Now we're cooking with gas!
I have just completed a project to build a helicopter with a gasoline engine, controlled by Arducopter (of course!) This helicopter serves as a test bed for future gas heli development work for a client of mine. The goal was to prove out that it could be done. Gas engines pose a unique challenge for Arducopter due to the heavy vibration they produce. But they also present a lot of promise for UAV applications as it can allow heavy payloads, long duration flight, and high speeds.
The heli is based on a Helix Heli conversion of a Trex 700. However I stretched it to 800, used many aftermarket upgrades such as from KDE, and machined a number of custom parts myself. The machine required quite a bit of customization in order to increase frame stiffness which is important for vibration reduction. The engine is a Zenoah G29RC engine with pull start. This is an increased displacement 23cc engine, which makes more power but creates more vibration than the G23. I could have purchased an aftermarket balanced engine, but I wanted to use COTS parts and also prove the Pixhawk can survive with a worst-case engine.
Last night I performed the first check flights of the new machine and began PID tuning. This is one segment of that flight where I was working on the PIDs.
Today I finished the PID tuning, and it is flying very well indeed. After increasing rotor speed to ~1600rpm and tracking in the blades, the vibrations on the Pixhawk are quite good, better than both of my quads:
I flew it around a bit in Stabilize, and hit 30 m/s without really trying. It should easily be capable of 40 m/s flight speeds. I'm hoping for a 10 kg payload capacity. Flight time is currently better than 20 minutes with plenty of reserve on a 630cc tank. I will probably begin development on a larger fuel tank system on the order of about 2L which should allow for 1 hour of flight time with payload. Currently the 2S 4400mAH avionics battery lasts for at least an hour, but will be supplemented with an on-board generator.
Later today, I will start working on auto missions and will shoot another video.
The success of this project opens up an entirely new world of possibilities for affordable UAVs. It will be possible to perform realistic crop spraying. Aerial imaging with the best quality cameras available. And extended flight ranges in a large aircraft with VTOL capability for usage in areas without a prepared landing strip. Obviously this is not the type machine that would be used anywhere near people. But remote areas, or secured industrial lands would be suitable operational areas.
Comments
Wow, nice work Rob!
Awesome always impressive work by rob bringing traditional heli into the future
I wonder if this heli (i.e. modified Trex 700) can carry 5 kg or 10 kg load).
Rob, nice job. Hopefully, we can see some documentation of this mod.
Thanks, Noli
Rob, Good job
Regards,
David R.Boulanger
Hi Rob, Mitchell, interesting discussion,
It will actually be an important issue for the future regarding use over populated areas but I tend to think that while safety rules may be considerable, it will eventually be permitted.
Clearly operator licensing, manufacturer type approval and sufficient safety measures will be required, but the value is too great to not allow helis.
A parachute and requiring sufficient altitude to deploy it could greatly reduce the risk and requiring low level and landing and takeoff only be permitted under approved conditions could eliminate a lot of the problem.
And redesigning the hobby grade copter components so they were actually highly reliable would make a huge difference as well.
I don't think a guard is at all practical on a heli, but I do think they can be made sufficiently reliable to be at least as safe in the sky as their full sized counterparts.
The efficiency of that giant rotor disk is what makes them important.
Best Regards,
Gary
I think that it would be more reasonable to make a gas powered, ducted fan twin-copter, if you were looking to operate near people. You'd still get many advantages, but the safety situation would be much better.
Mitchell, I suppose it is possible to make prop guards for it, and let's say you managed to remove the danger from the blades themselves. But, you're still talking about a 12 lb, fairly hard, flying machine, capable of travelling at 100 mph, or falling from 100+ feet up. It would be similar to a comparably sized airplane. You can minimize the risks, but never totally eliminate it. So, then it becomes a discussion about what is acceptable risks.
Beautiful machine Rob, congratulations. I have one question:
You seem to say it could never be used in populated circumstances. Why exactly can't prop guards be installed on a heli? Is the blade speed so high it causes problems? Sorry if I'm missing something fundamental here, but I don't see why it can't be applied to an 800 size heli. You'd be looking at a few kg of guard.
I understand on electrics that weight is at a premium and another kg or two of frame will make the model impractical, but with petrol, inefficiencies like this are easily absorbed. A main prop / tail rotor guard will both take up weight, waste some energy and chew up some efficiency but in the scheme of things its a safety tax to operate in populated areas. With the cost of fuel it really doesn't add up to much. Cheers.
I've always wanted to do a gas heli with arducopter. You solve so many problems at once, flight time, payload, etc. Amazing work well done!
@Rob Dunbar, I've been flying for 3 years, and never had a problem with the GPS under the carbon fiber blades. Some people insist it has to be a problem, but it's just not. The disk solidity is just too low.
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