Sprag Clutches

Hilliard Sprag Clutches are designed for overrunning, backstopping and indexing applications. This clutch is a freewheeling device with an inner race and an outer race, either of which can be the input or output member. The input can drive the output in a chosen direction and permit the output to overrun in the same direction. The clutch consists of a cage full of steel sprags or wedges, located in the space between concentric inner and outer races. Power is transmitted from one race to the other by the wedging action of the sprags between them. Rotation in one direction causes the sprags to tilt and wedge, preventing rotation. This allows free rotation in the opposite direction.