Abstract: An air clutch of the type having a friction drum secured to a first shaft and an inflatable annular tube concentrically surrounding said drum and carrying friction means for engagement with the drum upon inflation of the tube, is provided with a variable elastic coupling in the drum portion of the clutch. The coupling is comprised of an annular drum having a plurality of radially inwardly disposed plates extending in the axial direction and a hub member having a plurality of axially extending radially disposed plates thereon interdigitated with the plates on the drum. A bellows member is disposed between each pair of plates with the interior of the bellows being disposed in fluid communication with conduits running through the plates on the hub member. The conduits are connected to a common source of air pressure whereby the torsional rigidity of the coupling can be varied by varying the air pressure within the plurality of bellows.