Abstract: An intermediate rotatable member is driven at relatively high speed about a common axis and is concentrically positioned between first and second relatively rotatable members, one of which is bidirectionally driven with respect to the other. Hydrodynamic fluid bearings are carried by the intermediate member on both surfaces thereof and acting on the first and second members, thus even upon cessation of motion, between said first and second members, there is no loss of the hydrodynamic fluid bearings between the first, second and third members.