Specific event: T-34(76mm) vs PIV H (late)

[Kauz]

I had a test scenario running....and i want to tell you one occasion which was a little disturbing.

A Panzer IV H(late) was fighting a T-34(76mm) on a distance of 1500 meters.

Then i saw a hit ....The T-34 hit the front upper hull at the good angled part , far under the driver slit. It was (a little) above the edge which lead us to the lower hull.

The message was "front upper hull penetration".

No weak point like the driver sight slit was hit !

...It was more like the best armored and angled point of the PIV got the hit.

One of the PIV crew members got killed...but it was the radio operator at the hull Machine gun ...not the driver which i would suspect to be injured first or at least additionally to the hull gunner who was on the other side.

Okay Okay....it might be possible that the side-wards flying shrappnells of the exploding round could hit the hull gunner....and the driver because of fortuna did not got hurt anyway.

...But let me continue...

Like you would suspect the penetration of the front upper hull at 1500meters would be done by a tungsten core round of the T-34....but no...it was done by a standard AP round....

I know it is only a specific occasion and someone will argue it is a statistic issue or may hit a weak point of the armor and that the hit decals are not correct ...may be ...yes......but nevertheless i wanted to share the event with you and ask you for your experiences with armor and penetration events.

[Kieme(ITA)]

The only thing I would suggest here is to make some screenshots or videos next time, it's much more informative than this.

Impossible to comment on these lines without a reference...

Besides, what number or reiteration was this case on? How many reiterations had the test? What kind of conditions were set for the test? Too many missing points to call a test and show a result. Can't really comment on this.

Out of curiosity:

What's "the best armored and angled point of p4"?

[Kauz]

The only thing I would suggest here is to make some screenshots or videos next time, it's much more informative than this.

Impossible to comment on these lines without a reference...

Besides, what number or reiteration was this case on? How many reiterations had the test? What kind of conditions were set for the test? Too many missing points to call a test and show a result. Can't really comment on this.

Out of curiosity:

What's "the best armored and angled point of p4"?

It was a specific event...no iterations....i never intended to make a statistic talking....i think i made this clear in my post.

Video not necessary....both units elite (all maximum), both shot around by own decision....all what you have to know is what i told.....there are no other points which you have to know......if there are others just tell me in specific!

Here is picture where i marked for you the exact position of the hit decal:

http://www.directupload.net/file/d/3644/hgauco5z_jpg.htm

This picture also should answer your last question.

[Oddball_E8]

First: Shot from 1500m would be at an angle (not that flat a trajectory at those ranges).

Second: Shot at that distance from that gun COULD penetrate the PzIV's front armour at that range.

Third: Damage after penetration could very well hit and kill radio operator. Schrapnel, riccochets, explosions whatever could happen after impact and penetration.

[Kieme(ITA)]

" I was running a test scenario", so I assumed this was a test.

That part of panzer4 armor is indeed upper hull, nothing strange there. Besides, while being angled, that armor plate is not the thicker part of front armor, in fact, it's the thinner (just search for any pz4 armor layout scheme, should be 20/30mm if I remember correctly). The armor plate we are talking about the is the one connecting the front piece where mg and driver's slit are located and the lower front armor, it's thin not for a case and it holds the hatches used to access the front transmission.

And considering what Odd suggests about the angle from which a shot lands on its target when the range is 1500m you could assume that much of that armor angle was negated.

Can a 76mm AP penetrate 20/30mm of armor at 1500m with a shot Landing at not extreme angle? Well, if it punches through 60mm at 1000m and 40mm at 2000m (just search for any penetration table reference) I'd say yes, it can.

As regarding what the projectile did inside, there's aproximation, and we still don't exactly know the angle it came from.

So I'd say the game here shows results you could came up with a little of research, I see nothing strange, but for the crew hit, but it can be explained as Odd did too.

Oh, by the way "there are no other points you need to know" is not exactly the right foot to start a discussion on a forum...

[Vanir Ausf B]

The angle of decent for Soviet 76mm at 1500 meters would be around 1.5 degrees, so that is not really a major factor.

The problem with single events like this is that we don't know for sure if CMx2 models weak point penetrations. We do know that there is no weak point penetration hit text so the only way to find out if there is a problem is further testing.

[Kieme(ITA)]

Got it, it was 20 not 30, 20mm:

Even considering the extreme angle the armor there is pretty weak, for sure not the best armored part of pz4 front.

Some mathematics to see the effective armor on that point: 72 degrees from vertical (according to that drawing, might be different), 20mm of armor:

T_L=\frac{T_N}{cos(\theta)}

where

T_L: Line of sight thickness

T_N: Normal thickness

\theta: Angle of the sloped armour plate from the vertical

Cos72 is .3090, let's cut two degrees as Vanir suggests, Cos70 is .3420

20/0.3420 = 58.4mm of effective armor.

