Tores mailbox VIIC and VIIC/41 operation and technical details

[SnakeDoc]

Tore, thanks for the drawing. It looks, that this interlock also prevents flooding the stern buoyancy tank while the exhaust valve is opened.

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Regards
Maciek

[Don Prince]

Hello Mr. Tore and Maciek,


Wow!  It looks like one dumb question has generated a lot of good information...  By the way, over night while I was sleeping I remembered the large red hand-wheel was for venting the residual water in the saddle tanks (MBT2). 


Before I retired from NCR as a hardware and software support engineer...  If I had a problem that I could not solve during the day, then I would generally figure out the problem while taking a warm shower or while sleeping.  I guess after retirement my U-Boat hobby has replaced my NCR work load; the same thing is happening again.  This stuff is coming to me in the middle of the night again!!!


I guess we just can't stop old habits...


Regards,
Don_

[tore]

Don.
It is not the first time we have figured out the working details when you have no access to drawings or further information. In fact when I was on board many detailed drawing were not available, the advantage then was on board you could start crawling around even dismantle items to make sketches for your own skizzenbuch. I wish I had mine from those days today. It is remarkable little details in the manuals available about the exhaustsystem of the Junker and on the poor old U 995 they have made a hull entrance were the piping should be. We have not yet got all the details on the outboard exhaust piping included exhaustvalve which has many parts within the pressure hull, I think I have a vague idea and shall see if I can compose a sketch within some days. In the meantime may be somebody have some drawings or photos which might give us some details. Lets hope Simon is digging himshelf out of the snow and provide us with some info.
Tore

[Don Prince]

Hello Mr. Tore,


You mean it snows where Simon lives?  Just joking of course...  Can you provide some information as to how they grind the exhaust shutting valve on the Junkers exhaust system?


Do you have any idea as to why they moved the bow buoyancy control to the control room?  There are no open slots in the buoyancy tanks, so as air escapes the water would have to pour in if opened while submerged.  Or, they open the vent to initially pump water into the bow buoyancy tank and then close off the valve.  Then they can use the trim pump to balance the U-Boat while surfaced?  Or, during a periscope attack they want a bow down angle of 1 1/2 degrees; is this how that is accomplished?



Regards,
Don_

[tore]

Don.
I don`t know why they move the bow buoyancy tank venting to the controlroom, but I guess it is more convenient to have the controls in the controlroom. The buoyancy tanks have freeflood holes in the bottom, when you open the vents waterflows freely into the tanks while diving. If the vents are open in surface position the buoyancy is gone in rough sea pitching. The tanks are not used for trimming, when ventvalves are shut in surfaced position they simply gives additional buoyancy when the bow or stern goes under the surface when pitching. You can use any tanks for surface trimming but you avoid the use of the ballast tanks. Large, partly filled tanks have a bad effect on the submarine called free surface effect, that's one of the advantages of having watercompensated fueltanks. Bow down angle of 11/2 degrees is usually accomplished by using hydroplanes.
Tore

[Don Prince]

Hello Mr. Tore,


I'm assuming they did not move the blowing valves for the bow or stern buoyancy tanks in their respective torpedo rooms.  Do you have a photo of these blowing valves?


For example, Plate 12 shows LP air is used to blow/force the sea water out of the buoyancy tanks through the open slots in the bottom of the tanks.


At what level of seas was the commander required to abandon the topside watch for the enemy because of concerns for the safety of the crew in bad weather?  An Atlantic hurricane can generate winds way above 100 MPH and really huge waves...


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


I updated Skizzenbuch pages 90 and 91 with the info about the stern buoyancy tank lever and the interlock with the Junker exhaust valve..


Regards,
Don_

[tore]

Don.
LP blowing blowing of buoyancy tanks.  I don`t believe this blowing was very much used, in fact I can`t even remember them. Normally during  surfacing you left the vents open and the tanks drained nicely,I should guess in bad weather some COs would like to break the surface with ventvalves shut and then blow the tanks to to speed up the buoyancy effect. Unfortunately I cannot find any photos of the blowing valves.
The people at the bridge took a lot of beating as sometimes the sea could fill the bridge. I have experienced, particularly during the November storms, that we had to shut the conningtower hatch as we got too much water in the controlroom, once we had to navigate surfaced by the periscope and at the end we continued submerged at a depth of 50 meters. Even at that depth you could feel the swell. Thus you could have people at the bridge in quite bad weather conditions not only depending upon the wave hights, but your course  in relation to the direction of the wind and sea as well. Certainly for the Germans during WW2, not having air superiority, it was necessary to have people on the bridge under all circumstances.
Tore

[tore]

Don.
I checked your Skizzenbuch 3, OK although not yet complete on the Junker.
Tore

[tore]

