As long as the speed is greater than about 100 revolutions per minute (the exact value depends in part on available suction lift or suction head), centrifugal force is enough to keep the balls rolling along the track while fluid is drawn in.

This pump can be remarkably efficient, in part because no parts of the pump reciprocate (the reciprocal motion in the cylinders is due to the relative motion of the balls on their circle meshing with the rotor on its circle).

The track the balls revolve around is a dual track. The primary purpose of this track is to maintain the ball in constant radial alignment within its cylinder. It also serves to keep the balls from slipping along the outer housing.