I am a pig at maths so maybe I did something wrong, mind this step.

Now the ball goes to penetration tables.

Some state 50mm penetration at 1000m, some state 60mm. I like this one:

http://english.battlefield.ru/specification-and-armor-penetration.html

65mm (at 90° that is equal to the effective armor we calculated)? Against the 58.4 we calculated? Good match (even at 50mm it would be, because 8mm of armor penetrated or not could really go to the chance factor)

Now, let's not forget we could add armor quality and projectile quality to the above, thus adding or reducing an X value from the true armor value and penetration value, (considering that armor quality in 1944 was descending for the germans, while projectile quality was raising for the russians)

All in all I'd say the penetration is nothing strange, too many variables and too many doubds on penetration tables, which are not 100% reliable, to be scientific about this, but I'm happy with the research, thumb's up for CMRT.

Now that I think of it the tank also took fire? Who knows what happened inside, yet the transmission might be hit, leading to a fire, thumb's up again for CMRT.

[Vanir Ausf B]

For this time period the most likely 76mm ammo would be BR-350B which penetrates 55mm of RHA at 1500 meters, according to WW II Ballistics.

[Vanir Ausf B]

Also keep in mind that in CMx1 the Pz IV ausf H and J were modeled as having armor quality of less than 100% and this is likely true in CMx2. Using Kieme's number, an armor quality rating of 95% would knock the effective thickness down to about 55-56mm.

[JonS]

maths and stuff

Don't forget that while the straightline path through the armour is 58mm (or there abouts) that the plate is still only 20mm thick. Meanwhile the diameter of the incoming round is three, almost four times that wide.

Consider, hypothetically, a plate of armour that is 2 metres wide x 2 metres deep x just 1 milimetre thick. Assume an incoming 76mm round strikes exactly on the edge of the plate, parallel to the flat plane. Using naïve maths that incoming round has a full 2 metres of armour plate to go through before it comes out the other side, which is theoretically impossible. But it should be obvious that actually it won't have much trouble at all slicing through the whole plate with plenty of energy to spare.

The same principle would apply to the 76mm round hitting the 20mm plate.

Armor obliquity effects decrease as the shot diameter overmatches plate thickness in part because there is a smaller cylindrical surface area of the displaced slug of armor which can cling to the surrounding plate. If the volume which the shot displaces has lots of area to cling to the parent plate, it resists penetration better than if that same volume is spread out into a disc with relatively small area where it joins the undisturbed armor. Plate greatly overmatching shot involves the projectile digging its own tunnel, as it were, through the thick interior of the plate. It was found experimentally that the regions in the center of the plate produced the bulk of the resistance to penetration, while the outer regions, near front and rear surfaces, presented minimal resistance because they are unsupported. Thus, an overmatched plate will be forced to rely on tensile stresses within the displaced disc, and will tend to break out in front of the attacking projectile, regardless of whether the edges cling to the parent material or not. Plate obliquity works in defeating projectiles partly because it turns and deflects the projectile before it begins digging in. If there is insufficient material where the side of the nose contacts the plate, stresses will travel all the way through the plate and break out the unsupported back surface. The plate will fail instantaneously rather than gradually.

You can angle the armor any way you want, and beyond a certain point of shot overmatching plate, the obliquity will cease to be relevant. In fact, at certain conditions of shot overmatching plate, the cosine rule is broken and the plate resists less well than the simple cosine relationship would predict (LOS thickness is greater than effective thickness).

(Robert Livingston; excerpts of a response to a question posted on "Tanker's Forum")

[Kieme(ITA)]

True JonS. The theory goes only as far.

the armor there is pretty thin:

Also, a single plate that has three big openings can't guarantee that much of structural integrity. Maybe the game thinks of that plate as a weak spot, but as Vanir said we have no precise idea of this feature.

[Kauz]

Got it, it was 20 not 30, 20mm:

Even considering the extreme angle the armor there is pretty weak, for sure not the best armored part of pz4 front.

I was searching it myself....indeed the thickness is low but the angle good...

Good chart....where did you found it?

The explosion abstraction what you and Oddball were mentioning...

i mentioned it myself in my first post.

So now we more or less talk about which ballistic curve would lead us to a higher possibility to penetrate the 20 mm.

20mm ...yes....it is thin......but with an angle of 72°.

If we ignore a additional possible side-ward orientation angle to the enemy and just take for start the 72°....

You will get a geometrical armor thickness of 64,7 mm .... not possible for the 76mm even if you take the CM:BB table you would penentrate 55mm at 0° at 1500 meters.)

