Goliath - A Gas Powered Quadcopter

A BIG Gas Powered Quadcopter

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Goliath is an open source prototype vehicle for developing gas-powered quadcopters.


Goliath is a prototype vehicle for developing large scale quadcopters. The current design is based on a single central gas engine with a belt drive providing power to the four propellers. Control of the vehicle is provided by control vanes placed under the propellers. Each propeller will be enclosed within a duct that protects the rotors and contributes to the lift. Goliath itself will be open source with the creative commons license, and whenever possible open source components are used.

The Mk I vehicle was focused on developing the drive train. The Mk II vehicle was built with lighter weight aluminum frame. Even when completed Goliath is intended as a starting point for future vehicles.

Flight control will be performed using the Pixhawk controller running the PX4 flight stack.

Related Projects

#Inexpensive Composite Propellers/Rotors

#Drone Test Stand

#Measuring Engine RPM with the Pixhawk

#EVPR: Electric Variable Pitch Rotor

Current Status: HOVERING!

The Mk II vehicle has been assembled and hovered for the first time in September 2016.



The initial Mk I frame was constructed using slotted galvanized angle, also known as Dexion, bolted together. While this is heavier than a steel tube or composite frame, the dexion is quickly assembled and can easily be reconfigured. This allowed for multiple iterations of the drive system to be tested with a minimum of time and cost.

The Mk II frame is built using aluminum tube and assembled using aluminum gussets and and stainless steel rivets. This leads to a lightweight, vibration resistent design that can be assembled easily.


An electric powered design would have been the most straightforward approach. Electric motors are more efficient than gas motors, but the energy density of gasoline is much greater than today's batteries. So until battery technology improves, for large scale vehicles, gas power seemed the way to go.

Goliath currently uses a single 30 Hp vertical shaft engine and a belt system to transfer power to the four propellers. The setup was chosen because at this scale, four smaller gas engines have a smaller power to weight ratio than a single larger engine. The specific engine, an 810cc Briggs and Stratton Commercial engine was chosen primarily because of its relative low cost per power ratio.

Drive System

The drive system uses High Torque Drive (HTD) belts. These belts are made of neoprene rubber with continuous fiberglass cords. HTD belts are able to transfer more power per weight than roller chain and can also run at higher RPMs that Goliath requires.

To eliminate aerodynamic torque, the drive system rotates two propellers clockwise (CW) and two counter-clockwise (CCW). This is done by using two belts, one sided sided and the second double sided. The direction of rotation is changed by placing the outside of the double sided belt against the driving pulley.


The propellers are fixed pitch propellers 36 inches in diameter. They are custom made, starting from a foam blank with birch stiffeners. The blanks are machined using a CNC router and then fiberglass and epoxy are laid up over the machined core. This process produces a propeller that can carry over 60 lbs while only weighing one and a quarter pounds.


An electric quadcopter would traditionally maneuver by varying the speed of each propeller to control thrust. Since Goliath uses fixed pitch propellers and all the propellers turn at the same speed due to the belt drive, maneuvering will be done by control vanes similar to those used to steer hovercraft.


Each of the two exhaust pipes are built from Go-Kart hardware, which are easy to procure and inexpensive. The U-Build It Kits are easily assembled using a minimum of welding and highly customizable.

Electrical System

The electrical system is powered primarily from the alternator with the battery as a backup. The battery is 12V and designed for off-road vehicles, so it'll handle high vibration loads. The micro-controllers and servos...

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  • 1 × 30 HP vertical shaft gas engine Should equipped with a starter and alternator
  • 1 × Pixhawk Open Source Flight Controller
  • 2 × Clockwise Propellers (36" Diameter) See Detailed Build Instructions for Raw Materials (Forthcoming)
  • 2 × Counter Clockwise Propellers (36" Diameter) See Detailed Build Instructions for Raw Materials (Forthcoming)
  • 4 × Duct (37" Inner Diameter) See Detailed Build Instructions for Raw Materials (Forthcoming)

View all 22 components

  • Goliath Mk. III

    Peter McCloud06/05/2019 at 03:36 0 comments

    The hardware for Titan, Goliath's bigger brother is starting to come together. The engine has arrived and the first frame elements are taking shape.

