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Goliath - A Gas Powered Quadcopter

A BIG Gas Powered Quadcopter

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This project was created on 05/25/2014 and last updated 4 days ago.

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


Goliath is a prototype vehicle for developing large scale quadcopters. The design is based on a single central gas engine with a belt drive providing power to the four propellers. Control is done using control vanes placed under the propellers. Each propeller is 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 were used. It's currently a work in progress, and even when completed it's intended as a starting point for future vehicles.

THP Semi-Finalist Video

Flight control will be performed using the Pixhawk controller running a modified version of the Ardupilot flight software. Modifications to the Ardupilot software are needed to work with Goliath's unique control system. Both the Pixhawk and Ardupilot are open source. The modifications made will be open source as well. A USB radio receiver will be attached to the flight controller and setup to receive ADS-B signals. These signals will allow the operator to be aware of other aircraft operating in the area.Additionally Goliath will have a WiFi interface allowing the public to interact and connect with Goliath. Data and Video Feeds will be available and observers can notify the operator of potential issues.


An electric powered design would have been the most straightforward approach. Electric motors are more efficient than gas, but the power density of gasoline is much greater than today's batteries. So until battery technology improves, gas power seemed the way to go. Goliath uses a single 30 Hp engine and a belt system to transfer power to the four propellers. The setup was chosen because at this scale, four smaller engines have a smaller power to weight ratio than a single larger engine.

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.


The frame is 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. At a later stage when the configuration is finalized the dexion could be swapped out for a lighter weight frame.


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 are powered using a battery elimination circuit that provides 5V @ 10 amps. Solid State Relays are used to control the engine using the Pixhawk.

  • 1 × 30 HP vertical shaft gas engine Should equipped with a starter and alternator
  • 1 × Pixhawk Open Source Flight Controller
  • 1 × Raspberry Pi WiFi Interface
  • 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)
  • 8 × Control Vane (37" Wide) See Detailed Build Instructions for Raw Materials (Forthcoming)
  • 8 × Control Servo
  • 1 × Throttle Servo
  • 1 × Main Pulley (50 mm wide) HTD Pulley 50 mm wide,34 teeth, with QD Bore (Type SH)

See all components

Project logs
  • First Custom Pulley Finished

    4 days ago 1 comment

    The first of the custom pulleys was completed today. The custom pulleys are aluminum instead of steel and allow for six fitted mounting bolts instead of three fully threaded bolts. Here's an image of the new custom pulley connected to one of the previously used rotors.

    The custom pulleys are started from a 10" length of pulley stoc. Below is the stock mounted in the lathe.

    I won't go through all of the steps here. The manufacturing steps were outlined in the previous log and updated to reflect the as-built process. All of the photos showing each of the steps are in a Flickr album. Here's a shot showing the part after the machining was complete:

    Next, the flanges were put in place and a punch was used to roll over the edge in six spots to hold the flange in place. The bearings were press fit in place.

    Here's a shot with the six bolts holding the rotor in place. I'm confident this will solve the issue with the bolts breaking.

    The next step is to mount the new pulley onto Goliath and run a test to ensure that it doesn't have any issues. If that test is successful, then the other rotor pulleys can be manufactured.

  • Designing Custom Rotor Pulleys

    11/07/2015 at 21:09 1 comment

    One of the goals of the project is to use as much off-the-shelf hardware as possible. The prior rotor pulleys were standard pulleys and readily available. A few of the issues with the prior pulleys were that they were made of steel and required a separate steel bushing. While aluminum pulleys can be purchased, they have to be custom ordered.

    How Timing Pulleys are Constructed

    There are several examples across the Interwebs about how to build timing pulleys and in particular HTD pulleys. Building a single pulley or a small batch of pulleys can be done with machine tools. Below is a good example by DIYisFun building a small pulley from a block of material on a mill.

    Another way is to use a fly cutter to create pulley stock from a block of material. Here is another video from DIYisFun showing how a fly cutter is used to create a timing pulley.

    This method is a bit time consuming. A good compromise is to purchase the raw pulley stock and cut the pulleys from the stock. This will only require basic machine tool operations. Aluminum stock of different sizes and pitch can be readily purchased.

