Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Thank you Maciek.  Nice images of the vent locking pins.
Tore

[Don Prince]

Hello Mr. Tore,


 I hope all is well with you and your family... Happy Easter!


I thought about the location of the exhaust valve plate and the shutting direction.  There were three reasons for this particular proposed design:


1. I drew it with the shaft raising upward and shutting the valve because when you turn a valve clockwise the hand-wheel and valve stem would generally move into the valve housing to shut the valve (grind the valve plate and seat in this instance). Also, the valve was mounted upside-down in the exhaust system.


2. When the hand-wheel is turned counter clock-wise to fully open the plate valve, then the rotating hollow valve stem shaft moves downward into the housing, and is not exposed to the exhaust heat or a carbon buildup.


3. When the external flap valve is shut, then it has the external water pressure applied to it. Therefore, the exhaust plate valve should not experience these water pressures.


What do you think?


Kind regards,
Don_

[tore]

Thank you Don.
If you look at the main engine exhaust hullvalves you see the principle, and I guess it is possible they followed the same system on the Junker exhaust. Allthough the outer Junker exhaust valve was not used as a damper, you would experience carbon deposite on the outer exhaustvalve causing leakages as the Junker was a two stroke diesel and more susceptible to carbonization. I agree with your philosophy of shutting valve by turning the handwheels clockwise. I guess we could overcome that by using anticlockwise threads operating the valvestem.
Tore 

[Don Prince]

Hello Mr. Tore,


After reviewing Maciek's info from a U-Boat KBT log which states the following:


"After dis-assembly of the internal exhaust gas valve, it was found that the seat of the valve was burnt or ground out over half of its perimeter.  Repair was not possible by on board means.  The external valve is tight."


It would be virtually impossible to take apart the exhaust valve system and separate it from the outer exhaust casing if the exhaust valve plate extended up into the upper chamber; the valve plate would have to move through the valve seat.


When the valve seat was damaged, they could see that burned and worn out areas. The valve seat must have been face downward because I don't believe they would have disassemble the outer exhaust casing.


However, they could separate the lower exhaust valve system from the upper pressure hull and exterior exhaust casing to inspect the valve plate and the valve seat from inside the pressure hull.


What do you think...


Regards,
Don_

[Don Prince]

Hello Mr. Tore, Maciek, and All,


Mr. Tore - I have checked the Type VII C training manual and the word "Grease" is not there...  With the initial supplies was there some type of container of grease brought on-board?


Maciek - I made the changes suggested on pages 71, and 314, is this OK?


Mr. Tore - When ever you have the time (there is no real hurry for this because I have to do some yard work at home that I need to catch up on).


I hope I have my understanding of the Lubrication Oil problems resolved this time...


Page 72 - 73
Page 85
Page 97 - 99
Page 108 - 109
Page 125 - 126
Page 142 - 150
Page 176 - 177
Page 180
Page 429


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


Mark and Karel - I believe Skizzenbuch is very close to a finished product, and most likely there will be a correction version.  However, If you all see anything wrong, no matter how trivial, then please let me know. I would like Skizzenbuch to be accurate and easy to read and understand as possible.


Mr. Herrn Klaus Mattes will meet with Annemarie Bredow (Uboot-Museum) and with members of the German IMMH on April 22rd, and the day before that he attend a meeting and will present Skizzenbuch at the annual meeting of Uboat Wilhelm Bauer where he hopes to be re-elected to the board.


Skizzenbuch will most likely become a Website book and not a printed book because of the expense incurred with a printed edition.  However, my final version of Skizzenbuch will be encrypted with an embedded reader; it will not allow changes, but will permit printing the book...


Regards,
Don_

[tore]

Don.
The only reliable source we have for the old exhaustsystem of the U 570 execution, is plate 13 showing the coolingwater system. By comparing that with the U 570 images shown by Maciek I guess the KTB is refering to the inner exhaustvalve ( inside the pressurehull) which has its inner casing flange inside the pressurehull hence it is possible dismantle the valve disc into the compressor room. As shown on the plate a leaking outer exhaust valve shall fill the space before the inner valve, just as on the main engine system, hence a proper draining of that space as shown is nessecary. Contrary to the main engine system when we got the cylinders filled water, we turned the engines with open indicatorcocks, this is not possible with the Junker and as a last precausion a watersaparator was installed just before the compressor . A burned valvedisc as reported in the KTB might very well derive from a carbon deposit on the seating creating a local leaking jet acting as a burner on the seating. This is one of the reasons for grinding the deposits away as soon as possible. As I told before if you had such a difficult deposit on the seatings  we very often allowed the seapressure to act on the valve disc to increase the pressure against the seatings while grinding. This is one of the advantages to have the valves shutting with sea backpressure. On the image below I have tried to explain the system. I agree with Macieks theorie.
Tore

[Don Prince]

Hello Mr. Tore,


Did the old original Junkers exhaust system have the ability to grind the inner valve  and seat? 


http://uboatarchive.net/U-107/KTB107-6KTBMaschine.htm
War patrol from 21.4. to 11.7.1942 (6th War Patrol)


The KBT came from U-107 which was a Type IXB that was commissioned on 8.10.40. Would  U-107 have been upgraded with the new exhaust system?


U-107 was lost on 18.8.44 and no survivors...

