuators

I know that I simply never stop adding more and more designs that could pottentially work, but I do think this is it. This one allows the fibers to be actually around 1mm to 2mm thick while also allowing the separation between the electrodes to be also 1mm without making the electrodes too thick.

My only gripe with this design is that the center contracts more than the borders, so how exactly would it reduce its length if the entire border of the actuator is connected to something?

The only reference I have are these two videos of dielectric elastomer actuators:

The first is just like the 3 dimensional version of this planar electrode, while the second doesn’t seem to have the same issue because it doesn’t seem to have the outside electrodes.

The only problem remaining is that I kinda want to use PVA because of its price, but there isn't anything that doesn't dissolves in something PVA does… I guess that I could simply mix it with waterproof PVAc (wood glue) to make the core water-proof but not the electrode protection, or even hydrophobic materials like fumed silica.

So, a drawing of how I intend on doing it:

Obviously, this will be a continiously printed dielectric elastomer actuator.

Also, I didn't talk about it because I didn't want to bloat the project log more than it already is, but taking into consideration the thickness of everything, a lot of these options for fiber DEA's ended up being half a centimeter of thickness (or even wider) when you stop to think its dimensions. Besides, I do think this version would also be easier to print without some crazy DIY setup. I could even use a rolling printer for this.

Oh yeah, I forgot to write about the efficiency of dielectric elastomer actuators. They work through the Maxwell stress, so a lot of energy is wasted just to overcome the resistance of the material for bending. So, the efficiency is around 18%-20% and maximum 60% while recycling the energy that comes out of the muscle, they are a kind of capacitor anyway.

Okay guys, this is the last time, I swear.

I'm not satisfied with the hypothetical performance of this dielectric elastomer, I'm not very confident on its actuation strain and efficiency. And after some consideration, I do believe that the best material to continue with this endeavour is the HASEL actuator. They don't neeed an elastomeric material, only a flexible one.

They can also be tuned to have higher contraction ratios as shown in the video.

I also tried to find a dielectric elastomer and HASEL hybrid only for the sake of not throwing the design away, but I couldn't find any.

And finally, I will need to figure out how to extrude this thing. I was thinking of even using a 3D printer… Initially I was against the idea because I was thinking of making everything as thin as possible, since this is not the objective anymore, dimensions of millimeters are really within any 3D printer. After all, 3D printers have a precision of 0.2mm or even smaller. And for that I would need multiple nozzles and a multi-material screw extruder for mixing all the materials together.

And at this point, I’m not even sure if I will use PVA glue for the plastic or HDPE/UHMWPE + PE wax for the core materials…

Third:

Now I "just" need to start modelling the skeleton and "simply" making the muscles.

This is that moment that deep down in my lizard brain that makes me think:

"This thing might kill me"

We are taking about kilovolts that could easily make my heart stop.

Although the thickness of the materials will differ, and thus, the input voltage may be lower, we are still talking about inserting 81 Kilowatts of power in the shape of high voltage low amperage.

And on top of that, it will require the same mechanical brakes as the other artificial muscles, so I'm starting to ask myself it is worth the trouble...

Shouldn't I instead work with the thermal artificial muscles...?

Well, this is me from the future, and I finally went to check the price of mechanical/electromagnetic brakes and winches with the lifting capacity closer to the intended input force (3000kg), and guess what?

It is too expensive and heavy. :|

With the exception being the manual winch brakes, which would need to be modified for higher load and also for the insertion of a encoder:

Mech design:

I want to make some of the parts of the mech biomimetic, I was thinking on making artificial cartillage (gels attached to the joints of the skeleton), artificial ligments (cables/ropes attached to the skeleton) and tendons (ropes covered in pva).

I'm just not that confident on my skills, neither in how long/strong will these parts actually hold on. I say this because some parts of the human body can reach 1 GPa of tensile strength. That is close to carbon fiber, now imagine an elefant or a horse...

You know what? I will "study" (look at videos) the anatomy of elefants, horses, rhinos, hippos and all sort of heavy animals in order to take inspiration/copy their structure for the mech. By the way, elefants can weight from 2700kg to 6000kg depending on the race, horses can weight from 150kg to 1500kg depending on the race, hippos range from 1300kg to 1800kg and rhinos 2500kg to 3200kg. These values are the average, the elefants can even get up to 10 tons.

In both cases, what concerns me is the relaxation of the artificial tendons, ligments and muscles.

This video is about a reduction pulley that uses ropes, and after a while, the ropes start creep. The guy was forced to use Dyneema for it, which has the lowest extension in the market, but it is also very expensive. However, his actuator is a precision actuator, not a biomimetic artificial tendon made in the trash (like mine), so I don't know how much it would affect my project.

Accordingly to this document, irreverssible rope creep can happen after a few years. Well, it sounds good to me, gears and bearings have the same issue of degradation over time. https://www.samsonrope.com/docs/default-source/technical-bulletins/tb_understanding-creep_mar2012_web.pdf?sfvrsn=1e71fc4e_2

Bruh, the idea that every couple of years I will need to make a "surgery" in a mech to fix its arthritis, arthrosis, tendinopathy and strains.

Articles that I think are interesting for biomimetic human robot:

"Bone has yield strength of 51–66 MPa in tension and 106–131 MPa in compression when tested along its transverse axis. The Young's modulus of cortical bone is 17–20 GPa along the longitudinal axis and 6–13 GPa along the transverse axis (Toma et al., 1997)." https://www.researchgate.net/publication/336821961_Rapid_prototyping_technology_for_bone_regeneration

"Tensile strength of the extensor tendons averaged 13,392 psi (88 MPa) while that of the flexor tendons was less, with an average of 10,944 psi. These results indicate that, of the tendons tested, the extensors are about 20 per cent stronger than the flexors." https://www.sciencedirect.com/science/article/abs/pii/0021929068900389

"The tensile strength of cartilage from the deep zone did not show an increase in the early years but decreased continuously with age. The tensile stiffness of the superficial layer at stresses of 5 MN/m2 (5 MPa) and 10 MN/m2 (10 MPa) increased to maximum values in the third decade and thereafter decreased with increasing age." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1001032/

" Ultimate tensile strengths for tendons and ligaments range from 50 to 150 MPa (for comparison, recall that the tensile strength of bone is about 150 MPa)." https://musculoskeletalkey.com/mechanical-properties-of-ligament-and-tendon/

"The 'overall' strain in the ligament was calculated from the outermost pairs of markers along the ligament length. The average tensile strength, the 'overall' tensile modulus and the 'overall' strain of the ALL at failure were 27.4 MPa (S.D. 5.9), 759 MPa (S.D. 336) and 4.95% (S.D. 1.51)" https://pubmed.ncbi.nlm.nih.gov/1400518/

A rubber pad for hydraulic jack with a diameter of 115mm and thickness of 35mm can withstand 2500kg, and accordingly to compressive strength calculator, the force in MPa would be around 2.3 MPa. So a compressive strength of 8 MPa would be 3.47 times that value (assuming the same diameter of 11.5cm), so: 8695.6kg. Obviously, I do intend on using other materials for the composite and increasing its strength, like starch, cellulose fibers, borax and even sodium hydroxide with fumed/fused silica powder. The addition of 1:1:0.1 of PVA, starch and cellulose alone can double or even triple its tensile strength.

I said "biomimetic", but boy, do I say BOY, the idea of simply going full anatomical copy of the human body is extremely tempting.

The reason why this is a bad idea:

Human body has 206 bones
More than 650 skeletal muscles (muscles attached to the skeleton)
900 ligaments
4,000 tendons.

So, I was wondering which should be the height of the mech. Well, I actually found proportional human height calculator:

https://hpc.anatomy4sculptors.com/

And as such, you could insert the height of a person in a determined position in order to check how tall the mech should be in order to fit the pilot inside of it.

For example, if the pilot has 185 cm of height (1.85 meters), its thigh/femur would have around 46cm long, and if you assume this person is in a sitting position, then you just need to reduce the length of the thigh by the total length 185-46 = 139cm. If you insert this length in one of the parts, the other measurements will be in proportion to that. For example, if you add this length of 139cm to the square where it says "from shoulder line to navel", the total height including head would be around 6,6 meters tall (5.7 meters without the head).

By the way, if you assume the leg of the Mech in the art of this project has around 1,9 meters of height, the total height of the mech would be around 7,5 meters tall.

Well, I settled for the height of this 185cm tall person in a crouch position to be a little more than 90cm, so the entire height including the head of this mech would be around 3,8 meters tall (without the head).

Of course, you could change this whatever way you want to, but it would stil give an idea on how big the mech should be in order to fit the pilot and on top of that, all of the equipment. And I do think this is too tall since the floor to the ceiling of my room is just 2,5-2,6 meters tall, and I don't see the reason for a mech that needs to be crouched to fit in a room.

By the way, using the square cube law and assuming that a 1,80 meter tall human weights around 80kg to 100kg, a 3,6-3,8 meter tall human would weight around 640kg to 800kg.

So you can have an idea on how much weight this mech would weight in this scenario.

Obviously, I don't know yet what are the exact dimensions of the pseudo-bones/endoskeleton of the mech, since they are meant to be biomimetic and not a 1:1 scale.

Besides, the human skeleton is capable of enduring 30 times its own weight, so i would need to make it around 10 times thicker/stronger in order to survive the thousands of kilograms I intend on making it lift.

It just occurred to me that I could just make cylinders actuated by the HASEL/DEA actuators instead of a biomimetic mess that would be harder to build and maintain…

Source: https://www.researchgate.net/figure/The-prismatic-soft-actuator-The-Pneumatic-Artificial-Muscles-PAMs-of-the-prismatic_fig2_366616100

That is a way of doing that alright. Obviously I’m not gonna do this way, but you get the ide

Also, links relevant for heavy animal anatomy:

Off-topic:

While I was reading manga, it got me wondering:

Wouldn't it be cool if there was a mathematical system and/or a programming system based on magical circles and the like?

I'd say that they would need to be intuitive, dynamic and work with the already stablished system in order to work properly...

You may think it too much of a difficult task, but just look how Japanese people makes multiplication:

Don't tell me this doesn't look like a magic circle, lol.

Also, while image searching, I just found out that there is a mathematical "magic circle" made by a chinese named Yang Hui.

I do wonder what else strange mathematical systems one could find while digging around history... huh

Adding this here because I'm afraid of the project log deleting some things:

I just found out that there are graphene fibers that are made either using graphene oxide or dissolving them into polyvinyl alcohol and water while extruding.

I don't know how exactly they are done, but I do think the PVA and electrospinning (that method of making nanofibers) would be the easier method and the simplest.

Source: https://www.sciencedirect.com/science/article/pii/S0950061820316524

Plus, the continuous method of making flash graphene is by either using a plasma torch with neutral gases such as argon or helium or simply making an automatically self-charging flash tube.

Source: https://www.researchgate.net/publication/355576693_Large-Scale_Syntheses_of_2-D_Materials_Flash_Joule_Heating_and_Other_Methods

Source: https://www.nature.com/articles/s41467-024-47603-y

Project Log 82: Screw it, let's freaking do it.³
06/05/2024 at 11:33 • 6 comments
Wednesday, 05/06/2024, 07:36

Well, the previous project log had so much text that it started deleting new text.

I really don't want to go 2812838218 project logs into the part I actually start building something...

I also bought a new table and one of those drawing tablets with screen on it, because, if you don't know, I like to draw things (even though I'm bad at it [hey, I make a mech project, even though I'm bad at it too]), so I won't be able to buy anything for the project for the next... What? 6 to 10 months. lol

I do hope I can make some extra money with my drawings tho... Hopefully...

Well, Anyway, starting from where we left:

Wattage consumption:

(81 kilowatts is the energy required to move 1 ton of weight at the speed of the human body)
- Arm + Shoulder + Torso + Leg of one side of the mech.
- 81 + ((81x3)x6) + ((81x3x3)x6) + ((81x3x3x3)x6) = 19,035 kilowatts = 25,380 horsepower.
- 81 + ((81x2)x6) + ((81x2x2)x6) + ((81x2x2x2)x6) = 6,885 kilowatts = 9,180 horsepower.
- 81 + ((81x1.5)x6) + ((81x1.5x1.5)x6) + ((81x1.5x1.5x1.5)x6) = 3,543.75 kilowatts = 4,725 horsepower.
- 81 + ((81x1.2)x6) + ((81x1.2x1.2)x6) + ((81x1.2x1.2x1.2)x6) = 2,203.848 kilowatts = 2,938.464 horsepower.
- 81 + ((81x1.1)x6) + ((81x1.1x1.1)x6) + ((81x1.1x1.1x1.1)x6) = 1,769.526 kilowatts = 2359.368 horsepower.
Assuming that there is no biceps/arm actuator, but a shoulder-arm stewart platform:
- (81x6) + ((81x3)x6) + ((81x3x3)x6) = 6,318 kilowatts = 8,424 horsepower.
- (81x6) + ((81x2)x6) + ((81x2x2)x6) = 3,402 kilowatts = 4,536 horsepower.
- (81x6) + ((81x1.5)x6) + ((81x1.5x1.5)x6) = 2,308.5 kilowatts = 3,078 horsepower.
- (81x6) + ((81x1.2)x6) + ((81x1.2x1.2)x6) = 1,769.04 kilowatts = 2,358.72 horsepower.
Well, let's try a non-exponential aproach then:
- 81 + ((81x2)x6) + ((81x3)x6) + ((81x4)x6) = 4,455 kilowatts = 5940 horsepower
- (81x6) + ((81x2)x6) + ((81x3)x6) = 2,916 kilowatts = 3888 horsepower
- 81 + ((81x1.5)x6) + ((81x2)x6) + ((81x2.5)x6) = 2997 Kilowatts = 3996 horsepower
Okay, this is just getting stupid.

Needless to say, screw actuator, hydraulics or pneumatics, I don't think it will be possible to continue with this insane amount of power required.

I guess this is another wall that I've stumbled upon and I need time to think on how to preoceed...

The first obvious thing that probably anyone with a lizard brain bigger than mine notice: I'm assuming that all the actuators in the stewart platform are using power, which would not occur.

And being honest, I don't know how to properly calculate that...

It is always relevant to remember myself that all of this problem comes from the fact that I'm trying to make a humanoid mech, a walker mech wouldn't need to worry about lifting weight, in fact, this project would've already been in actual construction if it wasn't for this detail... (I think).

Land Walker

Types of mechs that are viable/practical or not:

Screw Actuator Mech/Electric Mech: ❌

I still need to calculate those, but even though it would supposedly be lighter and practical with a direct electric motor driver, unfortunately it is not as simple.

As you could see, it requires 81,000 watts (100 horsepower) to move the limbs with a force of 1000kg at a speed of 4 meters per second, and even though I'm inputting 3000kg at 1.33 meters per second, it is the same amount of energy, but transformed.

And since the electric motor would be that 80 kilowatt Reb 90 for every limb, which weights around 30kg and probably costs hundreds of dollars if you're not in the mood to build it from scratch. aI don't think this is viable... For the mech.

If you are making an exoskeleton, then this value wouldn't be that high (8 kilowatts/10 horsepower), but it would still require considerable planning.

Hydraulic Mech: ❌

I can say with some certainty that taking this fact into consideration, hydraulics are out of the question for this specific task.

It doesn't matter if you are applying a few grams of force or a few tons, they will require thousands of liters of hydraulic fluids being pumped in order to actuate.

Hydrolysis Pneumatic Mech: ❓

If you don't remember, the idea is to separate hydrogen and oxygen from water, you would need 1 liter of water to generate 1857 liters of hydrogen+oxygen.

(I forgot to link the article that gave the idea)

Source: https://www.semanticscholar.org/paper/Soft-Polymer-Electrolyte-Fuel-Cell-Tube-Realizing-Nabae-Kodaira/e23633c26983e613c647139e917760feb9b52bb6

Based on the weight of the hydraulic fluid, I can take the volume of the liquid, more or less 400 to 500 liters and multiply by the pressure I intend on working with, which is 6 bar/atm, so, 500 x 6 = 3000 liters in total (since gases are compressible, unlike hydraulics).
So, 3000 liters for the mech to contract all muscles, 1500 if half is actuated, but I don't know how many liters will be used per minute, or even per hour.
We are talking about using 1500 liters of gases for a single contraction, after all, the amount required to keep the mech moving is just a guess, but it woul require a lot.

This would still require thousands of liters of air being pumped, but since you can control the output force, then it is one less source of energy losses.
- However, hydrolysis is 60% to 70% efficient.
- And I can't find a specific number, but it is said that pneumatic systems are 2% to 20% efficient, this is due to leaks, poorly sized valves and pipes and so on.
  Even without a pump, you would need those.
- But if you count only the actuator, it can be as high as 80% to 90%.
- You would need compressed gas tanks, made from scratch with plastic (like everything else) or bought.
- You would need mechanical brakes for position control, also more weight and complexity.
- You can recycle the hydrogen and oxygen with a fuel cell after they are used by the pneumatic system, like a turbocompressor recycling the the exhaust gases of a combustion engine.
- Limited pressure (6 bars), so bigger muscles, so big they might start weighting significantly
- hydrogen is combustable and so light/small it can pass through solid material, but HDPE and/or UHMWPE are polymers used in liners for hydrogen storage to avoid that, so I can assume it would be somewhat safe.
This one has a lot of pros and cons, and overall.

I will try and search for a material that can be separated into more inert gases for safety.

... And I can't find one at all...

I know that there is hydrogen peroxide and you could decompose it into water vapour and oxygen, but the process isn't reversible like hydrolysis...

Evaporative Pneumatic Mech: ❌

Esteban kidnly suggested me using a refrigerant called "Trichlorofluoromethane R-11" (what a mouthfull), it is non-flamable and it evaporates at 24ºC. You could just use any other refrigerant.

So it has all the pros of the hydrolysis pneumatic mech, but without the possibility of burning me alive.

But it still has some cons related to pneumatics:
- You would need an onboard refrigerator, and if it fails, you would really need safety valves, because all of it would turn into vapor.
- And since it is a evaporative refrigerant, it would need a really big heat exchanger and/or a electric heater, or else all the tubing would freeze and crack (leading to leaks).
- I'm still trying to find more information on how to handle this one specific refrigerant, but its liquid form depends on its pressure and temperature. Which for some reason, googles doesn't show me which is.
  Accordingly to this graph, at 6 bar of pressure it should liquid, and it would evaporate at around 71ºC.
  But wait, doesn't that mean that the gas in the muscles would be at liquid state since they are also at 6 bars of pressure?
- I can't find a specific number, but it is said that pneumatic systems are 2% to 20% efficient, this is due to leaks, poorly sized valves and pipes and so on. Even without a pump, you would need those.
- But if you count only the actuator, it can be as high as 80% to 90%.
- You would still need compressed gas tanks, but it wouldn't be much of a problem.
- You would need mechanical brakes for position control, also more weight and complexity.
- This time, the pressure wouldn't really be a limiter, but working with lower pneumatic pressures is still more efficient and practical.
Being honest, now I'm divided between dielectric elastomers and evaporative pneumatics...

Actually I noticed a relevant characteristic of it that may turn it non-viable: the compressor.

Assuming that you let some of the refrigerant liquid evaporate and pressurize, what will happen when you take it out of the muscle?
It will continue to be in the gaseous form, forcing you to compress around 1500 liters of refrigerant gas as fast as possible before it saturates the gas tanks.

BUT I don't know if it would be that simple, you could use the evaporation intake of the refrigerant to cryogenicaly cool the exhaust refrigerant gas.
On top of it, you could allow the exhaust gases to accumulate until they also reach 6 bars of pressure and let the compressor to work at somewhat minimum efort, but I'm unsure how all of that would really work.

Compared to the hydrolysis and DEA mechs, this one sounds a little too complex.
BUT if I am unable to solve the problems of the dielectric elastomers, I will pick this one.

I was calculating how much air flow you would need with this refrigerant in order to make the mech work, and as such, the amount of refrigerant gas you would need to compress back to liquid in order to do that:
- Since a human takes 3.24 steps per leg in a second while running, and since half of the mech needs 1500 liters for a single actuation, then it is safe to assume that the total number of liters in total per minute would be:
- 3.24 steps per second x 1500 liters x 60 seconds = 291,600 liters per minute.
So, 300,000 liters per minute of airflow, or 10,600 CFM is a really big amount.

This fan is capable of having such an airflow, and it has a diameter of 44 inches, or 110cm.I would need a compressor with this insane amount of airflow to work.

Needless to say, this is not viable.

... But I will still go through the trouble of finding out how much energy it would consume and how big it should be if it was a compressor unit.

This is a 10,000 CFM air compressor unit and it uses around 1800 kilowatts, or 1 megawatt of power.

This one below is a 1,000 CFM (cubic feet per minute)/33.6 CMM (cubic meter per minute) 8 bar air compressor and it uses 160 kilowatts (200 horsepower):

It also weights 4 tons.

Unfortunately, this is not viable. :/

Maybe measuring the compressor I'm looking at it incorrectly?

For example, looking at this chart of refrigerant gases, you can see that some of these need to be at more or less -30 degree celsius to stay at room pressure (14 psi), and as such, you would need to have a sufficiently big enough mass/cooling system to turn the used gases into liquid again.

I asked chatgpt, and for a air flow of 10,000 CFM, I would need around:
- Q=1.08×CFM×ΔT
- Q = cooling capacity or BTU/hr
- CFM = is the volume flow
- ΔT = the difference in temperature in fahrenheit.
- From room temperature of 25ºC (77ºF) to -30ºC (-22ºF)
- 1.08x10000x(77-(-22)) = 1,069,200 BTU/hr
QkW=QBTU/hr×0.000293071071 BTU = 0.00029308323 kWh.

(I don't know why the text is weird like this lol)

Q_{kW} = Q_{BTU/hr} \times 0.00029307107
- Q kW = 1,069,200 x 0.00029307107
- kW = 313.3 kilowatts or 417.8 horsepower.
It is not really a small amount, BUT, at least it seems more viable than before.

I just don't know how big of an air compressor I would need for 1 million BTU/hr...

Commercial/house air conditioner units can have up to 60,000 BTU/hr, and most of them use around 6,000 Watts per hour.

1,000,000/60,000 = 16.6666 x 6,000 = 100,000 watts or 133.3 horsepower.

The only problem is the size:

I found this marine air cooling unit with 360,000 BTU/hr:

You would need 2 to 3 of these for this mech to work.

Peltier pellets could also work, but those have only 20% of efficiency when cooling.

... Which makes me wonder: if my approximation of the 10,000 CFM of air is even correct, wouldn't this means that I wouldn't need such big screw compressor just to compress/cooldown the refrigerant gas?

Dielectric Elastomer Actuator Mech: ❓

Yes, it would be feasible IF the dielectric elastomer in question can lift at least 1000 times its own weight.

For now I'm still trying to find some place were the article with the high performance DEA is available, and IF I happen to find its, and IF happens to be simple enough to make, then it will my choice.

Source: https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11587/115871T/Challenge-of-creating-high-performance-dielectric-elastomers/10.1117/12.2581255.short

The article in question.

I forgot to write the pros and cons:
- Conventional DEA's materials are readly available and easy to find, most of the time.
- High performance DEA's materials really can't be sourced on stores and need to be specifically sourced through chemical companies.
- I have no idea how I will take liquid silicone rubber and turn it into 1mm thin thick square fibers for the actuators.
- Its actuation method is somewhat safe in small cases like the ones in the articles, but it is unknown how well it would work in thousands of fibers at same time, specially with such high wattages being required per actuator.
- It requires a really, really good insulation on the electronic equipment or else the electrons will just go though the insulation and toast everything in its path.
- Dealing with thousands of fibers will be a task on its own, not that the McKibben wouldn't have the same issue, but that is also a characteristic.
- It will be extra hard to figure out which fibers aren't working properly.
- Position control will need mechanical brakes.
Well, while I don't have access to the article in itself, I will at least try to find dielectric elastomers with a significant energy density and performance.

In the previous project log I used this one as a basis for calculating the weight, but I think I misscalculated something, since this one can clearly carry 1000 times its own weight (it can lift 200 grams while weighting 0.2 grams).

So, if I wanted to pull a weight of 3000kg, It would weight 3 kilograms, no?
1. "Modeling and Characterizing a Fiber-Reinforced Dielectric Elastomer Tension Actuator":
  Anyway, said actautor has a energy density of 10.7 Joules per kilogram.
2. "Printing Reconfigurable Bundles of Dielectric Elastomer Fibers":
  This one has 134 W/kg, so I may assume that since this one has 134 J/kg of energy density, meaning it can lift 10,000 times its own weight?
3. "A Jumping Robot Driven by a Dielectric Elastomer Actuator":
  This one has 28.71 J/kg.
4. "Triblock Copolymer Organogels as High-Performance Dielectric Elastomers":
  This one (use sci-hub) has its energy density measured in MJ/m³, which accordingly to chatgpt it is around 1600 J/kg and an efficiency of 90% from electrical input to mecahnical ouput.
5. "A processable, high-performance dielectric elastomer and multilayering process":
  This one has energy densities scales in watts and in joules, and it shows that it has a energy density of 2000 W/kg and around 90 J/kg...
6. "A large-strain and ultrahigh energy density dielectric elastomer for fast moving soft robot":
  This one has 225 J/kg, and around 2400 W/kg so also 20,000 times its own weight?
In any manner, how each DEA is synthesized accordingly to each article:

1: Modeling and Characterizing a Fiber-Reinforced Dielectric Elastomer Tension Actuator

The soft composite layups were prepared using VHB F9473 PC elastomer tape. Within the elastomer layers, cottoncoated polyester fibers were arranged in meshes with fiber angles ranging from 15◦ to 85◦ with a constant element edge length between samples. Then for each layup, a layer of the elastomer tape was applied on either side of the fiber mesh. Once the layups were prepared, single-walled carbon nanotube (CNT) electrodes (Carbon Solutions, Inc. P3-SWNT) were applied on both sides to make the completed DEA composite. Once prepared, the maximum stress in each sample was measured with both ends fixed, such that λ2 = 1. The DEA composites were attached to a custom-built tension testing machine made with a Zaber T-LA60 A linear actuator, Zaber TSB60-I translational stage, and a PCB Piezotronics 1102-05 A load cell. The samples were stretched taut, and the actuator was exposed to a step input and held at voltage until the measured tensile force stabilized. Actuation voltages ranged up to 9 kV (UltraVolt 10A24-P15-I5) and the data was recorded by a National Instruments USB-6009 DAQ card.
A sheet of VHB 4910 elastomer tape was used for the dielectric of this experiment and was biaxially prestretched to λP S = 5 to improve its dielectric properties and discourage pull-in instabilities at low ramp rates [20]. The elastomer was left to relax for 24 hours to minimize viscoelastic effects. At this stage, CNT electrodes were applied to both sides, and aluminum foil leads were attached to the nanotubes to connect later with the power supply. Fiber meshes were prepared following the procedure outlined in Section III-A with VHB F9460 PC elastomer tape layers encapsulating fiber meshes ranging from 15◦ to 75◦ and were applied over one of the CNT electrodes. Finally, polyamid seeding particles (Dantec Dynamics PSP-50) were distributed across the surface of the elastomer. The samples were then connected to a high-voltage amplifier (Trek 20/20C-HS) and actuated up to 5 kV at a rate of 50 V/s. A further increase in voltage leads to wrinkling of the dielectric, which causes out-of-plane deformations not predicted by the modeling. Images of the actuator were taken using a Nikon D7000 at a variety of voltages. The images taken were then modified to black and white images and processed using PIV software (TSI Insight 4 G) to obtain the deformation fields in both the DEA and the surrounding elastomer. MATLAB was then used to determine the strain fields and calculate the boundary conditions applied by the surrounding elastomer on to the DEA region. Another strain test was performed to attempt to improve the strain results. [20] showed improved DEA performance was achievable using higher strain rates and lower prestrains, achieving five times higher linear strains resulting from the increased viscous impedance which prevents pull-in failure. Following this, we fabricated another actuator made from VHB 4910 biaxially prestretched to λP S = 3.5 without a relaxation period, applied an encapsulation layer, and actuated it with step inputs up to 7.5 kV. Images taken from the Nikon camera were then processed to determine the intersections of each fiber element which defined the size of a given element. After this, the dimensions of the elements in their initial and final positions were used to calculate the engineering strain. This process was repeated for all complete fiber elements and the average was reported.

