3D printed truck

3D printed running aid

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The ultimate running aid was big enough & the 3D printed truck became so big that it was decided to separate the 2.

The high cost of good RC truck kits, diminishing need for such kits & the noise of gearboxes made lions look elsewhere for a robot platform.  3D printing a truck from scratch, with only a few metal parts still being off the shelf, was the next step.  The only parts which have to be outsourced are the motors, steering servo, & steering knuckles.  Everything else is 3D printed, made of coroplastic, or home made electronicals.  The size was based on the original Tamiya lunchbox.


Motor numbers are comprised by their diameter & length, so a 4248 has a 42mm diameter & 48mm length.

The current ship has a Propdrive 4248 of any KV rewound with 20 turns of 26AWG according to the diagram.   It doesn't produce enough torque to go up hills.

A Propdrive 5060 with lower AWG & more turns would be a better match.

Steering knuckles:

These have to match the wheel base, to achieve ackerman steering.  Lions use

Jazrider Aluminum Front Steering Knuckle Upright For Tamiya RC CW01/Lunch Box

from fleebay & size the wheel base to within 1" of a lunchbox.  

Steering servo:

The lion kingdom uses discontinued trackstar brushless servos with servo savers.  Brushless is required to get any life out of them.

The 3 mane components are the steering module, traction module, & the coroplastic container.  They're held together by  aluminum angle rods.

The tires are 3D printed out of TPU for a lot less money than Chinese ones.

The final mechanical piece is the paw controller.  It uses springs from ball point pens.

Electronicals provide semi autonomous throttle & steering.

  • New tire

    lion mclionhead11/13/2021 at 07:49 0 comments

    The last tire was real fragged.

    So along came another one at 230C, with a 1.6mm tread.  It still had voids.  Some guys leave their filament on an enclosed print bed for 5 hours.  Another thing which might improve layer adhesion is breaking up the smooth tread with slight ridges. A smooth tread still has the best traction with TPU.

    As rough as printed tires are, it pays to remember what lions did before 3D printing.  Those were desperate times.

  • Antlers

    lion mclionhead10/30/2021 at 03:05 0 comments

    After much anguish, new antlers rolled off the printing press like an economic stimulus package.  There was another fruitless search for cheap commercial options.   A design was reached which didn't need support or infill, could be easily popped off in the field.

    Orange PLA with a brown sharpie made a surprisingly realistic woodgrain texture.  The lion kingdom couldn't afford to dunk it in wood stain.   It was surprising to find brown sharpies still in existence, in a time when 31 flavors of ice cream are the enemy of equality.

    They went in series, off of 5.5V.  The original package ran on 2 AA's.  The next step was the nose mount & final assembly.

    Heating to 280C in a special jig managed to release the selastic just enough to pry off the heat sink.

    The new nose mount could use a lot of changes to make it easier to screw in the clamps & use string instead of zip ties. 

    It was designed in a time when 25 zip ties were $1.  3mm zip ties aren't even made anymore.  A better design would use bolts.  

    Every iteration of robo rudolf gets better & this year was definitely a big leap.

  • Rudolf update

    lion mclionhead10/26/2021 at 04:31 0 comments

    The decision was made to electrify the antlers.  The copper is so heavy, it might be time to replace the pipe cleaners with copper or orange PLA.  Brown is just dark orange.

    These cheaply soldered, unregulated battery powered LEDs were $4 at the homeless despot, but the same hot snotted, unregulated, battery powered goodness can cost up to $30, depending on length.

    Brightening the nose is a harder problem.  4 10mm LEDs in a diffuser aren't bright enough. 

    There was enough desire to immerse the trail in bright red like the movie to spend more than the minimum but not $50.  Thus arrived the $15 methusela of lightbulbs, the 100W equivalent RGB Cree.

    After much onboarding, passwords, & configuration, it was compared to the lion kingdom's previous 4 LED nose with conventional bulb glued on.

    It became clear that the brightness per area is the same, but the methusela outputs more light by lighting a larger area than a standard bulb.

    The app is an extremely painful way to change colors.  It's obviously intended for someone who wants the light to change color based on time.  Despite all its features, there's no simulation of a fire, a candle or a strobe.  It's just aimed at a multi millionaire homeower or rich gootuber.

    It's a lot brighter than the house lights, but it's a lot more expensive, so lions can't complane.

    The lion kingdom doesn't have any other use for it & already has a drawer full of unused spiral lights.  Despite its cost, it's actually comparable to the $10 lions paid for the 1st spiral lights.  Generation X was really schmick with its fluorescent spiral lights in 2001.

