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Permalink Reply by Martin Seven on April 3, 2010 at 6:30am

The main issue would be with the weight, but not because of lift - it's the inertia that gets ya :-) gas/glow engines have much higher response time, they need more of it to rev up. That means you'd probably never get a fixed pitch unit in the air. You'd need variable pitch. And a pretty good RPM governor to keep it all in sync.

A hybrid solution might also be of interest to you :)

I've only heard stories about a gas powered tri. Someone's grandpa somewhere in the Czech Republic, in the old commie days, build a gas powered tri with mechanical gyros, got arrested by the secret police, came out clean, and as he was flying it over a field it got shot down by a hunter who thought it was a duck. The original storyteller promised to provide pictures but hasn't been heard from since, so it could very well be just an urban legend.

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Permalink Reply by Jason Frisbie on April 3, 2010 at 6:35am

Good point with the RPM gov and the vari pitch. I was kinda thinking the same thing. I have seen a few Electrics that are done with Vari pitch heads too. They work nice. That might be a good way to start out and see if it works.

Thanks

Jason in Hawaii

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3D RoboticsPermalink Reply by Chris Anderson on April 3, 2010 at 7:51am

The ESCs on the quads are changing speed at at least 200Hz. Servos can only move at 50Hz, so even if you had instantaneous fine-grained response by the engine, the mechanical servos just can't move fast enough to compete with electric. Of course a gas-powered quad would be bigger and move more slowly, so maybe you could get by with slower response, but it all sounds complicated, risky and very, very dangerous!

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Permalink Reply by Jason Frisbie on April 3, 2010 at 9:24pm

That totally makes sense. I didnt know the numbers but I had thought about the response time. If my thought process is right (and it may not be) you could slow down the(undesired) movements by extending the arms a bit and speed up the response by using Heli digital tail rotor servos which are much faster than other servos. I have found servos with higher than 250Hz pulse rates. Again, I really dont know if this will work but I want to try.

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Permalink Reply by wurpfel on April 3, 2010 at 8:00am

gas is cool, but electric much easier.

on gas you have to deal with "good vibrations", they could fall in resonance and destroy the tri in seconds.


this has only two rotors, with three its much higher risk to fall in!

look on youtube for resonance and chopper, all this kinda vids turn to a sad end ;-)

this is famous:
http://www.youtube.com/watch?v=mbn3WancX6g

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Permalink Reply by A. Rafael Ptacnik on June 28, 2011 at 4:29pm

This sounds like a Good Project, Jason did You got any further than just asking for info ?

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