The steering gear and plane operating gear operates on a traveling screw-fixed nut principle.  Pushbutton electric control is provided, and hand-wheels are fitted for emergency and silent-running service.  Bow planes are permanently rigged out.  Twin steering rudders are provided.  
          Rudders and planes are well located to obtain maximum effect with minimum area.  
        The systems are compact, but are not otherwise unusual in any respects, and do not warrant exploitation.
March, 1946


C  O  N  F  I  D  E  N  T  I  A  L
          Steering arrangements consist of twin rudders, linkage joining the tiller heads and leading forward into the after torpedo room, a traveling worm steering machine driven by an electric motor, electric steering stations in the control room and conning tower, and an emergency hand steering station in the after torpedo room.  Associated therewith are the necessary thrust bearings, limit stops, clutches, wiring and indicators.  
          The stern plane system consists of twin planes and related components similar in principle to those of the steering system.  All operating stations, however, are in the control room, shafting being led forward from the after torpedo room for the hand operation of the stern planes.  
          The bow plane system consists of twin, permanently rigged-out planes, with operating gear similar in principle to that of the steering system and stern planes.  Operating mechanism is located in the forward torpedo room, but operating stations are in the control room, and shafting is accordingly led aft from the torpedo room to the control room.  
          The rudders are of the balanced streamlined hollow spade type, with the interior space filled with wood.  Each has a plane area of 3.111 m2 (33.4 sq. ft.) of which .779 m2 (38.4 sq. ft.) is forward of the stock.  They are located 975 mm (38.4") out from the centerline of the vessel, and 225 mm (8.85") in toward the center of the vessel from the center of the propellers.  
          The rudders are suspended, the weight and thrust being carried by bearings in the rudder trunk and at the head of the stock.  Stops are at 30 degrees port and starboard.  
          The stocks are provided with tillers, which are joined by connecting rods to a linkage which translates the athwartships movement to fore and aft movement.  Another connecting rod leads forward from the linkage to a crosshead.  
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          From the crosshead, the rudder drive shaft leads forward through a stuffing box into the after torpedo room.  The inboard end of the shaft is fitted with a double trapezoidal thread of 20 mm pitch on an outside diameter of 88 mm (.79" pitch x 3.47" diameter).  The shaft moves forward or aft depending on the direction of rotation of a section of shaft which combines the features of a nut and thrust bearing.  
          Forward of this last mentioned fitting is a sound isolation coupling, the worm drive from the electric motor and the hand-operated jaw clutch which connects either the electric or hand steering gear, and at the forward end of the shaft, working through two sets of bevel gears, is the emergency steering wheel and mechanical indicator which are mounted on a column suspended from the overhead and are swung out of the way when not in use.  
          The drive motor is rated at 6.2 to 11.8 H.P. depending on voltage, speed and duration of operating period.  Weight is 530 lbs.  It is shunt wound type equipped for dynamic breaking, and is spray tight.  
          The motor control consists of a magnetic controller, the relay circuit of which is wired through to a selector switch in the control room.  The selector switch extends the circuit either to the permanently connected control stand in the control room, or to a branch terminal box in the conning tower.  From the box in the conning tower the circuit can be extended to the conning tower control station as the bridge control stations by means of three-conductor cable.  When the bridge station is used, the cable is led down through the upper conning tower hatch to the conning tower terminal.     
          The control system also includes a spray-tight travel limit switch which opens the motor circuit when the rudder gear reaches the end of the established travel.  This operates through a reduction gear on the nut, which turns on the threaded portion of the inboard rudder drive shaft.  The limit switch operates on a worm and traveling nut principle, with cams which, at the end of the worm travel engage contacts, initiate dynamic breaking and stop the motor.  Damping coils extinguish the resulting arc.  
          Also connected to the same reduction gear as the limit switch is the electric rudder angle indicator, from which leads connect to repeaters in other parts of the vessel, as described in the section on intercommunications (S65).  
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          Electric movement of the rudder is accomplished by depressing the "port" or "starboard" pushbutton at the steering station in use, employing the palm or the heel of the hand.  Depressing the button closes the circuit to the magnetic controller, which starts the steering motor.  The motor in turn, operating through the reduction gear, rotates the female threaded member on the shaft at the thrust bearing, thereby pulling in or pushing out the shaft connecting with the rudder linkage.  When the button is released, it returns to normal under control of a spring, opens the circuit to the magnetic controller, which in turn closes the dynamic breaking circuit and then opens the power circuit, thereby stopping the motor.  No follow-up is provided, and the rudder remains at the angle set until the angle is changed by further action at the control stand.  Control of steering at the operating stations is facilitated by providing a gyro repeater and a rudder angle indicator repeater at each station (Note that certain of these units are portable, so the number of repeaters does not correspond to the number of steering stations).  
          Hand steering is initiated by rigging the hand steering column, attaching the steering wheel which is stowed separately, setting the mechanical angle indicator to correspond to the existing rudder angle, and operating the clutch which disengages the electric drive and engages the handwheel.  It is to be noted that the electric rudder angle indicator remains in operation, is that locations in the vessel can be kept informed of the rudder angle.  Further, it is possible to carry one of the portable gyro repeaters aft to the torpedo room and there connect it, permitting personnel at the handwheel to follow course without recourse to telephone or loudspeaker system.  
          The stern planes are located directly aft of the propellers in the horizontal plane with the center of the propeller shafts.  The plane area of each plane is 2.56 sq.m. (27.4 sq.ft.) of which .82 sq.m. (8.76 sq.ft.) is forward of the stock.  They are arranged to work from 30 degrees rise to 30 degrees dive and are normally secured at 2 degrees dive.  This is a change from previous practice, promulgated in 1943 to reduce the tendency of surfaced vessels to run under.  (See Special Wartime Experience - Part XXIV, page 1).   
          The bow planes are located 1500 mm (4.92 ft.) above the bottom of the pressure hull, just forward of the forward end of the pressure hull at frame 126.  The plane area  
    - 3 -


