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Old 08-29-16, 01:56 PM   #108
Aktungbby
Gefallen Engel U-666
 
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Default A delicate business

Quote:
Originally Posted by Catfish View Post
@ Elanaiba,
have found a photo with a crewmember actuating the clutch for coupling the electric engines to the propshaft, but it's pretty bad (it is from one of Buchheim's three photo books). It is a simple hand wheel..
[QUOTE]A chief mechanician prisoner, claiming expert knowledge of Diesels, gave the following explanation of the term "Diesel-Electric." "Diesel-Electric" propulsion is used, when it is desired to put one Diesel out of action for repairs or other reasons, and it is nevertheless required to turn both screws. The electric motors are dual-purpose motors. They can be used either as dynamos or as generators as required. The switching over from one use to the other is done by means of a switchboard and a series of resistances. The whole procedure takes but a few seconds. If it is required, for example, to stop the port Diesel and keep under way on the other Diesel, the starboard generator is started from the batteries. The compression cocks of the starboard Diesel are opened, the generator slowed down and the clutch slowly let in, thus turning the Diesel engine. The cocks are then shut and the Diesel will run under its own power. The dynamo is then switched off and the speed of the Diesel increased so that the starboard generator produces enough electricity to drive the port dynamo. The electricity produced is led through the batteries to prevent the current fluctuating. The following table, found among captured documents, would therefore, indicate that if one Diesel is turning at 285 revs. at slow speed and the electric motor is coupled with it, the number of revs. is reduced to 240; the electricity produced is sufficient to turn the other screw at 155 revs. The loss in revolutions is due to the loss of power in the process of conversion. The differences in speed between port and starboard propellers is counteracted by the rudder. http://www.uboatarchive.net/U-570/U-570INT.htm Below is revs differential 'twixt diesel and electric 'clutched' revs:
.
Revs.
Speed in Knots.
Revs.
Speed in Knots.
Speed in Knots.
Diesel Revs.
Electric Motors Revs.
Slow
285
10
114
3
7.5
240
155
Half Speed
350
12
167
4.5
9
285
195
Three-fifth speed
390
14
220
6
10
330
215
Four-fifth speed
460
16.5
275
7.5
11
360
240
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