Landships II

spaceman · Corporal

15 cm sFH 13 Hydro-Pneumatic Recoil System

CharlieC · Legend

Ralph Lovett restored an sFH13 some years ago he would probably know how recoil system and variable recoil mechanism worked.

(https://www.lovettartillery.com/).

Have you looked at the patent literature? Both Krupp and Rheinmetall (Ehrhardt) patented many of their mechanisms - Google patent

search works pretty well.

Regards,

Charlie

spaceman · Corporal

I was about to email Ralf Lovett when I came across this forum and thought I would give it a try first! I did quite an extensive patent search without success and assume that it would probably not have been in Germany's interests to have publicly disclosed the details of their weapon technology at a time when they were about to go to war with half of Europe!

Ralph Lovett · General

The 15cm sFH 1913 I have is equipped with a hydro-spring recoils system. It seems that some of this model did have the more basic hydro-spring system and others got the hydro-pneumatic system. It is interesting that the later 15cm lg.sFH 1913/02 in my collection and for that matter all 15cm lg.sFH 13 types have the hydro-spring system. The older 15cm sFH 13 was the only one in the series that I am aware of to try the more advanced hydro-pneumatic recoil.

spaceman · Corporal

My understanding was that the problem was due to the higher recoil forces in the earlier kurz sFH 13 and the extra weight and reduced recoil forces generated in the lange models meant the hydro-pneumatic recoil system was not needed for them. I can imagine what form the hydro-pneumatic recoil system looked like but am struggling to find a cutaway diagram showing the details.

I am assuming the sFH 13 models all had variable recoil but was hoping to find details of how this achieved and how this differed from the typical British cut-off gear or the French approach used, for example, in the Canon de 155 Mle 1917 GFP. Any information on how the German variable recoil was achieved would be very gratefully received.

AN5843 · Sergeant

spaceman wrote:
The sFH 13 was originally designed using a fairly conventional hydro-spring recoil system but, like the British 18-pdr field gun, heavy use at the start of WW1 resulted in the recuperator springs breaking. In both case, a hydro-pneumatic recoil system was introduced to solve the problem which, in the case of the German howitzer, fitted entirely within the original spring case.
I've got drawings of the 18-pdr hydro-pneumatic recoil system and, although I assume the German system must have been similar, I haven't found any drawings or a detailed description of it. If anyone could provide me with this information, I would be very grateful
I also believe, the sFH 13 was fitted with a variable recoil system. In the case of the British variable recoil or cut-off system which I am familiar with, this was achieved via a control rod that is clearly visible on the right of the cradle. In the case of the German variable recoil system, I have not seen a picture of a similar arrangement and assume it was achieved in a different way. Again, I would be grateful if someone could provide me with any information on this topic.

According to Lovett's page on the development of the 15 cm sFH series before 1918, there were 4-5 variants of the sFH 13:

The initial version which used hydro-spring and variable recoil (1520 to 1030 mm)
The modified 1915 version which used hydro-pneumatic and variable recoil (1565 to 1065 mm)
The long-barreled version which had many modifications to reduce wear on the gun when in use
Earlier short-barreled guns which were upgraded to longer barrels, and had some but not all of the modifications of the long-barreled guns (mainly the muzzle band)
A simplified version known as the sFH 13/02 which used hydro-spring and fixed recoil (950 mm)

In addition to this, despite some secrecy about key parts, the design was licensed to Italy before WW1 as the Obice da 149/12. It was used against Germany as Italy's main heavy howitzer in WWI, making it one of the few weapons to be not just used, but widely produced by both sides in WWI.

Other than some changes to things like the sights, the first model Obice da 149/12 was almost identical to the sFH 13, and all 3 versions could be considered variants of the sFH 13. So if you find any documents about how that howitzer's recoil worked, it would likely apply to the sFH 13.

That being said, there is mention in the book "Theory and Design of Recoil Systems and Gun Carriages" that a type of recoil valve was extensively used by Krupp and some other manufacturers, known as the Krupp valve. It functions as a recoil brake. A simpler illustration of the same type of mechanism can be found in the 1969 document "Engineering Design Handbook: Carriages and Mounts Series," on page 8 (with a description on page 6):

In this figure, the Krupp valve is mechanism (c). The description is as follows (note this document never describes this type of brake as a Krupp valve):

33. Another method varies orifices through the piston (Fig. 6c). A rotatable disk with matching holes is assembled to the piston. A projection of the disk is guided by a spiral groove in the cylinder wall. As the disk rotates, the orifices change in size. Again, excellent control is possible.

