Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore,

I have been able to figure out some of the circuitry on my own after several hours of study...

Regards,
Don_

[tore]

I have been briefly looking at the large scale models of trumpeter modelkit and am impressed about the ambitions rather than the results of the kit maker, it is however impressive what some of the modelbuilders have achieved. My memories goes back to the days we were crawling under the floorplates trying to figure out  how things worked without any drawings or manuals in the first years. The way some of your guys are able to model the piping system is awesome. On order to have a correct system it helps to know how it works and below is an image of the lubeoil system up front of the port engine of U 995 having a non reversible GW engine without lubeoil purifier (sentrifuge) .
The system works as follows: Each engine has a dry oilsump with 5 drainages to a common drain pipe leading to a double valve cage being able to select port or stb system tank. The attached gearpump up front is able to operate in two turningdirection (a complicated rudiment from a direct reversible engine) takes suction via a suction valve from the relevant systemtank to the suction side of the pump, before entering the pump is a smaller branch pipe with valve to the discharge pipe and from the discharge of the pump is a small pipe with reliefvalve to the engine drain pipes.  The dischargepipe has a thermometer and then a NR valve before entering a valvecage having connections to port filter and cooler, stb luboilsystem and the emergency lube oilsystem. The cooler has on the top a venting pipe with cock, the ventpipe ends in the common main drain pipe of the engine.  The cleaned and cooled lubeoil leaves the cooler via a three way cock enabling connection to port engine, stb. engine or bypass. After this cock is a branch of pipe ( full pressure) to the governor servo motor (aft of the engine) which has a drain to the common drainage pipe. The main lubeoil pipe now passes very visible the front of the main engine where a pressure reduction valve is situated reducing the oil pressure from 3kg/cm2 to 1,5 kg/cm2. Then a thermometer (in mainengine) before branch off to the various components of the engine like main bearings, register drive, turbocharger etc.
Tore

[tore]

Don.
I recall we discussed the turning of the VIIC main diesel, I guess in connection with the Skizzenbuch, at that time I couldn`t remember exactly where you engaged the turning bar on the engine. I just discovered an image showing the item as shown below. The manual turning of the main engine was always necessary during maintenance and adjustment, furthermore we always turned the engine manually with open indicator cocks in the event of water intrusion to prevent waterstroke. As you shall see from the image the turning bar system was identical to the main clutch and engaged a "disc" just before the dieselclutch. 

[maillemaker]

Hello Mr. Tore,
The pictures are fascinating.  I love seeing them.
Were the stanchions/handrails on deck added post-war?  Did they stay on when submerging?
Thanks,Steve

[Katuna]

Tore - You are absolutely right about knowing what the components are, how they work in conjunction with each other and how the piping and electrical is laid out in regards to modelling. While Trumpeter did an admirable job of creating a cutaway model, they left an enormous amount of detail out. Those of us that have an inner masochist have decided to twist the knot a little tighter everyday by trying to convincingly recreate as much of the intricate detail as possible.


I grumble about not having a certain drawing covering the specific area I'm working on at any given time. I can't image how you actually operated without any manuals. When men were men.

[tore]

Hello Mr. Tore,
The pictures are fascinating.  I love seeing them.
Were the stanchions/handrails on deck added post-war?  Did they stay on when submerging?
Thanks,Steve

Steve, the stanchions and railing were originals, surfaced and submerged, however they were easy removable. For war patrols, and exercises they were removed as they were ratling quite a bit submerged.
Tore

[Don Prince]

Hello Mr. Tore,

I believe I figured out how the Rudder motor drive circuit works, and here are the other 2 options for the circuit...

Also, the exact same electrical devices were in the Type VII U-Boats. However, the Type VII electrical diagrams only showed small boxes and not the internal details. In fact, the Type VII electrical schematic did not even identify what the boxes were... Go Figure!

Regards,
Don_

[Don Prince]

Hello Mr. Tore,

Manually cranking the diesel engine: I figure at most only 3 cylinders would be flooded because the exhaust valves would have to be open to allow water to enter (Some stage of the exhaust stroke). If the engine were manually cranked, then some water would exit the exhaust valves into the exhaust pipe and could be drained into the bilge (besides the exhaust test valves)? Does my drawing look anywhere close to being correct?

Regards,
Don_

[tore]

Don.
Your drawing of the turning device is excellent.

