Abstract: A friction coupling apparatus contains a plurality of fluid motor actuators circumferentially fixed about a relatively rotatable shaft. Each of the actuators is positioned between a spaced pair of friction rotors fixed to the shaft for rotation therewith. The actuators each contain an annular axially distensible elastomeric air tube, which upon pressurization operates to force pairs of friction members against the rotors for establishing frictional communication between the shaft and a relatively fixed support member. In a preferred embodiment, the elastomeric air tube contains a pair of axially spaced apertures. Each aperture defines a circumferential sealing edge by which one of a pair of air pistons is supported. Each piston contains a circumferential groove which sealingly mates with one of the edges, the pistons positioned to bear directly against the friction members.