TM5-3810-305-10
Winch Theory of Operation
The winch is made up of four basic assemblies:
winch base, hydraulic motor and brake valve,
brake cylinder and motor support, and drum
assembly. The hydraulic motor turns the gears in
the drum assembly, working the cable.
The winch has a dual braking system: a dynamic
brake and a static brake. These two types of
brakes work together to control the speed of the
drum assembly. The dynamic brake uses hy-
draulic pressure to operate the brake valve which
controls the flow of hydraulic oil to the hydraulic
motor, The static brake is made of multiple-
friction discs, a brake clutch assembly, and a
hydraulic piston and cylinder. The static brake is
automatically applied unless it is released by
brake valve pilot pressure at a level lower than
that required to open the pilot-operated spool
valve.
Either brake system does not affect the winch
during hoisting operations. When the operator’s
control is placed in neutral, rollers between the
cam and outer race wedge to prevent the drum
assembly from turning. The brake valve stops oil
flow from the hydraulic motor. For lowering a
load slowly, the operator can allow only enough
oil to release the brake without engaging the hy-
draulic motor. The heat build-up is dissipated by
the hydraulic oil. For faster lowering, the hy-
draulic pressure is increased by the operator to
both release the brake and engage the hydraulic
motor.
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