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Goliath - A Gas Powered Quadcopter

A BIG Gas Powered Quadcopter

This project was created on 05/25/2014 and last updated 2 days ago.

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

Overview

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.

Engine

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 fiberglass cords and are able to transfer more power per weight than roller chain and can also run at higher RPMs.  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.

Propellers

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.

Control

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.

Frame

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.

Exhaust

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...

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Components
  • 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
  • Testing Belt Configurations (Tests #11 - #14)

    2 days ago • 0 comments

    Last week I was able to test out some new belt configurations. After checking out the test stand in tests #9 and #10, it was clear the test stand was working well, but the belts were still having issues. It's apparent that the flight rotors require a lot more torque than the test rotors and there is more slack in the belts due to this.

    The first attempt (Test #11) was adding a pulley on the slack side of the double sided belt. It seemed to help a little bit, so the next attempt was to try tightening the belts a little bit. This did not improve the situation. The literature suggests that having the belts too tight is as bad as having them too loose. This is because if the belts are too tight, the pitch on the belt gets stretched and they no longer mesh well with the pulleys. I don't know if that's what happened during the test, but after the test was over, the two sets of propellers were no longer aligned with each other.

    Another potential issue was how well the props were balanced. I hadn't balanced them thinking that they were probably close enough and the weight of the propellers was less than the pulleys. After Test #12 I took the time to balance the propellers. Only two of the propellers needed any weights and those two didn't need very much. I'll do another write up on balancing the props later. However after balancing them and running it, there was no perceptible change. The last change made was removing the springs on the double sided belt tensioner. I was curious as to if the springs were contributing to the oscillations. Again, no visible changes in the oscillations.

    So overall thoughts on testing so far.

    • The frame does not flex significantly like it used to. Some of this has to do with the way it was tied down before, but some of it also has to do with the changes to the frame that have been made.
    • The flat idlers are working. This are significantly lighter than the steel HTD pulleys.
    • While the belts are moving around significantly horizontally, they are staying in place vertically. Those parts of the issues seem to be solved
    • The relay board is working well. I was concerned with using mechanical relays with this amount of vibration, but so far they've worked.
    So far the overall design philosophy has been to use the minimum number of pulleys. This was to come up with a minimum weight design. It's clear that the minimum number of pulleys are not sufficient. Luckily the design so far is underweight, so some additional weight can be absorbed. The next steps are to add more pulleys to help dampen the oscillations and likely move the tensioners to the slack sides of the belts, again to help dampen the oscillations.

  • Tests #9 and #10, Checking out the Test Stand

    11 days ago • 2 comments

    Well the rain held off on Saturday long enough to do some short tests in the new test stand. Most of the morning was setting up all of the tie-downs. There are 8 lines supporting Goliath's weight. Two on each of the prop supports for redundancy. Eight lines are connected horizontally, two on each prop arm. Again there is some redundancy built in, so if a line fails or comes loose, the vehicle will still be secure. Underneath Goliath are four lines, each with about 3" of slack. These will come into play when doing to the hover test. Once Goliath has enough thrust it will lift upwards 3" until the lines are taut.

    In addition to the test stand, there is a protective barrier setup (a sheet of plywood with a hole cut into for a camera to take video (nicknamed the bunker).

    Two tests were run yesterday. The first, Test #9, was run for a short bit to check out how everything worked. We only took video from behind the bunker for this test. The belts seemed to have more oscillations in them than previous tests. This was not obvious from the video, but could see it from my vantage point. So I tightened up the tensioners and added a forward camera view and ran Test #10. Again the cameras didn't catch the oscillations, I need to get a better vantage point.

    It could be that the wood dummy props were balanced better. I'm going to remove the props and balance them while they are attached to the pulleys to see if that makes a difference. The new flat belt idler seemed to hold up, so I'll probably switch out the other pulley were I can put a flat belt idler and move that HTD pulley to act as an idler on the double sided belt to try to dampen out the oscillations.

