Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don I just had a look at U-Historias image of the GW mainengine front nearly a same image as below. U- historias image marks my assumed exhaustvalve lubrication point as no 14 saying this is " tubo de engrase valvula" I am not very conversant with the spanish language but I assume U Historia is of the same opinion as me. May be we can draw a conclusion.
Tore

[Don Prince]

Hello Mr. Tore,

I translated the u-history.com comment to "grease tube valve"... "Google Translate" looks to do a good job translating many languages and the source/destination language has many different combinations.

It looks like the GW Piston has no internal lube oil cooling ability. However, the GW piston has 7 compression rings and 2 lower oil control rings. Where the American GM piston design only has 4 compression rings and 2 lower oil control rings. Interesting....?

Regards,
Don_

[Don Prince]

Hello Mr Tore,

I FOUND IT!!! U-Boat Archive Series Volume 7, Report on U-570 - H.M.S. Graph - Page 70

Main Engine Liner

"Cylinder lubrication is by means of a Grutzner pump with tow connections to each liner, inboard and outboard. There are no oil groves cut in the liner walls and no holes are provided for piston slinging gear."

Main Engine Pistons

"They are fitted with 6 impulse rings, 1 upper scraper ring and 2 slotted scraper rings, Drain holes are drilled behind the 2 lower scraper rings and also in the oil catchment groves. The groves, 2 in number are situated immediately below each slotted scraper ring."

Don - Therefore, it looks like pump connection is situated so that the nozzle will always be in between the 7 top piston rings (compression rings) and the 2 lower scraper rings (oil control rings).

Exhaust and Induction Valves - Page 72

"The stems of both exhaust and induction valves are lubricated by a mechanical pump driven from a camshaft'"

Connecting Rods - Page 71

"The connecting rod has a large diameter bore through it, being reduced near the eye of the rod. The lubricating oil is taken round the gudgeon and fed through the pin through 4 holes at 45 degrees above and below horizontal."

The only thing that I'm not sure of is how are the rocker arms lubricated, Is the above describing how the rocker arm pivot point is being lubricated...?

Regards,
Don_

[tore]

Don U-570 ex HMS Graph  was a VIIC built by Blohm & Voss and the main engines were MAN m6v 40 46 type being turbocharged and a different construction than the GW engines. Although they did the same job. The MAN design was a bit more "advanced" than the GW engine  but the latter was considered to be more reliable.  Sorry I don`t think we can compare the details of the GW engines with the MAN.
Tore

[Don Prince]

Page 64 - two sets of GW 4-cycle engines built by Blohm & Voss under Krupp License at Hamburg...


Don_

[tore]

Don
You are absolutely right, U 570 was equipped with GW engines, I did not checked the British report but the US report of september 28th 1941, classified reliable, and made by 3 US naval officers who was onboard inspecting the submarine U570  23.- 26. september 1941 at Hvalfjordur Iceland. Obviously not very reliable as they say on page 51 section II-C-  2 :" Main engines   The two 6 cylinder, 4 cycle, solid injection M.A.N engines are rated at 1400 horsepower each at 470 rpm with supercharger cut in........" I should of course had been a bit suspicious on the cut in expression. But in a hurry I just noted the MAN. So much for reliable source, sorry Don. I guess we possibly could accept the cylinder lubrication by the GRUETZER lubricator and leave the in lubrication of the fulcrums to the manual greaser I am a bit bewildered on the valvestem lubricator driven by the camshaft.  For easy access to the fulcrum lubrication  on the top a foldable step was arranged along the engine. as shown on my image below.
Tore

[Katuna]

Ahem...


https://models.rokket.biz/index.php?action=dlattach;topic=1621.0;attach=11906

[Don Prince]

Hello Mr. Tore,

The GW Diesel engine design had no top valve cover... Was there any maintenance procedure where the push rods and valve rocker arms which were exposed to the engine room were lubricated? Were there any grease nipples located on the GW Diesel engine?

I have attached 2 charts:
<1st chart is the GW Diesel engine crank shaft and ignition timing>
<2nd chart is the Lubricator injection and the GW Diesel engine stroke timing>

Regards,
Don_

[tore]

Don, I don`t think we had any fixed lubrication instructions for the many fulcrums and contact points on the top of the engines. As mentioned the technology was pretty much based on pre WW2 practise and local manual lubrication was the custom. I guess you are able to see the lubrication points on the tops of the valve rocker arm on the enclosed image below. There were no greasecups on this point as far as I remember an oildrop was added at regular intervalls to the engineer/greasers judgement. The manual point lubrication was an important time consuming part of the engine crews watch. To day I am afraid that many layers of fancy paintings are hiding the many lubricating points on the top.
Tore

[Don Prince]

Hello Mr.  Tore,


The attached photo looks to have captured the lube point for the valve rocker arm...


Regards,
Don_

[tore]

Don. I am afraid it might be a bit more complicated than indicated on your image. I guess your yellow arrow is pointing at the setscrew (locking) for the pedestal shaft and thus fixed to the pedestal. The rockerarm is pivoting on this fixed shaft and hence need lubrication which is admitted via a wart on the rocker arm. Usually the fulcrum shaft is locked and the arms are pivoting. The shafts are usually locked in the support either by segerings or setscrews, the latter can easy be mistaken for a lubrication wart as the threaded boring is in a wart similar to the luboil bore. My image below explain what I mean.
Tore

[Don Prince]

Hello Mr. Tore,


New terminology for me... "Lubrication Wart" is this a raised circular area with a hole in the center going down to a shaft that needs lubrication? Since these are rocker arms, would you use grease rather than lube oil because of the constant up and down motion that may sling a lube oil out of the "Wart." Or, does the Wart have a cover?


Regards,
Don

[tore]

Don.
 I guess warts on engineparts is not proper english for the extra materials needed for bores with or without threads primarily on cast steel /iron. Not always used for lubrication, but bores for setscrew, drainplugs etc. Grease need pressure to get to the lubricating points hence mostly luboil is used. Proper lubrication of a dieselengine having an open top was difficult before the topcover was introduced. The time consuming pointlubrication  was one thing, another was the drains from all these points which you didn`t like to get in to the bilges. Hence an elaborate system of funnel and small drainpipes was installed to take the drain from the top. The system was susceptible to damage especially during maintenance.
Tore

[Don Prince]

Hello Mr. Tore,


I noticed that the Selector Valves for air distribution in the Diesel engine room were both painted red on U-995, even though they look to be on the port and starboard side. Is red the original color for both valves?


Regards,
Don_

[Don Prince]

Hello Mr. Tore and All,

Merry Christmas and Happy New Year; Wishes for a Peaceful New Year and Lasting Friendship!

Kind Regards,
Don_