Systems Operation

Usage:

Introduction

Reference: For Specifications with illustrations, refer to the Specifications for the CP-533 & CS-533 Propulsion System, Form No.KENR1893. If the Specifications in Form No.KENR1893 are not the same as listed in the Systems Operation and the Testing And Adjusting, look at the print date on the front cover of each book. Use the Specifications listed in the book with the latest date.

Propulsion System Schematic
(1) Front propulsion pump. (2) Rear propulsion pump. (3) Parking brake valve. (4) Speed shift control valve. (5) Front propulsion motor. (6) Propulsion system cooling valve. (7) Oil cooler. (8) Hydraulic oil tank. (9) Rear propulsion motor.

The propulsion system is a closed loop, hydrostatic system. The main components of the system are: front propulsion pump (1), rear propulsion pump (2), parking brake valve (3), speed shift control valve (4), front propulsion motor (5), propulsion system cooling valve (6), oil cooler (7), hydraulic oil tank (8) and rear propulsion motor (9).

Charge oil (make-up oil) for the propulsion pumps comes from the hydraulic oil filter and is supplied by the return oil from the steering system. The flow from the propulsion pumps is controlled by the propulsion control lever on the operator console. A control cable connects the propulsion control lever to the rear pump.

A linkage rod connects the rear pump to the front pump. Propulsion system cooling valve (6) allows some of the oil in the propulsion system to go to the vibration cooling valve, then to oil cooler (7) and hydraulic oil tank (8). Speed shift control valve (4) sends charge oil to front and rear propulsion motors (5) and (9) to change the motor displacement for high and low speeds. Parking brake valve (3) controls the flow of charge oil to the parking brake in the front propulsion motor.

Below Operator Platform
(1) Front propulsion pump. (2) Rear propulsion pump. (6) Propulsion system cooling valve.

Front propulsion pump (1), rear propulsion pump (2) and propulsion system cooling valve (6) are located under the operator's platform. The front propulsion pump and rear propulsion pump are piston pumps. The propulsion system cooling valve is a three position spring centered shuttle valve. The propulsion system cooling valve has four disconnect pressure taps for measuring the close loop hydraulic pressure for the two propel circuits.

Behind Operator Platform
(3) Parking brake valve. (4) Speed shift control valve.

Parking brake valve (3) is a solenoid operated, two position valve that controls the operation of the brake in the front propulsion motor and the rear axle.

Speed shift control valve (4) is a solenoid operated, two position valve that controls the operation of the speed shift mechanism in the front and rear propulsion motors.

Left Side Of Drum
(5) Front propulsion motor.

Front propulsion motor (5) is a dual displacement radial piston motor, which provides high starting torque and variable operating speeds.

Rear Axle
(9) Rear propulsion motor.

Rear propulsion motor (9) is a dual displacement axial piston motor that features the bent axis design rotary group.

Propulsion Pumps

Propulsion Pump
(1) Inlet/Outlet port. (2) Port plate. (3) Barrel assembly. (4) Servo piston. (5) Piston. (6) Servo control valve. (7) Shaft. (8) Inlet/Outlet port. (9) Spring. (10) Swashplate. (11) Housing.

When the engine is running, shaft (7) and barrel assembly (3) are rotating. There are nine pistons (5) in the barrel assembly. Port plate (2) and swashplate (10) are fastened to or held by housing (11) and do not rotate. Spring (9) keeps 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 (5) 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. Charge oil from the steering system maintains oil pressure in the propulsion pump to keep the barrel assembly full of oil. Lubricate the pump components and to make up for the normal, internal loss of oil due to leakage. The charge oil is also used to fill the closed loop system with oil. This pressure provides the service braking for the system.

The position of the swashplate is controlled by servo control valve (6) and servo piston (4). Movement of the propulsion control lever will move the servo control valve. The servo control valve routes charge oil to activate and adjust the servo piston. The servo piston controls the direction and amount of swashplate angle.

Oil flows from the propulsion pump to the propulsion motor and back to the propulsion pump through inlet/outlet ports (1) and (8). The position of the swashplate determines the direction of flow and which of the two loop lines is the high pressure line.

Charge Relief And Multi-function Valve

Propulsion Pumps
(12) Charge relief valve. (13) Multi-function valve. (14) Multi-function valve. (15) Charge relief valve. (16) Neutral start switch.

Front Propulsion pump
(12) Charge relief valve. (13) Multi-function valve. (17) Charge circuit oil line.

Charge Relief Valve

Each propulsion pump has a charge relief valve. Charge oil enters the pump through charge circuit oil line (17). Charge relief valves (12) and (15) are located in the pump housings. When the charge relief valve opens, excess oil is directed back to the hydraulic oil tank. The charge relief valve is adjustable to maintain a maximum pressure of 2756 ± 140 kPa (400 ± 20 psi). This is a differential pressure of the charge pressure measured after the hydraulic oil filter and the case drain pressure measured at the propulsion pumps.

Multi-Function Valves

Multi-Function Valves
(18) Pressure limiter section. (19) Main relief valve section. (20) Charge check valve section. (21) Adjustment screw with locknut. (22) Bypass actuator nut. (23) Pressure limiter valve poppet.

Each propulsion pump has two multi-function valves, one for FORWARD drive and one for REVERSE drive.

Each multi-function valve performs four functions in the circuit. Those four functions are: charge system check valve, high pressure relief valve, system pressure limiter and system loop bypass.

System pressure is maintained at approximately 2350 kPa (340 psi) below the main relief valve setting by pressure limiter section (18) of the multi-function valve. When system pressure reaches the pressure limiter setting, the pressure limiter routes oil to the servo valve causing the propulsion pump to destroke. The destroking of the pump reduces pump output pressure. System pressure adjustments are made with adjustment screw (21).

