Optimizing a Ratchet Gear
  The energetic efficiencies of rocked ratchets reported in the literature typically lie in the sub-percent range. We discuss the problem of optimization of the energetic efficiency of a ratchet, and show that considerably higher efficiencies can be achieved; however this assumes a fine-tuning of the parameters of the system. The domain of parameters corresponding to high efficiencies is typically narrow. 
I.M. Sokolov