Quad Copters Are So Last Year

[Nuke]

now you can get by with just 2 rotors. linky:

http://hackaday.com/2014/12/16/uav-coaxial-copter-uses-unique-drive-mechanism/

its rather clever. yaw control comes from the usual mechanism of varying torque between top and bottom rotors. but the top rotor uses a very clever hub mechanism. blade swing as a response to changes in torque can be used to vary the pitch of the blades at each of the cyclic points, and it does it all without a swashplate and servos. instead it does this by pulsing torque in phase with the motor hub rotation. damn clever if you ask me.

Edited December 19, 2014 by Nuke

[*Aqua*]

Interesting!

But this mechanism will put more stress on rotors and blades, won't it?

[Red Iron Crown]

That's a fairly standard way of controlling yaw in coaxial helicopters, the Russians have been doing it for years. Pretty cool to see it implemented in such a small package, though.

Edit: Er, I read "usual" as "unusual" in the OP. Carry on.

[Nuke]

Interesting!

But this mechanism will put more stress on rotors and blades, won't it?

it looks like the blades are free swinging on their axis. i dont think any more than any other rotor blades do. carbon fiber blades are really tough, flex well, and also really cheap. you might tear up some of the less flexible blades though. i think i would be more concerned with vibration. torque is being pulsed at about 1-4 times the motor frequency depending on which direction of cyclic is being applied. you just have to make sure all your materials have resonant frequencies outside of those harmonics, and i dont think that is a major issue for composites.

[Tommygun]

Make it larger and more robust so I can mow my lawn with it and I'll buy it.

[merendel]

Make it larger and more robust so I can mow my lawn with it and I'll buy it.

Oh that would be oh so safe and not ripe for abuse with horrific consequences. Ever played halflife 2? http://half-life.wikia.com/wiki/Manhack

Shudder those things still give me nightmares.