    With Titan's design progressing, there's a need to test portions of the hardware before integrating the complete vehicle, particularly the rotors. Additionally, designing Titan has been educational, and some of the lessons learned can be applied to Goliath.  So this summer, work will start on upgrading Goliath to a Mk. III design with an update to the drive system and 42" rotors (vs. the previous 36" rotors).

    The #EVPR: Electric Variable Pitch Rotors will also receive a custom PCB designed by our very first intern. Things are falling into place to make a lot of progress this summer, so stay tuned.

    P.S. If are interested in progress updates specific to Goliath, check out  or follow us on LinkedIn

  • Goliath Expecting a Sibling in 2019

    Peter McCloud01/31/2019 at 18:57 0 comments

    Goliath is still moving forward, but work has already begun on the next vehicle that will incorporate the lessons learned from Goliath Mk. I and II. Over the past few months, I've been working on the conceptual design for the new vehicle, called Titan. The design has progressed to the point that today, the deposit was placed for the engine that will power Titan.

    It will be 3-4 months until the engine arrives and as the design matures, I'll be providing more details on the design. The goal is to have the vehicle assembled and begin testing by the end of 2019.

  • Pixhawk/PX4 Mixer Issues Among Other Things

    Peter McCloud11/14/2018 at 05:32 2 comments

    One of the advantages to using the Pixhawk is the ability to create custom control configurations. This is necessary for Goliath since it's using a single engine with variable pitch propellers. Previously, having a custom mixer  wasn't necessary since the standard quad mixer worked reasonably well with the variable pitch rotors as the PWM signals map in a similar manner. The downside to using the standard mixer is that the engine speed and thrust are not coupled, which made it difficult to control the engine RPM properly. Now that all four rotors are variable pitch, the thrust and engine speed need to be coupled together, making a custom mixer necessary.

    The process is supposed to be straightforward. You write a custom file, copy it to the SD card and update the configuration file on the SD card to point to the new mixer. After doing all that the rotors stopped working. After a lot of debugging and gnashing of teeth, it turns out there are currently some bugs in the PX4 build (

    The workaround is to add the mixers to the Firmware source code, and flash the updated firmware to the PX4. Makes debugging a slower process as every time I want to make a change, I have to flash the firmware versus directly editing the file on the SD card, but it's working. The issue is supposed to be fixed in one of the upcoming releases, and things can hopefully go back to normal.

    At this point I was hoping to write that I have a new mixer file. Nope, that didn't happen. In the process of debugging the mixer, the Pixhawk is now refusing to arm, giving the error:


    I've tried some of the easy steps to address this, but none of them worked. Since I can't arm, I can't test the custom mixer. So this needs to be addressed before I can finalize the mixer.

  • Dedicated Vehicle Mounts

    Peter McCloud11/02/2018 at 21:28 0 comments

    With a full set of #EVPR: Electric Variable Pitch Rotors completed, the next round of testing is getting close. One item on the to-do list to get ready is having dedicated vehicle mounts. In the past the vehicle was suspended by a loop of rope around the structural frame. Below is the previous setup.

    The issues is that the loops tend to move around, and when the ropes go slack, the rope ends can hit the rotors.

    With a brand new set of rotors, it'd be nice to keep them in good condition. So dedicated vehicle mounts were added.

    The mount is 1" wide and is the same thickness used on the gussets. The black material is a non-slip drawer liner material, to keep the parts from chafing.  No more movement of the mounts and no more impact issues with the rotors.

  • Portland Maker Faire Sept 15th and 16th

    Peter McCloud09/01/2018 at 18:07 0 comments

    Goliath will be on display at the Portland Maker Faire at OMSI on Sept. 15th and 16th. The vehicle has a full set of  #EVPR: Electric Variable Pitch Rotor installed. In addition to the Mk. II vehicle, we'll also have the Mk. I frame on display.

  • OMSI Robot Weekend June 16th and 17th

    Peter McCloud06/01/2018 at 20:00 0 comments

    In the Pacific Northwest and want to see Goliath Mk. II or the #EVPR: Electric Variable Pitch Rotor in person? Come out to OMSI's Robot Weekend on June 16th and 17th. This will be the first time Goliath is displayed with all of the controls integrated into the vehicle. The last of the variable pitch rotors has been assembled and is ready to go on the vehicle.

