Abstract: A continuously variable diameter pulley includes a cylindrical hub mounted on a drive shaft for rotation therewith. A plurality of vanes have stem portions slidably journaled through radial apertures in the hub for slidable movement radially inwardly and outwardly in the hub. The vanes include head portions which form an outer circumferential drive surface around the hub. A first apparatus for sliding the vanes radially outwardly includes a cone slidably mounted on the drive shaft for rotation therewith and for slidable movement longitudinally along the drive shaft. The cone is slidable into a central cavity formed in the hub, with the conic surface of the cone contacting beveled inward ends of the vanes, to force the vanes outwardly as the cone is pushed into the hub cavity. A second apparatus for extending the vanes radially outwardly from the hub includes a disk-shaped plate with a plurality of radially extending apertures and a plurality of hydraulic fluid wells.