Power transmission

A rotary sliding vane pump or motor having a body comprising a central cam ring having circular arcs of major and minor diameters alternately spaced around its inner cam surface and connected by ramps along which fluid displacement can occur, said body further comprising end covers, means forming inlet and outlet terminals connected respectively with the ramps, a slotted rotor within the cam ring and carrying radially slidable vanes to traverse the inner cam ring surface, one or more cheek plates interposed between one or both end covers and the rotor, the vanes, and the stationary cam ring, the cheek plate or plates having a wear face of bearing material abutting the rotor and vanes wherein the wear face is a layer of bearing material formed on a harder metal back, the back being deformed over discrete limited areas to provide wearresistent contacts with the cam ring, whereby the wear between the cheek plate and the cam ring as it radially expands and contracts under intermittent pressure loads is reduced.