It seems that this "VHB F9473 PC elastomer tape" is just a transfer tape (61 dollars/300 reais for every 50 meters), the single-walled carbon nanotubes are just too expensive and the "VHB 4910 elastomer tape" is just a silicone rubber tape.

The "VHB4910" is easy to find, it is a silicone tape. It costs 100 reais (20 dollars) for every 20 meter of this tape, it normally has 12mm of thickness. I don't even know how I would attach the electrodes to it...

Translation: "it supports 3.4 kg of weight for every meter"

2: "Printing Reconfigurable Bundles of Dielectric Elastomer Fibers"

Dielectric Ink: Fumed silica nanoparticles (CAB-O-SIL TS-720, from Cabot Corp.) were dispersed in Ecoflex 00-30 (Eco30) part A (Eco30A) and part B (Eco30B) separately by mixing in a SpeedMixer (Flack Tek, Inc) at 2000 rpm for 18 min. 12 g of the Eco30B/silica mixture was weighed into a separate container and 0.36 g (3 wt%) of SloJo cure retarder was added and mixed for another 2 min. 12 g of the Eco30A/ silica mixture was added to the container. Finally, 8 g of SE 1700 (Dow Corning Corp.) base and 0.266 g of SE1700 curing agent were added to create a final composition with a weight ratio of 3:1 Eco30:SE1700 and 30:1 SE1700 base:SE1700 curing agent. The composition was mixed at 2000 rpm for 12 min in a SpeedMixer. The resulting dielectric composition included 7.88 wt% TS-720 silica, 32.8 wt% Eco30A, 32.8 wt% Eco30B, 24.5 wt% SE1700 base, 0.82 wt% SE1700 curing agent, and 1.10 wt% SloJo. To improve the dispersion of the nanoparticles, the dielectric ink was roll milled (Torrey Hill, T50) three times. The ink was loaded into 20 cc syringes and centrifuged at 4000 RPM for 20 min to remove any trapped air. Rheology measurements were performed on an AR-2000EX shear rheometer at 25 °C using stainless steel parallel plates with a diameter of 40 mm and a gap of 0.3 mm. After lowering the top plate to the target gap, the sample was allowed to settle for 300 s before starting the measurement. Oscillatory measurements were carried out at a frequency of 1 Hz over a range of shear stress from 1 to 10 000 Pa. Cured dielectric matrices were characterized by shear dynamic mechanical analysis (DMA) using an AR-2000EX rheometer. Samples of uncured dielectric matrix were loaded into the rheometer equipped with a 20 mm steel plate with a gap of 0.3 mm. The samples were heated to 100 °C while collecting oscillation measurements at 1 Hz to monitor the curing. After fully curing, samples were cooled to 25 °C and shear DMA was carried out at a strain of 1% over a frequency range from 0.1 to 100 Hz. Parallel plate capacitors were prepared by blade coating the dielectric ink onto ITO-coated PET. The dielectric ink was cured at 80 °C for 12 h. Gold particles were used to define top electrodes with a diameter of 1 cm. Capacitance measurements were collected using an Agilent E 4980A using controlled using a Labview program. Electrode Ink: Carbon black nanoparticles (AB100, from Soltex, Inc.) were weighed into Eco30A and Eco30B separately at a content of 13.8 wt%. The compositions were mixed at 2000 rpm for 18 min using a SpeedMixer (Flack Tek, Inc). 12 g of Eco30B/AB100 mixture was combined with 0.12 g (1 wt%) of SloJo curing retarder and mixed for another 2 min. 12 g of Eco30A/AB100 was added and mixed at 2000 rpm for 12 min in a SpeedMixer, followed by roll milling three times. The dielectric ink was loaded into 20 cc syringes and centrifuged at 4000 RPM for 20 min to remove any trapped air. Rheology measurements were performed on an AR-2000EX shear rheometer at 25 °C using stainless steel parallel plates with a diameter of 40 mm and a gap of 0.3 mm. After lowering the top plate to the target gap, the sample was allowed to settle for 300 s before starting the measurement. Oscillatory measurements were carried out at a frequency of 1 Hz over a range of shear stress from 1 to 10 000 Pa. Mechanical Testing: Samples of the dielectric and electrode elastomer for tensile testing were printed into rectangular planar sheets with dimensions of 0.8 mm × 60 mm × 60 mm. After curing, the sheets were cut into dog-bone shapes following the ASTM D412a standard scaled down by 2.5 times. Specimens were stretched until rupture on a homemade stretcher (Mint, Baldor) with a load cell (FUTEK LSB200, 2 lb, JR S-Beam Load Cell) at a strain rate of 0.1 s–1. Data was acquired using a LabVIEW program. For electrode inks, the resistance was measured by a Keithley 2636A connected to the two metal clamps of the stretcher. The measuring voltage was 1 V. Device Fabrication: A multicore-shell nozzle (Figure S3a,b, Supporting Information) was prepared by an Aureus Plus 3D printer with a layer height of 25 µm and an X-Y resolution of 43 µm, as described in the previous work.[41] The nozzle, dielectric, and electrode inks were mounted to an Aerotech 3-axis stage (Aerotech, Inc.). The pressure of each channel in the nozzle could be controlled by an Ultimus V pressure pump (Nordson EFD) and switched on and off by a solenoid valve while printing (Figure S3c, Supporting Information). The relative dimensions of the DEF samples were printed onto glass plates covered with a Teflon adhesive film (Bytac, Saint-Gobain). Because the ink rheology was temperature-dependent, quickly increasing the curing temperature leads to a viscosity reduction that causes the printed structures to sag under their own weight. Hence, printed samples were first cured at a low temperature of 60 °C for 24 h to drive solidification, followed by curing for 24 h at 80 °C, and finally for 24 h at 110 °C to achieve a fully cured state.

Fumed silica is cheap and easy to find, ecoflex is just sculpiting silicone rubber that already comes with its uring agent, carbon black is expensive but replaceable, teflon is easy and the last one is "cure retarder", I don't know where to find this exactly type, but there are ones you can buy online, you can even mix acetone or alcohol to silicone to make it more liquid and retard the curing process for some time.

3: "A Jumping Robot Driven by a Dielectric Elastomer Actuator"

"The fabrication process of multilayer DE includes two processes: the fabrication of single-layer DE and the stacking of multilayer DE, as shown in Figure 8. The DE material is VHB4910 produced by the company 3M, and the main material is acrylate. In the single-layer process, a DE film with a thickness of 2 mm was stretched to 12.25 times (3.5∗3.5) its original area by a biaxial stretching machine to obtain a pre-stretched DE film with a thickness of 100 μm. The pre-stretched DE film was taken out with a large retaining ring and a small retaining ring with inner diameters of 160 mm and 140 mm (PMMA, cut with a laser cutter), respectively. The upper and lower surfaces of the pre-stretched DE film were covered with a mask (Release film, cut with a laser cutter) which had been vacated for an electrode. The flexible electrode was applied by spin coating, and the electrode pad was attached. In the multilayer DE stacking process, the prepared DE with a small retaining ring was sleeved inside another DE with a large retaining ring, and the air bubbles between the two layers of DE were removed by rolling. The large retaining ring was cut off along the edge to obtain two-layer DE with a small retaining ring. The two-layer DE was then nested into a new DE layer with a large retaining ring. We repeated the above operation and ensured that the electrode pads were aligned in the alternating layers. Variety in the multiple-layer DE could be obtained according to the requirements of different actuators by this way."

Again, the "VHB4910" is easy to find, it is a silicone tape. It costs 100 reais (20 dollars) for every 20 meter of this tape, it normally has 12mm of thickness, which is more or less the thickness that I was thinking on working with... I don't even know how I would attach the electrodes to it...

Translation: "it supports 3.4 kg of weight for every meter"

4: "Triblock Copolymer Organogels as High-Performance Dielectric Elastomers"

We developed systematic synthetic strategies to tune the bimodal system’s stress-strain responses and viscoelasticity. First, short-chain cross-linkers with softer and more-extended chains were used to replace previously explored short and stiff molecules, such as hexanediol diacrylate (HDDA), thus achieving more tunable stretchability and tensile strength (Fig. 1C and figs. S2 and S3) (8). The cross-link density/gel fraction (fig. S4) as well as the stress-strain responses were further controlled by changing the concentrations of the short-chain cross-linker, PNPDA (Fig. 1C) (8). Without PNPDA, the DE shows a similar long stress-strain plateau to that of non-prestretched VHB (fig. S5) (5, 6). With the bimodal network structure, our DE stiffens after a critical stretch ratio in its non-Gaussian region (20), which can suppress EMI. This critical stretch ratio shifts to a smaller value as the cross-link density increases. Second, the concentration of hydrogen bonds was optimized in the DE network to modify the viscoelasticity while maintaining its stress-strain relationship. A small amount of acrylic acid (AA) comonomer (2.5 parts of weight) was added, which provides side groups to form hydrogen bonds with themselves, as well as with the –NH– groups on the CN9021 and PNPDA cross-linkers (fig. S6) (21). The mechanical loss factor of DE, a measurement of the viscoelasticity, was then decreased from ~0.22 to ~0.11 at room temperature and low frequencies (fig. S7) without changing the strain stiffening behavior (table S2) and high elasticity (fig. S8). After AA is added, hydrogen bonds partially replace covalent cross-links in the network. Hydrogen bonds act as weak, physical cross-links and can dynamically dissociate, leading to a lower glass transition temperature (Tg) (fig. S9) and higher chain mobility in the network (22). As more AA is added, hydrogen bonds become highly concentrated, and the density of covalent bonds decreases (fig. S7), which results in inhibited actuation performance (fig. S10). At frequencies above 20 Hz, the storage modulus and loss factor of DE also increase rapidly (fig. S11).

Asked web search GPT, all of these costs around 400 reais (75 dollars) per 100 ML/100g. Some don't even have a price tag for them, you need to ask a quote from the supplier.

5: "A processable, high-performance dielectric elastomer and multilayering process"

"We built a bimodal-networked elastomer using two cross-linkers with different chain lengths and tailored its electromechanical properties for high actuation performance. DE films were fabricated through solution processing and cured under ultraviolet (UV) light. The long chain segment in the bimodal network ensures large elongation, and the second relatively short chain segment raises the modulus at modest strains to resist the rapidly increased Maxwell stress during actuation and suppress EMI (Fig. 1A) (8, 17). Figure 1B shows the molecular structures of reactants. Detailed formulations and nomenclature of samples can be found in table S1. Butyl acrylate (BA) and isobornyl acrylate (IBOA) were selected as comonomers to lower the modulus and improve the toughness of copolymers, respectively (18). They were also important to reduce the viscosity of prepolymer solutions (19). CN9021, a urethane diacrylate (UDA) with a high molecular weight, was selected as the flexible long-chain cross-linker, and propoxylated neopentyl glycol diacrylate (PNPDA) was used as the short-chain cross-linker (fig. S1). 2,2-dimethoxy-2-phenylacetophenone (DMPA) and benzophenone (BP) were used as cophotoinitiators to ensure complete curing through the bulk and surface of the film.

"We developed systematic synthetic strategies to tune the bimodal system’s stress-strain responses and viscoelasticity. First, short-chain cross-linkers with softer and more-extended chains were used to replace previously explored short and stiff molecules, such as hexanediol diacrylate (HDDA), thus achieving more tunable stretchability and tensile strength (Fig. 1C and figs. S2 and S3) (8). The cross-link density/gel fraction (fig. S4) as well as the stress-strain responses were further controlled by changing the concentrations of the short-chain cross-linker, PNPDA (Fig. 1C) (8). Without PNPDA, the DE shows a similar long stress-strain plateau to that of non-prestretched VHB (fig. S5) (5, 6). With the bimodal network structure, our DE stiffens after a critical stretch ratio in its non-Gaussian region (20), which can suppress EMI. This critical stretch ratio shifts to a smaller value as the cross-link density increases. Second, the concentration of hydrogen bonds was optimized in the DE network to modify the viscoelasticity while maintaining its stress-strain relationship. A small amount of acrylic acid (AA) comonomer (2.5 parts of weight) was added, which provides side groups to form hydrogen bonds with themselves, as well as with the –NH– groups on the CN9021 and PNPDA cross-linkers (fig. S6) (21). The mechanical loss factor of DE, a measurement of the viscoelasticity, was then decreased from ~0.22 to ~0.11 at room temperature and low frequencies (fig. S7) without changing the strain stiffening behavior (table S2) and high elasticity (fig. S8). After AA is added, hydrogen bonds partially replace covalent cross-links in the network. Hydrogen bonds act as weak, physical cross-links and can dynamically dissociate, leading to a lower glass transition temperature (Tg) (fig. S9) and higher chain mobility in the network (22). As more AA is added, hydrogen bonds become highly concentrated, and the density of covalent bonds decreases (fig. S7), which results in inhibited actuation performance (fig. S10). At frequencies above 20 Hz, the storage modulus and loss factor of DE also increase rapidly (fig. S11)."

Asked web search GPT, all of these costs around 400 reais (75 dollars) per 100 ML/100g. Some don't even have a price tag for them, you need to ask a quote from the supplier.

6: "A large-strain and ultrahigh energy density dielectric elastomer for fast moving soft robot"

"Polymer design:
To develop a high-performance DE under low electric fields, we design a random copolymer of 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA), 2-ethylhexyl acrylate (EA) and dodecyl acrylate (DA) (Fig. 1a). The transparent dielectric elastomer was synthesized by mixing the three comonomers in one-step UV photopolymerization (Supplementary Fig. 1). In this strategy, the rich and highly polar CF3 groups in HFBA segments provide high dielectric constant.

I just asked web search GPT to find these chemicals, all of these costs around 400 reais (75 dollars) per 100 ML.

I know that this can sound disappointing after I copy pasted so much crap from these papers, but I was considering switching from Silicone Rubber to Polyurethane Rubber, at least for the electrodes.

Accordingly to web search GPT, higher tensile strengths for dielectric elastomers can POTENTIALLY increase its contraction ratios, its energy density, durability, dielectric breakdown limit and efficiency.

Polyurethane rubber can have a tensile strength as high as 44 MPa while Silicone rubber can have a range of around 10 MPa. Silicone rubber has an elongation of around 700% and polyurethane can have around 300% to 400% maximum. Polyurethane rubber would be more durable than Silicone rubber, and it would also be better at tear resistance.

And yes, I do intend on adding fillers for both materials both at the electrodes and at the dielectric layer, like silica powder, flash graphene, dielectric grease, titanium dioxide and fiberglass. So the current properties of either material can end up significantly changing.

It is a consideration, I don't know which one is the best for this job, and I can always mix a little bit of both.

I would need around 42 kilograms of polyurethane/silicone rubber.

I found out that there are more rigid and stronger silicone rubbers (like the ones used in tires) which rigid called "shore" raging from 00-05 to 45A. The polyurethane rigidity is from 60 going up to 75.

Well, I said all that, but it seems like it is bullcrap generated by GPT, since I found some Polyurethane/Silicone rubber suppliers that actually have a data sheet, and their tensile strength is around 3.5 to 2 MPa.
Some variantions can have up to 5 MPa and an elongation at break that ranges from 200% to 400%, but it doesn't seems like these values have any kind of relationship with tensile strength and shore hardness.

However, with that in mind, Polyvinyl Alcohol has a tensile strength of 40-90MPa, 200% elongation at break and a shore hardness of 70A. It also has 10 times better dielectric constant than silicone rubber and 2 times better than polyurethane rubber.
It is also cheaper than both.
However, it doesn't mean I will only choose PVA, I'm actually looking at several options, when I'm decided I will try to make an update.

By the way, I found dielectric elastomers that use liquid metals as soft electrodes. Hum...

Source: https://www.researchgate.net/publication/369887430_Liquid_Metal_Smart_Materials_toward_Soft_Robotics

Source: https://www.mdpi.com/2073-4360/14/4/710

Source: https://www.researchgate.net/publication/325271594_An_autonomously_electrically_self-healing_liquid_metal-elastomer_composite_for_robust_soft-matter_robotics_and_electronics

Thermoactive Actuators Mech: ❓

Esteban also suggested thermoactive artificial muscles, such as Nylon/Polyethyelene (fishing line) or shape memory alloys like Nitinol.

Of course, there are other options besides these, such as the silicone rubber carbon fiber composite artificial muscle that can lift 12,000 times its own weight (here).
This one works because the silicone rubber expands when heated, pulling the fibers apart, simulating a contraction.

These are interesting alternatives, but:
- They are too slow to contract.
- Even slower to relax.
- You would need a robust refrigerant system and turn the materials into composites with thermal paste for fast thermal dissipation.
- They reach even less than 10% to 20% thermal efficiency.
- You would need to separate the muscles in sections for a somewhat precise position control, if you are not interested on using mechanical brakes.
- They are cheap (the thermalpolymer ones) to find and make.
- They are the somewhat safe to work with, however, if the heater exceeds the polymer's temperatures, they will irreversibly melt and even catch fire. Ruining most of the muscle.
- You could "just" let the muscles in pressure bags with refrigerant liquid/gases that would evaporate at the maximum temperature the materials are allowed to heat up.
  Or maybe just flow oil/water all the time so the muscles always can easily cooldown.
  But both of these potions seem sketchy to me.
This video is about nitinol wires as artificial muscles, contracting and relaxing them by pumping water with different temperatures into the bundle.

Source: https://www.researchgate.net/publication/334490010_Shape_Memory_Alloy-Based_Spring_Bundle_Actuator_Controlled_by_Water_Temperature

If you need to pump hot and cold water this fast, wouldn't that be the same as having an hydraulic actuator tho?

I even thought on maybe attempting to make peltier plates on the fibers themselves, but these would be too small and complex to mass-produce at home.

And to be honest, even thought it has all of these cons, if Nitinol wire wasn't 700 dollars per kilogram, I would've used these a long time ago to make the mech.

By the way, there are a lot of variations on Nitinol wire, the cheapest ones are called "superelastic" and the "shape memory alloy" type is the most expensive.

I would love to DIY one of these, but you need titanium and nickel to be instantly refrigerated with liquid nitrogen at vacuum. Thus the price.

There are other shape memory alloys, shape memory polymers and thermoactive polymers, but I never found one type that is easy to make at home and it is super strong.
Maybe google didn't show me all the alternatives or I simply didn't mind to look closely enough.

This one article is about a high energy density shape memory polymer and it explains how the polymer is synthesized:

"Synthesis and Film Preparation:
This synthesis is a modification of a previously described synthesis for PDMS-based, amine-terminated macromonomers. (32) A solution of H2N-PPG-NH2 (Mn ≈ 400 g/mol, Jeffamine D400) and anhydrous dichloromethane (8.0 g in 150 mL, 0.13 mM) was prepared under a N2 atmosphere. Methylenebis(phenyl isocyanate) (MPU) was added in a 1:1 molar ratio of amine/isocyanate functional groups (5.0 g, 0.13 mM). The resulting mixture was stirred for 72 h at room temperature, until the solution gelled and partially precipitated. The synthesized polymer was quenched in methanol and then fully precipitated by adding an excess of hexane. The recovered polymer was subjected to vacuum evaporation for 2 h at 90 °C. Molecular weight according to GPC: Mw = 12.0 kDa, Mn = 10.6 kDa, ĐM = 1.1 (Figure S10). 1H NMR (400 MHz, d2-C2D2Cl4, δ/ppm): 7.75 (br, 4H), 7.30 (br, 4H), 7.03 (br, 4H), 3.93 (br, 2H), 3.81 (br, 1.5H), 3.45 (br, 17H), 1.09 (br, 17–18H) (assignments given in Figure S11). Elemental analysis data: Analytical calculations for (C39H62N4O8)n: C, 65.5; H, 8.7; N, 7.8; O, 17.9. Found: C, 64.3; H, 8.5; N, 8.3; O, 18.9 (remaining).
Film samples were prepared by drop casting 100 mg/mL solutions in CHCl3 onto SiO2 wafers treated with a monolayer of octadecyltrichlorosilane (OTS) to allow for easy removal of the film and dried for over 12 h at room temperature and then again at 70 °C for at least 24 h. Higher quality films were obtained using lower concentrations (e.g., 50 mg/mL compared to 100 mg/mL), though the resulting drop-casted films were much thinner for lower concentrations, due to the decreased solution viscosity."

I was curious, and it seems like there are liquid/gel based thermoelectric materials, which maybe it could make a fibrous thermoelectric/peltier unit possible.

Source: Cu2Se-Based liquid-like thermoelectric materials: looking back and stepping forward - Energy & Environmental Science (RSC Publishing)

Source: Liquid-like Materials May Pave Way for New Thermoelectric Devices - www.caltech.edu

Source: Popular strategies for constructing polymer gel thermoelectric materials (wiley.com)

I was searching for polyvinyl alcohol based ionic polymer actuators, which is basically like a mix of a fuel cell membrane and a dielectric elastomer. However, I did found this article about a PVA shape memory polymer artificial muscle able to lift 1,100 times its own weight.

Basically, it is treated with sodium hydroxide and... That's it.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7610272/

Other options: ❌

You may notice that the list is actually very small compared to the insane amount of different actuators out there, and that is simply because of a couple reasons:
- I only listed the ones that seems more viable and easier to DIY.
  Every actuator/artificial muscle sounds ✨amazing✨ when you read a news article about them, until you check its speed of contraction and relaxation, force-to-weight ratio, efficiency, cost, practicality and manufacturing process.
- Not all actuator types have their performance carefully explained and listed.
- Google simply didn't show me others.
For example, there is a type of electroactive polymer called "Ionic Polymer Metal Composite" (IPMC), you can ditch out the metal part, but most of the options that study/make this artificial muscle uses super expensive materials like gold, cobalt, nafion or a series of different materials.

The only article that I found about IPMC that actually cared about calculating its weight and output force achieved only a force-to-weight ratio of around 10, and it is made out of gold and nafion.

Source: https://www.researchgate.net/publication/263670086_Ionic_and_Capacitive_Artificial_Muscle_for_Biomimetic_Soft_Robotics

Video

Others like liquid crystal elastomers, magnetorheological elastomers, carbon nanotube artificial muscles, chemically activated actuators, even light activated actuators and so many more.

But, as you can guess, they either are super expensive to make, hard to make, inefficient, impractical, slow or just have a really bad force-to-weight ratio.

All options seem interesting, now I need to figure out which one I will choose to waste my money and time on just to see everything going into flames...
Project Log 81: Screw it, let's freaking do it.²
05/28/2024 at 14:59 • 5 comments
Tuesday, 28/05/2024, 11:41

Well, well, well...

I didn't, in fact, "do it" and finally start building things.

And the previous project log was so long it started deleting new text, so I'm forced to make this one.

Uuuuuuugh, this is me from the future, and even though I call ChatGPT stupid for not making math correctly, guess what? Neither does I, I keep forgeting certain parts on the equations and I need to make everything again and again.

This is me from the further future, you know what? I'm gonna redo all the calculations!

(obviously, you won't notice after the log is edited)

Not related, but look, I just found this cool scene featuring a mech:

(and yes, I go around youtube watching all kinds of mechs in media, I just think the scenes are cool)

-

In any manner, I'm trying to figure out how to make the McKibben hydraulic artificial muscles. And before I actually build those, I need to figure out how much force the materials will need to withstand and how much force the actuator will be able to output.

As you may not remember, since it was many project logs ago, the best way of making the most efficient hydraulic McKibben muscles is to make a non-elastic (but flexible) bladder and make it more filament like.
Not to mention that the easiest way to mass-produce filament-like McKibben artificial muscles is by using a small sock knitting machine.

Sources:
Anyway, I do need to figure out how to mass-produce the inner bladder, although I can buy kilograms of plastic tube, it would still be preferable to handmake those instead of buying, it will be expensive enough to buy the required equipment for the pump and electric motor.

This one costs 57 dollars or 250 reais (without the taxes).

Actually, I think I'm just overthinking the inner bladder thingie, I could "just" extrude it just like the filaments for the braided sleeve.

In any manner, it is only left for me to find out the optimal dimensions for the materials since I intend on applying 150 bars of pressure.

And after all of that, I need to figure out a way of making/testing/calculating the dielectric elastomer fibers, because I have a gut feeling that these braided sleeves won't be that great in the end.

Well, I think the first approach I will attempt on how to calculate the knitted braided sleeve is to assume each hole between the braided sleeve is a ring, just like in a chainmail.

This way I will probably find a rough estimation on how much force the fibers need to withstand in order to survive. Then I will add a safety factor of 7.

