Spandau Rate of Fire in WWI

[Chill31]

It seems like this topic deserves its own thread at this point...

 

I am going to condense the previous information from another thread here along with everything I have found so far.  Open for discussion in case I am missing something.

 

To start, I tested the Fokker Dr.I rate of fire after seeing how my 120 Rhone was setup to fire once per engine revolution.  In this configuration, the rate of fire should be dependent up on the engine rpm.  I found that the FC Dr.I has a 650 rds/m rate and it does not change with rpm (I'm not necessarily of the opinion that it needs to either).  Based on what I've heard from guys who have shot Spandau MGs, heard them fired aboard replica airaft, and watched on youtube (that makes me an expert right?), 650 seemed to fast.  Hence the following research.

 

Here is Jason's post about the rate of fire change in ROF: ROF MG Rate of Fire Explaination

 

First, start with the gentleman's description of the Spandau LMG08/15:

 

Now you know as much as I know about the Spandau...so what was the rate of fire as the guns were mounted on aircraft?  The only way I know how to tell is based upon what he said about the spring tension on the left side of the receiver.  When doubled, it roughly equates to the rds/m firing.  With that in mind, I began looking for pictures of the guns mounted to WWI German fighters.  I found some of the Fokker Dr.I, Fokker D7, Albatross D5, and Roland D6.  It appears that, across the board and throughout the war, the Germans were setting the Spandau to something around 35-40 kg of spring tension.  If we believe the guy in the youtube video and take his adjustment and subsequent firing of the gun as correct information and authentic presentation of the gun firing, then our Spandau MGs in FC should be firing at no more than 450 rds/m.

 

If you see something I missed or have something to add, please do!

 

Following are all of the pictures I collected that show the setting of the spring tension on the side of the reciever:

 

This is an image of a TVAL reproduction Spandau (it is rubber, BUT it appears to be made from the mold created from a real gun)

 

Here are is an image of the Albatross

 

Here is an image of the Roland D6

 

Here is the Fokker Dr.I

 

 

Here is the Fokker D7

 

Edited August 14, 2018 by Chill31

[Garven]

Somewhere a flight simmer is relieved that they aren't the only one who flies with their teddy bear. 

 

BTW the replica doesn't look like it was cast from a mold.  Could it be a de-milled gun welded back together in a non-firing condition?

Edited August 14, 2018 by US103GarvenDreis

[Trooper117]

Interesting stuff, thanks!

[HiIIBiIIy]

The fourth picture down seems to have a rate of fire about 300 RPM if not slightly less.

[HagarTheHorrible]

Some research done and I think posted on "The Aerodrome" website suggested that the usual rate was about 420, sometimes a little more sometimes a little less. Several factors were involved in the setting of the rate.  Reliability of the interrupter mechanism itself, consisting of a series of metal rods that were affected by wear, setting and temperature differential from altitude variation.  Secondly, the cloth belts used limited reliability.  Steel disintegrating belts were tried but problems with obtaining quality steel was an issue cloth belts were retained.  I don't know exactly why cloth belts were an issue, over and above their typical drawbacks, whether it was speed or just expected jam rate for every "X" number of bullets fired.  Thirdly, there was the relationship between typical engine speed and machine gun cyclical rate, a higher rate didn't necessarily compliment the engine speed and would actually result in fewer rounds down range.  The figure of 420, average, comes from observation of photo's of German aircraft where the gun can be seen.

 

A good reference, and well worth picking up is "Flying Guns of WW1" by Antony "Tony" Williams and Dr. Emmanual Gustin. Tony is, or was a regular contributor to "The Aerodrome" website, from what I can gather.

 

It appears that the British were able to set consistently higher rates due to the effectiveness and reliability of their "CC" interrupter gear, metal disintegrating belts and "Hazelton" muzzle booster.  Theoretically, this allowed for a rate of 800rpm, but again this was probably lowered to sync with the best expected rate when combined with engine speed.  It's possible that the higher rate just allowed for a greater range of possibilities.  I don't know if it's possible to observe the rate of fire of the Vickers from photo's or how it was set in combination with the booster.

