An interesting question! As a guess, there should be some slack and elasticity in the last two gears or so, which you could get out if you used enough force. B

An interesting question! As a guess, there should be some slack and elasticity in the last two gears or so, which you could get out if you used enough force. Beyond that, the effective torque is reduced by 100x or 1000x already, which means moving any further gear even by the width of an atom would probably require more torque than the final gear can bear, and either the teeth or some other weak point would fail on the last gear. Of course, even what motion there is (up to failure) would be hard to observe. Moreover, putting this much torque on the end of the structure would also likely torque the entire machine end to end (like twisting a rope) and generally mess things up in uninteresting ways. Putting all that together, I think an observer would probably say nothing is moving, right until the last gear and/or entire structure fails spectacularly.