PLATE AS-GOVERNOR 2P8707 - Caterpillar

The starting motor is used to turn the engine flywheel in order to get the engine running.
Illustration 1 g00285113
Cross section of the starting motor (typical example) (1) Field windings (2) Starting motor solenoid (3) Clutch (4) Pinion (5) Commutator (6) Brush assembly (7) ArmatureThe starting motor has a starting motor solenoid (2). When the start switch is activated, electricity will flow through field windings (1) of the solenoid. The solenoid core will move in order to push pinion (4) with a mechanical linkage. This will engage with the ring gear on the flywheel of the engine. The pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starting motor. When the circuit between the battery and the starting motor is complete, the pinion will turn the engine flywheel. A clutch gives protection to the starting motor. The engine can not turn the starting motor too fast. When the start switch is released, the pinion will move away from the flywheel ring gear.The starting motor is protected from damage in two ways:
The starting motor is protected from engagement with the flywheel when the engine is running. The control feature will not allow the starting motor to engage if the engine speed is above 0 rpm.
The starting motor is protected from continued operation. The operator is not allowed to hold the key in the start position after the engine has been started. This is accomplished by disengaging the starting motor solenoid after engine speed reaches 300 rpm.