Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.
On page 140 you have a photo of the U 995`s GW engine. On page 141 you say: " The MAN engine looks to be the new diesel engine generation...."  It could be misunderstood as you are referring to the photo of the GW engine.
Starting procedure.
You have a description, possibly mine, of the general starting procedure on page 135 . On page 101 you are referring to a startingprocedure after surfacing, possibly mine, particularly mentioning air blowing of the cylinders prior to starting to prevent waterstroke. I would suggest you include the latter in the description on page 135 because you blew the cylinders after a long stop as well not only after surfacing and particularly after schnorchling. You would always be sure the cylinder were clean and free from water as you could have an ordinary coolingwater leakage into the cylinder as well.
Tore

[tore]

Don.
Skizzenbuch group exhaustvalve.
 On page 97 you are using one of my bad rough sketches to illustrate the group exhaustvalve casing passing the pressurehull and the grinding of the outer (muffler) flapvalve. This sketch might give a confusing image as it is a sideview of the aft/forward outboard system connected to a sideview of an at wartship inside system. May be you should indicate a line were the outer alongship pipe is turned 90 degrees to the aft as I have tried to indicate below.
Tore

[Don Prince]

Hello Mr. Tore,


The Black and White photo was supposed to be a MAN Diesel Engine...  Note the control levers are of the MAN design.  That is the first difference I see between a GW and a MAN design.  Am I wrong on that photo?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


The outer flap valve - what drove the gear shaft to raise the plate? Was this manual or part of the pneumatic drive?


I know the inner flap valve rotational drive was manual and I assume the raising of the plate was manual as well?


Regards,
Don_

[tore]

Don.
The black and white photo is taken on board U 995 as a museumboat during the last 10 years and is showing the GW engines with a few minor modification since my time on board. The starboard engine has a new type of fuel filter, the port the original. The flooring is the museumversion having  modern floorcoverings, not original. The MAN engine is entirely different. The most significant apart from the maneuvering stand is the turbocharger in the aft end, having double inlet airducts on the inboard side from the turbocharger and the double exhaust pipes to the turbocharger on the outboard side. GW engines have common airduct directly underneath the exhaust manifold on the outboard side and the exhaust goes directly overboard as the engine has a mechanical driven Roots blower. Crankcase doors on MAN are round on the GW square. Lp fuel supplypump is on the aft end on MAN and in the forward end on the GW, so I am afraid somebody told you the wrong story.
Tore

[SnakeDoc]

Hi Gentlemen,

both engines - MAN and GW were designed before war, so one can not say, that MAN engine was new generation.
Moreover, one can wonder, why Kriegsmarine chose GW engine as the primary propelling unit for type VII U-Boats
(MAN engines were installed less frequently) - especially knowing, that MAN engine was lighter and had lower
fuel consumption. The answer is that MAN engines (in the 9-cylinder version) were manufactured for type IX U-Boats,
while the other factories manufactured GW engines for type VII boats.

The photos of the MAN engines can be found here:
http://u-historia.com/uhistoria/tecnico/articulos/motores/motores.htm

--
Regards
Maciek

[tore]

Don.
The outer flapvalve was manually shut by a handwheel,external rods and bevelgear. The inner valve was manually operated by the same type of handwheel as well. Both wheels have holes in the  wheel circle for putting in a bar thus being able to get extra torque moment for shutting. see my picture below.

[Don Prince]

Thank you Mr. Tore,


Again, I will make the appropriate changes...  I am very surprised that U-995 had two very different control levers units on the what I assume to be the original GW Diesel Engines.  That sure confused me!


Does anybody have a good high resolution isle photo of two MAN Diesel Engines in a Type VII U-boat?  I sure don't, and I don't see one on the web so far...


Regards,
Don_

[tore]

Don.
I don`t have a high resolution photo but below you see the significant difference of the maneuvering stands of the two engine types, although the MAN engine of the U 166 being a IXC  from 1940- 1941 and as such having the 9 cylinder direct reversible execution, the maneuvering stand was the same as a direct reversible 6 cylinder MAN. The MAN engine was equipped with a turbocharging system which means utilizing the kinetic and thermal energy in the exhaustgases to drive an exhaust gas turbine attached to a rotary compressor in the aft end, this system could be used over the whole output range. Although the system had been known for years, the practical use was not common in the latter part of 1930, primarily because the efficiency is depending upon fairly high temperatures which was limited by the material heat resistance of the turbine blades which at that time was a material challenge. The GW engine technique was more conventional technique of the 30this with a Roots blower which only could be used at higher output and thus required a complicated system of clutches and interlocks. Moreover the specific fuelconsumption was higher on the GW engine letting the residue exhaustgas energy disappear directly overboard.
Tore

[tore]

Don,
A high resolution photo of the MAN 6 cylinder engine is hard to find, below is the best image I found showing a 6 cylinder MAN M6V 40/46KBB.
Tore

[Don Prince]

Hello Mr. Tore,


Does this look like a MAN Diesel room on a VIIC?


Regards,
Don_

[tore]

Don.
It is very little engine and much of the crew on the photo, but the crew is very high up head above the engine top and it is very narrow between the engines which could indicate small engines. If you look at the framing it indicates a small hull as well. I guess this could be one of the older small submarines like  type IIB, however these submarines had MWM RS 127S 6 cyl. engines and it does not look like a MWM.
I don`t think it is a MAN 40/46 as the airduct along the engine is round and not rectangular moreover there are some internal gatevalves up under the pressurehull which does not exist on a VIIC. My guess would be: not a MAN engine and not a VIIC, possibly a smaller coastal submarine.
Tore

[tore]

Don
I was able to find a more comprehensive photo of the engine assumed by you was the MAN mainengine alternative of the VIIC engine. The MAN submarine engine underwent a number of design developments from the early natural aspirated engine ,I believe in the late 1920this, via a mechanical supercharged version, to a Buchi turbo charged version in the 1930this and to the last turbocharged,intercooled high performing version having an output for a 6 cylinder version of 2000 bhp at 520 rpm. Really an advanced modern engine I believe introduced in 1944.
I  do not think this last version of the MAN engine was used in a VIIC as 2000 bhp at 520 rpm would require  quite a few alterations in both the Emotors, shafting and propellers etc.
However I guess the engine was developed for the new "Electroboats" class XXI all equipped with MAN 6 cylinder M6V 40/46 KBB being the last type of the WW2 MAN submarine engine.
Below I have a picture explaining why I assume your picture is from a XXI boat. The people are standing on a footstep attached to the engine (on the GW engine is a similar footstep which can be folded in) which fooled me to believe it was a smaller boat. Even if the airduct from the turbocharger and intercooler is not rounded as on the picture of the MAN M6V 40/46 KBB, I believe there are so many components similar to a MAN engine which justifies my conclusion the engine is a MAN M6V 40/46 KBB in a XXI boat of which I have no knowledge.
Tore

[tore]

Don.
Further to my todays post. Do not to use the photo of the MAN 6V 40/46 KBB,  if not any better, may be my photo of the  IXC 9 cylinder MAN M9V 40/46 as I can`t find a good photo of a 6 cylinder.
Tore

[Capt Kremin]

Hi tore, Don et al
 
Is this photo any good to you it is from the MAN museum where they have/had this engine on display,
 
Regards
Jon