David,
Here is a little information that I have. I don't know if this will answer your question but here goes.

The machinery plant on the Type 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 the two shafts and a battery of 124 cells. The submarine has a crusing 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 asscciated fuel, lub oil, and circulating water systems are much simpler than corresponding U.S. systems and much additiional reliance is placed on operating personnel to insure their proper operation.

Inroduction:

The propulsion arrangement on the type IXC submarines is similar to that of its predecessor, the smaller type VII-C. However, the machinery layout has been designed to provide an increase in surface speed and cruising range at no sacrifice to submerged characteristic.

General Description:

The propulsion charactistics on the type IXC vessel are closer to those of present U.S. (World War II) designs than thse of any other German type. The comparative characterstics are listed in the following:

Max surface speed: IXC - 19. U.S. Sub - 20.25
Submerged speed: IXC 7. U.S. Sub - 8.75
Normal battery charging time: IXC - 7hrs. U.S. Sub - 7hrs
Max speed while charging at normal rate: IXC 13.5kts U.S. Sub - 14kts

The direct drive arrangement has a 2170 HP nine cylinder MAN diesel engine cooupled 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 of furnish, at the one hour discahrge 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 power propulsion plant are at a minimum for this small vessel.

The associated serving systems are, for the most part, of comparatively simple designe and have been proivded 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 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 iin 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 the system.

Some consideration has been given to possible casualties to the sytems arasing 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 shockmounted on rubber mounts. However, no special attempt has been made to keep fuel lines outside of the ballast tanks or compensating water piping water piping between tanks within the pressure hull.

Main and Deisel Coupling:

Standard cone type fraction coupling aare used. To provid the quick operation necessary for uncoupling of the deisel from the main shaft a combined pneumatic hydraulic setup is employed. This consists of a hydraulic piston and cylinder operating in conjunction with an air on oil cylinder, a common German praactic. Hand operation is also provided for emergnecy use. The main coupling is operated by a hand crank arrangement. Both of the units are designed to function at a maximum torque of 94,000 lbs. ft., equivalent to 25% overload. Operating instructions state that the clutches should not be engaged when turing the shaft above 350 RPM. They may be disengaged at any RPM.

Conclusions:

The IXC propulsion arrangement is consider a satisfactory compromise to obtain the desired propulsion characterstic in such a small "fleet" submarine.

The circulating water, lub oil and fuel oil systems are, in general, considered much inferior in design to the corresponding system on U.S. submarines.

This will make more questions than it answers.

Scott