If you have enough heat to make it click forward, you also get random bounces on the prawl which themselves make it go in reverse as much as forward.
http://en.wikipedia.org/wiki/Brownian_ratchet
If you have enough heat to make it click forward, you also get random bounces on the prawl which themselves make it go in reverse as much as forward.
http://en.wikipedia.org/wiki/Brownian_ratchet