Pressure limiter valve poppet (23) also acts as a pilot valve for the main relief valve. Main relief valve section (19) protects the high pressure system from sudden high pressure spikes, such as obstruction to the drum or wheels. Using the pressure limiter valve poppet as a pilot allows the main relief valve pressure to be higher than the limiter pressure.

Charge check valve section (20) protects the charge circuit from damage by stopping oil flow from the high pressure side of the closed loop to the charge circuit. The check valve is spring loaded and seats against the high pressure inlet area of the multi-function valve. The center of the charge check valve is open and seats on the outer diameter of the high pressure valve spool. The high pressure valve spool is also open through the center.

The area between the charge check valve and the charge check valve seat is open to the charge oil circuit. As leakage occurs in the closed loop circuit, charge oil enters the multi-function valve and overcomes the spring tension and the pressure of the low side of the closed loop, forcing the charge check valve off the seat. When the check valve is off the seat, charge oil flows into the low pressure side of the closed loop.

High pressure oil from the propulsion pump enters through the openings and acts on both the inlet end of the high pressure valve spool and the opposite end of the charge check valve. As loop pressure increases, charge oil pressure is overcome causing the charge check valve to shift and reseat, stopping the flow between the loop and the charge circuit.

Bypass actuator nut (22) is used when conditions require flow but no pressure in the propulsion system such as towing the machine. Loosening the bypass actuator nut three turns, this removes the tension of the pressure limiter valve spring. When the bypass valve is open the propulsion system cannot build up pressure and the machine can be moved.

Adjustment screw (21) is part of the bypass actuator nut. When the bypass actuator nut is moved, the adjustment screw moves the same number of turns and therefore the main relief valve setting does not change. After the machine has been towed, tighten the bypass actuator nut three turns and torque to proper specification. No adjustment is needed to the main relief valve setting.

Servo Valve

Servo Valve
(6) Servo valve. (24) Metering spool. (25) Control linkage.

Movement of the propulsion control lever moves control linkage (25). Movement of the control linkage causes metering spool (24) to move. When the metering spool moves, charge oil is directed to one side of the servo piston and oil from the other side is directed to drain. The servo piston moves and causes swashplate (10) to rotate and change the pump output. A feedback link that is connected to the swashplate controls the amount of movement of the servo valve.

Neutralizer Valve

Front Propulsion Pump
(26) Neutralizer valve.

Neutralizer valve (26) prevents the pump swashplate from moving out of neutral when the parking brake is applied. Both front and rear propulsion pumps have a neutralizer valve.

The neutralizer valve has a solenoid on one end to move the valve spool and a spring on the other end to position the valve spool when the solenoid is not energized. The neutralizer valve solenoid is energized when the parking brake button is in the BRAKE OFF position.

When the neutralizer valve is not energized (parking brake is on) the valve spool connects both sides of the servo piston. The oil from the servo piston is open to case drain and goes back through the manual displacement control valve. When the neutralizer valve is energized (parking brake is off) the valve spool blocks the passage between the ends of the servo piston. Charge oil can now be directed by the servo valve to one end of the servo piston to move the swashplate from neutral.

Propel Brake Interlock

Propel Brake Interlock Electrical Schematic
(1) Start relay. (2) Main relay. (3) Parking brake fuse. (4) Wire to starter. (5) Neutral start relay #2 (NSR2). (6) Neutral start relay #1 (NSR1). (7) Brake relay #1 (BR1). (8) Brake relay #2 (BR2). (9) Parking brake switch. (10) Wire to diode and alternator indicator lamp. (11) Parking brake solenoid. (12) Wire to engine shutdown solenoid. (13) Wire to key start fuse. (14) Front propel pump neutralizer valve. (15) Rear propel pump neutralizer valve. (16) Neutral start switch. (17) Key start switch.

The propel brake interlock performs two functions. It prevents the operator from propelling the machine while the parking brake is applied and it also provides for controlled propelling when the parking button is released.

The main components of the propel brake interlock are: parking brake fuse (3), neutral start relay #2 (NSR2) (5), neutral start relay #1 (NSR1) (6), brake relay #1 (BR1) (7), brake relay #2 (BR2) (8), parking brake switch (9), parking brake solenoid (11), front propel pump neutralizer valve (14), rear propel pump neutralizer valve (15) and neutral start switch (16).

Parking brake solenoid (11), front propel pump neutralizer valve (14) and rear propel pump neutralizer valve (15) receive electrical power from brake relay #2 (BR2) (8). This allows parking brake solenoid (11) to move the two-position brake valve, sending non-filtered charge pressure oil to the parking brake in the front propel motor. In order for this to be accomplished, the following three conditions must be met:

*First, key start switch (17) must be in the ON position. This provides electrical power to parking brake switch (9) from main relay (2) and parking brake fuse (3).

*Second, the propel control lever must be in the neutral position. With the propel control lever in this position, neutral start relay #2 NSR2 (5) is energized, breaking continuity from neutral start relay #2 (NSR2) (5) to brake relay #2 (BR2) (8).

*Third, parking brake switch (9) must be released. When this is done and with the propel control lever in the neutral position, electrical power to the brake relay #1 (BR1) (7) and brake relay #2 (BR2) (8) is interrupted and electrical power is supplied to parking brake solenoid (11), front propel pump neutralizer valve (14) and rear propel pump neutralizer valve (15). This in turn allows both propel pumps to go on stroke when the propel control lever is moved forward or reverse and allows unfiltered charge pressure oil to flow to the parking brake in the front propel motor. The charge pressure works against the applied spring pressure, releasing the parking brake.