Funnily enough, the answers I got from ChatGPT are actually almost the same, but there is something I'm finding weird. Basically, they all agred that 900kg of force would be applied to the ring area and then divide the force bewteen the six links.
But since the tension on the links is being concentrated on 6 points, it doesn't make much sense that it would equally divide the force between linking points...

Maybe I should've asked it to pretend it is a chain link...

I got the answer and it keeps saying it is around 300kg or 2000kg, maybe the idea of a safety factor of 7 was asking for too much...

In either way, I will have to use those 2 ton sized HDPE ropes...

Well, I was looking at charts about Rope Strength based on material and thickness of the rope so I can figure out how thick should be the DIY HDPE rope for 2 tons in these artificial muscles, and lo and behold: any kind of polyethylene that doesn't use UHMWPE is not shown.

Source: https://denverrope.com/rope-strength-guide/

It seems like Nylon, Polyester and even Polypropylene have higher tensile strength than HDPE. :|

Well, Prolypropylene has an yield tensile strength (tensile strength before permanently deform) of 20 to 45 MPa, so this means that I still can use the composite of HDPE and graphene/silicon carbide to double the strength of the fibers of HDPE.

In any manner our rope of 40 MPa made out of HDPE+graphene+silicon carbide (I'm thinking on giving up on fiberglass it is kinda messy to work with) would need the following dimensions:
- 38mm of diameter and 3 twisted strands.
Well, I don't even know how I will fit this thing in a filament muscle with 28mm of diameter, lol.

Well, I asked chatGPT to use that old equation for McKibben muscles that I asked in this post

on worldbuilding stackexchange, but it gave me results around 900kg and 1600kg.

I tried to make the equation as follows:
- 15000*pi*28^2(3(cot(20)^2)(1-1.30*0.2)^2-csc(20)^2)
And it resulted in:
- 3142595105.5096786503920999.
(even if you take out the three zeros behind 15 KPa, it still gives around 300 tons of force, which is absolutely not possible)

I feel like I will never make this equation correctly...

Well, I found an article about a 21mm in diameter McKibben muscle that uses 7MPa of pressure and 8 kilonewtons (800 kg) of force.

Source: https://www.researchgate.net/publication/290316475_A_Method_of_Designing_and_Fabricating_Mckibben_Muscles_Driven_by_7_MPa_Hydraulics

I couldn't check it with sci-hub either, but at least this is a good indicator.
If we simply take the pressure and output and doubles, the result of 1600kg is also right.

kelvinA kindly shared the source for a free access article.

Source: https://www.fujipress.jp/ijat/au/ijate000600040482/

However, the article only uses 7 MPa as the maximum pressure input and 2 MPa as the nominal pressure input.

But in one of the graphs it is shown that in fact, it would output 800 kg of force with a diameter of 21mm.

At 2 MPa it outputs 300kg of force.

By the way, I was calculating the weight of the hydraulic fluid if I were to fill the hydraulic muscles.For example: let's assume that the muscles have 30cm (24cm when contracted) of length and a diameter of 28mm when fully actuated. So, this single muscle would weight 0.12kg.
- 0.12kg x 90 (9000kg of output) x 30 muscles in total = 324kg in total for the hydrauic liquid alone.
Just remember that in reality the artificial muscles would be way longer since I intend on braiding them to increase contraction ratios, so it would weight way more than that.
Sure, not all muscles would be contracted at all times, but letting things as simple as that wouldn't change much either.

Now I need to figure out where the hell I'm going to find 300+ kg of hydraulic oil (400 Liters). :|

If it was water, it would be easy to collect, now hydraulic oil...?

I think I could reduce the liquid volume required by using sponges or other materials, although the sponges aren't rigid, they still occupy space, but since they are solid and not compressible, they wouldn't allow for more fluid to get into the muscles.

Reducing the weight based on the amount of volume they are occupying.

I suggested sponges because it was the first thing in my mind, solid rods/chains of plastic/metal would still help to reduce the hydraulic oil required, but not saving in weight. HDPE has a density similar to hydraulic oil, it would still weight the same, but I wouldn't need to expend money on hydraulic oil.

Yes, I could "just" use water and a water pump.

But even then, I don't know anymore.

a 30kg brushless motor with a 80kw output converted to 300kw or even 400kw would weight around 120kg to 150kg.

How much would the pump weight?

So, 300kg to 400kg of working fluid + 120kg of motor + Xkg of pump + 200kg of fuel + 100kg of pilot + Ykg of skeleton (that would weight just as much as the rest of it) = 720kg + X + Y.

All of this crap just to lift 1 ton of weight...

I don't even know how to strike a balance of "weight required to be lifted" and "weight of the system".

Maybe someone smarter than me would've figured it out by now. Maybe a professional would.

... Or maybe a professional would rapidly understand that this whole endeavor is a waste of time.

Re-calculating:

I need to remember something:
1. The artificial muscles that I'm calculating have a length, force and speed proportional to a human sized humanoid. I did it at the start for simplification's sake, like a template I can easily edit later. Depending on the final size of the mech skeleton or even an exoskeleton, the input wattage/horsepower would considerably change, maybe triple or even octuple (8x).
2. On top of that, I do need a safety factor, which would increase the weight even more.
3. Last, I need to add more muscles to compensate for the weight of the strucutre of the mech itself, like the weight of fuel, pilot, endoskeleton and equipment (containing the hydraulic fluid if it is to be used).
I don't know which value to use for the weight of the skeleton, and it will heavily change based on the size and shape, which will also require the increase in actuator's weight.

It may be a waste of time to calculate the weight of the muscles and horsepower output even before designing the rest of the structure, but I kinda prefer to just take this part out of my mind first.

When I finally start designing the skeleton, I will need to come back here and use the weights as reference.

But it got me wondering, is making the next limb x times stronger than the previous one even a good idea?

This is literally an exponential equation that would only get out of control

Multifilament Hydraulic McKibben Muscles:

So, 2 MPa is already good enough, me thinks. The paper does say it would output around 300kg of force, and I think this is already good enough. The author literally had to use PBO fibers (expensive) and a 3 layer inner bladder for this one.

3 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 3 Extra force = 9 tons = 30 muscles x 6 stewart platform actuators = 180 x 0.12kg = 21.6kg x 2 sides = 64.8kg
- Torso: 9 tons x 3 extra force = 27 tons = 90 muscles x 6 stewart platform actuators = 540 x 0.12kg = 64.8kg
- Legs: 27 tons x 3 extra force = 81 tons = 270 muscles x 6 stewart platforma actuators = 1620 x 0.12kg = 194.4kg x 2 sides = 388.8kg
- 2.4 + 64.8 + 64.8 + 388.8 = 518.64kg in total.
- Safety factor of 2: 1,037.28kg
- Safety factor of 4: 2,074.56kg
2 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 2 Extra force = 6 tons = 20 muscles x 6 stewart platform actuators = 120 x 0.12kg = 14.4kg x 2 sides = 28.8kg
- Torso: 6 tons x 2 extra force = 12 tons = 40 muscles x 6 stewart platform actuators = 240 x 0.12kg = 28.8kg
- Legs: 12 tons x 2 extra force = 24 tons = 80 muscles x 6 stewart platforma actuators = 480 x 0.12kg = 57.6kg x 2 sides = 115.2kg
- 2.4 + 28.8 + 28.8 + 115.2 = 173.04kg
- Safety factor of 2: 346.08kg
- Safety factor of 4: 692.16kg
- Safety factor of 7: 1,211.28kg
1.5 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 15 muscles x 6 stewart platform actuators = 90 x 0.12kg = 10.8kg x 2 sides = 21.6kg
- Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 22.5 muscles x 6 stewart platform actuators = 135 x 012kg = 16.2kg
- Legs: 6.75 tons x 1.5 extra force = 10.125 tons = 33.75 muscles x 6 stewart platforma actuators = 202.5 x 0.12kg = 24.3kg x 2 sides = 48.6kg
- 2.4 + 21.6 + 16.2 + 48.6 = 86.64kg
- Safety factor of 2: 173.28kg
- Safety factor of 4: 346.56kg
- Safety factor of 7: 606.48kg
1.2 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 12 muscles x 6 stewart platform actuators = 72 x 0.12kg = 8.64kg x 2 sides = 17.28kg
- Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 14.4 muscles x 6 stewart platform actuators = 86.4 x 0.12kg = 10.36kg
- Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 17.28 muscles x 6 stewart platforma actuators = 103.68 x 0.12kg = 24.3kg x 2 sides = 12.44kg
- 2.4 + 172.8 + 103.68 + 124.4 = 403.28kg
- Safety factor of 2: 80.65kg
- Safety factor of 4: 161.31kg
Conventional Hydraulic McKibben Artificial Muscles:

Now I need to take that equation in the paper and see if I can actually find calculate something.
- F = (pi/4*(D0^2*P))*(1/sin(O0))^2*{3(1-e)^2*cos(O0)^2-1}
Well, I tried in MPa, in KPa and it still didn't give any result that made sense.
- (pi/4*(21^2*2000000))*(1/sin(20))^2*{3(1-0.20)^2*cos(20)^2-1}
- -565384994.5986882470453348857008804125900264872223170612834861024
But somehow ChatGPT was able to make the equation correctly for some reason. :|

The output force depending on the diameter at 2MPa would be:
For a 50 mm diameter muscle: approximately 13634 N / 1390 kg
For a 100 mm diameter muscle: approximately 54536 N / 5561 kg

Weight of one 50mm diameter muscle with 30cm length: 0.79kg

Weight of one 100mm diameter muscle with 30cm length: 4.77kg

3 times extra strength for every consecutive muscle 50mm:

Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
Shoulders: 3 ton x 3 Extra force = 9 tons = 7 muscles x 6 stewart platform actuators = 42 x 0.79kg = 35.55kg x 2 sides = 71.1kg
Torso: 9 tons x 3 extra force = 27 tons = 20 muscles x 6 stewart platform actuators = 120 x 0.79kg = 94.8kg
Legs: 27 tons x 3 extra force = 81 tons = 59 muscles x 6 stewart platforma actuators = 354 x 0.79kg = 279.66kg x 2 sides = 559.32kg
1.58 + 71.1 + 94.8 + 559.32 = 726.8kg.

2 times extra strength for every consecutive muscle 50mm:

Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
Shoulders: 3 ton x 2 Extra force = 6 tons = 5 muscles x 6 stewart platform actuators = 30 x 0.79kg = 23.7kg x 2 sides = 47.4kg
Torso: 6 tons x 2 extra force = 18 tons = 13 muscles x 6 stewart platform actuators = 78 x 0.79kg = 61.62kg
Legs: 18 tons x 2 extra force = 36 tons = 26 muscles x 6 stewart platforma actuators = 156 x 0.79kg = 123.24kg x 2 sides = 246.48kg
1.58 + 47.4 + 61.62 + 246.48 = 357.9kg
Safety factor of 2: 715.8kg

1.5 times extra strength for every consecutive muscle 50mm:

Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 4 muscles x 6 stewart platform actuators = 24 x 0.79kg = 18.96kg x 2 sides = 37.92kg
Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 5 muscles x 6 stewart platform actuators = 30 x 0.79kg = 23.7kg
Legs: 6.75 tons x 1.5 extra force = 10.125 tons = 8 muscles x 6 stewart platforma actuators = 48 x 0.79kg = 37.92kg x 2 sides = 75.84kg
1.58 + 37.92 + 23.7 + 75.48 = 248.8kg
Safety factor of 2: 497.6kg
Safety factor of 4: 995.3kg

1.2 times extra strength for every consecutive muscle 50mm:

Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 3 muscles x 6 stewart platform actuators = 18 x 0.79kg = 14.22kg x 2 sides = 28.44kg
Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 4 muscles x 6 stewart platform actuators = 24 x 0.79kg = 18.96kg
Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 4 muscles x 6 stewart platforma actuators = 24 x 0.79kg = 18.96 x 2 sides = 37.92kg
2.4 + 28.44 + 18.96 + 37.92= 87.72kg
Safety factor of 2: 175.44
Safety factor of 4: 350.88kg
Safety factor of 7: 614.04kg

3 times extra strength for every consecutive muscle 100mm:

Biceps/Arm: 3 tons = 1x 2 MPa muscle = 4.77kg x 2 sides = 9.54kg
Shoulders: 3 ton x 3 Extra force = 9 tons = 2 muscles x 6 stewart platform actuators = 12 x 4.77kg = 57.24 x 2 sides = 114.48kg
Torso: 9 tons x 3 extra force = 27 tons = 5 muscles x 6 stewart platform actuators = 30 x 4.77kg = 143.1kg
Legs: 27 tons x 3 extra force = 81 tons = 15 muscles x 6 stewart platforma actuators = 90 x 4.77 = 429.3 x 2 sides = 858.6kg
9.54 + 114.48 + 143.1 + 858.6 = 1125.72kg
Safety factor of 2: 2251.44kg

2 times extra strength for every consecutive muscle 100mm:

Biceps/Arm: 3 tons = 1x 2 MPa muscle = 4.77kg x 2 sides = 9.54kg
Shoulders: 3 ton x 2 Extra force = 6 tons = muscles x 6 stewart platform actuators = 12 x 4.77kg = 57.24 x 2 sides = 114.48kg
Torso: 6 tons x 2 extra force = 18 tons = 4 muscles x 6 stewart platform actuators = 24 x 4.77kg = 114.48kg
Legs: 18 tons x 2 extra force = 36 tons = 7 muscles x 6 stewart platforma actuators = 42 x 4.77kg = 200.34kg x 2 sides = 400.68kg
9.54 + 114.48 + 114.48 + 400.68 = 639.18kg
Safety factor of 2: 1278.36kg

1.2 times extra strength for every consecutive muscle 100mm:

Biceps/Arm: 3 tons = 1x 2 MPa muscle = 4.77kg x 2 sides = 9.54kg
Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 1 muscles x 6 stewart platform actuators = 6 x 4.77kg = 28.62kg x 2 sides = 57.24kg
Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 1 muscles x 6 stewart platform actuators = 6 x 4.77kg = 28.62kg
Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 2 muscles x 6 stewart platforma actuators = 12 x 4.77kg = 57.24kg x 2 sides = 114.48kg
9.54 + 57.24 + 28.62 + 114.48 = 209.88kg
Safety factor of 2: 419.76kg
Safety factor of 4: 839.52kg
Safety factor of 7: 1469.16kg

Fluid Flow:

Well, all options seem interesting...

However, all of these muscles still needs a fluid flow to supply them, and that needs to be taken into consideration for the hydraulic pump that is going to supply them.

Of course, let's take into consideration that:

The muscles will already be partially full, meaning I will need half of the fluid flow.
The plastic filler will also keep half of the muscle full.
The lower density of the hydraulic fluid would make the total weight slightly lower, but the amount of liters would stay the same.

The 21mm muscle - 2 times stronger than the previous muscle - Safety Factor of 2: 346.08kg

Actuated weight: 0.12kg if water, 0.1 kg if hydraulic oil
Unactuated weight: 0.08
0.12-0.08 = 0.04 kg of liquid need to be pumped for every fiber.
Amount of fibers: 346.08kg/0.12kg = 2884
2884 x 0.04 = 115.36 liters need to be pumped.
Since it needs to be delivered in a speed to make the muscle contract with a speed of 1.33 meters per second: I will admit, I have no idea on how much fluid flow this would require, but I used the Hydraulic Cylinder calculator, added a bore of 20mm and a stroke of 130mm at 20 bar, and it said that the total volume would be 0.04 liters, and in order to achieve 1.33 m/s, it said it would need 25.0699 liters per minute.
I also tried to take a Speed Calculator, inputing the speed and the distance, it gave me 0.015038 seconds, so I would need to supply 0.04 liters at 0.015038 seconds, which in one minute would be:
60 seconds / 0.015038 = 3989.89227291 x 0.04 = 159.595690916 liters per minute?
25.0699 LPM x 2884 fibers = 72,301.5916 LPM
36,150.7958 LPM if half of the muscles filled by the filler
18,075.3979 LPM if half of all muscles are actuated.
If we assume that the 160 LPM is true, then it should be: 115,360 LPM (divided 2 times)

The 50mm muscle - 2 times stronger than the previous muscle - Safety factor of 2: 715.8kg

Actuated weight: 0.79kg
Unactuated weight: 0.53kg
0.79 - 0.53 = 0.26kg or liters if water
Amount of fibers: 912 fibers
912 x 0.26 = 237.12kg or liters
Hydraulic Cylinder calculator said it is: 156.6869 liters per minute for a volume of 26 liters.
60 seconds / 0.015038 = 3989.89227291 x 0.26 = 1037.37199096 LPM.
912 x 156.6869 = 142,898.4528 LPM
71,449.2264 LPM if half of the muscles are filled by the filler
35,724.6132 LPM if half of all muscles are actuated.
If we assumed that the 1037 is true, then it should be 236,436 LPM (divided 2 times)

The 100mm muscle - 1.2 times stronger than the previous muscle - Safety factor of 2: 419.76kg

Actuated weight: 4.77kg
Unactuated weight:
4.77 - 2.35 = 2.42kg
Amount of fibers: 44 fibers
44 x 2.42 = 106.48kg or liters
Hydraulic Cylinder calculator said it is: 156.6869 LPM for a volume of 2.42 liters.
60 seconds / 0.015038 = 3989.89227291 x 2.42 = 9655 LPM
44 x 156.6869 = 6,894.2236 LPM
3,447.1118 LPM if half of the muscles are filled by the filler
1,723.5559 LPM if half of all muscles are actuated.
If we assumed that the 96554 is true, then it should be 106,210 LPM (divided 2 times).

Well, well, well... Isn't physics a pain in the butt some times?

If I take a hydraulic pump that produces around 7 LPM with 1750 RPM and 5 Nm of torque at 1.25 horsepower, I would need:

115360 LPM / 7 LPM = 16480
1.25 x 16480 = 20,600 horsepower.

236436 LPM / 7 LPM = 33776.5714286
1.25 x 33776.5714286 = 42,221 horsepower.

106210 LPM / 7 LPM = 18966.0714286
1.25 x 18966.0714286 = 18,966 horsepower.

Of course, this is using the exponential growth and a random value that I took, but if you divide it by the number of safety factors, since it would mean the number of times the pressure inside the muscles are divided, it would get a little better, but not great...

I would really love to know how I could reduce the amount of horsepower... I mean, did I really do the calculations correctly?

Dielectric Elastomers:

Although I already calculated the hydraulic McKibben artificial muscles, screw actuators, hydraulic cylinders, linear motors and all of that stuff, I'm actually very interested on Dielectric Elastomer Actuators.

Not because they are "cool" or anything like that, but because they would eliminate the need for a Hydraulic Pump and an Electric Motor to drive the pump. Both have their own complications to deal with and I'm really concerned on how in the hell I would make a BLDC motor capable of outputing 300 kilowatts and the ESC required to move it.

Not to mention that in the case of dielectric elastomers, I wouldn't need to worry about the weight of the hydraulic fluid, neither about tubing, solenoid valves and all of that stuff.

Yes, I would still need to figure out some problems, like motion control, electrical insulation and converting the electrical output of the fuel cells to 5 kilovolts and the like.

With that in mind, the electrostatic actuators would clearly be better suited for that, but I do wonder if it is possible to simplify its construction...

I also doubt my idea of reppeling fibers would work, so I do think I should just compromise and use a dielectric elastomer like this:

Source: https://www.researchgate.net/publication/350364525_Printing_Reconfigurable_Bundles_of_Dielectric_Elastomer_Fibers

As you can guess, this is a reversely actuated dielectric elastomer, sinze the inner electrode out get attracted to the outer electrode, increasing its length.

Although, I do wonder if it would be possible to mix this one with the below dielectric elastomer:

Source: https://www.semanticscholar.org/paper/Modeling-and-Characterizing-a-Fiber-Reinforced-Moss-Krieg/57618d574b2753dc81866fd89055609176d1c88f

This one has a braided sleeve just like a McKibben muscle, and it contracts just like one, but I doubt I would be able to print a continuous fiber like the previous example.

In either way, I need to figure out how much force dielectric elastomer fibers would output, and then I would need to figure out how much force they would also be able to output if they were braided like a rope.

From the GPT chats capable of search the web for actual sources, it seems that braiding/twisting ropes can increase the strength of said rope from 3 to maximum 7 times.
Obviously I will take the conservative approach of 3 times. and add a safety factor.

Anyway, actually trying to figure out how much force they would output and how much they would weight.

Accordingly to the article of the braided dielectric elastomer above, it weights 0.219 grams and was able to lift 200 grams.
Unfortunately I'm kinda confused about the contraction ratio, it keeps changing the number on "tensile strain", one time it says it is 14.7%, other says it is 2% depending on the testing conditions. Unfortunately, it doesn't tell the exact dimensions of the samples.

So, taking into consideration the probable size of milimeters of the Dielectric Elastomer in the images, I would assuming it is a few millimeter squares.
By the way, the article says it uses VHB 4910 elastomer tape and 5 to 7 Kilovolts, such as in the image below:

So, let's say it is 10 by 10mm and that its length is 300mm (30cm) or even larger since it will be braided/twisted, but let's take this length and then multiply a few times just to be sure.

0.200 grams x 30 = 6 grams = 200 grams of pulling force, I doubt it increases with length.
9000kg of pulling force / 1 fiber with 200 grams of pulling force = 45000 fibers x 6 grams = 270 kilograms.
270 x 30 actuators in total = 8100kg
Even if you use only 3000kg/200 grams it gets 90kg per actuator.

My face thinking the dielectric elastomer would be lightest actuator of them all:

I did find this acrylate based dielectric elastomer that was capable of lifting 8kg while only weighting 0.15 grams, this would be more than 50,000 times its own weight.

Source: https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11587/2581255/Challenge-of-creating-high-performance-dielectric-elastomers/10.1117/12.2581255.short

Unfortunately, like all good things in life, I don't have access to it, not even through Sci-hub.

And I don't know if this performance is intrensically related to the Acrylic itself or the use of SWCNT (single walled carbon nanotubes) in the electrodes.

And yes, I keep asking ChatGPT and searching google scholar myself for high performance dieletric elastomers, but for some god-forsaken-reason they never show me what I'm looking for.

Well, I literally looked around all day and I doubt I would be able to replicate the materials, since these high performance dielectric elastomers are normally made of super mega specific chemicals that would probably summon a demon if you spoke their names out loud.

I really don't know how to proceed with this project.

Did I take the weight of the actuators incorrectly? I didn't research enough for alternatives? Maybe the strength I'm requiring for the actuators is just too much?

What should I do...?

Pneumatic McKibben

And yes, I'm still trying to find ways of increasing efficiency of pneumatic actuators.

One example is this one, it is said to be 31.2% stronger and 25.6% faster than conventional pneumatic muscles.

Source: Actuators | Free Full-Text | Power-Efficient Soft Pneumatic Actuator Using Spring-Frame Collateral Compression Mechanism (mdpi.com)

Accordingly to chat GPT, if we take the percentages, it would be something around:

30% = 0.30
22% = 0.22
31.2% increase = 1.312
25.6% increase = 1.256
0.30*1.312*1.256 = 0.4943616 = 49.4>#/li###
0.22*1.312*1.256 = 0.36253184 = 36.2>#/li###

Since the article doesn't talk about initial efficiency, we can only extrapolate like this.

This other article says it was capable of reducing the losses in 70%, but I'm unsure of what kind of losses...

Source: Actuators | Free Full-Text | Energy Efficiency of Pneumatic Actuating Systems with Pressure-Based Air Supply Cut-Off (mdpi.com)

By the way, one interesting thing I think about Pneumatic actuators is that it doesn't matter much the pressure you work with, it is still the same amount of liters, because gases are compressible.

So, it would be a waste of energy to attempt compressing the gases to 15 MPa, the lower the pressure, the more efficient the whole system would be.

Supposedly...

But this still makes me wonder: if the majority of the losses in pneumatic systems is due to the work being converted into heat, then why not just heat the gas?

Gases increase in pressure inside a chamber proportionally to its temperature after all...

Like adiabatic-pneumatics or isothermal-pneumatics, where heat is either not exchanged or at least constant.

I found this article that uses a reversible fuel cell membrane to convert water into hydrogen and oxygen, making a unthetered pneumatic muscle.

Source: https://www.semanticscholar.org/paper/Soft-Polymer-Electrolyte-Fuel-Cell-Tube-Realizing-Nabae-Kodaira/e23633c26983e613c647139e917760feb9b52bb6

It is not hard to make a reversible proton exchange membrane, but it would be hard to make in this such high amounts...

... Or I could "just" use a central reversible fuel cell in one point like a pump and suplement the muscles in the mech...

One interesting thing is that I could re-use the oxygen and hydrogen in the fuel cell to recycle some of the wasted energy. Like a turbocompressor of some sorts.

Well, guess what? It would need a really small amount of water:

1 liter of water produces 1235 liters of hydrogen and 622 liters of oxygen.

Maybe in the end this is the solution for the mech?

Well, a reversible fuel cell/regenerative fuel cell is kinda hard to make, a simple hydrogen generator is easy, you can always just burn both for water again.

Although, I kinda wanted a regenerative fuel cell so I could react the hydrogen and oxygen after they're used so I could recycle some of the energy...

Wait, I could just build a hydrogen generator and a conventional fuel cell separately...

No, really, I'm serious, should I even attempt this one? This REALLY looks promising, simple, light and cheap to do.

My concerns are:

Hydrogen is known to be so light it can actually pass through solid materials, although many carbon fiber tanks for hydrogen have a polyethylene layer separating the fibers from the hydrogen.
If there is any leak at all (which will have, it is a pneumatic system), the lesser the gases to compress.
Hydrogen is combustable, and even worse than that: it has an invisible flame to the human eye. Should I only work with the oxygen instead?
There is also the issue of position control, pneumatics need precise control of antagonistic actautors, and on top of that, I don't know how much is difficult to make reliable progressive pneumatic valves.
Would the low efficiency of pneumatic muscles still be a problem?

I normally use the festo air arm as a reference, but that is already 13 years old.

While nowadays, James Bruton's video showed that you can, in fact make simple precision control of pneumatic actuators using arduino.

I also found this video, and its tittle made me know that there are in fact, mechanical breaks that could allow for reliable position control for pneumatics.

(unfortunately, for the life of me, I couldn't find a single image or video showing a pneumatic actuator with a mechanical brake)

There are also articles about position control using simple solenoid valves and mechanical brakes.

