An apparatus for selectively transmitting power between a rotating shaft and a belt including an integral brake member. The apparatus includes a pulley affixed to the shaft and which frictionally engages the belt. The pulley includes a pair of sheave halves which are reciprocable axially with respect to each other between belt engaged and disengaged positions. The integral brake member is mounted about the shaft between the sheave halves and affixed against rotation with the shaft. In the disengaged position the belt drops onto the brake member and is brought to a rapid stop.