If an operator would try to release the parking brake with the propel control lever in the forward or reverse position, the machine would not move. With the propel control lever not in the neutral position, neutral start relay #2 (NSR2) (5) is not energized. Electrical power is sent from neutral start relay #2 (NSR2) (5) to brake relay #2 (BR2) (8). Due to the electrical logic of brake relay #2 (BR2) (8), this would continue to supply the coils of brake relay #1 (BR1) (7) and brake relay #2 (BR2) (8) with electrical power even if parking brake switch (9) is released. This prevents electrical power from being supplied to parking brake solenoid (11), front propel pump neutralizer valve (14) and rear propel pump neutralizer valve (15). This provides a latching mechanism and prevents an operator from propelling the machine until the propel control lever is brought back to the neutral position. With the propel control lever in the neutral position, the latching mechanism is eliminated and the operator is allowed to operate and propel the machine.

Propulsion System Cooling Valve

Propulsion System Cooling Valve
(1) Propulsion system cooling valve.

Propulsion system cooling valve (1) is connected to the high pressure side and the low pressure side of the closed loop circuit. The propulsion system cooling valve allows the flow of hot oil from the low pressure loop to the vibration cooling valve. Oil from the vibration cooling valve goes to the oil cooler. This allows cooled charge oil to enter the low pressure loop through the check valve of the multi-function valve.

Propulsion System Cooling Valve Schematic
(1) Propulsion system cooling valve. (2) Spring. (3) Closed circuit loop line. (4) Closed circuit loop line. (5) Vibration cooling valve return line. (6) Spring.

With the propulsion system circuit in the neutral position, springs (2) and (6) center the shuttle valve spool inside propulsion system cooling valve (1) so that oil flow from closed circuit loop lines (3) and (4) is blocked from vibration cooling valve return line (5).

With the propulsion system circuit in the forward drive position, high pressure oil in closed circuit loop line (3) moves the shuttle valve inside the propulsion system cooling valve against spring (6). Hot low pressure oil in closed circuit loop line (4) now flows across the shuttle valve spool into the vibration cooling valve return line. This allows cooled, filtered charge oil to enter the low pressure loop through the charge check valve.

With the propulsion system circuit in the reverse drive position, high pressure oil in closed circuit loop line (4) moves the shuttle valve inside the propulsion system cooling valve against spring (2). Hot low pressure oil in closed circuit loop line (3) now flows across the shuttle valve spool into the vibration cooling valve return line. This allows cooled, filtered charge oil to enter the low pressure loop through the charge check valve.

Parking Brake And Speed Shift Control Valve

Parking Brake And Speed Shift Control Valve
(1) Check valve. (2) Speed shift solenoid. (3) Return oil hose to return manifold. (4) Charge oil pressure test port. (5) Shift hose to rear drive motor. (6) Shift hose to front drive motor. (7) Shift hose to front propulsion motor. (8) Parking brake solenoid. (9) Charge oil hose from steering pump. (10) Hose to hydraulic oil filter. (11) Hose to parking brake in front propulsion motor.

Schematic For Parking Brake And Speed Shift Control Valve
(12) Parking brake valve. (13) Speed shift control valve.

Operator Console
(14) Speed selection switch. (15) Parking brake switch.

Parking Brake Valve

Parking brake valve (12) is a solenoid operated, two position valve that controls the operation of the brake in the front propulsion motor.

When parking brake switch (15) is pushed in (parking brake applied), parking brake solenoid (8) is not energized. The parking brake valve in this position connects hose (11) of the parking brake in the front propulsion motor to return oil hose (3) to the return manifold. This allows the oil from the brake release piston to drain to the hydraulic oil tank and the brake springs will apply the parking brake.

When parking brake switch (15) is pulled out (parking brake released), parking brake solenoid (8) is energized. The parking brake valve in this position, charge oil flows from hose (9) to the parking brake in the front propulsion motor through hose (11). This allows unfiltered charge oil from return side of the steering control valve to go to the piston of the brake and will release the parking brake.

Speed Shift Control Valve

Speed shift control valve (13) is a solenoid operated, two position valve that controls the operation of the speed shift mechanism in the front and rear propulsion motors.

When speed selection switch (14) is in the LOW speed position, speed shift solenoid (2) is not energized. The speed shift control valve in this position connects hoses (5) and (6) to hose (3). This allows oil from the shift valves in the propulsion motors to go to the return manifold. The propulsion motors are now in the maximum displacement position (LOW speed).

When the speed selection switch is in the HIGH speed position, speed shift solenoid (2) is energized. The speed shift control valve in this position connects hoses (5) and (6) to hose (9). This allows unfiltered charge oil from the steering pump to go to the shift valves in the front and rear propulsion motors. The propulsion motors are now in the minimum displacement position (HIGH speed).

Front Propulsion Motor

Front Propulsion Motor
(1) Drum drive shaft. (2) Internal cylinder block. (3) Radial piston. (4) Roller. (5) Cam ring. (6) Valve housing. (7) Valve. (8) Displacement selector spool. (9) Brake plates and discs. (10) Brake piston. (11) Springs. (12) Brake shaft. (13) Passage. (14) Passage. (15) Passage.

Hydraulic oil is supplied to the front propulsion motor by the front propulsion pump on the pump group. The direction of motor rotation is controlled by the oil flow direction from the front propulsion pump. The displacement and speed is controlled by the speed shift control valve.

The propulsion motor is a two speed (dual displacement) radial piston motor with a parking brake. In LOW speed, (high torque, large displacement) the motor has a displacement of 4202 cc/rev (256.2 cu in/rev). In HIGH speed, (low torque, small displacement) the motor has a displacement of 2101 cc/rev (128.1 cu in/rev). When the machine is shifted from LOW to HIGH, the drive motor displacement and torque are decreased by one half, and the rotating speed is doubled. The propulsion motor can operate in either direction.

There are six lines connected to the propulsion motor: two high pressure loop lines (17) and (20), brake line (18), a displacement selector pilot line (19) and two case drain lines (16) and (21).

