  A great endeavor has been undertaken to engineer molecular rotors operated by
an electrical current. A frequently met operation principle is the transfer of
angular momentum taken from the incident flux. In this paper we present an
alternative driving agent that works also in situations where angular momentum
of the incoming flux is conserved. This situation arises typically with
molecular rotors that exhibit an easy axis of rotation. For quantitative
analysis we investigate here a classical model, where molecule and wires are
represented by a rigid curved path. We demonstrate that in the presence of
chirality the rotor generically undergoes a directed motion, provided that the
incident current exceeds a threshold value. Above threshold, the corresponding
rotation frequency (per incoming particle current) for helical geometries turns
out to be $2\pi m/M_1$, where $m/M_1$ is the ratio of the mass of an incident
charge carrier and the mass of the helix per winding number.
