How to transfer mechanical power from the inside of a vacuum chamber to the outside while maintaining a seal? In a vacuum chamber how would one transfer mechanical power (either rotation or linear) from inside to the external environment?
I'm working on an idea for a new/different type of motor that would require an evacuated internal atmosphere and am wondering how to transfer the generated motion outside the case.
I have thought about using rotating magnetic coupling on either side of a thinned wall section but don't think it would scale well for larger versions of the motor (perhaps powering a bike or car). I expect with a high enough budget (which I don't have) that an extremely high-tolerance mechanical seal could be machined but am wondering if there are any solutions that could sidestep the high tolerances by thinking laterally.
 A: Second answer, what about the phenomenon of “Quantum Locking”? Right now it is being used to levitate superconductors over magnets, but I am sure you could exploit the phenomenon to transmit torque. Plus, you can put the superconductor on the vacuum side of the seal to keep it cold.
A: Might be overly complicated, but...
Put electrical generator inside vacuum chamber and drive it with the internal mechanical power;  pass electric current through conducting patches in chamber wall;  use current directly to drive motors in wheels of bike/car...
Cooling the generator could be a problem...
A: If you attach the motor so that it rotates the casing, then you can simply mechanically attach the casing to whatever it is that needs to be driven.  Not sure how you would implement this, but it is a rather lateral solution, if I do say so myself.
A: One standard way is a rotary fitting using a ferrofluidic seal.  These are fairly standard parts in your favorite vacuum components catalog.  Often used in semiconductor processing equipment.
A: Take a look at the torque converters of cars with automatic transmissions. They are rotational couplings where the working fluid is completely sealed from both the source and sink environments, so one of those could be vacuum. One shell of the device rotates inside the other, to the outer one could be stationary and form an integral (welded) part of the wall of the vessel which contains your power-producing device. The rotating seal has to keep the converter fluid at bay against ambient pressure, not total vacuum.