The major components of the propulsion motor are drum drive shaft (1); motor group consisting of internal cylinder block (2), radial pistons (3) with rollers (4) and cam ring (5); valve housing (6); valve (7); displacement selector spool (8); and a parking brake group consisting of plates and discs (9), brake piston (10) and springs (11). Valve housing (6) is fastened to the yoke on the left side of the drum.

Front Propulsion Motor
(16) Case drain line. (17) High pressure loop line. (18) Brake line. (19) Displacement selector pilot line. (20) High pressure loop line. (21) Case drain line.

The front propulsion motor uses radial pistons (3) with rollers (4) working against cam ring (5) to generate high torque at low speeds. The motor displacement is controlled by charge oil acting against spring loaded displacement selector spool (8) in valve housing (6) of the front propulsion motor.

The torque is generated by the radial pistons of the front propulsion motor. Each radial piston has a roller. The front propulsion motor has 20 pistons (3) radially positioned in two rows in internal cylinder block (2). Cam ring (5) that the pistons act upon is part of the motor housing. The cam ring has eight lobes. The cam is shaped like a sine wave wrapped in a circle. High pressure oil from the propel pumps works against the pistons when they are on the downward slope. With cam ring fixed this transmits torque to the cylinder block causing it to rotate. When the roller is at the bottom of the slope the piston and cylinder are blocked from the supply and return passages. When the roller moves beyond the bottom of the slope, the piston is connected to the return side of the loop and the oil is forced out of the cylinder as the roller moves up a slope on the cam. When the roller is at the top of the slope, the piston and cylinder are blocked from the supply and return passages until it passes over center and the cycle begins again.

When the front propulsion motor is operating at LOW speed (large displacement), eight pistons are pressurized and eight are connected to return passages. When the front propulsion motor is operating at HIGH speed (small displacement), four pistons are pressurized and 12 are connected to return passages.

Leakage oil from the cylinder block fills the motor housing for lubrication and cooling.

Schematic Of Valve (7)
(13) Passage. (14) Passage. (15) Passage.

All of the porting to the pistons is controlled by valve (7) that is located at the center of valve housing (6). This valve pressurizes the pistons at the right time and works with displacement selector spool (8) to control the displacement of the motor. Valve (7) has 16 ports that supply oil to the pistons and allow reduced pressure oil to return to the pump. The return circuit is under a slight pressure (charge pressure) to keep the piston cavities full and the rollers against the cam surface. Passage (13) connects to eight ports. Passages (14) and (15) connect to four ports each. The forward direction side of the high pressure loop is connected to passage (15). The reverse direction side of the high pressure loop is connected to passage (13).

When the front propulsion motor is in FORWARD LOW, pressure oil is supplied to the front propulsion motor through passage (15) in valve housing (6) and reduced pressure oil returns to the propulsion pump through passage (13). Displacement selector spool (8) does not receive pilot pressure in LOW speed (large displacement). The pressure oil in passage (15) flows around displacement selector spool (8) into passage (14). Since both passage (14) and passage (15) are connected to four ports each, eight ports are supplied with pressure oil. Internal cylinder block (2) has 20 equally spaced openings. Because of the design of the internal cylinder block and the valve, there are always four cylinders that are in neutral (blocked oil). There are eight cylinders connected to high pressure oil and eight cylinders connected to low pressure oil that returns to the propulsion pump.

When the front propulsion motor is in FORWARD HIGH, pressure oil is supplied to the front propulsion motor through passage (15) in valve housing (6) and reduced pressure oil returns to the propulsion pump through passage (13). Displacement selector spool (8) is piloted in HIGH speed (small displacement) and the spool shifts to the left. The reduced pressure oil in passage (14) flows around the spool and combine with passage (13). Since only passage (15) has pressure oil, four ports in valve (7) are supplied with pressure oil. Internal cylinder block (2) has 20 equally spaced openings. Because of the design of the internal cylinder block and the valve, there are always four cylinders that are in neutral (blocked oil). There are four cylinders connected to high pressure oil and 12 cylinders connected to low pressure oil that returns to the pump.

When the front propulsion motor is in REVERSE LOW, pressure oil is supplied to the front propulsion motor through passage (13) in valve housing (6) and reduced pressure oil returns to the propulsion pump through passage (15). Displacement selector spool (8) does not pilot pressure in LOW speed (large displacement). The reduced pressure oil in passage (14) flows around the spool to combine with passage (15). With pressure oil in passage (13), eight ports in valve (7) are supplied with pressure oil. Internal cylinder block (2) has 20 equally spaced openings. Because of the design of the internal cylinder block and the valve, there are always four cylinders that are in neutral (blocked oil). There are eight cylinders connected to high pressure oil and eight cylinders connected to low pressure oil that returns to the propulsion pump.

When the front propulsion motor is in REVERSE HIGH, pressure oil is supplied to the front propulsion motor through passage (13) in valve housing (6) and reduced pressure oil returns to the propulsion pump through passage (15). Displacement selector spool (8) is piloted in HIGH speed (small displacement) and the spool shifts to the left. The pressure oil in passage (13) flows around the spool to combine with passage (14). With pressure oil in passage (13) and (14), 12 ports in valve (7) are supplied with pressure oil. Internal cylinder block (2) has 20 equally spaced openings. Because of the design of the internal cylinder block and the valve, there are always four cylinders that are in neutral (blocked oil). There are 12 cylinders connected to high pressure oil and four cylinders connected to low pressure oil that returns to the propulsion pump. Note: Four of the twelve pressurized pistons are trying to make the front propulsion motor go in the opposite direction. These pistons oppose the force of four of the remaining eight pistons, therefore only four pistons are actually supplying a driving force in REVERSE HIGH.