Going back to the book "Theory and Design of Recoil Systems and Gun Carriages," the book can be found at these 2 sources (the Internet archive generally has higher-quality scans):

https://archive.org/details/theoryanddesigno00unitiala/page/406/mode/2up

https://www.google.com/books/edition/_/dZ1HR34swQcC?hl=en

In it, the Krupp valve is described on pages 386, 399-407, and 432-435, while it is illustrated with better accuracy on page 407:

And the method for making a variable recoil gun using this mechanism is described on page 432:

"MECHANISM FOR REDUCING THE RECOIL ON ELEVATION

Variable recoil is obtained by decreasing on elevation the initial throttling areas by turning, the counter-recoil buffer rod which contains sets of the recoil throttling grooves, as in the Filloux recoil mechanism; or by turning the piston and its rod with respect to the rotating valve, and thus changing the initial openings in the Krupp recoil mechanism; or by rotating a perforated sleeve as in the American sleeve valve.

Two methods for rotating the throttling rod, valve or sleeve are used,

(1) by a sliding bar linkage as in the Pilloux mechanism or

(2) by a four bar linkage as in the Krupp or sleeve valve recoil mechanism"

That's about all I know regarding recoil mechanisms on some Krupp guns, much less the sFH 13 specifically. I know this was used on a lot of Krupp guns, and at least 1 variable-recoil gun, but I don't know if it was specifically used on the sFH 13. I also don't know what sort of recuperator and buffer would be used with this valve, since it was only a brake.

spaceman · Corporal

Many thanks for your input and the very useful reference. This seems to indicate that Krupp used a similar type of rotating or recoil valve to that found on most British howitzers and variable recoil was achieved by rotating the piston rod which governed the point at which the rotating valve closed off the flow of oil through the piston and coaxial rotating valve thus bringing the recoil to an end.

In the British howitzers, the variable recoil control rod linked to the elevation of the gun can normally be seen on the RHS of the cradle which rotated gears at the front of the cradle that, in turn, rotated the piston rod. On the sFH 13, it is difficult to see a control rod mechanism and, if it is internal to the cradle, it is not obvious how this linked to the elevation of the gun especially given that the trunnions where a significant height above the cradle. I will have to look closely at the pictures I have of the gun to see if I can work out what the mechanism was.

However, knowing what form of variable recoil system was used by Krupp is a very useful starting point!

AN5843 · Sergeant

spaceman wrote:
Many thanks for your input and the very useful reference. This seems to indicate that Krupp used a similar type of rotating or recoil valve to that found on most British howitzers and variable recoil was achieved by rotating the piston rod which governed the point at which the rotating valve closed off the flow of oil through the piston and coaxial rotating valve thus bringing the recoil to an end.

In the British howitzers, the variable recoil control rod linked to the elevation of the gun can normally be seen on the RHS of the cradle which rotated gears at the front of the cradle that, in turn, rotated the piston rod. On the sFH 13, it is difficult to see a control rod mechanism and, if it is internal to the cradle, it is not obvious how this linked to the elevation of the gun especially given that the trunnions where a significant height above the cradle. I will have to look closely at the pictures I have of the gun to see if I can work out what the mechanism was.

However, knowing what form of variable recoil system was used by Krupp is a very useful starting point!

I should note that there are at least a few Krupp guns that definitely did not use this recoil mechanism, and there are a few recoil mechanisms that definitely were not used by Krupp in WW1 or earlier. So if Krupp did use this system, the guns it was used on can be narrowed down by eliminating the guns that did not have it, and by eliminating the various mechanisms that they could not have used at the time.

The first bit of information I found was in the US Army 1921 Handbook of Artillery, in which a captured German 10.5 cm leFH 16 is described, including a diagram of the recoil system on Page 174:

(That book is the source of many such images on Wikimedia commons, including this one)

The description of it on Page 175 states that the recoil brake uses 2 throttling grooves in the inner cylinder wall, along the piston's path. Since that carriage was also used by the 10.5 cm leFH 98/09, the 7.7 cm KiH, and the 7.7 cm FK 16, we can also assume that they used a similar or identical recoil mechanism. Only 2 grooves means it is fixed recoil, which makes sense as this carriage predates the sFH 13 which was apparently the first gun where Krupp had to adopt variable recoil.

