TM 5-3810-300-24 & P2
As the piston begins its upward stroke, the air that was drawn into the cylinder on the down stroke is being compressed.
Air pressure on top of the inlet valve plus the force of its spring, returns the inlet valve to its seat. The piston continues
the upward stroke and compressed air then flows by the open discharge valve, into the discharge line and on to the
reservoirs. As the piston reaches the top of its stroke and starts down, the discharge valve spring and air pressure in the
discharge line returns the discharge valve to its seat. This prevents the compressed air in the discharge line from
returning to the cylinder bore as the intake and compression cycle is repeated.
Non-Compression of Air (Unloaded). (Illus. 4-19C). When air pressure in the reservoir reaches the cut-out setting of the
governor, the governor allows air to pass from the reservoir into the cavity beneath the unloader pistons. This lifts the
unloader pistons and plungers. The plungers move up and hold the inlet valves off their seats.
With the inlet valves held off their seats by the unloader pistons and plungers air is pumped back and forth between the
two cylinders. When air is used from the reservoir and the pressure drops to the cut-in setting of the governor, the loader
saddle spring forces the saddle, pistons and plungers down and the inlet valves return to their seats. Compression is
then resumed.
Brakes. (Illus. 4-19).
The brakes are mounted on the 8 wheels of the Carrier. The front brakes are 15" x 6" and the rear brakes are 15" x 7".
Air to operate the brakes is provided by the engine driven compressor of the Air System. A brake pedal in the Carrier
when depressed allows air flow to the brake assemblies.
The brakes used on the Carrier are wedge actuated. The brake shoes are automatically adjusted for wear. A fail safe
feature is incorporated on brakes of the rear axle. When air pressure is removed from the failsafe unit a spring forces a
piston against a diaphragm plate and the brakes are applied.
Brake Assembly.
The brake assemblies used are Stopmasters. The description that follows will describe an earlier model brake assembly
although a later model may be found in the field. The illustrations that accompany the text will show both types.
Operation of both models is the same.
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