TM 5-2410-240-23-1
0007
HYDRAULIC SYSTEMS CONTINUED
Hydrostatic Drive Motor Operation
0007
The driveshaft (Figure 11, Item 1), retainer (Figure 11, Item 4), pistons (Figure 11, Item 6), and barrel (Figure 11,
Item 9) rotate within the hydrostatic drive motor. The motor case (Figure 11, Item 2), head (Figure 11, Item 7), and
control lens (Figure 11, Item 8) do not rotate.
The spring (Figure 11, Item 10) pushes the barrel (Figure 11, Item 9) against the control lens (Figure 11, Item 8) to
ensure a high-pressure seal between the barrel and the control lens and between the control lens and the head
(Figure 11, Item 7).
The control lens (Figure 11, Item 8) has two oil control slots, one for the high-pressure loop and the other for the
low-pressure loop.
When the high-pressure oil is at the high-pressure loop port, it flows to the control slot in the control lens (Figure 11,
Item 8) and then into the cylinders of the barrel (Figure 11, Item 9) that are over the control slot.
The retainer (Figure 11, Item 4) holds the spherical piston heads in the sockets in the driveshaft (Figure 11, Item 1).
The barrel (Figure 11, Item 9) holds the seven pistons (Figure 11, Item 6) and rotates around the pivot pin (Figure
11, Item 12), which is at an angle to the axis of the driveshaft. Because of the bent-axis relationship between the
barrel and the shaft, the seven pistons move in and out of the cylinders as pressure oil enters and leaves the
cylinders. This movement forces the pistons, the barrel, and the driveshaft to rotate.
While the pistons (Figure 11, Item 6), the barrel (Figure 11, Item 9), and the driveshaft (Figure 11, Item 1) continue
to rotate, the piston reaches the fully retracted position. At the same time, the cylinder begins to overlap the control
slot in the control lens (Figure 11, Item 8) on the low-pressure side of the loop. At this point, the piston starts to
move back into the barrel. As the piston moves back into the barrel, the piston pushes oil out of the cylinder
through the control slot to the low-pressure side of the loop.
The motor bearings receive oil for lubrication and for cooling from the hydraulic oil cooler. The oil flows from the
hydraulic oil cooler through the port (Figure 11, Item 3) to the motor bearings. The remainder of the internal
components receives lubrication from this oil and by normal leakage from the pistons (Figure 11, Item 6) and from
the barrel (Figure 11, Item 9).
The speed sensor (Figure 11, Item 5) sends two signals back to the machine ECM as the teeth of the ring gear
(Figure 11, Item 11) rotate past the speed sensor. The signals produced by the speed sensor determine motor
speed and direction.
0007-12
