Freewheels are machine elements with particular characteristics:

• In one direction of rotation there is no contact between the inner and outer ring; the freewheel is in freewheeling operation.

• In the other direction of rotation there is contact between the inner and outer ring; in this direction it is possible to transmit high torque.

For example the outer ring of the freewheel shown in figure 4-1 can freewheel clockwise while the inner ring is stationary. If, however, the outer ring is turned in the opposite direction, there is contact between the inner and outer ring and the inner ring is driven (driving operation).

Freewheels are used as:

• Backstops

• Overrunning Clutches

• Indexing Freewheels