Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore,

During WWII, was there ever maintenance at sea on a diesel engine where a head valve, piston, or any other major component was replaced where the lifting bars were utilized? I don't believe in your situation at sea where you could go back to port that these types of repairs were ever done...

Regards,
Don_

[tore]

Don
I have no records of any maintenance at sea by the germans during WWII, but based on my experience from the VIICs I guess it could be quite a few. You are right in your assumtion that we carried out major repairs at shipyards along our coast, being about 30.000 km long. Repairs like changing big end bearings and exhaust valves, even a seized supercharger was done by our own crew, otherwise planned maintenance was carried out a our yards.
Tore

[Don Prince]

Hello Mr. Tore,

Would you carry spares like: fuel pumps, oil pumps, air starting valves, etc? Intake and exhaust valves would require pulling a head casting and all those connections; would your crew do that at sea? It seems like replacing an end bearing would be more difficult at the clutch (aft) end than at the forward end of the engine. Were you limited to the spare parts because of shortages of parts from German shipyards that were destroyed during the war?

Regards,
Don_

[tore]

Don.
Spares like oilpumps, and starting air valves were not stored onboard. Consumeables like fuel nozzles, fuelpump plungers were stored. Exhaust and inletvalves with cages was a routine job. Big end bearings were not a problem. The germans left behind a considerable amount of spares in the large submarine pens which were constructed for a larger submarine fleet than ours.
Tore

[Don Prince]

Hello Mr. Tore,

Then if your spares included Intake and Exhaust valves, then your crew used the lifting bar to pull the head casting to replace the valves. That seems like a very time consuming Job to me, along with replacing the crankshaft bearings - Wow! It's a darn fortunate thing that you were not being hassled by Allied aircraft and British Destroyers when attempting to repair an ailing diesel engine...

Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Simon and I were having a discussion about the lines going to the Starting Valves, and I think that the Germans installed a pressure relief valve at the end of the air pressure lines feeding the starting valves lower chamber. If there was a water stroke, then the air pressure would build up and pop the relief valve and possibly avoid any engine damage? See the image and what do you think?

Question - How do you blow out the cylinders with HP air? Open the cylinder drain cocks and what else is done?

Bear with me for a moment... What is a water stroke. Near TDC the exhaust and the intake valves overlap by about 20 to 60 degrees. So a piston could be near the top of the cylinder with both valves open. If there was a water intrusion; then water could go from the exhaust valve chamber, to the cylinder chamber, and then to the intake valve chamber. Now, the first time the piston does an intake stroke, the water from the intake valve chamber is drawn into the cylinder, and then on the compression stroke we get a "Water Stroke" because the piston cannot cycle to the top of the cylinder??? Comments?

Regards,
Don_

[tore]

Don, I have rewritten your two starting air pages of the Skizzenbuch but have trouble in mailing the correct images, at my age (92) I am not very familiar with the E-mail and shall get some help from my grandson next week. My pages explains the starting air system bit further incooperating the maneuvrehandles with manifold. The relief valve on the end of the starting air common rail is adjusted to 75kg/cm2 and with a lifting hight of 12mm too small as a waterstroke cylinderprotection, remember water is acting like a solid rather than a gas. The starting system allows for manual control of the starting air independently of the fuelinjection, hence you can run the engines on air only. As a safetyprecaution you always run the engines by air and open indicatiorcocks, one for each cylinder, open. We called that "blowing through the engine". By massive intrusion of water we sometime cranked the engine by hand with open indicatorcocks.

Tore

[Don Prince]

Hello Mr. Tore,

Thanks for the update...  The U-Boats HP air is capable of 205 Kg/cm square and that's 2,915.79 psi which is huge. Then the pressure relief valve for the starting valve line to the lower chamber was limited to 75 Kg/cm square, or 1,066.75 psi, and it looks like this is the limit of air pressure that may be used to start the diesel engine without popping the relief valve.

Question #1.  Exactly, what was the function of the relief valve? Could you over pressurize the diesel engine with the starting air valve since the bottle source could be 205 Kg/cm square?

A water stroke would happen during the very first 360 degree turning of the crank shaft when you attempt to start the diesel engine with air. The crank shaft speed would be slow and only the air pressure is driving the piston. When you turn the handle on the starting air valve, the air pressure would go from low-to-high. I would think that a water stroke would just stop the crank shaft from turning and not damage the piston, piston connecting rod, the crank shaft journals, or the crank shaft???

However, if I do the math - The piston diameter is 400 mm = 15.745 inches, so the piston surface area is 194.6 sq inches. Now, if we apply 1,066 Psi (75 Kg/cm square) of air pressure, then the total pressure could be 207,449.40 pounds on the piston top... Yep! I guess things could break...

Question #2.  Mr. Tore, what usually broke?

Question #3.  Was there an air pressure gauge that displayed the Starting Air pressure that was applied to start the diesel engine?

Regards,
Don_

[tore]

Don.
It seems I have overlooked a basic element in your understanding of a four stroke engine, the compression and ingnition.
 If you have water intrusion in the engine it usually enters via the exhaust system. The combustion air enters via the engine room as the induction air ducts ends near the outboard bilge. On the exhaust side the usual reason for the water intrusion is the carbonization of the valve seating of the main hull exhaust valve. Allthough you having the pneumatic grindingdevice for the valveseating, leakages occur for several reasons. Time is a major factor, grinding of the main hullexhaustvalve starts as soon as the engines are stopped and boat is ready for diving e.g. totally shut pressure hull and on the COs order. An important element in the grinding is seawater backpressure on the flapvalve disc, hence you want grinding the valvedisc as soon as you leave the surface. Two elements works against this, the pneumatic grinding is noisy and consumes a lot of HP air building up the pressure inside the sub. A third element reduce the grinding time, as you reach about 5-6 meter the flapvalve backpressure becomes so great that the pneumatic motor can`t overcome the grinding friction and stop. All these elements counts in the risk of water intrusion. An ideal dive from the exhaustvalve grinding point of view is 4- 5 meter for some 3-5 minutes, but that is wishful thinking.
 If you are unlucky and have to keep the periscope depth after a crashdive you might have a massive waterintrusion, the 2nd hull exhaustvalve has a special high drain capacity to the bilge, but in the worst case not large enough and might overflow and flood the exhaust manifold along the engine. In spite of drain to the bilge the manifold can be flooded  and water might enter the cylinders. If you start an engine with water in the cylinder equal to the compression volume (dead volume)you might have a waterstroke in the cylinders reaching the compression (ingniton) stroke as the water is trapped solid in the compressionvolume. The collateral damage by the rotating masses can be substatial.
Tore

[Don Prince]

Hello Mr. Tore,

After reviewing all the material we post last week... This is my understanding about a water stroke:

1. A diesel engine is shutdown with one cylinder/piston in the exhaust stroke position
2. The piston is low in the cylinder and the exhaust valve is open (creating an entrance and space for sea water)
3. Another cylinder/piston is in the power stroke position
4. The exhaust system failed and there is a massive sea water intrusion
5. The cylinder/piston in the exhaust stroke fills up with sea water (also the valve head area and the manifold)
6. Starting air is enabled for all cylinders
7. Starting air is applied to the cylinder/piston in the power stroke position
8. The crank shaft attempts to rotate
9. The piston with the sea water filled cylinder attempts to move upward
10. The sea water pushing through the open exhaust valve port creates a huge back pressure (pressure shock)
11. The exhaust cylinder piston barely moves as the pressure increases on the power cylinder piston
12. The starting air valve continues to supply HP air to the power stroke cylinder (increase pressure)
13. The exhaust cylinder piston has a "dead head" (no motion)
14. This is a water stroke

When a diesel engine is normally running; in the exhaust stroke, while the piston is moving upward the burned fuel gasses are compressed as they are forced around the exhaust valve and out the exhaust head port. However, with a water filled cylinder there is nothing to compress which stops all crank shaft rotation, and applies excessive back pressure on the driving piston in another cylinder chamber.

Did the pressure relief valve pop/release when you had a water stroke? Is it just a signaling device, or did the pressure relief have some effect on the starting air system (Shut-off the starting air system)?

Regards,
Don_

[tore]

Don.
Waterstroke. Starting air pressure at 30kg/cm2 is normal for a medium speed engine. The GW engine starting system allows the engine to run on the air (without fuel injection) for a manually controlled time. By allowing the engine to run at full air pressure it picks up speed very quickly.  At a massive waterintrusion filling the engine exhaust manifold, water might enter some of the cylinders and cylindercover inlet and exhaustvalve ducts draining down on the piston top. The compression clearance in the cylinder is 6,6 mm leaving only a very small compression volume in the cylinders during the compression stroke, ( piston at TDC. and all valves shut). Hence at the wrong quick start, the rotating massforces might create an impact between the cylindercover under side and the water on the top of the piston with collateral damages. Some of the engineers were experts in manually controlling the airstart, managing to reduce the starting air and blowing the water out of the open indicatorcocks before the engine picked up speed.
Tore

[Don Prince]

Hello Mr. Tore.