Edited August 14, 2018 by HagarTheHorrible

[Chill31]

On the topic of muzzle boosters...I lifted this from the aerodrome forum: 

 

A bit from one of Lt. Boelcke's letters, dated November 1st, 1915, which seems relevant here:
"What helped me greatly was a visit from one of Fokker's mechanics a few days ago; he fixed my machine-gun up with a patent novelty which enables me to fire from four hundred and fifty to six hundred shots a minute instead of the former four hundred."

[SeaW0lf]

12 minutes ago, Chill31 said:

On the topic of muzzle boosters...I lifted this from the aerodrome forum: 

 

A bit from one of Lt. Boelcke's letters, dated November 1st, 1915, which seems relevant here:
"What helped me greatly was a visit from one of Fokker's mechanics a few days ago; he fixed my machine-gun up with a patent novelty which enables me to fire from four hundred and fifty to six hundred shots a minute instead of the former four hundred."

 

You can find the quote in the book "Knight of Germany: Oswald Boelcke German Ace". Interesting, because they were doing it in 1915... It might end up being a preference or circumstantial, like pilots reducing the rate of fire later on in the war because of manufacturing problems, etc., not really the design or the mechanism per se.

 

Whenever I have some time I'll try to do some research on this piece of information.

[HagarTheHorrible]

4 hours ago, SeaW0lf said:

 

You can find the quote in the book "Knight of Germany: Oswald Boelcke German Ace". Interesting, because they were doing it in 1915... It might end up being a preference or circumstantial, like pilots reducing the rate of fire later on in the war because of manufacturing problems, etc., not really the design or the mechanism per se.

 

Whenever I have some time I'll try to do some research on this piece of information.

 

I think we have to assume it remained a patent novelty.  We've probably all been there, at sometime or another.  Shown the latest and greatest only to find that it isn't all it's quite cracked up to be and quietly forget about the whole unfortunate affair.  Reliability, particularly with a single gun, was probably an issue, muzzle boosters exacerbate any weaknesses. With the imperfections of early interrupter gear the chances of a malfunction or bullets hitting the propeller blade was possibly greater than the nerves could withstand. 

[SeaW0lf]

2 hours ago, HagarTheHorrible said:

I think we have to assume it remained a patent novelty. 

 

In 1915? In this case your argument is just plain elucubration and you are going against a clear quote from Oswald Boelcke, not just a John Doe.

 

Perhaps he mentions something further in the book, but otherwise I consider it a strong statement from him. He did not say it had drawbacks.  It was when things have just started, the Fokker E.III had just been released in the same year and the improvements in design and manufacture were just exponential in the next couple years.

[Cybermat47]

If Immelmann was using one of these muzzle boosters when he shot his own propellor off, that would probably be a convincing argument against using it.

 

I’d also be interested to know if the gun Boelcke had the muzzle booster fitted to was an lMG-08 or an LMG-08/15. I’m not sure if there was any difference in the rate of fire between the two versions, though.

 

I think that someone here with a great knowledge of aviation history, like @LukeFF, should be able to shed some light on this.

[HagarTheHorrible]

1 hour ago, SeaW0lf said:

 

In 1915? In this case your argument is just plain elucubration and you are going against a clear quote from Oswald Boelcke, not just a John Doe.

 

Perhaps he mentions something further in the book, but otherwise I consider it a strong statement from him. He did not say it had drawbacks.  It was when things have just started, the Fokker E.III had just been released in the same year and the improvements in design and manufacture were just exponential in the next couple years.

 

Nothing of the sort.  The RFC used the Hazelton muzzle booster to increase the cyclical rate of their guns, the Germans did not.  If the "patent novelty", which I think we can probably agree was a muzzle booster, had been a success then it's reasonable to assume it would have become a standard feature of German, synchronized, aircraft weapons, it didn't.  Just because Boelcke said something on one day didn't necessarily mean the next day, with more experience, he changed his mind.  He, and we, are more likely to record positives rather than negatives. Opinions aren't always correct or set in stone.  For all of Boelcke's greatness he was still a young man learning his craft, a craft that had no precedents and was changing on an almost daily basis in a particularly harsh and unforgiving environment.