    The teardown revealed it to be junk.

    Only the 4 center LEDs are used in color mode.  The white ones are only used in white mode, even if the color mode is white.  The rated brightness on these is for white light only.  Definitely not worth it for color, but still worth it for adjusting the temperature of white light.  The sane way to get colored light is the good old snail mailed COB.

    V+ - R- is 13.9 for full red

    VBUS is 140 & obviously powers the white LEDs through WH- & WL-.  It would not be possible to run it in white mode without an inverter.

    The LEDs are glued on a heat sink which can't be removed.

    The money being permanently spent, the only solution was to whack on the $1 dome & call an end to the brief taste of multimillionaire luxury.

    The rich gootuber with the $50 Philips Hue lights (not sponsored) & the $1/2 million cabin:

  • Cyclops light

    lion mclionhead10/24/2021 at 03:30 0 comments

    After an unfortunate toe injury, the decision was made to install a very bright, removable light to try to improve the visibility of the path.  A 60W LED bulb was converted to 8.2V 200mA.

    Then a heat resistant mount was printed out of PETG.

    The prolific jump in zip tie prices has led to string.

    It was hard to make any conclusions in a parking lot.  That was the last of the dry weather for 36 hours.  The mane problem is without a reflector, it's very diffuse.

  • Captive locknut motor farsteners

    lion mclionhead09/29/2021 at 04:45 0 comments

    It occurred to the lion kingdom that the use of self tappers as load bearing farsteners has been a disaster of biblical proportions. The latest thinking was to use captive 4-40 locknuts & hot glue to farsten the locknuts. The new motor module still managed to have acceptible tolerances with the .8mm nozzle.

    The hot glue actually seemed to work. If it got in the way, it managed to be compliant enough for the screw to not push it out. The captive nut walls are still too thick. The nuts aren't going to break PLA. It's going to compress.

    The mane unknowns are if the 4-40 bolts are going to stay on as well as the self tappers did & if the motor will find another way to stall when it overheats or if it'll just destroy itself.

    After 3 miles with the locknut motor plates, the right motor let out the magic smoke. It manifested itself as a loss of torque despite accurate commutation. There was no evidence of the encoder failing, the locknuts getting loose, a stall, or debris. The motor just stopped providing torque & overheated after successfully ascending part of a hill.

    Decided to rewind it over the next 4 hours & see if the problem happened again. Sadly, the 32 AWG got tangled. If 32 AWG gets tangled, the only solution is to cut it off & throw it away. It can't be untangled. Ended up doing 2 of the fields in the last of the 26 AWG & ordered another spool of 26 AWG since there is going to be a lot of magic smoke.

    What's probably going to happen is a switch back to self tappers. There was no evidence of the locknuts causing the failure, but they were the only explanation. The best explanation is the rebuild was slightly off, causing the encoder to miss just enough to suck more power but not stall. The overheating would have caused the motor to stall before burning up, with self tappers. The locknuts allowed it to overheat without stalling until it died.

    Chinese direct drive motors don't have these problems because their sensors are epoxied into solid steel & their motor mounts are solid steel to suck away any heat.

    So 8.7 miles with the latest motor rewinding sucked a whopping 190mAh/mile. Solid core 26 AWG might actually be more efficient than quad 32 AWG. The best explanation lions have is the skin effect. In a high frequency PWM application, skin effect causes more resistance as wire diameter decreases. Laminated quad 32 AWG has 4 times more surface area than solid core 26 AWG, so the quad 32 AWG would have a lot more resistance than solid core 26 AWG. You'd think it would matter more for kilometers of wire & megahertz than a motor winding.

    It's become clear that the motor encoder is getting knocked out of alignment & the reason probably isn't loose cables snagging it. Lacking any reason, the idea of farstening thermisters to the motors is gaining traction. In 1985, thermisters might have been available in every corner Radio Shack, but in the future they're a little hard to come by.

    Daily repair work turned to a failure of the happy meal controller to charge anymore. It had salt water damage around the battery management chip, so the latest clamshell still isn't repelling water.

  • MHPS2285 vs MHPS2266

    lion mclionhead09/28/2021 at 04:40 0 comments

    There was some regret after buying the 8.5mm MHPS2283 switches instead of the 6mm MHPS2266 switches.  It turned out there were a few 2266 switches in some doll hair LED lights which arrived before the age of 3D printing.  They must not have been seen as useful, since no custom enclosure could be printed.  Now that they can be used,  they're garbage.  They're just too small to give the satisfying click of the 8.5mm.  They're also a lot more fragile & wouldn't last long.  The 8.5mm were what we had in the 80's & they defined satisfying clicks for lions.  