    Below is a photo with the first two variable pitch rotors mounted.

  • Flight Controller Died, Looking For a New Controller...

    Peter McCloud06/23/2017 at 03:58 5 comments

    Progress is being made the flight controls and the hub for the first prototype was attached to Goliath and spun up to make sure it held together (see #EVPR: Electric Variable Pitch Rotor for more details). There were no issues with the EVPR, there was an issue with the flight controller. When the vehicle was activated, the controller didn't power up properly. The Pixhawk consists on an FMU and an IO board. The IO board power was the only light coming on, nothing else. As a work around for this test, the flight controller was removed and I went back to controller the throttle with just a standard RC receiver directly connected.

    While I can do a little bit more testing without the controller, it's not going to be too long before I need a new controller to start testing the interface between it and the EVPR. However, I'm a little hesitant to get another Pixhawk as I'm not sure what went wrong with the old one. It was about 3 years old, but there was only a handful of hours on it. There were a few rough tests, before I nailed down the isolation on the avionics tray and Goliath had two solenoids go bad, most likely due to vibration.

    I'm familiar with the PX4 flight stack and at least know conceptually how to proceed with modifying the software to work with the EVPR. However there a few controllers that use the PX4 stack including the newer Pixhawk 2.1. Of course it uses different connectors, so the stack of DF13 connectors I have laying around as well as the GPS would be worthless, but maybe it makes sense to upgrade.

    If anyone has any thoughts I'd love to hear them.

  • Control Hardware Starting to Take Shape

    Peter McCloud03/27/2017 at 02:42 0 comments

    Up till now the work on Goliath has concentrated the drive train and the structure. The controls were put on the back burner until the other design problems were addressed. The other items aren't done, but the project has progressed to the point that having a control system would be helpful.

    When Goliath was originally conceived three years ago, the default control scheme was to use vanes underneath the rotors to direct the airflow for control. This was chosen because it was the simplest hardware setup to implement and it's been demonstrated to work for hovercraft. Back in October I started doing some basic calculations to size the control vanes and determine the required servo sizes. Turns out assuming that if it works for a hovercraft, it'll work for Goliath was a bad assumption.

    The issue with using vanes is the rotor downwash velocity. Goliath has a similar amount of horsepower as a hovercraft, but instead of 1 fan, there are 4 rotors, so the power per area is reduced by a factor of 4. Additionally the equation for the force generated by a vane is:

    So if the downwash is reduced by a factor of 2, the force created by the vane is decreased by a factor of four. The end result is that at full thrust, a single vane would have generated only two pounds of force. Which would be grossly inadequate. More force can be generated using multiple vanes in parallel, but the forces would still be low.

    I was discussing this issue with @Benchoff at the OSHW summit, and he suggested using grid fins instead. Doing some back of the envelope calculations show that grid fins should generate enough force. The downside is that the the grid fins have much higher drag, which would reduce the payload or flight time.

    Ignoring their complexity, variable pitch rotors would be the ideal control scheme. Variable pitch rotors would be able to generate larger moment torques than either vanes or grid fins. However, the increased complexity and the fact that Goliath is already a complex project, convinced me not to pursue this.

    However, it's been three years and I really want to see Goliath fly, so I've decided to start building both grid fins and a variable pitch rotor. If I pick one scheme and it doesn't work, then it'll be that much longer before it can fly. So I'll incrementally develop both and see which one works out better.

    Grid Fins

    The grid fins I'll document as part of Goliath as they are relatively straight forward. I have sourced some material to create the fins. The fins will be made from aluminum louvers for florescent lighting. It was difficult finding sheets big enough to make a 36" disc from, but I finally found some 4'x4' sheets (shown below).

    The next step will be cutting out a test disc and placing it under a rotor to determine the control forces generated.

    Variable Pitch Rotors

    The variable pitch rotors are a different story. I had decided not to pursue this until I came across some research that made me realize that it may be possible to create an electrically actuated variable pitch rotor with the servos contained inside the rotor hub.