"Hence at a wrong quick start, the rotating mass force might create an impact between the cylinder cover under side and the water on top of the piston with collateral damages."

1. I agree, the cylinder/piston was driving upward in an exhaust stroke with an open exhaust valve, but the water is not pushed out through the exhaust valve port in the head cover because of back pressure; and water is not compressible.

2. I agree, If the start-up is very slow with the indicator cocks open, then this process may clear the flooded cylinders.

3. Was the water stroke primary damage done to the piston or the cylinder cover?

4. What was the function of the Pressure Relief Valve?

Regards,
Don_

[tore]

Don.
At the beginning of the compression stroke a piston moves from BDC to TDC and the exhaust and inlet valves are shut. Prior to this stroke is the inletstroke and the air inletvalve is open creating a suction when the piston moves to the BDC. At this point some of the trapped flooded seawater left in the cylindercover airducts drains into the cylinder and piston top. This seawater reduces or even might eliminate the smallcompression volume (compression clearance 6,6 mm) which might create an impact force on the cylindercover bottom plate by the rotating masses at the air start and you have a waterstroke.
We never experienced a waterstroke so I personally have not seen the damage, but assume the cylindercover bottom and overstressing the cylindercover bolts could a damage.
As on every high pressure vessel a relief valve is installed in the cylindercover. The function is to protect same for excessive high pressure stresses which might occur, like misfire of a cylinder.


Tore

[Don Prince]

Hello Mr. Tore,

"At the beginning of the compression stroke a piston moves from BDC to TDC and the exhaust and the inlet valves are shut."

I understand this part...

"Prior to this stroke is the inlet stroke and the air inlet valve is open creating suction when the piston moves to the BDC."

I understand this part...

"At this point some of the trapped flooded sea water left in the cylinder cover air ducts drains into the cylinder and the piston top."

I don't understand this part???

The sea water intrusion was on the exhaust side of the diesel engine. Therefore, the exhaust inlets in the top cover are flooded, and water may enter through the open exhaust valve and drain into that cylinder on top of the piston.

How does the sea water intrusion get from the EXHAUST INLET side of the top cover to the AIR INLET side of the top cover to flood the cylinder chamber during the intake stroke? I thought the intake and the exhaust chambers in the top cover are physically separated?

As I pointed out previously... If a cylinder piston was neat TDC in an exhaust stroke, then both the inlet valve and the exhaust valve are open (valve overlap with 20 - 60 degrees). Therefore, with this rare occasion you could have sea water entering the exhaust top cover chamber and then flooding into the cylinder chamber and over flowing into the air inlet chamber in the top cover.  With this scenario, I could see a compression stroke where a solid piston stop would happen "DEAD HEAD"...

I don't know of any other way to get sea water into the air intake head top cover...

Am I missing something else?

Regards,
Don_

[tore]

Don.
 I don`t think you are missing anything and agree with your conclusion of filling the inlet ducts by the exhaust flooding water and am sorry to have mentioned the waterdrain from the valve ducts as it is confusing. I once experienced filling water in the cylinder from the exhaust valve having a waterleakage into the cylinder from one of the exhaustvalves water cooled cages having a corrosion hole while the engine was running, but did not experienced any waterstroke as the water evaporated prior to reach the pistontop. We better stop mentioning the exceptions and stick to the basics.
Tore

[Katuna]

Hello Mr. Tore,

Then if your spares included Intake and Exhaust valves, then your crew used the lifting bar to pull the head casting to replace the valves. That seems like a very time consuming Job to me, along with replacing the crankshaft bearings - Wow! It's a darn fortunate thing that you were not being hassled by Allied aircraft and British Destroyers when attempting to repair an ailing diesel engine...

Regards,
Don_

I remember reading that the Germans packed as many crates of spares as they could on board, both below decks and around the Engine Room. I know when U-534 was cut into sections, they found parts crates including a piston and I think a con rod and a liner. they were stored around the engines. I'm sure a lot of smaller parts are stored under deck on the fuel/oil tanks.


Are the racks between the frames, behind the engines original to that time period or were they added after the boat was turned over?

[tore]

I guess I have mentioned it before,  but we found a barrel where a piston was stored in conservation oil onboard KNM Kaura ex. U 995 at that time I was very young and engaged or newly married. In those days we used engagement rings of gold. To get a ring we had to trade in gold at the goldsmith and my wife at that time working for WHO in new Dehli bought som gold to trade trade in for the rings. Opening the barrel I wanted to check the piston submerged in the slippery oil and all of a sudden my ring slipped off and disappered in the barrel. It was of course a disaster and I must confess I used my engineroom crew to retrieve the ring with some work and my marriage was saved. We are still married, this year for 65 years.
Tore

[Don Prince]

Hello Katuna,


As far as I know the metal storage bins in the diesel engine room are original items.  It would make no sense for them to create storage bins during the retrofit and not use them?  Here is an attached photo from the Skizzenbuch Addendum Booklet...


Regards,
Don_

[VIC20]

Yes Tore, you must have mentioned it before, I remember the story about the ring.

[Katuna]

I had forgotten your ring episode! Thanks for sharing again.

[Don Prince]

Hello Mr. Tore and All...

[tore]

j

[Katuna]

A very Merry Christmas to all and hopes for a much better New Year.

[VIC20]

Merry Christmas https://www.youtube.com/watch?v=J_Ucuu-doao

[Don Prince]

Hello Mr. Tore and All,


I updated Skizzenbuch page 433 with new photo of the Schnorchel Indicator...


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


My wife Maureen and I have been talking about visiting the U-995 Museum and other parts of Germany next year because some of her Asian college friends live in Germany as well. I would like to visit Berlin and get together with Mark Hessburg, and even perhaps visit Norway and actually meet first hand with my friend and colleague Mr. Tore Berg-Nielsen...


Regards,
Don_

[Raymic1]

Make sure you contact Mr Paul Patrick-Schroder. A curator at U995
I believe he assisted you with the Uboat files?.
He has been very helpful to me also.
Be great to get a tour into the Tower.


But its closed at present to Covid.

[tore]

Don.
You are welcome, hopefully the Covid 19 restrictions shall be lifted. I donated some images from U-995s life in Norway to the museum.
Regards Tore

[VIC20]

Great, would be nice to meet you Don.

[Don Prince]

Hello Mr. Tore,

I believe you have been copied on the email schnorchel discussions the past month or so with Simon. Arron S. Hamilton's book "Total Undersea War" has a great deal of info about the schnorchel and procedures. I was reading through some of what is available online (I just ordered the book on Amazon) and I have a few questions related to starting the GW Diesel engine...

1. They bring the U-Boat up to 25 meters and raise the schnorchel, then continue up to attack periscope depth.
2. The schnorchel head is above the water and then the Schnorchel air supply shut-off valve is opened and the water in the schnorchel air supply tube is drained into the bilge.
3. The internal exhaust valve is opened to enable schnorchelling and the blowing valve for the selected diesel engine is opened to direct the exhaust gases to the schnorchel.
4. The GW Diesel engine is started with air...

Now, here is where your expertise is needed:
When the GW diesel engine is running on air, how long is it before you switch over to running on fuel oil? I believe the internal air pressure in the GW diesel exhaust system will start to build up at a fairly rapid pace. Therefore, they need to monitor the exhaust air pressure, and open the schnorchel exhaust shot-off valve at the appropriate pressure to blow out the water in the schnorchel exhaust side (something like blowing the ballast tanks). I doubt if the schnorchel exhaust blowing is done while the GW diesel engine is running on fuel oil...

Q1 - How long will the GW air startup normally take?
Q2 - The book stated that the GW supercharger and the MAN turbocharger must both be turned off while schnorchelling. I thought the MAN turbo charger was constantly running?

Regards,
Don_

[tore]

Hello Mr. Tore,

I believe you have been copied on the email schnorchel discussions the past month or so with Simon. Arron S. Hamilton's book "Total Undersea War" has a great deal of info about the schnorchel and procedures. I was reading through some of what is available online (I just ordered the book on Amazon) and I have a few questions related to starting the GW Diesel engine...

