Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore,


Thank you for the info...


One question


If during a dive and while on the surface, could you bring the diesel engines rpm down to 290, and at the same time fire up the e-motor to the maximum at 290 rpm, then could the main clutch be disengaged with out any friction or burning issues, or would there be a problem with mechanically disengaging a clutch while running (centrifugal force issues)? Perhaps the diesel engine would have a problem with suddenly no load? I guess that may kill that idea...


Just a thought...


Regards,
Don_

[tore]

Don.
Disengaging the engine clutch did not create a problem with regard to the heating of the friction lining of the double cone mainclutch, but a sudden loss of load could be hard on the governor of the dieselengine and would probably need an engineer at the fuelhandle. I Guess such crash diving action was taken when attacked by plane during diesel surfacecruising. The real problem with switching in and out rotating masses on the shafting is the torsional vibrations creating very large stresses in the shaftings which might break crankshaft as well as propellershaft. The primary part of the mainclutch ( attached to the dieselengine) act as a flywheel running disconnected at normal load, but when you switch in the e-motor/generators and  disengaging the propeller, you introduce a different torsional vibration scenario, which again is changed  switcing in the propeller shaft ( propeller) and for a GW engine connecting the Roots blower at high outputs.
In the earliy stage before you calculated the torsinal vibration stresses in the shafting quite a few broken propellershfts and crankshaft occurred. This resulted in a thorough calulation and an installation of a torsional vibration damper on the front of the crankshaft " chopping " up the worst vibrations.
Tore

[Don Prince]

Hello Mr. Tore,


Thank you for the last posting...


I have updated the following pages:


Prologue - pages XVI and XVIII - concerning the diving and surfacing sequence
Pages 108 - 109 - concerning the buoyancy tanks
Page - 414 - concerning an emergency/crash dive sequence


When you have time, would you please review and correct any problems?


At this point, I believe Skizzenbuch is in the final stage of being complete; unless, something comes up that is wrong and needs to be corrected. Everything I have added has been by making page lay-out changes and I haven't been adding any pages for several months because I don't want to have to re-index the entire book again. However, If something needs to be corrected, then I will do what ever is necessary.


I have uploaded the latest version of Skizzenbuch into my Dropbox account folder...


Regards,
Don_

[tore]

Don.
I have scanned your new skizzenbuch only and shall revert if any remarks. I think your Skizzenbuch is a never ending project as you go into more and more details, hopefully it would be more interesting for the reader. I am busy with the Junker exhaust and I have a few new inputs coming up in a few days I hope. I don`t like our present "solution" very much, so I assume your text has to be revised.
Tore

[Don Prince]

Hello Mr. Tore,


OK...  The only thing that must be considered with the Junkers internal exhaust valve mounted on the upper pressure hull is that it has to rotate the bottom external shaft segment and drive shaft extends to the upper segment which drives and intermediate segment (the interlock).  Also, it close/open the the grinding valve plate and position the intermediate segment so the lever may be enabled to lock or is disabled.  All of which must be accomplished by turning one hand-wheel...


That gearing ratio system was the only thing that I could come up with that would fit within the constraints of the outer casing.  Also, what does that 90 degree lever actually control when rotated or locked-out?


Kind Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Is the Skizzenbuch 12-5-2017 PDF File that you uploaded to dropbox the file that you were going to modify?


Regards,
Don_

[tore]

Don.
I am sorry not being able to give you a quick answer on the Junker exhaustsystem, the reason being I am utterly confused as I can not remember the stern buoyancy venting system with interlocks  launched as a possible system for the venting of the stern buoyancy tank and exhaust valve of the Junker. I am afraid I have to switch to another assumption. In Bremerhaven is a  museum submarine of type XXI laying alonside afloat I have in fact seen it several times but not being onboard. This submarine was commissioned just at the end of the war and was never on war patrol. She was scuttled at the surrender but raised and recommissioned by the Bundesmarine in 1960 when Germany became a member of NATO and became the mother of the future modern submarines of the german navy as well as the Norwegian navy. Willem Bauer ex U 2540 was serving in the German Bundesnavy till 1980. Long story short, I stumbled over a photo of what looked exactly like our "Junker exhaustvalve and buoyancy ventingvalve" fitted aft in this XXI boat. To my astonishment the test stamping on the housing was in English and checking further I registered  this was an English design of a Bold ejector. My therory is that Nato has a standard type of decoy cannister used by Nato long after my time and the ejector was installed in U 995 after my time as a NATO standarization. Sorry I guess it is back to the drawingboard.
Tore

[Don Prince]

Hello Mr. Tore,


I don't believe that device is not a Bold device... It is an exhaust valve for the Junkers compressor.  I believe you can clearly see the exhaust pipe in the upper right corner. I have a Type XXI schematic print that shows 2 junkers compressors located in the aft area of section 3 where the 2 - 6 cylinder diesel engines are located. I will post copies of the Type XXI schematics later. Also, I see dates stamped in the one area that look to be 11 8 43, and tested to 1000 lbs???  I believe the current Type XXI has only 1 junkers and 1 battery powered compressor.


Regards,
Don_

[SnakeDoc]

Hi Gentlemen,


Tore, great spotting. I like your theory very much.


Don, according to US Navy Report on type XXI U-Boat, this vessel was equipped with:
two Junkers compressors located in the aft part of the diesel engine room;
one electric compressor located in the pump room under the control room.


