Does this project spark your interest?

Become a member to follow this project and don't miss any updates

Goliath - A Gas Powered Quadcopter

A BIG Gas Powered Quadcopter

Similar projects worth following
This project is submitted for

This project was created on 05/25/2014 and last updated 2 months 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
  • Manufacturing Issues

    2 months ago • 1 comment

    The design of the new rotors for Goliath is complete. There's also been a lot of effort spent making a separate repository for the rotors. The goal is to provide everything a person would need to manufacture their own rotors from scratch using the process used for Goliath. Manufacturing of the rotors has started, but there has been some issues machining the new rotor cores.

    To avoid any confusion, the numbering system for the cores started with original cores built for Goliath (Cores 1 through 4). Two were destroyed in the second test and were replaced with rotors 5 and 6.

    For the 7th core, in addition to use the new tool paths, there was an attempt to optimize the cutting path and reduce the cut time. The optimization worked for one side, but ruined the leading edge on the other. It was decided at that point to hold off the optimization until after enough cores were completed.

    The 8th core came out acceptable with no issues. The 9th core had a bad trailing edge. It appears that the bottom cuts were performed with the z-axis slightly too low and too much material was cut off the rotor and the trailing edge broke. To help ensure the Z-axis was aligned properly for the following propellers the spoil board was re-machined to ensure it was level.

    The next core, the 10th was completed without issue and was likely the cleanest of the cores that have been made. The 11th core, was the first of the new clockwise cores since cores 8 and 10 were counter-clockwise rotors. The tool path was loaded and the router was left to rough out the top of the rotor. This was the result after returning the the router:

    No idea what happened.

    Making additional rotors is on hold all the birch plywood is used up. Meanwhile the new tool paths will be tested out on a purely foam blanks to avoid wasting more birch. Work can also start on fiberglassing cores 8 and 10. There's still a lot of work left to do, so it'll be several weeks until all of the new rotors are completed.

  • 35 lbs short

    3 months ago • 3 comments

    Thrust measurement and weight reduction has been the focus of the work on Goliath over the last few weeks. Prior to the last test, Goliath weighed 238 lbs, about 40 lbs more than the target weight when the project started. With the vehicle design still in flux it's not time to move away from the slotted angle yet, but there were a few areas that could provide some potential weight reduction.

    Bolts and Washers

    When Goliath being assembled for the first time, the final design was somewhat nebulous. To make things easier, the same sized bolts where used for the frame assembly. Most of the bolts don't need to be the full length, so wherever possible, the original 3/4" long bolts have been replaced with 1/2" long bolts. The size difference is shown below. About 75 of these bolts have been changed out for smaller bolts

    While the bolts were being swapped out, the traditional lock washers where replace with external toothed lock washers. The primary reason for replacing the washers is that the traditional lock washers aren't very vibration resistant and every test would see at least one or two come loose. A bonus to replacing the washers is that the external tooth washers are lighter than the traditional lock washers. The picture above also shows the external toothed and traditional lock washers.

    Cross Beams and Side Beams

    The side and cross beams previously used the wide slotted angle. It was felt that they could be swapped out for the narrow slotted angle with a minimal reduction in stiffness. Below on the right is the wide cross beam and on the left is the narrow cross beam replacement installed.

    Cross Members

    The cross members were another area improved. Previously the two cross members on each side of Goliath spanned the whole length of the side and angle wasn't ideal for stiffness. Each of the cross members where removed and trimmed into two smaller pieces, with a little bit of excess. These pieces where then used to form two smaller crosses on each side. Below is a shot of the side beams and cross members being reconfigured on one side of the vehicle.

    After completing the structure modifications, the end result is that Goliath looks a bit leaner, and the weight was reduced by 5 lbs to a total weight of 233 lbs. The slotted angle structure is probably as lean as it's going to get.

    Propeller Axles

    Another issue that needed to be addressed was the axles for the two propellers powered by the double sided belt. After inspecting the vehicle it was found that the axles were slightly deformed (see picture below). The double sided belt needs additional tension, probably because of the extra length and the difference in the angles. Eventually the all-thread axles will be replaced with thicker axles, but for now an easy fix was to replace the 5/8" zinc plated all thread rod with 5/8" stainless all thread rod. The stainless has a higher strength and has more resistance to being deformed.

    Thrust Measurement

    The thrust measurement portion of the # Drone Test Stand has been completed. You can read the details there, but the test stand has been setup to measure the thrust while Goliath is running. Below is a picture of the remote display with Goliath in the background.

    In the above picture the reading says 220.92 lbs. This was because some of the hardware had been removed from Goliath. Note that there is no data logging capabilities built it. The measurements are being recorded visually for now.


    Three more tests have been conducted since the last posted test. There hasn't been time to compile the video yet, it'll probably get posted over the weekend.

    Test 22 tested the latest changes in the frame. The test went smoothly and Goliath was brought up to full speed without the ignition switch coming loose. There was no flexing in the frame visually, so the new design appears to be working.

    Test 23 attempted to get full thrust measurement data. However the double sided belt tensioner was not performing satisfactorily...

    Read more »

  • The Likely Suspect...

    3 months ago • 6 comments

    The last few tests have shown that under full power Goliath was unable to produce enough thrust to lift itself. Analysis shows that Goliath should have sufficient power to lift itself, but it's difficult to say why Goliath is not hovering without additional data on the actual thrust and engine power being produced. The electronics for measuring the thrust produced is almost complete. Measuring the engine power requires measuring the engine RPM and a hall effect sensor is being installed that will be triggered by the magnet on the flywheel.

    Meanwhile the design analysis has been revisited again to make sure there wasn't something's that been missed. The power required calculations were shown to be sound, so a closer look was at the propeller design was next.