1. They bring the U-Boat up to 25 meters and raise the schnorchel, then continue up to attack periscope depth.
2. The schnorchel head is above the water and then the Schnorchel air supply shut-off valve is opened and the water in the schnorchel air supply tube is drained into the bilge.
3. The internal exhaust valve is opened to enable schnorchelling and the blowing valve for the selected diesel engine is opened to direct the exhaust gases to the schnorchel.
4. The GW Diesel engine is started with air...

Now, here is where your expertise is needed:
When the GW diesel engine is running on air, how long is it before you switch over to running on fuel oil? I believe the internal air pressure in the GW diesel exhaust system will start to build up at a fairly rapid pace. Therefore, they need to monitor the exhaust air pressure, and open the schnorchel exhaust shot-off valve at the appropriate pressure to blow out the water in the schnorchel exhaust side (something like blowing the ballast tanks). I doubt if the schnorchel exhaust blowing is done while the GW diesel engine is running on fuel oil...

Q1 - How long will the GW air startup normally take?
Q2 - The book stated that the GW supercharger and the MAN turbocharger must both be turned off while schnorchelling. I thought the MAN turbo charger was constantly running?

Regards,
Don_

Hi Don
The switching over to fuel was a matter of experience, the starting procedure at snorting was pretty much like starting the engines for residue blowing the ballastanks while surfacing, clearing the cylinders by blowing starting air and possible water out via the opened indicatorcocks, then shutting the cocks and admitting starting air to the cylinders and when the engine revs turned dead slow you added fuel according to your experience, as the system derived from the reversible engine design this was a fairly rapid operation, a matter of seconds rather than minutes. A starting failure was not a big deal, you simply repeated the start. As far as I remember if the exhaust backpressure exceeded 0,8 kg/cm2 the reliefvalve at the engine exhaustmanifold lifted and filled the engineroom with black smoke which could be cleared quickly if one engine was running.
The MAN supercharging system was indeed  driven by the exhaustgases and not by the camshaftdrive and clutch with interlock as on the GW engines. On the GW engines you could only clutch in the Roots blower at higher loads.
You monitored the exhaustbackpressure constantly as you did not want the relief valve on the exhaustmanifold to open. 
Tore

[Don Prince]

Hello Mr. Tore,

Thanks for the info...

According to Aaron's book:
1. They bring the U-Boat up to 25 meters and at a very slow underwater speed, they raise the schnorchel mast/lock and then proceed to where the schnorchel head is above the water and the exhaust pipe is below the water surface.
2. They drain the schnorchel air mast into the bilge, so the front tube ready for operation.

Now, the issue is how do they blow the water out of the exhaust pipe and start the Diesel engine at the same time? The schnorchel exhaust system will be flooded back to the schnorchel exhaust shut-off valve above the deck on the starboard side of the tower. So, the schnorchel exhaust pipe is flooded.

Question - Can you blow compressed air into the exhaust system while opening the schnorchel exhaust shut-off valve, and start the diesel engine during or very shortly after the blowing process. You do not want to open the exhaust relief valve with back pressure during start-up?

Regards,
Don_

[Don Prince]

Hello Mr. Tore,

From Aaron...
"To the best of my understanding, based on the engineering reports and archival documents, the exhaust line remained, generally full of water. To what extent I do not know. The backpressure generated by the diesel engines kept the water at bay as the exhaust gasses were expelled. This is why it was so very important to close the shutoff valve at the end of snorkeling otherwise the water flushed back to the engines, forced toxic gasses into the engine room and could flood the engines."

Some of that doesn't make sense... If you stopped the diesel engine and failed to shut the schnorchel exhaust shut-off valve, then you could flood the engine. However, I don't see the toxic gasses into the engine room under that scenario.

Starting the Diesel engine for schnorchelling:

I imagine that you keep shut the external diesel exhaust valve, drain and open the internal diesel exhaust valve, and open the main exhaust valve (port or starboard) for blowing. Now, we have air filled pipes up to the schnorchel shut-off valve. At this point, you are setup for blowing the schnorchel exhaust mast that is full of water (about 8 meters high).

If we start the Diesel engine on air and monitor the exhaust pressure gauge for blowing the ballast. When the pressure gets to .5 kg/cm2, we open the schnorchel exhaust shut-off valve and switch the diesel engine to fuel (Start). Then bring the engine up to speed while clearing the schnorchel exhaust mast of water. Hopefully, when the hot exhaust gases hits the compressed air and it expands in the exhaust pipe system, it push the water up and out of the schnorchel mast exhaust pipe, and not cause exhaust safety valve in the diesel room to open...

Does this sound reasonable?

Regards,
Don_

[tore]

Don. There are many alternatives when omitting to do obvious things  as well as doing wrong things. The snorting system introduced at the end of the war was designed making use of the existing systems. Hence the snort/exhaust system was connected as much as possible to the exsisting system e.g. by a valveconnection to the drain chambers between each main/internal exhaustvalves. This means that the snort exhaust pipe could be drained by the original exhaust system drainage down into the bilge and pumped overboard. This would of course not imply filling the engineroom with black smoke (exhaust.) The main reason for getting exhaustleakage into the engine room with exhaustpressure exceeding the preset relief valve adjustment (mainly 0,8 kg/cm2) on the exhaustreciever. In rough weather you could of course dip the top exhaust outlet that much causing the reliefvalve to open( happened to me a couple of times).     I rather would drain the system the normal way if time allowed.
Tore

[Don Prince]

Hello Mr. Tore,

Did you raise and lock the schnorchel mast while on the surface, and then dive to schnorcheling depth?

Or -

Like Aaron discussed; They brought the U-Boat up to 25 meters depth and raised and locked the schnorchel mast, and then went up to schnorchelling depth:

1. The schnorchel head was above the surface, but the mast was filled with water. So, they drained this water into the bilge (problem solved), and now the schnorchel mast air intake section is cleared.

2. The exhaust pipe on the schnorchel mast is below the surface. So, they can not just drain the exhaust pipe because it would continue flooding with sea water (problem)? Somehow, they had to blow the water from the schnorchel exhaust section of the mast ahead of the schnorchel exhaust shut-off valve...

Under Aaron's scenario, how did you start the diesel engine and blow the schnorchel mast exhaust pipe clear of water?

Regards,
Don_

[tore]

Don.
 I really don`t remember raising the snortmast at 25meters nor to have seen  any indication in the german orderbooks mentioning such a maneuvre. We frequently raised the mast surfaced for service with no trouble.
Point 2. in your question draining the exhaust mast.  The exhaustpipe of the snortmast is connected via a shutoff footvalve to the exhaust blowingsystem and utilizes the two exhaust pipebranches ( port and stb) for residue blowing from the chamber between the outer and inner main exhaustvalves. This complicated watercooled valve casing is described in your Skizzenbook. As mentioned,  the chamber is enclosed by two valvedisks and hard to get watertight due to carbon formation on the valvesatings,hence a rotating valvdisc is provided, further the outer main exhaustvalve  is a flapvalve used for backpressure adjustments during residueblowing of the main ballast tanks. When the snortexhaust pipes are connected to this system it is connected to a fairly large internal drainage system operated by the large main drain pump in the controlroom. As we have discussed before, a massive intrusion of water in this system can be gravitydrained from the exhaust valvecasing chamber into the engineroom bilge before getting to the exhaustmanifold of the main engine, even this manifold has a substantial drainage capacity to the bilge before the water might enter the cylinders of the engines. Finally, getting water into the engines is not a disaster as we have discussed previously. Allowing water in and out of the submarine was a routine. Large and long half filled vessels could create a non desireable surface effect.


Tore

[Don Prince]

Hello Mr. Tore,


If there was an exhaust leak and some of the water backed up into the exhaust Manifold, then where is the valve located on the GW Diesel engine to drain the water? Is that drain valve located on Plate 15?


Regards,
Don_

[tore]

Don.
I don`t think the drainvalve is located on plate 15 as that is the starting air supplysystem. I don`t remember but guess it could be one of the valves indicated on plate 13 may be one of the valves having a sightglass. As mentioned the snortsystem were installed by the German navy latter part of WW2, at that time they were short of everything and the snorting system was designed pretty simple utilizing exsisting systems as much as possible hence existing airducts and exhaustblowing system were used. The exhaust system utilizes the exhaust blowing system going from the chamber between the outer main exhaust flapvalve and the inner main exhaust flapvalve continuing by the two pipes (stb and port) to the exhaust ballast tank blowing panel eg. 8 valves outside the pressurehull. The valves have elongated valvestems down into the controlroom. After this valvechest  the pipe continues passes a shut off footvalve operated from the controlroom and up the snortmast having outlet well below the ringfloat air intake valve.
You don`t clear the water in the snortmast exhaust system by blowing HP air but drain the mast by one of the drainvalves in the aft engine room, I don`t remember which but possibly the pipe with valve and sight glass.
Tore

[Don Prince]

Hello Mr. Tore,

I believe that valve (n) is used to drain the exhaust manifold of flooded seawater into the bilge, and the safety valve is to the right of it on Plate 15.