    Overall the tests show that the test stand works well. Even though there is some give in the lines, the vehicle isn't bouncing all over the place. This setup should also work well for evaluating the controls once those are added on.

  • Test Stand (The Octagon!)

    16 days ago • 0 comments

    After going back and forth on how to rig up the hover test, I decided to go with a large test stand that will enclose Goliath. I've nicknamed it The Octagon cause it has eight sides and saying The Octagon reminds me of Rex Kwon Do from Napoleon Dynamite.

    Anyways, I started building the stand Sunday night out of 2x10s in the driveway. It's split into two halves to wrap around Goliath. Below is the top of the first half.

    After this it was tipped on it's side and the legs were added.

    Here are both halves of the initial frame.

    I had today off for Veteran's Day and got started on actually setting up Goliath in the stand. I moved the frame to a spot in the backyard that's surrounded by a fence on two sides and a building on the third. This should help to contain any debris contained for the higher RPM testing.

    The next steps were leveling the stands and joining them together with some more 2x10s. Using some rope, eye-bolts and s-hooks, each arm was lifted up to take the weight off the cart.

    It's been raining a little bit and it'll be a couple days before I have some time to do more testing, so Goliath will have to stay in the stand and be covered up.

    Here's a shot underneath the tarps. I've also wrapped the engine and electronics in plastic to make sure any leaks.

    The next step will be lowering it a foot so that it has 2 feet of clearance above and below. Then I'l add two tie-downs to each corner to prevent Goliath from twisting.

    When the hover test happens, the plan is to have four ropes tied to Goliath underneath and attached to cinder blocks. Each rope will have a couple inches of slack (all the same amount). As the engine speed increase, the weight on the test stand will decrease and when the thrust is finally greater than the weight, the slack in the lower lines will be eliminated and we'll know if we've had a successful test.

    Like I mentioned, the weather's kinda crummy right now, so no date set yet for the next tests, but stay tuned!

View all 32 project logs

Build instructions
  • 1

    THINK BEFORE YOU START

    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

    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

    BUILDING THE FRAME

    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

Discussions

Rebelj12a wrote 17 days ago null 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 16 days ago null point

Thanks for the inputs. This is what I feel Hackaday.io 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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PointyOintment wrote 16 days ago null point

66
I dont know if this will work, however it might...
99

Like this?
http://www.geek.com/science/weve-been-designing-quadcopters-incorrectly-since-day-one-1577256/

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Rebelj12a wrote 15 days ago null point

Possibly add an adjustable belt tensioner? Similar to this.

http://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=belt+tensioner

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.

http://www.dji.com/product/spreading-wings-s1000-plus/feature

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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Rebelj12a wrote 15 days ago null 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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Peter McCloud wrote 15 days ago null point

I have added spring loaded adjustable tensioners, that I built from scratch. They can be seen in the video link here.
https://www.youtube.com/watch?v=OfnLvJodg84
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 15 days ago null 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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gnoejuan wrote a month ago null 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 2 months ago null 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 2 months ago null 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 a month ago null point

I am interested in designing/ building a recovery system for this monster! I have emailed you.

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Peter McCloud wrote a month ago null point

I look forward to hearing about your ideas. I'll contact you soon!

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Mike Berti wrote 2 months ago null point

This is by far one of the most compelling quadcopters I've seen to date.

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Peter McCloud wrote 2 months ago null point

Thanks Mike!

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CHOPPERGIRL wrote 2 months ago null 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...

CG

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zakqwy wrote 2 months ago null point

You should post your design to HaD.io! 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 2 months ago null point

I agree with Zakqwy, you should post your project to HaD.io. 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 (http://hackaday.io/project/996-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 2 months ago null point

66
Placing your heavy motor on the top makes it inherently unstable.
99

This is not true: https://en.wikipedia.org/wiki/Pendulum_rocket_fallacy

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J Groff wrote 3 months ago null 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 3 months ago null 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 (http://copter.ardupilot.com/wiki/singlecopter-and-coaxcopter/)
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 3 months ago null 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 3 months ago null 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 3 months ago null 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 3 months ago null 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 3 months ago null 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.

