DEMO - 1965 Ford Truck Shop Manual - ForelPublishing.com

PART
2-6
AIR SUPPLY SYSTEM
Section
Page
1 Description and Operation
Compressor
2-67
2-67
Governor 2-67
2 In-Truck Adjustments and Repairs 2-68
Air Compressor Drive Belt Adjustment. .. . 2-68
Governor Adjustment 2-68
Air Reservoir Safety Valve 2-69
3 Removal and Installation. 2-69
Vertically-Mounted Compressor—
With Gas-Engine Trucks 2-69
2-67
Section
Page
Side-Mounted Compressor—
With Gas-Engine Trucks 2-69
Air Compressor With Ford Diesel Engines.. 2-70
Air Compressor—Cummins Diesel
N-H Series Engines 2-70
Air Compressor—Cummins Diesel
V-6 Engines 2-71
Governor 2-73
Pressure Indicator Valve. , 2-73
4 Major Repair Operations (Not Applicable)... 2-73
DESCRIPTION AND OPERATION
The same air supply system is
used with either the air-hydraulic
booster brake system (Part 2-5) or
the full air brake system (Part 2-7).
In the air-hydraulic booster system,
air pressure increases or "boosts"
the hydraulic pressure applied to the
shoes. In the full air system, air pressure
is applied directly to the shoes
through a diaphragm and mechanical
linkage.
The air supply system consists of
the compressor, reservoirs, governor,
low pressure indicator and dash
gauge.
The compressing action of the
compressor is controlled by the governor.
When reservoir air pressure
reaches 100-105 pounds, the gover-
D1SCHARGE VALVE
FIG. 1 —Air Compressor Operation
nor cuts out the compressor. When
reservoir pressure drops to 80-85
pounds, the governor allows the
compressor to cut in again. When
reservoir air pressure drops below
60 pounds, the low pressure indicator
valve closes an electrical circuit
to a warning buzzer.
COMPRESSOR
The compressor is a two-piston air
pump with an engine pressure lubricating
system and water cooled cylinder
head and block (Fig. 1).
During the downward stroke of
the compressor pistons, a partial
vacuum is created above the piston
and inlet valve. This vacuum above
the inlet valve together with the at-
RESERVOIR
mospheric pressure below the valve
automatically opens the inlet valve
and allows air to be drawn through
the intake filter (air pick up tube on
SD V-8 engines) into the cylinder
above the piston.
As the piston starts moving upward,
the air is compressed, and the
air pressure on top of the inlet valve
together with the inlet valve spring
force automatically closes the inlet
valve (Fig. 1). As the piston continues
moving upward, the air is
further compressed until the pressure
lifts the discharge valve and allows
the air to enter the reservoir. As each
piston starts its downward stroke, the
discharge valve closes to prevent the
compressed air from returning to
the cylinder.
GOVERNOR
The governor (Fig. 2), operating
in conjunction with the compressor
unloading mechanism, automatically
controls the air pressure in the air
brake or air supply system between
the desired, predetermined maximum
and minimum pressures. The compressor
runs continually while the
engine runs, but the actual compression
of air is controlled by the governor
which stops or starts compression
when the maximum or minimum
reservoir pressures are reached.
The D-2 governor has a piston upon
which air pressure acts to overcome
the pressure setting spring and control
the inlet and exhaust valve to
either admit or exhaust air to or
from the compressor unloading
mechanism.