 

It seems that the early German aircraft guns were overly endowed with cooling perforations that didn't provide enough support for the barrel with booster attached.  Later guns didn't have as many perforations and thus could have supported the booster, in theory, but given that several other things were needed to work efficiently it was maybe surmised that the risk of stoppages outweighed the advantages.  A gun that fires, all be it slowly is better than a gun that fires not at all.

 

What part Cc gear, metal disintegrating belts and maybe even better quality ammunition played in these decisions is open for debate.

Edited August 15, 2018 by HagarTheHorrible

[SeaW0lf]

1 hour ago, HagarTheHorrible said:

which I think we can probably agree was a muzzle booster, had been a success then it's reasonable to assume

 

We can't skip Boelcke's account just on supposition. I'm not saying it happened that way, but I think the correct route, even because Chill did not rebuke it promptly, he just posted it as a new evidence, would be to cross the information with knowledgeable people in the field, not just historians, but builders. I don't even know the context of his account, but he's not saying about range of fire (we all know how deceptive it was), but a simple function and setting.

[BMA_Hellbender]

18 hours ago, HagarTheHorrible said:

Some research done and I think posted on "The Aerodrome" website suggested that the usual rate was about 420

 

 

   BLAZE IT!  

 

 

 

EDIT: Joking aside, the high rate of fire is part of the problem why the damage model sometimes feels arcady.

That, along with g forced on gunners, are fixes I am hoping will pull through by release.

Edited August 15, 2018 by Hellbender
(actually had something meaningful to say for once)

[HagarTheHorrible]

As posted by Tony Williams on the Aerodrome forum in " The myth of German fire superiority", post number 4 " Mr Williams seems to be about as knowledgeable as you're likely to find.   Dave Watts knows all about the Spandaus, and he may drop in sometime. From what he's told me, around 450 rpm was standard. What is very difficult to discover is the actual effect of particular synchronisation systems on the rates of fire of particular guns. I have put the following information in 'Flying Guns World War 1: Development of Aircraft Guns, Ammunition and Installations 1914-1932' by Emmanuel Gustin and myself (due to be published today by the Crowood Press): "Synchronisation systems reduced the gun's natural rate of fire; by how much depending on a variety of factors. The first factor was a gun whose trigger mechanism could be controlled separately from the action of the bolt. As we have seen, the Lewis gun did not have this feature and the initial efforts at synchronisation resulted in a RoF of only 100-150 rpm, less than a quarter of the normal rate. The later Alkan gear managed to increase this to 160-200 rpm, and a more thorough redesign of the firing mechanism by Hazleton did see some limited use, but by then the Vickers had been accepted as standard. The second factor was a precise and reliable synchronising gear. The more accurate it was, the lower were the safety margins required and the greater the number of degrees of the propeller disk available for firing. The third factor was the gun's normal rate of fire; the higher this was, the greater the percentage loss through synchronisation (other things being equal). The final factor was the number of propeller blades; the more there were, the more critical accurate timing became. The rate of fire of a synchronised gun tended to be rather erratic because it varied with propeller speed. Theoretically, it was possible to achieve an ideal match between the propeller rpm and gun's natural rate of fire, so that the gun was not slowed down at all. However, such harmony would obviously disappear as soon as the engine slowed down or speeded up. This particular problem was not solved until the adoption of the constant-speed propeller, which was uncommon until the late 1930s. The effect of synchronisation on the rate of fire can best be explained by describing a simple system like that introduced by Fokker, in which one firing signal was sent to the gun for each rotation of the propeller. If the gun was capable of firing at 500 rounds per minute, then for propeller speeds of up to 500 revolutions per minute the RoF would be the same as the propeller rpm. However, as soon as the propeller exceeded 500 rpm, the gun mechanism could no longer keep up and could then only fire on every other rotation, so the RoF would drop to 250 rpm. It would then accelerate again with increasing propeller speed but at half the rate, so when the propeller was spinning at 1,000 rpm, the gun would be back to firing at 500 rpm again. Once more, propeller revs faster than this would cause the RoF to drop, but this time only to two-thirds of the full RoF, as it would fire on every third rotation, so it would be achieving 330 rpm. As the propeller continued to accelerate to 1,500 rpm, the gun would be back up to 500 rpm again, and so on. Any quoted figure for synchronised rates of fire could therefore only be an average. It is also worth repeating that quoted RoFs for unsynchronised guns were only averages also, with the actual RoF for different examples of the same type of gun varying quite significantly depending on age and maintenance. Any one gun might also vary in its rate of fire depending on the ammunition used, on the effect of the low temperatures experienced at high-altitude in congealing the gun lubricants and of course on the variable G-forces consequent on manoeuvring. More advanced systems like the CC and the later German types sent two firing signals per propeller revolution (logical with a two-bladed propeller, in which there would be two firing opportunities per revolution), although possibly at the expense of some reliability in these primitive early systems, as they would have to work twice as fast. In this case, the maximum RoF for our 500 rpm gun would be reached twice as often, at 250, 500, 750, 1,000, 1,250 and 1,500 rpm. A still more sophisticated variation was to use a “critical sector cam”, which instead of just sending a single firing impulse sent a continuous one during the “safe” period when the propeller blades were out of the way. The effect of this was much less regular, with the gun firing in erratic bursts, but the average RoF was the highest of all. In the vast majority of cases at this time, the engine directly drove the propeller so the propeller revs were the same as the engine revs. Rotary engines ran at around 1,200-1,300 rpm, the six-cylinder in-lines favoured by the Germans at 1,200 rpm at the start of the war and 1,400-1,500 rpm by the end, the Hispano-Suiza used in the SPAD at 1,600 rpm, and the Rolls-Royce Falcon V-12 used in the Bristol Fighter at 1,800-2,250 rpm, depending on the version. In the case of geared engines (which saw relatively little use in the First World War, the main fighter example being in some installations of the Hispano-Suiza V-8) then it was clearly the propeller rather than engine speed which determined the synchronisation conditions. Taking all of this information together it becomes possible to understand the different national choices in regulating the gun RoF. With their in-line six-cylinder engines running at 1,400-1,500 rpm, the Germans' Maxim would have had to have been capable of about 800 rpm to take full advantage of a firing impulse every other rotation. It could not do this, so it made sense to adjust it to fire approximately every third rotation and thereby enjoy the benefits of greater reliability of both gun and synchroniser gear and reduced gun heating problems; the Maxim was in fact normally set at around 450 rpm. The introduction in 1917 of the Hazleton gear to the British Vickers enhanced the RoF to 850-900 rpm, which in combination with the fast-acting and more reliable CC gear would fire twice for every three rotations of a rotary engine, or every other rotation with the faster-running V-8 and V-12 engines. " Tony Williams: Military gun and ammunition website and Discussion forum __________________ Tony Williams: Military gun and ammunition website

