Ratchet/slip bearing?

[greencactus3]

how large a one do you need? you can buy small one way bearings for rc cars (oneway pulleys/oneway diffs) in many hobby stores

[coreyjon]

-Or if you have any of the old bikes around, you could always find away to salvage just the clutch bearing-Or, you can order a nice shiny new one from McMC. I've used them in the past in projects not relating to robotics, and last year when I wanted a unidirectional drive system for the robot ascender, so that it would not backdrive both globe motors, I used a system found on many boat trailers, It was possible to back drive, by pulling the spring loaded latch back - and forcing it all the way up to hit a saftey limit switch (so that the drivers couldnt try to fight the one way mechanism in game) then you could run the system backwards to rewind the spool. What do you have in mind for the clutch bearing? that is if it isnt top secret.