Looking at some other recoil systems from the Recoil Systems Metric, there are some other systems that can be ruled out. The 4 basic systems described on Pages 3-9 to 3-15 all originated in France: the Puteaux mechanism, the St. Chamond mechanism, the Filloux mechanism, and the Schneider mechanism. Of these:

The Schneider mechanism was patented before the war for Schneider's artillery exported to Russia, and so it could have been used, but it cannot perform variable recoil in its basic form.

The Filloux mechanism is similar to a Schneider mechanism but capable of variable recoil and uses a floating piston (it can almost be seen as an improved Schneider mechanism), and was used in and presumably invented for the 155 GPF- hence the name. But that 155 GPF was only introduced in 1917, far too late for Krupp to adopt it in any WW1 gun afterwards.

The Puteaux mechanism was used in the Canon de 75 (which was designed at the Puteaux arsenal, hence the name) since 1897, and was the first successful hydropneumatic system. But my other thread about manufacturing the Canon de 75's recoil system has pointed out that no one succeeded in manufacturing that recoil system outside of France, until the US did so in late 1918. Germany did not copy this recoil system due to the tolerances involved, as mentioned on pages 49-50 of the Evolution of the American Light Field Gun.

The St. Chamond mechanism, is mentioned on Page 83 of the aforementioned Handbook of Artillery as being invented in 1917 specifically for the 75 mm M1916 gun by Col. Rimailho, one of the designers responsible for the Canon de 75. Further searching yielded Volume 3 of Ordnance journal (1922), which on page 50 also mentioned it as being invented by Rimailho, along with a detailed description/illustration of the mechanism. Further, on Page 161 of that journal is a description of its development, in an article written by Rimailho himself about the St Chamond company's work in the war. It mentions it was developed from the Canon de 75's Puteaux mechanism and used many of the same parts, but was designed to provide variable recoil. Thus it could be considered an improved development of the Puteaux mechanism. Interestingly, Page 44 of the Evolution of the American Light Field Gun mentions that it was Albert Deport who designed it (this may be an error, there are other errors in that document), and also that it was difficult to manufacture much like the Canon de 75. On Page 50 that document states Rock Island Arsenal used the facilities designed for the St. Chamond mechanism to manufacture Canon de 75 recoil mechanism. (Incidentally, I also found a separate handbook for the St. Chamond mechanism's maintenance on the 75mm M1916 gun, and found that the 3-inch AA gun of the interwar era also used the St. Chamond mechanism as shown on Page 55 of Coast Artillery FM 4-125.) Based on this, it can be concluded that the St. Chamond mechanism came too late, and was too difficult to manufacture, for Krupp to have used it in WW1 or earlier.

There are of course other possible recoil mechanisms, especially hydrospring recoil mechanisms. One such mechanism is shown in the illustration I posted in my previous comment, with the illustration of the various types of recoil brakes (this can also be found on Page 3-8 of the Recoil Systems Metric). Mechanism (D), with the perforated sleeve, was used in the 75 mm M1916 gun, before the St. Chamond mechanism was adopted. It can be seen illustrated on Page 78 of the Handbook of Artillery:

This image (and a lot of other information on the gun) is also shown in Page 62 of the Handbook of the 75 mm Model 1916.

This makes it easier to see how the system gets variable recoil by rotating the perforated sleeve, as mentioned on Page 432 of the book "Theory and design of recoil systems and gun carriages." Looking at Section A-A of the above mechanism, it can be seen that if the perforated sleeve is rotated clockwise from its position, some of the holes will start being blocked by the projections in the recoil cylinder, and if that set of holes is longer it will result in variable recoil. It is also mentioned on Page 355 of the Handbook of artillery that the 3-inch M1918 anti-aircraft gun used the same recoil mechanism with a spear buffer. It is described as an American system, though it is not mentioned how old the mechanism is, and it is possible that this could have been used by Krupp.

