5-3.
Brake System Operation
(1) Connect both the EMERGENCY and
a. Driving Normally.
There are three
SERVICE BRAKE systems at the rear of the truck crane
positions of EMERGENCY-RELEASE-PARK lever (fig.
to the vehicle to be towed.
(2) Place lever (fig. 5-1, item 16) in the
the work site in the RELEASE position, stop the carrier,
EMERGENCY position and run the engine until the
andplace the control in the EMERGENCY
carrier air pressure is at least 50 psi. It is recommended
position. This position is used for short term parking.
that the towed vehicle not be moved until it reaches
When ready to move, flip the control to the RELEASE
normal system pressure. When the low air pressure flag
position and drive away.
rises, place the lever in the release 'position.
b. Overnight parking. When through working
(3) Depress .valve (15, fig. 5-1). The towed
for the day, or v hen intermediate term parking (several
vehicle brakes will now operate when the carrier air
hours) i required, drive to the point where the carrier will
brakes operate, and the carrier can be driven normally.
be parked. Stop the carrier and place the lever (fig. 5-1,
The trailer brake lever (31, fig. 5-1) is used to apply the
item 16) in the PARK position. This will drain air
brakes on the towed vehicle only. Be careful to avoid too
pressure from the system and mechanically engage the
much speed on grades and use more caution than usual
carrier brakes. When ready to move the carrier again,
when towing another vehicle.
start the engine, place the lever in the EMERGENCY
position, and wait until the low pressure indicator flag (fig,
5-4.
Front Axle Drive
5-1 item 41) goes up. This may take as much as five
a. General. The use of the driving front axle should
minutes, and there may be an interval It at about 95 psi
be restricted to off highway or very rough or slippery
air pressure when the charging seems to slow down.
conditions. When front axle drive is used, the operator
This is normal and should be overlooked Also, the low air
should also consider engaging the interaxle differential
pressure buzzer will be shut off tile air pressure is rising,
lockout, as well as the SLIPPERY R'OAD position of item
and this buzzer can not shut off. When the low air
18, figure 5-1.
pressure flag goes up, place the lever in the RELEASE
b. Engaging Front Axle Drive. To engage the front
position and drive the carrier normally.
axle drive, proceed as follows:
c. Park Abort. When it is necessary to park the
(1) Stop the vehicle completely.
carrier for more than eight hours, in extreme cold, or
(2) Shift the transfer case into the LOW
under damp conditions, it is placed in the PARK ABORT
position.
condition by means of item 12, figure 5-1. Under these e
(3) Shift the front axle control lever (40, fig.
circumstances, the air supply is bled out of the entire
system and the brake shoes are mechanically prevented
(4) Shift the main transmission lever to the
from coming in contact with the brake drums.
desired starting position and bring the carrier up to
operating speed in the usual manner.
Warning. While in the park abort condition, the
carrier will have no brakes. Always block the wheels
c. Disengaging Front Axle Drive. Disengage front
so as to prevent truck crane motion before placing
axle drive as follows:
the machine in the park abort condition. Do not
(1) Stop the carrier.
remove blocking until the carrier is returned to
(2) Shift the transfer case into the HIGH
normal brake system operation as follows:
range.
(3) Shift the front axle control lever to the
(1) Start engine.
OUT position.
(2) Place lever (fig.
(4) Bring the carrier up to speed, using the
EMERGENCY position and run engine until the low air
main transmission shift lever.
pressure flag rises, indicating system pressure is within
the operating range.
5-5.
Starting
(3) Place the lever in the RELEASE position.
a. Preparation for Starting.
The carrier brake system is now ready for normal
operation.
(1) Perform the pre-operation services (para
d. Towing Another Vehicle. To tow another
(2) Lubricate the carrier as specified in the
vehicle, proceed as follows:
current LO.
b. Starting. Refer to figure 5-2 and start the carrier.
5-4