NOTE: Due to the design of this motor the forward direction is referred to as the preferential direction due to the 12 ports receiving high pressure oil in REVERSE HIGH. The motor efficiency is not as good in REVERSE HIGH.

Pistons And Cam

Motor Startup Phase
(2) Internal cylinder block. (3) Radial piston. (4) Roller. (5) Cam ring. (7) Valve. (A) Return oil. (B) Supply oil.

Pressure oil enters valve (7) through a passage which sends the oil to internal cylinder block (2). Oil from valve (7) passes into the cavity of radial piston (3). The radial piston pushes roller (4) against cam ring (5). This is the startup phase of the front propulsion motor. Springs help to seat the valve against the face of the internal cylinder block until the machine is running. The pressure oil acting on the tee pee design of the valve keeps the two faces seated.

Full Force Phase
(2) Internal cylinder block. (3) Radial piston. (4) Roller. (5) Cam ring. (7) Valve. (A) Return oil. (B) Supply oil.

The pressure which acts on radial piston (3) causes roller (4) to roll on the face of cam ring (5). This will drive internal cylinder block (2) in the direction shown by the arrow. Valve (7) remains stationary along with the motor casing. This means that the supply passage moves from a partial connection with the radial piston to a full one. This is the full force phase.

Bottom Neutral Phase
(2) Internal cylinder block. (3) Radial piston. (3A) Radial piston. (4) Roller. (5) Cam ring. (7) Valve. (A) Return oil. (B) Supply oil.

When roller (4) goes to the bottom of cam ring (5), the inlet port of radial piston (3) will be located between the valve passages. Since there is no connection with the passages, the piston does not drive on the face of the cam.

Radial piston (3A) takes over the role as the driving piston. This allows the roller of radial piston (3) to move up the cam ring face. The internal cylinder block and motor shaft will continue turning. This is the bottom neutral phase.

Discharge Phase
(2) Internal cylinder block. (3) Radial piston. (3A) Radial piston. (4) Roller. (5) Cam ring. (7) Valve. (A) Return oil. (B) Supply oil.

When the roller of radial piston (3) moves up the cam ring face, the piston cavity is connected to the return line passage of valve (7). This is the discharge phase.

Startup And Bottom Neutral Phase
(2) Internal cylinder block. (3) Radial piston. (3A) Radial piston. (4) Roller. (5) Cam ring. (7) Valve. (A) Return oil. (B) Supply oil.

As roller (4) of radial piston (3) continues moving up the cam face, the connection between the piston cavity and valve (7) return passage gradually closes. Radial piston (3A) is now at the bottom neutral phase.

Top Neutral Phase
(2) Internal cylinder block. (3) Radial piston. (3A) Radial piston. (4) Roller. (5) Cam ring. (7) Valve. (A) Return oil. (B) Supply oil.

When roller (4) of radial piston (3) is at the top of cam ring (5), the port of the piston will be located between two distributor passages. Since there is no connection between the two ports, radial piston (3) is neutralized. This position is the top neutral phase.

As soon as the roller passes the top of the cam and starts to move down the opposite face, the piston cavity will be connected with a new pressure oil passage in valve (7). This will give a new motor startup phase, and a new cycle will start for the piston.

Parking Brake

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 housing. When the brake is applied, the charge oil is blocked at the brake valve and the brake piston cavity is open to the hydraulic tank. Springs (11) push on piston (10) and compress brake discs and plates (9) together.

Rear Propulsion Motor

Rear Propulsion Motor
(1) Drive shaft. (2) Motor case. (3) Retainer. (4) Pistons. (5) Spring. (6) Barrel. (7) Minimum displacement adjustment screw. (8) Head. (9) Spring. (10) Stroke begin adjustment screw. (11) Poppet. (12) Cavity for pilot oil. (13) Valve spool. (14) Passage. (15) Spring. (16) Passage. (17) Piston. (18) Check valve. (19) Check valve. (20) Pivot pin. (21) Control lens. (22) Control slot. (23) Control slot. (24) Swivel pin. (25) Control piston. (26) Spring. (27) High pressure loop port. (28) High pressure loop port.

The rear propulsion motor is a variable displacement, bent-axis piston motor. In LOW speed, (high torque, large displacement) the motor has a displacement of 55 cc/rev (3.34 cu in/rev). In HIGH speed, (low torque, small displacement) the motor has a displacement of 28 cc/rev (1.71 cu in/rev). When the machine is shifted from LOW to HIGH, the rear propulsion motor displacement and torque are decreased by one half, and the rotating speed is doubled. The rear propulsion motor can operate in either direction.

There are five lines connected to the motor: two high pressure loop lines, a displacement selector pilot line and two case drain lines.

Oil is supplied to the rear propulsion motor by the rear propulsion pump on the pump group. The direction of the motor rotation is controlled by the oil flow direction from the propulsion pump. The displacement and speed are controlled by the speed shift control valve.

The components of the rear propulsion motor that rotate are drive shaft (1), retainer (3), pistons (4) and barrel (6). The components that do not rotate are motor case (2), head (8) and control lens (21). Spring (5) pushes barrel (6) against control lens (21) to make a high pressure seal between the barrel and control lens and between the control lens and the head.

When high pressure oil is at high pressure loop port (27), oil from the port also flows to control slot (23). Oil in the control slot goes into the cylinders of barrel (6) that are over the control slot.

The spherical piston heads are held in the sockets in drive shaft (1) by retainer (3). Seven pistons (4) are held by barrel (6). The barrel rotates around pivot pin (20) which is at an angle to the axis of drive shaft (1). Because of this bent-axis arrangement between the barrel and the shaft, the seven pistons move in and out of their cylinders as pressure oil enters and leaves the cylinders. This forces the pistons, barrel and drive shaft to rotate.

