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| Illustration 1 | g00695134 |
(1) Shaft (2) Cam ring (3) Piston (4) Rollers (5) Cylinder block (6) Distributor (7) Valve housing (8) Displacement control spool (9) Brake discs and brake plates (10) Brake piston (11) Spring | |
The wheel propel motor is a two-speed radial piston motor. Oil is supplied to the wheel propel motor by the propel pump. The angle of the swashplate in the propel pump determines the direction of rotation of the propel motor. The speed of the motor is determined by the volume of hydraulic oil that is supplied by the pump.
The propel motor consists of the following major components: shaft (1), cam ring (2), pistons (3), rollers (4), cylinder block (5), distributor (6), valve housing (7), displacement selector spool (8) , brake discs and brake plates (9), brake piston (10) and spring (11). The housing is fastened to the mounting plate. The mounting plate is fastened to the frame.
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| Illustration 2 | g00694195 |
(12) High pressure loop line (13) Brake line (14) High pressure loop line (15) Case drain line (16) Displacement selector pilot line | |
Five lines are connected to the rear propel motor: high pressure loop line (12), brake line (13), high pressure loop line (14), case drain line (15) and displacement selector pilot line (16) .
The propel motor uses radial pistons (3) and rollers (4) that work against cam ring (2) in order to generate torque at variable speeds. The propel motor has 10 pistons that are radially positioned in the internal cylinder block (5). The cam ring has eight lobes. The cam ring has the shape of a sine wave that is wrapped in a circle.
When pressure is applied to a piston, the roller moves down a slope on the cam ring and the cylinder block rotates. This transmits torque to the drive shaft and the wheel. When the roller is at the bottom of the slope on the cam ring, the piston and the cylinder block are blocked from the supply passages and the return passages. When the roller moves beyond the bottom of the slope on the cam ring, the piston is connected to the return side of the loop and the oil is forced out of the cylinder block. The roller moves up a slope on the cam ring. When the roller is at the top of the slope on the cam ring, the piston and the cylinder block are blocked from the supply passages and the return passages. When the piston passes the center of the lobe, the cycle begins again.
The oil that is supplied to the pistons is controlled by distributor (6). The distributor is located at the center of valve housing (7). The distributor works with displacement selector spool (8) in order to control the displacement of the motor. The distributor has multiple ports that supply oil to the pistons. The ports allow the reduced pressure oil to return to the propel pump. The return circuit is under charge pressure in order to keep the piston cavities full. This keeps the rollers against the cam surface.
The parking brake is spring applied and pressure released. Brake discs are splined to the shaft assembly and the brake plates are splined to the stationary housing. When the brake is applied, the passage for charge oil is blocked at the brake interlock valve. The brake piston cavity is open to the hydraulic oil tank. Spring (11) pushes on brake piston (10). This compresses the brake plates and the brake discs (9). At this point, shaft (1) is locked to the stationary housing and the wheel will not turn.
When the brake is released, the charge oil is routed to the passage for charge oil (13) by the brake interlock valve. The charge oil enters the brake piston cavity and the charge oil acts against brake piston (10). The charge oil pressure overcomes the force of the spring. This moves the brake piston away from brake plates and the brake discs (9). At this point, the wheel is free to turn.