DEMO - 1965 Ford Truck Shop Manual - ForelPublishing.com

2-30 GROUP 2 - BRAKES
DRIVE SHAFT
PARKING BRAKE
ACTUATING LEVER
BRAKE
SHOE
Fig. 23, Part 2-7, except that the
pressure housing is replaced by the
Fail-Safe unit (Fig. 4).
FAIL-SAFE PISTON
FAIL-SAFE
PRESSURE
CHAMBER
ACTUATING SPRING
HOUSING CAP
BACK VIEW
PARKING
BRAKE
DRUM
LOWER
RETAINING
SPRING FRONT VIEW H1009 . B
FIG. 2-Shoe-Type Parking Brake-Nine-inch Diameter Drum
MAXIBRAKE
On trucks equipped with full air
brakes, a Maxibrake emergency stop
safety feature is available.
The Maxibrake air brake chamber
(used on the rear axle only) is much
like the conventional brake chamber,
and differs only in that it contains an
independently operated spring loaded
piston which, when released due
to low air pressure, will set the service
brakes (Fig. 3).
System air pressure applied to the
safety chamber and piston keeps the
safety piston spring compressed,
while metered pressure from the
service brake control valve applies
against the diaphragm and service
push rod for normal service operation
(Fig. 9). In case of system pressure
loss, the safety piston spring
will release against the safety piston
and push rod for automatic application
of the brakes.
If air pressure cannot be restored,
SAFETY PISTON SPRING SUPPORT-
PRESSURE PLATE*
CLAMP RING,
it will be necessary to compress the
safety spring by introducing pressure
from an auxiliary source so that
the truck can be moved. Connect
the auxiliary air line to the emergency
air supply valve which is located
near the brake chambers. Turn
the valve handle 90 degrees to cut
off the normal air supply system and
open the auxiliary system. This
action admits air to release the Maxibrakes,
but prevents the air from
escaping through the break-down
area.
A manual control valve located in
the cab exhausts the air from the
safety chamber for safety stops, or
to set the service brakes for parking.
FAIL-SAFE—SPRING BRAKE
The Fail-Safe unit combines normal
brake operation with parking
and safety brake action. The Stopmaster
brake with the Fail-Safe assembly
is the same as that shown in
PUSH ROD RETURN SPRING
PUSH ROD
SAFETY PISTON
SPRING
SEAL
NORMAL
OPERATING
PRESSURE
PLATE AND
PUSH ROD
CLAMP RING
PRESSURE LINE
CONNECTIONS
DIAPHRAGM
NON-PRESSURE
HOUSING
SPRING COMPRESSED-
NORMAL OPERATING POSITION
LOCK -SSESETfer 'RELEASE
CLIP
FAIL-SAF
PISTON
PLATE AND
PUSH ROD
BOLT
SPRING
SPRING RELEASED—EMERGENCY OR
PARK-APPLIED POSITION
HI 25o~A
FIG. 4 - Fail-Safe Operation
NORMAL OPERATION
There are three air pressure line
connections on the Fail-Safe housing.
The two outer connections allow
SLACK SAFETY SAFETY
ADJUSTER CHAMBER PISTON
DIAPHRAGM
MOVING TRUCK
FIG. 3—Maxibrake Operation
PARK OR EMERGENCY STOP
H1254-A