Principles of naval engineering - Historic Naval Ships Association

iChapter 21. -OTHER AUXILIARY EQUIPMENTBRAKE OPERATING ROD DRIVING NOT3 \ LINKPEDESTALTO DECKSECUREDRUDDER^YOKE^ BRAKE BAND'RUDDER STOCKTRANSMISSION SHAFTFROM STEERING ENGINEFigure 21-5. —Right-and-left screw steering gear.47.140XELECTRICAL SYSTEMS. -Steering gearcontrol systems of the electrical type are dividedinto two general types— the direct current pilotmotor type and the alternating current synchronoustransmission type. The direct currentpilot motor type is no longer used on newconstruction.The direct current pilot motor type ofremote control consists of a small reversibledirect current motor which is connected throughthe differential gear to the control shaft of avariable displacement hydraulic pump. The controlof the pilot motor is effected by means of amagnetic contactor control panel located adjacentto the motor and through master controllerslocated at remote control stations. The motoris equipped with a magnetic brake which promptlystops and holds the motor when the mastercontroller is returned to the neutral position.The alternating current synchronous transmissiontype of remote control consists ofinterchangeable receiving and transmitting unitswhich are, in reality, small wound rotor inductionmotors with interconnected three-phaserotor windings; their stator windings are connectedto the same alternating current supply.When the transmitter rotor is turned, the receiverrotor turns at the same speed and inthe same direction.The transmitters are located in steeringstands at remote control stations such as thepilot house, conning tower, central station,etc., and are mechanically connected throughgearing to the wheels. A transmitter at one ofthe remote stations is electrically connected toa receiver in the steering room. Where morethan one remote steering station is provided,as on cruisers and carriers, a switch is providedfor selecting the desired control station.Indicating lights are provided on the steeringstands and at the selector switch to indicate theselected circuit and the power available.The receiver is connected to the control shaftof the variable displacement hydraulic pumpthrough a differential. On large hydraulic unitswhere the torque required to stroke the pump isgreater than the torque that can be exerted bythe receiver, the stroke is controlled through anauxiliary hydraulic servosystem. In installationsinvolving the use of a servosystem, the synchronousreceiver actuates a pilot valve whichcontrols the flow of oil, under pressure, toand from a power cylinder. The direction andamount of motion of the power piston controlsthe stroke of the main pump which actuates therudder.Electrical control circuits from the transmitterselector switch (from the pilot houseselector switch in the case of destroyers andauxiliary vessels) to the steering gear compartmentare installed in duplicate. Drum-typeselector switches, one in the steering room andone located at the terminus of the duplicate runof control circuits, are provided for selectingthe port or starboard cable. When independentsynchronous receivers are provided for each525