Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.
Kya`s  ex. U 926 structual damage. 12 Storage containers seems a lot, we had only 3 when I was onboard. I am a bit confused as to HP blowing of the storage container as you know the containers are not equipped with any HP airconnection and are simply a pressureproof container with lid like the ammocontainers. Anyhow Boyle Mariottes low is valid and Storage containers might be a confusion with the HP air flasks or airbottles as we say. 205 bar with an expansion to 10-25 bar makes a considerable volume increase, but a detail which is forgotten is the temperature drop according to Boyle Mariottes P1xV1/T1=P2xV2/T2. Such a temperaturdrop during a long blowingtime might cause freezing of  the blowing valve which is one of the reasons the main blowing panel in the controlroom has an emergency blowing valve shortcutting the main blowing valve in case of freezing.
Back to U 226 and the structural damage. it is a long story which I might revert to if any interest, but the conclusion was, in late April/ early May grossadmiral Dønitz ordered all the operational uboats to Norwegian ports as Norway was going to be the center for the German submarine high command for the last desperate fight. More than 100 boats arrived causing a capacity problem at the surrender and the Allied forces decided  to remove these boats to Scotland sailing the boats by the german crew. The operation was named Pledge, and a Norwegian naval submarine delegation took part in an investigation as to which Uboats were fit for the crossing to Scotland. I guess all but 11 were fit and amongst those 11 were , the U-995, U-926 and U 1202 which later were reconditioned and operated by the Royal Norwegian navy. The whole story is long and last year I wrote an article on the event in the main newspaper in Oslo, I have translated same to English.
Tore

[tore]

Simon.
It`s a delight to see you are back with you amazing drawings, as many times we have to improvise and assume as no reliable images exist. I am still in doubt of the selector valve, not the position outside the tank. The selectorvalve is a double seated valve and we have such a selector valve in the trimsystem placed in the controlroom. It might be this valve is closer to the prevously indicated.
Tore

[NZSnowman]

Hi All

Yesterday I think I found the valve and piping on U-534.

[Don Prince]

Hi Simon,


Those photos seem to verify that the selector valve was below the deck... Great investigation and find!  It's amazing that some of the tanks internal surfaces are not rusted like the internal pressure hull. Perhaps they stayed in tact and were not flooded after all those years at the bottom of the sea.

Hmmm... I just noticed that the kingstons are shut.  That would mean they were in a fuel oil storage configuration.  That could account for the better condition of the tank's internals.

Mr. Tore,


Just for my own personal knowledge, what is the difference between a selector valve, a sealed selector valve, and a double sealed selector valve?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


I made the suggested changes to pages 82 and 83 and uploaded the Skizzenbuch update to dropbox.  Thank you for reviewing the text...


Regards,
Don_

[tore]

Don.
A double seated valve is probably not a precise name as f.i. a gatevalve can be double seated using both side of the "gate". However in this specific case of a compensator selector valve it means a valve having two seatings which can only be put in either-or position. The image below is a double seated valve having one inlet and two outlet. For smaller pipes such a "valve" would be a three way cock, in the case of the valve below, the valve has to be operated to the end stops, up or down like the selector trimvalve in the controlroom shown below. I don`t think there is any mentioning of a double sealed valve in this connection, I guess this might be a misunderstanding.
Tore

[Don Prince]

Hello Mr. Tore,


What is this lever for located near the GW Diesel engine on U-995?


Regards,
Don_

[tore]

Don.
As you know U 995 is equipped with Krupp Germaniawerft main engines. Contrary to the MAN engines the GW engines were only partly supercharged in the upper outputs by a mechanical driven Roots blower. The blower is driven from the camshaft assembly in the aft end of the main engine and switched in at a given output and revs by a doublecone clutch. The handle you refer to is the handle for same. Simultaneously to engaging the blower is the shutting of the natural aspirating air inlets for each cylinder in order to accommodate the common airduct for the supercharging air to the cylinders. This is done by rotating the natural aspirating inlet valves by the same handle. May be the image below is of some help.
Tore

[Don Prince]

Hello Mr. Tore,


It looks like there is no interlock for reversing since U-995's GW Diesel engine is non-reversing, and the handle is different from the drawing Plan 30 with the reversing interlock.


It looks as if the handle is down (Aspirater mode), and raised up (Supercharged mode) is that correct...


Regards,
Don_

[tore]

Don.
As you know the plate 30 as published is from the manual of U 570 later HMS Graph, comissioned in 1941, and as such shows the GW engine in a direct reversible execution. The later non reversible GW engines had most of the maneuvring gear removed and simplified so the plate 30 is not relevant to every detail for the U 995. I believe the lever for the roots blower was raised in an engaged position.
Tore

[NZSnowman]

Tore, I noted on the early Type VIIC's, there are small bass labels next to the deck hatches. Most likely identifying the hatches. Do you think they carried on this practice with the late war U-boat?

[NZSnowman]

Simon.
It`s a delight to see you are back with you amazing drawings, as many times we have to improvise and assume as no reliable images exist. I am still in doubt of the selector valve, not the position outside the tank. The selectorvalve is a double seated valve and we have such a selector valve in the trimsystem placed in the controlroom. It might be this valve is closer to the prevously indicated.
Tore

Hi Tore

Here are the new drawings of the Selector valve (Figure 1). I cannot get it to fix in the space available on the post side of the main ballast and reserve fuel oil tank 2

Looking that the pictures of U-534, my original Selector valve (Figure 2) looks more correct. I might leave the Selector valve till later, until we get better pictures or after I add the saddle tanks to my model, to see how much real space there is.

Simon


Fig. 1. New Selector valve. (Images has been resized. Click to view original image).


Fig. 1a. New Selector valve. (Images has been resized. Click to view original image).



Fig. 2. Original Selector valve. (Images has been resized. Click to view original image).



Fig. 2a. Original Selector valve. (Images has been resized. Click to view original image).

[tore]

Simon.
Your selector valve fig two is probably correct for an inboard fuelvalve but for an outboard valve your fig 1 would probably be better with a few modification. The stuffingbox should be a bit different. Below I have tried to indicate my idea. The threaded part of the valvespindle should be on the top of the spindle whereas the spindle should be without threads in the valvehousing where the packing materiel is located. I can not remember any brassplates for identification on the later VIICs, in the latter part of the war the Germans hardly used any brass.
Tore

[NZSnowman]

Tore, the hull valves ('h') for the low pressure exhaust gas for main ballast and reserve fuel oil tank 2 & 4 http://www.uboatarchive.net/U-570/U-570Plate16.htm

Which valve do you think is best figure 1 or 2?

Figure 1.

Figure 2.

[NZSnowman]

Simon.
Your selector valve fig two is probably correct for an inboard fuelvalve but for an outboard valve your fig 1 would probably be better with a few modification. The stuffingbox should be a bit different. Below I have tried to indicate my idea. The threaded part of the valvespindle should be on the top of the spindle whereas the spindle should be without threads in the valvehousing where the packing materiel is located. I can not remember any brassplates for identification on the later VIICs, in the latter part of the war the Germans hardly used any brass.
Tore

Hi Tore,

Thanks for the information on the stuffingbox, I have always wonder about this detail. Below is the updated drawing.


Image has been resized. Click to view original image.