Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

I'll guess anyway...


Perhaps this?


Don_

[tore]

Don.
The endstopper controlshaft is driven by a  system from the IMO converter having rotating pto from the drive spindle via a worm gear, with ratio, engaging a gearwheel, with ratio, all reducing the rotating movement which is then transmitted to the endstopper via a chaingear, again a possible rotation reduction. I don't have a drawing of the system, but I post a sketch of the system below. As you see, apart from the internal threads in the endstopper slide there are several reduction elements in relation to the periscopetravel. As it is only an end stopper and not an indicator it does not need to have a big movement.
Tore

[tore]

Don.
Your Skizzenbuch.
On page 168 you are stating: However the U-boats does take on the dynamic diver characteristics when it surfaces with the ballast tanks flooded and used dieselexhaust to blow the ballast. To remain surfaced at that time, diesel power and diveplane upward angle is used.
I am afraid it is a bit different. Normally the VIICs are surfaced by taking the boat up to periscope depth by e-motors and hydroplanes, the ballast tanks are still filled with water and you have normal neutral buoyancy. Then the CO takes a periscope sweep and if everything is OK he  gives the order surface and  the ballasttanks are blown by compressed air. You don`t surface the boat by hydroplanes. At a given point in surfacing the boats metacentric height is reduced and the boat becomes a bit unstable. Depending upon the sea and the submarines relative position the CO evaluate the situation before he orders stop blowing. The reason for this procedure is that you don`t want to be hit by a major wave sideways when you are in an unstable condition hence the degree of airblowing (surfacing) is determined by the circumstances mentioned. When the submarine has semi surfaced to the wishes of the CO, he enters the bridge and if everything is OK he gives the order to start the diesel and blow the residue ballast water by exhaust. The use of diesel exhaust to blow the ballast tanks is to save HP air. You may start the other diesel for propulsion to keep the submarine up against the sea.
Circumstances in wartime might require deviation from the above procedures.
Tore

[Capt Kremin]

Hi Tore


Just to change to subject slightly, external torpedo storage containers, did any of the Norwegian boats still have them?, were they used at all?, if either, did they have a pressure line going to them or were they just a waterproof container?


Regards
Jon

[tore]

Jon.
I believe they were removed on all the boats as well as some of the casing deck containers.
Tore

[Capt Kremin]

Hi Tore,


Thanks for the reply


Regards
Jon

[Don Prince]

Hello Mr. Tore and Maciek,


1.  I added two pages 160 -161 with photos & info about the exhaust blowing manifold valves per Maciek.
2.  I deleted some info about surfacing per Mr. Tore and added info on page 163
3.  I added corrected info about rudders and hydroplanes 170 - 177
4.  I added corrected info periscope hydraulic drive on pages 217 - 225
5.  The schnorchel section is at pages 330 - 337 (I believe it has been checked out?)


Skizzenbuch has grown to 349 pages, so I had to renumber the pages in my 3 Word documents and re-merge them into a single PDF file.  Sections have different page numbers every time I make additions and the additions have to be two pages so the Plates end up on the right side of the book and on an odd page number..


However, I welcome any suggestions or corrections because I what to get Skizzenbuch right!  I have loaded the latest version of Skizzenbuch into dropbox... 


Kind regards,
Don_

[Don Prince]

Hello Mr. Tore,


The ratchet and anti-backup pawl looks to give the crewman the possibility of raising the periscopes manually.  However, I do believe the drive shaft must be disengaged during a normal hydraulic wench operation.  How is this done?


Regards,
Don_

[tore]

Don.
I have looked briefly through you Skizzenbuch (13) edition and have a few remarks related to the exhaustblowing of ballasttanks. As you might have noticed, the HP air hullvalves for blowing the ballasttanks have a non return valve  or check valve as you would say, integrated. The exhaustblowing valves have not, and that calls for some care, otherwise the ballasttanks might be vented through the exhaust system. Thus when you start exhaustblowing you first start the diesel the conventional way by having the inner and outer exhaust flapvalve fully open, then you adjust the pressure to 0,5 bar before you open the main exhaustvalve to the distributionpanel operated from the controlroom. Just to be sure no venting shall occur.
As the internal pressure varies in the different tanks f.i. MBT3 require a higher pressure than the saddle tanks, you blow the tanks separately otherwise the exhaust, taking the flow where you have the least resistance, shall escape. Thus the exhaustblowing is a timeconsuming affair. By the HP airblowing you don`t get the same problem of escaping air, as you normally don't empty the tanks fully  allthough you might have more residue water in the tank having the highest resistance.
I`ll look into the other questions later.
Tore

[Don Prince]

Hello Mr. Tore,


Previously we said the blowing pressure was 1.5 atm which would be equal to 1.5 bar.  Is it OK to use 1.5 bar?


