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Appendix G

U-Boat History, Development & Equipment, 1914 to 1945

by David Miller


All four Stroke, two stroke considered but not applied in WWII

The diesels had to be modified to run with the Schnorchel: the MAN M9V in the IXC-40, for example was fitted with special camshafts with a 'normal' position giving an exhaust pressure of 0.1 atmospheres and a Schnorchel position ,with a pressure 0.4-0.45 atmospheres.

Early experiments on two type U-57-U58 involved removing a periscope and replacing it with the Schnorchel tubes. This was followed by modified tubes in Type VII U-235-U236 in Sept 1943.

German exhaust discharge techniques were different to the simple underwater outlet adopted by the Royal Navy. British ASW experience had showed that the submarine could be detected by observation of the exhaust gases, while the Germans persisted in thinking this was not so.

The Germans developed two versions of the all important air induction tube head valve, the first a simple ball float and later a ring float. Both these methods were adopted by the Royal Navy, first the ball and later the ring float. Miller reports that an electro-pneumatic head valve was produced but then adds a footnote that this type of valve was still under development when the war ended.

As in the Royal Navy, the induction float valve fell open when lowered allowing the mast tube to flood. Apparently the ring float had a vent valve that opened at 30 m



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Appendix F