The B-end is the hydraulic motor of the CAB unit. Physically, it is very similar to the construction of the A-end. A B-end converts fluid pressure from the A-end into a rotary mechanical motion. In a CAB unit installation, the B-end is secured to the opposite face of the valve plate. In the Special K type of units, the B-end(s) is/are separately mounted and receive fluid by transmission lines.
The major components of the B-end are shown in the upper portion of figure 4-28. The bearing housing, the cylinder barrel housing, and the valve plate enclose and support the other components of the motor. The unit is sealed to prevent fluid leakage.
The output drive shaft of the B-end rotates on bearings inside the bearing housing. The shaft connects to the mechanical drive train units of the power drive system. It also drives the response gearing of the B-end that provides launcher position information to the control assembly.
The socket ring of the B-end is mounted to the other end of the drive shaft. The socket ring causes the drive shaft to rotate. The socket ring is attached to the cylinder barrel by connecting rods and a drive link and pin.
The cylinder barrel bears on and rotates against the side of the valve plate face of the B-end. The cylinder barrel is bearing-mounted to a stub shaft in the valve plate face. The cylinder barrel of the B-end has the same number of cylinder bores as the A-end. The cylinders are open at their lower end to receive and return fluid to the A-end.
Just as the tilt plate of the A-end had to be tilted to develop a pumping action, the B-end must also be "tilted' to develop a rotation. In relation to the valve plate, the socket ring in figure 4-28 is installed at an angle. The socket ring of the B-end is normally placed at (about) a 30-degree fixed angle. It is sometimes referred to as the "fixed tilt plate" of the B-end.
In operation, the B-end responds directly to the A-end. If the tilt plate of the A-end is on neutral, no pumping action takes place and no fluid transfer is accomplished. The B-end is not rotating in this situation; the missile launcher is stopped.
In view A of figure 4-32, the A-end has gone off neutral and is pumping. The output fluid of the A-end acts on some of the pistons of the B-end and pushes them. Because of the imposed angle of the "fixed tilt plate," the drive shaft of the B-end starts rotating.
The speed and direction of rotation of the B-end are factors determined by the A-end. The amount of tilt of the A-end determines the speed of rotation of the B-end (small tilt, slow speed; large tilt, fast speed). As long as the A-end is on tilt, the B-end will continue to rotate. When the tilt of the A-end is removed (returned to neutral), the B-end will stop. The direction of rotation of the B-end is determined by the direction of tilt applied to the tilt plate of the A-end. View B of figure 4-32 shows the reaction of the components of the B-end when fluid flow is reversed.
DUAL GEAR PUMP ASSEMBLY
The dual gear pump assembly (fig. 4-33) of a CAB
type of power drive is better known as the servo and supercharge pump assembly. The pump housing is physically mounted to the aft end of the electric motor. When the motor is running, a common drive shaft turns both gear pumps. (Meanwhile, the forward end of the electric motor is also driving the A-end.)
The dual gear pump housing is similar to that described with a single gear pump of an accumulator type of power drive. (Refer to fig. 4-20.) A divider plate separates the two pumping chambers. The larger gearset belongs to the servo pump. The smaller gearset is for the supercharge pump. Both pumps share a
Figure 4-32.-Basic operation of the B-end.
Figure 4-33.-Dual gear pump assembly.
common intake or suction port. They draw their fluid through a suction screen/strainer in the main fluid supply tank.
Two separate output lines direct the discharge fluids to a valve block assembly. Here the fluids are filtered, controlled, and regulated. The servo fluid normally charges a small accumulator and is distributed to the hydraulic system of the power drive. Servo fluid pressure is the higher of the two and, as mentioned before, normally ranges between 400 and 500 psi. It is used for control purposes, primarily in the control assembly of the power drive.
Supercharge fluid pressure is the lower of the two. It does not charge an accumulator and only averages around 100 psi. Supercharge fluid is supplied directly to the CAB unit. Here it compensates for or replenishes fluid lost through internal slippage and leakage.