Torpedo Tubes in DKM U-boats

[TopherVIIC]

This is aimed at Maciej 'SnakeDoc' Florek, but anyone with the right answer can jump in...


I have been looking and have not been able to find a definitive answer for this one.


What is the Outside Diameter of the torpedo tubes inside the pressure hull used in DKM Type VII U-boats, and is there a difference in OD between the inside and outside pressure hull?


We have to account for the torpedo itself, the free space between the torpedo outside diameter and the inside of the lining, the lining itself, and the wall thickness of the castings of the TorpedoRohr...

The tubes had an internal diameter 553,6 mm and total length of 755,2 cm. There were built from three segments (one inside the pressure hull and two outside) joined together by means of flanges and bolts. The segments were bronze (late war were steel because of the shortage of the copper).

The images I have been able to find seem to indicate a wall thickness of at least (I am estimating) about 20mm each side. This is my best guess using forensic techniques, photoshop, and a good calculator... :-) The wall thickness may be thicker, but without being able to take the pics I need from 90 degrees, (The exact front) or actually put on calipers or a micrometer, I may never get the answer... :-(

Guessing
Torp Dia= 533mm
Tube ID inside the liner = 553.6mm (that is 10.3mm per side of free space for water to circulate and to allow the piston to free slide through the tube liner)
Wall thickness of tube casting (Guessing) 20mm

20mm+20mm+553.6mm = 593.6mm Rounding up to 594mm.

Has anyone been able to find drawings or slapped calipers on the tubes of U-995?

I am preparing a detailed drawing of my findings of Typ VIIC/41 boats, but this is frustrating me.
Christopher
Illustrator
Military Historian
Model Builder

[NZSnowman]

This is aimed at Maciej 'SnakeDoc' Florek, but anyone with the right answer can jump in...


I have been looking and have not been able to find a definitive answer for this one.


What is the Outside Diameter of the torpedo tubes inside the pressure hull used in DKM Type VII U-boats, and is there a difference in OD between the inside and outside pressure hull?


We have to account for the torpedo itself, the free space between the torpedo outside diameter and the inside of the lining, the lining itself, and the wall thickness of the castings of the TorpedoRohr...

The tubes had an internal diameter 553,6 mm and total length of 755,2 cm. There were built from three segments (one inside the pressure hull and two outside) joined together by means of flanges and bolts. The segments were bronze (late war were steel because of the shortage of the copper).

The images I have been able to find seem to indicate a wall thickness of at least (I am estimating) about 20mm each side. This is my best guess using forensic techniques, photoshop, and a good calculator... :-) The wall thickness may be thicker, but without being able to take the pics I need from 90 degrees, (The exact front) or actually put on calipers or a micrometer, I may never get the answer... :-(

Guessing
Torp Dia= 533mm
Tube ID inside the liner = 553.6mm (that is 10.3mm per side of free space for water to circulate and to allow the piston to free slide through the tube liner)
Wall thickness of tube casting (Guessing) 20mm

20mm+20mm+553.6mm = 593.6mm Rounding up to 594mm.

Has anyone been able to find drawings or slapped calipers on the tubes of U-995?

I am preparing a detailed drawing of my findings of Typ VIIC/41 boats, but this is frustrating me.
Christopher
Illustrator
Military Historian
Model Builder

Christopher, I also been looking for the same thinkness of the torpedo tubes, I went for the 593.6 mm

[TopherVIIC]

Simon,
Thanks for that - I love your drawings. Mine are different, and with a slightly different purpose, but we share the same frustration, eh?
Sk

[tore]

I should probably not interfere in this discussion as Maciek and you guys know more about it than me. As an ex.engineer however I have some reflections as to the
estimated torpedotubewallthickness. There are basically two mainelements which decide the thickness, material and stresses. It is new to me that earlier version of the VIIC  tubes was made of bronze which have a lower tensilestrength than steel, thus require more material given the same stresses. The VIIC/41 has and increased pressurehull wallthickness due to deeper design depth. Thus if the designers would incorporate the same safetymargines on the tubes, it could be 3 versions of the tube- wallthickness. It could be that they kept the outer diameter switching from bronze to steel, that would be easier (and cheaper) and leave sufficient margins to the VIIC/41 stresses, otherwise you should have two different outside diameters of the VIIC and VIIC/41 tubes. 
Forgive my thougths are wandering.
Tore 

[TopherVIIC]