    One last consideration is adding flanges to the pulleys. The flanges are required because the belts operate in a horizontal position. The flanges can also be readily purchased with the pulley stock, but there are several methods of attaching them. The prior pulleys appear to have flanges attached using a method called roll staking. Here is a video showing how roll staking is done.

    The roll staking requires special equipment, so the options are either to use bolts to attach the flanges or use a punch to do conventional staking.

    New Rotor Pulley Design

    Making the rotor pulleys isn't as simple as lopping off a piece of pulley stock. The rotor pulley has to accommodate the flanges, the bearings and the rotor bolts. Below is the CAD design of the pulley with 6 fitted 1/4" diameter bolts, 4" long.

    Machining steps:

    • Mount pulley stock
    • Cut 1st shoulder to 1.77" radius 0.22" wide
    • Cut off the length of pulley from the pulley stock (1.60" wide)
    • Remount using 1st shoulder
    • Cut second shoulder 1.77" radius 0.15" wide
    • Bore center hole
    • Bore 1st bearing pocket
    • Face Surface
    • Remount using second shoulder
    • Bore 2nd bearing pocket
    • Face Surface
    • Drill bolt holes

    Any feedback on the pulley design or tips on doing the actual machining would be appreciated.


    The new pulleys should weigh about 1.3 lbs and the previous pulleys weighed 2.6 lbs so the total weight reduction for the four rotor pulleys will be at least 5 lbs. There will likely be further weight reductions since the bushings are being eliminated as well. Finally, having the six fitted bolts vs. the three fully threaded bolts will solve the rotor bolt issues.

  • Latest Tests Completed

    11/06/2015 at 23:18 0 comments

    The latest testing with the new rotors has been completed. However, Goliath still isn't flying. Most of the testing was troubleshooting Goliath after reassembly. It seems that a few tests are always required to get everything setup up correctly when Goliath has been reassembled. Below are the videos of the latest testing, then a description of what changes were made and what's next.

    Tests 22 & 23

    Mostly troubleshooting Goliath after reassembly, securing hardware and getting the belt tension correct. Increasing the throttle above idle has little effect.

    Tests 24, 25 and 26

    More of the same. Finally got the belt tension correct for test 26, but the propeller bolts fail toward the end of the test. The engine was still mostly unresponsive to throttle settings above idle.


    New Rotors

    A brand new set of propellers were manufactured since Test 21. The angle of attack at the tips was decreased to change the power vs. RPM curve to better match the engine. The new propellers should require less power at lower engine speeds, allowing the engine to rev up to higher RPMs. The new set of rotors is shown below.

    Propeller Bolts

    During prior tests the bolts attaching the rotors to the pulleys have broken on a few occasions (see prior project logs). The bolts are supposed to merely hold the bushing to the pulleys, but have been replaced with longer bolts that serve to also attach the rotors. This time around the original bolts were put back in and a new set of bolts were added to attach the rotors with. The purpose of doing this was to decouple the loads required to hold the bushing to the pulley together and the loads from the rotors. The new rotor bolts were epoxied with JB Weld into empty holes already present in the pulleys. Below is a picture of the bolts being epoxied in place. the nuts and washers are on the bolts to hold them in place.

    Obviously this didn't work. Two of the bolts were broken off and one of the bolts was pulled out of the hole. It's difficult to tell exactly what failed first. I suspect that the bolt that got pulled out of the hole didn't have a strong bond and failed first. The load on the other bolts increased, subsequently causing them to fail. Of course it's possible that one of the other bolts broke first and then the rest failed.

    Choke Servo

    Before test 21, a second servo for the choke was added, but until a few weeks ago the linkage hadn't been connected. Now the linkage is connected to the choke lever. Below on the right is the throttle servo and on the left is the choke servo.

    Connecting the linkage was problematic because the air intake is in the way. Below is a photo with the upper ball link installed and the tight clearances around the linkage. On the right is the side of the carburetor and on the left side is the air intake.

    In order to get the nut on the linkage, a special wrench was required:Having the choke servo made starting the engine much easier. Previously starting the engine involved closing the choke, running the engine for 30 to 60 seconds to warm it up, shutting down, then setting the choke to open and then performing the actual test.

