Identification of engine diagrams

[VC54002]

Hello
After hours of looking for a place where someone could have a clue as to what this engine was used for or what it was a part of I rembered about this forum which for some reason wasn't the first site that popped into my mind since I usually visit it to identify equipment.

Anyway, what I'm trying to identify today is an engine represented in a diagram that I found in a rather unusual location; An abandoned military base in southern Spain used for storing naval ordnance and german naval mines which were stored after the war. The diagram is in very bad condition but at least most of the information is visible. I am mainly interested in finding out the model of the engine and where it could have been used, here are the images:

This is the first half of the diagram showing the crankshaft and the phases of the engine


This is the second half, showing the cylinders and the list of all the components of the engine


And here is the entire diagram showing the engine


I am really thankful to anyone who looks into this and provides any kind of information about it.

[Natter]

It's a torpedo engine - the german G7a(TI).
It differs in minor details from the drawings in M.Dv.Nr. 358A Torpedo G7a Zeichnungen from 1941, so it probably shows a later version (the G7a engine went through a couple of redesigns since it's first version around 1930).

Spain received both G7a(TI) and G7e(TIII) from Germany in 1943 as a result of Program Bär (it also included supplies of other types of weapons).

I have attached a couple of drawings from the spanish G7a-manual, showing a very similar engine-version as your drawings (taken from Description del Torpedo 'G-7a' (Láminas), 1946).

[VC54002]

Wow, thank you very much, I knew this was the right place to ask. In addition to the diagram of the engine there also are diagrams of various different machines but they are in worse conditions, I suppose these are also components of the torpedo but some info about them would be appreciated. If you are interested I can post all the diagrams

[Natter]

I suppose these are also components of the torpedo but some info about them would be appreciated

See notes on attached image.

If you are interested I can post all the diagrams

I'd be very interested to see all the drawings, as they differ from other drawings found in german manuals (I suspect these probably have been used for educational purposes, hence the colours...).

Ideally, it would be great to have proper highres scans though if that's possible? I'd be happy to trade you scans of the spanish manuals in return.

[VC54002]

Ideally, it would be great to have proper highres scans though if that's possible? I'd be happy to trade you scans of the spanish manuals in return.

Yes, I've already been working on scanning the diagrams and I should be done with them in about 2-3 days. When I'm done scanning them I will contact you and send you everything. Also I would be very interested to take a look at the spanish manual or any other information you have since I've just started reading about the history of these weapons and it's really fascinating, we can talk about that when I contact you after I finish with scanning.

By the end of this month I will most likely go back to the place where I found the diagrams and I will focus on searching every corner of the offices for more documents, the entire ceiling collapsed over everything that was left in there which makes things hard to find but if I find something interesting I will make sure to contact you.

[VC54002]

If anyone is interested in high resolution scans of all the diagrams PM me

[Natter]

Based on additional information/fragments of drawings found and provided by VC54002 lately, it's clear that these drawings are of the german pre-WW2 G7v / G7v* torpedo.

Very interesting, as this has unfolded some information regarding spanish involvement in the development of the G7a that has slipped by me before.

The range of german wet-heater torpedodesign leading up to the G7a is well-known - very briefly:
ca 1905: G/7 (the first 50cm torpedo, with later variants/improved versions G/7 AV and G/7**)
ca 1925: G/7s (improved max speed and increased airpressure)
ca 1926: G7v (increased airpressure, new design of the engine - in particular the in-/outlet valves and valvesteering)
ca 1928: G7v* (new airtank to handle increased pressure to 200 ato)
ca 1933: G7a (the first 53,34cm torpedo)

It turns out that the spanish firm Echevarrieta was establishing a torpedofactory in Cadiz in 1929, partly funded by the spanish navy. I haven't got the full story yet, but it seems like they were planning to license-build german torpedoes and requested a "good and well-proven" design for this purpose. Germany offered the G7v, but the spanish navy was demanding a 21" (53,34cm) torpedo - being the new "standard" established internationally at this time.
This initiated the development of a new 21" torpedo, were Echevarrieta wanted to take the lead, planning to make 5 prototypes themselves supported by german torpedoexperts. As it happens, the firm went bankrupt before the project was launched, and germany ended up doing the development themselves, leading up to the final G7a design in 1933 and the fielding (operational status) of the G7a(TI) with Kriegsmarine in 1934.