Based on all this, my best guess is that the Krupp valve (similar to the one used by Vickers on most of its clean-sheet WW1 artillery) is most likely to be the mechanism used on the sFH 13.

spaceman · Corporal

Many thanks for the reply. I agree that, from the limited data available, the 15 cm sFH 13 must have used a Krupp (rotating throttling) valve. In contrast, Rheinmetall, in the 10.5 cm lFH 16 for example, seems to have favoured using throttling grooves.

With the Krupp system, variable length recoil would have involved rotating the piston rod at the front of the cradle as the gun elevated using some sort of mechanical linkage. As said, in British howitzers, the control rod for this mechanism can be clearly seen on the RHS of the gun cradle but, in the case of sFH 13, it is difficult to see any signs of one. The only hint of one I can see of one is an arm that can be seen in some pictures fitted to the LH trunnion which seems to extend down to the cradle. I assume the control rod for the mechanism is actually inside the cradle but what I am struggling to work out is what form the back-end of the mechanism took.

As stated in the well known accounts of the sFH 13, although Krupp developed the gun, Rheinmetall were given some credit for the variable recoil system. While it looks as though it did not use Rheinmetall's throttling groove approach, it is possible that it used their actuating mechanism. What would really help me is if I can find the equivalent of the French 'Instruction Militaire' showing drawings of the sFH 13 - unfortunately, finding documents of this type for old German field guns is a bit of a challenge!

AN5843 · Sergeant

spaceman wrote:
Many thanks for the reply. I agree that, from the limited data available, the 15 cm sFH 13 must have used a Krupp (rotating throttling) valve. In contrast, Rheinmetall, in the 10.5 cm lFH 16 for example, seems to have favoured using throttling grooves.

With the Krupp system, variable length recoil would have involved rotating the piston rod at the front of the cradle as the gun elevated using some sort of mechanical linkage. As said, in British howitzers, the control rod for this mechanism can be clearly seen on the RHS of the gun cradle but, in the case of sFH 13, it is difficult to see any signs of one. The only hint of one I can see of one is an arm that can be seen in some pictures fitted to the LH trunnion which seems to extend down to the cradle. I assume the control rod for the mechanism is actually inside the cradle but what I am struggling to work out is what form the back-end of the mechanism took.

