The machinery plant on the IXC has been designed to provide a maximum sustained surface speed of 19 knots and a submerged speed of 7.5 knots at the one hour rate.  This has been accomplished with a direct drive arrangement of a diesel engine and main motor on each of two shafts and a battery of 124 cells.  The submarine has a cruising radius of 16,800 nautical miles at 10 knots.  
          The machinery arrangement does not provide the flexibility of operation equal to that on U.S. submarines.  The units installed, however, give the vessel similar speed and range characteristics under varying submerged and surface conditions.  The associated fuel, lub oil and circulating water systems are much simpler than corresponding U.S. systems and much additional reliance is placed on operating personnel to insure their proper operation.  
July, 1946
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  1.  Introduction  
          The propulsion arrangement on the type IXC German submarines is similar to that of its predecessor, the smaller VII-C.  However, the machinery layout has been designed to provide an increase in surface speed and cruising range at no sacrifice to submerged characteristics.  
  2.  General Description  
          The propulsion characteristics on the type IXC vessel are closer to those of present U.S. designs than those of any other German type.  The comparative characteristics are listed in following table:  
Late U.S. Submarines
Max. surface speed
Submerged speed  
Cruising range (surface)
      "         "     (submerged)
Normal battery charging time
7 hrs.
7 hrs.
Max. speed while charging
13.5 kts.
14 kts.
    at normal rate
(1 shaft)
          The direct drive arrangement has a 2170 HP nine-cylinder MAN diesel engine coupled to the main motor and to the shaft through appropriate clutches.  Each main motor when operating as a motor has a rating of 493 HP and when operating as a generator can develop 710 HP.  The two batteries, of 62 cells each, have the capacity to furnish, at the one hour discharge rate, the rated motor horsepower to the two main motors.  
          The limitations that have been found to exist with a direct drive set-up on former S-boats apply as well to the German arrangement.  However, it is believed that a well balanced power plant for both surface and submerged propulsion is provided and that the space and weight requirements of the comparatively high powered propulsion plant are at a minimum for this small vessel.  
          The associated servicing systems are, for the most part, of comparatively simple design and have been provided with a minimum of standby facilities.  Some added flexibility has been gained, however, by the practice of providing standby and emergency service through numerous portable hose connections on the various systems.  
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  and by the design of piping systems to permit use of several of the pumps on more than one system.  The lub oil system is simplified in that all units within the maneuvering room utilize gravity lubrication.  The circulating water system is also simplified in that salt water cooling is used throughout; there are, however, numerous places within the system wherein salt water leaks can cause serious casualties.  The fuel oil system employs the simplified gravity feed tank arrangement formerly used on U.S. vessels.  The lack of means for adequate oil purification is a weakness in this system.  
          Some consideration has been given to possible casualties to the systems arising during depth charge.  All hull valves have inboard back-up valves; these valves and interconnected piping are tested at 2-1/2 times designed submergence pressure.  Many of the system units have been shock mounted on rubber mounts.  However, no special attempt has been made to keep fuel lines outside of the ballast tanks or compensating water piping between tanks within the pressure hull.  
  3.  Conclusions  
          The IXC propulsion arrangement is considered a satisfactory compromise to obtain the desired propulsion characteristics in such a small "fleet" submarine.  The layout, however, is conventional in nature and offers little that is new for discussion.  
          The circulating water, lub oil and fuel oil systems are, in general, considered much inferior in design to the corresponding systems on U.S. vessels.  Only isolated details of the system are of interest.  
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