John

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Peter McCloud wrote 3 months ago null 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 3 months ago null point

Peter,

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?

John

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Peter McCloud wrote 3 months ago null 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 3 months ago null point

Peter,
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?

John

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Peter McCloud wrote 3 months ago null 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 3 months ago null 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 3 months ago null 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 3 months ago null point

Peter,
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.

John

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Peter McCloud wrote 3 months ago null 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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John Burchim wrote 3 months ago null point

Peter,
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.

John

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Peter McCloud wrote 3 months ago null 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.

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Hacker404 wrote 3 months ago null point

Hi Peter,
What are the props made of? I look at this and see a 810cc motor that must be 30+ Kg and then I look at the pitch and surface area of the props and wonder how they don't tear apart from centripetal force at the prop RPM you will need to lift 30+ Kg.

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Peter McCloud wrote 3 months ago null point

The props are made from a foam core with wood stiffeners and then covered with 3 layers of 9 oz fiberglass. I have a few project logs detailing the progress, the last is: http://hackaday.io/project/1230/log/6507-not-so-rapid-prototyping

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bruceb75 wrote 3 months ago null point

You might want to take a look at how other belt powered propeller jigs have worked.... https://www.youtube.com/watch?v=rG9clKE6268 shows a universal hovercraft UH-14P.... There is added weight, but these belts really whip around.... constraining them like shown is a good way to keep them out of the prop

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Adam Fabio wrote 3 months ago null point

Hey Peter, Sorry you're having trouble starting the engine. I'm no small engine expert, but I've fought with a few of them in my day.
You know the old saying - gas engines need air, fuel, and spark. You know you're getting fuel to the carb, but is it letting that fuel in to the intake. (closed needle valve?)

Spark - the easiest way to do this one is to place the spark plug wire somewhere near the engine, and look for a spark while cranking. (You want to disconnect your props for this)
You could also disconnect the entire spark plug, touch the threaded portion of the plug to the block, and check for spark. If you're not getting spark, check your ignition system - sometimes these engines have a low oil cutout, which could be causing you problems. (You did put oil in it, right?)

Finally air - check for a clogged air filter, (could be packed in a plastic bag from the factory).

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Peter McCloud wrote 3 months ago null point

Thanks Adam. I did put oil in it, but perhaps it needs more now that it's been circulated around a bit. The air cleaner wasn't wrapped, but I did remove it to get at the carburetor and left it off for the last few tests. I had been leaving testing the spark until last since the gas setup is sketchy, but if the oil doesn't work I'll try those spark tests.

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Jasmine wrote 3 months ago null point

Hello Peter, you need to add a few more bits of documentation on Hackaday Projects to give your project the best chance of going through to the next round of The Hackaday Prize.

By August 20th you must have the following:
- A video. It should be less than 2 minutes long describing your project. Put it on YouTube (or Youku), and add a link to it on your project page. This is done by editing your project (edit link is at the top of your project page) and adding it as an "External Link"
- At least 4 Project Logs (you have this covered)
- A system design document (I can't see one. You should highlight it in the Details)
- Links to code repositories, and remember to mention any licenses or permissions needed for your project. For example, if you are using software libraries you need to document that information.

You should also try to highlight how your project is 'Connected' and 'Open' in the details and video.

There are a couple of tutorial video's with more info here: http://hackaday.com/2014/07/26/4-minutes-to-entry/

Good luck!

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Zorro wrote 4 months ago null point

Wow... This reminds me of Terminator 4...

Forgive me if I am stating something obvious or dumb, cuz I'm a complete newbie to this area , but have you considered making this as a tri-copter? You wouldn't need custom blades since all the blades are the same spin direction, the yaw control and flight stability is better, plus three blades instead of four would mean lighter design?

If nothing else, it'd be nice to understand the reasons why you chose a quad-copter over other designs.