The "exhaust valve" visible on the photos provided by Tore is located in the aft room, on stb side:
https://www.flickr.com/photos/clemensv/9447842743/


I don't think that Germans led the exhaust duct from diesel engine room, through electric motor room, to the aft room.


I have attached photo of the original bold ejector installed in aft room (at stb side) of U 2518.
I think that post-war version of the ejector (as Tore suggested, of NATO standards) was installed in place of it.
It could be used as bold ejector as well as signaling flares ejector.


The question is, why Norwegians did not remove the Junkers compressor, when they decided to put the bold/flares ejector in place of the exhaust valve?


Generally, such post-war ejectors were called (at least in RN) Submerged Signal Ejectors.
Here you can find description of three types of ejectors: MK 2, MK 4 and MK 7:
https://maritime.org/doc/oberon/weapons/part2.htm
In my opinion, S.S.E. MK 4 is slightly similar to the arrangement found in aft room of U995 and U 2540.


At the bottom of the page, you will find some drawings of the "items" ejected from this device.


--
Regards
Maciek

[Don Prince]

Hi Maciek,

Nice photo of the Type XXI's original "BOLD Device"...

OK.. I assumed wrong when I seen a photo of the e-compressor in the Type XXI. Now, I believe the current Wilhelm Bauer should have 3 air compressors; 2 Junkers and 1 electric. (see attached image 3372a)

I also don't believe the Germans ran the Junkers exhaust from the diesel room to the aft room because that makes no sense.

However, the photo c4834_o (attached) from the Wilhelm Bauer shows a Junkers exhaust valve in the aft section, in place of the original Bold ejector (your photo).  That looks to be dead wrong!


I believe that I understand everything you posted except the following:

"The question is, why Norwegians did not remove the Junkers compressor, when they decided to put the bold/flares ejector in place of the exhaust valve?"

At the beginning of your post you state that Tore's photo is of the exhaust valve (I think so).

1. The current bold ejector on U-995 above the Junkers compressor looks to be correct, and it matches up with the outer hull casing. Is this correct?

2. The current exhaust valve in the upper pressure hull looks to be original in U-995, but the junkers exhaust pipe was cut off. So we don't see the exhaust pipe to the water separator or the exhaust pipe from the separator Which should go to an exhaust hull valve (I think). Is this correct?


Regards,
Don_

[Don Prince]

Type XXI Image


Don_

[SnakeDoc]

Hi Don,

However, the photo c4834_o (attached) from the Wilhelm Bauer shows a Junkers exhaust valve in the aft section, in place of the original Bold ejector (your photo).  That looks to be dead wrong!

No, I think (the same as Tore) that it is not a exhaust valve. In my opinion this is post-war ejector of bold/flares, installed in place of the war-time bold ejector.

What would be the reason to install the exhaust valve in the aft compartment, with no exhaust duct (from Junkers compressors in Diesel engine room) connected?

I believe that I understand everything you posted except the following:

"The question is, why Norwegians did not remove the Junkers compressor, when they decided to put the bold/flares ejector in place of the exhaust valve?"

At the beginning of your post you state that Tore's photo is of the exhaust valve (I think so).

In my post I put the exhaust valve in quotation marks, to indicate that this item (supposed to be a exhaust valve before) should be explained in different way.
I'm sorry, if it was not clear enough.

1. The current bold ejector on U-995 above the Junkers compressor looks to be correct, and it matches up with the outer hull casing. Is this correct?

Right. The question if this is original, war-time ejector or was it altered after war too.

2. The current exhaust valve in the upper pressure hull looks to be original in U-995, but the junkers exhaust pipe was cut off. So we don't see the exhaust pipe to the water separator or the exhaust pipe from the separator Which should go to an exhaust hull valve (I think). Is this correct?

I state, that in U 955, in the upper pressure hull is post-war bold/signal ejector (submerged signal ejector). It was installed in place of the Junkers compressor exhaust valve. So the exhaust pipe from the compressor had to be removed (as well as water separator).
My question was, why they did not removed Junkers compressor also. Without exhaust valve, exhaust pipe and water separator, the compressor was useless.


--
Regards
Maciek

[Don Prince]

Hello Maciek,


Let's tackle this issue one item at a time...


First - the original German Bold ejector is mounter on the pressure hull above the Junkers compressor, and it aligns with the external slot in the external hull casing. There is a hinge on the Bold so that when the ejector is opened internally an new cartridge may be inserted.


In back of the junkers compressor is the water separator which is the exact same separator that you Identified in the U-570 photo.


See image


Regards,
Don_

[SnakeDoc]

Hi Don,

First - the original German Bold ejector is mounter on the pressure hull above the Junkers compressor, and it aligns with the external slot in the external hull casing. There is a hinge on the Bold so that when the ejector is opened internally an new cartridge may be inserted.

Right, however I'm not 100% if it is original German design, or was it altered by Norwegians after war (the design is quite different than ejector from U 2518).

In back of the junkers compressor is the water separator which is the exact same separator that you Identified in the U-570 photo.

No, the marked item is not the same separator as on U 570 photo. This is water separator of the hp air system, see the drawing.


You can trace the line going to Junkers compressor (the last fragment missing) as well the line going to the electric compressor). It is also possible to trace the connection to the hp line (with strainer attached).


--
Regards
Maciek

[Don Prince]

Hi Maciek,


We do have a water separator on the exhaust...


Regards,
Don_