As the pistons, barrel and drive shaft continue to rotate, the piston reaches top center (fully retracted position). At the same time, the cylinder begins to overlap control slot (22) on the low pressure side of the loop. At this point the piston starts to move down. This pushes oil out of the cylinder, through the control slot, and through high pressure loop port (28) to the low pressure side of the loop.

The rear propulsion motor is lubricated by oil leakage from the pistons and barrel.

This rear propulsion motor operates either at large displacement (low speed) or at small displacement (high speed). At large displacement, the barrel and shaft are at the maximum angle. At small displacement, the barrel and control lens are at the minimum angle against minimum displacement adjustment screw (7).

Check valves (18) and (19) allow high pressure oil from high pressure loop ports (27) and (28) into passage (14) at all times.

With the rear propulsion motor in LOW speed, there is no control pressure at cavity for pilot oil (12). Spring (9) pushes piston (17) against stroke begin adjustment screw (10). Springs (15) and (26) push poppet (11) against valve spool (13). With the valve spool in this position, high pressure oil remains only in passage (14). The high pressure oil in passage (14) goes to the outside of the top side of control piston (25). The force from springs (9) and (26), and the force of the oil keep the control piston at the bottom. Swivel pin (24) is fastened to control piston (25) and fits in the center of control lens (21). The control lens and barrel are held at the maximum displacement angle.

When HIGH speed has been selected, the speed shift control valve allows charge oil to go to cavity for pilot oil (12) in the rear propulsion motor. This pressure pushes on the top of valve spool (13) with enough force to move the valve against the force of springs (15) and (26). When valve spool (13) moves down, high pressure oil from passage (14) can go to passage (16).

High pressure oil is now at the bottom of control piston (25) and around the outside of the top side of the piston. The area that the oil pushes against is larger on the bottom of the valve than the top. The control piston will move up and move control lens (21) and barrel (6) up to minimum displacement adjustment screw (7). The rear propulsion motor is now at minimum displacement (high speed).

Stroke begin adjustment screw (10) moves piston (17) which changes the pressure needed to allow valve spool (13) to move. This changes the amount of charge pressure needed to begin to move control piston (25) toward minimum angle.

Propulsion System Operation

Neutral With Parking Brake On

Propulsion System Schematic
(1) Front propulsion pump. (2) Pump control valves. (3) Rear propulsion pump. (4) Charge relief valves. (5) Line from hydraulic oil cooler. (6) Closed circuit loop line. (7) Neutralizer valves. (8) Pressure limiter valves. (9) High pressure relief valves. (10) Line from steering valve. (11) Closed circuit loop line. (12) Reverse multi-function valve. (13) Pressure limiter valves. (14) Charge check valves. (15) Charge check valves. (16) Speed shift valve. (17) Forward multi-function valves. (18) High pressure relief valves. (19) Line from hydraulic oil filter. (20) Line to hydraulic oil filter. (21) Parking brake valve. (22) Line to vibration cooling valve. (23) Propulsion system cooling valve. (24) Front propulsion motor. (25) Parking brake. (26) Hydraulic oil cooler. (27) Hydraulic oil tank. (28) Rear propulsion motor. (29) Speed control valve.

When the engine is running, front and rear propulsion pumps (1) and (3) and the steering pump are rotating. The return oil from the steering valve provides the charge oil for the propulsion system. The maximum charge oil pressure in neutral is controlled by two charge relief valves (4) in the two propel pumps and the charge relief valve in the vibration pump. The charge oil is used as make-up oil for propulsion pump and motor leakage, cooling for the propulsion pumps and motors, to move the propulsion pump swashplates, to release the parking brake and to shift motor displacement for high and low speed.

Pump control valves (2) are connected to each other by a linkage rod. Both pump control valves always move together. The front propulsion pump supplies oil for front propulsion motor (24) and the rear propulsion pump supplies oil to rear propulsion motor (28).

In neutral, pump control valves (2) are in the center position. Charge oil is blocked at the control valves. With no pressure to either side of the swashplate there is no oil flow from the propulsion pumps. Charge oil goes through charge check valves (14) and (15) to the closed circuit loop lines (6) and (11) of each system. Charge oil also goes to both sides of propulsion system cooling valve (23) and positions the valve in the center. This blocks oil flow to the vibration cooling valve.

With the parking brake button pushed in (applied), parking brake valve (21) and neutralizer valves (7) are not energized. The springs in parking brake (25) apply the parking brake. The neutralizer valves connect the passages for the pump control piston together and prevent the swashplate from moving out of neutral.

Forward, Low Speed With Parking Brake Off

When the parking brake button is pulled out (released), parking brake valve (21) and neutralizer valves (7) are energized. The parking brake valve shifts to the left. Charge oil goes to parking brake (25) and moves the piston against the spring force and releases the parking brake. The neutralizer valves shift to the left when energized. The passage for each side of the pump control piston is now separated and the swashplate will move when oil is directed to one side.

When the propulsion control lever on the operator console is moved forward, pump control valves (2) are shifted to the right. This allows charge oil to go to one side of the pump control piston and opens the other side to drain. The farther the pump control valve is moved, the more the swashplate moves and the pump oil flow increases. High pressure oil in closed circuit loop lines (11) goes to each propulsion motor. Low pressure oil in closed circuit loop lines (6) leaves each propulsion motor and returns to the propulsion pumps.

Charge check valve (15) inside forward multi-function valve (17) closes when high pressure oil is pumped along closed circuit loop line (11). Charge check valve (14) inside reverse multi-function valve (12) opens to allow oil from charge circuit oil to enter low pressure closed circuit loop line (6). This compensates for internal leakage within the different circuit components.

