CONFIDENTIAL REPORT 2G-21
S22
     
 
FORMER GERMAN SUBMARINE TYPE XXI
 
 
 
 
STEERING AND DIVING
 
 
 
 
SUMMARY
  
     
          Steering and plane control and hydraulic retractable bow planes are provided.  Control is elaborate, both hydraulically and mechanically, and is not considered desirable for further exploitation, although the mechanical details of individual valves are of interest.  
     
     
     
     
     
     
     
     
 
March, 1946
 
 
 
 
PORTSMOUTH NAVAL SHIPYARD, PORTSMOUTH, N. H.
 
     
     
     
 
 
     
     

 

     
     
 
  REPORT 2G-21
S22
     
          Steering arrangements consist of a single rudder linkage joining the yoke carrying forward to a single hydraulic ram in the after compartment, hydraulic piping and valves connecting to steering stations in the control room and in the conning tower.  An emergency steering wheel and hand-operated clutch are also located in the after compartment, together with a hand pump which serves as an emergency means for providing oil pressure.  The necessary limit stops and indicators complete the system.  
          The stern plane system is similar in assembly to the steering system.  
          The bow plane system is also similar, but has, in addition, an arrangement to rig the planes out and in.  Retractable bow planes first appear on this type of vessel.  
     
  Steering System  
          The rudder is a balanced, streamlined, free flooding type, with a plane area of 8.06 sq.m. (86.7 sq.ft.), of which 5.91 sq.m. (63.5 sq.ft.) are aft of the stock and 2.15 sq.m. (23.1 sq.ft.) forward.  It is located on the centerline of the vessel 1000 mm (3.28 ft.) aft of frame 0, and the vertical center of the area is at the plane of the propeller shaft centerline.  There are upper and lower bearings, the latter of which carries the weight of the rudder.  
          The stock is fitted with a yoke head, from which connecting rods lead forward, port and starboard to a second yoke.  From one end of the second yoke a connecting rod leads to a crosshead.  The rod from the crosshead leads through a stuffing box into the after compartment of the vessel, and terminates at the piston in the working cylinder of the hydraulic steering gear.  
          Another shaft leads to the piston, and leads through the forward end of the cylinder to the rudder angle indicator.  It is so connected to the piston that fore-and-aft piston motion introduces a rotary motion in the shaft which is transmitted via steering gear to the angle indicator.  
     
 
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          This shaft is also connected through a hand-operated clutch, a chain of gears and shafting to a hand steering station in the after compartment.  
          Piping leads from the working cylinder to a by-pass, which is a spring-loaded piston valve to provide relief in case of excessive back pressure in the return line.  Thence the piping leads to a spring-loaded control valve which gives access to the main hydraulic piping.  The control valve is operated through a linkage by a spring-loaded pilot valve.  This, in turn, is piped to the hand-operated piston valve at the steering station in the control room, and to the hand-operated piston valve at the steering station in the conning tower.  By opening and closing certain valves it is possible to select either station to control steering.  
          Electric rudder angle repeaters are located in the after room, the control room, conning tower and sound room.  In addition, a mechanical angle indicator operated through teleflex cable is provided in the control room of some vessels.  The teleflex cable is so run that it is virtually inaccessible for maintenance, and on the U-2513 has been a continuous source of trouble.  
          To move the rudder, the "port" or "starboard" lever at the steering station is depressed.  This opens ports in the hand-operated control valve which permits a flow of oil to the pilot valve.  The piston on the pilot valve is displaced, thereby operating through linkage to move the pistons in the control valve at the working cylinder, and thereby opening ports to permit flow of oil from the hydraulic oil main into the working cylinder, moving the piston and transmitting the force to the rudder yoke.  If the lever remains depressed, the working piston will continue to the end of its stroke.  If the lever is released, the ports on the chain of valves are closed and the piston remains stationary.  To reverse the direction of travel, the other lever at the steering station is depressed, which opens ports permitting reverse flow through the chain of valves and the working cylinder.  Specified time from hard-over is 10 seconds.  
          If there is hydraulic pressure, but the normal steering stations are inoperative, the rudder can be controlled by a hand lever on the control valve at the working piston.  
          If there is no hydraulic pressure, oil can be supplied in limited quantity by a hand pump in the after compartment, which is able to draw oil from an equalizing tank  
     
 
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  REPORT 2G-21
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          in the after compartment or from the hydraulic oil collecting tank.  
          If hand steering is desired, the clutch is engaged and control is taken at the hand steering station in the after compartment.  
     
