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| Illustration 1 | g00466862 |
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Drum Propel Pump (1) Drive shaft. (2) Cup. (3) Servo valve. (4) Directional control valve. (5) Port Plate. (6) Inlet/Outlet port. (7) Head. (8) Inlet/Outlet port. (9) Case. (10) Barrel assembly. (11) Shims. (12) Spring washers. (13) Pistons. (14) Swashplate. (15) Bearing housing. | |
The drum propel pump is mounted in tandem with the axle propel pump. The charge pressure for the propel system is supplied by the steering pump. When the engine is operating, drive shaft (1) and barrel assembly (10) are rotating. There are nine pistons (13) in the barrel assembly. Port plate (5) and swashplate (14) are fastened to case (9). The port plate and the swashplate do not rotate. Spring washers (12) keep a force on the barrel assembly to make a high-pressure seal between the barrel assembly and the port plate. When the barrel assembly is rotating, each piston (13) follows the angle of the swashplate. If the swashplate angle is at zero, the pistons do not move in and out of the barrel assembly and there is no oil flow.
The position of the swashplate is controlled by the manual directional control valve (4) and servo valve (3). Movement of the propel control lever moves the directional control valve. The directional control valve routes charge oil into the servo valve. The servo valve controls the direction and the amount of the swashplate angle.
The steering pump maintains charge oil in the propel pump to keep the barrel assembly full of oil. The charge oil lubricates the pump components. The internal loss of oil due to leakage is replenished by the charge oil. The charge oil is also used to release the brakes and the charge oil will provide the shift valve with oil.
Oil flows from the drum propel pump to the drum propel motor and back to the drum propel pump by way of inlet/outlet ports (6) and (8). The position of the swashplate determines the direction of flow and the high-pressure side of the two loop lines.
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| Illustration 2 | g00485610 |
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The location of Servo Valves on the propel pumps. (1) Servo valves. | |
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| Illustration 3 | g00469156 |
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Servo Valve (2) Springs. (3) Slot for control valve. (4) Servo piston. (5) Slot for swashplate control. | |
Oil from the control valve goes to either the right or the left end of servo piston (4). Servo piston (4) also receives a mechanical input from the lever that is connected to slot (3).
The swashplate control is attached to the servo piston in slot (5). When the servo piston moves, the lever moves the swashplate to the angle that corresponds to the position of the servo piston.
When the charge pressure is relieved by the POR valve, springs (2) move servo piston (4) toward the centered position. This reduces the angle of the swashplate in the pump which causes the pump output to be reduced.
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| Illustration 4 | g00469121 |
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Pressure Override Relief Valve (1) Adjustment screw. (2) Locknut. (3) Spring. (4) Passage. (5) Valve. (6) Passage. (7) Piston. (8) Chamber. (9) Passage. (10) Slug. (11) Passage. | |
The pressure override relief (POR) valve is on the propel pump. The POR valve limits the maximum pressure on both sides of the propel loop. This valve prevents continuous dumping of excessive flow through the main relief valves in the pump. The POR valve is set at
Oil from the high-pressure side of the closed loop enters the POR valve at passage (9) or (11). This is depending on the side of the closed loop that has the higher pressure. Slug (10) moves up if the high pressure is in passage (11). The slug moves down if the high pressure is in passage (9). This sends the high-pressure oil to chamber (8).
When the pressure setting of the POR valve is reached, the pressure moves piston (7) and valve (5) against spring (3). This opens passage (4), and the charge oil goes through passage (6) to the tank. When the charge oil goes to the tank, the centering springs shift the servo valve and the angle of the swashplate is reduced.
Valve (5) serves two purposes. The valve modulates to maintain the system pressure at the setting of the POR valve until the load is reduced. The valve maintains the charge pressure so that the angle of the swashplate is large enough to compensate for system leakage. The pressure setting of the POR valve can be adjusted by loosening locknut (2) and adjusting screw (1).
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| Illustration 5 | g00476058 |
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Charge Relief Valve | |
Each propel pump has a charge relief valve. The charge relief valves are located in the pump housings. When the charge relief valve opens, excess oil is directed back to the hydraulic oil tank. The pressure settings for the charge relief valves are
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| Illustration 6 | g00467841 |
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Propel Pumps (1) Multifunction valves for the axle propel pump. (2) Multifunction valves for the drum propel pump. | |
The two sets of multifunction valves are designed to provide the following three functions:
- High-pressure relief valve
- Makeup check valve
- Bypass valve
The maximum working pressure of each loop line of the closed circuit is limited to
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| Illustration 7 | g00467843 |
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Multifunction Valve (1) Cap. (2) Stud. (3) Locknut. (4) Spring. (5) Collar. (6) Spring. (7) Spindle. (8) Passage. (9) Poppet. (10) Seat. (11) Seat. | |
The high-pressure relief valve functions to protect the circuit from high-pressure spikes. The valve also protects against damage to the circuit components if the POR valve malfunctions. Oil from the high-pressure side of the open circuit enters the valve at passages (8). Spring (6) forces spindle (7) against seat (11). The oil pressure acts against the force of spring (6). When the circuit pressure reaches the high-pressure relief setting, spindle (7) is lifted off seat (11). This movement instantly dumps high-pressure oil into the low-pressure side of the closed circuit.