As stated in the well known accounts of the sFH 13, although Krupp developed the gun, Rheinmetall were given some credit for the variable recoil system. While it looks as though it did not use Rheinmetall's throttling groove approach, it is possible that it used their actuating mechanism. What would really help me is if I can find the equivalent of the French 'Instruction Militaire' showing drawings of the sFH 13 - unfortunately, finding documents of this type for old German field guns is a bit of a challenge!
Actually, the leFH 16 was a longer-barreled version of the 10.5 cm FH 98/09, so that recoil system was most likely originally designed by Krupp.
The credit Rheinmetall were given could mean a lot of things, since they invented the world's first artillery of any kind with a variable recoil system. This was the 1904 mountain gun, as mentioned on the below link:
http://www.germancolonialuniforms.co.uk/militaria/mountaingun.htm
(in the early 1900s Rheinmetall guns were usually known as Ehrhardt guns after Rheinmetall's founder, Heinrich Ehrhardt)
This also led me to check back on another book about artillery from 1910, Modern Guns and Gunnery: A Practical Manual for Officers of the Horse, Field, and Mountain Artillery by H.A. Bethell:
https://books.google.com/books?id=S7ZBAAAAIAAJ&dq=variable+recoil+ehrhardt+1908&source=gbs_navlinks_s
It describes Ehrhardt and other variable-recoil guns as using the Ehrhardt-Vavasseur system on multiple pages. On Page 129, this system is described, and turns out to be mostly identical to the Krupp valve. It is also mentioned that the original system is a Vavasseur gear, and Ehrhardt (Rheinmetall) designed the modified versions. As such it is mentioned on Page 328 that "Messrs. Ehrhardt are the original inventors of the Ehrhardt-Vavasseur controlled recoil system."
It was easy to back this up by searching for "vavasseur recoil valve" in Google, which quickly pointed to Patent US283688A:
https://patents.google.com/patent/US283688
This patent from 1883 describes the basic functioning of the valve, in a fixed recoil form. (Josiah Vavasseur is best known as the inventor of the Vavasseur mounting for naval and fortress guns.)
The Ehrhardt contribution is harder to find, but I remembered that the original Ehrhardt gun was designed with the help of Konrad Haussner (whose long-recoil patent caused the French to start developing the Canon de 75). He has a lot of patents related to artillery in Google Patents, but none relating to variable recoil. But it is mentioned on Rheinmetall's corporate history page that Haussner had a falling-out with Ehrhardt, and Carl Völler replaced him in 1903. Völler became general manager in 1912 and remained in this role until his death in 1916:
https://www.rheinmetall.com/en/rheinmetall_ag/group/corporate_history/125_jahre_rheinmetall_1/jahre_1889_bis_1/index.php
Upon searching "Carl Völler artillery patent" on Google, Patent US1073061A pops up on Google Patents. From there it is possible to check other patents by Völler by clicking the name (his name is spelled Karl Voeller in the patents, so that has to be the term entered for inventor), and a lot of results come up. Of special importance is Patent US755418A from 1904- which describes the concept of using the Krupp valve for variable recoil. It describes the exact system Vickers and likely Krupp used in their WW1 artillery with variable recoil. This is almost certainly the modification that Ehrhardt made to the Vavasseur valve. The other patent of note is Patent US818801A, also from 1904 and probably related, which describes how the variable recoil is controlled by a cam attached to a rod running inside the recoil housing to the front (it looks similar to the Vickers guns of WW1). There are plenty of other artillery recoil patents from Völler, but those are the most notable.
Since both Haussner and Völler have many patents, I thought that people with one artillery patent assigned to Krupp might have many more. So if I could find one patent assigned to Krupp about recoil, then I could search the inventor's names to find more. In the main 1904 Völler patent for variable recoil, one of the patents under "Similar documents" is Patent US927862A, assigned to Krupp from Otto Lauber and Franz Boeminghaus. When clicking on both of those inventors, a large number of other artillery patents popped up- 32 patents for Lauber and 15 patents for Boeminghaus. Going down those patents further, Boeminghaus has no collaborators other than Lauber on his recoil patents, but Lauber's Patent US724398A is shared with Adolf Resow, who has another 4 patents. Resow's Patent US633366A for a recoil brake is in turn shared with Otto Behnke, who has 17 patents. Behnke's Patent US1227134A is shared with Walter Heilemann, who has 14 patents, and Norbert Koch, who has about 27 patents assigned to Krupp. Many of his recoil patents are shared with Otto Lauber, but some patents like Patent US913403A are shared with Georg Hayn, who has 19 patents (but unfortunately none are about recoil). Going back to Lauber's patents, Patent US707432A is shared with Friedrich Stock, who has about 13 patents assigned to Krupp. Lauber's Patent US864175A is shared with Heinrich Kanonenberg, who has 10 patents. Lauber's Patent US809819A is shared with Karl Thiele, who has 2 patents assigned to Krupp.
That's about all the patentees I could find who assigned their artillery inventions to Krupp during this time. So putting all that together, Krupp's artillery patents from the late 1890's to 1918 sort into:
Adolf Resow (4 patents)
Otto Behnke (17 patents)
Otto Lauber (32 patents)
Friedrich Stock (13 patents)
Norbert Koch (27 patents)
Karl Thiele (2 patents)
Franz Boeminghaus (15 patents)
Heinrich Kanonenberg (10 patents)
Walter Heilemann (14 patents)
Georg Hayn (19 patents)
These are in order of when their first patent assigned to Krupp was filed.
If you need to know how the recoil system was connected to the elevation, Otto Behnke and Otto Lauber seem to have the most recoil-related patents. More specifically, Lauber and Boeminghaus' Patent US923051A describes a possible method of connecting the recoil with the gun elevation (the controlling rod runs inside the recoil housing, in the bottom-right corner if you look from the muzzle end of the gun). Heilemann's Patent US1028939A describes another method, which is different than the usual gear connected to a rod. It's also dated from 1910 when the sFH 13 was being developed, so it is definitely interesting as a possible linkage method. But it should be noted, that many patents are impractical and do not get used in final products.
Those sources may help you with your search.

-- Edited by AN5843 on Tuesday 19th of July 2022 12:20:19 AM