I had a wrong label on the large funnel and corrected it as "Drain into Bilge."

What do you think?

Regards,
Don_

[tore]

Don.
Checking the other plates 13 I figured out the plate 13 for the GW engines have wrong letters for several valves like valve p becomes o hence a wrong and confusing  naming and purpose of the various valves in the system.Below is a correction which might clear up the matter.


Tore

[Don Prince]

So, in order to drain the exhaust manifold you will need to open the venting valve (n) and the Drain valve (o) on the exhaust manifold...


Don_

[tore]

Don.
I guess the venting valves belongs to the anticorrosion system. E.g. you are draining the seawater in the coolingmantels. We did not make use of the anticorrosion system and had only minor problems.
Tore 

[Don Prince]

Hello Mr. Tore,


I guess where my confusion begins about the cooling water system involves the jacketing of the exhaust manifold. Some of the draining valves are taking water and possibly some air from the cooling water jacket space. However, the vent and the drain for the exhaust manifold has to pass through the water cooling jacket to the inner chamber of the manifold in order to function properly.


Therefore, valve (n) the vent valve line, the safety valve line, and the drain valve (o) line must pass through the water cooling jacket into the exhaust manifold chamber in order to function properly...


What do you think?


Regards,
Don_

[tore]

Don.
This is only for draining the sea cooling mantels in the system not the possible seawater from the leakages of the main exhaust flapvalves. In a confined space like the coolingmantels you need a vent to be able to drain properly.
Below is an image of the reliief valve of the exhaust reciever, as you see pretty close to the maneuverstand and could be unpleacent for the man operating the engine.

[Don Prince]

Hello Mr. Tore,

I have the same view of the Diesel engine that you have item listed the components in your previous posting. However, with the magic of the Paint.net application, I can bring some components to light! Could what I have uncovered be the components in Plate 13 that I had marked as well? The lower handle looks like a black "L" shaped handle and the drive shaft extends under the diesel engine exhaust manifold end cap near the operator.

Regards,
Don_

Addition:
If you look at this drawing that you had done several years ago (last posted). The exact same valves are identified as the vent valve (n) and drain valve (o). However, I believe these valve actuators are located near the safety valve at the forward end of the exhaust manifold, and not in the relative position as shown in the schematics.

[Don Prince]

Hello Mr. Tore,

The top valve in my previous posting looks to be a cooling water drain valve per Simon's drawing (see the red circle)...

Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Do you have a photo of what valve is connected to pipe #7 on the u-historia photo?


Regards,
Don_

[tore]

Don
I have been looking into my files and the only I found is the image below.
Tore

[tore]

Don.
Somehow the lower part  of my image was cut off. Here is another try.
Tore

[Don Prince]

Hello Mr. Tore,

I didn't realize that U-historia has two #7 items listed...  I took one of Simons drawings and it looks like the line in "Yellow" drains the the Main internal exhaust valve chamber of flooded seawater???

I was just attempting to get that established...

Regards,
Don_

[tore]

Don,
I leave it to Simon to comment on his drawing, but guess you remarks on draining the snortmast and startig is correct with a few minor things. Basicly the starting procedure is the same as for any start. As you normally shall have some water in the chamber between the outer and inner main exhaustvalve. However if you have a massive intrusion of water you might experience a filling of the exhaustmanifold with a possible filling of some cylinders as you have explained. In any start you blow through the cylinder with open indicators cocks and the engine shall turn a few revs, you don`t  open the indicatorcocks to "make it easier to turn the engine", the reason is to blow out possible water in the cylinder through the open indicator cocks to prevent waterstroke. The starting airpressure of 30 kg/cm2 is ample to run the engine easy on air only, but you want to prevent water strokes, hence you want to get rid of the water in the cylinder which might created a major damage by a reciprocating engine. Only in extreme cases you crank the engine by hand, not normally, as air shall do the job easy having an experienced engineer at the starting handle bowing out the trapped water in the cylinders flooded.
I noted some place you mentioned we dived with the snortmast raised, that is a misunderstading, we normally raised the snortmast submerged but raised the mast for maintenace surfaced, see the image below, however we did we never run the engines with the mast raised on the surface as the mast did not have any cooling and the greaseingpoints could be ruined.
Tore

[Don Prince]

Hello Mr. Tore,

Thank you for the corrections...

#1) Starting the Diesel engines with controlled air pressure makes perfect sense (The only cylinders that should be flooded with seawater had their exhaust valve open when the Diesel engine was stopped - flooding occurred via the cylinder head exhaust chamber and the exhaust manifold seawater intrusion)...

1. HP air is admitted on a piston in a power stroke (drives it down the cylinder liner & turning the crankshaft).
2. Any piston in the exhaust stroke will force any seawater out of the liner via the open exhaust valve.
3. Any piston in the intake stroke will take in pressure hull air via the open intake valve.
4. Any piston in the compression stroke will force air out through the open test cock.

After the first 2 full turns of the crankshaft there should be practically no more water in the flooded cylinder liner depending upon the flooding state of the exhaust valve chamber in the cylinder head. Eventually, all flooding water will be forced into the exhaust manifold with HP air and drained into the bilge via the open drain valve...

#2) OK... You raised the schnorchel mast submerges as Aaron suggested. So, you had to drain the Schnorchel mast air supply section into the bilge to clear the water and open up the air supply.

The schnorchel exhaust mast is still flooded up to the tower deck exhaust shut-off valve? U-995 had the Type II schnorchel with the bend in the air supply, and the straight connection from the schnorchel exhaust shut-off valve and through the blowing valve and then to the Main External Exhaust Valve. The exhaust system on the Type II schnorchel doesn't seem to have a draining capability? 

This was the question that I was attempting to understand... What was the starting procedure to deal with the flooded schnorchel exhaust system at the schnorchel exhaust shut-off valve?

Regards,
Don_

I thought that just starting the Diesel engine on air like normal, and when the internal exhaust system got up above 0.5 atmospheres (like blowing the ballast); then opening the Schnorchel exhaust shut-off valve and switching to fuel oil (ignition)?

However, Aaron has documentation of a special HP airline attached to the exhaust manifold to blow the schnorchel exhaust mast...

[tore]

Don.
The snort exhaustpipes have indeed a draining capacity as they are connected via shut off valves to the drainchamber between the inner and outer main exhaustvalves port and starboard. When draining the raised snortmast you can open one of these shut off valves and drain the water into this drainchamber and you have a normal situation like a leaking outer main exhaust flapvalve, hence you drain the water in the drainchamber to the bilge and discharge it overboard.

Tore

[Don Prince]

Hello Mr. Tore,

I agree that the drain capacity is there as you described... However, the schnorchel exhaust pipe outlet is about 0.5 meters below the seawater's surface level. You can drain the schnorchel's exhaust mast all day and never empty it because it will constantly be refilled by the surface water! Therefore, the Schnorchel's exhaust mast must be blown and then start the Diesel engine immediately to maintain the opened exhaust capability with the exhaust pressure...

Regards,
Don_

[Raymic1]

Hello Mr. Tore and Don
Hope you are all well?
During my research, I noticed these brackets.
I have asked this question recently on some Uboat Facebook sites and even the curators of U995 are unsure as to what these brackets on U995 were used for.
I have identified 3 of them so far onboard U995 from pictures, one under the Switchboard, one in the Galley, and One in the Forward Torpedo Room. There may be more I haven't found as yet.
No one is 100% sure if they are Kriegsmarine or Norwegian add ons.


And I see on my U570 Photo that there is NOT a bracket, although U570 Switchboard is early war Round type and U995 is late war Rectangular.


Some suggestions have been


1.Original Fire Extinguisher holders, either Kriegsmarine or Norwegian,  although they seem a bit small
2.Flashlight holders, although the Kreigsmarine Flashlights were generally square shaped.
3.Filters or spares holders
3.Crew Emergency Oxygen holders.


Can you shed any light on this mystery bracket at all?
thanks
Raymic (Mike)

[tore]

Hello Mr. Tore,

I agree that the drain capacity is there as you described... However, the schnorchel exhaust pipe outlet is about 0.5 meters below the seawater's surface level. You can drain the schnorchel's exhaust mast all day and never empty it because it will constantly be refilled by the surface water! Therefore, the Schnorchel's exhaust mast must be blown and then start the Diesel engine immediately to maintain the opened exhaust capability with the exhaust pressure...

