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| Illustration 1 | g02958758 |
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Typical example (1) Air starting motor (2) Air inlet (3) Control valve (4) Starting motor solenoid | |
When the main supply of pressurized air is ON, pressurized air is provided to the control valve. The main supply of pressurized air is blocked by the control valve. The control valve allows some control air pressure to flow through the control valve to the starting motor solenoid .
When the normally closed starting motor solenoid is activated for start-up, the solenoid opens the connected valve. The valve allows the control air pressure to flow behind the piston inside the air starting motor.
The pressurized air causes the turbine to rotate. The rotor uses the reduction gears to rotate the drive shaft for the pinion. The pinion rotates the flywheel in order to crank the engine.
When the engine starts to run, the flywheel will begin to rotate faster than the pinion. The design of the drive shaft for the pinion allows the pinion to move away from the flywheel. This action prevents damage to the air starting motor, to the pinion, and to the flywheel ring gear.
When the engine control senses the crank terminate speed, starting motor solenoid (4) is de-energized. The control valve closes in order to shut off the main supply of pressurized air to the starting motor.