  Diving Plane System  
          The stern planes are located 1250 mm (4.10 ft.) forward of frame 0, immediately aft of and in plane with the centerline of the propeller shafts.  Plane area is not 2.76 sq. meters as shown in German texts, but 64.2 sq.ft.  From leading edge to the center of the shaft is 15-3/16" and from the shaft center to the trailing edge is 3'7-3/4".  Stops are set at 28 degrees rise and dive.  Specified time from hard dive to hard rise and vice versa is 6 seconds.  
          The stern plane operating gear is similar in assembly to that described above for the steering system.  The normal operating station is in the control room.  The same alternate methods of control are available, and the hand pump mentioned under the steering system can also be used to supply oil for the stern plane working cylinder.  
          The bow planes are retractable.  They are located in the superstructure at frame 61.6, and when not in service are swung back into the superstructure.  The plane area is not 3 sq. meters as described by the Germans in text material, but 47.2 sq.ft. total.  Distance from the leading edge to the center of the shaft is 11-1/8", and from the center of the shaft to the trailing edge is 3'-0-1/2".  Stops are set at 28 degrees rise and dive and specified time from hard dive to hard rise and vice versa is 6 seconds.  
          The planes are retractable.  The plane stock bearing is mounted on a vertical shaft which turns when planes are rigged in or out.  The inboard end of the plane stock extends in from the bearing about two feet, and is terminated in a rectangular block.  This block slides in a U-section which is, in plan, an arc of a circle the center of which is the centerline of the vertical shaft aforementioned.  When the plane is retracted or rigged out, the U-section guides the inboard end of the stock and retains the plane on a horizontal plane.  
          When the planes are fully rigged out, the rectangular blocks at the inboard ends come into pieces at the ends  
     
 
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  of the tilting shaft which have the same section as the U-section mentioned above.  Rotation of the tilting shaft then introduces tilting of the planes.  
          The mechanism for rigging the planes consists of a hydraulic cylinder in the superstructure, to the piston rod of which are connected two radius rods, each of which extends to the inboard end of one of the plane stocks.  When the piston is moved aft by hydraulic pressure, the inboard ends of the stocks are brought aft to engage the tilting shaft.  At the end of the piston stroke a trigger device on the piston rod is engaged to hold the planes in a rigged out position.  While the planes are rigged out, the entire load tending to force them back into the ship is transmitted through the radius rods to the piston rod, and is carried by the trigger device.  
          The plane tilting mechanism consists of the tilting shaft at the inboard end of the plane stocks, a lever arm on the shaft, a connecting rod leading aft to a second lever arm which is mounted on a shaft rotating in parallel with the tilting shaft.  On this shaft, is a fork which engages a pin on the piston rod.  The piston rod connects between the pistons in two separate cylinders, each of which has one hydraulic oil connection.  A positioning device is provided to insure alignment of the tilting shaft with the guide pieces when rigging planes in and out.  
          The entire foregoing assembly is in the superstructure, the only protection afforded being a vertical cylinder on which the twin pistons are mounted, and which serves as a housing for the fork and pin assembly and as a protection for the open inner ends of the cylinders.  
          To rig the planes, a lever-operated, spring-loaded piston valve is placed off normal, thereby opening ports which permit oil to flow to one end of a piston type pilot valve.  This is displaced, thereby opening ports which permit flow of oil from the hydraulic main to the desired end of the rigging piston, which in turn actuates the linkage described above.  Before rigging in, it is necessary to release the trigger by hand, and a wheel for this purpose is provided overhead in the torpedo room.  
          To tilt the planes, the normal operation requires that one or the other of the levers at the bow plane station in the control room be depressed.  The sequence is then the same as described for the steering rudder and stern planes, except that the operating device consists of one  
     
 
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  piston to raise and one piston to lower the planes.  
          Local hydraulic control in the torpedo room is provided by a lever which operates the control valve directly.  In addition, a supply line is provided from the hand pump in the after compartment.  
          Emergency hand operation is provided by means of a hand wheel which is connected through a bell crank and linkage to the after lever arm referred to in the description of the tilting mechanism.  
          The plane angle indicator is geared to the shaft which is rotated by the piston, pin and fork arrangement, and is brought inboard via a rotating shaft.  The indicators are of the same type as those for the stern planes.  
          Among other things, the bow plane system requires nine openings in the pressure hull, exclusive of grease lines.  
     
  Comments  
          The entire system is unnecessarily elaborate.  The remarks in Naval Technical Mission, Europe, report 305-45 on hydraulic systems apply, and need not be repeated here.  
          The mechanical aspects of the steering and plane systems also appear to be rather involved, as the same work could have been done in all cases with simpler devices.  With specific reference to the bow planes, one concludes that the operating gear was located in the superstructure because there was insufficient space overhead in the torpedo room.  
          It will be noted that the system operation described herein is not the latest version described in Navtechmiseu report 305-45, but the intermediate version therein referred to.  
          The systems have not been entirely satisfactory to U.S. Navy crews.  The steering ram has been a source of considerable difficulty, as it has regularly blown its gaskets or piston leathers.  At the moment of writing, no successful solution of the trouble has been developed.  
          The fine machine work on individual valves is of interest, as evidencing the precision work which the German put into the individual components of the systems.  
     
 
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