Author Topic: Tores mailbox VIIC and VIIC/41 operation and technical details  (Read 302694 times)

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Offline Raymic1

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3900 on: 21 Aug , 2018, 03:08 »
Ah yes sorry Tore.
I am a member of Ubits Facebook site admin is Boris. He also makes a lot of Metal etch Uboat modelling bits.
Also  I guess that link would not work for non member as you are.
Ill see if I can copy and paste his brief comments.


Offline Raymic1

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3901 on: 21 Aug , 2018, 03:18 »
https://www.facebook.com/ludvig.haga


Mr Tores. Above is his Facebook profile and it was not much of a conversation. But he said he was onboard 59-60 so he may have missed you.

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3902 on: 27 Sep , 2018, 03:09 »
Weathering VIIC

As many of you have noticed I am not in favour of the overdone weathering  on some models. In my time (peace) there was hardly visible rust and damage to the hull which was not repaired as soon as we entered harbour. Major damage to the casing happens to me only once on U 995 where we in the North Sea got some 4- 5 meters on the starboard casing smashed in by the November gale. Below are a few images which might enlighten you on the subject. First of all the most visible part for weathering is the casing and (U 995 wooden)deck. A vital detail is that the deck should be dark grey and one of the instruction from the German High command was always to patch up any damage by the dark grey paint. The reason is obvious, air surveillance.

The casing  is made by galvanized thin metal plating riveted by small rivets using alongship joggle joints as can be seen on my image from an inspection of U-995 I made in 1953. The joggle joint is clearly visible but hardly the rivets, corrosion is minimal.

I enclose my latest paintinting of KNM Kaura ex. U- 995 where I have indicating the normal weathering after approximately 8 months service under rough condition above the artic circle in the Barentz sea.
« Last Edit: 27 Sep , 2018, 13:45 by tore »

Offline karel

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3903 on: 11 Oct , 2018, 06:57 »
Hello everyone!  Hope you have all been doing fine.

I have a question about operating the uboat. I know that the ballast tanks should be either empty or full. Keeping them partially flooded was not intended.
https://uboat.net/forums/read.php?20,91306,91308#msg-91308

This brought me to the question. If there were no gauges that showed the water level of ballast tanks then how did uboat crew member knew when to stop applying compressed air to a ballast tank?
Blowing all the water 100% out of the tanks would be also dangerous since you would produce bubbles? Also the danger of wasting compressed air when blowing an empty tank. How did the ballast tank operator know when to stop blowing?
Did this happen by pure experience or were there any sound cues?

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3904 on: 11 Oct , 2018, 08:03 »
Karel.

Blowing the ballasttanks is done under different circumstances and you are using instruments and experience. F.inst if you want to ascend by ballasttanks from larger depths say 50 meters you use more precious HP air as the counter pressure would be 5 kg/cm2. It takes an experienced controlroom engineer to admit the right amount of air into the ballast tanks which are never blown empty at this depth, the controlroom engineer uses the blowing pressure, the counterpressure ( depth), the time and experience admitting the right amount of air. The aim is just to blow so much air into the the tanks so the submarine start to ascend, then shut the blowingvalve and the air in the ballast tanks expands, forcing out the ballastwater. As the counterpressure reduces it increases the acceleration of the ascend. If you blow too much air into the ballasttanks the tanks are empty before your uncontrolled ascend which is waste of energi, a lot of bubbles and dangerous as the sub break the surface without control. The correct ascend is:  you take the sub up to 14 meter by hydroplanes, make a surface sweep with the periscope and then blow your ballasttanks controlled by checking the depth gauge, stop blowing before completely surfaced, then start the diesels and blow the residue air by the diesel exhaust. The exhaustblowing is done in a special sequence starting with the saddle tanks having the smallest resistance being almost at the surface. You are able to check the counterpressure (exhaust) manometer when the tank is empty but normally you checked when the exhaust escapes out of the Kingstons.
Tore
« Last Edit: 12 Oct , 2018, 05:06 by tore »

Offline karel

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3905 on: 11 Oct , 2018, 08:37 »
Thank you.  Makes sense and it also means i have to cheat for my game project a little since this kind of experience is hard to come to a gamer. Need to think how i can communicate this proccess to a player.  I attached a picture of gauges. These are modelled after photos but i have not yet found a proper source that would identify their purpose. Are you able to tell me what info these gauges presented?

