Operation and maintenance manual

Section 250-0000
SM 2155 Rev 1 10-03
1
BRAKING SYSTEM - Braking System Schematic
DESCRIPTION
Numbers in parentheses refer to Figs. 2 through 5.
The hydraulic braking system is of closed centre
design wherein constant pressure is stored in
accumulators and is regulated as required to retard or
stop the machine.
A brief description of the individual components used
in the braking system are listed below. Detailed
service and operating instructions can be found in the
relevant component sections of this manual.
Service Brakes
Refer to Section 165-0015, BRAKE ASSY - OCDB.
The service brakes are of the enclosed, forced oil-
cooled multiple disc type. The service brakes are
actuated by hydraulic oil as specified in Section 300-
0020, LUBRICATION SYSTEM. DO NOT use BRAKE
FLUID (J 1703). Multiple discs within the brake packs
are cooled by brake cooling oil as specified in Section
300-0020, LUBRICATION SYSTEM.
The brake pack is bolted to the stub axle and houses a
sandwich of friction discs splined to a hub rotor. There
are six friction discs in each of the front axle brake
packs, four in the centre and rear axle brake packs.
When the treadle valve is actuated, hydraulic oil enters
the brake pack and forces the piston against the
rotating friction discs which react with stationary stator
plates. The stator plates are retained by scalloped
tangs at the outside diameter, which in turn transfers
the reaction torque to the rigid outside housing, slowing
or stopping wheel rotation.
In an emergency situation, application of the park/
emergency valve will actuate the service brakes and
the parking brake to bring the machine to a halt. In this
condition, a restriction in the 'Px' line from the brake
manifold valve will slow oil flow from the parking brake
allowing the service brakes to actuate momentarily
ahead of the parking brake.
Parking Brake
Refer to Section 170-0010, PARKING BRAKE AND
MOUNTING.
The parking brake consists of a sliding calliper acting
on a brake disc on a rear driveline and is of 'Inverted
Design' i.e. requiring pressure to hold it off.
Operation is by a spring applied/hydraulically released
actuator. The actuator is connected through a slack
adjuster to the power screw shaft that is screwed into the
piston in the calliper head assembly. The calliper head
assembly slides on anchor plate guides in a bracket
assembly bolted to the trailer frame.
A push control on the right hand dash panel activates
the solenoid on the brake manifold valve controlling oil
pressure from the front brake circuit accumulator to the
actuator. Application of the push control releases oil
from the actuator allowing internal springs in the
actuator to apply the parking brake. Pulling out the
push control directs oil pressure from the front brake
circuit accumulator to the actuator, compressing
internal springs, to release the parking brake.
In an emergency situation, application of the park/
emergency valve will actuate the service brakes and
the parking brake to bring the machine to a halt. In this
condition, a restriction in the 'Px' line from the brake
manifold valve will slow oil flow from the parking brake
allowing the service brakes to actuate momentarily
ahead of the parking brake.
Hydraulic Tank
Refer to Section 230-0040, HYDRAULIC TANK.
The hydraulic tank is the common reservoir for the
steering, body hoist and brake actuation systems. It is
mounted off the frame and fender bracket at the rear
right hand side of the tractor.
Integral with the hydraulic tank assembly are the
hydraulic oil filter, oil strainer and oil level sight
gauge. Located on the top of the tank assembly is the
filler cap and breather.
Triple Pump (1)
Refer to Section 250-0040, TRIPLE PUMP.
The triple pump is mounted off the transmission power
takeoff. It is a triple gear type pump, which supplies
various circuits:
a) front section (closest to driveshaft) supplies brake
actuation circuit and engine cooling circuit.
b) middle section combines with front section to
supply engine cooling circuit.
c) rear section supplies the brake cooling circuit.
The triple pump is assembled for left hand (anticlockwise)
rotation, as viewed from the driveshaft end.