How to calculate HE penetration?

[Claus B]

Originally posted by Mr. Tittles:

I am not too familiar with the shape of these tanks but maybe someone can confirm:

1. Is there supposed to be a big rivet at about 11 0'clock from the center of the hit?

Yes.

Originally posted by Mr. Tittles:

2. Does the outer armor appear to be buckled in somewhat?

Either that or the explosion has eroded some of the material, creating a shallow cone towards the point of impact.

Originally posted by Mr. Tittles:

It certainly appears to be a HE shell and not HEAT. From the blast area, It appears that it came from a flat trajectory. Is the outer armor not as hard as the inner armor?

The outer armour would be on average harder (IT80 = bhn 300-331) than the inner armour (IT110= bhn 260-310).

Originally posted by Mr. Tittles:

I would concur that it appears that the HE went off after 'stalling' at the inner armor. Would be nice to know what internal effcts it had if any.

The tank is that of Lt. Cloudsley-Thompson which was hit by Wittmann as he drove into Villers-Bocage, but from the account of the lieutenant, it would appear that it was hit by AP after which the tank was abandoned. The HE-hit on the turret could well be from another occasion later in the day.

As for the account on the panzerace.net site, I think it gives a rather distorted view of what happened (in fact, the term "fairy tale" springs to mind...) In any case, the Cromwells in Villers-Bocage and on RN 175 were certainly not abandoned before they were hit.

Claus B

[ October 04, 2003, 06:41 AM: Message edited by: Claus B ]

[Mr. Tittles]

Thanks.

Is that armor spaced on the Cromwell? Its certainly appears to have stood up to the energetic event. But in the picture, the un-penetrated inner layer seems to be without an air gap.

The picture just makes me wonder what it would be like to stand on the inside of the turret when such a blast takes place. Metal being a good conductor for heat/vibration and all.

If ammo was directly on the other side of the armor, could sympathetic detonation occur? I believe western allies/germany used a stable HE in shells but what about the fuzes in the shells? powder?

I was thinking about the fragmentation from this Cromwell hit. It dawned on me that the shell splinters, which would normally be ejected sideways, would get a forward vector from the HV shell. That is, the armor would be extensively carved up by shrapnel that would normally be directed away from a lower velocity shell. This does seem to have happened in the pic. Anyone know escape velocity for shell splinters? I would imagine it depends on the size of the splinter.

Another thing about splinters, it occurs to me that a shell rotating at a high speed from rifling unleashes this energy into the splinters when the shell breaks up.

[Mr. Tittles]

http://www.battlefield.ru/destroyed/germany/panther_11.jpg

http://www.battlefield.ru/destroyed/germany/panther_10.jpg

This pics show panthers that have been hit by large caliber HE shells. The side armor in both cases shows holes bigger than the warhead and irregurly shaped. Almost like broken plastic. One panther appears to have the zimmerit blasted away suggesting HE detonated outside.

[Mr. Tittles]

As for the account on the panzerace.net site, I think it gives a rather distorted view of what happened (in fact, the term "fairy tale" springs to mind...) In any case, the Cromwells in Villers-Bocage and on RN 175 were certainly not abandoned before they were hit.

Claus B

It does not say they were abandoned, but rather were unmanned at the time of the attack. If anything, it downplays the rampage by saying that British AFV were destroyed easily because they weren't crewed up at the time.

I would like to know if the other German AFV destroyed armor before they were KO'd themselves. The whole battle seems clouded in lore.

[Redwolf]

Originally posted by Mr. Tittles:

http://www.battlefield.ru/destroyed/germany/panther_11.jpg

http://www.battlefield.ru/destroyed/germany/panther_10.jpg

This pics show panthers that have been hit by large caliber HE shells. The side armor in both cases shows holes bigger than the warhead and irregurly shaped. Almost like broken plastic. One panther appears to have the zimmerit blasted away suggesting HE detonated outside.