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| Illustration 8 | g00468192 |
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Multifunction Valve (1) Cap. (2) Stud. (3) Locknut. (4) Spring. (5) Collar. (6) Spring. (7) Spindle. (8) Passage. (9) Poppet. (10) Seat. (11) Seat. | |
The multifunction valve has a second function. The valve acts as a makeup valve for the closed circuit. When the pressure in passages (8) (low-pressure side of the closed circuit) drops below the charge pressure, charge oil fills the closed circuit. Charge oil pressure on poppet (9) compresses spring (4). Poppet (9) is lifted off seat (10). Oil from the charge loop flows into the low-pressure side of the open circuit. When the pressure in the low-pressure side of the open circuit increases to charge pressure, the force of spring (6) closes poppet (9) on seat (10).
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| Illustration 9 | g00467876 |
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Multifunction Valve (1) Cap. (2) Stud. (3) Locknut. (4) Spring. (5) Collar. (6) Spring. (7) Spindle. (8) Passage. (9) Poppet. (10) Seat. (11) Seat. | |
The multifunction valve has a third function. The valve allows the machine to be towed. To tow the machine, loosen locknut (3) and turn stud (2) clockwise until the stud contacts with the top of collar (5). Spring (4) is compressed. Then turn stud (2) until the top of the stud is flush with locknut (3). Spindle (7) moves downward and the oil flows across seat (11). This action allows the oil to pass from one side of the closed circuit to the other side.
Note: Brakes must be released prior to towing.
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| Illustration 10 | g00451114 |
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Directional Control Valve (1) Lever. (2) Spool. (3) Passage for charge oil. (4) Control valve body. (5) Servo valve lever. | |
The propel control lever delivers a mechanical input to lever (1). The input determines the amount of rotation of spool (2). The output of the propel pump is proportional from 0 to 100 percent. This measurement is based on the amount of charge oil that is allowed to flow from passage (3) through spool (2) and into the servo valve. Charge oil flows through passage (3) to the spool (2) and the oil is sent to either the right end of the servo valve or left end of the servo valve. The charge oil pressure shifts the servo valve, and a mechanical signal is sent to the swashplate. This action upstrokes the propel pump.
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| Illustration 11 | g00485605 |
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Location of Neutral Start Switch-on Propel Pump (1) Neutral start switch. | |
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| Illustration 12 | g00468995 |
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Neutral Start Switch (2) Spool. (3) Electrical switch. (4) Neutral start switch pin. | |
When the control valve spool (2) is centered properly, neutral start switch pin (4) will rest between the spool and electrical switch (3). The electrical contact for the starter relay will not be broken. If spool (2) is shifted from neutral, pin (4) will be pushed outward. This action will cause the contact inside electrical switch (3) to open. When this happens the electrical continuity of the start circuit will be broken and the machine will be prevented from starting.
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| Illustration 13 | g00468477 |
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Propel Pumps (1) Brake interlock valves. | |
Brake interlock valve (1) prevents the pump swashplate from moving out of neutral when the parking brake is applied. Both the drums propel pump and the axle propel pump have a brake interlock valve.
The brake interlock valve has a solenoid on one end to move the valve spool. There is a spring on the other end to position the valve spool when the solenoid is not energized.
When the brake interlock valve is in the BRAKE ON position, the brake interlock solenoid is not energized. In this position, the brake interlock valve shifts and the brake lines and the directional control valve are open to the hydraulic oil tank. When the brake lines are open to the hydraulic tank, the spring applied brakes are engaged. When the directional control valve is open to the hydraulic tank, the servo valve shifts to the neutral position. This causes the swashplate to move to the neutral position.
When the brake interlock valve is in the BRAKE OFF position, the brake interlock solenoid is energized. In this position, the brake interlock valve shifts and the charge oil flows across the valve and to the brake lines and the directional control valve. The charge oil pressure overcomes the force of the springs and the brakes are released. When the charge oil becomes available for the directional control valve, any movement of the propel control lever causes the servo valve to shift the swashplate.
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| Illustration 14 | g00485518 |
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Brake Interlock Valve (2) Solenoid valve. (3) Charge pressure port. (4) Brake port. (5) Tank port. | |
When solenoid valve (2) is not energized, brake port (4) is common to tank port (5). The charge pressure port (3) is blocked. This prevents the charge pressure from releasing the brakes.
When solenoid valve (2) is energized, the spool that is inside the valve moves. This allows charge oil into the circuit and the brakes release.