The new torpedo saw widespread service with Kriegsmarine through WW2 (with some redesigns, especially following the german "torpedokrise" in 1939-41), being their main naval torpedo and the only torpedo used by the surfacevessels, as well as serving along the numerous G7e variants on the U-boote.
It was also used a lot post-WW2, with Norway being the last operator (as far as I know) until 1999, when the coastal artillery phased out the T1 mod 1 (G7a(TI) modified with wireguidance in the mid 1960's).

The G7v also saw some service during WW2: I don't have the complete picture, but it's well documented that it was used in "Torpedobatterie Narvik"; "Lilian" and "Drot" operating as a "schwimmende batterie" in the Ofotfiord until the two shore batteries at Porsöy and Korshavn were established in 1941 with twin 50cm tubes from the vessels. In 1944 the two shore-batteries were equipped with 53,34cm drillingrohrsätze and G7a(TI) torpedoes, upon the before mentioned vessels got their twin tubes back, and continued serving as floating batteries with the G7v torpedo, protecting the major german naval bases up north for the remaining time of the war (like with Tirpitz in Alta/Kåfiord).

Although being different in appearance (for instance, the G7v - virtually identical to all the G/7 variants - had a woolwich tail and the G7a had a whitehead-tail), the G7a incorporated several internal mechanisms/parts from the G7v, including the engine (which explains the similarities in the drawings found: These are among the first technical documents I have seen of the G7v, hence my mistake in the initial ID ).

[Natter]

A bit off-topic, but still...

The G7v also saw some service during WW2: I don't have the complete picture, but it's well documented that it was used in "Torpedobatterie Narvik"

I have scanned this "Torpedobuch" (ie the protocol following each torpedo where all maintenance routines, exersice shots, transfers between units/arsenals etc were documented).
The record shows this particular torpedo - produced in 1927 - was serving with "Torpedobatterie Narvik", on "Drot" (before the torpedo was put into action as a "gefechtstorpedo" in 1939, it had already been used for 179 exersice-shots).

[Roelie]

Dear Natter,
Thank you for all this information!
Do you maybe know whether the G7v or G7v* was used on the earlier Schnellboote (S2 to S-5)? After looking at model drawings of these, it suggests that the tubes on these earlier boats were smaller, so I am curious whether these torpedoes may have been used.
Thank you in advance,
Regards,
Roel

[Natter]

Do you maybe know whether the G7v or G7v* was used on the earlier Schnellboote (S2 to S-5)? After looking at model drawings of these, it suggests that the tubes on these earlier boats were smaller, so I am curious whether these torpedoes may have been used.

I don't know anything certain about that...

However, I have wondered about the Kriegsmarine torpedo inventories, which includes a number of the older G7v torpedoes.
For instance, in december 1940 there were 330 G7v torpedoes in stock. The number being reduced to 321 by march 1941.

Admitable, I haven't used much time to track down all inventories throughout the war (the G7v is not included in lists from at least the summer of 1944, but I'm not sure if that is due to all having been used or the torpedoes having been phased out at that time).

I only know about the before mentioned torpedoträgers "LIllan" and "Drot" specifically using the G7v, as well as the two shore batteries in Norway until the fall of 1944, but the high volume of torpedoes in 1940-41 number suggest there must have been others at that time (the reserve-volume of torpedoes are normally calculated by a factor of "operational tubes" - for instance 4 - so for the two vessels and two shore batteries about 40-50 torpedoes should have been sufficient considering their role as static defences). On the other hand, the stock being reduced by only 9 torpedoes in 15 months also suggest that they are not used by units in regular action, as I suspect would be the case for the S-Boote..?

[Roelie]

Natter,
Thank you for getting back to me! I did a lot of measuring on the older series of Schnellboote and the tubes are indeed smaller. Since the G7v* was as far as I am aware introduced in 1928, the S2 was built in 1931, first trails for the G7a fired from Schnellboote was in 1934. It seems therefore quite possible that these were used on Schnellboote too. The first series of boats where sold to Spain in 1936 already. They seem to have been only temporarily mounted with these torpedo tubes.

[Natter]

Since the G7v* was as far as I am aware introduced in 1928, the S2 was built in 1931, first trails for the G7a fired from Schnellboote was in 1934. It seems therefore quite possible that these were used on Schnellboote too. The first series of boats where sold to Spain in 1936 already. They seem to have been only temporarily mounted with these torpedo tubes.

Makes sense. Before 1934, the 50 cm G7v-torpedoes would probably have been the only available. As mentioned earlier in this topic, Spain wasn't interested in 50 cm torpedoes, so I guess they might have received G7a(TI) and 53,34 cm tubes.