To me, picture number 10 looks more like a brittle plate, bad steel from alloy missing components late in the war.

I think if this was a HE explosion in contact with this plate, then the edge of the hole would be bent in, which it isn't. I think this damage is more likely to be caused by an AP shot almost from front, hitting the side plate at a very high angle.

On the other hand, below the hole on the side hull you see the towing cable apparently pushed downwards which would fit a HE theory.

[ October 04, 2003, 07:56 PM: Message edited by: redwolf ]

[Mr. Tittles]

http://home.vicnet.net.au/~antitank/Publications/It_Happened_II/Chapters/Tally_Ho_/tally_ho_.htm

this site claims that japanese tanks were destroyed with 2 #'er HE shells. actually used/prefered because the ap was just wizzing through!

[JasonC]

Rexford is right on delay fuses, which are not variable as Redwolf said. The 1/20th of a second delay is standard on US HE, not limited to 75mm, and is still used today.

This is a screw setting on the plain vanilla fuse. In one position, the screw detonates the shell "quick" - microseconds. Turn it one half turn and it detonates "delay" - 1/20th of a second after impact.

Don't confuse this with time fuses. Those can indeed be dialed for a time to detonation as Redwolf says, but not a time -after- impact. With time fuses it is the time -since firing- that is set as the gunner wants, to e.g. get a burst at a certain altitude.

Fuse quick is generally used for targets in the open. Fuse delay is used against targets in cover, e.g. buildings or trenches. You want the shell inside the obstacle or buried to give its full HE blast - whereas with quick you want rapid dispersal of shrapnel.

Against such targets the 1/20th of a second would typically be enough for the shell to come to rest. But it is nothing like "5 seconds". You would use delay against an armored target.

As for how HE shell is made, from what I've found (I'm not expert) it is generally forged not cast. That is, heated steel sheet is wrapped around a lathe and then mechanically compressed to thin it out to about the desired thickness. Final finishing, shaping the nose etc is by spinning and machining on a lathe.

[flamingknives]

So how thick is the casing of a standard HE shell?

[Mr. Tittles]

I have a book with a cross section of a 7.5cm L24 AP round (K. Gr. rot Pz).

This actually has a very large HE cavity for a AP round. The cavity extends into the shell over 60% of its length. The cavity narrows as it approaches the front of the AP shell. At the thinnest part of the shell, the walls are approx 20mm or so but this tapers inward as I said before.

The fuze and tracer element take up a considerable space by the way. This would be a base acting fuze. This diagram shows the shell to be a APCBC. The Panzer IV website claims this L24 AP round to be a APC.

A cross section of the L48 AP round shows the HE charge to be much less and the walls much thicker.

I do not have any sources/diagrams on the 75mm HE rounds. Logic would suggest from the payloads listed at the Panzer IV website, that the walls would be much thinner.

[ October 05, 2003, 11:17 PM: Message edited by: Mr. Tittles ]

[Claus B]

Originally posted by Mr. Tittles:

It does not say they were abandoned, but rather were unmanned at the time of the attack. If anything, it downplays the rampage by saying that British AFV were destroyed easily because they weren't crewed up at the time.

But they were crewed at the time. The only tanks "unmanned" were those that the British destroyed themselves on Hill 213 long after the Wittmann had left the scene.

As it were, the "rampage" was not quite what it is made up to on the said homepage and indeed in numerous other accounts.

Originally posted by Mr. Tittles:

I would like to know if the other German AFV destroyed armor before they were KO'd themselves. The whole battle seems clouded in lore.

Only because it has only recently (well, in the last 10-15 years) been subjected to carefull study. David Taylors book mentioned above is a good place to start if you want to get the most recent interpretations.

Claus B

[Mr. Tittles]

I have a pic of a M48 HE round (75mm)in cross section. It is roughly 11-12 mm as far as shell wall thickness. A big factor is that the front fuze screws into this shell. that part that has these threads actually gets thinner! i would imagine the fuze would just disintegrate/melt when the HE round would strike armor. the shell would then be akmost open ended and trying to push through the armor.

