CHAPTER 21 



OTHER AUXILIARY EQUIPMENT 



In addition to the shipboard auxiliary machin- 

 ery described in previous chapters of this text, 

 there are a number of other units of machinery 

 that are essential to the operation of a ship and 

 which are directly or indirectly of concern to 

 engineering department personnel. Such aux- 

 iliary machinery includes steering gears and 

 their remote control equipment, elevators, 

 winches, capstans, windlasses, and catapults. 

 Some of this machinery may be located within 

 the engineering spaces of the ship; but many of 

 the units are located outside the engineering 

 spaces and are sometimes referred to as out - 

 side machinery . 



ELECTROHYDRAULIC TRANSMISSION 



Some shipboard auxiliary machinery must 

 operate at variable speeds over a considerable 

 range. In addition, there must be close control 

 of speed between minimum and maximum limits. 

 Many auxiliary machines operate with a high 

 starting torque and must be capable of ac- 

 celerating to maximum speed very quickly. To 

 meet these requirements, the electrohydraulic 

 transmission is used on naval ships. Since the 

 electrohydraulic transmission is utilized in 

 more than one type of auxiliary machine, it is 

 discussed first. 



Electrohydraulic transmissions are usedfor 

 driving or controlling machinery such as steer- 

 ing gears, gun turrets, anchor windlasses, boat 

 and airplane handling equipment, capstans, 

 hoists, and certain shipboard valves. Some 

 electrohydraulic transmissions are designed to 

 deliver rotary motion; others are designed to 

 deliver reciprocating motion. 



An electrohydraulic transmission designed 

 to deliver rotary motion to an auxiliary machine 

 consists basically of an electric motor, a hy- 

 draulic pump, a hydraulic motor, and piping to 

 allow the flow of fluid from and to the pump 



through the motor. The pump is of the variable 

 displacement reversible type^; it is sometimes 

 called the A-end of the transmission. A complex 

 machinery system may include one or more 

 pumps and one or more motors. The hydraulic 

 motor of an electrohydraulic transmission is 

 similar in design to the pump, except that the 

 motor is usually of fixed displacement. Occa- 

 sionally, to provide very wide speed variation, 

 the motor may also be of the variable displace- 

 ment type. A hydraulic motor for use in an 

 electrohydraulic transmission is shown in figure 

 21-1. 



The components, control equipment, and 

 piping system for an electrohydraulic trans- 

 mission used to drive a winch are illustrated 

 in figure 21-2. The transmission illustrated is 

 typical of those designed to deliver rotary 

 motion to various types of shipboard auxiliary 

 machinery. 



The pump is driven at constant speed by an 

 electric motor. The hydraulic motor is driven 

 by the fluid under pressure, and the auxiliary 

 machine is driven by the mechanical output of 

 the motor. By controlling the variable output of 

 the pump, the direction and speed of rotation of 

 the motor can be controlled; therefore, the 

 direction and speed of motion utilized in the 

 operation of the auxiliary machine can be con- 

 trolled. 



The flow of fluid under pressure from the 

 pump to the motor exerts force on the faces of 

 the pistons open to the valve port receiving the 

 fluid under pressure. This force on the piston 

 results in a thrust component along the axis of 

 rotation of the socket ring and a turning com- 

 ponent at right angles to the thrust component. 



Operating principles of variable displacement pumps 

 are discussed in chapter 15 of this text. 



520 



