The disc brake on the hydraulic motor (20) is of the spring-loaded, normally-on type. When the brake handle is
shifted to the OFF position, pressure is applied to release the brake. When the brake handle is returned to the ON
position, the pressure is released, and the brake is reapplied.
As the winch handle is shifted the pressure to the stroker is increased, shifting the swashplate angle in the pump
and causing the displacement of the pump, and therefore the flow from the pump, to increase. The winch handle is
spring-centered, so that when the handle is released the pump displacement and flow return automatically to zero.
The dual relief valve (17) protects the rotor (20) and winch structure from overloads. In the event of pressure in
excess of the motor rating, the dual relief valve will open to allow flow from the high pressure to the low pressure side of
the circuit, bypassing the motor. This feature is incorporated into the circuit to protect the structural and hydraulic winch
components from damage due to line pulls and pressures beyond their rated capabilities.
Two pressure gauges (7A) on the hydraulic power unit indicate the piston pump pressure on the high and low
pressure sides of the circuit, and another gauge (7B) indicates the charge pump pressure. A shuttle valve (19) on the
winch selects the higher pressure side to be indicated by the gauge (7A) next to the joystick.