    What's Next

    Fixing the rotor bolt issue is the biggest item that needs to be resolved. So far the measures attempted accommodated the existing pulleys. It had already been apparent that custom rotor pulleys made out of aluminium would be needed to decrease the weight. Making these new pulleys is now on top of the list. Designing the pulleys is still in work, but the new pulleys will likely have six bolts instead of three. The new bolts will also be fitted bolts instead of fully threaded bolts (as @mechanicalsquid has discussed). There will be a project log in the future detailing the custom pulley design.

    More data is also needed to figure out the engine issues, particularly engine RPM. There is already a hall effect sensor installed to sense the magnet built into the flywheel. It just needs to be utilized now to sense the engine RPM....

    Read more »

View all 50 project logs

Build instructions
  • 1


    Before you start this project, take some time to REALLY think about what your 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 handle putting 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 quadcopter be mindful of your safety and the safety of others.

  • 2


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

    • Propellers
    • Ducts
    • Control Surfaces
  • 3


    Tools - Chop Saw or Reciprocating Saw, File, 5/16" Sockets and Wrenches

    A) Cut the Frame Pieces

    Start by cutting the all of the galvanized slotted angle pieces to the correct lengths using the cutting guide. A chop saw or a reciprocating saw are the best choices. All of the cuts are intended to be across the center of the nearest hole and the exact lengths won't matter as long as the correct holes are used.

    Afterwards be sure to file all the edges and corners.

    The pieces after being cut are:

    • 4× Center Beams ( 2 1/2" x 1 1/2" x 39 3/4")
    • 4× Side Beams ( 2 1/2" x 1 1/2" x 29 1/4" )
    • 4× Cross Beams ( 2 1/2" x 1 1/2" x 30" )
    • 4× End Beams ( 2 1/2" x 1 1/2" x 18" )
    • 8× Outer Prop Supports ( 1 1/2" x 1 1/2" x 30 3/4" )
    • 4× Inner Prop Supports - Fore ( 1 1/2" x 1 1/2" x 28 1/4" )
    • 4× Inner Prop Supports - Aft ( 1 1/2" x 1 1/2" x 32 1/4" )
    • 8× Shaft Mounts - ( 2 1/2" x 1 1/2" x 6")
    • 4× End Cross Bars ( 1 1/2" x 1/16" x 18" )
    • 4× Side Cross Bars ( 1 1/2" x 1/16" x 30" )
    • 1× Battery Plate ( 2 3/4" x 1/16" x 11 1/4" )

    B) Assemble the Top and Bottom Decks

    Follow steps B1 and B2 for each deck

    Note: The frame assembly uses only 5/16" bolts. All of the bolts, lock washers and hex nuts referenced will all be 5/16"

    1) Bolt the (2) Center Beams and the (2) End Beams together using (4) bolts, (4) lock washers, (4) hex nuts.

    2) Bolt the (2) Cross Beams to the (2) Center Beams using (4) bolts, (4) lock washers, (4) hex nuts.

    C) Join the Top and Bottom Decks

See all instructions

Enjoy this project?

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.

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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!

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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.

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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).

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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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Rebelj12a wrote 11/10/2014 at 21:31 point
Odd thought, are you still having stability issues...

I wanted to make a gas powered one for more sustained flight anyways. Current electric quadrocopters dont have alot of flight time especially for heavier things.

I dont know if this will work, however it might...

One, place a direct porpeller on the motor itself. Primary lift comes from the center of the craft.

Recess the center motor further down, i.e. angle the quad rotors upwards by maybe... 20 Degrees 30 degrees?

Add brushless propeller motors on the ends of the quadrocopter.

Heres the "if" and I dont now if it will work... See if you can find an alternator and a flight controller. There are lots of electric ones, although it may need to be retooled but this will allow you to balance the quad with the brushless motors. The motors would be powered by the gas engine turning the alternator, well besides the initial first charge.

At the most maybe, it would need to be tuned to stay afloat, however instead of the rotors providing primary lift the engine would therefore making it more powerful and using the rotors for stabilization and guidance using the flight controller. That may need to be tuned im sure the physics are different. Although with the *hanging* design of having the motor propeller and camera/gimbal lower it should make stabilization a bit easier.

A thought I had bouncing around. In any case thought i'd throw it your way, never know.

