I've been trying to figure out the best way to accomplish. My specific purpose is rotors, but I also just want to understand it in the general case. So far, it seems that there are 3 ways, none of them seem ideal:
- Use three, stacked powered wheels. The first one is fixed to the chassis and rotates. The second one is fixed to the first one and rotates in the opposite direction, creating a net rotation of 0. The 3rd one is fixed to the second one, and also rotates in the contra direction, create a net rotation. This seems kind of kludgy.
- Use a perpendicular powered cog which engages two unpowered cogs. This creates contra-rotation more elegantly, but has the theoretical disadvantage that the rotation must always be at the same speed. I have not tried this, but recall seeing a video of it, so I think it's possible to make work.
- Create two, stacked platforms fixed to the chassis, making sure that there's clearance for the rotor blades. Braces could be used, since they are non-interfering.