High pressure oil in closed circuit loop line (11) moves the shuttle valve spool inside propulsion system cooling valve (23) to the right. Hot low pressure oil flows from the propulsion system cooling valve to the vibration cooling valve through oil line (22). This allows fresh charge oil to enter low pressure closed circuit loop line (6) through charge check valve (14).

Forward multi-function valves (17) contains pressure limiter valves (13) and high pressure relief valves (18). When system pressure of 42 000 kPa (6090 psi) is reached in the high pressure loop, the pressure limiter valve routes oil to pump control valve (2) and the pump servo piston. An orifice in the pump control valve raises the oil pressure in the passage which shifts the pump servo piston, causing the propulsion pump to destroke. The destroking of the propulsion pump reduces pump output pressure.

High pressure relief valves (18) protects the system from sudden high pressure spikes. When system pressure of 44 000 kPa (6430 psi) is reached in the high pressure loop, high pressure relief valves (18) routes the oil to the low pressure loop and hydraulic oil tank.

Oil from the case of front propulsion pump (1) goes to the case of front propulsion motor (24), and then to hydraulic oil tank (27). Oil from the case of rear propulsion pump (3) goes to the case of rear propulsion motor (28), and then to hydraulic oil tank (27).

When the speed selector switch on the operator console is in the LOW speed position, speed shift valve (16) is not energized. In this position the speed shift spool in each propulsion motor is open to drain. Each propulsion motor is in maximum (large) displacement (low speed).

Reverse, High Speed With Parking Brake Off

Propulsion System Schematic
(1) Front propulsion pump. (2) Pump control valves. (3) Rear propulsion pump. (4) Charge relief valves. (5) Line from hydraulic oil cooler. (6) Closed circuit loop line. (7) Neutralizer valves. (8) Pressure limiter valves. (9) High pressure relief valves. (10) Line from steering valve. (11) Closed circuit loop line. (12) Reverse multi-function valve. (13) Pressure limiter valves. (14) Charge check valves. (15) Charge check valves. (16) Speed shift valve. (17) Fotward multi-function valves. (18) High pressure relief valves. (19) Line from hydraulic oil filter. (20) Line to hydraulic oil filter. (21) Parking brake valve. (22) Line to vibration cooling valve. (23) Propulsion system cooling valve. (24) Front propulsion motor. (25) Parking brake. (26) Hydraulic oil cooler. (27) Hydraulic oil tank. (28) Rear propulsion motor. (29) Speed control valve.

When the propulsion control lever on the operator console is moved in the reverse direction, pump control valves (2) are shifted to the left. This allows charge oil to go to one side of the pump control piston and opens the other side to drain. The farther the pump control valve is moved, the more the swashplate moves and the pump oil flow increases. High pressure oil in closed circuit loop lines (6) goes to each motor. Low pressure oil in closed circuit loop lines (11) leaves each propulsion motor and returns to the propulsion pumps.

Charge check valve (14) inside reverse multi-function valve (12) closes when high pressure oil is pumped along closed circuit loop line (6). Charge check valve (15) inside forward multi-function valve (17) opens to allow oil from charge circuit to enter low pressure closed circuit loop line (11). This compensates for internal leakage within the different circuit components.

High pressure oil in closed circuit loop line (6) moves the shuttle valve spool inside propulsion system cooling valve (23) to the left. Hot low pressure oil flows from the propulsion system cooling valve to the vibration cooling valve through oil line (22). This allows fresh charge oil to enter low pressure closed circuit loop line (11) through charge check valve (15).

Reverse multi-function valve (12) contains pressure limiter valves (8) and high pressure relief valves (9). When system pressure of 42 000 kPa (6090 psi) is reached in the high pressure loop, pressure limiter valve (8) routes oil to pump control valve (2). An orifice in the pump control valve raises the oil pressure in the passage which shifts the pump servo piston, causing the propulsion pump to destroke. The destroking of the propulsion pump reduces pump output pressure.

High pressure relief valves (9) protects the system from sudden high pressure spikes. When system pressure of 44 000 kPa (6430 psi) is reached in the high pressure loop, the high pressure relief valve routes the oil to the low pressure closed circuit loop line and hydraulic oil tank.

When the speed selector switch on the operator console is in the HIGH speed position, speed shift valve (16) is energized. The valve spool moves to the left. In this position the speed shift spool in each propulsion motor is supplied with charge oil. Each propulsion motor is in minimum (small) displacement (high speed).

Rear Axle Assembly

Without No-Spin Differential

Components
(1) Left sun gear and shaft. (2) Left planetary gears (three). (3) Left planetary gear needle bearings. (4) Left ring gear housing. (5) Pinion shaft. (6) Pinion tapered roller bearings. (7) Right ring gear housing. (8) Right planetary gears (three). (9) Right planetary gear needle bearings. (10) Right sun gear and shaft. (11) Left axle seal. (12) Left axle bearing. (13) Left axle shaft. (14) Axle retaining bolt. (15) Left drive axle housing. (16) Left planetary ring gear. (17) Differential case. (18) Differential ring gear. (19) Differential side gear (two). (20) Differential tapered roller bearings. (21) Right planetary ring gear. (22) Right drive axle housing. (23) Right axle shaft.

Operation

Power from the rear drive motor goes through a reduction unit that is coupled to the rear axle by the splines on pinion shaft (5). Pinion shaft (5) is supported by tapered roller bearings (6). Differential ring gear (18) is fastened to differential case (17) by rivets. The torque from the case goes through a four pinion differential to sun gear and shafts (1) and (10). Shafts (1) and (10) are connected by splines to side gears (19) of the differential. Planetary ring gears (16) and (21) are pressed into ring gear housings (4) and (7). Planetary gears (2) and (8) are mounted to the carrier by shafts and rotate on needle bearings (3) and (9). There are three planetary gears in each carrier. Each carrier is located inside of ring gears (16) and (21).