Source: https://www.semanticscholar.org/paper/Accurate-position-control-of-a-pneumatic-actuator-Varseveld-Bone/e356f88410d850013e1f827d996da41bbef0515f

Source: https://www.researchgate.net/publication/336642252_SENSORS_AND_POSITION_CONTROL_METHODS_FOR_PNEUMATIC_SYSTEMS

Screw actuator:

Before we start, I will need to calculate not only the size and weight of the thing (again), but also because I misunderstood something about volume and tensile strength.

You see, I saw once that Aluminium piston rods are 2 times bigger than steel ones, but they have the same tensilse strength, but 20% to 30% lighter.

So, my monkey brain went "this means that making it out of plastic would be even lighter!11!", which is absolutely stupid.

You just take the tensile strength of steel (200,000 PSI) and divide by the tensile strength of the material you want to use, then you multiply the result by the volume of said material and insert the density to find the weight.

For example:

1 m³ of steel = 7,850 kg
Tensile strength of steel = 200,000 PSI or 1378 MPa
Tensile strength of Aluminium = 95,000 PSI or 655 MPa
200,000/95,000 = 2.10526315789
1 m³ of aluminium x 2.10526315789
2.1052631578 m³ of aluminium = 5,705 kg

Now let's see HDPE graphene composite:

Tensile strength of steel = 200,000 PSI
Tensilte strength of Composite HDPE with graphene = 5801.51 PSI or 40 MPa
200,000/5801.51 = 34.4737835495
1 m³ of HDPE x 34.4737835495
34.4737835495 m³ of HDPE = 33,440 kg

As you can see, for every part made out of HDPE would literally weight 4.25 times more than any piece made out of steel (and yes, I know that a composite of HDPE graphene would have a different density, but that would probably make it maximum 20% to 10% lighter).

So I need to take a material that has a really good tensile/compressive strength, the first thing that comes to mind is carbon fiber, but that is just too expensive.
I also thought on aluminium matrix with iron or steel cables and silicon carbide for extra strength, or even using HDPE matrix in the place of aluminium.

Also, just now I remembered about an all PE based composite that could achieve around 1 GPa of strength. Maybe I could reach the same amount of strength by using HDPE.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7435843/

I found another which uses HDPE too:

Source: https://www.sciencedirect.com/science/article/abs/pii/S0032386118301514

The problem is that both UHMWPE and PE wax are expensive and harder to find.

(I said that and I immediately found a link for PE wax in my country costing 169 reais or 32 dollars the kilogram)

I also remembered about that DIY plastic that uses talc powder and PVA glue, I always assumed it to be weak or just acceptable, but I just saw some papers and they were capable of reaching tensile strengths close to 50 MPa of tensile strength.

Source: https://www.researchgate.net/publication/304572845_Structure_and_properties_of_highly_filled_poly_vinyl_alcoholtalc_composites_prepared_through_thermal_processing_effects_of_talc_size
(it is available on Sci-hub)

But this does makes me wonder:

PVA + Talc composite are obscenely cheap to buy and simple to make, but it is also has the problem of being soluable on water.
It would be like making a mech made out of paperboard, even if it was able to lift tons of weight, what is the point if it is going to melt in the rain?

This one uses polyvinyl alcohol with polyacrylic acid reached 50 MPa of tensile strength, maybe it would be less soluable in water.

Source: Super-strong and tough poly(vinyl alcohol)/poly(acrylic acid) hydrogels reinforced by hydrogen bonding. | Semantic Scholar

This one is on PLA (also on Sci-hub), but they "only" got to around 50-60 MPa.

Source: https://www.researchgate.net/publication/263573513_Effects_of_talc_on_the_mechanical_and_thermal_properties_of_polylactide

Well, first I will try to calculate the weight/volume of the all PE composites if they were to replace Steel:

1 m³ of steel = 7,850 kg
Tensile strength of steel = 200,000 PSI or 1378 MPa
Tensile sterngth of UHMWPE+PE wax composite = 1320 MPa or 191,449.8 PSI
200,000/191,449.8 = 1.04466027126
1 m³ of UHMWPE x 1.04466027126 = 1,013.3 kg

Almost 8 times less heavy than Steel while having the same volume, sweet.

However, there is always something, and this is that:

The articles don't specify if it is yield or ultimate tensile strength.
The articles also say it has increased elasticity/elongation of around 7.35%.

Both of these things may considerably change how much this thing would weight and how it should be shaped.

Accordingly to ChatGPT:

"However, for many engineering materials, the ultimate tensile strength is often found to be about 1.5 to 2.0 times higher than the yield strength 1 2. This means that the yield strength is about 50% to 67% of the ultimate tensile strength."

Well, then it is actually 2,026.6 kg.

Although this is the equation that I was thinking of using, I'm kinda concerned when it comes to the screw actuator. The articial muscles would be "easier" to fix, because they are cylindrical pieces of cloth, not solid pieces of material.

It could mean that in the end I would need to make 6 different types of screw actuators with widly different sizes of motors.

I could simply use the final screw and just add it to everything, but... The motors would still be a problem.

Well, first, I need to find a 3 ton rated screw actuator/lifter and then take its dimensions.

(I'm having no success)

I also tried to ask ChatGPT and other gpts with access to internet to take the general value that screw actuators normally use for the dimensions and outputs in order to make a conservative approach based on the generalistic data.

Then they reach the conclusion of 2+2=22 around 40 times.

Me: "I need you to figure out the pitch of the screw based on the torque, which is 45 Nm"

GPT: "Why, yes, thank you, the diameter is 12mm and the torque is 2389 kilonewtons per meter"

Me: "That wasn't what I asked, please, redo the calculation."

GPT: "Why, yes, thank you, the diameter is 12mm and the torque is 2389 kilonewtons per meter"

Me: "That wasn't what I asked, please, redo the calculation."

GPT: "you reached your limit of allowable questions for the day, pay for the premium for more."

It is kinda pathetic how people wasted billions of dollars just to make an AI that can't even make f*cking math, how is that even possible since the AI are literally made out of MATH!?

Well, at least let me check about the hydraulic cylinders, right?

They have more of less the same structure (without the threads and the like), so I could at least use it as a starting point...?

In any manner:

3 times extra strength for every consecutive actuator:

Biceps/Arm = 3 tons
Shoulders: 3 ton x 3 Extra force = 9 tons
Torso: 9 tons x 3 extra force = 27 tons
Legs: 27 tons x 3 extra force = 81 tons

Now that I separated every consecutive actuator, I think I see the issue... I did say that this leads to exponentional growth, which is absolutely insane...

2 times extra strength for every consecutive actuator:

Biceps/Arm = 3 tons
Shoulders: 3 ton x 2 Extra force = 6 tons
Torso: 6 tons x 2 extra force = 18 tons
Legs: 18 tons x 2 extra force = 36 tons

Well, I could only find a 30 ton hydraulic cylinder, and it is CHONKY.

I don't understand Mandarin (or Cantonese), so I don't know exactly which is the diameter of the rod and the diameter of the bore.
(Forget it, I found another link were it is in english)

It has 80mm of rod diameter and 140mm of bore (inner diameter) and a outer diameter of 168mm.

It is meant to work maximum 300 meters per second (somehow) and maximum 30 MPa of pressure, which reaches the 40 ton mark, at 30 MPa its pulling side reached 30 tons.
And since the rod will be sticking out in both sides, then it would be 30 tons for both sides.

It would need 827.3070 Liters per minute of fluid flow, and I'm supposed to ad 6 of these for each leg.

I won't even waste my time calculating this one, lol.

At least I now know how THICCC the screw actuator would need to be.

1.5 times extra strength for every consecutive actuator:

Now this one, the 10 ton hydraullic cylinder has 63mm of rod diameter, 100mm of bore diameter and 110mm of outer diameter.

It has maximum 7 ton of pulling force, so you know the drill, I will make the inner diameter a little bigger for the sake of reaching 10 ton. 110mm of inner diameter in this case.

It would also need 509.6085 liters per minute of fluid flow, or 3000 liters of fluid flow in total counting the stewart platform.

I can't go around making 4 different cylinders for each output force, so let's see how much fluid flow each would need:

Biceps/Arm: 3 tons = 500 LPM but with a pressure limiter for 5 MPa
Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 500 LPM pressure limiter at 7 MPa x 6 = 3000 LPM
Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 500 LPM pressure limiter at 10 MPa x 6 = 3000 LPM
Legs: 6.75 tons x 1.5 extra force = 10.125 tons 500 LPM with no pressure limiter also 3000 LPM
To supply one side of the mech at full speed: 9500 LPM.
I would "only" need 90 hydraulic pumps with 100 LPM of output flow.
Which would need around 585 horsepower in total.
Not great, not terrible.

The 10 ton hydraulic cylinder weights around 15kg by the way, so 1+6+6+6 = 19 x 2 sidez = 38x15 = 570kg in total for the hydraulic cylinders alone.

1.5 times extra strength for every consecutive actuator:

Now calculating with the proper hydraulic cylinder sizing:

3 ton hydraulic cylinder: 50mm of inner diameter, 28mm of rod, 300mm of stroke, 16 MPa = 107 LPM.

5 ton hydraulic cylinder: 63mm, 35mm, 300mm, 16 MPa = 170 LPM.

6 ton hydraulic cylinder: (I couldn't find one, so I will use the force of a 8 ton) 80mm bore, 50mm rod, 300mm stroke, 16 MPa = 245 LPM.

10 ton hydraulic cylinder: 100mm of bore diameter, 63mm of rod diameter, 300mm of stroke 16 MPa = 500 LPM.

Biceps/Arm: 3 tons = 107 LPM
Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 170 LPM x 6 = 1020 LPM.
Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 245 LPM x 6 = 1470 LPM
Legs: 6.75 tons x 1.5 extra force = 10.125 tons 500 LPM x 6 = 3000 LPM
To supply one side at full speed: 5597 LPM
I would "only" need 55 hydraulic pumps.
Which would need around 357.5 horsepower in total.

1.2 times extra strength for every consecutive actuator:

Biceps/Arm: 3 tons = 107 LPM
Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 107 LPM x 6 = 1020 LPM.
Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 245 LPM x 6 = 1470 LPM
Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 245 LPM x 6 = 1470 LPM
To supply one side at full speed = 4067 LPM
Which would need around 260 Horsepower in total.

In any manner, this would show how much the screw actuator would also weight and how much energy it would need.

Although, it would be 7 times lighter if made with the all PE composite + graphene.

Tomorrow I will try to make a 3D model of the screw actuator with the dimensions into consideration.

Well, guess what? The scroll in my mouse stopped working, now I need to wait until the new one arrives at my house.

Dang it, the project log is already reaching maximum limit of characters.

But before I create a new one to post the screw actuator design: to calculate the linear speed and force into horsepower, and it seems like in order to lift 3000kg at a linear speed of 1.33 meters per second, I would need around 1000 watts (1.33 horsepower) accordingly to chatGPT, which is probably wrong...

So maybe I misscalculated some things on the previous actuators?

Nope, it is 81 kilowatts for 1000kg of force, ChatGPT was indeed incorret.

Also, this would make it simpler for the screw actuators or even for hoist actuators.

Out of curiosity, energy consumption with the extra force:

81 + ((81x3)x6) + ((81x3x3)x6) + ((81x3x3x3)x6) = 19,035 kilowatts = 25,380 horsepower.
81 + ((81x2)x6) + ((81x2x2)x6) + ((81x2x2x2)x6) = 6,885 kilowatts = 9180 horsepower.
81 + ((81x1.5)x6) + ((81x1.5x1.5)x6) + ((81x1.5x1.5x1.5)x6) = 3,543.75 kilowatts = 4725 horsepower.
81 + (81x1.2)x6) + ((81x1.2x1.2)x6) + ((81x1.2x1.2x1.2)x6) = 2203.848 kilowatts = 2938.464 horsepower.

Well, I definitely misscalculated something in the hydraulic cylinders, because it should be way above the values I got.

Off-topic:

One thing I forgot to talk about more in depth was the plasma jet engines.

Although I talked about them more like a conventional turbine engine, with compressor, combustor and turbine parts, you could also use them as a Tip-jet rotor.

Basically, it is a type of propulsion system in which the rotor/propeller/blades are hollow and air is injected into them, the centrifugal forces compresses the air further and at the tips of the rotor there is the combustion chamber that generates thrust.

Source: https://www.researchgate.net/publication/252026659_Geometry_design_model_of_a_tip-jet_reaction-drive_rotor_based_on_coupling_analysis

The thing is: since it is a type of propulsion system that doesn't need a combustion chamber and a turbine to work the same way as a conventional turbine engine, you could, maybe, use it in a plastic plasma jet engine, only using the ceramic/metal parts at the tips.

Like this one.

Source: https://www.sciencedirect.com/science/article/pii/S1000936119302213

Maybe this could be useful to replace the 300+ kilowatt electric brushless motor, or it could even be used for a pneumatic McKibben muscle.

Adiabatic Combustion Engine:

SPEAKING of adiabatics...

There are a type of engine called "adiabatic engine", it is said to have around 50% to 60% of fuel efficiency.

Source: https://www.sae.org/publications/technical-papers/content/830314/

You "just" need to make all of the components out of insulating ceramics and then run it super mega hot so the energy loss to heat is minimal.

It can also be done by doing a very high compression very fast, when I was searching for the most efficient combustion engines in the planet, ship engines were always the first to appear, and those had meter long compression. But I don't know how I would avoid fuel detonation with an engine at 1200ºC

Project Log 80: Screw it, let's freaking do it.

03/09/2024 at 15:10 • 2 comments

09/03/2024, Saturday, 11:58

This project Log was another failure, I ended up doing absolutely nothing and just yapping and yapping.

I copy-pasted all my project logs to a google drive, it didn't pass the videos, neither some images because their link expired, but it resulted in literally 999 pages.

999 pages of time wasting.

Maybe I never wanted to finish this project, I just wanted to distract myself, or something. Who knows...

Literally no one reads these logs, but sorry, I'm procrastinating a lot for some reason.

Not just in this project, but everything in my life right now. I don't understand it either.

I was thinking on keeping this as a draft until I actually made something, but... Right now I'm pissed and confused, so I will leave this here, I'm still adding new content whenever I actually make said content (like buying the goddang pump).

I hate this project...

Being honest, I feel like I hate myself more. I literally didn't even make a single scaled-down prototype of any of my ideas...

You know what? Screw it all, let's just do it. DO IT.

Screw efficiency, screw precision, screw reliability, screw durability, screw it all! Let's JUST DO IT.

In any manner, let's begin with the beginning:

The energy source will be any kind of stationary generator that I can get my hands on, even if it means just plugging it directly to a plug in my house.

I could find a lot of combustion engines with a single cyinder, in fact, I found a few motorcycle ones that achieved 75 horsepower.

The problemo is that it costs 4000 reais (800 dollars).

I don't think that I can make any kind of electric motor that can properly work, so I was thinking of using the REB-90 number of poles and energy consumption as a basis for an air core linear brushless motor:

I will make the coils out of casted aluminium, not the best, but cheap and easy do find and melt (easy enough, at least).

I kinda want to use normal electric motors instead of linear motors, but for now, the production of it seems easier than the conventional one.

The coils will be encased in silicon rubber or epoxy resin (the cheaper I can find) with the thermal paste for heat dissipation and maybe fibers for strength.

This means that it will looking like a thick, long spaghetti.

The specific number of turns on each aluminium coil is still unknown to me, I still need to calculate that stuff.

On top of that, I need to find a way of making the ESC for a brushless motor that needs to get hundreds of amps and hundreds of volts...

One interesting fact is that I don't really know how many volts I should have since the voltage in a brushless motor defines its RPM, which would be dozens of times faster than mere centimeters per second of linear speed.

The structure will be any crap that I come across, be it wood, steel, aluminium or even Polyethylene.
I don't give a damn, I will just build it thick enough until it stops breaking.

That's it.

Now I "just" need to do it.

Actuator:

The torque of the REB 90 is 300 Newton meters, and since the motor has 27cm of diameter, then a linear version would have 200kg of pulling/pushing force. But this is a spaghetti linear motor, so only pulling force.

The kilowattage is rounded up to 80kw, but in reality it uses 60-70kw continiously. In any case, since it uses 800 volts, it would use around 100 amps. Accordingly to the AWG of aluminium wire, I would need 1AWG of aluminium wire, which is 7.5mm of diameter, almost a centimeter.
Since it has maximum 4000 rpm with 800 volts, I would assume that its KV is 5. I don't need the speed of 4000 rpm in linear motion, but the actual number depends on the position of each linear motor.

I forgot the number of poles and slots that the REB-90 was supposed to have...
I did count 59 magnets and 44 slots in the 3D models that I've made. Dunno if it is correct, the number of poles and slots should be dividible by 2 and 3 (2 poles and 3 phases).
So it is probably 60 poles and 45 slots.
Also, I forgot: this is the widing calculator: https://www.bavaria-direct.co.za/scheme/calculator/

Now I don't think this winding scheme/calculator is a good example for a tubular linear electric motor, since the coils would be one above another in this case.

If I find the winding process too difficult I may just stick to the conventional square linear motor...
Maybe it will be easier to turn a induction motor into a tubular motor, they are already stacked in a diagonal, just need to straight it out:

I can't find for the love of me the number of turns required. It changes between 10 and 200 turns in each stator. :|

Plus, the Reb-90 is a long motor, with aorund 20cm of height/thickness, meaning that I would need to make the turns like it was in a 20cm long slot, and then keep it in a tubular shape for the linear electric motor actuator.Well, I will do the following: I will make a 3D model occupying the space around the stator teeth, by taking the volume and the density of aluminium, I can find more or less how many turns I would need.

It would occupy around 90 cubic centimeters of space, and since I'm assuming the original would use copper wire, it would weight around 800 grams. But since it has 45 slots, it would weight around 35kg, in total, but the original is said to weight around 23kg.
Assuming that the copper weights 15kg in total, then each coil weights around 300 grams instead.
Taking a volume, density and weight calculator, it would be 2.51 meters in length.

By the way, since the Reb90 has 27cm of diameter, it would have 84cm of length. So it would also actuate 84cm, totally 170cm of length in total. But it would be so long the electromagnets wouldn't be able to "catch" the moving part.

I'm buying the parts to make the furnace, but I don't think I will have enough aluminium scrap to use...
Also, I was thinking on 3D printing a coil and then use it as a mold for a paraffin/wax sacrificial mold.
But an AWG 1 aluminium wire has only 7.5mm of diameter, which wouldn't make it pretty solid. I was thinking on making a pretty solid coil as the mold, something like this:

I will try the two types and test it out which one is better.

It is embarassing how much time it took me for 3D model these square coils on Blender. All the tutorials that I found are crap.

I really need to learn how to use FreeCAD. I will try it tomorrow, I'm done with this crap for today.

Maybe I should just make a giant ass spiral on a bucket of sand mixed with sodium silicate and then cut it to size for the aluminium coils.
The problem is: a spiral made out of what?

I thought on maybe using one of those giant syringes with a hole the exact size and then extrude some partially molten paraffin.

In any manner, just now I stopped to considerate the weight and price of everything.

Although I assumed each coil would weight around 300 grams, in actuality it would probably weight around 100 grams maximum.
So, since every spaghetti muscle has 45 coils and more 60 replacing the permanent magnets, I would have 10kg per muscle with the coils alone (not counting all the silicon rubber and so on), and since I would need around 30 of these per limb, I would have 1575kg of weight in total.
On top of that, the initial problem of not being able to find aluminium scrap and other metals in general doesn't help.
Asking around 100 sellers online, I could only find 2 that would sell aluminium scrap per kilogram, and they offered 60 reais (12 dollars) per kilogram, so this would already explode into 9000 reais (1800 dollars), which is a pain in the ass.
Yes, I can go around scrapyards and attempt on find more scrap, but like I said on previous project logs: it is hard as hell to find scrapyards that actually sell their scrap, they normally buy and resell to other companies/government.

I can only find aluminium scrap for 50 reais (10 dollars) per kg, a seller said they would sell for 20 reais per kg (4 dollars), but when I was looking the price that crushed soda cans are sold for, it was just 6 reais (1,20 dollars) per kg.
For the life of me I can't find anywhere that sells for that price.

This means that I would be forced to use the idea of dielectric elastomers were fibers with the same polarity are close to each other, repelling each other, simulating a muscular contraction. You could use anything to mix the carbon/graphite with, silicone rubber, latex, plastic etc.
But unlike the previous idea, these don't have any kind of position control at all. Electric motors (rotary or linear) have a easy and practical way of making position control even without encoders, you "just" need to "freeze" the waves in one position and that's it.
The DEA's only turns on or off, so if you want the muscle to contract half-way, you would need to low the power input, sacrificing strength over position control. This way, I would need to be forced to make the actuators way stronger than they need to be in order to lift something half-way.
The other idea would be to turn on and off the muscles at high frequencies so they stay in one position only. This seems promising, but I'm concerned with the durability of the material, since the higher the frequency, the faster dielectric breakdown occurs.

Of course, unless I use the equivalent for an linear electric motor that uses electrostatic charge with 3 phases:

Source: https://www.sciencedirect.com/science/article/abs/pii/S0957415814000324

... Buuuut I don't know how to mass produce it with these materials...

There is always hydraulics...

... I could maybe use a mix of hydraulics and encoders to lock the limbs in certain positions... Maybe...?

Maybe I could use encoders in the limbs and use antagonistic control like it is done with pneumatics...

One thing about the Dielectric Elastomer Actuators is that the dielectric material has a dielectric breakdown limit, for example, Silicone Rubber has a resistance of 250,000 volts per cm of thickness. By adding other dielectric materials, such as titanium oxide, teflon and/or dielectric silicone grease, you can increase the resistance to 1.000.000 volts/cm or more.

This is relevant because every dielectric elastomer, as its name suggests, needs a dielectric layer. The thinner the layer, the stronger the electromagnetic force, but the thinner it is, the lower the voltages it can withstand.

Most dielectric elastomer actuators shown in articles have layers with micrometers, or even nanometers of thickness. And accordingly, they need very little voltage to work, but also very little work to do.
It would be wonderful to have a 1 nanometer thick layer with whatever dielectric breakdown you want, but that is not how things work...

Of course, one thing that is also relevant to note is that if you have parallel wires, the voltage is divided by the number of wires.
So, even if you have very high voltage, if you divide by the number of fibers, you don't need thick dielectric layers.
I was thinking on using something more akin to a rope going around the limbs, but it seems that I will need to find a way of connecting the fibers to the limbs, like ligments and tendons.

Well I didn't show many images in this document, so here is a shitty drawing I made explaining:

The good news is that I could use burnt wood and grass for charcoal and turn charcoal into graphite, then mix it with any kind of plastic, rubber or whatever.

THis plastic, rubber or whatever that I could mix with graphite and/or graphene could allow for a cheap conductive material, while the dielectric layer, the more expensive part, could be applied later.

By the way, mixing white glue and talc in a 70:30 ratio will make a material that acts exactly like plastic (source).
Both are cheaper per kilogram than silicone rubber and plastic, because, like always, I can't fucking find plastic scrap to recycle anywhere.

Well, I found some websites were people sell scrap of everything, the problem is that I need to own a company in order to even have an account and see the prices.
Luckily, I have family members that have companies and I can buy the scraps through them.

But now I'm divided between actually going through with the dielectric elastomer fibers or the aluminium linear motors...

Speaking of it... Why I can't find dielectric elastomer actuators that are fibers just the way I described? I do wonder if it is because it doesn't work or if it is because nobody thought of it yet...

Which makes me wonder if it would work the same way if conventional electromagnets, although I don't know how one would make fibers have the same electromagnetic polarity...

By the way, I was complaining that the aluminium linear motors would weight 1575kg in total, but if you remember: dielectric elastomers with 20 grams of weight can lift 1000 grams (1kg) of weight, a difference of 50 times its own weight.

This means that if I wanted to lift 10.000kg, the muscle would weight 200kg (at least), the requirement of lifting 10 tons is due to the fact that this muscle would need a disadvantage of 10:1.

So, if there are 30 of these in total, then it would be 6000kg.

Well... That ratio is questionable in this scenario, those are meant for conventional DEA that are sandwiched by horizontally connected actuators, not parallel fibers.

By the way, I think I found a method to make the dielectric fibers as thin as possible without the nano needle, it is called "electrospinning".

The only problem is that I can't create single continuous fibers, so I don't know if it would still be okay for dielectric fibers...

Then, you have 5-3 ton rated hydraulic cylinders that only weight around 10kg each...

... But you would need a single motor or a motor for every cylinder...

Ugh... Back to square 1...

I don't know how to properly size the fricking pump...

Well, I would guess that I "just" need to make an electric motor and pumps with the total horsepower required.

If legs needs 100 horsepower for 1 ton of weight, then I would use x number of pumps that fit in that power input/output.
And then, the body sensors would automatically regulate the oil flow based on the sensors you pressed more during movement.

But even then, I don't know how well it would work. Every hydraulic cylinder needs a fluid flow of 200 liters per minute and around 30 bars of pressure (assuming just 3 cylinders are actuated).
But... If I take the information of hydraulic pumps with 100 liters per minute of fluid flow and stack them, I would need way more than 100 horsepower to compensate...

Or I simply misscalculated things, because I tried again with that hydraulic pump chart from aliexpress and I would end up using around 40 horsepower.... It is probably incorrect (again) because it would mean that I would be able to do the work of 100 horsepower with the energy of 40 horsepower, meaning I simply calculated a perpetual montion machine. lol
Actually, that isn't the case, I recalculated and it seems I actually misscalculated the initial 10 horsepower per 100kg of weight. Huh...

(I inserted too much rpm for the limb and ended up being 109 hp)

Also, the hydraulic cylinders are in diagonal because of the stewart platform configuration, so they would probably need to be even faster than the linear one, which could explain the horsepower.

If I make a electric motor for every joint, the coils would be too heavy for the insane amperage. If I make linear electric motors, the issue continues. If I make dielectric elastomers, the insane voltages will fry everything and it will still weight a lot. If I make hydraulics, the central electric motor can be too heavy still and not as responsive.

Screw it, we ball.

I just bought a hydraulic gear pump with a displacement of 28cm³, which would be around 50 liters per minute at 1750 rpm and 98 liters per minute at 3500 rpm.

And yes, I know that gear pumps are not that efficient (80% to 85% efficient) and that they only start pump properly once they reach around 1/3 of its rated nominal rpm.
There are way more efficient hydraulic pumps such as axial and radial piston pumps, but these are at least 10 times more expensive than my little gear pump.

