'French' M4A2 hit by German gun(most likely 88)

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seppw
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'French' M4A2 hit by German gun(most likely 88)

#1

Post by seppw » 16 Mar 2018, 23:36

sherman.png
Because of edge effect the shell didn't need as much KE in order to penetrate the front section as it would have, had there been more plastic deformation, but it rotated the shell upwards so that the shell entered the upper part of the turret at a very terrible angle. It looks a little sureal that the shell managed to get through nonetheless.
What's even more interesting about this image imo is that it can potentially spark the idea for composite armor elements like perforated steel plates or perhaps NERA.

Richard Anderson
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Re: 'French' M4A2 hit by German gun(most likely 88)

#2

Post by Richard Anderson » 16 Mar 2018, 23:51

Interesting. I know of only one M4A3E2 in French hands, but was unaware it had been hit and penetrated.
Richard C. Anderson Jr.

American Thunder: U.S. Army Tank Design, Development, and Doctrine in World War II
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seppw
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Re: 'French' M4A2 hit by German gun(most likely 88)

#3

Post by seppw » 17 Mar 2018, 00:05

Richard Anderson wrote:Interesting. I know of only one M4A3E2 in French hands, but was unaware it had been hit and penetrated.
I wrote "M4A2", because that's what the source stated. Did you misread or are you saying this isn't an M4A2?

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Re: 'French' M4A2 hit by German gun(most likely 88)

#4

Post by Richard Anderson » 17 Mar 2018, 00:09

seppw wrote:
Richard Anderson wrote:Interesting. I know of only one M4A3E2 in French hands, but was unaware it had been hit and penetrated.
I wrote "M4A2", because that's what the source stated. Did you misread or are you saying this isn't an M4A2?
Ooops! Misread...I've been working in the garden and am more tired than I thought. :D
Richard C. Anderson Jr.

American Thunder: U.S. Army Tank Design, Development, and Doctrine in World War II
Cracking Hitler's Atlantic Wall
Hitler's Last Gamble
Artillery Hell

critical mass
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Re: 'French' M4A2 hit by German gun(most likely 88)

#5

Post by critical mass » 17 Mar 2018, 08:55

Cast armor, with well rounded up corners, isn´t suffering edge effects as is known from straight RHA plate with well defined corners.
The reason is that the shockwave tranferred very quickly to the back of the plate and reflected from it doesn´t hit radially an acute contoured line but spread over a wide arc and thus is refracted.

Cast armor is inferior to plain resistence compared to a flat RHA plate of infinite dimensions by 15-20% (You cannot well controll grain growth and You cannot -at all- controll grain orientation in cast armor), however, cast armor isn´t much suffering by plate edge effects when well made and straight lines are prevented (note that straight cutouts for sight apperatus or gun barrel will again have edge effects).

seppw
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Re: 'French' M4A2 hit by German gun(most likely 88)

#6

Post by seppw » 17 Mar 2018, 11:29

critical mass wrote:Cast armor, with well rounded up corners, isn´t suffering edge effects as is known from straight RHA plate with well defined corners.
The reason is that the shockwave tranferred very quickly to the back of the plate and reflected from it doesn´t hit radially an acute contoured line but spread over a wide arc and thus is refracted.

Cast armor is inferior to plain resistence compared to a flat RHA plate of infinite dimensions by 15-20% (You cannot well controll grain growth and You cannot -at all- controll grain orientation in cast armor), however, cast armor isn´t much suffering by plate edge effects when well made and straight lines are prevented (note that straight cutouts for sight apperatus or gun barrel will again have edge effects).
sherman.png
Interesting read though. I learn something new almost everytime I read one of your posts, critical mass. Thanks!

Here's a different angle btw:
sherman2.jpg

Yoozername
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Re: 'French' M4A2 hit by German gun(most likely 88)

#7

Post by Yoozername » 18 Mar 2018, 02:03

I also was confused by the 'edge effect' you are referring to. The 90 deg edge you are pointing to is the 'cheek armor' welded onto sherman cast turrets that had a weak spot, and the cheek armor covered it. I am not sure if it is certain that is one strike or two. One above the other. The top penetration is striking a sloped part of the upper turret.

Clearly, the effects were devastating from the video that picture comes from. A high order 88 mm AP detonation, and the amount of armor pushed in, apparently beheaded one tanker and gave another a massive torso laceration. Hopefully, a quick death. The tank does not appear to have burned.

seppw
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Re: 'French' M4A2 hit by German gun(most likely 88)

#8

Post by seppw » 25 Mar 2018, 19:27

Yoozername wrote:I also was confused by the 'edge effect' you are referring to. The 90 deg edge you are pointing to is the 'cheek armor' welded onto sherman cast turrets that had a weak spot, and the cheek armor covered it. I am not sure if it is certain that is one strike or two. One above the other. The top penetration is striking a sloped part of the upper turret.

Clearly, the effects were devastating from the video that picture comes from. A high order 88 mm AP detonation, and the amount of armor pushed in, apparently beheaded one tanker and gave another a massive torso laceration. Hopefully, a quick death. The tank does not appear to have burned.
Assuming the source is right and this was done by a 88 and assuming what you're suggesting, that the edge effect didn't force the round upwards too much, the "lower" hit would have gone right though at any realistic combat distance.

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Re: 'French' M4A2 hit by German gun(most likely 88)

#9

Post by Yoozername » 26 Mar 2018, 20:04

The 'edge-effect' is generally referring to a case like the hatch on the front of a T-34. That is, the weakness that having the projectile strike near that edge brings. I don't think that this sherman is a case of that.

It would be difficult to say what actually happened in that video without some after-action report. What is known is that at least two tankers were (massively) physically harmed in a AFV that does not appear to have had a catastrophic detonation of it's own ammunition.

This panther might show the effects of the failures near the MG.

Image

critical mass
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Re: 'French' M4A2 hit by German gun(most likely 88)

#10

Post by critical mass » 31 Mar 2018, 19:04

If the perforation hole or porjectile shoulder physically touches a free, unsupported edge, the loss in aequivalent thickness reaches 15%.
This linearely drops to close to zero if the projectile side walls are ca. 1.5 diameters distant to the nearest plate edge.
Supports by buttressed plates, overlaps, keys and welds tend to mediate the loss in resistence, though by how much is contested and conditional.

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