Regards,
Don_

Don, you are absolutely right, I have no excuse but the brain of an old man now going on 94. Back to the drawingboard. Have you seen the German instruction on the orders for raising the mast of 1944? It is unfortunately in the german luangage but gives a good impression how the Germans operated the snortmast . I have briefly read it  with my rusty german knowledge, but as far as I can see they raised the mast submerged, ascended up to periscope depth, ( not mentioning which periscope) prepared the engines for start by starting the luboilpumps, normally blew through the engines a few times. Then at pericope depth they drained the airmast prior to starting the engines carefully while opened the snort mastexhaust valve monitoring the exhaustgaspressure not to exceed 0.8 atm. I am mailing the font page of my document which I have only breafly scanned. By this procedure they are using the engines blowing out the snortexhaust mast with narrow margin as to max exhaustpressure . In this detailed document  there is no metioning of blowing the exhaust mast with HP air, it seems they simply used the diesels at low load. May be worth while to check further, I guess some of our german friends might be able to translate the document.

[Don Prince]

Hello Mr. Tore,


Perhaps we could ask Mark Hessburg to translate the document...  I tried, but the scanned copy is really difficult to read...


Regards,
Don_

[Don Prince]

Hello Mike,

Sorry about not getting back to you earlier...

My best guess is that your first thought as those being fire extinguisher brackets sounds about right. The big red ones throughout the U-Boat are not originals by any means. Just put there during modern times for insurance regulations and tourist protection.

I don't see those brackets in the Control room, the NCO's ward room, Officer's ward rooms. The Diesel room may have its unique fire control system; you need to ask Mr. Tore about that situation. However, the forward and aft torpedo rooms contains explosives, and the E-room could have an electrical fire. As far as the Galley is concerned, the cook could have a bad day and set something on fire...

I searched the internet for WWII German fire extinguishers and her is what I found. They look like they could fit into those brackets...

Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Do you have any information about the Supercharger clutch and the linkage that activates it? I found it on one of your drawings and would like to understand that part of the GW Diesel engine...


Regards,
Don_

[tore]

Don,
As you know the U 995 was originally designed to be propelled by direct reversible GW engines hence the linkage with clutches are originally equipped with a number of interlocks no more applicable. Below is an image of the system where I have removed the superfluous reversing rudiments. The GW engines were as you know designed with a Roots blower pto from the camshaft and should be switched in at 390 rpm. The drive is shown on the image below. At a normal start the supercharger is disengaged. On the both engines there are two manifolds towards boardside, the upper for airinlet, the lower watercooled, for outlet. The outletmanifolds are connected via flanges to the cylindercover exhaustducts (with exhaust cages, watercooled). The airmanifold has flangeconnections to the separate airinlets in the cylinder cover. Further the air manifold has two inlets which can be shut by cylindrical slidevalves operated by the supercharger clutchhandle up front of the engine and to the Roots bloweroutlet, thus now an enclosed airsupply to the cylinders..
If revs are required above 390 the fuelfilling handle is pushed to a higher fuelfilling position, the supercharger clutchhandle at the outboard side pushed rotating the rod by bevelgear. The rotating rod continues after the air shutting valve where the rod is fixed to a 90 degrees bevelgear transferring the rotation to a rod with gearwheel which is engaging a tootrack, which is axially moved and thereby trigger the friction shoe of the friction clutch. 


Tore

[Don Prince]

Hello Mr. Tore,


The finer detail... Is this how it works (see the attached drawing)?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


I got a drawing of the supercharger clutch and now see how it works...


Regards,
Don_

[Don Prince]

Hello Mr. Tore,

I came across this drawing of the Supercharger and it looks like the input air is run towards the outer casing. I guess the air vents on the outer casing is adding a cooling effect to the compressed air fed to the Diesel engines intake manifold and the cylinders...

Regards,
Don_

[tore]

Don.
In supercharging mode the inlet air enters towards boardside as the main dieselair outlet . The main dieselair shaft ends down towards the bilge is draining seawater mixed with air to the bilge, creating an impressive splash whereas the combustion air shaft on air intakes both for the normal aspirated and supercharged mode are situated a bit higher up and well apart from the dieselair duct outlet. I am afraid the arrangement do not allow for any "intercooling" effect. In spite of the arrangement we experienced salt deposites on the Roots blower rotors jamming same and we had to dismantle the blower for cleaning. My personal opinion is that in extreme weather the dieselairshaft was occasional flooded via the valve in the towercasing causing a massive intrusion of seawater mixed with air which eventually entered the air inlet of the supercharger, the seawater evaporated during the compression in the Rootsblower and left the deposits in the blower. Cleaning the blower was a 12-14 hours job[size=78%].[/size]
Tore   

[Don Prince]

Hello Mr tore,

When you experienced the Roots Supercharger jamming because of sea salt on the impellers or in the air chamber what broke? The supercharges is gear driven from the Diesel engine crankshaft. I would think it would be the impellers were damaged because the Diesel engine is turning at around 2000 RPM when the supercharger clutch was engaged (possibly the clutch was damaged too)

Interesting...

Regards,
Don_

[tore]

Don
When you clutched in the Roots blower you noticed very clearly the frictionclutch started slipping and smoking so you declutched immediately. No dammage was done to the clutch or geartransmission (camshaftdrive)
Tore

[Don Prince]

Hello Mr. Tore,

I guess that I'm starting to forget things....  I have been looking over some drawings from Crushdepth.com and the mechanical hydroplane indicators are using the Telekin System. I thought that we had discussed this topic but I don't remember Telekin name???  What did we use years ago?

Regards,
Don_

[tore]

Don.
I guess the system is called Teleflex.
Tore

[Don Prince]

Hello Mr. Tore,

Do you have any documentation that states when the grinding of the exterior exhaust valve seats changed from a manual hand-wheel operation to the pneumatic motors. It looks like the Type VII B U-Boat was only a manual grinding operation.
 
1. Was the pneumatic grinding motors part of the upgrade to the Type VII C?   
2. Was the pneumatic grinding motors an upgrade to the Type VII C at a time later?

Regards,
Don_

[tore]

Don.
Sorry, I have not any documentation as to the fitting of the pneumatic grinding of the outer main exhaust flapvalve. I doubt this was a feature of the VIIC/41 only, as both of our remaining VIICs (not 41) were equipped with same.
A disadvantage with the Pneumatic grinding was in the event of the need for a longtime grinding, the internal air pressure in the sub increased and some time we had to start the E-compressor to lower this pressure.
Tore

[Don Prince]

Hello Mr. Tore,


This photo is of the bulkhead inside the forward torpedo room...  Do you remember what would be located at the red circled location?


Regards,
Don_

[tore]

Don.
Sorry I cannot remember, to me it looks like a bracket for a gyro repeater, a lot of stuff were mounted on this bulkhead particularly electronics related to Nato surveillance after my time. The small hooks up on the top of the image were hooks for the brigde rain coats to be dried.

Tore.

[tore]

Don.
Returning to your question of today I am posting an U-Historia image of the equipment hooked up to the item you questioned. As you see it is indeed more to it than just a bracket and as I assumed related to surveillance installed after my time. I guess everything of this installation is classified and removed.

Tore

[Raymic1]

1.Mr. Tore..was there supposed to be a U-Historia picture attached?


2. Ref the original inquiry, there is at least 3 of these White Circle mounts on U995.
Attached is a picture from the Rear torpedo room one, above the Electric Compressor.
There is also an electric wire that runs into the back of each of these  'White Circles'

[tore]

Raymic1
Sorry somehow my U-Historia image was not posted hope my second try works.


Tore

[Don Prince]

Hello Mr. Tore,


I have a question about roll stability with the Type VII C U-Boat:


1. When FBT 2 and FBT 4 are in the fuel oil configuration, the U-Boat sets lower in the sea water and this would add to the roll stability because the center of gravity is lower compared to the water surface. Therefore, the U-Boat has a degree of roll stability.


2. However, when FBT 2 and FBT 4 are in the water ballast configuration, the U-Boat sets a little higher and the water line is raised. But, FBT 2 and FBT 4 empty tanks also provide stability against rolling.


Is one state better than the other for roll stability, or are they about the same?