    I've created a separate project, #EVPR: Electric Variable Pitch Rotor, and I'll be documenting the progress there. I'll be populating more of the design details there, be sure to follow the project if you're interested and want to get updates. Additionally, I think that the project can be useful for other multi-rotors and even conventional aircraft, so I'm entering #EVPR: Electric Variable Pitch Rotor in the 2017 Hackaday Prize. If you think it's worthwhile, but sure to give it a like.

  • Evaluating Aerodynamics

    Peter McCloud03/12/2017 at 00:26 0 comments

    Goliath hovered for the first time in September of 2016. The hover performance was less than desirable since it required a higher throttle setting than hoped and the vehicle did not rise evenly. It tended to favor the port side or the aft. Even more puzzling, was that it tended to lift off first on the side that had the most weight. Ballast could fix the issue, but understanding why is also important. Testing has continued to evaluate the aerodynamics of the setup. Below is a video compilation of some of those tests.

    Test 12 was a simple flow visualization of the rotor downwash. Tufts of yarn were added to the frame to show the flow direction along the radius of the rotor and into the frame. The tufts behaved as expected, with the tufts under the rotor mostly steady. Inside the frame, the tufts indicated the flow reversed and flowed upward due to ground effects. While the tufts wiggled, there did not appear to be anything that suggested any unsteady flow phenomena.

    Tests were also conducted outside to see if the shop walls and ceiling were effecting the aerodynamics. Occasionally in the past, loose debris had been ingested into the rotors and the debris recirculated inside the wake as the flow got turned around by the walls and got re-ingested. Testing outside reduced the re-circulation.

    Test 16 nearly ended up with the vehicle getting damaged. There were four hold-downs, intended to allow the vehicle to move slightly upward, yet remain captive. They weren't made long enough and the hold-downs failed on the aft end of the vehicle. Fortunately, the throttle was reduced in time and the vehicle settled back on the stand (albeit precariously).

    The hold-downs were fixed and the testing continued. During Test 17, the vehicle again lifted up, favoring the port side, but at a reduced throttle setting. However, the test stand didn't allow enough movement for a full hover to be achieved. The test showed that the asymmetries were present, regardless.

    In theory, the rotors themselves should have been out of ground effect as they were at least one diameter above the ground. However, for quadcopters, it may be that the ground effect is dependent on the length scale of the four rotors together and not the length scale of a single rotor. If that is true, then perhaps the port rotors are experiencing higher thrust since they are slightly closer to the ground. It's difficult to tell exactly. This may be why the Mallory Hoverbike has the offset rotors catty-corner from each other.

  • Mitigating the vibrations

    Peter McCloud12/12/2016 at 05:04 0 comments

    I'd hoped to be well into working on the controls on Goliath by now, but the shorter days and colder weather mean less time in the shop. I'm still nailing down some lingering issues with the drive train. The new pulleys are weeping grease because the bearings are getting too hot. I suspect it's because I'm using all thread axles and nuts to keep the bearings in place. I'm working on building the proper axles and axles mounts to go with the new pulleys.

    Meanwhile I wanted to document the progress made on mitigating the vibrations that the avionics experience. This was accomplished by better isolating the engine from the frame and the avionics tray from the frame. The new engine mounts are made primarily of rubber, but are built such that if the rubber fails, the bolts are still captive. Stainless steel bolts are used to attach the mounts.

    The avionics tray was switched from aluminum to steel. This was to add mass to help reduce the displacement of the avionics tray. Below is the new tray with some of the avionics populated.

    The tray is mounted to the frame using four Expansion Nuts. I forgot to take a picture of them before I installed them, so here is a link. Below is a shot showing the flange on the expansion nut between the tray and the frame.

    So how much did all the changes help? Data from the Pixhawk shows a huge reduction in the pitch rates down by a factor of 5 to 10. This means that the Pixhawk should be able to control Goliath once the rest of the hardware is complete.

    Hopefully the next log update in the not too distant future will be about fixing the bearing issues.

View all 79 project logs

  • 1
    Step 1


    Before you start this project, take some time to REALLY think about what you're about to build. Seriously, this is a flying machine that weighs more than most people and runs on gasoline, a chemical that the states of Oregon and New Jersey have deemed too dangerous for the average citizen to pump into their own car.

