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Schurzen Effects on German Tanks


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#1 Peter M. Skaar

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Posted 06 March 2017 - 01:44 PM

In 1943 many German tanks were provided with "Schurzen" to better resist Soviet AT rifles fired from the flank.  The additional side benefit of the Schurzen was a stand-off for heat rounds as well which made those much less effective.

 

Since the Schurzen were fairly thin, what benefit would be gained against larger AP rounds of 45mm and up?

 

In the game there is no differentiation for different ammo types fired at the flanks of German tanks fitted with Schurzen.

 

Here is a possible home rule to better differentiate the effects of different ammo on these.

 

1. ATR and Heat rounds would be the standard effect.

 

2. AP rounds in the 45 to 57mm caliber or less would add +2 to the normal side armor.

3. AP rounds of larger than 57mm and up would only add +1 to the normal side armor instead of the full Shurzen effects.

 

Anyone have any thoughts on this? 

 

Since this extra armor is fairly thin, I really don't see it having a full effect against standard AP rounds than the other two types I listed.

 

Thanks,

Pete



#2 Kenny Noe

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Posted 20 March 2017 - 10:45 AM

Pete,

 

I've asked out MP manager to chime in.  he should post something soon.

 

Thanks



#3 Peter M. Skaar

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Posted 24 March 2017 - 12:18 PM

Hi Kenny

 

Thanks for the heads up.  I am really interested to see what you guys think plus anyone else on this forum that has played and enjoyed Mein Panzer.

 

Pete



#4 Bob Benge

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Posted 25 March 2017 - 07:16 PM

Hi Peter,

 

There is a Schurzen rule though it is not defined as such. The rule is in Mein Panzer Core Rules, Chapter 9, page 9.4, DV (Defensive Value) section and it states:

 

"In some cases, there will be two values listed, where the first value is used against AP attacks, and the second value is used against any type of HEAT attack."

 

Now when we reviewed this I had done some research into Schurzen and found that it was predominately used to prevent ATR rounds from destroying tank road wheels and causing a track to be thrown, thus immobilizing the vehicle. The Schurzen was typically thin sheet metal and, in some cases, even bed springs wielded to a frame mounted on the side of the tank. I remember a good discussion on the subject with the group and found that Schurzen would have relatively no impact to a high velocity round. So we kept it simple and said if the vehicle had a double number for side armor then HEAT rounds would use the second value. I looked at your suggestion and would be inclined not to use it. The reasoning is, is that a +1 armor rating would equate to 10mm of armor and +2 , 20mm of armor and since we are dealing with sheet metal and bed springs I don't think this would be an accurate representation of the effects of a high velocity round.

 

Hope this helps, :)


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#5 Peter M. Skaar

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Posted 27 March 2017 - 04:37 PM

Overall, I don't have any major issue with this interpretation.  Since these schurzen were originally designed to reduce, if not stop the effects of ATR rounds, they should be given full effect against both ATR and HEAT.  ATR rounds are essentially small AP rounds and the Germans tried to cover both the sides of the vehicle as well as the turret so there was concern that these rounds would be degraded if not stopped by the addition of this extra armor.  The effects against HEAT rounds were a nice bonus.

I'm still not sure that there was absolutely no effect on AP rounds but for game purposes I am okay with no effect for "true" AP rounds.

 

 

Thanks for chiming in Bob.



#6 Mark 1

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Posted 31 March 2017 - 03:51 PM

"Schurzen ... was predominately used to prevent ATR rounds from destroying tank road wheels and causing a track to be thrown, thus immobilizing the vehicle."

 

The primary purpose for Schurzen was to prevent penetration of armor by ATR projectiles.  Any protection it offered to running gear was a secondary benefit.

 

As Pete points out, this is one reason that Pz III and IV turrets were provided with Schurzen.  No running gear there.

