Over Running Alternator Pulley

An Over Running Alternator Pulley is used to smooth out irregularities of driving speed of an automobile alternator. During normal operation alternator pulleys can rotate at up to 18,000rpm and coupled with rapid acceleration and deceleration can lead to premature alternator, pulley and drive belt failure. To prevent this Overrunning Alternator Pulleys (OAPs) were developed that are designed to decouple the alternator from the rotational irregularities of the crankshaft in an internal combustion engine, as the alternator has the highest moment of inertia in the accessory belt drive. As a result of this decoupling the alternator is only driven using the acceleration components of the rotational irregularity of the crankshaft.
The Over Running Alternator Pulley consists of a pulley, an overrunning clutch unit with a double bearing support, a drawn inner ring and outer ring and two sealing rings. For protection against heavy water impacts and other dirt contamination, a cover snap is fitted on the front side.