THEORY OF OPERATION - CONTINUED
AIR AND BRAKE SYSTEMS - CONTINUED
Service Brakes. All-wheel, air-activated, drum brakes with floating-type linings and cam actuators. A foot-operated
control valve in the operator compartment controls the system.
Parking/Emergency Brakes. The parking/emergency brakes operate all wheels using the same actuators as the service
brakes. When the parking/emergency brake control knob is pulled out, air pressure is exhausted from the brake cylinder
and spring pressure is applied. When the control knob is pressed in, air pressure is applied to the cylinder and the park-
ing brake is released. A spring override actuates brakes in the event of low air pressure or broken air lines. This override
is deactivated when the system air pressure is above 60 psi (414 kPa). A warning horn sounds in operator compartment
when system air pressure falls below 65 psi (448 kPa).
The electrical system consists of two 12-volt batteries connected in series, with negative grounding, providing 24 volts
to operate the electrical systems and components.
The system contains all the necessary switches, circuit breakers, fuses, relays, harnesses and connectors to operate the
machine, including a NATO slave receptacle.
The three major systems comprising the electrical system are:
Service, work and blackout lights
The machine hydraulic system supports both steering and scraper hydraulic systems.
The hydraulic system consists of a vane-type pump and a gear-type pump; control, check and spool type valves;
filters; hydraulic motor; lines, hoses and fittings; oil cooler; and hydraulic reservoir. The vane-type pump mounted
on the differential provides hydraulic system pressure for the bowl, ejector and apron controls. The gear-type pump
(supplemental steering pump), located beneath engine on front of differential case and frame, adds to the volume
of flow in the scraper hydraulics. Since this pump is ground-driven by forward motion of machine, the amount of
oil it adds is directly proportional to machine speed. If the vane-type pump looses drive power, then the supple-
mental steering pump supplies hydraulics for operation of steering only. This allows the machine, in motion, to be
steered safely to a stop.
Steering System. The steering system is divided into two separate systems, a primary system and a supplemental sys-
tem. The primary system shares the main hydraulic circuit with the cylinders for bowl, ejector and the apron control. A
vane-type two-stage pump powers the primary steering system. A separate, ground-driven hydraulic pump powers the
supplemental steering system. Both systems operate from a common reservoir.
Scraper Hydraulic System. The scraper hydraulic system consists of three primary hydraulic circuits to support
scraper operations: bowl circuit for raising and lowering the bowl; ejector circuit for ejecting material from the bowl;
and apron circuit for raising and lowering the apron.
END OF WORK PACKAGE