Tiger I armor plate quality

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Miles Krogfus
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Tiger I armor plate quality

Post by Miles Krogfus » 26 May 2015 21:02

Kummersdorf August 27,1942 test of Dortmund Horde Hutten Verein (DHHV) 37HB75 analysis plate for the company's use on the Tiger. Given are the plate thickness (T) equivalent thickness from the projectile's official armor pen. curve (ET) Brinell Hardness of plate (HB) angle of strike (A).
T 60.4 mm ET 64.4 HB 285 A 44.5. T 70.2 ET 71.4 HB 290 A 29.5. T 80.3 ET 80 HB 280 A 0. T 90.2 ET 83.3 HB 270 A 31. T 100.2 ET 96.3 HB 270 and A 6.5. T 110 ET 90.9 HB 270 A 0.
DHHV 37HB75 plate at Aberdeen: Tiger I Lower hull side (LHS) T 63.25 ET 60.8 HB 285 A 55 P M82. Lower hull front (LHF) T 102.6 ET 85 HB 270 A 30 P M82. Driver's plate (DP) T 103.9 ET 109.4 HB 305 A 0 P M72.
DHHV analysis C81 Aberdeen: Upper hull side (UHS) T 81.8 ET 92.5 HB 340 A 30 P M62. Turret side (TS) T 81.3 ET 77.5 HB 330 A 0 P M62. DP T 102.1 ET 89 HB 295 A 0 P M62.
Krupp PP7182 plate Aberdeen: Lower hull side (LHS) T 61.5 ET 57.3 HB 310 A 0 P M72. Second LHS T 62.5 ET 66.8 HB 315 A 45 P M62. UHS T 81.3 ET 89.8 HB 330 A 0 P M72. Same UHS ET 87.8 A 45 P M82. DP T 106.4 ET 107.7 HB 295 A 30 P M82.

Miles Krogfus
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Re: Tiger I armor plate quality

Post by Miles Krogfus » 28 May 2015 02:17

The peforation figures (ballistic limits) for the ABL Tiger I tests: N Naval, Army limits.
DHHV 37HB75: LHS M82 2491 NI, DP M72 1991 N, LHF M82 2277 NI
DHHV C81 TS M62 1774 NI, UHS M62 2424 Ni, DP 2006 N
Krupp PP7182 LHS #1 M72 1098 A, LHS #2 M62 2409 NI, UHS M72 1536 A, M82 2680 N, DP M82 2395 NI

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Re: Tiger I armor plate quality

Post by Miles Krogfus » 04 Sep 2019 00:33

Here are the figures for the 1942 DHHV tests of its Tiger plate and those from the Aberdeen tests of 3 Tigers. and pages 2 and 16 from the ABL report. Note that 1 of the 5 original DHHV 37HB75 plates was superior (in green), 2 inferior (in red), 1 of the 3 37HB75 Aberdeen plates and 1 of the 3 newer DHHV C81 plates superior, 1 inferior. Of the 5 Krupp PP718 plates, 3 were superior, 1 inferior.
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Mobius
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Re: Tiger I armor plate quality

Post by Mobius » 04 Sep 2019 02:33

The yaw issue calls into question the long range effectiveness of the 76mm M62 shell. Maybe that is why they went to the 1/32 rifling. The windscreen should only absorb about 1mm in penetration.

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Re: Tiger I armor plate quality

Post by Peasant » 04 Feb 2020 14:20

Mobius wrote:
04 Sep 2019 02:33
The yaw issue calls into question the long range effectiveness of the 76mm M62 shell. Maybe that is why they went to the 1/32 rifling. The windscreen should only absorb about 1mm in penetration.
I don't believe this is correct. If I understand correctly, the text is saying that the yaw was only an issue at short ranges and the projectile becomes more stable as it flies further.

critical mass
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Re: Tiger I armor plate quality

Post by critical mass » 05 Feb 2020 19:25

As you might notice, it was expressed that the M62 & M82 APCBC cannot be relied upon to stay intact against ca. cal t/d plate when the obliquity exceeds 25deg.

This seems a serious constraint to me, and might indicate known problems with projectile quality.

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Re: Tiger I armor plate quality

Post by Mobius » 05 Feb 2020 20:06

Peasant wrote:
04 Feb 2020 14:20
Mobius wrote:
04 Sep 2019 02:33
The yaw issue calls into question the long range effectiveness of the 76mm M62 shell. Maybe that is why they went to the 1/32 rifling. The windscreen should only absorb about 1mm in penetration.
I don't believe this is correct. If I understand correctly, the text is saying that the yaw was only an issue at short ranges and the projectile becomes more stable as it flies further.
My reading is that the projectiles without windshields become more stable at greater range. Though this could mean the difference in penetration between with and without is greater at longer range meaning the windscreened projectiles are just that much worse at longer range.

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Re: Tiger I armor plate quality

Post by Peasant » 05 Feb 2020 20:11

critical mass wrote:
05 Feb 2020 19:25
As you might notice, it was expressed that the M62 & M82 APCBC cannot be relied upon to stay intact against ca. cal t/d plate when the obliquity exceeds 25deg.

This seems a serious constraint to me, and might indicate known problems with projectile quality.
Yes, I've noticed, but I thought these were two separate issues?