 

It is also the reason that the Panther A was provided with Schurzen.  Combat during the second half of 1943 demonstrated that there was a small area of the original Panther D armored hull side, below the sloped upper hull and above the return run of the track, that was vulnerable to penetration from Soviet 14.5mm fire. It seems that results were clear ... any vertical plate of less than 40mm WOULD be hit and penetrated by ATRs in action against the Red Army.  In the Panther A this was covered by small Shurzen.  In the Panther G the vulnerability was removed by the redesign of the hull.  All it took was 45mm of plate, or some level of sloping, to complete the protection from ATR fire.

 

The mechanism by which Schurzen worked was to incite wobble in the projectile.  When striking a plate for which there is marginal penetrative reserve, if the projectile is in an off-axis attitude it greatly reduces the likelyhood of successful penetration. Some portion of the kinetic energy of the round diverts into rotational force, both reducing the round's ability to dig into the armor and increasing the surface area of the penetration from the point to the sides. Enough wobble and you get a visible mark of a side-on slap and riccochet, rather than crater of an unsuccessful penetration.  These slap-marks are visible on the armor of tanks with Schurzen.

 

It did not take armor-grade plate to induce this wobble. So the mild-steel used in Schurzen (and even mesh screen in late war Pz IVJ's) offered little protection against rounds of substantial mass.  A 45mm or larger projectile had sufficient total kinetic energy and mass to resist significant loss of penetration through any minimal wobble, in part due to the excess of penetrative potential vs. the levels of plate protected by Schurzen, in part due to the different length-to-width ratios of the larger caliber rounds in those days.  Soviet ATR rounds were rather longer, relative to their diameters, than cannon projectiles. High L2W ratios reduce stability over time of flight in rifled (spun) projectiles, but the ATRs were not firing out to 1,000+ meters, so the superior penetration of a high L2W profile was more important than the stability in flight.

 

"The Schurzen was typically thin sheet metal and, in some cases, even bed springs wielded to a frame mounted on the side of the tank."

 

The Soviets developed the spring-steel add-on plates in the late war period. Whether they were actually bed springs is a somewhat contentious question, as it is pretty clear that they manufactured spring steel screens to be added to tanks for urban combat, but that does not mean that crews in combat zones didn't find their own improvisations as well ... some of the photographic evidence looks pretty clearly like improvisation using bed-springs.  These defenses were very specifically for protection from HEAT rounds .. most notably from Panzerfaust HEAT rounds.  The common practice of placing them on the front-half of the turret roof indicates the expectation that it was to defend from hand-held weapons (fired from upper floors in urban areas).  These defenses were effective not so much becase they increased the effectiveness of the armor through stand-off, but rather by defeating the fuzing mechanism.  The rounds simply didn't detonate when caught up in the springs.

 

Or so I've read.

 

-Mark

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#7 Peter M. Skaar

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Posted 31 March 2017 - 05:28 PM

Hi Mark

 

Great to have you weigh in on this.  I always appreciate your insights and consider you to have great knowledge of these kinds of things.

 

I suspected, but did not know, that the gap between the skirt and the actual armor did something to the ATR round and your explanation covers it perfectly.  The same for HEAT.

I gather then, from your response, that there would be almost no benefit of schurzen (I'm talking solid plate, not bedsprings or mesh) on any round over 14.5 mm?  Would there be any effect against a 20mm or 37mm round fired from a T-60 tank or 37mm AA gun? 

 

The bottom line for me would be - Do sideskirts have any effect, in game terms, on standard AP rounds, not those fired from an ATR? 

Thanks again Mark and Bob for your input on this.  I am okay to be wrong as I am learning things.

Pete



#8 Bob Benge

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Posted 31 March 2017 - 07:53 PM

Great info Mark! Thank you for the clarification. :)

 

I would say that, in game terms, you could say that trying to put any benefit to this would be a guess and out of my wheelhouse. There is no numerical evidence to work with to make any changes at this point. This doesn't preclude you Pete from using a house rule if you can put some numerical value to it.  From Mark's info maybe <45mm would gain a +1???


