Tores mailbox VIIC and VIIC/41 operation and technical details

[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