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Peter McCloud wrote 11/11/2014 at 18:19 point
Thanks for the inputs. This is what I feel is all about, so please keep the inputs coming. The issues I've been having are oscillations with the belts themselves, I hope I have it fixed, but I haven't tested out the latest config.
A hybrid design would be nice, it certainly would solve the issues of having belts. I haven't done the math as to how much power I would need to maneuver using electrical power. The engine is already equipped with an alternator, so it'd just be extra weight of the control motors. Something to think about if the current fixes don't work out. Thanks!

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Rebelj12a wrote 11/12/2014 at 10:32 point
Possibly add an adjustable belt tensioner? Similar to this.

Also for fairly decent cheap parts this place is the place to look. Couldnt believe the prices so i'd question the build quality long term however for a working concept and for ideas on what to look for. This place has got the parts.

Also the idea to lower the engine and main rotor a bit came from here.

Look at the very bottom, theres the degrees of inclination. The lower center of gravity at the center as well makes it more stabile. Also.....

If you were to go with a single gas propellery and smaller control engines on the outside. I would use a propeller with a center connect and outside connection ring. Fix the propeller inside a round shell. That way it would have the stability if you wanted, to even attach the 4 control engines above the main main blade itself. It might offer a bit more stability as well, keeping the propeller blade from oscillating, attached to the motor.

Also for safety reasons too XD

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Peter McCloud wrote 11/13/2014 at 01:31 point
I have added spring loaded adjustable tensioners, that I built from scratch. They can be seen in the video link here.
Hopefully the remaining issue was having the pulley flanges setup right. Hopefully I'll find out it's all right with the next test.

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Rebelj12a wrote 11/13/2014 at 03:08 point
Oooh oh I dont know about springs. Makes it bouncy thats not good. I would have use screw adjustible ones you can lock into place. Especially because depending on temperature and wear the belts will loosen and tighten (dont know about you but its getting cold here XD)

If all else fails. I highly suggest looking at a chain based solution. Grab a couple old bikes for the gears and chains from thrift or garage sales.

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Rebelj12a wrote 11/12/2014 at 21:16 point
Also, of note on the page I linked is the motors they use and the kg of force they exert for flight.

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PointyOintment wrote 11/11/2014 at 22:47 point
I dont know if this will work, however it might...

Like this?

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gnoejuan wrote 10/17/2014 at 22:18 point
What i see here is a flying lawnmower. And that's exactly how I'd use it.

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Dave Hermeyer wrote 09/30/2014 at 11:11 point
I'm glad that you put a disclaimer "Think before you start" at the beginning of your instructions, but you go on to say "it's only as dangerous as the user". That's exactly the problem! There's plenty of fools out there, and I'd hate to imagine one of these machines in their hands. And what happens when you have engine problems in mid-flight, or a belt breaks?

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Peter McCloud wrote 09/30/2014 at 20:09 point
Yes there are people out there who could do bad things with Goliath, but there are many other things that they can get there hands on as well that'd be dangerous.
Once I start flying more than a few feet off the ground I intend to install a ballistic recovery chute. In an emergency the parachute is shot out using compressed gas or a rocket. There are some sized for ultralight aircraft. So that would be ideal. It'd be nice to have redundant belts, but I don't think there's enough weight margin for that.

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michaeldlewandowski wrote 10/17/2014 at 17:41 point
I am interested in designing/ building a recovery system for this monster! I have emailed you.

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Peter McCloud wrote 10/19/2014 at 02:07 point
I look forward to hearing about your ideas. I'll contact you soon!

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Mike Berti wrote 09/30/2014 at 02:35 point
This is by far one of the most compelling quadcopters I've seen to date.

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Peter McCloud wrote 09/30/2014 at 20:04 point
Thanks Mike!

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CHOPPERGIRL wrote 09/17/2014 at 01:59 point
Im designing my own heavy copter drone. Several points just looking cursorarily at your build out:

1. Placing your heavy motor on the top makes it inherently unstable. Far superior would be placing it underneath the center of gravity, not above it. The difference in stability is between either balancing a basketball on your finger tip (your design) or suspending a basketball from your finger on a string (like a helicopter with the aircraft body below the main rotor).