    There is a need to build new remote controls for a camera, so the choice of switches has arisen again.

  • Death of PLA retaining rings & servos

    lion mclionhead09/12/2021 at 05:50 0 comments

    Sharpied the final designs on. PLA+ is shinier than PLA, making it look slightly more upscale, but PLA+ is expensive so the lion kingdom didn't order any more after the container.

    Sadly, the latest retaining ring popped right off. 1 problem is it can't be inserted bed side up, so it has a bevel which just slides off. After a moment of grief & debating destructive shaft modifications, the decision was made to spend $25 on a set of steel retaining rings & a retaining ring tool. It was as much as a new motor.

    This tool doesn't fit anything smaller than M6.  M6 requires the aid of a metal rod to separate the ring.

    The era of 3D printed retaining rings had come to a close, after 6 months.  The problem with modifying the shaft for another PLA structure was how a more robust PLA retaining ring would slide on. It would entail removing the encoder & then removing the pin, instead of just removing the encoder. Getting the right tool for the job was the only way.

    Stashed a repair kit in the battery compartment while waiting for the snail mail shipment of retaining rings.  This can unbolt a wheel & either reseat or remove an o-ring.  Lions haven't had any luck reseating an o-ring in the field, but a sharp screwdriver can cut through TPU.  The battery compartment has enough room for contraband, but if screwdrivers aren't pointing forward, they'll get trapped.

    In servo land, the SPT died the same way the Hextronix died, a sudden full left lockup followed by intermittent restoration after wiggling the cable. Power cycling it did nothing. It's been 7 years of chasing erratic servo behavior. Most of it might be pots & motors wearing out. The last few have been converging on the wiring.

    The cable has been already replaced. Replaced it again. This one is coming down to a loose solder ball or dry solder joint. So that's 2 days of not going anywhere because of a retaining ring, dead servo, dead 3D printer.

    Pressing down on the board in just the right way got the servo to glitch reproducibly.  Only after thoroughly cleaning the PWM trace, the problem finally appeared.

    There was a micrometer scale break in the trace, completely invisible when it was dirty.  It's believed to have been there since the board was made.  The board was made with a dedicated buck converter for the servo.  An xacto nicked it while cutting a wire to the buck converter.  The oldest photo is too small & dark, but some grotesque unsharping reveals 3 slightly brighter pixels in a row where the break was spotted later.

    The break only cost $35 in unnecessary new servos.  The previous $150 of servos were bought during the lunchbox days to solve common wear.

    There was another bought of overheating motor.  It was blamed on a tangled cable jamming the encoder, but there's no obvious way for it to get in the encoder. The cable was pulled tight, since untangling it would be a full day.  Another idea is current in the cable interferes with the hall effect sensors.  

    Finally, there was a case of a tire appearing normal, but actually coming out softer than a sponge.  The filament became hydrated from a swamp cooler.  It was cosmetically indistinguishable from a normal tire until analyzed under a microscope.  Something must be done to more reliably dry TPU.

    This brings us to the motor module.  The use of self tappers as load bearing farsteners is a disaster of biblical proportions.  The latest thinking is to use captive 4-40 locknuts & hot glue to farsten the locknuts.  The motor module might have to be printed with a .4mm nozzle.

  • Container #3

    lion mclionhead09/09/2021 at 21:02 0 comments

    After several days, all the panels were done filament depositioning. None of the 228mm ones had any showstopper defects, though they improved over time. The last panel was a narrower one with no bed heating, but the 228mm ones definitely required it.

    There was an attempt to evolve joining the segments to use PLA zigzags. This was the 1st attempt at expensive printed tape. The mane problem was clamping it to get the adhesive to stick. Magnets were terrible. It really needs a big, expensive jig. 1 piece goes on the flat side. The other piece needs pins pressing on all the facets of the other side. The final solution was spraying water to accelerate the glue, but water leaves a white film.

    Despite the artifacts, the hassle, & the price tag, the zigzags were visually lightyears ahead of duct tape. The mane issue is how they look when light shines through the panels.

    The corner bumpers had a lot of delamination. They definitely needed 2mm walls & .32mm layers, but the TPU absorbed a lot of water from the lion kingdom's air conditioning.

    Lighting used a slightly improved hot glue process & no solid core wire after all the solid core wire broke in the last container. The 3D printed containers have a lot more flexing near the corners than coroplastic.

    The standard storage compartments went in with duct tape since duck with zip ties has been very robust.

    The lion kingdom likened its own container design to the battery box in the Robotix R-2000.