    Originally when designing the shape of the propellers, analysis was performed using simplified blade element theory. This consisted of some code borrowed from a Matlab code that I got from a University of Cambridge website. An attempt to make a spreadsheet out of this was unsatisfactory and Prop Designer was tried instead. Aircraft propellers and helicopter rotors work on the same principle, but operate in different regimes. Since the hover condition (static thrust) was the design condition for Goliath, Prop Designer gave an answer, but the software warned it may not be a good answer. With the deadline for the 2014 Hackaday Prize looming, it was decided to push forward and design the propeller with an angle of attack at the maximum L/D of the airfoil to get an efficient design.

    Taking a closer look at the propeller design required having a more accurate analysis. This time a python code was written to analyze the design and the issues encountered previously were resolved. While the new python code is giving the best results for the propeller design so far, it still needs to be validated with data. However if it is right, then the new analysis shows a reason why Goliath isn't flying and more importantly how I can change the design to get Goliath flying.

    Below is a plot showing the predicted power curves for different propeller designs using the new code.

    The current design has a angle varying from 20 degrees at the root to 12 degrees at the tip. The problem with the design could be that it produces too much thrust at lower RPMs. The predicted power is too much for the engine to get above 2400 RPM, limiting the power to 21 Hp. The predicted thrust is at this condition is 220 lbs. Goliath weighed 238 lbs when last tested, so this could be why Goliath isn't flying.

    If this is indeed the case, then the fix is to lower the tip angle. The plot above shows 3 additional designs where the tip angle is decreased in increments of 2 degrees. The last design in the list has a tip angle of six degrees and looks to be the most promising. This design could allow the engine to run up to 3300 RPM generating 27 Hp and the predicted total thrust is 290 lbs which should provide more than sufficient thrust.

    The next test will provide thrust data and possibly engine RPM data. This will help validate the software and provide a good path forward to get Goliath flying.

View all 46 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


thesunman84 wrote a month ago 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 :)

Are you sure? yes | no

Peter McCloud wrote 24 days ago point

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

Are you sure? yes | no

Aaron Cooper wrote a month ago 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 a month ago 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 a month ago 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 3 months ago 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 3 months ago 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!

Are you sure? yes | no

surubarescu wrote 4 months ago 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?

Are you sure? yes | no

Peter McCloud wrote 4 months ago 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.

Are you sure? yes | no

surubarescu wrote 4 months ago 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.

Are you sure? yes | no

Rollyn01 wrote 4 months ago point

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

Are you sure? yes | no

Peter McCloud wrote 4 months ago 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. 

Are you sure? yes | no

Adam Fabio wrote 9 months ago 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!

Are you sure? yes | no

Peter McCloud wrote 9 months ago 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.

Are you sure? yes | no

dwardio wrote 10 months ago 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.

Are you sure? yes | no

Peter McCloud wrote 10 months ago 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.

Are you sure? yes | no

Rebelj12a wrote 11 months ago 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.

Are you sure? yes | no

Peter McCloud wrote 11 months ago 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!

Are you sure? yes | no

Rebelj12a wrote 11 months ago 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

Are you sure? yes | no

Peter McCloud wrote 11 months ago 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.

Are you sure? yes | no

Rebelj12a wrote 11 months ago 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.

Are you sure? yes | no

Rebelj12a wrote 11 months ago point
Also, of note on the page I linked is the motors they use and the kg of force they exert for flight.

Are you sure? yes | no

PointyOintment wrote 11 months ago point
I dont know if this will work, however it might...

Like this?

Are you sure? yes | no

gnoejuan wrote a year ago point
What i see here is a flying lawnmower. And that's exactly how I'd use it.

Are you sure? yes | no

Dave Hermeyer wrote a year ago 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?

Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

michaeldlewandowski wrote a year ago point
I am interested in designing/ building a recovery system for this monster! I have emailed you.

Are you sure? yes | no

Peter McCloud wrote a year ago point
I look forward to hearing about your ideas. I'll contact you soon!

Are you sure? yes | no

Mike Berti wrote a year ago point
This is by far one of the most compelling quadcopters I've seen to date.

Are you sure? yes | no

Peter McCloud wrote a year ago point
Thanks Mike!

Are you sure? yes | no

CHOPPERGIRL wrote a year ago 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...


Are you sure? yes | no

zakqwy wrote a year ago 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.

Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

PointyOintment wrote a year ago point
Placing your heavy motor on the top makes it inherently unstable.

This is not true:

Are you sure? yes | no

J Groff wrote a year ago 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.

Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

J Groff wrote a year ago 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.

Are you sure? yes | no

Smerfj wrote a year ago 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.

Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

zakqwy wrote a year ago 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!

Are you sure? yes | no

John Burchim wrote a year ago 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.


Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

John Burchim wrote a year ago 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?


Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

John Burchim wrote a year ago 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?


Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

mr.nathan.richter wrote a year ago point
wow, this is incredible. why did you choose to go with a belt drive over shaft drive?

Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

John Burchim wrote a year ago 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.


Are you sure? yes | no

Peter McCloud wrote a year ago 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.

Are you sure? yes | no

John Burchim wrote a year ago point
I noticed your framing flexed and that is with no load, you might need to add either tubing or reverse angle framing to reinforce your struts. have you considered using chains instead of belts as they tend to flex less. Also was wondering about your shaft sizes, your shafts should all be close to the same size for the torque they are receiving which should be similar.
I don't know if any of this is helpful but hope it works out for you either way.


Are you sure? yes | no

Peter McCloud wrote a year ago point
I do need to fix some of the flex. I'm still debating on the best method that won't add too much more weight. The shafts for all the props are 3/4" all thread.

Are you sure? yes | no

Similar projects