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3906 on: 11 Oct , 2018, 09:23 »

Your image of gauges does not make sense to me, but I assume it is a simplified HP blowing panel for the ballasttanks. I am afraid the real thing is a bit more complicated, but the original design idea is that you have a centralised Xmas tree with a main blowingvalve handle by which you can control all the mainballasttanks. Each main ballasttank has it own valve locally at the pressurehull which really don`t is used in the normal operation, hence it is left open. At the Xmastree you have separate blowingvalves for each main ballasttanks and other distribution valves which I have indicated on my image below, It might look complicated, but it makes a very flexible blowing system which takes time to study. 
Tore
« Last Edit: 11 Oct , 2018, 09:25 by tore »

Offline karel

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3907 on: 11 Oct , 2018, 14:07 »
Tore.

Highly appreceate you taking the time. I studied your picture for couple of hours with additional material that i have gathered over the internet. Gauges on my image are indeed from blowing panel but i understand that i am missing many of them. Looking closely at other pictures i can see additional gauges between some valves. I decided to dive deep into the subject and try to understand as much as possible. This will give me best option to decide how to represent similar level of control in the game. I am not aiming for super  1:1 realistic but i do want the game system to feel authentic and somewhat believable.

I should start from the basics. Do i understand this correctly that air compressor was used to fill HP banks 1-5 with air? These banks were connected to HP air distributor. From there the air was distributed between ballast tank blowing distributor and LP air distributor.  Hope it is ok if i keep my questions short and go forward from there step by step. As every answer gets me a step closer to understanding this complex system and will help me form my sequential questions better. 

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3908 on: 11 Oct , 2018, 14:32 »

Karel. 
Below is the VIICs HP air system with the total air vessels for HP air storage, inside and outside the pressurehull. The scheme is a bit old as you have two conventional compressors, the normal VIIC execution had the Junker free piston diesel compressor replacing the conventional electric compressor on the starboard side in the aft torpedo room. Sorry for the many arrows crisscrossing the image.
Tore

Offline karel

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3909 on: 12 Oct , 2018, 02:10 »
Tore.

Can you tell me where it was possible to read the data on how much compressed air was left into HP banks? I cant seem to locate the placement for these gauges.  If i had to guess then i would say they are near the HP air distributor where the lines were connected to the banks.

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3910 on: 12 Oct , 2018, 02:54 »
Karel.
The hp air capacity was monitored by the pressures for each vessel to be read at the air distribution rack, never the volume. The volume could of course be calculated acc. to Boyle Mariottes law, but was never done. All the storage airvessels were never connected to the distribution rack at the same time, only a few for normal use. One of the problems for blowing exstensively is of course the expansion temperature which might lead to ice formation at the blowing valve being used extensively so you had a limiting factor as to using this valve.

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3911 on: 12 Oct , 2018, 02:58 »
Karel.
The total capacity of the HP air banks is 3.900 liters at 205 kg/cm2

Offline karel

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3912 on: 12 Oct , 2018, 09:31 »
Tore.

The HP and LP distributor both have a drain valve. I cannot find any good explanation about these. What are they for exactly? Draining water? From where?

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3913 on: 12 Oct , 2018, 10:07 »
Karel.
When you are running a compressor you always collect water from the humidity in the air, particurlary on a submarine where the humidity is high. In view of the previously mentioned freezing at air expansion it is a good idea to keep the air ar dry as possible.
Tore

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #3914 on: 12 Oct , 2018, 22:19 »
Hello Mr. Tore,


When using the Exhaust Manifold Blowing Valves in the control room would the proper blowing order be:
1. Blow MBT 1 and MBT 5 the highest tanks with less back pressure
2. Blow FBT 2 and FBT 4
3. Blow MBT 3 being the lowest tank with the greatest back pressure


Would there be a drop in the back pressure which would tell the crewman the tanks was blown, or could the crewman hear the gases escaping and know the tanks were blown?


Regards,
Don_
A man’s got to know his limitations…
Harry Callahan, SFPD