TM 5-3805-248-23-1
THEORY OF OPERATION - CONTINUED
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AIR SYSTEM - CONTINUED
Air Dryer. The air dryer is used to remove moisture and foreign material from the compressed air before it gets to the
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air reservoir. Desiccant beads, used in the drying bed, clean and dry the air.
The air dryer is installed vertically in the air line between the air compressor and the first air reservoir. It is mounted on
the front of exterior cab.
Apron Control Valve. The apron control valve is linked to the bowl control lever at the operator compartment. When
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the bowl lever is moved forward, this valve routes air pressure to the apron control spool and simultaneously closes
apron while bowl is being lifted.
Quick Disconnect Connector. The quick disconnect connector provides easy access to the air system. This is used to
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attach an air hose for tire inflation.
BRAKE SYSTEM
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The brake system consists of three separate operating systems.
Service Brakes. All-wheel, air-activated, drum brakes with floating-type linings and cam actuators. Operation is
1.
achieved by a foot-operated treadle valve in the operator compartment.
2.
Parking/Emergency Brakes. The parking/emergency brakes operate all wheels using the same actuators as the service
brakes. A spring override actuates brakes in the event of low air pressure or broken air lines. This override is deactivated
when the system air pressure is above 60 psi. A warning horn sounds in operator compartment when system air pressure
falls below 65 psi.
Retarder. A hydraulic retarder is used to assist in braking action. When activated, it reduces forward motion and elimi-
3.
nates excessive use of the brakes.
The retarder housing and retarder control valve are fastened to the flywheel housing of the engine.
The operation of the retarder is similar to that of a torque converter. The rotor, fastened to a drive gear, throws oil against
the stationary vanes of the stator. This creates resistance, which works to slow the driveshaft and brake the machine. The
oil flow to the retarder is controlled by the air retarder valve on the steering column.
WHEELS
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The entire vehicle operates on steel-belted, heavy-duty, construction-grade tires seated on wheel assemblies. The wheel
assemblies have sealed, liquid-filled cooling compartments that assist in cooling during heavy braking.
STEERING SYSTEM
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The steering system is divided into two separate, yet shared systems: 1) primary steering, and 2) emergency/supplemen-
tal steering. The primary steering system shares the main hydraulic circuit with the cylinders for the bowl, ejector and apron
systems. Power is provided by a two-stage implement and hydraulic pump. The emergency/supplemental steering system is
powered by a separate, ground-driven hydraulic pump. Both systems operate from a common reservoir.
Primary Steering. With engine running, hydraulic power for steering is provided by one stage of the implement and
1.
steering hydraulic pump.
2.
Supplemental Steering. Supplemental steering is an emergency back-up system that enables the operator to safely steer
the machine to a stop with engine off or in case of hydraulic pump failure. The supplemental steering pump is a two-sec-
tion pump that is mounted on the front differential case and frame. The supplemental steering pump is driven by the ring
gear of the differential as the wheels turn.
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