Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.
The Junker dieselpiston crowns were attached to the 1. and 4. stage compressor piston on one side and 2. and 3. stage piston on the other side. As the diesel piston crowns are in direct contact with the combustion and as such are exposed to substantially higher temperatures than the compression pistons they have to be of another alloy hence the separate pistoncrowns. For normal maintenance you did not have to disconnect the pistoncrowns. However the freepiston compressor was very susceptible to carbon deposit due to balancing. A clean Junker compressor could hang in a wire and run with not much movement, but in excess of 50 grammes unbalance would be almost useless as far as I remember. The piston have normal pistonrings a total of 4 and not sleeves.
Tore

[tore]

Don.
Your question on "piston sleeve". As you might know the conventional engines have conrods and crankshaft which create sideforces on the cylinder walls by the combustionforces on the piston. Smaller (and lower) engines are designed as trunk engines where these forces are distributed to the cylinderwall by the so called pistonskirts of the trunkpiston. On larger diesels  as large bore mainengines for ships, you have cross headengines where the sideforces are absorbed by the separate lubricated crosshead being a slide (shoe) outside the combustion cylinder and where the conrod is connected. However on a freepiston engine having no conrod and crankshaft there are no combustion sideforces. This is the big advantage of a freepiston engine, you avoid the friction of the side forces and the rotating parts, the elimination of the friction creates a higher mechanical efficiency and a more compact engine.
Tore

[tore]

Don.
Following up my post of February 19Th I am posting an image  below showing the air inlets to both the 1st. stage compressor and the combusting / scavenging air intake.
Tore

[Don Prince]

Hello Mr. Tore,


The drawing does not match up well with the photo.  The savaging air filter looks to be attached to a cast manifold.  I guess the cast manifold could wrap around the back and make the connection at the bottom. The drawings indicate the savaging air intake is on the lower part of the compressor 1st stage.


In the photo there are two lines that are attached at the top; one on the forward casting air inlet 4th stage, and the other one is on the compressor 1st stage the 1st stage air outlet (or a cooling water outlet)?  Your bottom arrow is pointing to the 1st stage compressor air inlet which is at the casting location but internal beyond the 4th stage casting???


I believe the line near the red arrow is the cooling waterline to the 4th stage, and the smaller line goes to a pressure gauge (4th stage pressure?)....


How wrong am I...


Regards,
Don_

[tore]

Don.
No, it does not match as the sketch is possibly made by the Kobe people and differ slightly from the Junker installed in the VII Cs. It was the best I had for showing the working principle of the Junker compressor.
I have made an image of the Junker installed in U-995 and making reference to the Kobe steel drawing for localizing the various pipes. You`ll see I have removed the scavenging inlet port and the first stage inlet as they don`t match the Kobe steel execution. I assume it is hard to localise the 1 stage outlet pipe and guess it could be a pipe underneath the compressor entering the 1. stage cooler situated under the compressor and placed at the casing at the same distance from the left end as the coolingwater entrance.
Tore

[Don Prince]

Hello Mr. Tore,


I'm not too concerned about the differences in the junkers compressor as such.  If you look at the Junkers compressor that was installed in U-570; it looks very different as well...


Regards,
Don_

[falo]

Hi Tore,

I have a question about the antennas (please see the two attached pictures) of the conning tower. If you see my red circles and arrows you know what I mean. My question now, is this the accurate late war style to connect the antennas with the conning tower of a (late) typseven/41?

Thanks in advance
Falo

P.S.: I have caught the two pics from my photo report thread about U995, there are also some more conning tower pictures where you can see the antennas from a different angle if necessary for you.
http://models.rokket.biz/index.php?topic=1150.0

[tore]

Falo.
I am really not fully conversant on this matter, but to me the museums U-995 antenna arrangement seems a bit odd. I know there were different solution, but to my knowledge the most common arrangement would be to let the antenna enter a steelpipe into the wintergarten  on the later VIICs and on the aft conning towerplatform on the earlier. Posting a few photos including one of KNM Kaura to illustrate what I mean.
Tore

[NZSnowman]

Hi Tore

Here something I am sure you have see before

http://www.ebay.de/itm/U-Boot-Steuerbord-Maschinentelegraf-aus-Typ-VII-U-Boot-Bj-1944-selten-/231487213511?pt=Militaria&hash=item35e5b68fc7

Some great detail photo's

[falo]

Hi Tore, thanks for the quick information and the pictures. By seeing them now the U995 antenna solution looks really a little bit odd.


Thanks again and regards
Falo

[VIC20]

Hi Tore

Here something I am sure you have see before

http://www.ebay.de/itm/U-Boot-Steuerbord-Maschinentelegraf-aus-Typ-VII-U-Boot-Bj-1944-selten-/231487213511?pt=Militaria&hash=item35e5b68fc7

Some great detail photo's

Just 2999,-? A steal ;-)

[NZSnowman]

Hi Tore

Here something I am sure you have see before

http://www.ebay.de/itm/U-Boot-Steuerbord-Maschinentelegraf-aus-Typ-VII-U-Boot-Bj-1944-selten-/231487213511?pt=Militaria&hash=item35e5b68fc7

Some great detail photo's

Just 2999,-? A steal ;-)

OK, it look to me if we all put in $5 for the next 20 years, we should be able to build our own Type VII.
 
All we need to know who has the biggest backyard and how near is it to the sea 

[Capt Kremin]

 

[VIC20]

OK, it look to me if we all put in $5 for the next 20 years, we should be able to build our own Type VII.
 
All we need to know who has the biggest backyard and how near is it to the sea 

Someone is funding his Bf-109 Replica by building each part several times and selling the spare parts on ebay.


https://www.facebook.com/pages/Arsenal-45/129889520415326


http://www.ebay.de/itm/Rumpfteil-1-oben-Messerschmitt-Bf-109-G-/400859893995

[tore]

Simon.
Your excellent photo of the original enginetelegraph revealed perhaps one of the ways they are financing the maintenance of the poor old U-995. By the prices you achieve for old original parts no wonder why the original gauges like the depthgauges has disappeared. The photo of the engine telegraph is most probably the original telegraph for stb E motor as you see the encircled field "Laden" is on the right side. Moreover it says MT (E-motor) stb. The original telegraph in the controlroom has the astern scale on the left side and no MT. In fact if you compare the enginetelegraphs both in the controlroom and E-room you may see they are on present days U-995 exchanged by new ones deviating from the originals which can be easily identified by the outer dialrim having "dents". So all the engine telegraphs have been "nicked?"and substituted by new. 4x2999,- makes app. 12.000,- Euro a lot of temptations to remove the original parts not so good for the museumsvalue.
Tore