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Peter McCloud wrote 4 months ago null point

I wanted to do a quad-copter because by having two clockwise and two counter clockwise propellers, the torque from the propellers will cancel out. To be honest I hadn't considered a tri-copter. Tri-copters tilt the rear rotor to offset the torque like a helicopter tail-rotor. The belt system doesn't allow the blades to tilt. I guess Goliath could be built as a Tri, but the the control surfaces would have to be bigger to compensate for the torque.

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Steve Shaffer wrote 4 months ago null point

I just discovered this electric clutch and figured it might interest you, at least you must agree it is interesting: http://www.ebay.com/itm/Electric-PTO-Clutch-for-Scag-61-72-Hydraulic-Drive-3-Wheel-Riding-Lawn-Mowers-/121060668200?pt=LH_DefaultDomain_0&hash=item1c2fc73328

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Peter McCloud wrote 4 months ago null point

This is interesting. WillyMacD had suggested electric clutches, but I didn't find these when I was looking around. I'll have to look into these.

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Steve Shaffer wrote 4 months ago null point

Invent a pulley that can expand and contract by turning something. This will give you prop speed control, and thus allow simple control by all the normal RC control baords.

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Peter McCloud wrote 4 months ago null point

That would certainly make things easier. CVTs use a conical pulley to adjust the radius to do what you're talking about, but I don't think it'll work with a toothed belt. An expanding and contracting pulley would have to allow the teeth to slip in some manner. Perhaps a Derailleur setup might work, but I don't think it'd be responsive enough.

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Steve Shaffer wrote 4 months ago null point

I agree it's hard. The more I read the others comments the more it really sounds like you should spring for 1/5th scale helicopter assemblies and blades, then simple servos can adjust pitch and therefore thrust just like an electric quadcopter. I just created a guided rocket powered by the 4hp edf from Dr. Mad Thrust, with vectored thrust by flaps, flaps suck, couldn't get stabilization good enough with the multiwii controller. Just a heads up. I've given up with flaps for good thrust vectoring and am changing the design of the craft and giving it swivel nozzle styled vectored thrust.

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zakqwy wrote 4 months ago null point

Steve, I'd like to see your project if you do a gimbaled thruster. In my experience, it's not easy.

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Stephane wrote 5 months ago null point

For the propellors; when I built my composite uav wings I used the scraps from the hotwire cutting as a support for vacuum bagging. Since you mill your cores you may want to mill shells that fit around the props when bagging? Also some UD carbon on both sides of the prop will increase the bending strength :)

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Peter McCloud wrote 5 months ago null point

Thanks! Milling support shells sounds like a good idea. I do plan on eventually switching to carbon to increase the strength, but I'd rather get all the kinks worked out with cheaper fiberglass.

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PK wrote 5 months ago null point

Awesome project! Would love to see it fly.

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Peter McCloud wrote 5 months ago null point

Thanks! I'm looking forward to seeing it fly too!

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pfeffer.marius wrote 5 months ago null point

Whats your current plan for thrust control ? You could use some kind of wing, controlled with a (big) servo which can increase its produced air resistance under a rotor. (like flaps on a airplane)

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Peter McCloud wrote 5 months ago null point

Thanks for the inputs! The current plan is to use vanes similar to how hovercraft steer. That'd be a good way to control pitch and roll, but I'm not sure how well that'd work for yaw.

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WillyMacD wrote 5 months ago null point

Peter, I'm planning a similar albeit, smaller project. For thrust control, I was bouncing the idea of using electrically controlled clutches on the shafts of the props. Perhaps this is something that may work for you as well as with minimal changes to current control software. cheers and good luck

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Peter McCloud wrote 5 months ago null point

Thanks for the input! I'd really be interested in hearing more about your project if you feel like sharing. I don't know much about electrically controlled clutches but I'm definitely intrigued. The control system isn't set yet so it's a possibility. Do the clutches act simply in an On/Off manner or can you vary much much they engage?

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screen Name wrote 5 months ago null point

Ever thought about using the fuel engine as an electic generator? I understand that's not really helpfull at this point, but in my opinion thats a better way to go. Im curious about the flight dynamics of a mechanical sytem like yours. Maybe you add some serious nonlinearities to the system regarding control theory. ... Or maybe it'll just fly as heck. Have fun.

