A molecular motor is introduced which is composed of charges only and which does not contain any potential or interaction besides the Coulomb one. The motor is shown to transform efficiently a driven random rotation into a directed translational motion. The direction of translational motion can be chosen dynamically, so that a “forward gear,” a “reverse gear,” and even a “neutral gear” exist. The high efficiency stems from the fact that this motor only steps in the direction determined by the chosen gear.

• Received 13 September 2000

DOI:https://doi.org/10.1103/PhysRevE.63.030102