TM 9-2350-256-34-2
energy into rotary motion and torque. This torque is then transmitted to the hoist winch. (See (b) above).
(e) Hoist winch brake cylinder (fig. 1-7). The hoist winch brake cylinder is located on the brake housing
at the front of the hoist winch. Within the cylinder is a piston which is springloaded to the applied position. The
piston exerts force on the brake drum to prevent drum movement in the HOLD position. The piston is backed
off, and the brake released, by introducing hydraulic pressure into the brake cylinder.
(2) Operation.
(a) Hoist winch hydraulic motor operation. Hoist winch hydraulic motor operation is the same as main
winch hydraulic motor operation. Refer to paragraph 1-3b.
(b) Winch gear train operation. When the hoist winch control valve is in the RAISE position, the
hydraulic motor rotates in the counterclockwise direction (fig. 1-9) and drives the winch bevel gear and pinion
gear, causing them to rotate counterclockwise. (Gear direction of rotation is determined by viewing the hoist
winch from the brake assembly side). The pinion gear is splined to the pinion shaft and thus drives the shaft in
the same direction. As the pinion shaft rotates, the geared end of the shaft engages the low speed gear and
the pinion gear engages the high speed gear, both of which rotate freely around the brake shaft. Between the
high and low speed gears, and splined to the brake shaft, is the gear clutch. The external teeth of the gear
clutch are meshed with the internal teeth of the gear coupling. This couplingis positioned either left or right in
order to couple the gear clutch with either the high or low speed gear, thus causing the brake shaft to rotate in
the clockwise direction. The splined end of the brake shaft drives the brake drum assembly, while the geared
end of the shaft meshes with and drives the drum gear in a counterclockwise direction. The drum gear then
rotates the cable drum in a counterclockwise direction to raise the winch cable. Placing the hoist winch control
valve in the LOWER position causes the hydraulic motor to rotate in a clockwise direction. All gears then
rotate in the opposite direction from that described above and the cable drum rotates clockwise to lower the
winch cable.
1-11
