I’m almost done rigging the canopy for a spaceship I’m making, and I’m pretty happy with it so far. The idea is that the gear turns and pulls the canopy back and forth along a track of teeth. Ideally this would actually be rigged the other way, so that moving the canopy back and forth makes the gear rotate appropriately. I can do the math easily enough. I just don’t know how to constrain this in blender, or if it even can be done. Worst case I can just animate the two bones separately so that they appear to be in sync.
I don’t know if this will be useful to this thread, but here is the model so far: http://www.pasteall.org/blend/42875 It is obviously very much an unfinished work.