Don
Junker outboard exhaustvalve.
I have looked through all my papers and cannot find any detail on the subject so I have to design the valve based on the photos available. Down below is my sketch which is an assumption/ partly shear guesswork.
The valve consist of a tube steelhousing going through the pressurehull ending in an outboard valve which connect the muffler ( sea) and the inlet ports of the Junker opposed piston dieselpart.  The valve has a free rotating valvedisc (red) and stem with a bore for the valve spindle ( yellow) on which the disc is free to rotate.
The other end of the valvespindle (yellow) has a threaded end engaging threads in the valve wheel hub (pink) which is kept in position by a rim disc in the housing. When turning the pink valvewheel the yellow valvespindle moves up and down shutting/opening the valve, the pink valve hub stays in place. As the red valvestem and disc is connected to the yellow spindle they follow the axial movement of the yellow valvespindle. At the other end of the red valve stem is a gearwheel having a hub with inside slots engaging similar slots on the red valve stem, the gearwheel is kept in place by the housing. Thus the valvestem is sliding axially in the gearwheel when the stem is axially moving by the handwheel turning.
 When the valve is shut and the sternbuoyancy tank vent is open, the Junker valve is locked by the interlock (violet) as a small cam keeps the red valvestem down (shut).
If you have to grind the valve, you shut the valve, a small shaft end protrude out of the casing as shown, and a bar is secured by a screw on this shaft and you turn same thereby rotating a worm which is engaged to the gearwheel on the red valvestem. As the gearwheel bore has slots engaging matcing slots in the red valvestem, the valvestem and valve rotates around the yellow valve spindle and you are grinding the discseat against the housing seats. The valve opens towards the seapressure and you cannot open the valve unless the sternbuoyancy tank vent is shut.
An airpipe (green)is connected to the outboard valve housing which makes it possible to blow the exhaustpipe to the sea while the exhaustpipe is shut to the Junker cleaning the exhaustpipe for water prior to opening of the valve.
I should assume it is an additional hull exhaustvalve as usual. PHU!! Confusing? read it once more and look at the sketch
Tore

[Don Prince]

Hello Mr. Tore,


I cut a segment from the aft torpedo room showing the Junker's exhaust valve...  Does it look like all three components are very close to the sale horizontal line?


Regards,
Don_

[Don Prince]

Hello Mr. Tore and Maciek,


I uploaded the latest version of Skizzenbuch to dropbox.  Page 345 contains info on Group Listening Devices (GHG, Balkon, and KDB), I also added exterior photos of Bold (Note* without the bird crap on the side and the spikes on the upper deck edge of the U-Boat.  I edited the photos!)...


Regards,
Don_ 

[tore]

Don..
When reading the page 345 I came over the photo of U 995 hanging in the big crane in Kiel at the time being converted into a museumboat page 344. At that point she had a Balkongeraet and your text  on the photo says : " showing KNM Kaura pennant no. 309 (ex. U 995) in its original configuration".
She never had the balkongeraet in my time I guess this was possibly installed at a later stage may be when she was a training/ research boat. Thus in her original configuration she was without the Balkongeraet.
Tore

[SnakeDoc]

Hi Gentlemen,

LP blowing blowing of buoyancy tanks.  I don`t believe this blowing was very much used, in fact I can`t even remember them. Normally during  surfacing you left the vents open and the tanks drained nicely,I should guess in bad weather some COs would like to break the surface with ventvalves shut and then blow the tanks to to speed up the buoyancy effect. Unfortunately I cannot find any photos of the blowing valves.

The location of the low pressure compressed air valves for blowing (bow) buoyancy tank also suggests, that blowing was used rarely.
I have attached the photo of the hull blowing valve of bow buoyancy tank - it is located 78th and 79th pressure hull (internal) frame,
over the upper, port torpedo tube - quite inconvenient place for operation.
I have also marked the valves on the aft (port side) bulkhead of the forward torpedo room. There is also one more valve on blowing
line - comparing these two photos, you can see, that it is also inconveniently located.

I was unable to locate the hull valve for blowing the MBT5, but I have attached photo presenting the MTB1 hull valve.

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Regards
Maciek

[Don Prince]

Hi Maciek.


To make sure I understand the photos...


1. The photo with all the red arrows pointing to LP valves that lead to blowing the bow buoyancy tank.   Which valve would they use to blow the bow buoyancy tank, the hull valve, or the one down stream? Where are these valves in relation to the forward torpedo tubes?


2. The green hand-wheel is HP air and what is its purpose?


3. The photo is of the aft torpedo tube with the hull valve for MBT1 buried so deeply; am I correct?


I would imagine the hull valve for MBT5 is similarly buried in the forward torpedo room section as well. 


OK...  I have the following


1 - MBT1 and MBT5 venting valve hand-wheels in the control room
2 - The hand lever for venting the stern buoyancy tank in the aft torpedo room (VIIC/41)
3 - The hand-wheel for venting the bow buoyancy tank in the control room (VIIC/41)
4 - The info just provided about blowing the bow buoyancy tank in the forward torpedo room


I don't have info/photo of the blowing valve for the stern Buoyancy tank in the aft torpedo room...


Regards,
Don_