Now, when it arrives, I will have to make a copy out of plastic scrap or epoxy resin...

By the way, this is how you extend the hydraulic pump:

Also, for some fricking reason I'm feeling utterly stupid because of this project...

By the way, I don't feel confident on the idea of using a super long hydraulic pump or a pump with multiple stages.

Not exactly because I'm afraid of the precision, but because the distribution of fluid flow through the pump.
For example, if I were to make the pump like the example above, then I would need the same amount of torque to drive a single actuator moving in the mech's body.
If I connect everything in a weird parallel system, the fluid flow may suffer from the distribution and turbulent flow through the system until it reaches the required actuator.

So, the idea is to take this hydraulic pump, 3D model it in Blender and then make a bigger version of said pump, 3D print in resin and then finally make a mold with a physical copy.
Yes, theorically I could "just" take the measurements of a hydraulic pump's blueprint that I could find on the internet and attempt on making a pump.
Actually, I did try that before on previous project logs, but it didn't go well because I didn't had any kind of reference or palpable scale on the pump. So I ended up with a 3D model full of mistakes that I couldn't tell for sure if it would actually work or not.

(I would have posted the screenshot of what I'm talking about, but the archive where I used to make 3D model sketches got corrupted and I lost a lot of things)

Being honest, I don't like this idea that much, because I feel it would be a waste of time and money to buy a perfectly useful pump just to throw it away. But hey, I will at least try it.

Oh yeah, I also have the option to literally 3D scan the thing.

By the way, I did look for solenoid valves to use as solenoid pumps, but they aren't efficient, and on top of that, they never tell the pulling force that the solenoid has, only the holding force, which really doesn't matter in this specific use.

Also, I forgor the dimensions of the hydraulic actuators:

85mm of bore diameter, 50mm of rod diameter, 30 bar of pressure, 311.7245 liters per minute to achieve linear velocity of 1.4m/s with 1000kg of force.

Pump needs around 10Nm for 30bar and 3500 rpm for 100 liters per minute of fluid flow, needs 14 horsepower (30Nm + 3500rpm) per hydraulic cylinder.

For a single leg, this would be 44 horsepower (90Nm + 3500rpm). Assuming that every limb actuates (legs + arms + torso) = 220 horsepower, however, not all limbs will be activated at once, neither at full force and speed. Still, the electric motor/pump must be built to achieve that, even if for a few brief moments.

Now, I'm between adding chain-gears from motorcycles/bycicles to connect both pump and motor, but I would love to make a direct connection. Le problemo is that I don't know if I have enough precision for that.

The hydraulic pump arrived today, I will disassemble this bitch tomorrow (newsflash, I don't have the the tools to open this now, I need to buy them, I've been using those jaw locking clamp pliers and hammering the living hell out of it and the screw didn't move a fricking milimeter).

By the way, this thing weights like, 10kg or so, and even though the insides are completely oiled, I couldn't even rotate the axis.

Note to myself: when you double the scale of a object, its volume increases 8 times.

I doubled the size of a cylinder with 1 liter of volume and it changed to 8 liters, square cube law guys.

This is relevant because of the 3D model of the hydraulic pump.

Even though I'm first focusing on the pump, even if I'm able to make the electric motor to run all of this, I don't think I will be able to supply enough energy to it either through batteries or generators.

I'm afraid I would require to use copied combustion motors for it...

Actually, I don't even know if copying a conventional combustion engine would even work. You see, they are built with the strength of Steel in mind, no the strength of plastics and resins.

An HDPE piston rod would need to be around 3 times thicker than the aluminium one.

Also, I do remember that once I showed some scientific articles showing micro generators that I could DIY. The "trick" is to use a gearbox that converts the output shaft rpm and torque to a very high rpm and very low torque.

... I mean... Whatever, one thing at a time. Now hydraulic pump, next electric motor, next ESC, next combustion engine, next generator.

Now I need to make a hydraulic pump based on a real hydraulic pump.
Then I need to make the hydraulic valves.
Then I need to make the hydraulic hoses.
Then I need to make the hydraulic tank.
Then I need to make the electric motor.
Then I need to make the controller of the motor.
Then I need to make a combustion engine from scratch.
Then I need to make a generator.

No matter what I do, this fucking screw doesn't move a single milimiter.

I literally crushed it using my vice and hammered the entire thing in an attempt on moving it.

My jaw locking clamp plier is all messed up.

And I don't know if I actually bent the hydraulic pump by accident or if it already came like this.

The gears are turning just fine, so it i probably just superficial level stuff.

Just now I remembered that you could use a heat source to force the metal do expand, I just don't know if it would work or damage the hydraulic pump.

It is me from the future.

My heat-gun broke.

It literally spilled its heating wire in a molten metal mess.

In either way, I'm so f*cking pissed right now that I'm willing to actually buy another pump from the same seller, but paying more for him to disassemble it for me.

FRICKING FINALLY!

By the way, my uncle unscrewed the pump, I still had to hammer this crap for the parts to separate.

The video tutorials always show the disassembly process like a walk in the park, but me? I just idented every single part of this accursed thing trying to take it apart.

Dunno if you can see it, but basically, this is a shaft seal. I couldn't take it off for the life of me and now it is completely ruined.

There isn't a single goddang tutorial on how to replace this specific type of seal, I bet you literally need to burn it off and when replacing with a new one, use heat to fix it in place.

It seems to be this type of seal, unfortunately, it isn't like the one in the image, or else I could've actually removed it.

Needless to say, this seal is fucking awful, I will need to use a new one in the new hydraulic pump.

I'm half procrastinating, half sick as hell. But hey, buying an actual hydraulic pump wasn't that bad of an idea after all...

You see, I checked all of those highly detailed 3D models on GrabCAD and I noticed that they never have things right when it comes to the gear teeth and sealing in general.

However, one thing that actually makes me kinda regret it was those functional water gear pumps on thingiverse and the like.
I could've actually skipped all this trouble by 3D printing and molded those things from the beginning. But a part of me says that they wouldn't perform as well as actual hydraulic pumps (not that I have the resources those youtubers have to test all these parameters).

In any way, I think I should start scanning the parts on a printer scanner so I can make vector shapes from those things.

And yes, I did try to find blueprints from which to make these vector shapes, but I couldn't find any.

If only I found an image like this with every part...

For some reason right now I'm kinda interested on the possibility of linear screw actuators, they have an efficiency as good or better than the current hydraulic system that I'm planning, and they are supposedly easier to make.

(Like I said, I need to make these things quicker or else I end up changing my mind after I already bought all the materials.)

But... I don't know...

I really need someone's help with this project... :/

I know that I said "hydraulics are simpler than electrics", but now I'm in face of a electric motor that would need 300 amps and 900 volts to drive a hydraulic pump that I don't even know if it woud be efficient or even practical.
How I even begin to design the ESC for this beast?

I made the math, and I would need 2.5kw for each screw actuator, but 12.5kw for every pulley actuators.

The only issue I have with this idea is that I always assumed stewart platforms to distribute its loads equally between all actuators at all times, which is not the case.

I was thinking of using something like this... But I don't know if this stewart platform is hyper flexible because it has extra actuators or because of its unique joints.

Well, guess what?

I was right, unfortunately.

In a rough estimation, if a stewart platform is expected to handle X amount of weight/load/force, each actuator should be able to output and/or withstand at least Y amounts of that force/weight/load.

And the general rule that ChaGPT/BingGPT/PoeGPT comes with is that each actuator should at least be able to output 1.5 to 3 times the force you want to output and withstand a load of 7 times the output force.

Whenever I choose hydraulics, mechanical or electrostatic actuators, this is the "rule of thumb" for the stewart platform, and thus, the actuators would need to be built accordingly.
Even if I actually had the capability to properly calculate all the loads, I would still need a similar factor for safety factor.

Which kinda sucks because this means extra weight for extra strength.

"But Fulano, are you sure you want to trust the stupid ChatGPT?!"

Well, I always ask on forums and other websites specialized on the subject, and most of the time I don't receive answers at all, so this is really my last resort.

Besides, I did receive a single answer on reddit, and it was suggesting that every single actuator to be able to output at least 3 times the force you are expecting to apply.
So literally 9 ton actuators to lift a single ton.
Not exactly great...

Well, since I would need 2.5 kW to move 500 kg at 1.4 m/s, then I would need 22.5 kW for 4500kg at same speed, and around 45 kW for 9 tons.

A freerchobby 15kw motor weights around 2.88 kg, and since I would need 30 of these (at least), it would weight 86.4kg (at least).

There are in fact, 45kw motors out there and these often weight around 5 to 7kg, so 150kg to 210kg in total respectively. But I think that is overkill anyway.

Now, unfortunately, I will have to figure out the number of poles, turns and teeth in this electric motor, just like the REB-90. I had all the time to do that with that motor, but now I have to do the same thing all over again...

Well, I couldn't find any information on the motor, but I found this one:

It is named a "30kw freerchooby", however, when looking at its wattage output, it actually peaks at 26kw.

It is said to have

MOTOR: MP 15470
KV: 55
MAX POWER: 30KW
RATED POWER: 12kw
MAX CURRENT:300A
ESC:120V 500A ESC /22S 500A ESC
MAX VOLT: 100V
RPM: 5500
SIZE: 154 x 69.5( without shaft )
TORQUE: 50Nm
THRUST:60KG
POLES: 20 (40 MAGANET)
SLOT:36
PWM:8-16KHZ
TIMING DEGREE: 15
NET WEIGHT (kg):3.5

I don't know what "net weight" means, but I will guess that it is the weight of the motor. So, with 30 of these, it would weight around 105kg.

And dammit, it also has 300 amps, how the hell does this produces only 50 Nm of torque with 300 amps while the REB-90 can produce 300 Nm with only 100 amps?

Well, f*ck.

I decided to make the screw actuators instead of hydraulic cylinders, but now that I actually calculated the weight, it would be a pain in the butt either way.

Basically, making the screw actuators with HDPE tubes with 50cm of length, 20cm of diameter and 3cm of thickness, it would weight around 8kg each (believe or not, when using beam loading calculators, the thinner I made the walls of the hdpe tube, the stronger the load it was able to withstand for some reason.

8kg x 6 actuators per limb x 5 limbs = 240kg in total.

Well, this is optmized to simply withstand 2000kg of weight in either compressive or bending loads, and since I need to make not only the screw, but also the outer tube to hold it in place. With 20cm of inner diameter and 5cm of thickness, it would increase the total weight to around 27kg each + 3.5kg of each electric motor.

30.5kg x 6 actuators x 5 limbs = 915kg

bruh...

Now I know how aerospace engineers feel.
Like a rocket, the heavier it is, the more thrust you need to move it, and more thrust requires more fuel, which makes everything heavier.
Obviously, rockets don't go infinitely in this loop, I "just" need to find a weight to force ratio that allows this mech to exist...

Each brushless motor is capable of lifting 2 tons and a little more, but goddang it, I will need to spend 50horsepower just to stand and walk?
And even if I didn't use an independent brushless motor for every limb, I would still need more and more powerful motors to pump hydraulic fluids.

Well, I asked ChatGPT for advice:

"Interpretation
A weight to force ratio of 0.4575 means that for every kilogram of the actuator system, it can handle approximately 2.18 kg of force. This ratio is a useful metric to assess the efficiency and effectiveness of the actuators in handling loads relative to their own weight.

Summary:
Total Actuator Weight: 915 kg
Total Force Capacity: 2000 kg
Weight to Force Ratio: 0.4575

This analysis shows that your actuator system is relatively efficient, given the substantial load it can handle compared to its weight. As you mentioned, this optimization challenge is similar to what aerospace engineers face, balancing strength and weight to achieve the best performance. If you need further optimization, consider materials with a higher strength-to-weight ratio or redesigning the actuator assembly to reduce weight without compromising structural integrity."

Then I asked again:

"Carbon fiber composite weight reduction:
Carbon fiber composites can be around 70% lighter than HDPE for the same strength.
If the HDPE actuator assembly weighs 30.5 kg, a carbon fiber version might weigh approximately 9.15 kg (30.5 kg * 0.30).

New Total Weight:
Weight per actuator with motor: 9.15 kg + 3.5 kg = 12.65 kg
Total weight for 6 actuators per limb and 5 limbs:
12.65 kg × 6 × 5 = 379.5 kg
12.65 kg × 6 × 5= 379.5 kg

Force to Weight Ratio:
Given the force capacity remains 2000 kg:
Weight to Force Ratio = 379.5 kg
2000 kg = 0.18975

Weight to Force Ratio = 379.5kg/2000kg = 0.18975

This means the system can handle approximately 5.27 kg of force for every kilogram of the actuator system, achieving a force to weight ratio of over 5."

And yes, I know ChatGPT is not the most trustworthy AI bot out there, but honestly, do I have any choice left?

In any manner, I do think I'm looking at this problem through the wrong perspective.
This is a Screw actuator, not a hydraulic one. I don't need 100% solid walls, I could make these with holes and protuding structures and even hollow beams for support.

On top of that, even if eventually switch back to hydraulics, I do think that 30 bar of pressure is just too low for the actuators.

HDPE can survive even 30MPa of tensile strength and compressive strength, I could elevate the hydraulic pressure to 150 bar (15Mpa) or even 200 bar (20 MPa) and stay with relatively smaller components.
For example, if I increased the pressure to 150 bar, the hydraulic cylinder would need to be only 6.5cm wide inside of it, and a wall thickness of 5cm, it would only weight 5kg, maybe 2 to 3kg with the rod and valves. And it would result in 8x6x5 = 240kg in total.
Of Course, this is counting in the pulling hydraulic actuators, I doubt they would be capable of pushing.

I used pressure vessel calculators and it seems like 5cm of wall thickness is ok enough, but 7cm is the ideal thickness.

Now I need to figure out what should be the ideal thickness for the rod of the hydraulic cylinder, and then recalculate the weight.

It seems like 10 to 15cm of diameter for the rod is enough.

By the way, in hydraulics, the pushing and pulling action are absurdely different in strength, accordingly to the hydraulic calculator, this 6.5cm wide hydraulic rod would push with a force of 5000kg while the pulling force would be 2000kg.
You can "solve" it by making the hydraulic cylinder a double rod, but then you will have a giant rod sticking out of the back of the actuator.

Both would weight around 10kg together, and since there are 30 actuators in total, it would weight around 300kg in total. By the way, this is with a safety factor of 7, even lighter than the screw actuator.

... But this is weird, it has more or less the same dimensions of a 3 ton steel hydraulic actuator, but it weights just as much...

Well, I reached those results (wall thickness, rod thickness etc) by using online calculators and inputing the yield strength of HDPE (25 MPa) and things like that, however, now that I directly asked all the GPTs around the internet, they actually calculated/said that the dimensions of the materials would need to be severely bigger in order to withstand its strengths.

For example: I did calculate the pressure vessel to have 5 to 8cm of wall thickness for safety factors, but being a pressure vessel is different than being a pressure actuator. So I presume it would need to be even thicker (and thus, heavier) for safety and strength related to sustaining both the pressure and the weight put on it.

In the screw actuator I actually took that into consideration and you could use virtual spring/impact dampening with the electric motor programming, a hydraulic cylinder would need something similar, which if I recall correctly, is named "snubber" for some reason.

As you have noticed, I'm kinda stupid, and I completely forgot to considerate the weight of HDPE composites and not only HDPE.

For example, I was planning on using flash graphene and/or milk graphene to incraese its strength, not to mention fiberglass and silicon carbide.

In either way, fiberglass and silicon carbide can double to triple the strength of polymer composites with around 30% per weight. Although I don't have the information about how much graphene increases the strength of a material per weight, we can make a conservative estimation that it would also double the strength.

However, adding all the three at same time may not result in an "adding" of strength nor in a "multiplication" of strength.

I don't know what should be the ideal mixture, but I would risk going 10% of each and 70% of HDPE.

I asked multiple times to all the ChatGPT's out there and all of them said that it could increase the tensile and compressive strength to around 2 to 2.5 times if all three are added individually, but not together.

Well, in any case, their sources normally observe that when making a non-uniform composite of HDPE, the benefits start disappearing when 30% of the additional material per weight of HDPE is reached. You could use either 30% of a single one or a mix of all three.

In either case, I'm adding the three because of by uga-buga brain says that the safety factor would surpass even though my conservative estimations are just 2 to 2.5 times.

Either way, it would only cut the weight to around half, from 900 kg to 450-500 kg in total, and taking out around 40% of the weight trough the honeycomb structures that I was planning, the total weight of the actuators could still reach around 180 to 200kg.

(the electric motors will also weight around 90-110kg on top of that)

Although considerably better, it is still a lot and I would need to check the final weight of other actuators.

Don't forget the fuel (200kg), the pilot (100kg) and skeleton (not known yet).

Just now I noticed that I've made a 2 ton actuator and not 4.5 ton, which is not the value I need to output.

It should be at least 1.5 times the value, so 4.5 tons, which would still make both electric and hydraulic weight even more.

In any manner, I remembered that structural solidity is not the way of optimally using polymers.
In short, a rope rated for 2 tons made out of polyethylene will always be the same size than a steel rope made for 2 tons, but lighter and cheaper.
So, the optimal way of using HDPE in the actuators is not structuraly, but in tensile applications, like artificial muscles.

Well, well, well... How many times I will be sent to square 1 until I learn my lessons?

Now I need to figure out a way of calculating how much force the HDPE threads need to withstand with hydraulic McKibben muscles, and that was one of the reasons I discarded the idea: I couldn't figure out how to reliably calculate McKibben muscle sizing and output.

I found this article that shows stackeable and modular vacuum artificial muscles, I should take it as inspiration for the Mckibben muscles for ease of production and the like.

I don't know, but maybe I'm just trying every single alternative before making the next step.

For example, I would love to make and test the dielectric elastomer fibers that I described.

And on top of that, I was "researching" a little bit about plasma jet engines, some time ago a team of chinese researchers made a microwave plasma thruster that used a few kilowatts of power.

Although we already have combustion engines, this one is interesting because you don't need the complicated stuff surrounding the combustion ones (supposedly).
So, the idea would be to replace everything on a combustion engine by plastic or cheap metals and having a lighter and cheaper engine.
(I said the same thing about the hydraulic actuator and it endend with the same weight and size)

Maybe I could make an electric engine to rotate a pump with hundreds of horsepower without using copper, laminates or complex electronics.

The first big issue with this thruster is the heat it produces, they needed to use a metal base with the plasma going through a quartz channel.
Even modern cutting edge turbine engines that use super alloys to survive its absurd temperatures, they still use ceramic coatings and air/liquid cooling channels in the turbine blades.
The only thing that makes me thing that one could maybe make a conventional metal turbine is the possibility of using these cooling channels, after all, that is how plasma cutters survive.

(plasma torches have 95% efficiency on thermal transfer by the way)

The only thing that makes me think that this might actually be lighter is that HDPE is better at making ton lifting ropes than actual hard structures.

By the way, this one of the methods to 3D print metal:

Energy Source:

I don't really know what to use for energy source for this thing.

I mean, obviously I would need to plug it on something, even if it is the electricity of my house, but I don't know how to supply kilowatts of power with a cheap equipment that I can buy online.

Remember: I can only spend 300 reais (60 dollars) per month.

Which makes things... Hard.

Also, I just found out something interesting.

On half a hundred project logs ago I thought on using alkaline fuel cells instead of other sources of energy, but since the density of hydrogen is really small, it wouldn't be viable to go carrying a 500 liter high pressure hydrogen tank around.

And one of the interesting stuff I learned is that alkaline fuel cells could theoretically use any kind of fuel containing hydrogen, including hydrocarbons. However, the carbon content would poison the sodium hydroxide (responsible by the reaction and name of this type of cell) and make the fuel cell useless.

However², I just found out that there are molten alkaline direct carbon fuel cells, which uses a molten Sodium Hydroxide at around 650ºC to convert hydrocarbons (fossil fuels) and air directly into electricity.

Supposedly, it can reach 80% efficiency. However, as you can imagine, their useful life-span is not that great, and the paper I linked above uses Inconel alloy 600.

I searched online and I could find a sheet of inconel mesh with 30cmx30cm costing around 500 reais (100 dollars).
I don't know if that would be enough to completely supply a 200 horsepower fuel cell...

Also, it seems I was mistaken, the "direct carbon" part literally means that it uses solid carbon as the fuel, not hydrocarbons.

Somehow, coal and graphite have energy densities equal or higher than hydrocarbons. And yes, this includes charcoal.

Which makes me wonder: should I use the heat of the molten electrolyte to turn the bio-mass into charcoal?

Direct carbon fuel cells supposedly could also use solid hydrocarbons, the only solid hydrocarbon I found was paraffin wax/paraffin oil.
Dunno if they would work as well as coal and the likes on this type of fuel cell.

Unfortunately, it seems like this type of fuel cells is kinda of a single use type. It needs water to keep the molten hydroxide from carbon poisoning, so, if the water runs out, the cell will eventually stop working.

The article I linked above (which I should've read completely before posting) says that the material lasted around 40h in an average of 1 watts (that kept decreasing).

Which is an interesting time span for this system, but it also means I would need to increase the system by 100,000 times more to reach 100 horsepower.

Which is not possible.

So all of this section was a waste of time.

Well, actually, since I said earlier that this fuel cell has the same energy density than gasoline, then it would be safe to assume that I would need around 100kg of charcoal to power it for the same amount of time.
I just don't know how big the electrolyte chamber would need to be to convert all the carbon into electricity on demand tho.

It is like having a firebox/boiler, how much charcoal I can pump into it without suffocating the flames?

One way I thought on doing that would be by calculating the heat in the mass of the electrolyte and calculating how much of its heat it would lose depending on the amount of kilograms of carbon mass and liters of air it would receive to realize its chemical reaction..

I forgor the exact numbers of joules and the like, but I would need 20 kilograms of molten sodium hydroxide electrolyte and inject 20 kilograms of charcoal with 200 liters of air per hour for 100 horsepower-hour of energy.
This would be like, 0.333 kilograms of charcoal per minute and 3.3 liters of air per minute, you could literally supply the air with a computer cooler fan. lol

My only concern is that I'm unsure on how much energy I will actually be able to collect, my insecure mind tells me that I really won't be extracting 75 kilowatts of power with a simple inconel and copper mesh like in the article I showed before.

Well, I asked again and again and again to every type of chatgpt that there is out there and reached a rough estimate of a metal mesh size required to output 100kw of power with this fuel cell.
It changes from 12 square meters and 10 square meters, so basically, metal meshes that are at least 10 meters wide and 10 meters long, which would weight around 20 to 30 kilograms.

And since inconel metal mesh is expensive as f*ck, I will be forced to use Stainless Steel 316L or 310 and use welding rods that come in that grade.

I'm back again, and accordingly to my calculations, I would need around 40kg worth of stainless steel 316L welding rods in order to reach 10m², which would cost around 5000 reais (1000 dollars). Which is not viable.
However, I calculated what would be the value with 1kg of steel 316L wire with 0.8mm of thickness and it would be around 19m² of surface area.
My only concern is that this could fricking melt the goddang wire...

... Even though I like the idea of using this supposedly simpler fuel cell, I don't feel confident on this idea, specially because I don't see how this would generate around 100 to 300 horsepower peak with this setup...
And this is still using MOLTEN SODIUM HYDROXIDE.

Every idea I try to explore (mentally) I feel like it is not going to be practical enough, I guess that is the biggest obstacle of every research on exoskeletons/mechs.

(being honest, I don't even know which one is best: molten carbonate or molten hydroxide fuel cells)
(definitely molten hydroxide, lithium carbonate is expensive as f*ck)

Oh crap, just now, after 2198398021389 project logs and going through article after article about fuel cells and fuel reforming, I finally found a compact equipment that can actually convert hydrocarbons into hydrogen.

It is called a "plasmatron fuel reformer" or "plasmatron fuel cell", however, it is a relatively new technology and I still didn't go through a lot of articles, but it seems it can be both used as a fuel converter and as a fuel cell.

Source: https://www.sciencedirect.com/science/article/abs/pii/S221298202030113X

There is a lot of different types, but it is said that the vortex design (the above image) is the most efficient until now.

I just read the article and it is about converting Co2 into other products, but maybe you could use to convert hydrocarbons into hydrogen?
The only problem is that... Well, at this point, I don't know if using hydrocarbons is efficient for hydrogen generation, you are basically waisting half of the fuel to take out the hydrogen.

In 1 liter of gasoline, you have around 34 megajoules (34 million joules) of energy, then, taking the hydrogen out of this one liter, you get around 14 megajoules of energy in the hydrogen content.

Well, I asked PoeGPT to take the values hydrocarbons alone (gasoline, kerosene, methane etc) and make a conversion of 30% (assuming it is the conversion in a combustion engine) and then take the hydrogen content in these fuels and making a 60% conversion (assuming it is the efficiency of fuel cells) and interestingly enough, the final energy in joules of each fuel is pretty close.

Which is interesting to say the least, that taking hydrogen out of gasoline and then passing through a fuel cell would generate as much energy as taking the gasoline and passing through a combustion engine.

Although, it does make me wonder how much energy you would be able to extract with a direct hydrocarbon fuel cell...

And by the way, Palladium can store hydrogen around 900 times its volume, which is insane.

If palladium wans't a super expensive and rare material, the fuel cell problem would be essentially over.

I do wonder if it would be possible to synthesize materials with a particle accelerator tho...

Well, while I'm procrastinating to make the 3D model of the new hydraulic pump, I was searching for thermoelectric generators (again).

Although it is not very efficient (below 10% efficiency), it seems like the more you increase its temperature, the more efficient it becomes depending on the materials you use.

There are materials that aren't gold, germanium and the like and work wonders for thermoelectric materials. However, they are still super complex and super expensive to make/buy/find.

The best I can do for now is asking which materials have high "ZT" to chatgpt, and it goes explaining the material is mid at best.
For example, copper oxide, silicon carbide, silicon metal, graphite powder, iron, nickel and the like.
Supposedly I would need to make a good mix of materials to increase the efficiency of the thermoelectric generator.

It needs to have good electrical conductivity, but low thermal conductivity and good seebeck coefficient.

If I could precisely calculate what values I need, I could try and elaborate a good ratio of material for each characteristic I require...

I'm still procrastinating while "studying" about combustion engines, and one very interesting thing I came across whas porous recuperator combustion engines.