Regards,
Don_

[tore]

Don.
 Sorry about my late answer, I have just returned from my summerfarm where the access to the net is limited.
The transvers stability of a submarine is a bit complex and consist more elements than saddle tanks and fuel, in general you might say it has many variables as follows:
 1. Stability on the surface where the submarine acts like any surfaceship and the stability is governed by the metacentric hight.
 2. Stability submerged where the submarines transverse stability is created by the distance of the submarines center of gravity and center of boyancy. A proper way of obtaining transverse stability is placing heavy equipment between the submarines center of gravity and center of boyancy. A proper stability is achived by by putting heavy equipment like batteries as low as possible.
 3.The complicated stability while breaking the surface when the metacentric hight reduces, hence the tranverse stability as you ascend and break the surface. The COs normally like to have a check on the wind and waves to put the submarine in the right position as you break the surface  when the tranverse stability is low. I have experienced excessiv heeling of more than 45 degrees during surfacing. As far as I remember the batteries could take 60 degrees before spilling acid.

     Tore

[Don Prince]

Hello Mr. Tore,


Which state would you consider more roll resistant with a U-Boat Type VII C on the surface:
1. U-Boat in fuel oil reserve mode with the saddle tanks full, the U-Boat is about 9 inched lower in the sea as is the center of gravity.
Or
2. U-Boat saddle tanks in the water ballast configuration, and the air filled saddle tanks on the side of the pressure hull resisting the roll motion.


Regards,
Don_

[tore]

Don.
As mentioned before a submarines transveres stability has many variables and saddletanks introduces many more, without going into the metacenctric hights and naval architects math. you may say filling the seawater compensated saddletanks with fuel introduces a rise of the submarines center of gravity and weight, this shall normally reduce the transverse stability. With the saddle tanks filled with air and no water creating surface effect the submarine looses weight and the center of gravity sinks, hence the stability increases.
Tore

[Don Prince]

Hello Raymic1,


Paul "TheEngineeringGuy" on the CrushDepth Website discovered that the plates were for a mechanical clock. I tend to believe this is true because to the three (3) mounting holes. Also, The clocks were the first thing to be pilfered from the U-Boats after WWII...


Regards,
Don_

[Raymic1]

Thanks, Don for the clocks. Very interesting.


I also took this still from a video on FB off a Fort Aniota Museum at Fort Zachodni Poland.
It looks like a Mergus-type Uboat Toilet but is not as complex.?

[Raymic1]

Also in regards to the clocks. Here is a close-up view of the back of the circular plate in the rear Torpedo room.
You can see some sort of electrical wire or pneumatic cable going into the back of it. So possible the clocks were powered either this way?

[Don Prince]

Hello Mike,


I believe that view of the back of the mounting plate is a bit misleading. This front view of that plate does not show any hole towards the center. Besides ,the U-Boat clocks were key wound as you can see on the clock face just above the 6 in the photo that I previously posted...


Regards,
Don_

[Raymic1]

Yes your right. A bit of parallax in the rear pic....

[tore]

Being immobilized for a few weeks due to the gout made me some sparetime to re-arrange my e-painting of KNM Kaura, ex U 995. It is pretty much the same image as previously published. A fiction of KNM Kaura in the Vestfjord, Northern Norway, above the artic circle, where we usually were patrolling, escorted by a group of killer whales while passing the lighthouse Kaura (where KNM Kaura got its name from) and the old steamer S/S Finmarken (the lifeline to the rest of the world). The image is a fiction from 1953, part of it published in 2017. Might be some of the present days follower haven`t seen it.
Tore

[Don Prince]

Hello Mr. Tore,

I got the Gout about a month ago and my doctor gave me a 10 day prescription for Prednisone (A steroid) which resolved the painful problem... I get a severe case of Gout about 2 - 3 times pre year.

Regards,
Don_

[tore]

Don
Same thing here, but the last attack lasted 4 weeks, I am OK now.

[VIC20]

Tore, Rob Brassington, who created this awesome animation, is looking for information about the mechanism of the torpedo tube. The video shows his level of knowledge or simplifications for lack of better knowledge. Maybe you see things that should be different?


https://www.youtube.com/watch?v=CAO2BYZdfE4

[Don Prince]

Hello Mr. Tore,


Do you remember where this valve chest is located in the diesel engine room?


Regards,
Don_

[tore]

Don.
This valvechest is situated right underneat the writing deskplate port frontbulkhead in the engineroom.
Tore

[Don Prince]

Hello Mr. Tore,

I can see the valve chest for the Lube Oil located below the Desk Plate, but I can't locate the valve chest for the Fuel Oil in that area...

Don_

[tore]

Don.
As you know the aux. luboil pump could be used as an emergency fuel transferpump. This function was not likely to be used frequently and the connection to the fueltransfersystem was not as easy accessible as the aux. luboilpump function ( Used prior to every turning and start). I personally never used the aux. luboilpump as a fueltransferpump but as far as I remember the connectionvalvechest shown on the plate 9 was situated under the floorplating between the main engines hence not visible on the immage. If you look at the fuelpiping in and out of the fueldaytank (setlingtank) and on the front of the engines you have an idea of the considerably smaller pipingdimension.
Tore

[Don Prince]

Hello Mr. Tore,


Thank you for the update and information. I believe Patrick will goto U-995 and attempt to get a photo of the Fuel Oil Valve Chest... He has been helping with the restoration and has unusual access to U-995.


Regards,
Don_

[Don Prince]

Hello Mr. Tore,

Can you verify if the market valved are the Fuel Oil Valve Chest?

Regards,
Don_

[tore]

Don.
I don`t think these valves belong to the fuel transfer system, hard to see the detail but I guess they are valves belonging to the ordinary luboilsystem.
Tore

[Don Prince]

Hello Mr. Tore,

FYI... You are correct about those valves belonging to the lube oil system...

It looks like the fuel oil pump was the easiest pump to replace, them the lube oil pump, and lastly the water cooling pump. How much time did it take to replace each of the three (3) pumps?

What was the failure mode for the fuel oil pump; It is gear driven and is well lubricated with fuel oil? I would think if a screw or nut got past the filter and jammed the pump gears, then an intermediate drive gear would have a shear pin so that nothing in the diesel engine side would be damaged. Was there an issue with the pump just wearing out and what usually broke?

I have the same questions about the lube oil pump and the water pump???

Regards
Don_

[tore]

Don.
Your questions might be unclear to some as it covers a lot, like fueloil-, lubeoil- and coolingwater systems, including the components, their maintenance and alternative operation. I guess it would be easier to split up the questions referring to each system separately. A full basic understanding of the discussed system is vital. Generally all systems have a number of alternative operationsolutions and sometimes you had to use your creativety and study the system plates to figure out which solution to use. No book could tell the optimal solution for every situation, experience and creativety of the engineroom crew had to be used.
Tore

[Don Prince]

Hello Mr. Tore,

Basically, how much time would be required to change out the Fuel Oil Pump, the Lube Oil Pump, and the Water Pump. If one (1) of these three (3) pumps were swapped out after a failure, then what was the main reason for the failure as observed during your service on U-Boats...

Regards,
Don_

[tore]

Don.
A HP fuelplungerpump, driven by the camshaft, 11/2-2 hours, the attached fuel supply pump, driven from the crankshaft up front 2-3 hours, the fueltransferpump electrically driven vertical IMO type trippel screwpump 8-9 hours. Hour estimations assuming sparepump available, apart from the camshaftdriven HP fuelpumps  normally no complete pumps stored on board. We had a few seized HP plungerpumps otherwise we did not have much trouble with the fuel/lubeoil pumps.
Tore

[tore]

Don.
The electric driven coolingwater pump did not give us any trouble, however on the attached piston coolingwater pump the conrod of the piston broke and smashed the cylinder. The pump is situated very low with difficult access up front of the mainengine and could not be repaired by us. Same pump was repaired at the submarine baseyard.
Tore 

[tore]

The flexibility of the various system. As I have mentioned before the systems have been designed for many alternative solutions left to the engineroom crew skills, experiences, and creativity to utilize. One important feature is the aux. luboilpump function as a fueltransfer pump. Being able to bunker fuel from any sources might be vital. This is a detailed description of one solution of many.