    While Goliath is a big and powerful, it's only as dangerous as the user. As you build, test and fly your giant quad copter be mindful of your safety and the safety of others.

  • 2
    Step 2


    Building the composite pieces requires the longest amount of lead time. It's recommended to start these pieces first, and the rest of the components likely be built while waiting for the composite pieces. Components made from composites are:

    • Propellers
    • Ducts
    • Control Surfaces
  • 3
    Step 3


    Tools - Miter Saw, Jig Saw or Tin Snips, File, Drill with #30 drill bit,Rivet Puller

    A) Build the Jig for the Upper Frame

    To properly build the frame, jigs are required to hold all of the frame elements in place. The jig is constructed from particle board. Below the completed jig is shown with the upper frame elements in place.

    B) Cut the Upper Frame Elements

    Using a miter saw, cut all of the frame elements and place them in the jig to ensure a proper fit.

    C) Cut the Common Gussets

    Cut the common gussets (4 A & 4 B), layout and drill the holes with the #30 drill bit.

    D) Assemble the Upper Deck Elements

    1) Remove the frame elements for the upper ring, leaving just the pieces for the upper deck

    2) Clamp the common gussets in place and drill half of the holes into the frame. Use Clecos to fill in the holes as you go.

    3) With half of the holes filled with Clecos, drill the remaining holes and fill them with rivets.

    4) Remove the Clecos and fill in the remaining holes with rivets.

    5) Remove the upper deck from the jig, flip it over and place it back in the Jig

    E) Cut the Corner Gussets

    F) Assemble the Upper Ring

    1) Place the remaining frame elements back in the Jig

    2) Attach the corner gussets

    G) Join the Upper Ring to the Upper Deck

    1) Cut the Angle Gussets

    2) Attach each of the angle gussets

    The Upper Frame is now complete and can be removed from the Jig

View all 11 instructions

Enjoy this project?



Marcio wrote 07/24/2020 at 17:58 point

Hi Peter! Could you have used bigger propellers if you wanted, or are the propellers size already maximized for that 30 HP engine?

  Are you sure? yes | no

Peter McCloud wrote 12/29/2020 at 13:42 point

Thanks for the question! The current rotors, 36", are as big as they can be for the 30 HP without speed reduction. For the Mk. III vehicle, a speed reducer is planned to allow for 42" rotors.

  Are you sure? yes | no

philips170t wrote 04/02/2019 at 09:41 point

is this project still ongoing?

  Are you sure? yes | no

Peter McCloud wrote 06/05/2019 at 16:34 point

Yes! Work is about to begin on the Mk. III version of the vehicle.

  Are you sure? yes | no

justin.yang777 wrote 03/26/2017 at 03:41 point

Oh wow! Just found this project here and I remember seeing this at OMSI during the maker faire! Great to see how much it has progressed since then. :)

  Are you sure? yes | no

Peter McCloud wrote 03/26/2017 at 23:21 point

Awesome! Thanks. Hopefully we'll be back at OMSI again for this year's PDX maker faire.

  Are you sure? yes | no

Robert McClintock wrote 03/06/2017 at 18:13 point

This is a cool project. When you were building this did you use a Design program when drawing this thing out? Or was this all built from experience? The reason I am asking is because its for college course I am taking. I'm wanting to build this for my CAD project and know if had any previous info like dimensions for the frame? Well, thanks for reading and I will be being staying tune in for project updates.

  Are you sure? yes | no

Peter McCloud wrote 03/21/2017 at 19:08 point

Robert, thanks for the interest in this! I'm sorry I didn't respond earlier, I never got notified about this comment.

I hope its not too late to do this for your project. I've got coordinates for the frame buried in the github repo. I'll PM you and we can get in touch.