When the sun gear and shafts are driven by the differential, the planet gears and carriers are forced to rotate inside the stationary planetary ring gear. The carriers will rotate at a slower speed than the sun gears. The carriers are connected to axle shafts (13) and (23) with internal splines.

Rear axle shafts (13) and (23) are mounted in tapered roller bearings and the end play is adjusted by means of a shim under retaining bolt (14). The axle shafts have flanges at the outside ends to mount the wheels.

With No-Spin Differential

Components
(1) Left sun gear and shaft. (2) Left planetary gears (three). (3) Left planetary gear needle bearings. (4) Left ring gear housing. (5) Pinion shaft. (6) Pinion tapered roller bearings. (7) Right ring gear housing. (8) Right planetary gears (three). (9) Right planetary gear needle bearings. (10) Right sun gear and shaft. (11) Left axle seal. (12) Left axle bearing. (13) Left axle shaft. (14) Axle retaining bolt. (15) Left drive axle housing. (16) Left planetary ring gear. (17) Differential case. (18) Differential ring gear. (19) No-spin differential. (20) Differential tapered roller bearings. (21) Right planetary ring gear. (22) Right drive axle housing. (23) Right axle shaft.

Operation

Power from the rear propulsion motor goes through a reduction unit that is coupled to the rear axle by the splines on pinion shaft (5). The pinion shaft is supported by pinion tapered roller bearings (6). Differential ring gear (18) is fastened to differential case (17) by rivets. The torque from the case goes through a four pinion differential to left and right sun gear and shafts (1) and (10). The sun gear and shafts (1) and (10) are connected by splines to no-spin differential (19). The differential ring gear and differential assembly is partly immersed in oil thus providing adequate lubrication for bearings and bushings. Left and right planetary ring gears (16) and (21) are pressed into left and right ring gear housings (4) and (7). The three planetary gears are mounted in a carrier and are positioned around the sun gear and within the planetary ring gear. Left and right planetary gears (2) and (8) are mounted to the carrier by shafts and rotate on left and right planetary gear needle bearings (3) and (9). Each carrier is located inside of left and right planetary ring gears (16) and (21). When the sun gear and shafts are driven by the no-spin differential, the planet gears and carriers are forced to rotate inside the stationary planetary ring gear. The carriers will rotate at a slower speed than the sun gears. The carriers are connected to left and right axle shafts (13) and (23) with internal splines.

Left and right axle shafts (13) and (23) are mounted in tapered roller bearings and the end play is adjusted by means of a shim under axle retaining bolt (14). The axle shafts have flanges at the outside ends to mount the wheels.

The no-spin differential powers both wheels and yet freely permits wheel speed differentiation when required.

These are the three main functions:

(1) Assures 100% of the available torque.

(2) Prevents wheel spin and power loss when one wheel loses traction.

(3) Compensates for differences in wheel travel when turning or operating on uneven surfaces.

The drive axle is equipped with a no-spin differential. Note that there are no spider gears, but rather two drive members, called driven clutch assemblies. They mate with a spider assembly which is driven by the ring gear through the differential support case.

As long as the vehicle is operated in a straight forward or reverse direction over a smooth surface, the driven clutch assemblies remain locked to the spider assembly. The no-spin differential allows the vehicle to perform with axle completely locked. This means that both wheels turn at the same speed. If one wheel loses traction or leaves the ground, the opposite wheel, which still has traction, continues to drive the vehicle until traction is gained by both wheels. There can be no one wheel spinout.

When the vehicle turns a corner, or when one wheel passes over an obstruction, the outside wheel, or the wheel passing over the obstruction, must travel a greater distance and therefore faster than the other wheel. When this occurs, the no-spin differential automatically allows for the necessary difference in wheel speed.

During a turn, the inside driven clutch remains completely engaged with the spider and continues to drive the vehicle. The outside driven clutch automatically disengages from the spider, allowing the outer wheel to turn freely in the turn. When the vehicle completes the turn, the outside driven clutch automatically reengages the spider, as both wheels again travel at the same speed.

Operation In Forward Or Reverse

When a no-spin differential equipped vehicle is operated straight forward or reverse, over smooth terrain, the spider assembly and driven clutch assemblies remain fully engaged. The no-spin differential operates as a "locked unit"; both wheels are drive at ring gear speed and direction.

Operation In Turns

When making a turn, differential action is required to permit the outside wheel to travel a greater distance, and faster, than the inside wheel. The no-spin differential allows the outside wheel to turn faster than the ring gear speed but does not permit either wheel to turn slower than the ring gear when engine power is applied.

When making a right turn, the right driven clutch of the no-spin differential remains fully engaged with the spider. The spider transmits power to the right driven clutch, which drives the right (inside) wheel at ring gear speed. The left (outside) wheel covers a greater arc than the right (inside) wheel, and is driven by the traction of the road, turns faster than ring gear speed. The left driven clutch turns faster than the spider. The springs act as return devices for the driven clutches when their speeds are again equal.

The teeth on the right side of the center cam mesh securely with the teeth on the right driven clutch. With the center cam locked in this position (so that it cannot rotate with respect to the spider), the cams on the left side of the center cam serve as ramps upon which the mating teeth on the left driven clutch can rise, enabling that driven clutch to disengage from the spider.

After the left driven clutch assembly rotates forward, the slot in the left holdout ring contacts the spider key, and positions its lugs ahead of the slots in the center cam. This prevents the left driven clutch from reengaging with the spider as it rotates faster than ring gear speed. When this over-running action ceases and the relative speed of the spider and over-running clutch become the same, the left holdout ring lugs reengage the center cam slots, permitting the left driven clutch to return to full engagement with the spider.

When negotiating a left turn, this procedure is reversed and the operating principle is identical.