    According to random ebay photos, the top had a lot of artwork, but it also had a lot of functional polygons for attaching bricks.

    The bottom was a simple grid for strength.  There was no effort where plastic needed to resist the downward force of D cells.  The cleverest part of that kit was a switch for a 5th servo, but only providing 4 servos.  A kid would pay a fortune to get a 5th servo.  Those were very high torque, 360' servos.  

    Apparently, the battery bank was center tapped to provide reverse voltage to the servos.  Semiconductor H-bridges were a fortune in those days, so the answer was 3 rails.  The  lion cub had no concept of cost savings & just thought the 3rd conductor was a professional touch.  Honors & benefits already at the age of 9.

    Today, paying an animal to solder a center tapped battery terminal would cost a fortune compared to using H bridges.

    The inside had some placeholders for the batteries, but nothing structural.  It just relied on a thick shell, probably a generous 2mm.

    The kit in general had a lot of plastic artwork with structural elements, much like what the lion kingdom tried to do.  There's a lot of engineering in making sure plastic bits fit together & don't break, before they ever get to the artwork.

    Stuff like the Robotix kit was probably designed by Milton Bradley employees in New York city, as depicted in Big.  Milton Bradley was a real guy who worked as a draftsman (human CAD program) before trying to sell prints of Abraham Lincoln.  When Lincoln grew a beard, his prints became worthless.  That forced him to sell board games.  Today, the toy companies are all owned by Hasbro & the creative process is all done in China.  Hasbro is just a law firm.

  • New servo & helical front tire

    lion mclionhead09/06/2021 at 21:07 0 comments

    Another 400 miles ended with a shredded tire, burned out servo & cracked rod end.

    So the Hextronix died after 394 miles.  It was a motor burnout.

    In went the SPT.  

    The front tires came up thrashed from old age & going offroad.  

    The decision was made to make a helical front tire like the helical rear tires.  Because of the round tread, it couldn't be a simple C program that replicated & rotated an STL file.  This one performed 96 boolean operations in Blender to create individually rotated layers, over 6 minutes.  

    Blender has proven useful for final pass booleans, but it doesn't do parametric models, can't import a scene graph from FreeCAD, or have a model history.

    It only took 3 tries & $4 of filament to get it close.  They're never the perfect hardness.  

  • High vis controller

    lion mclionhead08/27/2021 at 20:03 0 comments

    The lion kingdom finally upgraded to colored filament.  A high vis paw controller was seen as the biggest win from colored filament.  Orange was the closest PLA color since there are no high vis PLA colors.

    Gootube videos extoll the fluorescence & shine of a $60 filament vs a $18 filament, but lions seriously doubt there's any difference in fluorescence.  It's going to be covered in sweat.

    It was time to model in all the lessons of the last 6 months.  It got a few more M2.6 screws.  The decision was made to skip M1.7 screws, since the amount of PLA required to make a standoff would nullify a smaller screw.  

    The original grey controller was quite soiled.  

    This was the 1st deployment of the clicky momentary pushbutton.  What a great click it is, but it was absolutely worthless when running.

    The electronicals had extreme water damage.  It surprisingly only entered the clamshell facing away from the lion, a retrograde motion of the normal sweat path.

    A trace perished & got a bodge wire replacement.   The other traces got a tinning.  This board is in the twilight of its years. 

    Then it got a hot glue potting.

    A few wires got replaced.  There were 3 hours of damaging a wire to replace a wire, going around the board.

    The mechanicals were an epic disaster.  It seems the orange build series filament does better at 200C than 210C.  At 210C, the layers were expanding randomly.  Tolerances were also way off, from bed leveling deviations.  The mane problem was making sure there wasn't too much of a gap between shafts & bushings.  Screw holes were too big.

    After reprinting a few parts, scraping off some material, the joysticks started working.  The 2 levers need bigger shafts & bigger cross sectional areas to ensure they only move on 1 axis.   The spring being underneath is trying to twist the 2 levers.  

    The tolerances were so bad, the buttons were loosy goosy but managed to not fall out.

    It took a heroic number of prototype guesses, but this is the 1st to be truly ambidextrous.  There's no way to make adjustable controls without making it into a brick, so the only way to adjust anything was to make guesses.  The lion kingdom has come from a time when an ambidextrous controller was impossible, to something that barely worked with loss of circulation, to something that truly works.

    This controller got a rounded throttle stick to address some of the chafing.

    Another feature was a shifting of the sound frequencies to try to make it louder, but this speaker has more of a comb filter than a single resonant frequency.  Sadly, it looks more like a happy meal toy than a high vis controller.  

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