Basically, on the top inside of a piston engine cylinder they insert a porous mesh were the fuel is injected through and during combustion, instead of a conventional flame forming, all of the fuel is combusted in the recuperator, basically making a hot-air engine.

Source: https://www.researchgate.net/publication/50283981_Potential_of_Porous-Media_Combustion_Technology_as_Applied_to_Internal_Combustion_Engines

The same applies to turbine engines.

It is also increases the efficiency of thermoelectric generators if you pass the flames through this said porous material, since the heat will be transmitted more efficiently through this porous material.

Source: https://www.mdpi.com/1996-1073/15/15/5597

The best way I can think of how to explain this is that it is that the porous media acts like thousands of micro fuel injectors, burning the fuel and air as efficiently as possible.

However, you need to size it properly, or else the air bubbles will become traped in the material, producing a heat insulator (like the ones in the space shuttle) instead of a fuel burner.

Structure:

I don't know what to use as the structure, I was thinking on either buy HDPE or get more aluminium scrap, I still don't know what to do with it...

Also, an idea for the structure: rolling contact joints.

These seem quite interesting.

Project Log 79: Testing things out.

02/03/2024 at 19:07 • 6 comments

03/02/2024, 15:55, Saturday.

So, remember when I said "You can't run from the laws of Physics"?

Good, because I should listen to myself more.

Basically, the human body doesn't use 300 watts, it uses the same amount of energy as any other equipment.

If the human muscles used less energy than it produces, this would mean it is a perpetual motion machine.

This means that all the equipment that I bought in the hopes that it would consume less energy than it produces is completely useless and stupid.

This means² that I wasted too much money. Again.

In any manner, I will be in my room and thinking on how to proceed with this project. :)

My room:

Well, at least I bought Silicon Carbide:

You know what? I will just post this and let anyone willing to help, give me a hand, because gawd, do I need it...

Well, I feel like I'm being ahead of myself again and creating this project log too soon....

In either way, I spent another 300 reais (60 dollars) to buy other materials. But I will only be able to buy the rest of the materials next month (thus my concern to make this too soon).

Now I will have the adjustable power source, silicone rubber, dielectric silicone grease, silicon carbide, sodium silicate and sucrose.

An odd selection of materials, but let me explain them:

The silicone rubber will be used to mix with graphite powder (which I already have) for the dielectric elastomer electrodes.
The silicone grease will be used to make the dielectric layer on the dielectric elastomer.
Yes, I did say that I would use Polyvinyl Alcohol and Polyvinyl Acetate to change the positive side and the negative side. But it would be cheaper to do the way I'm doing, after all, I will just test it out.
The sodium silicate, silicon carbide and sucrose will be used to make the porous heater.
I will mix the three with water and once it is solidified, I will heat it over until the sucrose turns into dust, leaving a porous structure behind.
I will use it to test if I can turn 1 liter of water into steam in 1 minute without requiring 47 kilowatts.

However, I'm still missing a few things, like the high voltage low amperage transformer for the dielectric elastomer actuator and dielectric pump and the PVA for the hydrogel heater I talked about in Project Log 77.

I will take another month to buy these two and test it out.

After all of that, I still need to test my hypothesis on the eccentric electric motor that I also talked about in Project Log 77.

That one will require 3D modelling and 3D printing.

... Which I didn't even started yet... y-y

Well, the adjustable power source just arrived, but I can't use because it doesn't come with a fricking plug.
It is supposed to be fed by another power source, either from a bigger adjustable power source or one of those switched power supply.

And I don't have one of these, I mean, I have one, but it is not for this voltage.

Either way I will have to wait for another fricking month until I can actually test some things out.

And yes, I can only spend 300 brazilian bucks per month.

Highly Porous Heater:

Since I already have all the materials to make this one, I'm still highly confused about the ratios I need for this thing.

I should've had thought this through (history of my life), because I'm pretty sure I would need to test various ratios for the perfect heater in this case.

And I just have a kilogram for each material.

I really should've paid someone to do this for me (like I had any money to do so)...

Although... I think it would be easier to make it porous if I used alcohol or the like...? Well, I will test it out on both cases, I bought more than enough anyway...

I also tried to search for electric steam generators that uses silicon carbide as porous heaters, but I had no sucess until now. If I could find a single article talking about it, I could've spared around 100 brazilian bucks...

By the way, Sucrose is just common sugar, I definitely didn't just waste 60 bucks on buying a chemical grade Sucrose without checking it first. Definitely not, this would be very stupid of me.

Just now, after asking for 298398392398th time, chatgpt suggested me using salt. and then dissolve it in water... And paraffin wax...

I mean, WHY DIDN'T I THINK OF THAT BEFORE?!

I could just have used carbon fiber as the heater...

In any way, here are some of the ratios I will be testing:

In the first try I will go with the gut, I will measure the amount I have for each material first and then adding it to a small pot until it "looks right", then I will measure the materials again so I know how much I used for the mixture.
Then I will try to use a ratio suggested by ChatGPT:
26% of sodium silicate
32% of silicon carbide
21% of graphite
19% of sugar.
Next I will try using a ratio suggested by BingGPT:
20% of sodium silicate
40% of silicon carbide
30% of graphite powder
10% of sugar

Well, it seems my intentions of publishing the project log before testing things out actually worked out very well.

For example, Esteban pointed out that using a silicon carbide heater directly in contact with water is a no-go because it reacts with water at 500ºC.

When it reacts with water, it creates Methane gas and Silicon Dioxide, more known as Silica.

This means that if I were to actually use this thing on a steam generator, I would be talking with the angels, because this is literally a bomb.

This is fine.

In any manner, I will try to use only graphite on the porous heater instead of silicon carbide. Maybe I can make a furnace with the silicon carbide for melting other stuff, but for now...

By the way, I will have to wait another 2 months to be able to buy the carbon fiber to be used as the porous heater...

About the dielectric elastomer:

So, it just came to my attention that I don't need two electrodes.

The idea of a dielectric elastomer is that both electrodes attract each other due to reverse polarities.

However, if you make the electrodes fibers, and all the fibers have the same polarity, they will repel each other. Simulating a contraction.

And since you can easily transmit very high voltages and very low amperages through hundreds of kilometers without much loss.

Plus, you don't need make complex stacks:

However, it also comes with many problems:
How to control contraction? How to predict contraction? How much force can the fibers take before failure and/or fatigue?

Electric motors continue to be the kings of reliability and pretictability.

Off-topic:

Well, like I said before: I need to figure out a way of making the direct contact electric motor.

The problem is that this design is so utterly alien to traditional electric motor design that I don't even know how to start it, I gave the idea of using hypocycloidal drives whre the teeth were the electromagnets. I still think it would be the best option, but I'm simply not qualified enough to figure out how to do it.

For example the only way I was capable of thinking on how to make dual pole teeth would be like this:

Of course, assuming the north and south pole would interact with anything outside of the stator. And then, even if I made all the dozen of teeths on both stator and rotor like this, how I would organize them on the 3 phases of the motor?

So... I think I will be forced to do the conventional way (as shown below), but wobbly just like in the example above:

But I mean, what would stop the rotor from just rotating on the axis instead of wobblling as intended...?

While looking around I found this thing:

Source: https://visforvoltage.org/comment/77084

Way simpler to make and it still has direct contact, both rotor and stator have the same amount of poles...

Another problem on either idea is the phase quantity and sequence of activation. The best I could think of was individually activate and/or reverse each pole with a program and sensors... But the phase and wiring configurations have been used for decades (if not centuries).

Example:

What would be the ideal phase of this thing?

I really need help with this...

I THINK I can calculate somewhat how this direct contact motor could produce both as torque and RPM.

In resume, I will just pretend the electromagnets are piston heads rotating a crankshaft. The stroke of each electromagnet is 0.5mm, and as such, the crankshaft will have that same radius.

Only 2 are working, one attracting and other repelling. For such thing, I will try to use the force of the holding electromagnets for this estimate. As such, there will be 4 electromagnets activating at time.

So, a 50kg electromagnet consumes 10 watts, so 4 of these consumes 40watts. Since stacked electromagnets don't add force, then it would be 100 kg of force in total.

So, accordingly with the torque calculator, I would have 0.5 newton meter (I'm already not liking where this is going). And accordingly to the torque and rpm to horsepower calculator, if it had 3000 rpm, it would output 150 watts of power while only consuming 40 watts.

So I would consume around 3.9 times less power. Not the 100 times less power I was hoping...

For example, if I had an electric motor that outputed 100 horsepower or 75.000 watts, I would consume only 34.4 horsepower or 25.641 watts.
This seems to violate the laws of physics, but do keep in mind that the human body consumes at maximum 300 watts in activities while the Atlas from boston Dynamics consumes 3000 watts.

From all the other crazy ideas, I think this one is the most reliable, safe and understandeable to work with.

(it almost makes me wonder if I even should have attempted on testing the other alterntives and wasted my money...)

On top of that I will still try to figure a way of using electrostatic current (high voltage low amperage) instead of the conventional ones, essentially making every pole a capacitor.

Not because of I want to make something special or anything like that, it is simply because electrostatic electricity goes pretty well in any kind of high resistance material, unlike conventional currents, which needs copper wires.
I'm broke and I can't be buying copper and custom laminations whenever I like it or not. Simple as that.

The only electrostatic motors I could find were these two:

As expected, there isn't much information o the subject, only claims by patent owners.

As far as I could understand, it works just like conventional motors in the sense that it has 3 phases and the rotor has positive and negative poles.

The problem is that I don't know how much torque and rpm it makes per watt of power, they simply don't care about showing these things...

Plus, it seems like a weird option to use copper as the conductive material, specially since it can suffer passivation during prolonged exposure to high voltages...
I guess that since these are PCB plates it is reeeeally cheap to make them.

I think I found them:

Source: https://www.sciencedirect.com/science/article/abs/pii/S0304388620301212

This one is awfully familiar with the first "electrostatic" motor that I've posted up there.

Of course, it is a "Corona Discharge Motor", not electrostatic, if the current is flowing it is not static anymore.

But, as shown in the graphs on the article itself, it has a really low efficiency and a really low power usage.
In fact, it only has a few miliwatts of power.

This guy made and tested his corona discharge electric motor, and the results really meet up.

Project Log 78: The Quest for the Universal Fuel Engine

01/26/2024 at 12:03 • 9 comments

Friday, 26/01/2024, 08:43

Well, since I bought my power source from Aliexpress, the goddang thing will take 75 days (and some times, more), so I have a plenty of time doing a whole of nothing involving this project.

You know what? I'm getting a little bit pissed off with myself.

I keep repeating myself over and over with "let's make a turbine, no, let's make a stirling engine, no, let's make a fuel cell, no, let's make a plastic piston engine, no-"

For f-ck sake, I should just shut up and just do something instead of listing 12932893282389 options that I will never use.

... Well, it would help a whole lot if I had any money to begin with...

(this is my hobby, I do it for fun, I'm having a lot of fun)

Let's talk about energy sources.

What I mean by "universal fuel engine" is that there are multifuel engines that can work with multiple types of fuel, but a lot of them have a small range of fuels.

Of course, you probably don't really need a universal fuel engine, but since I'm broke, the most probable fuel that I will find is grass and wood.

You can't put grass and wood in a turbine engine, neither a piston engine.

Asking to ChatGPT and BingGPT, steam turbine engines can convert fuel into heat, and thus steam with an incredible efficiency, around 80% or even more.

Of course, this is not a surprise if you ever saw anything about stationary energy production, like one of those giant turbine geneartors.

The bigger the blades, the more efficient they are, not to mention that the whole facility is specially built in order to make the finest control possible on fuel, fuel burn and heat exchange.

Of course, the compromise is size.

Not an issue for a energy generation facility, an issue if you want something energy dense, portable and efficient.

These madlads are building a monstertruck motorcycle, and the engine they are using (as shown in the thumbnail) has 150 horsepower, fits in a backpack and could easily power an exoskeleton.

The issues are:

It can only use a single type of fuel.
The generators are many times heavier and bigger than the combustion engine.
Low efficiency, around 30% (not low for combustion piston engines).

Of course, I did find some interesting articles about ultra high speed alternators that could possibly solve the issue of generator size and weight.

(this is a conventional 10 kilowatt AC dynamo generator and it "just" weights half a ton)

The articles in question are the following:

Of course, these are really small energy outputs, but look at the size of said generators, one of them is as small as a match head.

This means that it would be easier to use a gear box that multiplies the rpm instead of torque.

Of course, there are very low rpm geneartors, but these are not really compact. Although, they are very easy to make... At the cost of size.

Universal Fuel cells:

Basically, the first thought I had was to use a universal fuel cell, which was the idea of having a fuel cell that can directly use any kind of hydrocarbon fuel.

Of course, I'm not a company, and my Co2 footprint would be completely meaningless compared to the smallest airplane, lol.

In any manner, these supposedly "universal" fuel cells are called "direct carbon fuel cells", and apparently, the most promising ones (accordingly to the wikipedia article) are the solid oxide fuel cells and the molten carbonate fuel cells.

Both are equally complicated on their own, and both are extremely expensive on their own also. On top of that, information is limited I can barely find anything online.

Another possibility is the use of hydrides.

There are multiple types of hydrides, but the most promising ones are Ammonia-borane and Sodium Borohydride.

When the right conditions are achieved (like heating up ammonia-borane to thousands of degrees), they release hydrogen gas and are further decomposed to boron-nitride and sodium borate respectively.

Like always, information on this fascinating type of technology is scarce and I doubt I would find a way of replicating the results in a DIY way.

Here are some articles that may be interesting to read:

Oh, by the way, "PdCoAg/AC nanoparticles" stands for "palladium-cobalt-silver alloy nanoparticles", I have absolutely no idea how to put my hands on such material.

I said in previous Project Logs, but there are "Catalytic Condensers", which are materials that imitates the actions of catalysts by passing a current through it.

Like always², information on the subject is scarce.
Probably everyone is trying to make a patent and earn a living, it would be nice if scientists didn't need to worry about earning a living with proper support, I'd suppose if I knew what I'm talking about...

Room Temperature Turbine Engines:

Yes, adding to my list of insane ideas that will probably put me in an asylum are turbine engines that are specifically designed to operate at room temperature.

The turbine on turbine engines face temperatures from the combustion chamber up to 1700ºC, in which most common metals would be in liquid state. That is why turbines are made using superalloys such as inconel.

So, in order to make a turbine engine operate at temperatures closer to a turbocharger or even at room temperature, the idea is to cool the air exitting the combustion chambers as much as possible.

One way of achieving this would probably maybe using vacuum ejectors/jet pumps/steam injectors.

The hot air coming out of the thermally insulated combustion chamber would be at 1700ºC and a pressure around 20 MPa (common pressure inside turbine engines), such insane pressure would result in a very high amount of airflow and room temperature.

The ideal gas law tells that the air pressure is proportional to its temperature, so with such gas pressure expanding at high speeds while exchanging its temperature with the surrounding air, it would create a high airflow.

Of course, this would most probably not work.

If it was that easy to make a room temperature turbine engine, it would have already been done.

Another idea was to instead use air flow generated by the combustion chamber to drive a turbine on the outside of the combustion chamber.

Basically, the idea would be to do more or less the same thing with the previous idea, but the entire vacuum ejector would be around the entire assembly and the airflow around the engine would drive a turbine.

Imagine it like a reverse turbofan.

Just putting this here because I think it is interesting:

This is a 60kw microturbine engine with 40% of efficiency.

This one is a 25Kw with an bigger option for 500Kw, it is said to have 85% of efficiency.

Of course, I think it is bullcrap, but in both cases the efficiency must be higher because of the heat exchanger/recuperator.

In both cases it is a design that can fit in a backpack (I think).

I was thinking of using an electromagnetic bearing on the tip with the generator/alternator unit.

Maybe I could make a DIY titanium aluminide turbine blade, BingGPT suggested Haynes alloy HR-120 (33 wt % Fe, 37 wt % Ni and 25 wt % Cr [and maybe a little bit of tungsten]), which seems... Viable to do at a DIY setup.

Oh yeah, I completely forgot that I could "just" make a hero turbine engine. The only problem is injecting fuel on it.

(the one in the right)

Stirling engines:

Stirling engines are the bane of my soul.

They always come up, when I'm trying to find alternative engines, but they usually suck ass.

Not in the sense of efficiency, they usually achieve efficiencies of around 40%, and have almost no moving parts. Of course, the properly made ones, like the ones made by NASA or something.

Most of the time they look like this:

This insane piece of metal can't produce a single horsepower.

In any manner, let's talk about the properly made ones:

Recently, China has launched "the most powerful stirling engine yet that the world has never seen making a breakthrough that will SHOCK the industry", you know, that clickbait trash.

This chonky boy has 2 fricking meters of length and can produce 103 horsepower, it is meant for use in submarines, to turn waste heat into electricity.

And that is a common theme between stirling engine endeavors: they aren't meant to be the main power source, but a recycler of waste energy.

For the life of me, I couldn't find the diagrams, pdfs, articles or anything useful showing how this specific stirling engine works. Which I'm not very surprised, after all, it is a submarine stirling engine, who in their right mind would share this kind of top-secret machine?

However, trying to find how this ting works, I came across two types of stirling engines that I liked very much:

Free piston stirling engines

(I searched for 1 kilowatt stirling engines like the one in the pic, they are 45cm in height and 30cm in diameter, I need at least 30 of these, lol)

... And thermoacoustic stirling engines

Source: https://www.researchgate.net/publication/301791408_Stirling_cycle_engines_for_recovering_low_and_moderate_temperature_heat_A_review

Thermoacoustic stirling engines have absolutely no moving parts, and they can be used on a compound configuration, basically, mixing all kinds of energy generation systems.

For example, you can mix magnetohydrodynamic generators and free piston stirling engines on the same engine. Maybe even piezoelectric buzzers to convert the vibration into electricity.

Source: https://advanceseng.com/thermoacoustic-stirling-power-generation-lng-cold-energ-low-temperature-waste-heat/

Source: https://www.researchgate.net/publication/281593423_Analytical_study_of_thermoacoustic_MHD_generator

Source: https://www.sciencedirect.com/science/article/abs/pii/S0196890422002990

There is also the https://technology.nasa.gov/patent/LEW-TOPS-80 Stirling patent, but I can't find the schematics anywhere.

In any manner, I decided that I will stick to the Compound Thermoacoustic Stirling engine for the Universal Fuel Engine.

The only issue is that I don't know how compact this would be.

I remember seeing a few kilowatt thermoacoustic stirling generator that had 0.3 meters of length (30cm), it was multistaged and stackeable, but I couldn't find the gooddang picture again.

I searched for the picture for 5 hours straight and I couldn't find it, I thought I saved it on the thermoacoustic paste...

I just said this and I found it:

Source: https://www.researchgate.net/publication/276902981_Development_of_a_3kW_double-acting_thermoacoustic_Stirling_electric_generator

It is a 3 kilowatt generator, so I would need 10 of these stacked to a mere 40 horsepower generator.

It is also stated in the article itself that it only has an efficiency of 16%...

-_-

While searching for the subject I came across this two way-one way turbine, whenever direction the pulse from the burning element.

Source: https://journal.hep.com.cn/fie/EN/10.1007/s11708-020-0702-3

But I doubt I will be able to do it, my intention is exactly avoiding moving parts.

I didn't even read the articles about thermoacoustic stirling engines so I barely know those things work...

However, this did gave me an idea. I think I already talked about something like it before.

The idea would be to make a toroidal tube and add cylinders to it, they would be piston heads and this turbine would be inside the toroidal tube.

half of the cylinders/pistons would detonate and the other half would compress the other pistons, just like a liquid piston engine or a pulsometer engine.

The only problem is that I don't know how well it would work or how well

Thermoelectric Generators:

So, afterEsteban's comments in this project log, it made me realize that maybe thermoelectric generators are a more realistic option, even with its downsides.

Just like I said in Project Log 74, the thermoelectric generator could be 3D printed using Sodium Silicate, copper oxide and graphite.

You know the drill, mix this (thermoelectirc generator configuration:

And this (heat exchanger with a turbocharger):

With the air compressor feeding air like a blast furnace:

And finally, I do think it would be interesting to use the vacuum ejector idea from the "room temperature turbine" in order to use the exhaust for air flow generation, and thus, making a cooler with no moving parts. Increasing the heat difference between the cold part and the hot part.

Another point I was thinking on making:

I think that I could use a mold for making the DIY thermoelectric generator instead of building a paste 3D printer, like one of those silk screen printing plates.

Basically, 3D printing or paying someone to 3D print a mold for each layer, since these tecnically are two "E"s of each material type connected to each other in someway.

Plus, if I want to make a blast furnace-style thermoelectric generator, I would need to mix not just sodium silicate, but also refractory cement. Because blast furnaces can reach temperatures up to 1800 ºC.

The only problem is that I don't know how to make the hot air to reach all the thermoelectric cells, since the temperature lowers the further it goes away from the source.

I swear to god, I may be talking big about all these exotic energy generators, but I bet I will just switch to a simple combustion engine and shut up myself on the future.

Off-topic:

I was looking in the internet and there is a type of propulsion system called Arcjet Rocket, which has an exhaust velocity of 16 kilometers per second, accordingly to the rocket calculator, if the mass was 100kg and the final mass of 99.882kg ( 10 liters of compressed air at 10 bar weights 0.118, which would be ejected into an arcjet for extra thrust), it would accelerate the mass to 60km/h.

However, it is not that simple. Some arcjet rockets use hydrazine (super cancerous chemical) and I can't find an specific value of how many watts it consumes per thrust, but it seems to be highly dependent on the gas used.

I remember seeing one source affirming it consumed 1 kilowatt per 0.1 newtons of thrust, this would be around 100 kilowatts per kilogram of thrust. lol

Well, this paper had some graphs that would say that it more or less consumed around 90 volts and 10 amps and generated almost 180 newtons of thrust, this would be around more or less 50 watts per kilogram of thrust, which is more than electric motors.

Project Log 77: The quest for the Miliwatt Actuator.

01/21/2024 at 12:45 • 1 comment

21/01/2024, 08:22, Sunday.

I'm quite stoopid, I already said I gave up on the project, but I can't, for the life of me, just give up.

And besides, like I said on previous logs: looking for artificial muscles/soft actuators is my hobby now.

What I need to look for?

In any manner, using electric motors and combustion engines is a no-go for robotics, since a human speed exosuit/mech/robot would need megawatts of power to lift tons of weight, the only way I can make these viable is to reduce the consumption for at least 100 times.

And for that, I need to find a good actuator option that has a power-consumption below 1 watt in order to make this thing viable, more precisely, around Miliwatts of power. Which is 0.001 watts.

Electric motors are complex machines, but are very reliable and precise, I would love to "simply" make an electric motor that uses 0.3 watts (or less) per kilogram of force at 40m/s of speed... But it is not that simple.

One way I could think of was to reduce the air gap between the stator and the rotor to micrometer or nanometer distances. After all, the smaller the distance between electromagnets, the stronger the electromagnetic field.

The issue is: the stronger the electromagnetic field, the stronger the eddy current, the reluctance and a myriad of different things.

Every type of electric motor is an ecosystem on its own, and in order to figure it out, I would need to understand the fundamentals of electric motors.

With that in mind, I found myself looking at a concept called "zero air gap permanent magnetic machines" with this paper: https://digital.wpi.edu/pdfviewer/9p2909417

One of the suggestions is using ferrofluids to "close" the gap, but as far as I could see it, it actually had some substantial effects, like almost doubling the torque of the electric motor.

But still nothing close to miliwatts...

It makes me question if the micro/nanometer gap would even make any difference at all...

Ah, by the way, the article talks about a company specialized in super tight tolerances and super dense brushless motors called "Thin Gap", which uses a slotless winding that I couldn't quite grasp how it is done.

This one is said to have 100 kilowatts of power.

The paper I linked above kinda explained how these are done, but I don't think I quite grasped it yet.

In any manner, I can't find anything on the subject as much as I like, so I don't think I will have any luck trying to DIY my way into this type of exotic BLDC motor (and unfortunately, I would love to)...

I also searched for other articles:

If I didn't read it incorrectly, you can achieve up to 4 times more torque with the same amount of energy, which would reduce the power consumption from 3 megawatts to "just" 750 kilowatts, which is like, 1000 horsepower to lift 1 ton of weight.

Very interesting results, but nothing close to miliwatts...

They achieved that (if I'm not mistaken) by making the electric motor's rotor enccentric, so it physically touches the stator's teeth, like a radial piston engine, except with electromagnets instead.

So, if they literally physically touch and can only multiply the torque by 4 to 5 times, then this is probably a dead end.

The only reason the rotor strength doesn't increase even more is due to the fact that it is eccentric, only a small part of the rotor is touching. Only 2 teeths out of 17 teeths are in direct contact with the stator, so I could imagine a maximum increase of 8.5 in torque if full contact was possible. And it would probably be possible by stacking the eccentric just like radial engines did:

Assuming a gross approximation of simply taking 3000 Nm (to lift 1 ton at 30cm distance) and divide it by 4 and then further by 8.5 it would reduce the power consumption to 2300 watts from 78,000. Resulting in a total of 92,400 watts, or 123 horsepower for a full mech/exosuit.

This is a reduction of 32 times, not 100, but it seems viable to me.

Well, I do wonder how long these eccentric direct contact electirc motors would last, even with proper lubrication...

One could shape them like gears... Which would be interesting...

Hum... This makes me remember of this type of pump:

Maybe an hybrid of both could be made for a hydraulic pump?

Oh yeah, I think this is relevant, but I don't know how to explain in a quick way. But basically:

The directly-tounching electromagnetic teeth of the electric motor work more or less the same way the holding electromagnets.

These use very low energy, around 14 watts to hold 100 kilograms (0.14 watts per kg), and the direct-contact electric motor would do the same. But like I said: it uses this energy to hold such weight, not to move it.

An electric motor with such design would need to take into consideration the distance between the teeth of the gear I showed before, since some teeth would need to be electromagnetically attracted to rotate.
A mere distance of 1mm distance is enough to reduce the electromagnetic field for for more than half of its power, so the teeth's clearance must be very tight and require a very well thought design and control in order to diminish the waste of energy in other distances. Which could make this very expensive to make this custom motor from scratch...

Yes, I did say that electric motors are expensive, copper is also expensive and so on. But honestly, electric motors are way more understood and widely used than other options. It is way more practical to tell someone to make an electric motor with better precision than to go into uncharted territory and face thousands of different issues that no one has an answer for.

