I.C. engine starter motor pinion drive - has free wheel keeping pinion in mesh with flywheel when respective speeds are unequal

The starter pinion is fixed to a sleeve (5) able to move axially along the starter motor drive shaft (2) and turn with it in the usual way. The pinion has a flange (7) which acts as the inner race for a free wheel (8) whose ratchet (38) is moved into the locking position by a solenoid (42) when the starter switch is closed. The starter relay is actuated at the same time and the pinion moves forwards along the shaft by virtue of its pressure spring (32) and the spiral section on the drive shaft (5) until it reaches the stop (20) and engages with the fly wheel ring (22). The free wheel ratchet (38) drops out of mesh with the teeth (29) when the pinion sleeve moves forwards to slide inside a groove (30) between the free wheel and the brake disc (37).