Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Mark the 3rd sightglass is the inclinator eg. the instrument for measuring forward/ aft trim like diving angle and it work as per image below.
Tore

[VIC20]

Thanks Tore and Don, so the 3rd one of the two inclinators is identical to the one in U 995 (which comes with only one inclinator) right? The other Type VII you served on, did she had one or two inclinator gauges?


How did the mechanical hydroplane indicator displayed the angle? I don't see a gauge needle on any of the pictures. Did the mechanical hydroplane indicators always work or only when the manual wheels were used (instead of the electric motors)?


Which raises another question, the manual wheels could be decoupled right? Or did they always rotate simultaneously when a button was pressed on the electrical "BBC" controller?

The only thing that seems to be a mystery to me is what exactly is the function of the index pointer that slides up and down on the rod on the right side of the Papenberg meter scale?

I can only guess but I believe it is a marker which can be set to quickly mark a desired depth. I think this would be useful if the attack periscope is in use. The usable height of the observation periscope was very limited (operators must bend themselves if they want to lower it). So when the observation periscope was in use then the desired depth (to keep the head just low above the surface) was basically always the same. But the attack periscope was usable at almost any extension (at least this is what I understand from the description in Harry Schlemmer's book "Vom Turmsehrohr zum Optronikmast"), hence the "periscope depth" of the boat and the extension of the attack periscope could vary which makes a quick marker useful. But this is just my first thought and I bet I am totally wrong 


Something different that I absolutely don't understand:
The head of older versions of the C/2 attack periscope (till 1942) were pressure proof up to 15 bar only (equal to approx. 150m) later ones up to 25 bar (250m). I think even with a fully retracted periscope the head was still visible and had no additional protection (or is that wrong?). This would mean the older boats could dive to a maximum depth of 150 meters only because above that they would risk an ingress of water through the periscope.

[Don Prince]

Hi  Mark,


I will eventually get everyone's name right...  I found a photo that shows a lid placed over the tube casing of the aerial periscope.  I can't explain why, because if the lid is left on and they come up from a deep dive; do they just pop the lid off when they raise the periscope? Perhaps Mr. Tore has an explanation?


Perhaps the lid has a chain attached and they just pop it off the periscope tube casing when the aerial periscope is raised, and put it back in place after surfacing???


The attack periscope is located up in the tower and the captain is seated right in front of the eyepiece (no bending) the upper section of the attack periscope is what is raised and lowered..


Regards,
Don_

[tore]

Mark and Don.
On the U-995 and U-926 we used only one Papenberger as far as I can remember. It looks indeed on your image that it is a 2nd. Papenberger with somewhat larger glass for higher accuracy.
The manual operation of the hydroplanes was normally disconnected by a dogclutch situated locally next to the hydroplaneshaft, thus the wheels did not turn. You could connect the mechanical drive pneumatically from the hydroplane operators place, see my image, to reset same you had to do it locally though.
On my image below I have indicated the mechanical pointer of the teleflex system frrom U-570.

I am not sure where you got the pressureproof figures for the periscopes. 150 meters was the 1939-1942 testing pressure for the pressurehull plating. I should certainly think the periscopes could take more than that. Another thing is the operation of the periscopes. If you are going deep you lower the periscope to the endplates relieving the strains on the wires. However sometimes you let the boat hang on the periscopes when you need to go absolutely silent. You shut down the pumps and adjust the bouyancy by lowering and raising the scopes, ( changing displacement) using the stored energy in the hydraulic accumulators. It could be a limiting max.factor on these operations which is rather due to the wires than the scopes.
To my knowledge we never used any pressureproof caps on the periscopes.
Tore

[VIC20]

On my image below I have indicated the mechanical pointer of the teleflex system frrom U-570.

Thanks, I first thought this is a shadow.

I am not sure where you got the pressureproof figures for the periscopes.

From a book about German Zeiss Periscopes, written by Harry Schlemmer a physicist of the Zeiss AG.
http://www.koehler-mittler-shop.de/Programm-Koehler-15/Vom-Turmsehrohr-zum-Optronikmast-Schlemmer-88.html

However sometimes you let the boat hang on the periscopes when you need to go absolutely silent. You shut down the pumps and adjust the bouyancy by lowering and raising the scopes, ( changing displacement) using the stored energy in the hydraulic accumulators.

Wow, I need to add this to the simulation of the more complex 2nd title 

[Don Prince]

Hello Mr. Tore,
Hello Mr. Tore,

While reviewing page 340 and looking at the attached drawing of the threaded carriers to open and shut the Kingston Flap valves in MBT 3, I have come across an issue with the aft drive mechanism. the attached drawing does not provide enough detail about the threaded carriers that cause the Kingston Flap valves to swing open and shut while the threaded carrier moves up and down on the threaded drive shaft.  See my attached drawing. 

