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| Illustration 1 | g00499582 |
Air Starting Motor (1) Control valve. (2) Lubricator. (3) Relay valve. (4) Air starting motor. | |
The air starting motor is on the right side of the engine. Normally, the air for the starting motor is stored in a storage tank which is filled by an air compressor. The air compressor is installed on the left front of the engine. The air storage tank holds 297 L (10.5 ft3) of air at 1720 kPa (250 psi) when the tank is filled.
For engines that do not have excessive loads during start-up, the regulator setting is approximately 690 kPa (100 psi). This setting is a favorable compromise between the following conditions:
- The engine cranking speeds that are needed to start the engine
- Volume of air in the storage tank
For engines that have excessive loads, which cannot be disconnected during start-up, the setting of the air pressure regulating valve needs to be increased in order to generate the speed that is needed to start the engine easily.
Air consumption is directly related to the speed. Also, the air pressure is related to the force that is needed to turn the engine flywheel. If necessary, the air pressure regulator can be adjusted to 1030 kPa (150 psi) in order to produce the cranking speed that is needed to start an excessively loaded engine. With the correct setting, the air starting motor can turn the excessively loaded engine as fast as an engine that does not have an excessive load. Also with the correct setting, the air starting motor can turn the excessively loaded engine as long as an engine that does not have an excessive load.
Other air supplies can be used with the correct pressure and volume. For good life of the air starting motor, the air supply should be free of dirt and water. The maximum pressure for use in the air starting motor is 1030 kPa (150 psi). Higher pressures can cause problems.
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| Illustration 2 | g00493695 |
Air Starting Motor (5) Vanes. (6) Gear. (7) Pinion spring. (8) Pinion. (9) Rotor. (10) Piston. | |
The air from the supply goes to relay valve (3). Control valve (1) is connected to the line before the relay valve (3). The flow of air is stopped by relay valve (3) until control valve (1) is activated. Then, air from control valve (1) goes to piston (10) and behind pinion (8) for the starting motor. The air pressure on piston (10) compresses spring (7). Also, the air pressure on piston (10) engages pinion (8) with the flywheel gear. When the pinion is in engagement, air can go out through another line to relay valve (3). The air activates relay valve (3) which opens the supply line to the air starting motor.
The flow of air goes through lubricator (2) in order to pick up lubrication oil for the air starting motor.
The air with lubrication oil goes into the air motor. The pressure of the air pushes vanes (5) in rotor (9). This turns the rotor which is connected by gear (6) to pinion (8) which turns the engine flywheel.
When the engine starts running the flywheel will start to turn faster than pinion (8). Pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or the flywheel gear.
When control valve (1) is released, the air pressure and flow to piston (10) behind pinion (8) is stopped. Pinion spring (7) retracts pinion (8). Relay valve (3) stops the flow of air to the air starting motor.