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| Illustration 1 | g06618122 |
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Front Propel Motor (1) Speed sensor (2) Port "X" (shift port) (3) Port "A" (supply port) (4) Port "Z" (brake port) (5) Port "B" (supply port) (6) Case drain line (port "L") (7) Front propulsion motor group (8) Manual brake release plug | |
The machine is equipped with two propel motor groups, one for each drum. Front propulsion motor group (7) is on the right side of the front drum. The rear propel motor group (not shown) is on the left side of the rear drum. Each motor group contains a radial-piston motor with two speeds and a multi-disk parking brake.
Each port in the motor housing is identified by a letter. The function of each port is as follows:
- Port "A" (3) is the forward supply port on front propel motor group (7) and the reverse supply port on the rear propel motor group.
- Port "B" (5) is the reverse supply port on front propel motor group (7) and the forward supply port on the rear propel motor group.
- Port "L"is the case drain port. Case drain line (6) is connected to this port. Case drain oil from front propulsion motor group (7) and from the rear propel motor group is sent to port "C" of the bypass manifold.
- Port "X" (2) is the shift port. When the shift valve is energized, charge oil is directed to port "X" of front propel motor group (7). In this case, the motor shifts to high-speed mode. Port "X" of the rear propel motor group is connected to the hydraulic tank. The rear propel motor group operates in low speed, regardless of the selected propel mode.
- Port "Z" (4) is the brake port. When the interlock solenoid on the propel pump is energized, charge oil is directed from the pump into port "Z". This action releases the parking brakes. When the interlock solenoid is not energized, port "Z" is connected to the propel pump case drain. In this case, springs inside the parking brakes engage the brakes.
Note: The housing of the multi-disk parking brake has manual brake release plug (8). If the brakes must be released manually, the plug must be removed. Then, an M20 screw with a minimum length of
Each propel motor group is equipped with dual-signal speed sensor (1). A speed ring on the output shaft of the motor rotates past the tip of the speed sensor. Each time a tooth passes the sensor, two electrical impulses are sent to the transmission ECM. These impulses are out of phase with one another. The transmission ECM converts the frequency of the impulses to a vehicle speed and the phase of the impulses into a travel direction.
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| Illustration 2 | g06618564 |
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Cross Section, Propel Motor Cylinder Block (A) Low-speed operation (full displacement) (B) High-speed operation (half displacement) (9) Output shaft (10) Cam ring (11) Cylinder block (12) Cam follower (13) Piston (14) Distribution channel "3" (15) Distribution channel "2" (16) Distribution channel "1" | |
Cam ring (10) and control valve (not shown) in the radial-piston motor are stationary. Cylinder block (11) and pistons (13) rotate with output shaft (9). During motor operation, each piston in the motor goes through a four-phase cycle. The phases in the cycle correspond with the position of the cam follower in relation to the lobes of the cam ring.
When cam follower (12) is at the highest point on the cam lobe (relative to the center of the motor), piston (13) is in the top-neutral phase. At this point, the piston chamber is not connected to either an inlet or an outlet port. When the cam follower is on the downhill face of the cam lobe, the piston is in the full-power phase. During this phase, the piston chamber is connected to an inlet port. When the piston is connected to an inlet port, pump supply oil fills the piston chamber. The supply oil forces the piston out of the barrel. This action forces the cam follower to move down the cam lobe.
The piston chamber remains connected to the inlet port until the cam follower reaches the lowest point in the valley of the cam ring. At this point, the piston is in the bottom-neutral phase. In this phase, the piston chamber is not connected to an inlet or an outlet port. When the cam follower is on the uphill face of the cam lobe, the piston chamber is open to the return line. At this point, the piston is in the discharge phase. During the discharge phase, the piston moves toward the center of the motor. As the piston retracts into the cylinder block, the oil in the piston chamber flows into the outlet port.
When the motor is operating in low-speed mode, distribution channel "1" (16) and distribution channel "2" (15) receive high-pressure oil. These distribution channels deliver oil to four pistons at a time for low speed and high torque operation. When the motor is operating in high-speed mode, a control spool is shifted. This shift diverts high-pressure oil from distribution channel "2" to the return pressure of distribution channel "3" (14). This action reduces by half the number of pistons in the working stroke that operate at high pressure. Under these conditions, the motor will run at twice the speed but with half the torque.
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| Illustration 3 | g06618621 |
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Cross Section, Brake Assembly (A) Parking brake applied (B) Parking brake released (17) Brake shaft (18) Disc package (19) Annular cavity (20) Belleville washer (21) Brake piston | |
The brake assembly is mounted on the end of the propel motor. Brake shaft (17) is directly connected to the rotating group of the propel motor.
Disc package (18) is made of alternating discs splined to brake shaft (17) and to the brake housing. When the brake is applied, the disc package is compressed by the force of Belleville washer (20) acting through brake piston (21). In this case, the friction between the discs generates a holding torque that prevents rotation of the brake shaft.
When hydraulic oil is directed into annular cavity (19), hydraulic pressure acts against brake piston (21) to oppose the spring force of Belleville washer (20). If sufficient pressure is applied, the brake piston moves and compresses the Belleville washer. This action removes the compression on disc package (18) and allows brake shaft (17) to rotate freely.