When it comes to hobby rotorcraft, it almost seems like the more rotors, the better. Quadcopters, hexacopters, and octocopters we’ve seen, and there’s probably a dodecacopter buzzing around out there somewhere. But what about going the other way? What about a rotorcraft with the minimum complement of rotors?
And thus we have this unique “flying stick” bicopter. [Paweł Spychalski]’s creation reminds us a little of a miniature version of the “Flying Bedstead” that NASA used to train the Apollo LM pilots to touch down on the Moon, and which [Neil Armstrong] famously ejected from after getting the craft into some of the attitudes this little machine found itself in. The bicopter is unique thanks to its fuselage of carbon fiber tube, about a meter in length, each end of which holds a rotor. The rotors rotate counter to each other for torque control, and each is mounted to a servo-controlled gimbal for thrust vectoring. The control electronics and battery are strategically mounted on the tube to place the center of gravity just about equidistant between the rotors.
But is it flyable? Yes, but just barely. The video below shows that it certainly gets off the ground, but does a lot of bouncing as it tries to find a stable attitude. [Paweł] seems to think that the gimballing servos aren’t fast enough to make the thrust-vectoring adjustments needed to keep a stick flying, and we’d have to agree.
This isn’t [Paweł]’s first foray into bicopters; he earned “Fail of the Week” honors back in 2018 for his coaxial dualcopter. The flying stick seems to do much better in general, and kudos to him for even managing to get it off the ground.
26 thoughts on “When Sticks Fly”
RCTestFlight did something similar. Love to see abnormal flying machines.
re: more rotors, as the rotors get larger, they have more rotational inertia (harder to accelerate/decelerate rapidly) and they also end up with more of a gyroscopic effect (harder to tilt quickly), before long you need to switch from simple fixed propellers to the complex hinge/swashplate setup that helicopters use. having lots of small rotors instead of a few large/complex ones is a tradeoff that seems practical (at least so far)
Coaxial rotor helicopters are a thing and they work both big and complex (e.g. the Russian Kamov) and small and simple (many RC toys).
But there is a reason why helis have both rotors together at the top and the body of the helicopter is hanging *below* the rotors. I.e. not what he has in the video with the “stick”, where one rotor is at the top and the other one at the bottom.
Low center of gravity is important and it helps a lot with the stability of the craft (think how a steadicam works).
1. Big coaxial helicopters have full cyclic control via swashplate and are completely *utterly* dissimilar to the thing above and that is exactly what @David Lang mentioned!
2. The reason why helicopters have rotor at the top have nothing to directly do with stability. That is a complete BS which laymen can’t get their heads around for almost a century. It even have a name: https://en.wikipedia.org/wiki/Rocket#Pendulum_rocket_fallacy . Yes it applies to helicopters. Mein Gott *facepalm*.
3. Camera stabilizers are usually a very active system and have nothing to do with gravity stabilization.
I suspect the body of the heli is below the rotor is so that people can board while the rotor is turning and retain a full complement of feet.
Except that pendulum rocket fallacy does not apparently apply to helicopters. But a helicopter with rotor at the bottom is actually more stable: https://aviation.stackexchange.com/questions/42513/would-a-helicopter-with-the-blades-on-the-bottom-fly-the-same-if-at-all
holding out for a monocopter
Not really possible because of the torque of the rotor spinning the body of the craft in the opposite direction. So you would need to actively counter this somehow, usually with a second rotor (either coaxial or on a tailboom pushing sideways – like helicopters).
Sure it is possible and it has been done. You just have to do a tip powered rotor. It has been done with ramjetsm rockets, and even smaller props and motors on the rotor tips. The only torque you have then is the friction of the bearing which seems to be manageable.
The downside is they tend to be really loud. So while possible not all that practical.
Vanes can counteract the rotor torque using the downwash, and in fact it has been done. I dont know if it’s ideal, but it’s hardly impossible.
Or deflecting vanes: https://hackaday.com/2018/08/31/single-rotor-drone-a-thrust-vectoring-monocopter/
Might be able to pull it off with shifting weights that extend from the center and pull in as necessary.
Weights won’t cancel a torque around the Z axis, but deflecting the airstream will: https://hackaday.com/2018/08/31/single-rotor-drone-a-thrust-vectoring-monocopter/
So a stick can hang in the sky in much the same way that bricks don’t?
Well there is the flying banana for starts, then the original mono blade is the Samara seed of maples. I think I saw something on YT about such a mono blade, of course it has to have a counter rotation prop as well as a counterbalance on that single lift blade.
Oh, but bricks in fact do indeed.
Look up the F4-Phantom, aka the flying brick, from 1958, the source of the famous quote, “a brick can fly if you stick a big enough engine on it.”
We did similar work to this back in 2016 using aerodynamic fins as a control method, called the Stackrotor: https://www.araa.asn.au/acra/acra2016/papers/pap123s1.pdf
It flew very well and we got nominated for best paper! :D
The construction reminds me a bit of the cartoon Alfred Jodocus Kwak, in which the professor had a flying windmill. ^^
Minimum complement of rotors? This very website has featured successful flying craft with *half* the rotors that this creation has!
AND half the number of blades on that rotor!
Oh sorry was looking at the video in the comments – a THIRD of the blades of the blades per rotor from the post
(What a saucy title!)
There was an interesting venture in this vein by Canadair back in the 70’s:
I’m just musing…
I couldn’t tell from the video, but putting the batteries and circuit boards INSIDE the stick might help?
“Can sticks fly?”
The folks that brought you the F4-Phantom proved in 1958 that given a big enough engine, anything can fly. The more accurate quote was “a brick can fly if you stick a big enough engine on it.”
It was fun to watch the video though :)
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