Astounding RC flying with counterrotating drive


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Hopefully the total body of knowledge I will need to grasp before I can fully participate in this will prove vast enough to keep me from emptying my wallet on a new hobby…


Okay, quadcopters and drones need to be updated with motors that quiet.

Jesus. It moves like it’s on rails.

At 2:57 you can clearly see the two counterrotating propellers–previously I wasn’t sure if it had two props, or one prop and a counterrotating weight inside. It does those ultra-low-speed rolls by varying the relative speeds of the props, so the unbalanced torque twists it around the rotor axis.

That’s really fascinating. Coaxial rotors have been used in helicopters (e.g. everyone’s favorite crazy ex-Soviet attack copter, the Black Shark), where among other things they remove the need for a tail rotor (a normal chopper that loses its tail rotor starts spinning like a maple seed, it’s not pretty). I’d never thought of using that setup for a prop plane.

This is just a guess, but I suspect that that is a very light, low-powered engine even by mini-drone standards. That plane doesn’t look much more substantial than something you’d fold out of notebook paper. They’re flying it indoors because even the gentlest of breezes would send it tumbling, and you can see that it doesn’t go much faster than a brisk walk. Even small quadcopters need a bit more oomph than that.


If you are like me and want to nerd out learning more about the plane and motor I found a thread on an RC forum where the designer/builder of the motor explains it. He 3d printed the key parts, combined them with off the shelf gears to make the counter-rotating “transmission”. Enjoy:
better look at the plane there too - not discussed, but interesting tri-wing configuration.


The correct term here is “contra-rotating” which is where you have two propellers on a common shaft rotating in opposite directions. “Counter-rotating” means two motors, usually one on either side of the aircraft, with props spinning in opposite directions.


How may different sports does this gym support?


Also: Finland. Winter. 8 o’clock at night.


By the way: both props spin at fixed ratio of almost the same speeds: 15:14

“… we have been very happy with the ratio we originally selected (15/14) …”

"Since the reversing is done using toothed belts and pulleys, it means the RPM ratio of the front and rear props is always totally fixed. "

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That’s pretty normal to see on the floor of a european gym. I think the image shows markings for badminton, basketball (it would be netball in the UK), handball, volleyball and five-a-side football. The small one in the bottom right could be a fencing piste.

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Well, yeah, but F3P is a class of RC planes designed for indoor flight. The competition season is in winter because you’ll want to be inside anyway, but most of these guys will be using heavier, faster planes when they go outside in summer.

Contra-rotating props on full size aircraft aren’t new, but they’ve never been common.

I was wondering the same thing, and the only answer I can come up with is “All of them.”


Seeing as how these things move themselves by pressing on the air around them its awfully have for them to work without creating pressure waves in the air.

Those are the court markings for Calvinball.


Thanks, I immediately wondered if there would be an thread for it :smile:

This reminds me of outdoor slope soaring superlights, like “le fish” and it’s brethren:

I really need to build me one of these…


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