P.S. Did you notice the completely penetration of the Tiger's 102mm front plate at only 2006fps? What do you think, flawed plate or something else?
Mobius wrote:
05 Feb 2020 20:06
My reading is that the projectiles without windshields become more stable at greater range. Though this could mean the difference in penetration between with and without is greater at longer range meaning the windscreened projectiles are just that much worse at longer range.
"Analysis of the above table indicates that the windshield reduces the penetrative ability of the projectile when fired under the conditions listed at the begining of this paragraph..."
which were:
"...firing the 3" M62 APC projectiles at 50 yards..."
and
"Therefore the data obtained with projectiles fired without windshields was considered more reliable..."
Aka more indicative of the performance of the projectiles w/ and w/o windshields at longer ranges.

Edit: Found some info about the AD-P160 project: https://imgur.com/a/MO99y01

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Mobius
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Re: Tiger I armor plate quality

Post by Mobius » 05 Feb 2020 21:12

Like I was saying the shorter the range the less yaw from windscreen.
yallyaw.jpg
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Re: Tiger I armor plate quality

Post by Peasant » 05 Feb 2020 22:17

Mobius wrote:
05 Feb 2020 21:12
Like I was saying the shorter the range the less yaw from windscreen.
yallyaw.jpg
Alright, it must be true then. I don't know enough about external ballistics to argue about this. :)

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Re: Tiger I armor plate quality

Post by critical mass » 06 Feb 2020 11:29

There is a distinct windscreen effect. dr. Hershey filed a report on it (edit: link added). The windscreen is dead metal and causes a reduced penetration compared to bare nosed projectiles, similar to how AP-caps are reducing penetration, if the projectile manages to avoid break up. In other words, any metal used for windscreens need to be accelerated together with the projectile but does not contribute to penetration itselfe. Quite the opposite, the energy required to tear off the screen is wasted from the projectiles energy pool.

The effect is small but measurable:
https://apps.dtic.mil/dtic/tr/fulltext/u2/063985.pdf

Unstability at reduced discharge velocity and short range can be related to many reasons. Time and time again, blame is laid upon windscreens but my experience in related cases suggest, that this blame almost always is not substantiated by follow experimentation. More often than not, the causes can be tracked down to driving bands separating or deforming badly after discharge due to to rapid increase of angular velocity as the projectile moves down the barrel. Also, when a projectile is discharged at , say 2400 FPS rated and laid out with a given spin / stability condition, it will have Lower stability if it is discharged at lower than rated velocity.

Comparing the M62 and M72 attack at drivers plate, where both projectiles managed to penetrate intact at 0deg and 2006 (611.4m/s, K=1984) and 1997fps, respectively, I don’t see anything odd here. Instead of assuming inferior plate quality, I infer from the differences in %eqT that the domestic reference armor penetration curve (which was computed based upon the Thomspon formula) is the culprit here, thus, providing misleading assessments on the plate quality. It’s probably relevant that here, both projectiles stayed intact, and I suppose that for the M62, that generally was not the case in the domestic US armor curve. Tentatively, I am inclined to attribute it to a case of best quality projectile.
I have data for the 75mm Pzgr39 attacking 100mm plate in intact condition. It obtains complete penetration (by german definition) at K=1975, which is close enough to what we have seen for the M62 in order to assume its in the right ballpark for what an intact projectile can be expected to achieve against this 100mm 95 kg/mm^2 german RHA at 0° impact.

Notice that both M62 and M72 BL were reported for projectiles without windscreen, thus giving somewhat better results as long as the projectile stays intact compared to service projectiles (aforementioned windscreen effect). The same plate was attacked by M62 with windscreen fitted. The BL(P) was 2152fps /656m/s, K=2129. This is >8% higher than the data I have seen for the 75mm pzgr 39 and 76mm Pzgr 39 rot attacking 100mm plate. I suppose, this M62 projectile broke up earlier due to the inability to make a hole through at this elevated velocity.
Again, considering all variances, I don’t see a problem here but rather a range of quality differences on the projectiles.

These are 0 deg impacts, where projectile damage is least heavy. Still, I suppose the projectiles will start to break up against such a plate at higher velocities. If they break up, they can’t perforate easily, thus creating a dilemma, with only a small window where a good quality projectile can perforate a low enough velocity to avoid projectile break up/shatter.

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Re: Tiger I armor plate quality

Post by Yoozername » 06 Feb 2020 17:58

dupe
Last edited by Yoozername on 06 Feb 2020 21:48, edited 2 times in total.

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Re: Tiger I armor plate quality

Post by Yoozername » 06 Feb 2020 21:48

I guess there are windshields and then there are windshields. The German version for the Pzgr 39 (on the right) was smaller than the US version on the left. I believe the Germans tried aluminum also? I expect Al to just vaporize.

Also note the different cap designs.

For the German Pzgr 39 meeting armor at 700 M/s (as an example), the 'crush-time' (event between when BC first contacts armor and penetrating cap then contacts armor) is around ~72 uSecs. The mass of the AP+Cap of the projectile, compared to the ballistic cap is orders of magnitude greater? I believe the BC is just crimped on, not soldered on like the penetrating cap? It would be interesting to see it with modern high speed photography.

Great report there.
75.jpg
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Re: Tiger I armor plate quality

Post by Yoozername » 11 Feb 2020 19:41

Actually, I believe the Germans used Al in the explosive, not the ballistic cone. I read a report where the Germans wanted feedback on the effects of this.

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Re: Tiger I armor plate quality

Post by critical mass » 11 Feb 2020 20:16

The German navy indeed used an Aluminium alloy for windscreens of their major caliber L/4.4 Psgr. AP projectiles.
It’s for this little effect- and to remove the pointed windscreen when hitting the water in order to have a blunted projectile front (the ap cap) for stable underwater trajectory.

Such detail optimization wasn’t required for army purposes, though.

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