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Peter McCloud wrote 5 months ago null point

I had thought about coupling the gas engine with an electric generator and then using electric motors (hybrid system), but it's just too heavy at this scale. For aircraft the engines run near the optimum RPM most of the time, so the advantage of a hybrid system isn't as great.
I'm really curious as to how the controls are going to behave as well! I'm not expecting Goliath to be very nimble, but we'll see. Thanks for the feedback!

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samern wrote 5 months ago null point

You might consider emulating what you see in an ordinary A/C outlet in a car....3 or 4 vanes controlled by a single horn sitting outside the duct. Air can flow down the duct and then down and the vanes can direct the air straight down, or horizontally perpendicular to the quad's arm/duct. That gives you pitch/roll and yaw. the degree the vanes move controls the vectored force at the edge of the arm and so altitude and direction. You can also control airflow through the duct with a butterfly valve inside the duct also controlled by a horn (someone mentioned that as well, I think). What I think is going to be super interesting is the flight control software...

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samern wrote 5 months ago null point

Did someone already suggest this....I know you are using fixed pitch props, but there have been developments with constant speed props that don't use a governor and use small electric motors to vary pitch. Might make this too complicated and heavy. If you consider ducts you are going to need quite the concentrated blast out of each tip. The Harrier uses a rotating valves with vanes to vary the thrust direction, you might get some value out of just nozzles that open and close out the end....at any rate this is so very interesting I'm looking forward to seeing it fly.

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Peter McCloud wrote 5 months ago null point

Thanks for the feedback! I've been really hesitant to look into variable pitch props. Maybe I'm just biased towards the fixed pitch for simplicity, but one big concern is the loading. Each blade will be supporting 30 lbs in hover, which will provide a large moment at the blade root and make any variable pitch hardware heavy.
I really wanted to have the ducts be part of control system and opening and closing the nozzle at the end of the ducts would be a great way to do that. I'm just not sure how to implement it. I had thought about using nitinal wire to expand and contract the nozzle, but I'm not sure how responsive it would be.

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Adam Fabio wrote 6 months ago null point

Wow! that's one big quadcopter - thanks for submitting Goliath to The Hackaday Prize! I'm just curious how you'll get the props spinning in opposite directions to avoid torque issues?
Keep up the good work, and don't forget to document your flight control system - I'm curious to see what sort of system you go with - vanes and servos or something completely different!

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Peter McCloud wrote 6 months ago null point

Thanks! I'm planning on posting about the drive system later today and that'll show how the props spin in opposite directions.
I think that vanes and servos might be the best choice. All the other methods I've considered wouldn't handle yawing the vehicle well since all of the propellers rotate at the same speed.

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RoGeorge wrote 6 months ago null point

Did you considered Continuous Variable Transmission http://en.wikipedia.org/wiki/Continuously_variable_transmission instead of a gearbox?

It might help with the thrust distribution too.

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Peter McCloud wrote 6 months ago null point

I had not considered a CVT. Goliath doesn't have a gearbox, but it does use belts. Maybe a CVT could be used to vary the propeller speeds. Thanks for the suggestion!

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jeff.ballard.86 wrote 6 months ago null point

This sounds so dangerous/awesome, those two words do go hand in hand you know. :D

Im gonna pay attention to this, I may have to recreate your results when you finish.

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Peter McCloud wrote 6 months ago null point

Thanks, I'm glad to hear someone else is thinking about building their own!

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dave.m.mcdonough wrote 6 months ago null point

How to you plan on adjusting the thrust vector? Considering the belt drive I would think adjustable pitch props would be WAY easier mechanically, and provide more controllable result.
Also check out fiberglass poles for windsocks and such, using ones as a driveshaft inside a larger one as the support might be a lot lighter than a frame rigid enough to handle all that belt tension and let you space the props out further.
Or possibly even just using the engine as a generator and plopping electrics on the corners. ;)
Looks like you're already well underway but I hope the ideas help.

