SUB-SECTION 4A
HYDRAULIC SYSTEM
When the selector switch is in the high speed position, the
When the winch control lever is moved to the lower posi-
tion, the winch brake valve spool is shifted, blocking the
winch speed selector valve is energized, causing the valving
within the motor to shift to the closed position. This pre-
tank port while allowing the oil to flow from the swing
vents oil from flowing through both sections of the motor.
pump to the winch brake cylinder. Pressure developed in
Since all the oil flow from the control valve must now pass
the cylinder will then release the winch brake.
through one section of the motor, the motor will develop
low torque at a high speed.
NOTE
The winch brake is not released when the winch is
operated in the raising direction. A Sprag clutch
When the winch control lever is pushed fully forward, the
allows the motor to drive the winch drum through
oil in the circuit will recirculate from the motor, through
the brake disc.
the control valve and back to the inlet of the motor. This
will cause the load to lower under controlled free-fall con-
A two speed, gear type motor is used to drive the winch.
ditions.
When the winch speed selector switch in the cab is in the
low speed position, the winch speed selector valve is de-
energized, allowing the valving within the motor to shift to
AUXILIARY WINCH CIRCUIT. The operation of the aux-
the open position. This allows the oil supplied to the motor
iliary winch circuit is the same as the operation of the main
by the control valve to flow through both motor sections,
winch circuit. Refer to the above description.
producing high torque at low speed.
4A-18