But an electric motor? Ask a professional why the machine is acting in a certain way and they will have an answer.

In either way, I will """just""" need 1 electric motor per mech/suit in order to drive a hydraulic pump.

I will try to study and test every option before I finally come to a conclusion.

Steam-driven Actuators:

The first thing that comes to mind (besides electric motors) is the steam powered actuators.

There are a couple of ways of achieving this, but first things first:

1 liter of water can be turned in 1600 liters of steam.
Since steam is compressible, these 1600 liters must divided by the amount of pressure that will be used.
The faster you need to heat the water the more energy you need.
In 1 Hour takes around 750 watts.
In 1 Minute takes around 43,000 watts.
The bigger the pressure, the higher the temperature to turn water into steam. Around 5 bars, the amount is negligeable.
Electric to thermal conversion is 99%, the thermic energy used to transform water into steam is also 99% efficient.
Using steam alone to actuate things has maximum efficiency of 30% to 40%.
Steam powered actuators can lift at least 1000 times its own weight.

With this alone, steam doesn't seem much attractive, but you need to remember that water isn't the only thing that can be turned into steam, neither that using a simple resistor is the only way of heating it up.

Liquids like ethanol, ether and chloroform have boiling points around 30ºC and 60ºC. Which can be used, chloroform is the only one not flammable, buuuuut... It is toxic to humans.

The only liquid that the fricking half-useless BingGPT suggested that isn't flammable nor toxic is Novec 649, a fire extinguisher and coolant that has a boiling point of 49ºC. So it would consume half of the wattage's water.

In any manner, I found this article:

"Preparation of Linear Actuators Based on Polyvinyl Alcohol Hydrogels Activated by AC Voltage"

Source: https://www.mdpi.com/2073-4360/15/12/2739#

It uses PVA hydrogel with borax (slightly conductive) and distilled water, however, the current used to heat it isn't DC, it is AC at 220V and 500 Hz with an efficiency in the 0.8%'s.

The interesting part though, is that it uses only 0.04 watts of power, around 40 miliwatts and it takes around 1 to 2 seconds for full contraction.

And besides, I don't even know if it would be better to have a central "steam converter" using hydrogel fibers (as in the article) or resistive sponges to make steam and use a Steam Injector or use the artificial muscles to rotate a water pump.

Let me explain:

Steam injectors are water pumps (or steam pumps/jet pumps) with 95% of efficiency in pumping, while the artificial muscle driven pump (imagine a piston engine, but replace the pistons with muscles) would have around 40% of efficiency (and yes, it would still use miliwatts of power even while using more than twice the power).

The steam injector pump rubs me the wrong way because it is fricking steam, it is basically a bomb. Yes, I could limit it to 5 bars (around two times a pressure cooker takes), but even so, it would still be dangerous in some level, specially with the amount of steam required.

... Maybe I'm being too overly cautious with this, fire extinguisher tanks are meant for 2 MPa, around four times more pressure than I intend on using.
I could use discarded ones for the boiler.

BingGPT said I would need around 10 bar of pressure in order to pump a fluid to 5 bar of pressure in a Steam Injector/Jet Pump system.

I know that it sounds strange to use an artificial muscle to drive a pump, but hydraulics have a lot of advantages, for example:

I don't know how to make a compliant hydraulic actuator, but hot dang, is this fast (and strong, in the description it says it has a force of 10,000 Newtons, or 1 ton).

Accordingly to certain articles, they use a miniature hydraulic accumulator for passive compliance. The only issue I have with it is that they change the stiffness of the compliance by changing the pressure in the accumulator's bag/bladder. Not a big problem of anything like that, I just don't like the extra amount of complexity.

One could simply add a spring accumulator and adjust the stiffness by compressing it more or less, you know, by just rotating a nut or something among the lines.

This paper suggests using magnetic shape memory alloy, but one could also use magnetorheological/electrorheological fluids that changes viscosity with magnetic/electrical forces being applied to it.

This could mean that:

Water could be turned into steam with the same wattage using the same hydrogel borax method.
The use of a highly porous heating element could highly improve the water to steam conversion.

But again, the only way to be certain is to test things out.
But again², I'm broke.

Dielectric Elastomer Actuators:

Well, if you read the previous project log, you know the drill.

Dielectric Elastomer Actuators have efficiencies above 90%.
They can be 3D printed and/or 2D printed.
They have multiple types of stacks that highly impact its contraction.
They need really high voltage and high low amperages, around 5000 Volts and 0.00025 amps.
They work best with really thin layers and really thin electrodes, which can be hard to make.
Most dielectric elastomers actuators can lift around 50 to 100 times its own weight, which is a problem, but it can be a result of its implementation. The use of fibers can solve such issue.
Bubbles and material quality can heavily influence the efficiency and performance of the actuator.
Not many examples out there, this can mean lower endurance.

Source: https://www.pnas.org/doi/full/10.1073/pnas.1815053116

I thought on using a 3D printer with a syringe needle as the extruder in order to make a continuous 3D printed Dielectric Elastomer Actuator stacked in the same manner as in the image.

However, like I said, the thickness of the layers is imperative, and I really don't think I can achieve such insane precision with a DIY 3D printer.

One of the possible methods is using Airbrushers and mixing silicone rubber with alcohol (or acrylic with acetone), which makes the silicone rubber less viscous and allowing for an even thinner layer.
Heating the bed would also allow for faster curing time.

But I would need, like, one of those belt 3D printers.

One of my ideas for this actuator was to use microfibers by extruding conductive polymer through syringes and making micro-wires or even nanowires. The wires would be the electrodes and the dielectric layer would be over them, the positive side would be covered in Polyvinyl Alcohol and the negative side covered in Polyvinyl Acetate.

This way one could use water to dissolve the dielectric layer of the positive electrodes for power connection while using acetone to dissolve the Polyvinyl Acetate covered negative electrodes.

Well, the idea is that both fibers would attract each other and twist in someway, but I have absolutely no idea if it would happen.

(something like this)

In any case, I'm at a loss on how I should use the dielectric elastomers.

Should I use them directly into the suit? Should I use them in an piston engine configuration where the pistons are pulled by the artificial muscles?

I feel like the motor thingie would be easier to produce, no? I would need to make the same exact actuator and glue them together in a radial configuration.
It would spin at a predictable speed, with a known force and a known stroke. Either to drive a hydraulic pump or an electric motor (I like the electric transmission idea, but you know, it is very expensive).

While the direct attachment would need to be considered, the fibers need to be glued to the bones (that could unglue at any moment) and so on.
I do like the idea of direct connection, but the constant exposure to outside elements (even with fabric layers of protection) could damage the already fragile fibers.
The hydraulic pulling actuators would be made of recycled, more resistant materials like PVC, Polyethylene and the likes of it.

Another argument that could be used for the use of artificial muscle driven pump (and valves) is the fact that you can't make precise movements with the Dielectric Elastomer Actuators (DEA), like the Pneumatic Artificial Muscles, it is either on or off precisely because of the way it works. If you apply less voltage in order to parcially contract the DEA muscles, you would also use the parcial strength.
The strength applied by the DEA is equal to its electrical force, so you can't position it precisely, unlikely electric motors and hydraulic actuators which can tweak with its rpm and torque at will.

The only I could think of circumventing this (besides individually activating fibers, which is too labour intensive) is by rapidly turning it on and off before it can actually fully contract.

But this would need an unknown amount of hertz and a encoder on the axis of the artificial skeleton (either of an exoskeleton or mech) for full position control.

But again, the only way to be certain is to test things out.
But again², I'm broke.

Dielectric Pump:

Speaking of dielectrics, let's talk about dielectric pumps.

They also use high voltage low amperage just like dielectric elastomers, requiring milia
They can also be 3D printed without the precise requirements of Dielectric Elastomers Actuators.
I couldn't find the efficiency of such pump, but it doesn't matter.
Its performance depends on the number of electrodes, length of the fiber pump and dielectric properties of the material.
The fiber pump in the article uses an specific chemical liquid that forces passivation of the copper wires after 3-5 days of continuous use. Passivation occurs when a high voltage low amperage current passes through a metal material, which forces an oxide layer on its surface in the presence of certain materials.

Source: https://www.science.org/stoken/author-tokens/ST-1105/full

The paper of this fiber pump uses an specific dielectric liquid that costs thousands of dollars per liter, however, one could replace it with other liquids, such as oils and deionized water.

It is meant for microfluidics, meaning that using it for hydraulics that needs dozens of liters per minute and several atmospheres of pressure will require way more voltage.

Another concern I have is Passivation.
Although the paper uses a very specific liquid, the passivation of copper (or metals in general) can occur at myriad of different conditions, even by exposing it to air.

Passivation generates a oxide layer on the material, in other applications it is good for corrosion protection, but in this case, it can literally make a insulation layer between the metal connections of the conductive materials.

What a pain would be if every X amount of time the thing simply stops working because an oxide layer was created in every possible connection, essentially killing the electronics?

The only solution I can think of is using conductive polymers (like silicone rubber mixed with carbon powder) in the place of copper on the system that converts the current to very high voltage very low current.
And the only system that I can think of is a transformer, and I'm not very sure about it either.

I was thinking of making a fiber pump for every individual actuator, which seemed like a good idea, but I'm wondering if it really is.

Each fiber pump has to be at least 5 meters long and have multiple tubes, I thought on wrapping them around each actuator, but taking into consideration the absurd amount of actuators required and the small space they will be fitted in, the pumps would probably be rubbing on each other during activities, and thus, slowly being degraded.

A central fiber pump would be a better option, I suppose, but I find hard to imagine would I would fit a 5 meter long fiber pump with a thickness of a human body inside a mech.

But again, the only way to be certain is to test things out.

But again², I'm broke.

Testing things out:

I'm going to try and buy the equipment for this endeavor during next months, but I wish I could already test everything.

I bought the adjustable power source for around 40 dollars, which is around 200 reais + import taxes.

Here is the pic:

The first annoyance is that the high voltage converter only works with 400 kilovolts and above, I just need 3 kilovolts, specifically because of dielectric breakdown. The materials that I have available aren't the best, neither the most expensive, unlike the ones used on the dielectric elastomer actuators papers.

There are adjustable kilovolt power sources, but they cost thousands of brazilian bucks.

I will, unfortunately, be forced to make my own.

On top of that, I will be forced to use a faraday cage, because once I saw a guy make a homemade ionocraft while using these High Voltage generators and all of the electronics on his house simply fried because it was liek a continuous EMP.

I'm 2 minutes in and I already want to give up.

Can someone do it for me, please? y-y

Project Log 76: Mechs are not viable... In certain ways.

01/17/2024 at 00:23 • 2 comments

16/01/2024, Tuesday, 20:47

Converting the 40cm/s of linear speed with the 1/10 mechanical disadvantage of the human body in a forearm with 30cm of length, the rpm of the arm would reach 250 RPM, or 4 meters per second of linear speed (I heard that a punch can reach 45 km per hour of linear speed).

Now, if we input these numbers in an mech arm with 60 cm of length (since the entire mech is twice the size of an average human), and we maintain the linear speed of 4 meters per second, which would give 130 rpm, we would need 6000 newton-meters to lift 1000kg.
By the way, it doesn't matter if the load is put in a difference distance, if it is going to lift 1000kg on the tip of 60cm, the lever arm length won't change the final wattage, no matter how you tweak the rpm and torque, you can't scape the laws of physics.

And, if you input the numbers in a torque to horsepower calculator, it gives you 81,686 watts, or 109 horsepower.

If we take the more "whatever" approach and simply say that the arm and shoulder are the same, the torso uses the same amount of energy and the legs use 3 times more, it would still give 545 horsepower, or 408,750 watts.

This is basically half a megawatt.

If we take a somewhat precise approach and simply multiply the other limbs force requirement by 3, the numbers go bonkers.

109 hp to the forearm + (109x3) to the shoulder, ((109x3)x3) to the torso, (((109x3)x3)x3) to the legs, which would give:

4360 horsepower or 3,270,000 watts of power.

You would need 3 megawatts of power to a simple mech that moves at same speed as a human being.

It is not "super speed", just "super strength", you would still run miserable 10 km/h with the mech (average human running speed), maybe 20km/h due to the double size of the limbs (a mech even slower than this could be viable, but what would be the point?)

And a exosuit with 100kg of lifting capacity would use 145 horsepower/109,000 watts, not much lower than the mech (a exosuit even slower than this could be viable, but what would be the point?²).

Plus, I'm calculating only a 100% efficient machine, which is not possible. With inneficiencies, the energy consumption would increase even more.

In any manner:

In the end, it is indeed it is 81.6 watts per kilogram of weight at 4 meters per second of speed. A simply legged exosuit would consume around 8 kilowatts/10 horsepower for every 100kg of weight being lifted at 8 meters per second, half at 4 meters per second.. Not great, not bad, I'd rather say.

(by the way, the lightest mech in Armored Core's weight around 35 tons)

But, as a consolation prize, maybe walkers will be viable, since they don't need to carry the extra weight the arms and torso would need to carry. xD

Maybe some day I actually try to make a walker-forklift hybrid, but who knows...

Oh, by the way², you would spend 35 to 40 horsepower for every 100 kilograms if you were using drone motors to lift your body weight, so you could jump around like you are in zero gravity (or with super human strength, lol).

This would make 260 watts per kilogram, but you would need 4 times more power to to make things move 4 meters a second. Dunno if it would make sense to insert a lot of propellers in a humanoid mech.

Well, one thing I noticed: the Boston Dynamics robot Atlas consumes around 3000 watts-hour during exercises.

Since the robot carries a 3000 watt-hour battery and can only do it for 1 hour, then I'm assuming it uses around 3000 watts per hour. It can move at around 2.5 meters per second and carry maximum 14 kg of load while the robot itself can weight around 90kg to 195kg.

It is hard to find a definitive answer, I can only find scattered information through news articles about the subject. The website from boston dynamics also doesn't give clear information on the subject either.

https://bostondynamics.com/atlas/

On top of that, there are other versions of Atlas, some weight almost 200kg, the shorty white one weights around 90kg.

In either case, I do think it to be strange for this robot to be able to only consume 3000 watts while carrying weight and it might indicate that in fact I'm calculating something wrong.

But taking the 81.686 watts I calculated before and take the force and speed out of it, it makes a little more sense. The robot carries 10 times less weight and at 1.6 less speed, so in total it would be 5105 watts or 6.8 horsepower.

However, the robot is said to only consume 3000 watts or 4 horsepower without the stewart platform skeleton where the load is proportionally divided by all joints.

Of course, there can be a lot of information that is not specified, including the way the robot moves, the way it distribute its loads and so on.
Not to mention that the marketing department simply took approximated values and putted them into the website.
After all, a stepper motor may have a rated speed and torque, but its actual capabilities can only be shown into a graph.

But... I think it is realistic to assume that the estimate I've made is correct.

Project Log 75: Tech Tree for Mechs².

12/07/2023 at 10:15 • 6 comments

It happens that I wrote so much on the first Project Log 74: Tech Tree for Mechs¹. that the hackaday Website started deleting older text. :|

I contacted the Hackaday email asking if it was possible to check older edits so I can copy the part that was deleted (I received an automatic email response saying they would take like a week to answer).

... And no, I don't write my project logs in a other documents. Yes, I'm that stupid.

... And that is why I completely lost whatever it was deleted. Forever. :|

-----------------------------------------------------------------------------------------------------------------------------------------------

I literally cannot write a single new phrase on the previous project log, but basically, I think it would be worth it making the electromagnetic artificial muscle I suggested making with the nanometer 3D printer with actually the airbrush 3D printer.

I know that it would take ages 3D printing and calibrating properly, but it would still be possible. I just don't know if it would be viable or practical, still, you would face the same problems relating to 3D printing electronics with resin and metal powder.

Well, I'm still not actually giving up on the mech idea, but I'm simply have a lot of difficulty find solutions (cheap and simple solutions) for the actuator problem.

Like I said in the previous project log: I settled on at least trying to find a way of making a solenoid pump or something that can be used as a pump and doesn't need electric motors, combustion engines nor piezoelectrics.

Electric motors are expensive and need really big batteries, combustion engines are low efficiency, expensive, heavy and need solenoid valves, piezoelectrics can't be homemade, aren't efficient and neither can pump massive volumes.

I mentioned the possibility of using Nitinol Shape Memory Alloys, but those have efficiencies below 20% and cost 500 dollars per kilogram.

By the way, while asking my trillion of random questions over and over again, ChatGPT said that the conversion of electricity into heat (using a heater like Nichrome or other types) is almost 99% efficient, and that the conversion of heat into steam using this method is almost 99% also (I searched online and it seems to check out).
So, there is also the option of using steam to pump the fluid or something else. You could use steam instead of pneumatics or hydraulics, you could use it to make a steam engines ( that are around 40% efficient) and so on (turbine engines sit around 65% to 90%). I also believe that steam powered artificial muscles would be as efficient as pneumatic ones (30% of efficiency or less) because they are essentially the same thing, but using different fluids.

Source: https://www.science.org/doi/10.1126/scirobotics.aaz4239
It is a unthetered artificial muscle in which induction heaters are used to heat iron oxide nano-particles in order to turn water into steam, making the muscle actuate. It is less efficient than what I'm suggesting.

But I don't know which is the best method, and to be honest, I don't feel comfortable carrying an electric steam boiler on something that can simply fall on the ground and break what is basically a bomb.

The few positives that I can think of would be the speed of actuation, compared to hydraulics and electric motors, it is hard something as fast as a pneumatic actuator consuming the same amount of energy.

Not to mention that you wouldn't need the power of a turbine engine to compress thousands of liters of air.

... But it is also not that simple.

I would need to calculate how many liters of water you would need for a given pressure and flow of steam, which, as far as I could calculate in the past, it ins't that hard, but it isn't that easy either. It would entirely depend on the full system.

1 liter of water produces 1600 liters of steam.

Maybe it could be useful for an ornithopter...

Steam powered artificial muscles:

The same problem of pneumatic and thermal artificial muscles arise: which is how to control its actuation properly.

I found a few suggestions that have its own pros and cons:

Completely activate single strands based on how much weight you want to lift and how far you want to lift.
This one I accidentaly found out about when looking for Battlemech, ironically.
The description is that these are high voltage activated electric artificial muscles that activate independent strands.

Buuut this idea could really be useful for thermally activated artificial muscles, like the Shape Memory Alloys and that carbon-fiber-silicon rubber one I showed on the previous project log.

Another idea for thermal actuators is divide the actuators in sections, so you could progressively contract certain parts of the artificial muscle fiber. But it would be a pain in the ass to wire everything.

I also gave the idea of simply spraying cold water at the rate parallel to the thermal muscle contraction in order to make it contract in a certain distance.
But how to control the force?

Another option would be to "simply" turn the appropriated amount of water into steam required for a given action.
... Which is really not that simple. And just like I calculated in other previous project logs, the faster you want to turn water into steam, the more power you would need. To the point a single small muscle would require 2000 watts of power to contract in half a second.

However, a possible way of combating this would be to have multiple independent and interconnected steam generators throughout the body of the mechsuit/exosuit.
This way if one steam generator is not enough to supply a given action, others will open their own valves and help with the extra boost.
But, as you can guess, this option still requires a lot of solenoid valves and careful control, which means proper programming, which is not my forte.
And yet, I like the idea of multiple small steam generators instead of a single big one. If one of these were to blow up, the detonation would be smaller and less dangerous.

Another obvious option would be to copy the already existing pneumatic controls, but use it for steam.
Normally, if an actuator (like an arm with pneumatic artificial muscles) wants to make a precise movement, opposing actuators would be opening and closing in order to reach that position. A biceps can't move if the triceps is already pulling it back, which would lock the arm in the desired place.
This need a fine, precise and very expensive kind of sensors, progressive valves and it is really inefficient since half the effort of the arm will be spent counter acting the arm.
This option is not very good in my opinion.

There is still the simpler option of simply making steam with the electric method and rotating a steam turbine that would rotate an hydraulic pump.
But, as you can guess, this method wouldn't be so simple. And steam turbines are heavy and expensive.
However, they seem to be very versatile, since this one here (accordingly to the random website I found) could output a power between 100 to 3000 kilowatts of power (which is absolutely insane).

By the way, the bigger the steam turbine, the more efficient it is and the slower it needs to spin (just like helicopter/turbofan blades), so, depending on the amount of horsepower/watts I would require for the Mechsuit/Exosuit, I would need a custombuilt steam turbine engine.

But even then, if such an insane idea of using a steam turbine engine on the backpack of a Mechsuit/Exosuit works out somehow, you would still find the issues regarding common hydraulic systems: solenoid valves, control feedback and so on.

The ideal manner of pumping water using steam would be using steam itself without any mechanical means.
The best two results I got were Vacuum Ejectors, buuut I don't know how to make it to pump water and refill the steam boiler at same time using a Steam Injector.
In normal occasions you would either use one or the another.

The vacuum ejector uses a higher pressure fluid to create a vacuum and mix with another fluid in order to create a very efficient mixer or a high airflow thingie.

I couldn't find anywhere the efficiency of steam ejector/vacuum pumps.

I found a source that claims it to be 90%, but ChatGPT/BingGPT says it has around 10-40%.
I asked an engineer in a discord group and he said that the efficiency depends on the type of fluid being worked. air on air = 90%, air on liquid = 60%, liquid on liquid = 30%, but in the source I talked, the pressure being ejected is at 1.1 bar since this is a mixer, not a pump, meaning that proper pumping has to be properly tested.

A steam injector on another hand, uses the higher pressure steam from the boiler to pump water back into the boiler.

Since this would be a new type of pump, I can't tell how efficient such pump would be...

I did found out about pistonless pumps, which operate in a different principle and are quite interesting as far as I could see.
Of course, just like any other steam mechanism, it is way more complex when you want it to do something you want...

Savery Pistonless pumps are simple: fill in a tank with steam directly connected to water, the steam will expand and push the water, then you let the steam get cold and create a vacuum, pulling the water. Rinse and repeat.

They even used a similar approach for a rocket engine in order to save weight and money instead of using turbopumps.

Source: https://arc.aiaa.org/doi/10.2514/6.2014-3784

For last, there is the Pulsometer pump that also works with the same principle as the others, but with a different structure.

If I'm not understanding this incorrectly: it works the same way as the others, but it has extra chambers, allowing for a continuous operation unlike the Savery's one, which needs to wait the steam to cool down.

Well, if these are the equivalent to a piston pump, I wonder what would be the equivalent to a centrifugal pump...

... But the problem comes back to the efficiency problem: expanding steam is just like pneumatics... And pneumatics aren't efficient.

A piston steam engine has 40% efficiency, and this is basically a piston steam engine, but without the pistons... So... It is safe to assume comparable efficiencies.

Well, I forgot to talk about Dielectric Elastomer Actuators.

The video explains it very well, but basically, the non-conductive elastic medium is sandwiched between two conductive layers/electrodes, once static electricity is passed through it, the two layers attract each other, simulating a contraction.

The funny thing is that this is actually a shape-changing capacitor.

Capacitors have three layers: two electrodes and a dielectric (non-conductive) layer.
A bunch of electrons are concentrated on the electrodes and since they have a dielectric (non-conductive) space between then, it keeps them in place by the electromagnetic attraction, once the two sides are connected, the electrons instantly jump all at once to the other side.

(By the way, for the little I think I know, there aren't positively charged electrons? The only thing that can be called "positively charged" is something lacking electrons, no? I'm confuser)

In anyway, I just didn't give much credit to this type of actuator simply because I don't know what is their efficiency and how precisely are these made.

Some articles say Dielectric Elastomers have more than 80% of efficiency, in others it is said they have less than 20% of efficiency.
They normally have a really, really small stroke, less than 10%.

On top of that, there are numerous and numerous types of Dielectric Elastomers.

Some are based on acrylates, some are based on silicon rubber or are fluid assisted, some use carbon nanotube electrodes, others simply uses graphite powder on its place.

And I can't find enough information properly comparing each type's performance and efficiency, the information is all over the place, scarce and imprecise.
I would need to build every single type and personaly test every single one, but some need such complex polymers that I would need to directly contact some chemical factories for custom orders on the materials.

Example:

Source: https://www.mse.ncsu.edu/2016/11/new-bottlebrush-electroactive-polymers-make-dielectric-elastomers-increasingly-viable-for-use-in-devices/

This dielectric elastomer is a modified silicon rubber to be used specifically for this porpuse, it can have a stroke of 300%.

I couldn't find what the hell is a "bottlebrush polymer", but after searching a little bit on google, I think I found something that is probably the same thing, which is a normal silicon rubber being modified by at least 3 compounds:

PDMS Monomer: Monomethacryloxypropyl terminated polydimethylsiloxane.
Crosslinker: Methacryloxypropyl terminated polydimethylsiloxane.
Initiator: hermal-initiator: 2,2′-Azobis(2-methylpropionitrile).

To me, these three sound like old eldritch god forbidden names.

Not to mention the myriad ways you could stack these dielectric elastomers for different porpuses.

Also, as you can see, the dielectric elastomers are a reversedely actuated artificial muscles, meaning that they relax when activated and contract when disactivated.
After all, the two electrodes are attracted when charged, not the opposite.

Of course, it depends on the type of stack.

In any manner, I am divided between the vertically stacked and the spiralled/cylindrically stacked, simply because I could add milk-graphene to the flexible electrodes and absurdly increase the strength of the silicone rubber, while that is not an option for the vertically stacked...

(I think this is a good way of making the cylindrically stacked dielectric elastomer:you restrain one of the parts and it curves, it would curve in one direction, this one shows a different set of fibers that work like Mckibben which would coil on itself [supposedly]).

The spirally stacked would have its electrodes connected end to end while the vertically stacked would be divided with soft silicone in between...

Assuming that I wouldn't do the same thing as the electromagnet idea where the conductive connecting parts would be on the outside.

On another note, I could see the Spiralled stacked being easily mass produced, you would only need a conveyor belt and three airbrushers making three continuous layers of dieletric elastomer that would be solid by the end of the belt, which would be automatically spiralled and twisted, just like a rope.

But I don't know how the vertically stacked could be mass produced, I can imagine it being 3D printed with specialized conveyor 3D printers, but not as fast as in the gif.

However, I do think that this has the same problem as the stacked electromagnetic artificial muscles that I suggested previously: stacking the dielectric elastomers won't stack their strength, forcing you to make multiple parallel strands to increase strength.

