TM 9-2350-256-34
0003 00
Main Winch Hydraulic Motor
The hydraulic motor (Figure 2) is mounted at the rear of the main winch on the underside of the manifold. It is a vane-type,
reversible motor which serves to convert hydraulic energy into rotary motion and torque. This torque is then transmitted to the
main winch. The hydraulic motor is a reversible, vane-type motor equipped with two identical inlet-outlet ports. Hydraulic
pressure induced at either of these inlet/outlet ports is forced through the vanes of the rotor, thus turning the rotor and the
shaft which is splined to it. The direction in which the motor rotates (i.e., clockwise or counterclockwise) depends on which
inlet/outlet port the hydraulic pressure was introduced, and is controlled by means of the main winch combination control valve
mounted on top of the motor manifold.
Winch Gear Train Operation
When the main winch control valve is in the INHAUL position, the hydraulic motor rotates in the clockwise direction (Figure 3)
and drives the winch bevel gear and pinion shaft, causing them to rotate clockwise also. (Gear direction of rotation is determined
by viewing the 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
coupling is 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 counterclockwise 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 countershaft gear which is spline-mounted to the countershaft, in
the clockwise direction. Also splined to the countershaft is a pinion. The pinion engages the drum gear assembly, thus causing
the cable drum to rotate in the counterclockwise or INHAUL direction. Placing the main winch control valve in the PAYOUT
position causes the hydraulic motor to rotate in the counterclockwise direction. All gears then rotate in the opposite direction
from that described above, and the cable drum rotates in the clockwise or PAYOUT direction.
Main Winch Brakes
The main winch brake cylinder (Figure 2) is located on the brake housing at the rear of the main winch. Within the cylinder is a
piston which is spring loaded to the applied position. The piston exerts force on the brake drum to prevent cable drum movement
in the HOLD position. The piston is backed off and the brake released by introducing hydraulic pressure into the brake cylinder.
The main winch brake (Figure 3) consists of a circular brake band which makes contact with the brake drum, and a ratchet and
pawl assembly which allows the drum to rotate only in the clockwise direction. The brake band is held in its normally applied
position by a spring-loaded piston in the brake cylinder. The brake is released by introducing hydraulic fluid into the brake
cylinder to overcome the spring force. When the cable is inhauled the brake band is in its normally applied position, and the
brake drum, which is not secured to the brake shaft, is held stationary. The two pawls, which are secured directly to the brake
shaft, rotate freely in the counterclockwise direction, thus enabling the cable drum to rotate in the counterclockwise or INHAUL
direction. When the main winch control valve is placed in the HOLD position, hydraulic motor power is balanced, cable drum
rotation ceases, and the brake band remains in its normally applied position. Any weight on the cable is prevented from slipping
by the pawls which engage the ratchet teeth on the inside diameter of the drum and prevent cable drum movement. The cable
is PAID OUT by introducing hydraulic pressure into the brake cylinder to counteract the piston spring pressure and release the
brake band. The entire brake drum assembly is then free to rotate in the clockwise , or PAYOUT direction, even though the pawls
within the brake drum remain engaged with the ratchet teeth.
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