Bunkering fuel utilizing the aux. lubeoil pump.
One of the aux. lubeoil pumpoperations is pumping fuel from a source not capable of of supplying fuel with sufficient pressure. Referring to the plate 9 below it goes as follows:
 In the casing is a hoseconnection leading to a fueloil pipe which enters the pressurehull via a hullvalve (a). The pipe, marked dotted green, enters a nut and bolt filter and continues to a suction inlet in a valvechest underneath the writing plate on the forward portside engineroom bulkhead.
In the event of bunkering fuel from a source not capable of supplying fuel against the head of the watercompensated fueltanks the aux. luboil/fuel pump suction is connected  to the suction connection b2. on the valvechest and the pump discharge the fuel into the chest pressurechamber via valve b1. By opening valve valve c in the chest the fuel continues to a filter before a fuel meter. Then the pipe return to the valvchest via cock e and leave the chest by opening valve b6. then via  a bypassfilter before entering a selector cock e1 which makes it possible to select port , starboard or both daygravety tanks which then can be topped up. From the selected gravety tank the fuel passes a fuel meter, a branch off to the Junker compressor to a 3 way cock in a crossover pipe to the suction of the engineattached fuel supply pumps port and starboard. In spite of the plate 9  the GW engines these pumps are driven from the crankshaft up front of the engines. From the supplypump the fuelpump deliverypipes goes to a finefilter on the top of the camshaftcasing the filter is not shown on the plate 9.
By using the same methode you are able to bunker any internal fuel tanks as can be seen on the plate 9.


Tore

[Don Prince]

Hello Mr. Tore,

I believe valve (k) is an overpressure device to limit the fuel oil pressure to the injectors. If one of the diesel engine's fuel oil pumps failed, then you could use compensation water pressure from any external tanks, or the Auxiliary Fuel Oil Pump to provide fuel oil to the injectors by bypassing the failed pump using the internal fuel oil tanks. Also, while using the compensation water pressure or the Auxiliary Fuel Oil Pump with a failed fuel pump the day tank is bypassed...

My question is: When you bypass the failed fuel pump and provide fuel oil pressure to the injectors on that diesel engine. However, the engine with the functional fuel pump will see the increased fuel oil pressure at the pump's head. Does valve (k) just feed back any excessive pressure to the pump head, or do you have to bypass both fuel oil pumps to avoid an overpressure situation on the functional fuel oil pump?

Regards,
Don_

[tore]

Don.
As the fuel centrifuge was discarded, great care is taken to prevent accidental mixing of fuel and water, hence the double daytank has two purposes 1. Being a buffer placed as high as possible in the engine room to provide suctionhead to the engineattached fuel supply pumps, which are positive displacment pumps.  2.  acting like a settlingtank by being a double tank able to settle and drain the impurities in the tank not in use.
Generally all positive displacementpumps have, contrarly to sentrifugalpumps, a reliefvalve intergrated returning the liquid from the discharge to the suction side to prevent dammage in case accidental shutting the discharge.
The HP fuelplunger pump for each cylinder is a positive adjustable displacement pump having supply from the engine attached supply pump, but  would be able have positive fuelsuctionhead by the highly placed fueldaytank in case of failure of the engine attached fuelsupply pump. The daytank capacity of 700 litres would be able to serve both engines in the highly unlikely event of both fuepsupplyumps would fail.
Tore

[Don Prince]

Hello Mr. Tore,

Are you telling me that all of these scenarios will work?

1. Both fuel oil supply pumps failed and fuel oil will be supplied by one side of the day tank and because of the height of the tank (head pressure) above the bypassed fuel oil supply pump and on to the injectors. I thought there was a problem with the low head pressure from the day tank (i.e., The main reason for the fuel oil supply pump)?

2. Both fuel oil supply pumps failed and fuel oil could be supplied from any external fuel oil tank. The pressure head would be fairly high. The fuel will bypass the day tank because the valve is set in the pass-through position, thus providing adequate fuel pressure bypassing the failed pumps and on to the infectors. 

3. Both fuel oil supply pumps failed and fuel oil will be supplied from an internal fuel oil bunker via the Auxiliary Lube Oil Pump going through the day tank selection valve set in the pass-through position and bypassing the failed fuel oil pumps and on to the injectors...

Regards,
Don_

FYI - From Skizzenbuch page 73 - "If the attached fuel oil gear pump failed and must be by-passed; the pressure head from the gravity tanks height above the diesel engine (image below and less than 2 m WC) is probably not sufficient to force fuel through the filter and supply pipe to the high-pressure fuel injection pumps. Hence, you use the full compensating water pressure from the header tank (some 5 m WC) to provide the needed pressure. The compensating water pressure head goes directly to the fuel injectors supply pipe and by-passes the gravity tank."

[tore]

Don.
The fuelsupply pump can be bypassed by the cock e but have a  knifefilter between the suplypump and the HP pumps which would cause  some resistance which might require a larger head than obtained by the daytank. I have not tested this unlikely event, but would in case of emergency have tried to connect the other engines supplypump before using the compensating water pressure to the daytank.
I am not sure I understand your next question. In case both engineattached fuelsupplypumps fails you would be able to use the separately driven fueltransferpump via the day tank.
Tore

[Don Prince]

Hello Mr. Tore,


While we are still looking for the fuel oil valve chest under the floor plates, Patrick in Germany came across the brackets outlined in the attached photo. Do you remember what was attached?


Regards,
Don_

[tore]

Don. I cannot remember in spite of pondering for a couple of days.
Tore

[Raymic1]

Don
Just wondering. Are you working with Paul- Patrick Schroder or a different Patrick at U995?

[Don Prince]

Patrick Salmen who has a great collection of digital copies of original U-Boat manuals and documentation. He seems to get good access to U-995 and does some volunteer work.


Regards,
Don

[Raymic1]

Patrick Salmen who has a great collection of digital copies of original U-Boat manuals and documentation. He seems to get good access to U-995 and does some volunteer work.


Regards,
Don

Ah OK. I thought it might be Patrick Bateman The Engineer Guy, he also has a lot of original U-boat docs that haven't been published yet.

[Don Prince]

Hello Mr. Tore,

Since 2018 when I released Skizzenbuch, there were 3 websites that I authorized the book's distribution: AMP, The Subcommittee, and Wehrmacht Awards. The latter 2 were able to provide me with a download count, and there was a total of well over 13,000 downloads of Skizzenbuch. In addition, there were about a half dozen pirated sites in Europe and Asia that charged for a high speed download option which was a rip-off! Their initial slowed download speed was taking well over 5 hours, and the high speed download was about 3 minutes (which was about the normal speed from my Dropbox account).

About 6 weeks ago, I decided to look into doing an Amazon.com Kindle publication of Skizzenbuck in a Print Replica format; basically its like a pdf and Skizzenbuch was published on December 6th... I set the price at the minimum charge of $2.99 on the Amazon Website/Kindle Store. I doubt if the royalties will ever cover the yearly cost to maintain the Kristallklar Publishing, LLC, Corporate status in the state of Georgia, the Registered Agent fees, and the initial US Copyright cost. Here is what the Skizzenbuch eBook cover looks like (see the attachment)...

Mark Hessburg was the first person to purchase Skizzenbuch from Amazon's Kindle Store and write a review; now that's a good personal friend...

Regards,
Don_

FYI... I pulled the plug on the free Skizzenbuch download from my Dropbox account.

[Don Prince]

Hello Mr. Tore and All,


Merry Christmas and Happy New Year to All - May we all enjoy Christmas with our families and have a happy and healthy new year...


Kind regards,
Don_

[tore]

Don.
Returning the whishes
Tore

[VIC20]

Merry Christmas.


U 995 Christmas snow mod:

[SG]

Merry Christmas!

[Don Prince]

Hello Mr. Tore,

If you ever had a reason to look at the External Exhaust Flap Valve Casing on U-995; do you recall if it was a single cast casing or three (3) separate casings bolted together Brown/Orange/Yellow (See the drawings)?

Regards,
Don_

[tore]

Don.
I never checked it personally, but based on the general castings on VIICs I would assume such a complicated casting would be three castings bolted together. See image from a IXC.
Tore 

[Don Prince]

Hello Mr. Tore,

Simon and I believe that U-995 would have had the three (3) Sectioned Exhaust Flap Valve Casing because it was a Type C/41 which could dive deeper (They also applied the same External Exhaust Flap Valve to the later Type VII C's as well). So, the Germans installed a shut-off valve between the exit exhaust casing and the 1st section of the Exhaust Flap Valve Casing. The shut-off eliminated any sea water depth pressure from applying excessive water pressure on the internal exhaust water cooling pipes. Remember they did the same thing with a valve to the internal fuel tanks with regard to the compensating water pressure. I believe that Simon has located the shut-off valve in the Diesel engine room upper pressure hull. These construction changes were made to the Type VII U-Boats in the late 42 to 43 period and beyond...

