Abstract: A drive power transmission element in which a wheel has a peripheral surface provided with a unique groove structure for receiving a power transmission element such as a drive belt, rope, cable, or other compressible element. The wheel is provided with a groove having a particular configuration in the shape of a trochoidal curve. Since the compressible element or belt is of a compressible material, the drive belt or compressible element will be compressed into the groove of the drive wheel so that it is driven by compression of the belt or element, not friction.