  Are you sure? yes | no

charles wrote 12/26/2016 at 10:56 point

Have you considered using a variable speed pulley system and an actual quadcopter stabilizing software and hardware setup to control the amount of speed each pulley produces? Servos and actuators incorporated along with tensioners to increase and decrease the amount of speed that each pulley system produces. There are many manufactures of these belts and pulley sets. I personally think that would be the best solution to be able to maneuver this craft safely.  If this helps your quest to make a gasoline powered quad please inform me about it. You would need 4 sets of these to manage the quadcopters prop speeds. Or you could even use a small electric motor design that manages the amount of tension either with screw type management or offset tensioner pulley on the electric motor that changes each belt according to its thrust using the quadcopters hardware. But the reaction time would suffer greatly by using a screw type actuator just saying that for reference.

  Are you sure? yes | no

RX HMP wrote 10/03/2016 at 19:43 point

Brilliant. I was thinking why is there nothing modern like this lol. im new to flying but not rc. Its been a while though. I wanted to know were you are? Woud love to get involved.

  Are you sure? yes | no

jd_jaidev94 wrote 09/21/2016 at 13:00 point

If money was no issue, what engine would you use and in combination with what motors and props? Can heavy payload and long range flight be possible with gas powered engines and electrical motors?

  Are you sure? yes | no

Peter McCloud wrote 09/22/2016 at 10:29 point

If money was no issue, I'd probably try to make my own engine along the lines of #Open Source Two-Stroke Diesel Engine. There are engines out there with higher power to weight ratios, but the peak power RPM isn't optimal, so additional gearing is needed.

For props carbon fiber would give you the lightest weight and if money is not an issue, you could just get 4 variable pitch tail rotors from a helicopter.

  Are you sure? yes | no

Carl Mueller wrote 07/02/2016 at 22:34 point

As far as a control system, you could just treat this as a singlecopter.  The fact that it has 4 rotors instead of one is not really material, since all give the same thrust.  The implication is that (a) you only need 4 vane controls, and (b) it's already available in Ardupilot.

  Are you sure? yes | no

Peter McCloud wrote 07/04/2016 at 02:40 point

I hadn't thought of it in terms like that, but you're right. It looks like there is one difference between Goliath and the Ardupilot singlecopter setup. Goliath is setup as an X configuration vs the Ardupilot singlecopter + configuration. Regardless, it should be something that can be adapted. Thanks for the excellent insight!

  Are you sure? yes | no

TTN wrote 05/26/2016 at 01:46 point

I guess its easier to just test with new pulleys at this stage, but I was just wondering if you have considered using a 2 or 4 stroke motorcross bike engine? Light weight, high power, somewhat pricey, but not impossible to purchase. The engine units are generally well separated so the transmission part of the engine can be milled off the engine. Either way its a lot of work to do an engine swap. I can see a lot of work has gone into this project!

  Are you sure? yes | no

Peter McCloud wrote 05/26/2016 at 03:58 point

Eventually a different engine would be ideal. I had not looked at motocross engines, I'll have to add that to the list. One reason I've stayed with the current engine is that it's inexpensive and if the vehicle crashes I'd rather lose this engine.

  Are you sure? yes | no

Poppy Ann wrote 01/20/2016 at 08:44 point

did you consider using a set up similar to :- 

which uses only one motor and then uses constant speed propeller blades that use the same system that helicopters use to alter the pitch  to adjust the lift of each corner?

I have been thinking of building a similar design of one power system but using one of the Honda silent generators for power then either still using separate motors at each blade or a single motor and belt drive like the Hobbyking Assault Reaper quad.

Regards Poppy Ann.

  Are you sure? yes | no

Peter McCloud wrote 01/21/2016 at 00:10 point

That's been talked about a couple times in the comments. Essentially, it's a whole other project in itself to build adjustable pitch propellers. Once Goliath is flying I may investigate it then.

Thanks for pointing out the typo. I fixed the error in the instructions.

  Are you sure? yes | no

Poppy Ann wrote 01/20/2016 at 08:36 point

Hi who did the editing of this page? I am dyslexic and noticed one obvious mistake as soon as I read it ie:- "Oregon and New Jersey have deemed too dangerous for the average citizen to handle putting their own car."

where is the average citizen trying to put their car that is so dangerous ? or did you mean :- "Oregon and New Jersey have deemed too dangerous for the average citizen to handle putting in their own car."

Regards Poppy Ann.