2. Hexa would be more failsafe than quad. On a hexa if two (or even 3) props go out, assuming the software can detect and compensate for the loss, the thing can remain stable and keep flying (long enough to return to a safe landing).

3. Your frame and engine look too heavy. You may be over building a lot of it, and galvanized steel and a heavy cast iron engine block may kill your efforts to get airborne. Look into ultalight aircraft engines or even mor advanced stuff. Yours looks like a generator or lawnmower engine which is designed for an application where engine weight is irrelevant. But for you, engine weight is VERY relevant.

4. You need a way to individually control rotation to each prop. Consider a fluidics type transmission. Basically, your engine is attached to a pump and creates continuous water pressure. If no torque is needed to any props, the water (or oil) recirculatesgoes around in a continous loop. If a prop needs torque, a valve shunts water into it in varying degrees to a reverse pump that drives the prop. In this way you could control all props variably instantly... and the motor would run at its optimal constant speed.

5. I myself want to buildone large enough to be controlled by and carry a pilot underneath. So I'm thinking even larger than your design...


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zakqwy wrote 09/17/2014 at 02:34 point
You should post your design to! Definitely interested to see your project.

I'd counter point (4); pumps are heavy. Hydraulic motors are heavy. Control valves are heavy. I could see using this for control surfaces (like an airplane), but the flow rates and pressure requirements needed for the propellers would make such a system difficult to integrate into a flying platform.

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Peter McCloud wrote 09/17/2014 at 21:33 point
I agree with Zakqwy, you should post your project to I'd like to go bigger as well, but this is step 1. In regards to your comments:
1. Yes it does make it unstable, but I haven't found a light weight way to do sling the engine underneath. The electronics will at least address the stability. Goliath should at least be slightly more stable than Gimbalbot ( :p
2. Going to hexa is an intriguing idea, but since Goliath theoretically has a extra thrust margin of about 10%, even going to hexa wouldn't help much. It still just fall fast.
3. Yes mass is the number one issue in making sure Goliath works. I've traded heavier mass for reduced cost and effort for Goliath, because I know there is going to be a learning curve and I'd rather wreck a this design and learn a few lessons than a higher performance and higher cost vehicle.
4. I actually did research doing a hydraulic design and as Zakqwy pointed out, it does get heavy. The pressures involved lead to very heavy motors and at least at the scales I looked at, it didn't work out. I also looked at the same concept using pneumatic design which was also interesting, but there's a lot of energy losses with the expanding air and there would need to be some sort of thermal recovery system.
5. I'd love to see your design! I've gotten great feedback from the community here at Hackaday Projects.

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PointyOintment wrote 09/18/2014 at 02:15 point
Placing your heavy motor on the top makes it inherently unstable.

This is not true:

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J Groff wrote 09/06/2014 at 20:19 point
That is quite a software thicket there sir. Have you considered abandoning the 'Arduino Way' and going for Atmel studio with JTAG/ISP through an inexpensive programmer like JTAG/ICE. Source level debugging and more available memory (no bootloader) and you get to use the USB port on the board. As you may have discovered the core of the Arduino platform is thin and they do stupid things like hogging timers for beeps and unnecessary delay functions. Unless you really want the IDE backward compatibility, but then it seems you had to fork that as well. I ended up doing it this way so I can speak to the benefits. Good luck.

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Peter McCloud wrote 09/06/2014 at 21:46 point
I do some programming, but haven't done any on a microcontroller yet, so almost all that went over my head in the first read. After googling most of what you wrote, that sounds pretty intimidating. (This coming from the guy who's testing a giant gas powered quadcopter in his driveway).
Now that I've done a bit of research, I agree with you that it would certainly make sense to go the Atmel studio route, especially for follow on versions of Goliath, and have an optimized bit of software. I do like the ideas behind the Ardupilot software and would like to contribute to their community. Also the singlecopter (
has demonstrated the control system route that I'd like to do, so I can possibly leverage the Ardupilot software already written for that.

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J Groff wrote 09/08/2014 at 22:08 point
Sorry. I guess a distilled version of that would be: you have so much code there that you might consider doing it the way the professional embedded systems developers do it with single step debug and viewing memory/registers etc instead of the way hobbyists do it Arduino style with printf and such ;] You can still use all the Arduino libraries this way, which is the bulk of what 'Wiring' really is. I think their platform is great for little one-offs but at a certain point you need real tools.