Do you have better drawings of these threaded carriers? Especially the aft carrier that only drives 1 Kingston Flap Valve...  My attached drawing seems to answer the issue where the threaded carriers and the attached drive rods have the ability to swing and follow the Kingston flap valve attachment point.  That point, besides moving down also moves to towards the keel.  See where I have marked the poor drawing with yellow circles of the drive rods swinging point. what I need is better details...

Regards,
Don_

PS - The drawing seems to indicate the threaded mechanism may be attached to the internal longitudinal bulkhead in MBT 3 at an angle - where the bottom of the screw drive shaft is further away from the bulkhead and that does make sense???

Does Simon have any drawings of MBT 3 internals?  I know he is great on details and always gets the mechanical stuff correct?

[tore]

Don.
Unfortunately I dont`have access to my paintprogramme but I believe the best image would be that of plan 28. The fixing points to the centerbulkhead would be the two endbearings. In beween these bearings is the threaded shaft located. The driveshaft up to the controlroom having two universial joints allows the shaft to operate under an angle rotating the threaded shaft between the two fixed bearings, The travelling nut ,in this case the yoke, moves up and down as the threaded shaft rotates and thus operates the kingstons. I suggest you use plate 28 as an illustration which is more correct than your  present image. I have tried to indicate what I mean on the  image below.
Tore

[Don Prince]

Hello Mr. Tore,


Thanks - I updated my drawing and will post it...


I have a few questions about MBT 3.  You stated MBT 3 was nice and clean with a fresh coat of zinc chromate paint and there was a man-hole in the internal longitudinal bulkhead...  How did you get inside of MBT 3?  Through an open Kingston valve?  If that were the case, then why the man-hole?


Regards,
Don_

[tore]

Don.
As far as I vaguely remember we were able to squeeze in via the Kingston openings, may be the Kingstons were dismantled. This was some 65 years back and I was at that time a very skinny guy.
I see for some reason you want to have the threaded shaft and travelling nut on the aft Kingstons placed in an angle, I don`t see the reason for that, I believe the threaded shaft and bearings are vertically fitted and the driveshafts having universal joints have an angle.
Tore

[Don Prince]

Hello Mr. Tore,


OK, what you remember is good enough for me...  I will work on the drawing.  (Done)...


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Sometimes I think too much and forget some of the many lessons you have taught me...


any way...


MBT 3 has 6 Kingston valves normally open so the U-Boat can dive... Right? Why on earth would they ever want to close them?  If on a war patrol with closed Kingston's they can't dive, so they may as well run up a white flag because they can't out gun a destroyer and they would be ducks in a pond for aircraft?


I certainly am missing something... I did think of one thing...  make it a museum U-Boat!


Regards,
Don_

[SnakeDoc]

Hi Don,

MBT 3 has 6 Kingston valves normally open so the U-Boat can dive... Right? Why on earth would they ever want to close them?  If on a war patrol with closed Kingston's they can't dive, so they may as well run up a white flag because they can't out gun a destroyer and they would be ducks in a pond for aircraft?

The Kingstones of the MBT 3 were shut while staying in the harbour - to prevent the boat to submerge accidentally, especially, when the hatches other than conning tower hatch were opened. During the war patrol, the regulations prescribed the Kingstones to be opened.

--
Regards
Maciek

[tore]

Don.
Maciek has already answered your question. I may add in general Kingstons are bottom valves in any ships. For submarines they are vital as Maciek explains, an additional advantage of MBT 3 Kinstons would be if you have a maintenance job on the the vents you are able to do this afloat without having to return to a drydock harbour. On the VIICs you have an additional possibility by shutting the emergency shut off vents in the vent ducts. But think about how easy somebody could pull the venting handle by just removing the lockingpin.
Tore

[Don Prince]

Hello Mr. Tore,


U-Boats which were declared unfit for sea. U-926 had an over stressed MBT 3 creating structural damage to the pressure hull. This damage was caused by a mistake when blowing the tank by her crew during the end of WWII.


How could they over stress MBT 3?  Did they do a HP blow with the Kingston valves and the vent valves shut?  The only place where the Kingston valves for MBT 3 are shut is in the harbor area. 


That sure looks like the CO or Engineering Officer didn't like the idea of surrender...


Regards,
Don_

[tore]

Don.
I never saw the report from the German navy as to the actual cause of the structural damage other than it appeared during a deep dive test in the southern area of Norway early 1945. She was then moved to Bergen where she surrender May 9 th. 1945.
Your remark of hoisting a white flag for surrender is interesting. When the German submarines surrender in Norway May 9th. 1945 ,there were 97 of them,  they were ordered to raise a black flag preferably on the starboard side by the allies when transferred to other locations. I some times have wandered why, because the white flag is international approved by the Hague-Convention of 1899 and 1907 as the official flag of surrender. Could it be the RN would not have a surrender flag which could be taken for the RN`s White Ensign?
Tore