I guess the flooding normally is due to leakage of the outboard main exhaustvalve just before the silencer. The valve has a rotating valve disk driven by a pneumatic motor grinding the carbon deposit from the valve seats. This was carried out at regular intervalls running surfaced and as a routine during the diving procedure, the grinding was stopped when the sea pressure became too excessive. Sometimes (not often)this grinding when diving was incomplete due to lack of time and a substantial leakage could occur. When the leakage exceeded the internal draining capacity, flooding happened and water intruded the hull main exhaust valve casing, this valve is susceptible to carbonizing as well and leakage leading to flooding of the exhaust manifold alongside the engine. The manifold has a considerable drainage capacity hence the flooding was very short, but I guess in that short time all the exhaustvalve ducts in the cylindercover were filled and could not be drained by the exhaustmanifold drain. Hence some water was trapped in the cylinderhead exhaustducts. When turning the engine by hand you opened the  exhaust valves and drained this water into the cylinders. In order to get rid of the water could either blow it out by starting air through the indicator cocks running the risk of turning the engine uncontrolled by air with a possible risk of waterstroke or by cranking bar sqeezing the water out through the indicatorcocks by the piston.

Tore

[Don Prince]

Hello Mr. Tore,

I actually had a photo of the diesel engine manual cranking dogs, but I missed then right in front of me nose...

Regards,
Don_

[Don Prince]

Hello Mr. Tore,

After reviewing my Uboataces DVD I believe I found one of the Self-Starters for the Rudder or the Hydroplane control circuit in the Aft Torpedo Room. What do you think?

Regards,
Don_
 

[tore]

Don.
I am a bit rusty on this item, but I guess it is OK.
Tore

[Don Prince]

Hello Mr. Tore,

Does my comments make any sense about the Hydroplane control circuits?

This hydroplane drive system schematic for the Type IX U-Boat look very similar to the lower half of the Type VII schematic. However, the difference is the Type IX actually had the emergency steering unit. The extra BBC unit was mounted on a pedestal directly behind the hydroplane operators in the U-Boat control room. Notice the bow torpedo room self-starter box has a heater circuit and the stern/aft self-started box does not have one. However, the stern/aft self-starter box does have serial resistance (Ns Vorwiderst) added to the hydroplane motor shunt circuit which could act as a heater, and the current flow is decreased in the aft hydroplane shunt coil; more power for the aft hydroplane motor? For example, the U-Boat is running forward and coming to the surface at a horizontal position; the bow hydroplanes up angle determines the rising angle and the aft hydroplanes down lift the back of the U-boat to keep it level (This circuit may only apply to Type IX U-Boats). In addition, the hydroplane motor circuit has a series resistor for the purpose of displaying the Amps drawn.

Regards,
Don_

[tore]

Don.
The title of your book is Skizzenbuch: U- boat type VIIC Project, hence I guess it is correct to make it very clear to the readers when you introduce a IXC topic in a VIIC publication to prevent confusion and misunderstanding. Allthough there are many components of the same design in the two submarines types, they are different and mixing the two in your book might lead to confusion to the layman.
Tore

[Don Prince]

Hello Mr. Tore,

My questions:
1. Coming from depth to 20 meters - Would the captain bring the U-Boat up at a forward angle up, or the U-Boat up while positioned horizontally/level? I would think at a forward angle up for expediency.
2. Going to periscope depth from 20 meters - The captain would want the U-Boat level when going to periscope depth because he would not want a bow up angle.
3. At periscope depth - Take on some water ballast and make the U-Boat heavy, and use the forward and aft hydroplanes up position and maintain a horizontally level U-Boat at depth with a low periscope exposure.
4. Speed at periscope depth - I would think a higher submerged speed would provide the captain with greater control of the periscope depth exposure.

Regards,
Don_

I agree with you; I do not want to introduce U-Boat Type IX data into Skizzenbuch for the Type VII U-Boat. Since the Type VII U-Boat electrical circuit data is not detailed, then perhaps some of the more detailed Type IX electrical information applies to both U-Boats. If the above questions applies to both U-Boat types, then perhaps the electrical designs apply to both U-Boats as well? Fortunate for me, you are a very rare resource over 90 years old with actual Type VII U-Boat experience. I'm no spring chicken at 78 years old either. My area of expertise was electro mechanical equipment and the electronics (tube and solid state) of the past generation. I may ask questions beyond your area of expertise or responsibilities as the EO of Kaura, but there is no one else left to ask... Congratulations!!!