[SeaW0lf]

20 minutes ago, HagarTheHorrible said:

As posted by Tony Williams on the Aerodrome forum in " The myth of German fire superiority", post number 4 " Mr Williams seems to be about as knowledgeable as you're likely to find.

 

You are missing the point here... Boelcke's account diverges from it, so I think it is relevant (by its simplicity) and ideally should be explained instead of just to skip it. That's what I'm saying, to cross information with knowledgeable people to explain it. That's how research is usually done, at least from my point of view.

[HagarTheHorrible]

Nothing is ever certain, even when we are certain about what we know.

 

Tony Williams, who has written a book about and called "Flying Guns of WW1" is probably as informed as anyone.  Tony recommends and defers to Dave Watts as the foremost expert on the Spandau. Dave Watts conclusion from the evidence he has seen was that the German guns were typically set to approx 450 rpm, slightly less than the typical rpm of a standard maxim gun.  If Boelcke's letter held water then it would be reasonable to assume that a rate in excess of 500 would have been more typical from 1915 on.  What, if anything, I'm unsure about is, is the relationship between the muzzle booster and the ROF spring setting

[Chill31]

14 hours ago, Chill31 said:

On the topic of muzzle boosters...I lifted this from the aerodrome forum: 

 

A bit from one of Lt. Boelcke's letters, dated November 1st, 1915, which seems relevant here:
"What helped me greatly was a visit from one of Fokker's mechanics a few days ago; he fixed my machine-gun up with a patent novelty which enables me to fire from four hundred and fifty to six hundred shots a minute instead of the former four hundred."

