[mechanicalbrain]

well if you gear it (and i admit the gears would need i bit of slop) correctly the sides will still be able to slide though i couldnt use servos without gearing them. actualy the im positive that if you gear all four of the gears (agian with a little slop) they would rotate perfectly and still slide. to test this im making some oversized wood ones. the concept isnt that impossible and i was believe imployed in some cars or at least that is what im told. to clarify the picture is misleading in that in not tapering that much. admitedly theres some math. it also helps to have fine teeth on the movine gears.