Illustration No. 66 shows the hydraulic circuit for the RATAAC fan system. Oil from the small (rear) hydraulic pump enters the RATAAC fan speed control valve where the sequencer valve ensures that a sufficient supply of oil is first available to the pressure reducing manifold. The pressure reducing manifold supply has priority over the RATAAC supply. The sequencer valve maintains a minimum oil pressure to the pressure reducing manifold.
The relief valve is installed to limit the maximum RATAAC fan system pressure and the maximum RATAAC fan speed. The relief valve is pilot operated. Oil enters the left end of the relief valve and the pressure moves the spool to the right, against the spring. At the same time, oil flows through an orificed passage in the center of the spool and acts against the right end of the spool. The reduced oil pressure plus the force of the spring at the right end of the spool balances against the pressure at the left end of the spool. The result is a constant pressure in the fan system, proportional to the engine rpm. Oil that is drained by the relief valve returns to the hydraulic tank.
The accumulator helps maintain a constant system pressure when there are pressure fluctuations in the fan circuit. The accumulator also serves as a "shock absorber" for the system during pressure spikes.
INSTRUCTOR NOTE: During lab exercises, the following pressures may be observed:
- The sequencer valve is adjusted at low idle and the pressure observed (HFPD) should be approximately 4068 kPa (590 psi). At high idle, the pressure observed should be
approximately 5860 kPa (850 psi). (Note that once the sequencer valve opens, at
approximately 4068 kPa (590 psi), the pressure in the small pump circuit is then controlled by the relief valve for fan system pressure.)
- The relief valve for fan system pressure is adjusted at high idle and the pressure observed (HFMI) should be approximately 5690 kPa (825 psi). The RATAAC fan speed at high idle should be approximately 3100 rpm.
Always refer to the latest revision of the Service Manual for your machine serial number, "Specifications, Systems Operation, Testing and Adjusting - Hydraulic System" (Form No. RENR7540) for the most recent specifications of system pressures.
The RATAAC components are mounted to the under side of the hood. These components are: 1. air intake and pre-cleaner for the RATAAC (cooling air)
2. air intake and pre-cleaner for engine intake air (cooled air) 3. left and right exhaust pipes (with ejector tubes)
4. left and right muffler inlets
5. dust ejector hoses (connecting the pre-cleaners to the dust ejector tubes in exhaust pipes) 6. intake air tubes to air cleaner canister inlets (from RATAAC air pre-cleaner)
7. RATAAC heat exchanger core outlets (cooled intake air to intake manifold) 8. RATAAC heat exchanger core inlets (from air cleaners)
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The illustration above shows the RATAAC sub-assembly (upside down). The major components identified are:
1. RATAAC hydraulic fan motor
2. dust ejector tubes (from pre-cleaner to exhaust pipe) 3. heat exchanger cores
The heat exchanger core access panels (4) are removed in the illustration above. The cores may be accessed and cleaned through these passages.
Refer to the D10T Operation and Maintenance Manual (Form No. SEBU7764) for information about recommendations for cleaning the RATAAC heat exchanger cores.
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Shown above is the implement pump. The rear section of the implement pump (1) provides high pressure oil for the RATAAC fan motor and for pilot supply to the pressure reducing valve and the dual tilt valve. Attached to the pump is the RATAAC fan speed control valve (2). Components and service points identified above are:
3. Hydraulic Fan Pump Discharge pressure test port (HFPD) 4. Hydraulic Fan Motor Inlet pressure test port (HFMI) 5. RATAAC fan motor supply
6. sequencer valve (ensures that pilot supply has priority over RATAAC supply) 7. relief valve (limits the maximum pressure in the RATAAC circuit)
8. relief to tank
9. accumulator (ensures continuous RATAAC circuit pressure and protects against surges) 10. supply to the pilot manifold
NOTE: The fitting for dual tilt pilot supply oil is on the front side of the manifold,
beneath the fan supply line. It cannot be seen in the illustration, above.
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POWER TRAIN
Shown above is an illustration that identifies the relative location of all of the major power train components for the D10T Track-type Tractor. Numerous upgrades have been implemented in the power train for the D10T Track-type Tractor, as compared to the D10R machine. The most prominent of these upgrades include:
- the torque converter impeller has been re-engineered to provide slightly more engine lug; - the elimination of the transmission intermediate speed sensors;
- transmission output speed sensors that are more easily installed and require no adjustment; - the elimination of the priority valve and the lube management valve simplifies the system,
making it more reliable and easier to service and troubleshoot;
- a new A4 Power Train ECM controls the transmission, the braking, and the steering; - a new four-section power train oil pump;
- easy access to two, 6-micron power train oil filters; and - extended change intervals for power train oil filters.
Power Train Oil Pump Power Train Oil
Fill Tube and Dipstick
C27 ACERT Engine
Power Train ECM
Transfer and Bevel Gears Electronic
Steering Clutch and Brake Valve
Transmission
Hydraulic Control Transmission Steering Clutches
and Brakes Final Drives
Power Train Oil Cooler No. 1 Power Train
Oil Cooler No. 2 Torque Divider
Torque Converter Outlet Relief Valve
Transmission Charging Filter
Torque Converter Charging Filter Torque Converter Intlet Relief Valve Lube Distribution
Manifold