RING-PISTON 1801252 - Caterpillar

As signal pressure increases, servo spool (5) pushes down on pressure regulating spring (4). The machine speed increases as a result.As servo spool (5) moves down, high pressure oil is directed to the bottom of actuator (7). (The oil passage is not shown.) The high pressure oil flow causes actuator (7) to move up against the force of actuator bias spring (6). Port plate (13) is mechanically connected to actuator (7) with pin (8). Port plate (13) and barrel (14) move to the minimum angle.Motor Control Group
Illustration 8 g00749926
Minimum displacement (1) Drive motor stroking rate adjusting screw (2) Pressure regulating spring (3) Servo spool (4) Actuator bias spring (5) Pin (6) Actuator (7) Port plate (8) Maximum speed stop screw (Red) High pressure oil (Orange) Signal oil (Green) Tank pressure oil (Yellow) Activated component
As signal pressure increases, the machine speed increases.
Timing of both motors affects the tracking of machine.As the signal pressure increases upon servo spool (3), the spool is forced against the pressure regulating spring (2). As servo spool (3) moves down, high pressure oil is directed to the bottom of actuator (6). (The oil passage is not shown.) This causes the actuator (6) to move up against the force of actuator bias spring (4). Port plate (7) is mechanically connected to actuator (6) by control pin (5) .When the pump output is maximum and the motor begins to destroke, the timing is very critical to the operation of the power train. The stroking cycle of both of the pumps and both of the motors must occur at the same time. If this does not occur, the machine will not track straight. The transmission ECM compensates for normal range of tolerances in the system. However, if the machine does not track straight in FORWARD or REVERSE, the ENGINE ON calibrations must be performed. If these calibrations do not cause the machine to track straight, then a mechanical malfunction in the pumps or motors has probably occurred. Graphs for Drive Pump and Drive Motor Stroking
Method of Transmission Speed Control (Response to Mechanical Adjustment)
Illustration 9 g00722439
Description of Test for Drive Motor Stroking and Test of Drive Pump Stroking The graph shows drive motors (M) and drive pumps (P). As signal pressure (A) increases, machine speed (K) increases.At 3.5 km/h (2.17 mph) or 800 kPa (116.0 psi), drive pump (P) is at the maximum swashplate angle. Drive motor (M) begins to destroke up to a maximum speed of 10.0 km/h (6.21 mph).Calculate Machine Speed over a Specified Distance
Use the following table in order to obtain the machine ground speed:
Table 1
Speed of Machine in Seconds Per 35 Meters and Seconds Per 100 Feet    
Rate of Speed    Seconds per 35 M    Seconds per 100 Ft    
2 km/h     63.0 Seconds     55.7 Seconds    
4 km/h     31.5 Seconds     27.9 Seconds    
6 km/h     21.0 Seconds     18.6 Seconds    
8 km/h     15.8 Seconds     13.9 Seconds    
10 km/h     12.6 Seconds     11.1 Seconds