  Are you sure? yes | no

ken wrote 12/01/2015 at 16:21 point

Increase the diameter of the pulley on the motor and add a centrifugal
clutch to allow the engine to start and addle be for engage the propellers this
will allow higher rpm to the propellers. Do this till the motor can’t increase
to the max rpm than back off a little this will tell you if the motor is too
small. I don’t think it is you just need to get the rpm’s up on the propellers.

And put a cage around it when you test it. I don’t think
your propellers will withstand the rpms needed for lift off. If one breaks very
bad news for ever who is around.

  Are you sure? yes | no

Peter McCloud wrote 12/15/2015 at 14:40 point

Any recommendations on specific clutches? I looked around for one that would work my Goliath about a year ago and I didn't find any.

Thanks for the concern about safety. When Goliath is being tested, there is a safety net that is put up, and everyone is behind a big steel tool cabinet. There are some pictures of the safety net in the project logs.

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goldenshuttle wrote 11/04/2015 at 07:05 point

Great project. Have you taken a run on each part to reduce total weight ?

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thesunman84 wrote 09/05/2015 at 15:16 point

From my experience in the structural world, might I suggest adding a washer under the bolt head to distribute force evenly?  Right now, it looks like most of your bolt heads are only gripping a very small amount of the galvanized steel.  You are best off using a flanged nut with a washer under the bolt head.  I know you're trying to cut weight and washers won't help that but neither will a bolt head pulling through steel :)

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Peter McCloud wrote 09/11/2015 at 14:40 point

Thanks for the link and the suggestions.  I'll have to keep that in mind as I continue to develop the vehicle

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Aaron Cooper wrote 08/26/2015 at 21:04 point

Have you looked into lightening the engine itself? some features like the fuel shutoff solenoid are potentially un-needed as those were added to prevent a bad needle valve from flooding the engine during storage.  The various covers are potentially replaceable with lighter weight parts.  I was briefly interested in using a weed eater engine to power a RC plane, there is a community dedicated to modifying small engines for RC use. I believe some of them modified or replaced the flywheel to make it lighter.

  Are you sure? yes | no

Peter McCloud wrote 08/27/2015 at 14:24 point

All good thoughts. I haven't concentrated on that area yet. I would like to leave the solenoid in to be able to shut off the fuel source in case there is an engine fire. It's a common practice for aircraft, though it's probably pretty unlikely that I'll have an engine fire and still be able to command the fuel to shut off.  The fuel solenoid is pretty small, so it'd not too big of a weight penalty.

The plastic covers would be fairly easier to replace. I could make molds off the existing ones and replace them with fiberglass.

I'd love to get a lightweight flywheel for the engine, that's probably be the most beneficial and it's relatively easy to swap out. I haven't found any out there for my particular engine model.

If you could share any links to the specific RC groups you mentioned that'd be great.

Thanks for the inputs!

  Are you sure? yes | no

Aaron Cooper wrote 08/27/2015 at 19:14 point

Below is one site that has a bunch of info, they focus on the smaller engines but a lot of it should apply. Also a site that has parts that may be compatible or at least copy-able design wise for your engine.

  Are you sure? yes | no

michael.rodenbarger wrote 07/21/2015 at 14:21 point

Very interesting! Great job thus far :).
Have you thought of using 2 stroke motors at all? You can generally get more power out of a lighter 2 stroker vs a 4 of the same size. How about using crankshafts instead of a belt driven system? Weight can be reduced with creative use of materials (carbon fiber or fiberglass shafts).

  Are you sure? yes | no

Peter McCloud wrote 07/21/2015 at 21:19 point

Hirth makes an experimental aircraft engine that weighs the same as engine currently being used, but has more than 3x the HP. The issue is that it costs 10x the current engine.

The real issue with drive shafts isn't the shafts themselves, but the gears required to make them work.  I haven't found gearboxes that can support the Hp and are light enough.

Thanks for the interest in the project!

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surubarescu wrote 05/25/2015 at 08:49 point

I have some suggestions: for the belt pulleys you can use some with slightly barrel shape that will self center the belt (like on band saw), yet giving the power transmitted, the pulleys should have shoulders to keep the belt flying. Or you can use a transmission box like two mikey mouses heads connected at the neck: two big gears, one connected to the engine, the other used to reverse the rotation, and for each one 2 smaller gears to send the power to the propellers using shafts (either  via 2 sets of conic gears if the engine and propellers are level, or if the engine is very low shafts with universal joints). 