Just take a look at a source (http://english.battlefield.ru/specification-and-armor-penetration.html):

76mm F-34 gun:

BR-350A round 680m/sec start velocity:

@ 1500 meters:

@ 0° :

65mm (20% probability); 58mm (80% probability)

@ 30°:

52mm (20% probability); 43mm (80% probability)

You see a rapid decreasing penetration power with increasing angle.

Because: at 30° the geometric armor plus is only: +15,47%

That would lead us to the point that a round which penetrates maximum 65mm @ 0° should still penetrate 56,3 mm @ 30°, but it only penetrates 52mm.

So, from 0° to 30° we not only have to penetrate +15,47% geometrical armor .....we also see that the angle diverts the impulse of the not infinitesimale small round.

This factor is leads (like you can see) to a about 8,3 % less penetration power than it should have.

So we can assume the conclusion that the angle related penetration power is "not getting better" with further increasing the angle.

...Okay let us assume now that the round will also (only) loose 8,3% penetration power at any other higher impact angle ...which is a big conjecture in favor to the round:

20% penetration probability:

20mm = 65mm*cos(angle)*(1/1,0827)

angle= arccos (20mm*1,0827*(1/65mm))=70,54°

angle of armor is 72°; so you have about 1,5° for ballistic curve impact left.

---------

@ 80% penetration probability the difference became more crucial....not 8,3% ...now it is 16,8 % less penetration power than geometrical expected

20mm = 58mm*cos(angle)*(1/1,1681)

angle= arccos (20mm*1,1681*(1/58mm)=66,25°

angle armor is 72°; so you have about 5,75° for ballistic curve impact left.

_

About the armor quality i am not familiar.....but i guess the russian tested it at center, end or after the war with the already since 1943 existing PIVH models. So they tested it might with their better mid/end-war ammo against already "weak" german armor ...or they used their own "weak" armor-plates.

So i do not know if this counts ....

On the other side i did a lot in favor to the gun...:

1. no side-wards orientation of the tank is implemented

2. the angle dependend penetration decrease at high angles (from 0° to 70°) is assumed same like for 0°-30° (...the mentioned -8,27% (20% prob) and -16,81% (80% prob))

Conclusion:

I admit it might be possible....but only if the ballistic curve of the round is "quite" big.

To discuss further it would be necessary / interessting to know the impact angle of the round.

i try to find out or interpolate from the gun tables....but it will take time.

[Kieme(ITA)]

So, generally speaking what happened is nothing strange. Good to know.

As JonS said, we can calculate everything, fact is that 20mm armor plate with 3 openings has to deal with a projectile three times its thickness...

This is a videogame, it has some approximation we must accept when it comes to translating reality. This case is a nice example of how much you can discuss about 1 millimiter or 1 degree of angle, yet the game depicted something that is not impossible or ridicule, it's correct, so, returning to the original subject that opened this thread: nothing strange happened or "working as intended".

Glad we passed from "the best armored point of pz4" to something else.

Again thumb's up for CMRT.

[JonS]

I was searching it myself....indeed the thickness is low but the angle good

The angle is utterly irrelevant because the thickness of the plate (20mm) is thoroughly overmatched by the diameter of the projectile (76mm).

[Kauz]

So, generally speaking what happened is nothing strange. Good to know.

As JonS said, we can calculate everything, fact is that 20mm armor plate with 3 openings has to deal with a projectile three times its thickness...

This is a videogame, it has some approximation we must accept when it comes to translating reality. This case is a nice example of how much you can discuss about 1 millimiter or 1 degree of angle, yet the game depicted something that is not impossible or ridicule, it's correct, so, returning to the original subject that opened this thread: nothing strange happened or "working as intended".

Glad we passed from "the best armored point of pz4" to something else.

Again thumb's up for CMRT.

I support your saying!

Only the last sentence sounds like a "Hooah!" - mentality from BF3

[Kauz]

The angle is utterly irrelevant because the thickness of the plate (20mm) is thoroughly overmatched by the diameter of the projectile (76mm).

The angle is not "utterly irrelevant"...about the "round-diameter to armor-thickness"-effects and when they and how relevant they become i have to do some research....

I know about that issue....

But it is not a good way to just say it without any scientific numbres and this way to use it as thought-terminating cliché....

BTW.:

My first hypothesis as physicist is that the thickness relation affects mostly the chance of deflection (because of impulse and inertia matters)

The kinetic energy you need to break the bounds between atoms is always the same!!! Despite there will be some elasticity issues ....you still have to break the bounds ...and this depends on the geometrical thickness.

We talk about 70°....how far this angle is able to compensate your thickness to diameter issue is an open discussion.

[Kauz]

You have to do a LOT of research. About a LOT of things. Armour. MGs. Projectiles. Ballistics. Maths. And so on.