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#9 Peter M. Skaar

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Posted 01 April 2017 - 04:49 PM

Hi Bob

 

Thanks very much for your help.  I hope to hear from Mark about this again concerning smaller caliber AP rounds such as 20, 37, 45, up to 57.  Based on what he said, it would seem that 45mm and up would have no problems with the schurzen.  I do wonder what the "cut-off" point would be when deciding to whether the schurzen add any protection at all.

Pete



#10 Bob Benge

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Posted 01 April 2017 - 06:28 PM

Hi Pete,

 

My Pleasure! I would also. I would also like to see the documentation that supports his position. If that exists I can make a change to the rules. ;)


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#11 Peter M. Skaar

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Posted 03 April 2017 - 12:39 PM

Hi Bob

 

Thanks again for your responses. 

Pete



#12 Mark 1

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Posted 06 April 2017 - 03:24 PM

Most secondary sources on the effects of Schurzen on ATR projectiles point back to the original testing reports from Kummelsdorf in February of 1943. It was based on this test reporting that the orders for Shurzen production and fitting to Pz III and IV were given.

 

I have never been able to find an original of the Kummelsdorf reports online. Doesn't mean it's not there somewhere, but if it is I haven't found it.

 

Perhaps the most widely accredited secondary sources are the various books by Jentz. His books on Pz III, Pz IV, Panther A, and StuG III all provide information from the Kummelsdorf 2/43 testing.  I do not know if the larger, more expansive "Panzer Truppen" volumes also contain details of these tests.

 

From reading secondary (and tertiary) sources I understand that the 2/43 tests assessed the impact of both 5mm non armor-grade plates, and wire mesh screens, on Russian 14.5mm ATRs at a range of 100m, and on 75 / 76.2mm HE rounds.  It is my understanding that no other types of weapons were included in these tests.

 

These tests were conducted due to the fighting conditions on the Eastern Front in 1942.  ATRs (both PTRS-41 and PTRD-41) had become common over the course of 1942.  For larger guns there were shortages of AP production in 1942, so it was relatively common for Soviet gunners to fire HE at German tanks.  The 30mm armor on the sides of Pz III and Pz IV was shown in combat to be vulnerable to both. As both models were up-armored on the front, the chassis were becoming overloaded, and up-armoring the sides to provide effective protection levels was simply not in the cards for these vehicles.

 

The findings were that both 5mm steel and wire mesh were effective.  The effects on 14.5mm ATR projectiles was to induce wobble so that the rounds side-struck the armor behind, and failed to penetrate.  The HE rounds detonated at a distance from the armor, preventing damage to both the interior of the tanks (preventing penetration or significant spalling from non-penetrating HE hits) and also reducing damage to the running gear.

 

As both plate steel and wire mesh were found effective, it was thought that the lower weight of the wire mesh would be a superior solution. However the lack of rigidity in the wire mesh meant that more complicated mounting mechanisms were needed. So the plate went into production immediately, and the wire mesh skirting did not go into production until more than a year later.

 

I have never seen a reference to primary source materials of German testing of Schurzen against hollow-charge projectiles, nor against larger AT projectiles.

 

However the US Army did conduct test-firings against add-on spaced armor plating as part of the Shoeburyness tests in May of 1944.  These tests, conducted near Essex in the UK, were largely set up to demonstrate the enhanced firepower of the new 76mm gun mounted in 100 M4A1 Shermans that Ordnance had rushed to the UK in anticipation of the D-Day landings, and also of the new 90mm tank gun that was being mounted in upgraded M10A1 TDs (to be re-named M36) in the states in preparation for shipment to ETO.  The primary interest seems to have been demonstrating against the armor levels expected in Tiger tanks -- Phase 1 firings were against 120mm plate at 30 degrees, Phase 2 were against 100mm plate at 30 degrees.  But the test firings included a Phase 3 firing set against spaced armor plates ... at 50mm plates that also had a 20mm plate 6 inches in front.  These Phase 3 firings demonstrated how such an arrangement could initiate the fuzing of US AP shells leading to failure against the 50mm plate, in an environment where British AP shot (solid penetrators) or even inert-filled US AP shells would penetrate completely.  