  of each plane is 2.84 sq. m. (30.3 sq.ft.) of which .94 sq.m. (10.1 sq. ft.) is forward of the stock.  They are arranged to work from 25 degrees dive to 25 degrees rise, and are normally secured at 7 degrees rise.  This plane positioning also stems from the same directive referred to above.  Plans available show a designed 5 degree zero setting.  
          The plane operating gear is similar to that described above for the steering gear, although it is of different size.  The planes are connected port and starboard to a common stock which is provided with a tiller arm.  The crosshead, threaded inboard shaft, and all other components follow the same basic design principles as those employed for the steering control, except for the following.  
          a)  A low pressure air cylinder, with piping to the control room, is provided to permit operation of the power-to-hand clutch from the control room.  
          b)  Shafting is led from the end of the power drive to the control room, where the hand operating wheels are located.  
          c)  In addition to the electric plane angle indicator, a mechanical indicator is connected to the limit switch drive shaft, a plane operating gear.  The mechanical indicator dial for each pair of planes is located in the control room, adjacent to the diving station.  
          The bow and stern plane motors are both rated at 4.0 to 6.8 horse power, depending on voltage and speed.  Weight is 364 lbs.  Like the steering rudder motor, they are shunt wound, and arranged for dynamic braking. They are water-tight.  
          The motor control is likewise similar to that for the steering rudder, both in the type of manual switching at the diving stations and in the type of magnetic controller.  
          The travel limit switches, while similar in interior construction to the one associated with the steering control, are water-tight.  The electric plane angle indicator is identical with that used on the steering system.  
          Electric movement of the stern planes is accomplished by depressing the "up" or "down" pushbutton at the after diving plane station.  The sequence of operations is the same as that described above for the steering system.  
    - 4 -


          The electric operation of the bow planes is controlled from the forward diving plane station.  
          Each station had its related electric and mechanical plane angle indicator, and, in addition, depth gauges and trim gauge.  
          Hand plane control is initiated by operating the clutch switch which disconnects the electric plane control and connects the shafting to the wheel at the diving station.  
          It is of interest here to note that later vessels if the type have a third plane control station in the control room and a manual coupling and chain connection between the bow and stern plane handwheels.  These are provided to permit the following type of operation:  
        If there is a casualty to the electric control of either the bow or stern planes, the two hand wheels can be tied together so that two men can simultaneously control the affected planes in hand.  The diving officer connects the third pair of planes and operates them electrically.
          The systems described are of a type which uses available space to maximum advantage.  In addition, wheels have been eliminated for normal use, and are retained solely as an emergency and silent-running means for controlling the rudders and planes.  There is, however, nothing basically unusual in the arrangement of the components.  For details of the electrical components and the indicator systems, reference should be made to the related sections.  
          Rudders and planes appear to be well located to obtain maximum effort with minimum area.  The steering rudders are inboard of the propeller centers, thereby allowing the inboard rudder on a turn to cut across the slip stream of the inboard propeller, thereby increasing the effectiveness of the inboard propeller rudder combination on turning.  The stern planes are immediately aft of, and in plane with the center of, the propellers.  The bow planes are located well down on the vessel, ensuring continual submergence, and are so situated as to minimize pocketing of water flow past them.  Being permanently rigged, however, they are susceptible to damage to a greater degree then retractable bow planes.  
    - 5 -


          Further with respect to rudders, the vertical center of area is relatively higher on the vessel than it is in current U.S. Naval practice, thereby reducing the tendency for the vessel to take a list when turning.  
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