PRINCIPLES OF NAVAL ENGINEERING 



SELF SYNCHRONOUS 

 RECEIVER 



PLANETARY 

 DIFFERENTIAL GEAR 



47.139X 



Figure 21-4.— Arrangement of a double-ram electrohydraulic steering gear. 



To prevent the pressure developed by the 

 hand pump from causing motoring or leakage 

 through the main hydraulic units, the piping 

 from the emergency pump to the main hy- 

 draulic system is so arranged that the high- 

 pressure stop valves may be closed. The 

 emergency pump is usually connected to the 

 main hydraulic system in a manner whereby 

 all ram cylinders will be in use. Since it is 

 necessary to block off the emergency system 

 under normal steering gear operation, the emer- 

 gency lines are usually connected to the drain 

 valves to eliminate the necessity of additional 

 high pressure valves. 



Some ships are equipped with a dual emer- 

 gency, submersible steering system. The pur- 

 pose of this system is to provide emergency 

 steering by means of either electric motor or 

 hand power in event of failure of the main 

 system. This emergency gear, with driving 

 motor integrally mounted, is located in the 

 steering gear compartment of the ship. Hand 

 operation is accomplished by use of a re- 

 motely located crank stand connected to the 

 unit by shafting. 



REMOTE CONTROLS - Electrohydraulic 

 steering gears may be controlled from remote 

 steering stations (1) electrically by either a 



pilot motor and its controller or by a syn- 

 chronous transmission; (2) hydraulically by 

 means of a telemotor system; or (3) mechan - 

 ically by means of wire rope. (See subsequent 

 section on remote control systems.) 



Only a few pilot motor control systems are 

 in use; the majority of naval ships utilize either 

 synchronous transmission or hydraulic tele- 

 motor systems. 



In control arrangements for electrohydraulic 

 steering gears, the trick wheel and the receiver 

 of the control system, either synchronous re- 

 ceiver, hydraulic telemotor receiver, or pilot 

 motor, are geared to and actuate the pump con- 

 trol cam through one end of a differential to put 

 the pump on stroke. The follow-up acts through 

 the opposite end of the differential to reverse the 

 movement of the cam and to take the pump off 

 stroke. The differential control unit and cam are 

 so arranged that the control unit may lead the 

 rudder by the full amount of rudder travel. 



REMOTE CONTROL SYSTEMS 

 FOR STEERING GEAR 



Control of the steering gear from the steer- 

 ing wheel on the bridge may be accomplished 

 by any of the following remote control systems. 



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