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Smerfj wrote 09/05/2014 at 17:49 point
Highly inefficient, but for simple control (until you can design something better) you can place a flat baffle under each prop that slides on the frame from the center outward. It could not only reduce the effective lift of a prop, but also shift the CG toward that prop, inducing roll in that direction. You probably don't even have to cover more than 1/4 of a prop to effectively reduce lift. Also, your actuator only has to overcome sliding friction since the aerodynamic force is perpendicular to the actuation direction.

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Peter McCloud wrote 09/05/2014 at 23:08 point
It's a good idea. My only concern is reducing the prop thrust. I don't have a lot of excess thrust currently so I might not be able to implement it. My hope with the vanes is that since airfoils provide more lift to drag, they'll able to produce a large amount of side force with a minimum of thrust reduction.

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zakqwy wrote 09/06/2014 at 14:25 point
I say baby steps first; get your thrust:weight ratio over 1 and sustain a constrained hover. I posted a link to the Project Morpheus video archive which has a lot of good test setups. Definitely worth a look!

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John Burchim wrote 09/05/2014 at 00:22 point
Can't get this project out of my thinking. Now I believe the reason to be your rotors. Your rotors are not opposite of each other, that is going to throw your torque off.

Should it not be front left and right rear same rotation? Opposite corners rotate the same?
not parallel.


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Peter McCloud wrote 09/05/2014 at 23:02 point
Electric quadcopters have the same rotation on opposite corners to do yaw control. They speed up the propellers that spin one direction and slow down the propellers that spin the other direction. This allows a torque difference that spins the vehicle, but the total thrust is balanced across the corners. Having them parallel still cancels out the torque, but if you tried to do yaw control, one side would drop.
Goliath has the props spinning parallel to allow the the belts to wrap around the drive pulley more and increase the torque transfered to the belt. Since I won't be using differential thrust, I can get away with doing parallel.

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John Burchim wrote 09/04/2014 at 23:24 point

Had a thought, for the purpose of testing only, your details show the support under the main body of the unit. If you shift your support to under the propellers, you would have a better view of the stress caused when it is try to lift using them.

If your struts do not support the motor how can it lift it under load?


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Peter McCloud wrote 09/05/2014 at 23:04 point
Goliath is capable of supporting itself at the propellers. The saw horse are under the center to take up less room in the garage and allow the shop crane in and out.

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John Burchim wrote 09/04/2014 at 16:53 point
using the Metal framing for your structure, do you have the ability to put an extra bend into one face of it for a second angle. It should make the overall structure much more rigid, without adding weight?


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Peter McCloud wrote 09/05/2014 at 22:53 point
I have a sheet metal brake, that's in pieces. I could use it to add the bends. The current frame is intended for prototyping.

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mr.nathan.richter wrote 09/04/2014 at 01:26 point
wow, this is incredible. why did you choose to go with a belt drive over shaft drive?

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Peter McCloud wrote 09/04/2014 at 11:01 point
Thanks! After researching belt, chains and drive shafts, I chose a belt system because it was light, could handle the RPM/torque I was targeting and able to handle shock loads well. If I use drive shafts I'd have to have a gear box at each propeller to change direction as well as a a larger gearbox at the engine to attach multiple shafts.

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John Burchim wrote 09/04/2014 at 00:58 point
I like the idea, but not the approach. You should consider slightly different approach. At least research drive system stress details, Torque details, and give some planning for rotation speeds required to gain lift.
How do you plan to change altitude?
Could you use some sort of flywheel to aid in rotation control?
Consider using a less direct drive to change the stress points to a better location, while increasing rotation speeds.
There are multiple thoughts that could be helpful depending on some of the requirements you are looking for.
Bicycle or motor cycle drive systems or indirect drive systems would be a good place to start.


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Peter McCloud wrote 09/04/2014 at 11:05 point
Thanks for the feedback John. I did start this project looking at motor cycle, bike and aircraft drive systems. I have sized the components to the loads, as well as done the calculations for lift, I just have documented the details. I'll have to get those added at some point.

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