ABSTRACT
The chart in Figure 16.1 provides a quick system test for hydraulic (fluid) motors. A fluid motor may be thought of as an inverse of a pump, but the operation can be significantly different. A check valve-type piston pump will not function as a fluid motor. Certain pumps are designed to be capable of a motor function and certain motors are designed to provide a pumping function in a specific hydraulic circuit. As an example a drag line, anchor windlass, or crane requires power to lift the load (Figure 16.2). As the load is lowered the motor serves as a pump controlling the rate at which the load is lowered. The power in the lowering mode is provided by the drum which in this function is driving the motor/pump. A through shaft may be provided with a parking brake assembled to the motor (Figure 16.3). The brake is applied by the action of a mechanical spring and is released by application of system pressure of a predetermined value. Considering the potential of the shaft breaking under an exceptional load some safety advocates demand that the brake be placed directly on the driven shaft beyond the motor/pump drive coupling (Figure 16.4).