I also downloaded a M64 WP cross section. These white phos shells apparently are the same as HE shells. The burster charge to crack it open acually seems to be a cylindrical centrally positioned HE charge that runs from the front fuze to the back of the shell. Almost like a stick of dynamite if you will. These WP shells had to be deadly affairs because of the burning chemicals but also from the blast and resultant fragments. A spinning shell from a rifled gun has a lot of energy. This energy would be released into the fragments when the burster cracked open the shell.

I only own CMBB. Are these WP shells very lethal in CMBO?

[ October 05, 2003, 08:37 PM: Message edited by: Mr. Tittles ]

[Mr. Tittles]

http://www.vietvet.org/arty.htm

I wonder about HE being set off in microseconds. This site claims a millisecond or so.

[flamingknives]

I only own CMBB. Are these WP shells very lethal in CMBO?

"The offensive properties of WP shells are not modelled in CM to prevent ahistorical overuse"

So it says in the manual.

[Mr. Tittles]

I have tried to contact the owner of the panzer IV universe website regarding possible errors in the data.

I still can not believe that reinforced concrete would withstand either HE or AP better than ordinary steel. The armor penetration values seem correct for 90 degree armor but I would suspect that the steel and concrete values are reversed.

Also the HE content of the german 75mm Sprgrntn (34) is listed at 0.853 Kg. This is 1.87 lbs. This would seem high. Almost like a mortor rounds filling. more HE than the 88mm I believe.

[Mr. Tittles]

Originally posted by rexford:

PzKpfw IV Universe site presents penetration against vertical armor.

Comparing this to Combat Mission numbers shows the CM numbers to be higher across the range spectrum.

[Mr. Tittles]

Will answered my email....

The article from which these data were derived is based directly on data that came from the APG. I've verified that the data on my web page is accurate relative to the article, though I can't, of course, guarantee the accuracy of the article itself.

I'm not an expert in ballistics, but I believe concrete is indeed tougher than steel, but not inch for inch. IOW, steel one inch thick is tougher than concrete one inch thick. So it could be that the APG's testing compared penetration of steel plate of specific thicknesses against concrete of infinite thickness (they just measured how deep the round went into the concrete -- how deep the hole/pit/crater was). This might make sense because, somewhat unlike a duel with another tank, to destroy a bunker an attacking tank must generally fire multiple rounds and the damage is very much cumulative.

The problem is that the requisite amount of concrete is prohibitively heavy for use in armoring an AFV, and hence the popularity of steel. And yet the Germans did actually use concrete to protect the driver on certain versions of StuG.

--Will

[Stalin's Organ]

Originally posted by Claus B:

</font><blockquote>quote:</font><hr />Originally posted by Mr. Tittles:

It does not say they were abandoned, but rather were unmanned at the time of the attack. If anything, it downplays the rampage by saying that British AFV were destroyed easily because they weren't crewed up at the time.

But they were crewed at the time. The only tanks "unmanned" were those that the British destroyed themselves on Hill 213 long after the Wittmann had left the scene.

</font>

[K_Tiger]

I'm not an expert in ballistics, but I believe concrete is indeed tougher than steel, but not inch for inch. IOW, steel one inch thick is tougher than concrete one inch thick. So it could be that the APG's testing compared penetration of steel plate of specific thicknesses against concrete of infinite thickness (they just measured how deep the round went into the concrete -- how deep the hole/pit/crater was). This might make sense because, somewhat unlike a duel with another tank, to destroy a bunker an attacking tank must generally fire multiple rounds and the damage is very much cumulative.

The only comparsion i read was the ballistics of the Dora gun... the 7 tonn bullet was able to go thrue 8 meter concrete and 1 meter of steel. Maybe this helps a bit.