Tores mailbox VIIC and VIIC/41 operation and technical details

[NZSnowman]

Simon.
On the British report of U 570. You can read an accurate description of the exhaust valvegrinding. The muffler valves are turned by the pneumatic motors, the group exhaustvalves are handoperated and the same is the Junker compressor exhaustvalve.

Tore

Thanks Tore, I had a look.

Tore & Maciek, has anyone see any drawings of the exhaust valve?

[tore]

Simon
I guess you might find some details in your  own photos as this one below. I`ll check for more tomorrow.
Tore

[NZSnowman]

Simon
I guess you might find some details in your  own photos as this one below. I`ll check for more tomorrow.
Tore

I will for sure have more questions for you tomorrow In the VIIC manual it said there are four openings for the Grinding mechanism for the exhaust gas valves stb. and port. I have found 2, now looking for the other two.

[NZSnowman]

Tore & Maciek, can you guys please double check my valves.



Blue = Exhaust gas flap valve, inboard. Valve 'P'. http://www.uboatarchive.net/U-570Plate13.htm
Green = Pneumatic grinder
Purple = Drain valve

[tore]

Simon
Exhaust valves
Below is the normal systemsketch indicating the relevant components. The first valve is the group exhaustvalve which is situated in the peculiar cast steelcasing inside the pressurehull. It is a hinged valve which is "folded down " like a flap. You find a very good photo on u historias exhaustgas page. On this picture you see a square shaft stud marked 4 next to the hinge. On this shaft you put a lever for turning the groupvalve disc. When this valve is shut eg. the valveseats are in contact, you are moving the  handle, turning the valvedisc and thus grinding the valve.
Tore

[NZSnowman]

Simon
Exhaust valves
Below is the normal systemsketch indicating the relevant components. The first valve is the group exhaustvalve which is situated in the peculiar cast steelcasing inside the pressurehull. It is a hinged valve which is "folded down " like a flap. You find a very good photo on u historias exhaustgas page. On this picture you see a square shaft stud marked 4 next to the hinge. On this shaft you put a lever for turning the groupvalve disc. When this valve is shut eg. the valveseats are in contact, you are moving the  handle, turning the valvedisc and thus grinding the valve.
Tore

Tore, I still a little confuse

So on the picture at u historias, No. 4 operate the grinder & No. 2 operate the hinged valve?

[tore]

Simon.
The exhaust valve are operated by two devices, the shutting and the grinding. The valve is hinged and the hingeshaft is operated by a wheel and by linkage turning the shaft and moving the valvedisc to an open/shut position. The circumference of the valvedisc has a bevelled gearrim which meshes a short worm fixed to another shaft inside the hingeshaft. This shaft can be turned either by hand ( group exhaustvalve) or pneumatic motor( muffler exhaustvalve). The worm is always in contact with the rim meaning you can rotate the disc in any position. Unfortunately I don`t have any drawing but have tried to indicate the system on the muffler valve below.

[tore]

Simon
Exhaust valves
Below is the normal systemsketch indicating the relevant components. The first valve is the group exhaustvalve which is situated in the peculiar cast steelcasing inside the pressurehull. It is a hinged valve which is "folded down " like a flap. You find a very good photo on u historias exhaustgas page. On this picture you see a square shaft stud marked 4 next to the hinge. On this shaft you put a lever for turning the groupvalve disc. When this valve is shut eg. the valveseats are in contact, you are moving the  handle, turning the valvedisc and thus grinding the valve.
Tore

Tore, I still a little confuse

So on the picture at u historias, No. 4 operate the grinder & No. 2 operate the hinged valve?

Simon.
I think so.
Tore

[tore]

Simon
Group exhaustvalves
The name sound perhaps a bit strange to you but is a very common Royal Navy term in the submarine service, meaning a device collecting several connections, like exhaust outlets from 6 cylinders (manifold). Down below is a photo showing the  valvewheels in the engine room for the 3 pairs of relevant exhaust valves.
The arrangement deviates a bit from British and US subs as it is adopted for using exhaust pressure for blowing the ballasttanks in semisurfaced position instead of a lowpressure electric blower as the case of other submarines. The muffler valves were used in a semi open position when blowing the tanks in order to adjust the exhaust backpressure. One disadvantage of the system was that the muffler ( dry muffler) exhaustvalve had a tendency to get carbonizes and deposits could be formed both on the valveseating as well as the gear rim and wormwheel, thus blocking the device. As this was mostly common on the mufflervalve a pneumatic motor was fitted  and the valve had to be rotated may be once a watch whereas the group exhaustvalve had a hand turning with handles and ratchets.
As you see the wheels have a bore where you could put a bar giving an extra force to the shutting moment, moreover the group exhaustvalves had a pointer for shut and open 90 degrees.

Tore

[tore]

Simon
As an addition to my last post I should perhaps mention that the engineer having divingposition in the engineroom had a remarkable technique  grinding the mufflervalves  when diving. In order to get a proper pressure on the valve disc he started the grinder some 2-4 meter submerged and got a excellent pressure.  At periscope depth however the pressure was too high and the pneumatic motor stalled. In spite of grinding we had occasional leakages but a proper drain took normally care of that. Once or twice we had to surface due to excessive leakage and a couple of times we flooded the engine via the exhaustpipe. As a rule we never started the engines without turning with open indicatorcocks and more than once water squirted out of the cocks. A disadvantage with using the pneumatic grinder was building up pressure inside the boat, at excessive grinding this could happen.

Tore

[NZSnowman]

All the drain lines seen on Plate 13 http://www.uboatarchive.net/U-570Plate13.htm are within the pressure hull.

So, what is the 'Hull Valve Sea Water' marked as purple used for?

[NZSnowman]

Tore, I try to track the drain piping around the Exhaust manifold but I was not able to Too many pipes in a small area, not enough photo

[tore]

Simon.
 I am not sure I understand your question. U-570 plate 13 is not easy to understand as you have sea coolingwater pipebends, anti corrosionpipes and exhaust drain connection  drawn in the same way. The main drain having connection to the sea is the valve m on plate 16 or o on plate13. This valve has to be open in case of leaking muffler valve.
Tore

[tore]

Simon.
As to my last post I should probably say...or o marked as hullvalve on plate 13.
Tore

[SnakeDoc]

Hi Tore,


I wonder about one thing: on the following image and in the document (http://uboatarchive.net/Manual.htm page 14, table Test data) are gathered engine/motors orders and corresponding RPMs and speed. I suppose, that given speeds  corresponds the orders given to both engines/motors.





 The orders: Kleine Fahrt,  Langsame Fahrt, Halbe Fahrt, Gro