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Peter McCloud wrote 6 months ago null point

Thanks for the inputs! I had looked into driveshafts and while the fiberglass would be light, I'd need gearboxes at the center and at the propellers. I was really hoping to build a gas/electric hybrid since control would be simpler with electrics at the propellers, but I think the quadcopter would have to be even bigger before you can carry a generator and motors to go with it.
As for the thrust vectoring I haven't decided for sure yet, but I'm currently thinking servo actuated surfaces or something integrated with the ducting.

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zakqwy wrote 6 months ago null point

I've been doing a lot of design work trying to optimize thrust:weight ratio; while I plan to do some real-world tests to validate prop and motor selection, this site has given me a good quick starting point:

http://personal.osi.hu/fuzesisz/strc_eng/

It allows you to input prop size, pitch, type, air density, amd RPM and spits out a thrust calculation and motor power requirement. I haven't dug in to the tool's calculations, but it may be a good starting point for you. I'm guessing your belt-driven design will give you plenty of alignment flexibility but will also limit your maximum RPM, requiring a fairly good size set of props.

It's worth mentioning: 30 HP is A LOT of power. I suggest doing some research on typical maximun safe belt RPMs and using this as a primary design constraint to minimize safety concerns; in addition to whipping about and damaging stuff, a broken drive belt would likely result in a catastrophic and unrecoverable loss of flight control. Might be worth taking the weight penalty to equip the chassis with some kind of belt guard.

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dave.m.mcdonough wrote 6 months ago null point

So I'm looking at this project log of the motor with it's cover off and I got an interesting idea. This is a little off the wall and mostly half-baked brainstorm kinda thing but maybe you can think about it.
instead of a frame, belts, pulleys, etc.. mount the biggest blower fan 30HP can support directly to the motor. Then construct the frame as a big hollow X shape where the air gets ducted out the corners. maybe some in the center too but the corners will have your airflow vane directional vectoring control going on. Like a big hovercraft thing. :D
Just wrapped fiberglass or something would be pretty lightweight.

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zakqwy wrote 6 months ago null point

Cool idea, Dave. Isn't that how the Harrier and the VTOL version kf the F35 work? Definitely easier to actuate louvers then props; in addition to maintaining belt tension during vectoring you'll need to consider gyroscopic effects of the spinning props, which might drive up actuator torque requirements.

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dave.m.mcdonough wrote 6 months ago null point

Harrier turns the turbine exhaust straight downwards so yes kind of similar to that but we wouldn't be having a forward facing intake.. F35 I think has a separate turbine for VTOL? Not sure.
It occurred to me that in this x shape ductwork thing you could also have some throttle-body style valves to proportion the outputs.

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zakqwy wrote 6 months ago null point

Yup, butterfly valves of some kind would work. Turndown isn't great but they would only need enough rangability for angular velocity changes; overall ascent rate could be controlled using engine speed and maybe trimmed for response using the dampers. I'll bet you could actually salvage the throttle plate mechanisms out of a few old engines, the basic design requirements are likely similar.

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Peter McCloud wrote 6 months ago null point

Thanks for the link to the information, I'll have to check that against what I've calculated so far. Yes 30HP is ALOT, but the frame and ducting will encompass the belting. Once I go beyond tethered flying, I plan to incorporate a Ballistic Recovery System to help with any failures.
Also interesting idea with the blower and jetting the exhaust. I'm not sure if that method would work with this engine's weight and power though.

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zakqwy wrote 6 months ago null point

Are you using some kind of swashplate system? How are you varying prop pitch? This is quite awesome.

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Peter McCloud wrote 6 months ago null point

The plan is to use fixed pitch props and to vary the thrust direction for control. The controls haven't built yet, and there are a few methods I'm considering using. Thanks for the interest in the project!

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zakqwy wrote 6 months ago null point

Cool! We should compare notes, I'm putzing about with gimbaled fans albeit on a far smaller scale. Looking forward to seeing your design.

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