Regards,
Don

[tore]

Don.
As you know we had 3 VIICs in service U995, U-926, and U-1202 the latter 2 were VIICs. U995 is VIIC/41. As far as I remember they were equipped with the same external exhaust system. The external systems were with two external main exhaust flap valves which had a double functions
  1. The outer main exhaust valve being a shut off flapvalve with rotating valvedisk for grinding off carbon deposits on the valve seatings.  This valvedisk was driven by a pneumatic motor in the engineroom with rod extension through the pressurehull to the outer main exhaust valve.                           
 2.  The inner main exhaust flap valve being a shut off valve with a large drain to the bilge, the rotating valvedisk could be manually turned with a wrench on a stubshaft outside the valve casing.
At diving the outer exhaustvalve was shut and the pneumatic grindingmotor started, as soon as we descended through the watersurface we got a sligth back pressure on the valvedisk. When we came deeper the grinding came to a halt at some 4 meter as the back pressure  created a torque larger than the pnuematiq motor could manage. A few times this grinding was not sufficient and we drained the leakwater down to the chamber in the inner shutoff valvecasing and further to the bilges. The deeper we came the higher back pressure on the outer exhaust valvedisk. I cannot recall we ever had to surface because of this system.
When surfacing you know we used the exhaustgases for residue blowing. As there is a limit as to the back pressure the engines can take, as far as I remember the limit was 6-8m wc . This was monitored by the engineers and you had a procedure for not exceeding the back pressure. For controlling the exhaust back pressure the outer mainexhaust valve was used. The low pressure residue blowing (exhaustblowing) followed a certain sequence by starting with the highest ballasttanks and as the submarine ascends further blowing the deeper tanks. A drawback with the pneumatic grinding was the increase of the atmospheric pressure of the submarine and a few time we had to start the E-compresor to get the pressure down.
Tore 

[Don Prince]

Hello Mr. Tore,

Remember several weeks ago...  I was asking about the location of the fuel oil valve chest. Patrick came up with a photo of what looks like a possibility for the location of the fuel oil valve chest. Do these photos trigger any memories?

Regards,
Don_

[tore]

Don.
 A few ideas crossed my mind. There is obviously a difference between the two internal fuel bunkering pipes, the port pipe looks like the original wheraes the starboard having a strange hull valve, the stb strainer is placed under the floorplates and look different from the originals. Having just a quick look it seems that somebody has modified the system to make it possible to bunker from the starboard casing side and  keeping the original port, why? it might be related to the original wintergarden which was removed. Below a simple sketch showing my idea of the current system.
Tore

[Don Prince]

Hello Mr. Tore,


I recall that you said that you never used the saddle tanks for fuel oil storage because you always had access to coastal fuel oil supplies. Did you use Regulating Tank No. 1 for fuel oil, or only the internal fuel oil tanks?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


It looks like the Germans changed the fuel oil side access. The first drawing is from U-570 launched in 1941, and the second drawings is from 1943 (They changed the fuel oil access side)...


Regards,
Don_

[Don Prince]

Hello Mr.Tore,

Patrick came up with a photo where it looks like the Fuel Oil Valve Chest is located under the step coming into the Diesel Room. Does this photo refresh your memory about the location of the Fuel Oil Valve Chest located between his feet?

Regards,
Don_

[tore]

Don,
To me it looks like it might possibly be the valveconnection to luboil storage tank 1 and 2.


Tore

[Don Prince]

Hello Mr. Tore,


Below is what I was thinking...  Your Opinion?


Regards,
Don_

[Don Prince]

Hello Mr.Tore,

Question from Patrick....  Do you know what this is? It's directly behind the speed indicator. Is this part of it? I have seen it on many boats. On the right we have a IX Type Which haves the same.

Don_

It looks like it's a drain for the speed meter to drain any air from the speed measuring system because the air could compress and cause an incorrect speed reading...

Am I guessing correctly?


Regards,
Don_

[tore]

Don, I guess so, On U 995 the pipes for the dynamic pressure which belongs to the Pitot log has its two inlets below the water line on port and stb side of the bow and the static inlet is at the fwd. end of MBT 3. Both pipes goes to the log box on the front of the control next to the fwd hydroplane operator where the speed is calculated and transferred as an electric signal to the repeater in the conningtower. I have a blurred image (Falos) of the installation below.
Tore

[Don Prince]

Hello Mr. Tore and All,


Well, I'm officially 81 years old...  I don't feel that old yet, but time will tell; Ive had two (2) heart stents and it keeps on ticking...


Regards,
Don_

[dougie47]

Hi Don,
Happy birthday to you a few days ago and hope you had a nice day.
Best wishes,
Dougie

[Don Prince]

Hi Dougie,
Thanks for the best wishes...  How is your book doing on Amazon? I have Skizzenbuch digitally on Amazon in the Kindle Store.
Regards,
Don_

[SG]

Belated Happy Birthday Don. 2 coronary stents mean a rejuvenated/healthy heart again!
Keep up the usual, excellent work!
SG

[VIC20]

Happy Birthday Don.
What kind of book is Dougie's book?

[dougie47]

Hi Don,
The book is doing fine, thanks, with perhaps an French edition coming in due course. It is good to see your book on Amazon. I am really glad you used some of my introduction in the information part on Amazon, it has made my day.
VIC20 - My book is about U 47 and Guenther Prien and can be seen here -
https://amp.rokket.biz/books.shtml
I have also been working on an article on Type IX modifications for the last year and hoping to have it finished in the next few weeks.

Cheers,
Dougie

 

[Don Prince]

Hello Mr. Tore,

Patrick Salman (Discord) believes that possibly the Norwegians changed the location of the fuel pump on the GW Diesel Engines on U-995 because they do not match the GW Diesel engine drawings (See Attachment).

The images we have in Skizzenbuch shows the fuel oil pump located forward on the Diesel Engines (Skizzenbuch photo page 71 attached).

Was the location of the fuel oil pump changed by the Germans when the duel fuel filters were installed? Do you have GW Diesel engine drawings that match the changed positions...

Regards,
Don_

[Don Prince]

Hello Website Administrator,


The last email that I got from Mr. Tore stated that he could not login to his account... 


"Hello Don, nice to hear from you, I am still going strong in my 94years I am hoping to show a movie from a demo mission landsetting of underground troops in a norwegian fjord where U 995 took part. It shows some interesting external immages as well as interiors of the boat at that time, including the engineroom. It is made by the norwegian navy only a few month after I left the boat. The movie is of course in black and white but shows some original details from the 1960ties. One drawback though, where to show it ? It last approximately 5- 10 minutes. I dont know what they have done to my mailbox it seems I have been thrown out."

[SG]

Hi Don/Tore,

sorry for the belated reply. A valid option could be uploading the video on an online video platform of your choice (there are many around: https://en.wikipedia.org/wiki/List_of_online_video_platforms ) and share the video URL here on the AMP forum. Don't know what happened to Tore's mailbox, am sure the administrators can fix the problem. Eager to see the video soon!

Cheers,

SG

[Raymic1]

If its the same video it has been linked on here by me before.
I cant seem to link it again but a simple Google search of U995 Kaura Norwegian Navy will find a number of links to the color version.

[Don Prince]

I just got am email today...


"Yes, thank you, I've logged him back in and given him an updated link.
-Tore's Grandson Magnus."

Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Do you remember or have any photos that show the device for measuring the fuel oil drained from the internal fuel oil tanks and the buckets were carried to the diesel room to measure the fuel remaining in the internal fuel oil tanks? Then the contents of the measuring device was drained into the fuel oil collection bunker/tank.

This device seems to be missing in U995.

Regards,
Don_

[Don Prince]

Hello Mr. Tore and all of my very Dear Friends,


This will be my very last Christmas Card on the AMP Website for this year of 2022 to you all. I understand that the AMP Website will be shut down when we celebrate the New Year of 2023. I am so very grateful for the opportunity to have become a friend and a colleague of Mr. Tore Berg-Nielsen and all. Together, over many years of sharing knowledge with Mr. Tore Berg-Nielsen, Maciek Florek (Deceased 2nd August 2017), Simon J. Morris, and Mark Hessburg, I was able to compile their wealth of knowledge and to create the book; "Skizzenbuch: U-Boat Type VII C Project." I started this project as a novice with a steep learning curve because I only had questions and no answers. These friends and contributors were patient with me and answered all of my sometimes dumb questions; for their support I will be forever and eternally grateful. With my bitter sweet memories of long nights working with my colleagues on the AMP Website: Thank you!


Merry Christmas and Happy New Year to all, and many more years to come...

Kind Regards,
Don_

[VIC20]

Merry Christmas to all, too bad that the forum will close 

[SG]

Amen. Merry Christmas Don and all

[VIC20]

Happy New Year to all.
For whatever reason, the forum is still online. Someone must have forgotten to pull the plug.

[SG]

 

[Raymic1]

Yes Dougie can you please leave it up until at least the end of January?
I'm away on Xmas holidays and away from my laptop for 2 more weeks.
I wanted to store some reference info on my laptop before close down...thanks