Regards,
Don_

[tore]

Don.
Yes, when the VIICs were at their top the German pressurenominations were  ata which means atmospheres absolute and atu which means atmospheres over. Bar is still used by my generation, but is not correct, barg is more precise meaning atmospheres gauge.  The manometers on a VIIC  usually have a scale starting at 0 meaning the atmospheric pressure. The problem is that the prevailing pressure in the confined space of a VIIC was seldom one atmosphere, usually over or when schnorcheling under. You should compensate for that by having differential pressuregauges as we have discussed before. However in the mannor of speaking amongst the crew talking about pressure, we always meant pressure above atmospheric and 0.5 bar is actually 1,5 bar absolute. The time correct nomination for the VIIC pressures would be exhaustpressure should be adjusted to 0,5 atu or 1,5 ata.

Tore

[SnakeDoc]

Hi Gentlemen,

I have few words related with the hydraulic system and the diving planes.

Although most of type VII U-Boats were equipped with the diving planes driven by electric motors (as thoroughly discussed above), there were two boats, which were fitted with the hydraulic drive of the diving planes for experimental purposes. These boats were U 206 and U 207. I have no details about experiences related with this drive, but one can suppose, that electric motors driving hydroplanes were replaced by the hydraulic motors (the same as for periscope drive) controlled by pilot valves at diving planes control station.
What was the purpose of usage of the hydraulic drive - one main reason would be noise - the hydraulic drive would be quieter than electric drive.

The type XB U-boats (minelayers) were also equipped with the diving planes driven hydraulically.

The concept of the hydraulic drive was elaborated by Germans in the type XXI U-Boat, where not only periscopes were operated hydraulically, but also torpedo tubes muzzle door opening gear, torpedo reload system, forward diving planes retracting gear and finally diving planes and main rudder drive.
There should be noted, that in this case, the diving planes (and main rudder) were driven not by hydraulic motor (and then by worm gear), but directly by hydraulic pistons/actuators.

--
Regards
Maciek

[SnakeDoc]

Tore,

to continue the topic of the diving planes and hydraulic systems - in the US Navy, the Gato and Balao type submarines were equipped with the diving planes driven hydraulically (by means of the pistons/actuators). I have found no information, what was the British practice - could you present how it was done in British way?

--
Thanks, regards
Maciek

[tore]

Maciek.
Limiting my experience to V, S, T and A class British submarines I would say they used by far more hydraulics than the Germans. Apart from the periscopes,- the hydroplanes , rudders, vents and Kingstons were operated hydraulically even the capstans and windlasses. They had different hydraulic actuators depending upon the movement required and they made use of rams pistons f.i. on the vents required relatively small movements, IMO converters and VSG unites were widely used as well. For the hydraulics used outside the pressure hull the oleo systems were used. The oleo system is converting the energy transmission fluid from f.i. hydraulic oil to glycerin omitting the risk of oilslick in case of leakages. When you operated a British submarine you got the impression of a very modern vessel whereas the VIIC was a sturdy oldfashioned full of mechanical rods and gear vessel. Yet the VIIC gave a good feeling as you had direct mechanical contact with the elements you operated.
Tore

[Don Prince]

Hello Mr. Tore,


If we connected a pressure gauge that reads 0.0 bar based on the internal hull pressure as a reference, then the blowing pressure read on the pressure gauge for the blowing manifold would be 0.5 bar?   The absolute pressure would be 0.5 bar, plus 1 bar for the atmosphereic pressure, or 1.5 bar?  That seems confusing...  I would think that the exhaust pressure should be expressed as what is measurable with a pressure gauge.


My question is what pressure does the engine crewman adjust the blowing pressure to when viewing his pressure gauge?  0.5 bar...  Is this the gauge ? (see attachment)


Regards.
Don_