The Spandau as you see it normally with the flash hider and muzzle booster was not always so!  It seems that what you would normally think of as a Spandau MG began without those features.  So Boelcke did use the piece that Fokker brought him, and in fact, the German air service used it throughout the rest of the war!  See the attached pictures of Fokker EIIIs, including Max Immelmann during the period when it was not used.

 

[HagarTheHorrible]

Just for info: The Vickers-Maxim machinegun by Martin Pegler

 

In German service

 

"The pre-1914 years were to prove to be turbulent ones for the development of the new Vickers Company, for the seven-year manufacturing agreement with Ludwig Loewe in Germany expired and there was a scramble for licensing of the commercial manufacturing rights relating to the guns. In 1896 Loewe had formed a new company, Deutsche Waffen- und Munitionsfabriken (DWM). He had been making a copy of the Model 1894 Maxim, which was adopted by the German Navy, and he copied the Model 1901, which was purchased by the German Army, who equipped 16 machine-gun detachments, so that every army corps incorporated a Maxim detachment. German observers of the Russo-Japanese War (1904–05) saw at first hand the devastating effects of the fire from these guns on attacking infantry, but also began to appreciate the shortcomings of the existing designs. Some of the German modifications were, to say the least, a curious mix of the practical and puzzling. The Germans immediately set about improving the design of the Model 1901 by reducing its overall weight, eliminating the awkward and heavy tripod in favour of an equally clumsy and heavy Schlitten 08 mount (sledge mount). Inexplicably, they ignored the improved 1901 lock, opting to retain the old non-adjustable 1889 design, which meant that only trained armourers could headspace the locks and resulted in all World War I-production sledge mounts being manufactured with stowage boxes to accommodate two spare locks. Cold-weather performance was sometimes poor, due to internal resistance from parts stiff with frozen oil, so a muzzle booster was added; this increased the recoil force on the barrel, improving the performance and marginally raising the rate of fire from a relatively slow 350rpm to a more respectable 450rpm. Unlike the British, the Germans also added a side mount on to which a telescopic sight, the Zielfernrohr 1912 (Zf 12), was fitted; oddly, no optics were ever provided for the Vickers guns. The mechanical function of the new guns was unaltered from the early model and it was adopted as the Maschinengewehr 1908 (MG 08). The total weight of the water-filled gun and mount was a hefty 137lb and this was to place some tactical limitations on its use during the forthcoming war. "

 

 

In case you have lots of time on your hands and want to inform yourselves about the Vickers and Vickers type weapon.;

 

https://www.tommy1418.com/uploads/1/2/7/3/12733599/36291497-handbook-of-the-vickers-machine-gun-model-1915-with.pdf

 

 

 

© Osprey Publishing • www.ospreypublishing.com

 

The need for reliable feeding of the guns was heightened once it was realized that the normal rate of fire of a Vickers gun (500rpm) was simply too slow for fast-moving air combat – a rate of around 800–900rpm was required. The Hazleton Device, a simple muzzle restrictor and buffer system, was tested; this could provide a dizzying 1,000rpm, which was actually faster than the internal parts of the Vickers could reliably cope with, so it was modified to lower the rate and then widely adopted. As a result the additional wear on the working parts meant that side-plates, fusee springs and springs had to be strengthened and a larger cocking handle fitted. The guns had no water cooling, so the front of the jacket was machined with large vent-holes in it, and rear ‘gills’ to allow the passing air to exit. On fighters such as the Sopwith Camel that mounted two guns, a new left-handed feed block was produced, permitting ammunition feed from either side. These modifications were to provide British pilots with a considerable advantage over their German counterparts, whose guns generally remained unmodified with a ground-use rate of fire.

 

"the first round fires. Initially the gun jerks sharply, then settles down with a steady rocking motion and a distinctive ‘rat-tat, rat-tat tat tat’. A Maxim, with its slower rate of fire, made a more measured ‘tac-tac-tac’ sound, and World War I infantrymen could tell instantly whether the gun firing was British or German."

 

 

 

 

 

 

Edited August 16, 2018 by HagarTheHorrible