Almost forgot: this thing will have a gatling gun turret under it?

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Peter McCloud wrote 05/26/2015 at 19:49 point

Maybe I can add a paintball Gatling underneath and put it up against this guy:

As far the the barrel shaped pulleys belts go, I'm using those for the flat sided idlers.  All the toothed pulleys are flat faced, but they all do have shoulders.  You can't have the barrel shape and still maintain the right tooth profile.

I did look into gearboxes as well, but they are too heavy for what I need.

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surubarescu wrote 05/27/2015 at 07:55 point

Nice mech, but the driver is protected by chicken wire. You won't get a clear head shot, but you'll spray it well with paint. 

Let me draw you a little picture of how i see this "gearbox" (better said a collection of gears) [you'll need to view it using fixed font - paste it in notepad]

propeller                       |               propeller
----+-----            _____   __|__             ----+-----
    |                |  |  | |  |  |                |     
   _|_               |__|__| |__|__|               _|_    
   \|//|           |\\  |  / \  |  //|           |\\|/
      --------------- -----   ----- ---------------
      \|           |/               \|           |/

|  |  | this is a combination of cylindrical and conical gear
|__|__| the cylindrical part engages the other identical gear
\  |  / the conical engages the shaft conical gear
 -----  for each of these gears there are two shafts for two propellers
The only issue is that you'll have adjacent propellers rotating in the same direction (but you already choosed this configuration). You can also use sliding shafts to counter the bends in the propellers trusses.

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Rollyn01 wrote 05/25/2015 at 01:41 point

You ever thought of expanding this to build an actual factual flying car?

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Peter McCloud wrote 05/25/2015 at 03:21 point

Yes. I originally wanted to build a quadcopter large enough to carry a single person. However getting a more powerful engine and the hardware to go with it would have been expensive. I chose to make a smaller (relatively) prototype to test out the technology needed  before  going bigger. 

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Adam Fabio wrote 01/15/2015 at 05:57 point

Awesome work Peter! The wider belts do seem to be working out pretty well. I've made the same mistake leaving the screw out of a servo. I bet you needed a change of shorts after the unexpected jump to full throttle!

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Peter McCloud wrote 01/17/2015 at 03:00 point

When it happened, it seemed to be at full throttle for a while before I killed it, but after watching the video, it seemed much shorter. That's what adrenaline does I guess.

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dwardio wrote 12/03/2014 at 16:42 point
Very interesting project! Like many others, I'm curious as to how controlling thrust direction will replace variable prop pitch or speed.

Also, what is the estimated full-up weight at take-off? Current AMA guidelines are that any model weighing in at more than 50 pounds should be registered as an experimental aircraft. Needless to say, this bad boy is going to be potentially lethal, making sure you're within the rules is a good investment.

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Peter McCloud wrote 12/04/2014 at 22:31 point
Thanks for the interest! I'm hoping to have a gross takeoff weight of 240 lbs, with 40 lbs of payload capacity. Your right, Goliath can be hazardous and this is not something you simply take to the park and fly around.

Your right, knowing what the rules are is a good investment. I'm curious if you happen to have a link to the guidelines you're referring to. I did some looking and found AMA document 520A ( It simply states that AMA Large Model Aircraft 1 (LMA1) can be from 50 to 77.2 lbs and LMA2 can be from 77.3 to 150 lbs.
I did find a reference to the IMAA guidelines that states:
"IMAA qualification also requires the RC model be a maximum weight of 55 pounds, with fuel – ready to fly. Models over this weight up to 100 pounds, with fuel – ready to fly (known as Experimental Radio Controlled Aircraft) may also qualify as IMAA giant scale provided they have a Permit To Fly signed by an AMA certified “Experimental Inspector”"

My understanding is that drones are currently certificated by the FAA, and the guidelines that they are working on will be valid for 55 lbs and below. So this leaves Goliath in a questionable area. I'm not sure where I'll be able to fly it once it is flying. For now I'll just have to worry about it once I get Goliath flying.

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