Which is impossible to do by hand, forcing you to use a 3D printer specific for this job.

On top of that, using airbrushers would severly add air bubbles to actuators, forcing you to use a vacuum chamber to get rid of them.

... Which wouldn't be possible with a mass produced process of airbrushers, requiring conventional 3D printers:

(this is me from the future, you could mix silicone rubber with alcohol or put it on a warm surface to get rid of the bubbles, but syringe 3D printing is also nice)

... But this also brings up other problems: like in the thumbnail, the actuators would be too thick.

The thinner the layers are, the better the DEA works. Some papers used electro spun layers of silicon and electrodes, the same method used for microchips and other things.

Of course, one would need to check how much the air bubbles would interfere with the performance of the DEAs and how much the thickness would also interfere in order to find a middle-ground or a better option of the two.

... Which would need to be tested...

(ChatGPT and BingGPT said that thickness messes up with the response and softness, air bubbles with the capacitance and life cycle)

By the way, you could use any kind of conductive material as long it has the two flexible electrodes and a flexible dielectric filler.

This means that you could even use polymers, normal rubbers and so on.

And as such, maybe you could get rid of the air bubbles using plastics like PVA and/or PVP...

By the way, dielectric elastomers use electrostatic current, meaning that the voltage is on the 5 kilovolts, but with an absurdely small amperage.
So, 5000 volts x 0,0001 amps = 5 watts, Just like 5 volts x 1 amp = 5 watts.
The conversion of normal current into electrostatic has also its own inneficiencies.

Even so, it has its own limits (as shown in the first video on the subject), you would need to find the ideal thickness and the ideal way of carry the electric charges through the actuators.

The same problems I talked about the electromagnetic artificial muscles, which the same (possible) benefits of being simple and as fast as electricity can be.

I looked in a random wire diameter calculator and for a 5000 volt and 0.001 amperage, I would only need a AWG 25 copper cable, which has 0.4 mm of diameter, even if you had 100,000 meters of cable.

And as thus, it is probably not a big deal to calculate which should be the thickness of each part. An advantage over the conventional electromagnetic artificial muscle.
After all, I still couldn't find a way of calculate what should be the thickness of each wire based on is resistivity.

I tried asking to ChatGPT and BingGPT multiple times, and accordingly to them, I would need a cable with 1 cm to 10 cm of diameter to transmit a 1 volt 8 amp current through a material with 5.56e-7 ohms per meter of resistivity (the resistivity of electrolytic copper powder). While electrostatic current in the other hand, would still need the same diameter of the previous calculation (0.4mm to 0.2mm) to transmit the same amount of watts.

Guess Dielectric Elastomers seem to be the winner... 🤔

... If it wasn't for the fact that I can't possibly figure out its efficiency, stroke length and strength.

(Doesn't that mean that I could simply change the actuator for an electrostatic electromagnet instead of a dielectric elastomer?)

Source: https://www.science.org/doi/10.1126/sciadv.abc0251

Source: https://www.researchgate.net/publication/369858087_Versatile_Ultrasoft_Electromagnetic_Actuators_with_Integrated_Strain-Sensing_Cellulose_Nanofibril_Foams

By the way, comb drives use a system similar to biological muscles, but they use electrostatics in order to work.

However, these are used for sensing. One could make them this same way, and these aren't insulated, one could maybe add something dielectric or non-conductive layer to avoid short-circuiting between the teeth.

Although I don't know which would be best...

ChatGPT said that an insulator layer wouldn't work.

"In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field." Wikipedia.

(why did I've made an habit of checking wikipedia as the last resource? Bruh

I'm suggesting this other type of dielectric/electrostatic actuator because to me, it seems easier to 3D print and mass produce, since it wouldn't have the same issues as the other types I talked about before;
The dielectric layer don't need to be soft, in fact, almost no part on it needs to be soft...

But it would still benefit a whole lot if it was as thin as possible, however, since the elastomer is so dense, I think it would compensate for the lack of thinness?

I found this document: https://escholarship.org/content/qt7kf261zf/qt7kf261zf_noSplash_e480d01e957c9dd7a9e06b13b7356899.pdf

In page 38 it has a chart with different types of dielectric elastomers, and their efficiencies vary between 80% to 90% and a strain/stroke of around 30% to 60% (with the exception of pre-strained acrylic, which achieves 300%).

If it is so simple, then why companies aren't employing dielectric elastomer actuators in their bipedal robots and whatsoever?

What I'm missing...?

I asked on Quora and other websites including ChatGPT and BingGPT about this and it seems like the "catch" is the durability of this type of actuator.

Some sources say these only survive 1000 cycles, others say 1 million cycles.

I searched the amount of cycles that humans take for every hour, and it goes around 4800 to 13000 cycles per hour, which would mean each dielectric elastomer actuator would survive for only 3 to 8 days of non-stop walking (if its durability is around 1 million cycles).

On the dielectric elastomer wikipedia section itself is said that using hydrogels is a possible way of increasing its durability.

ChatGPT suggested me making an hydrogel using PVA, borax, glycerol and a conductive powder like salt, with the exception of the later two, this is basically the recipe for shear thickening fluid, lol.

By the way, I was thinking of using hydrogels for the electrodes and silicone rubber for the dielectric part that is to be sandwiched.

Not to mention the low strength, but that could be solved by simply twisting the filaments just like they did with fishing line artificial muscles, which have even lower stroke lengths and even lower force values.

... One thing makes me wondering, though... If thee actuators work like capacitors, wouldn't that mean that the actuators themselves are capable of storing energy somehow? And that energy could be reused for other actuations? Increasing its overall efficiency...?

By the way, dielectric elastomers are both sensors and actuators, so you could also make them into a sensor/haptic feedback system.

If you figure out a way of making a dielectric elastomer actuator that can withstand the strengths in a mechsui/exosuit, maybe you could make ornithopters...

Oh yeah, I almost forgot: you can still choose to use the dielectric elastomers as hydraulic pumps instead of use them as the primary actuator.

By god I hope this is the last time that I edit this project log (today is 31/12/2023, I've created the first tech tree log 2 months ago)

Well, let's just remember that I'm going through all this trouble of studying every single type of artificial muscle because I don't know how to make Carbon Nanotube artificial muscles.

I heard they are extremely efficient (I couldn't find any kind of precise information for that), but as far as I could find, the electrical way they activate is through Lorentz Force, which is not that strong, neither that efficient. But the carbon nanotubes have advantages over other mediums (such as copper wires) because they are on the nano-meter scale, and thus, the closer the electromagnetic field, the stronger it is.

This is the video in which he explains how the muscle works, which sounds extremely similar to how lorentz force works. One could still use extremely thin copper wires or other materials for that.
The thinnest copper cable is AWG 50, which has 0.02 mm of diameter, which is 20,000 times bigger than a medium-sized carbon nanotube (just now I found out about copper nanowires and zinc-oxide nanowires, but I couldn't find any source explaining how to make them in a way as useful as carbon nanotubes, they are normally used as conductive powder/catalyst).

On top of it, the last big breakthrough on the production of carbon nanotubes was 3 years ago and it was growing 12cm of it uninterrupted for days, and to me, it seems like it would need some post-processing.

You literally need to pump acetylene gas (explosive, flamable and unstable) in a chamber with a metal plate at hundreds of degree celsius.

How you do that in a homemade setup? You don't.

And there really isn't any other way I know of, because if it was, carbon nanotube muscles would be common.

You know what I said about metal oxide nanowires? There are also polymer based nanowires.

There is a crapton of ways of making these polymer based nanowires out of conductive polymers like Polyacetylene, Polyaniline, Polypyrrole and Polythiophene (I can't find them to buy online, only through polymer factories).

But while searching I think I got an idea:

There are syringes which have needles with an inner-diameter in the 2-5 nanometers of opening, these are called nanoneedles and are super cheap to find. From tattoo pens, to syringes to insulin pens.

This means that I could simply mix conductive polymers and conductive materials (like graphite or copper nanopowder) and extrude them through these nanoneedles, making little spagethi streams of conductive nanowires that are the same size as caron nanotubes and would act just like them (maybe). :|

I don't know how well it would work, but you could dissolve conductive polymers on acetone/glycol/ethanol and extrude it on warm (warm, not boiling) oil, so the polymer can dry out and not be on risk of simply breaking due to its absurd thinness.

(But since I can't find conductive polymers for the life of me, I would either make super fine graphite/graphene powder or try to make a graphite mold out of the needles and extrude molten copper)

... I kinda feel stupid since I didn't had this obvious idea before.

But to be honest, it is hard to tell if adding conductive powder will work, after all it is a needle with around 2-5 nanometer of diameter.

What garantee I have that the powder won't clog and probably damage (or even pop) the syringe needles?

I would be forced to either make a super ultra mega DIY thin powder or I would need to use only conductive liquids/polymers in order to make it to work.

maybe I could also use the same techniques used on carbon nanotubes in order to increase its strength, stroke and efficiency.

... Actually, the more I think about this, the less it feels like it wold work. The carbon nanotube artificial muscles uses voltage charges, meaning it is dielectric.

I could simply make graphene infused silicone rubber nanofibers with PVA/teflon as an "enamel" layer, but even then, I don't think it would work...

By the way, this nanoneedle also means that I could make super ultra thin dielectric elastomers (if the nanowires doesn't work out) with PVA on the electrodes and pure silicone rubber as the dielectric material (or the reverse).

I wish I could add the extra thingies that I talked about (graphite/graphene powder), but it wouldn't pass through the nanoneedles.

Speaking of which, would a fibrous electrode dielectric elastomer work?

What I mean is: nano-wires A is the entire positive electrode and it is covered in dielectric material (like enameled copper), nano-wires B are the negative electrode and they are exposed (or also covered), would these two fibers attractand coil on each other? Like a muscle?

However, if you change what you want from the muscles, the picture changes a lot.
Specially if you want a high lifting to weight ratio.

I were only looking at the speed, strength and easiness of production, but if you look at the lifting ratio, all of them are quite bad.

The dielectric elastomer silicone rubber can only achieve a lifting ratio of 10 times its own weight (10:1), meaning that if I wanted to lift 3000 kilograms, I would need 300 kilograms worth of dielectric elastomers. Even the elastomer muscle video can only lift 50:1. The steam muscle is a really good option, but I'm really afraid of the consequences of using high pressure steam. The nylon/polyethylene only achieve 100:1, the hydraulic and pneumatic ones 1000:1.

(By the way, just now I remembered that the dielectric elastomer has a limited lift-to-weight ratio because it isn't various fibers, the same problem with the electromagnets stacked one above another)

But the winner of them all (in force to weight ratio) is the thermal carbon-fiber/silicone rubber artificial muscle, which can lift 12,000 times its own weight.

This muscle and this muscle works by the expansion of material, pully the fibers apart, just like any mckibben muscle, the difference is that the material is solid and the fibers are inside of it.

Yes, I would need to add a whole amount of sections to heat it up progressively like I talked above, plus the water spray for instant cooling, but it would still be more practical than the others.

However, I was wondering if adding polyethylene/nylon would make the muscle work better, since it depends on the swelling of the silicone rubber heated by the carbon fiber.

Accodingly to ChatGPT and BingGPT, silicone rubber has a high coefficient of thermal expansion, unlike polyethylene and nylon, which have half to less of it.

Well, if that is so, I wish I knew more about the properties of materials in order to seek out the best ones for artificial muscles. If thermal expansion coefficient is better at certain materials, then the thermal coefficient of others won't be as attractive. I can only imagine if I knew what were the best properties of every material in order to make the perfect artificial muscle...

I thinkit would be like searching for a good orange for a bitter plate and knowing that a lemon is a better source of bitterness.

By the way, silicone rubber has a coefficient of thermal expansion (CTE) of 200 to 400 ppm/ºC.

Ethylene-vinyl-acetate (EVA) with 950 - 960 ppm/ºC
Natural rubber with 920 - 930 ppm/ºC
Polychloroprene (Neoprene) with 1,200 - 1,300 ppm/ºC
Polyisoprene rubber with 930 - 940 ppm/ºC
Polyurethane with 1,000 - 1,300 ppm/ºC
Silicone elastomers with 1,300 - 1,800 ppm/ºC

These are the materials that BingGPT sent me.

By the way, I saw this thermal artificial muscle made out of HDPE and COCe (Cyclic Olefin Copolymer Elastomer). I can't find COCe to buy online for the life of me, but maybe with the use of EVA, Polyurethane and meltable rubber, one could replace it with a more common material.

Being honest, after all this useless talk, I really don't know which option is best... I just feel stupid and useless to be honest...

Third: Structure.

The actuators need an skeleton to be attached to.

This one is not an actual impossibility at the moment, any kind of aluminium, steel or even plastic can support the force of the muscles and the weight of the mech.

The problem is that you would need to design the damn structure and go through the problem of actually building it, which would be both labor intensive and require a professional engineer to check/project such structure.

I thought on maybe trying to make a 3D model on my own using FreeCAD or Blender, but sincerily, I don't think I have any will power left in myself after 1 year of hitting roadblock after roadblock with this project.

What would even be the point of giving my all on making an articial skeleton since all other problems weren't solved?

I don't even have the money to test each part of the project, imagine actually building it.

Relevant to remember Hacksmith industries, they've made actual mechs (including the one above), and in all videos they show how difficult such task actually is.

I mean, they are sponsored professionals, so they have all the resources and all the resources that they needed.

... And yet, they had a crapton of difficulties, almost gave up on the project and still, on the end, the robot simply broke up, ending their years of effort.

Now, imagine me, a dumbass without any kind of degree on anything useful (I have on graphic design coff coff). Trying to do a mech. Alone.

In either way, one would need to plan how many tons of weight each limb would support, and on top of that, figure out if the structure will handle falling into the ground, running, jumping and whatever other actions one would need to peform.

Let's just remember that each part of the body is technically a lever, and each subsequent part of the body needs to be more powerful than the previous one. The shoulders would need to be X times stronger than the arms, the torso be X times stronger than the previous two and finally the legs that would need to be X times stronger than all others.

The "best" rule of thumb is to make everything somewhat stronger than it needs to be and make the legs 3 times stronger (it is said that the lower part of the human body is 3 times stronger than the upper part, and that is why you can carry weight and still be able to run and jump, besides your own weight).

I thought on using High Density Polyethylene (HDPE) reinforced with fibers (of whatever type, glass fibers, carbon fibers, even wood fibers etc) at first because I could simply recycle it, but I couldn't figure out how thicker the structure would need to be. And assuming that the tensile strength of HDPE (around 20 to 30 MPa or 300 bars) is 1:1 to kilograms, then it would be able to sustain 300kg... But I don't know at which thickness, which structural shape would be the best and so on.

The same applies to Aluminium, which I thought on turning it into heat treated aluminium 6061 or aluminium 7075 and on top of that, reinforce it with iron or steel cables, like a metal composite.
But aluminium is terrible with fatigue, in the sense of being not that good with dealing with repeated tension/compression cycles very fast, like in a mechanical component.
Drag cars use aluminium piston rods on its construction because of the light weight, but these same piston rods wouldn't last more than a month in a conventional car.

However, I don't fully understand metallurgy and how much material properly acts under certain circumstances. Which a professional would be able to tell.

I also thought on DIYing Titanium Aluminate, which is a 60% Titanium 40% aluminium alloy that uses the benefits of both alloys.
I would be doing that by taking titanium dioxide (which is both a food and agriculture product that is really cheap) and use the hydrogen reduction reaction to take off the oxygen from the titanium.
But even then, I would need a furnace that reaches the temperature of titanium to melt (2500 ºC) which is not easy even with industrial standards.

Steel is the final option, and I thought on mixing silicon and tungsten with it in order to create a good steel alloy like AR 500 or other types.

But Steel is hard to deal aswell, and the tools required to weld, forge, hammer and cut are expensive and equally as heavy.

One would need to actually figure out how much material and in which shape, size and weight each type of material would require to be in order to make something appropriate for a mech or/and an exoskeleton.

Fourth: Control.

Well, what is the need for a mech/exoskeleton if you can't control it?

Like I said in the beginning of this tech tree thingie: you could "easily" overcome the problem of control and precision with proper encoders and programming, but you would exponentially increase the cost and complexity of the system. Just like an industrial robot, and those robots are as expensive (or more) than a house.

The best I could think/find was something similar to what James Bruton first did do his DIY Iron Man exosuit:

In resume, he put hall sensors (cheap proximity sensors that only know the distance it is from a magnet) in a rubber box, so the more he approached one of the points, the more the suit moved in said direction.

The idea would do the same thing to the Exoskeleton or Mechanoid suit, but putting the hall sensors in the body of the pilot on the same points the artificial muscles would be in the artificial skeleton.

So, if you lifted a biceps in a certain way, both hall sensors (under and over your forearm) would notice a difference in distance over time and try to keep the suit from overpulling and underpushing the arm as fast as it could; In the case of the exoskeleton it would be "easier" to do this, since the body would be moving with the suit at the same time.

The Mechanoid suit wouldn't be so easy, as far as I could think.

For example, if you made a solid shell around the pilot's body using this technique for motion control, the system would be more or less "blind", because you wouldn't be receiving the sensation feedback.
You would need some haptic system (a system that simulates the touch of the mech into your own body), it would be easier to do if you connected servos in some kind of motion suit like in the Avatar movie.

But I think it would be a little complicated to do that with an artificial muscle system.

Another option that I was able to think was to make a "second skin" both for the mech and for the pilot while connecting these.

Let's say, like a large blanket full of sensors (like piezoelectric sensors).

Piezoeletric buzzers/actuators/sensors generate a small eletric current when exposed to vibration and/or impacts, and when receiving electric currents can produce sound and/or vibrate in a certain way.

The problem is that this option would be pretty labour intensive and could be full of defects and problems, you could make a different "sleeve-skin" for every part of the body, but still, it would be a lot of piezoelectric buzzers.

Plus, how you would define the vibration?

For example, how do you know where is your mouth is when eating? You know that because your sense of touch is "on" all the time, this way you know where each part of your body is at all times.

How the vibration of the second skin would transmit the sense of touch all the time? What about scratches? Bumps? Impacts? Changes in temperature? How you would convey the information you want to transmit into the haptic suit?

By the way, there is a myriad of different ways of making haptic sensors, this one uses fluids connected to sensors (I forgot which type) and can be made with silicon, rubber or whatever other flexible material.

Source: https://www.semanticscholar.org/paper/Skinflow%3A-A-soft-robotic-skin-based-on-fluidic-Soter-Garrad/2d76201c5700dc899ab18d419119d82be113f0fc

The problem is still the same: even if the "skin" itself is relatively easy to make and on the cheap, it is labour intensive.

Even if you could simply connect a flexible silicon skin from the mech to the person inside without any kind of electronics, how the heck you would fill and connect all the thousands of tubes? What if some of them rip apart or simply pops?

I also found this interesting article:

Source: https://www.nature.com/articles/ncomms6747

Well, I didn't read this article yet to see how they were able to make the sensors, but I would make a guess that one would be able to make printable skin sensors with conductive inks.

In each video below it shous varios methods for printing circuits and other types of sensors, including thermal sensors and even antennas.

(by the way, these printed circuits and sensors can be applied to any medium: paper, cloths, plastics, rubber sheets etc)

Well, I don't know what would be the best method of DIYing these printable sensors (using conventional printers or relief prints, like old journals were made), but one would need to figure out what sensor to put where and how to connect each one.

For example, what is the sequence of sensor layers you would need to use? Touch, thermal and humidity one above another? Maybe put each one on the same layer? How you would connect and transfer these sensations to the haptic suit of the pilot?

Would the printed sensors be able to be used as printed actuators?

While searching for a little bit, I found this electromagnetic ink printed actuator:

Source: https://www.mdpi.com/2076-0825/5/3/21

Well, it is not that useful for an artificial muscle, but maybe if you made a coil on both ends, it could be used as a vibration actuator for haptic sensing...

Although I don't know how I would make it through a large blanket/sheet, maybe you would need to align two sets of blankets that would attract and repel each other in order to make a vibration.

... But I don't know how perceptible it would be, a lot of things that I suggest would need to be throughly tested in order to be considered viable for its function.

... Which further increases the cost and complexity of the project.

I also found out this video this guy made, again, you could replace the magnet with an opposite magnetic coil.

The problem is that you would need to find a way of making a flexure stand.

Well, this madlad here made a speaker with conductive ink and paper:

Source: https://www.zachrotholz.com/paper-speakers.html

As far as I understand, sound is vibration, so if you can make a speaker with conductive ink and a mirroed coil (assume that the paper in the picture is folded in the middle), you've made a vibration actuator.

Maybe a good way of making a inkjet printed haptic actuator would be to not use any actuator at all, but electricity itself.

The idea would be to directly electroctute the skin with a small voltage in a sequence simulating vibration.

Source: https://www.nature.com/articles/s42256-022-00543-y

I found this article that uses hydrogel.

The only problem is that the haptic material needs to be in direct contact with the user's skin, which is not convenient if you want to wear clothes. >.>

Maybe this could be reserved for the feet, lower legs, forearms and hands. Which are exactly the parts of the body that you would be using the most, and you can easily lift you clothes for these parts.

I also saw other options that suggested using printed heaters for the haptic feedback, but I don't know how fast it would be to generate enough heat to simulate touch.

Also, I found this option here that I thought it was interesting:

01/01/2024 and I'm still editing this blasted project log.

Well, even though I said I gave up on the project, I still actively search on all my free-time simply because it is some kind of hobby, I suppose.

And one of those times while I was researching, I accidentaly found out about brain-computer interface.

The thing is that one could make a radar array around the human brain and interpret the sinapses/signals of the brain, spine or local nerves in the body in order to control prosthestics.

I couldn't find much information on the subject, and the little that I found, I didn't even gave a chance on trying reading them.

But let's imagine it like this: imagine the brain activity detection array of said radar is made of thousands of voxels with 1x1 mm of diameter.

One could "brute-force" the interface by detecting the position of every part of the body, every part of the brain and making a Deep Learning AI to interpret the signals in order to command the prosthetics in a certain way.

This way you could control the mech/exosuit with your brain instinctively, maybe you could even help prosthetic users with such thing.

... The problem is: how to make said radar array? Can radars even be used to see human brains?

Magnetic Ressonance Imaging? This thing uses superconductors cooled by liquid helium and costs million of dollars.

Electroencephalography (EEG) Sensors? These only work with a general activity of your brain.

The closest thing I could find was TMS (transcranial magnetic stimulation), which works with induction coils (I think), which could be used both to detect and to induct responses on the brain.

Buuuut... As you can imagine, there isn't any kind of machine like that.

In fact, I don't even know if the MRI machines have such insane resolution as 1mm voxels, imagine doing it in real time while you think on a myriad of different things?

Imagine the amount of gigabytes you would produce per second.

With radars? What kind of radar can see the human brain? I just found this one picture, but it doesn't look like it would have 1x1 mm definition...

(The induction coils make me wonder: could one use them to make a blind person see again by inducing currents on the eye nerves and/or on the brain?)

Accordingly to this link there are 684,000 neurons in a 1x1mm voxel.

... Which puts into question if this is enough.

Also, I don't have any idea of how to make a Voxel Scanner, but it seems like it is conventional practice on MRIs and the like.

The best idea I could come up with was simply imagining the electromagnetic waves as light, just imagine that each radar is a magnifying glass, focusing light in a single point in the air, and there are thousands other radars focusing on other 1mm focused light balls through your brain.

The obvious problem is how to do that.

The human brain typically has motherfricking 1,100,000 cubic milimeters, how the hell I am to make a homemade Voxel Radar that will have 1.1 million focusing points?

If one where to reduce each voxel to 1 (on) and 0 (off) state, you would still consume 0,0011 gigabytes for every time you scan, so, let's say, a 24 FPS (or 24 scans per second) would give 0.02 gigabytes per second of information.

A single second. :|

On top of that, as you can see in the picture above, there is no such thing as a simple "on and off" neuron (I think).

In any manner, I'm checking DIY electromagnetic 3D scanners, maybe these can be useful for something.

(it wasn't)

Also, this guy made a DIY MRI machine

Power Source:

Diesel Engine to Charcoal Engine:

How much energy I could store with those dielectric materials?

Off-topic:

Not Off-topic - Revisiting Actuators:

Design of the Artificial muscles:

Materials for dielectric elastomers:

Well then... I've made this huge list, now what?

First:

Second:

Third:

"This thing might kill me"

Mech design:

Articles that I think are interesting for biomimetic human robot:

Also, links relevant for heavy animal anatomy:

Off-topic:

Adding this here because I'm afraid of the project log deleting some things:

Types of mechs that are viable/practical or not:

Hydraulic Mech: ❌

Hydrolysis Pneumatic Mech: ❓

Evaporative Pneumatic Mech: ❌

Dielectric Elastomer Actuator Mech: ❓

1: Modeling and Characterizing a Fiber-Reinforced Dielectric Elastomer Tension Actuator

2: "Printing Reconfigurable Bundles of Dielectric Elastomer Fibers"

3: "A Jumping Robot Driven by a Dielectric Elastomer Actuator"

4: "Triblock Copolymer Organogels as High-Performance Dielectric Elastomers"

5: "A processable, high-performance dielectric elastomer and multilayering process"

6: "A large-strain and ultrahigh energy density dielectric elastomer for fast moving soft robot"

Thermoactive Actuators Mech: ❓

Other options: ❌

Re-calculating:

Multifilament Hydraulic McKibben Muscles:

Conventional Hydraulic McKibben Artificial Muscles:

Fluid Flow:

Dielectric Elastomers:

Pneumatic McKibben

Screw actuator:

Off-topic:

Now I "just" need to do it.

Actuator:

Energy Source:

Structure:

Highly Porous Heater:

About the dielectric elastomer:

Off-topic:

Let's talk about energy sources.

Universal Fuel cells:

Room Temperature Turbine Engines:

Stirling engines:

Thermoelectric Generators:

Off-topic:

What I need to look for?

Steam-driven Actuators:

Dielectric Elastomer Actuators:

Dielectric Pump:

Testing things out:

4360 horsepower or 3,270,000 watts of power.

In the end, it is indeed it is 81.6 watts per kilogram of weight at 4 meters per second of speed. A simply legged exosuit would consume around 8 kilowatts/10 horsepower for every 100kg of weight being lifted at 8 meters per second, half at 4 meters per second.. Not great, not bad, I'd rather say.

Third: Structure.

Fourth: Control.