Actually Tore - those are good observations. When steel was used for the late war tubes, the proportions could well have changed from the earlier bronze tubes. I am sure the ex KNM Kaura/U-995 is wearing steel tubes. Now I just need to find what the outside diameter of them is. It would be doubly good to know if there were differences between early VII and late period VIIC/41 tube dimensions, as I am planning on rendering a cut-away U-35 (after her brush with the Admiral Graff Spee). She was an early pre-war VIIA, so would have had bronze tubes.
We need someone with a tape measure to get us a circumference so we can figure out the outer diameter! Any takers?
Christopher

[tore]

Christopher
The germans could of course keep the dimension and change to a higher grade of steel,  but then again the deeper designdepth of the VIIC/41 was obtained by increasing the material thickness rather than upgrading the material. Realizing the painstaking effort they took to reduce the interior weigth in order to compensate for the increased hullweigth could lead us to believe it was a material shortage. The tubes on KNM Kaura ex (995) was steel.
Tore

[NZSnowman]

Actually Tore - those are good observations. When steel was used for the late war tubes, the proportions could well have changed from the earlier bronze tubes.

I would almost be sure when they change from bronze to steel they keep the same dimension, otherwise I think many of the fixer (pipings, handle etc... would not fix correct on the new tubes). Also I believe if they change the dimension the tubes this would mean redesigning the  bow casting as the control arm for open/closing the torpedo doors would not line up correctly.

[NZSnowman]

but then again the deeper designdepth of the VIIC/41 was obtained by increasing the material thickness rather than upgrading the material.

Yes, this is correct the Type VIIC was 18.5 mm compare to 21 mm for the Type VIIC/41. They german's were going to used a better steel (CM 351 compare to St 52 KM) and thicker for the Type VIIC/42.

As a side note I have always wanted to draw the VIIC/42 or VIIC/43, two very cool boats

[tore]

Simon
I agree a possible alteration of the outside diameter would imply a substantial alteration of the fittings. By keeping the bronzedimension for the VIIC steel tubes they would be overdimensioned and it could very well be that the increased depth design of VIIC/41 would let the VIIC steeltubes to be within allowable stresslevel without using a higher grade steel thus no change to be neccesary and all the VIIC and VIIC/41 tubes have the same outside dimension. I guess that is the most probable solution. So it remains to Christophers suggestion to have somebody with a tape to measure the outside tubecircumference on the Laboe U 995 unless Maciek comes up with something.   
Tore

[TopherVIIC]

So it remains to Christophers suggestion to have somebody with a tape to measure the outside tubecircumference on the Laboe U 995 unless Maciek comes up with something.   

Too bad that Laboe is such a walk from here -I doubt that even twin 70cu tanks, a 5mm wetsuit, and an energy bar would get me there!!!


Quick related question - Were the tubes used in the Type IIs the same as the ones used in the early VIIs?
Christopher

[SnakeDoc]

Hi Guys

Guessing
Torp Dia= 533mm
Tube ID inside the liner = 553.6mm (that is 10.3mm per side of free space for water to circulate and to allow the piston to free slide through the tube liner)
Wall thickness of tube casting (Guessing) 20mm

20mm+20mm+553.6mm = 593.6mm Rounding up to 594mm.

Christopher, I also been looking for the same thinkness of the torpedo tubes, I went for the 593.6 mm

In my opinion, each of two guide recesses is almost 3 cm deep. I estimate the tube's external diameter for 64 cm.

Actually Tore - those are good observations. When steel was used for the late war tubes, the proportions could well have changed from the earlier bronze tubes.

I would almost be sure when they change from bronze to steel they keep the same dimension, otherwise I think many of the fixer (pipings, handle etc... would not fix correct on the new tubes). Also I believe if they change the dimension the tubes this would mean redesigning the  bow casting as the control arm for open/closing the torpedo doors would not line up correctly.

I agree with Simon, I'm almost sure, that Germans did not alter the dimension of the tubes, even knowing, that they could save some weight.

I am preparing a detailed drawing of my findings of Typ VIIC/41 boats, but this is frustrating me.

 
I know, that each of us has some pieces of this jigsaw puzzle. Maybe together we will find this out. The next part of my research work on the torpedo tubes, is to create the exact drawings.
For now I can say, that in autumn I'm going to visit the Laboe, and measuring the tubes will be one on my list.

Quick related question - Were the tubes used in the Type IIs the same as the ones used in the early VIIs?

 
If you mean type II - yes, if Vesikko - no (but quite similar).


--
Regards
Maciek