 

However, this testing set-up does not mimic Schurzen. Rather, it appears to mimic Vorpanzer, a rarely seen German add-on armor kit produced for Pz IV with the notion of enhancing the protection of tanks that would lead assault waves against prepared defenses.

 

I have test results from other firing tests, such as Bazookas against Panthers, or US 37mm, 57mm, 75mm and 105mm rounds, including 105mm HEAT and 75mm HE and WP, against various test targets. But I have no primary sources for HEAT or AP projectiles against Schurzen.

 

The test firings of the bazooka against Panther does tend to lead one to the conclusion that just about ANYTHING between the projectile and the target plate will help defend against penetration. Wheels, tires, exhaust pipes, even tow hitches were struck by projectiles in those tests, and while bazooka rounds clearly penetrated with lethal effect when striking the armored plate cleanly on sides or rear, when they struck these various stand-off protrusions the side or rear armor was effectively protected from penetration.

 

Best I got, boyz.  Hope it helps.

 

-Mark

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#13 Bob Benge

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Posted 06 April 2017 - 06:04 PM

Thanks Mark! 

 

Great Info!


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#14 Mark 1

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Posted 10 April 2017 - 08:23 PM

"However, this testing set-up does not mimic Schurzen."

 

Hmmm.  Going back through the Shoeburyness report, it appears that there is one reference to Schurzen style plates.  To wit:

 

 


Inclosure No.2

ARMORED FIGHTING VEHICLES & WEAPONS SECTION
APO 887

SUMMARY OF CONCLUSIONS FROM ORDNANCE BOARD PROCEEDINGS No. 26495

1. 75mm APC M61 Inert loaded and Explosive "D" loaded have similar maximum perforative performances against single homogeneous plate.

2. Against a spaced plate assembly consisting of 20mm homo plate in front of 50mm FH plate, the shell failed at all velocities up to the velocity of the gun. The same shell, but with empty fuse succeeded against this target at velocities above 1780 f/s (equivalent to a range of about 850 yards with a MV of 2050 f/s). The failure of the filled and fused shell must be attributed to fuse action and detonation between the plates.

3. Against 70mm homo plate at normal or 60mm and thinner plates at 30ยบ the shell was as successful as shot and gave detonations at distances of up to 20 feet in rear of the target.

4. The effect of 5mm and 8mm skirting plate in front of 30mm homo plate did not affect the performance and successful functioning of the fuse.

 

Clearly, the #4 conclusion is a reference to Schurzen level plating over side armor.

 

However, in looking at the accounting for all shots in the three phases of firing, there are no shots listed as against this "5mm and 8mm shirting plate in front of 30mm homo plate".  So I don't know what data drove this conclusion, but clearly someone thought that Schurzen would not impede penetration by 75mm M61 APC rounds.

 

Here is another piece of data from the report, which appears to be a chart of combined data (on 75mm M61 penetration testing) from TWO test firings ... Proceedings 269594 (I believe this is the Shoeburyness tests) and an earlier test firing listed as Proceedings 23114.

 

Perhaps the testing against Schurzen level plating was part of that ealier test firing.  Don't know ... don't have anything more on that event.

 


CONSOLIDATION OF DATA FROM ORDNANCE BOARD PROCEEDINGS 23114 AND 26594

75mm APCBC M61 - HE filled versus Inert loaded

 

Ordnance%20Test%20Firing%20of%2075mm%20M

 

Still no genuine primary data on the effects of Schruzen....

 

-Mark


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