9262. Royce, F. H., and Rolls-Royce, Ltd. April 13. Securing gear-wheels on shafts.-Gear-wheels for fluid-pressure engines are elastically driven and are also combined with frictionally-driven fly-wheels. The crank-shaft a has keyed thereto a boss b which carries a radial flange b<1> integral with a sleeve b<2>. A ring d is keyed inside the sleeve and has projections alternating with those on a sleeve h carried by the gear-wheel g. Elastic buffers, such as springs, are placed between the two sets of projections. Externally, the sleeve b<2> is provided with a disk p, against the opposite sides of which disks p<1>, p<2> are pressed by spring couplings r, s, disks t of wear-preventing material being interposed. The chamber c is closed by a two-part disk n.