[Don Prince]

Hello Mr. Tore,


I just thought about something that is very obviously different about the GW Diesel engine exhaust system design and the proposed Junkers exhaust system design:


The GW diesel engine exhaust design uses a beveled gear to swing a large valve shut with not a great deal of force. Therefore, the valve grinding and external seawater pressure is needed to force shut a fairly large diameter valve.


The Junkers compressor valve (proposed design) would be a fairly small diameter plate valve and it is being driven positively shut by the hand-wheel at the bottom of the internal exhaust casing. This type of valve shutting would not need the seawater force to help shut the valve...


What do you think?


Good night it's 6:27 AM...


Kind regards,
Don_

[tore]

Don.
I don`t know much about the developement story of the Junker exhaust system. As they had a fairly long history of troubles before they came to the last construction, I assume there are several alternatives fitted on the various boats. I don`t know, but I would be astonished if they skipped the grinding possibility of the innervalve.  I guess a grindig connection could be as proposed on my image below.
It was never a problem to shut the main engine exhaust dampers by operating the handwheels and no need for any external force. However when a carbon deposit was formed on the seating, external force (seapressure) helped the grinding pressure as a possible strong shutting force exerted by the valveshutting mechanism would increase the pressure resistance on the valvedisc pivot. As told before at some 3-4 meters the sea backpressure prevented the operating of the pneumaic grinding motors without a pivoting shutting force.
Tore

[tore]

Don, Maciek.
I am moving to my summerfarm tomorrow morning, which mean I shall be without the net fo a few days reverting as soon as I can.
Tore

[Don Prince]

Hello Mr. Tore, Maciek, and All,


I have been struggling with the Junkers Exhaust System...


The first issue was getting the gearing to match up with what is present locking segments in the upper pressure hull --- and the fix was to add another gear to my gear assembly and now I have a match when the internal exhaust grinding valve is shut and the segments on the upper hull. Nothing is out of time or sync!


The second issue was getting the segment to line-up with the external exhaust flap valve locking cam  on the upper pressure hull.


a) with a new grinding valve and seat - no problem
b) with a worn grinding valve and seat - big problem because everything moves too further.


I believe the resolution to that problem is to have a very heavy compression spring to close the grinding valve and allow the gear assembly to move to the point where the exhaust flap valve needs to lock the movement. I believe the use of the compression spring buffers the valve wear issue.


I searched the internet and there are die and clutch springs that are rated at 1200 - 1500 pounds. So these springs are good for a depth of 250 -300 meters and beyond...


I have attached the new images - what do you all think?


Kind regards,
Don_
 

[Don Prince]

Hello Mr. Tore and Maciek,


I placed the latest version of Skizzenbuch in my Dropbox folder...  Maciek, I corrected pages 431 and 438, thanks again....


Regards,
Don_

[SnakeDoc]

Hi Don,

I placed the latest version of Skizzenbuch in my Dropbox folder...  Maciek, I corrected pages 431 and 438, thanks again....

Page 431 looks good, but on page 438 you have mistakenly marked the valve for closing Schnorchel air intake duct as "Schnorchel Locking Pin Hand-wheel". I have marked (with green color) the position of this valve on the attached drawing. Without this valve, when the Schnorchel is lowered, while the boat is submerged, the diesel engine intake duct would be flooded.


BTW, on page 425, on the sketch of the 1st generation Schnorchel system, number 6 means "Schnorchel flooding valve", not "Schnorchel draining valve". This valve was needed to flood the part of air intake duct (between ventilation mast air intake and Schnorchel mast) prior to lowering the Schnorchel mast (to equalize pressure inside the duct with the outside sea water pressure).


--
Regards
Maciek

[SnakeDoc]

Hi Don,

I have been struggling with the Junkers Exhaust System...

[...]

I have attached the new images - what do you all think?

If I understand correctly, in your design you assume that external exhaust flap (driven by lever) is interlocked with grinding plate?


Personally I think (as I tried to explain in this post) that external exhaust flap is interlocked with internal exhaust valve. However I do not have any hard evidence to support this opinion.


Regarding the Skizzenbuch: page 97

In addition, I assume a second exhaust valve was introduced outside the pressure hull which has an air connection on the water side to blow the exhaust pipe between the valve and the muffler and operated from inside the pressure hull, with interlock to the aft buoyancy vent valve as previously discussed. As a final countermeasure a water-trap was fitted just before the Junker exhaust outlet as indicated on the system image Plan 13 for the GW engines (See partial plan below right).

In this fragment you are talking about interlocking the exhaust valve with aft buoyancy tank vent valve. I guess that part was not corrected during your latest updates.

However, for U-995, it looks like the external exhaust control lever next the Junkers compressor exhaust valve grinding mechanism works with the interlock which prevents shutting the grinding plate exhaust valve while the Junker compressor is operational and passing its exhaust gases to the water cooled muffler.

As I mentioned before, I have different opinion on this matter, however I cannot proof it.
One note: the design you propose prevents shutting the grinding plate while external exhaust flap is opened (which is not exactly equivalent to the Junkers compressor running).


And final note: we are still missing the proposal, how and where exhaust duct from Junkers compressor was connected to the housing of the valve.


--
Regards
Maciek

[Don Prince]

Hi Maciek,


How about this for a proposal of the entire system...


Regards,
Don_