Currently; you are repeatedly assuming that what you're seeing is wrong.

In the future; you'd be wise to instead assume that you are wrong and what you're seeing is correct.

What a nonsense...

I just could copy your use-and senseless flaming in the same way against you....

Please search another forum for your trolling.

[c3k]

^^^

Thickness matters.

A sheet of aluminum foil is ~ .016mm thick. (Yes, 100 layers would be about 1 1/2 millimeters.) (Citation: Wikepedia "Standard household foil is typically 0.016 mm (0.63 mil) thick, and heavy duty household foil is typically 0.024 mm (0.94 mil).")

If I lay a sheet of that foil nearly flat, at an angle from the vertical of 89.99 degrees, it will have an "equivalent thickness" as a vertical piece of 91mm thickness.

Do you think that a 76mm shell fired at a flat sheet of aluminum foil 1500m away will do anything but plow through it?

Lorrin Bird (Rexford) published a book which discusses these issues, among others. The physics of penetration is more complex than running a cosine function. (Gawd, did I just write "thickness matters" and "penetration" in the same post?)

Overmatching is critical. This seems to be one such case.

Ken

[Kieme(ITA)]

I belive this thread is a good show off of how good game mechanics are and what a nice level of realism is in game. Good job also on the armor model of panzer4.

The penetration tables available around the web confirm in this case the approximation done by the game, which depicts a credible and correct result, more than enough for me.

(forgot to say: "hooah!")

[JasonC]

I would suspect a T-34/85 mid-IDed. 76mm plain AP shouldn't penetrate 80mm at 1500m. (At 500m sure, not at 1500). But 85mm could.

[Kieme(ITA)]

I would suspect a T-34/85 mid-IDed. 76mm plain AP shouldn't penetrate 80mm at 1500m. (At 500m sure, not at 1500). But 85mm could.

Jason, maybe you missed some posts, this got long soon enough. The armor in question is 20mm not 80, the Panzer4 armor front is not 80mm everywhere. I agree with you without doubds, that any reference would point to what you said, this is just a particular case because we know where the shot landed exactly.

I guess that maybe CMRT has a complex armor model that is resolved by means of "weakspots" even though the weakspot penetration is not explained or advertised to the player during the game.

[Sailor Malan2]

There is a further effect on large (relatively) projectiles hitting thin highly angled plates, especially with openings as here. The Aluminium sheet example is a perfect example of it. Penetration tables assume a fixed armour sheet able to withstand the pure 'collision'. If the bulk stiffness of the target armour is not large (compared to the energy of the incoming round) you end up with the sheet being unable to resist the pure impact force of the shell and deflecting (bending). The shell doesn't need to defeat the armour (as in, penetrate through it by a combination of shear forces and compression), it can just knock it bodily away (bending the plate as it goes). Thus the shell can defeat the plate without classically 'penetrating'. This is a large factor in overmatched plate issues - you see it a lot on WW1 battleships - the plate knocked out of place (up to say 6" inwards at one end) due to a hit on the plate join but no penetration of the plate. Still wouldn't want to be standing behind the impact!

In the case of the 20mm plate in question, the bulk stiffness will be rather low compared to the front plate (say) and may well deflect and let the round in rather than be penetrated

[cool breeze]

Kause you said "best armored and angled point of the PIV got the hit."

and

"....all what you have to know is what i told.....there are no other points which you have to know"

Another time you've been called out stating fiction as fact. With your current track record on here I suggest you start asking more questions and reducing the number of stated "facts". maybe admit to being wrong once too.

[JasonC]

Interesting. So the point of impact was actually the top plate of the lower hull section, meaning the impact was on the nearly horizontal section where it joins with the upper hull vertical? What is the full angle from the vertical of that plate? 72 degrees according to the diagram earlier in the thread.

The cosine formula puts 20mm at 72 degrees at equivalent to 64.7mm vertical. BR-350B at that range has vertical initial penetration of 69mm and complete penetration of 62mm, according to Russian sources. Perhaps surprisingly, even a 1.5 degree reduction in the angle due to fall of shot also makes an appreciable difference in this case, since by the cosine formula it reduces the resistance to 59.9mm equivalent (20mm at 70.5 degrees from vertical). The penetration figures for BR-350A at the same distance are 65mm initial and 58mm complete.

If that is the plate struck, then, I'd say the game got it right. Without the fall of shot effect, it would be in the partial penetration category; with it and assuming the better BR-350B round, it should be a full penetration. Learn something new every day...

[Kauz]

Kause you said "best armored and angled point of the PIV got the hit."

and

"....all what you have to know is what i told.....there are no other points which you have to know"

Another time you've been called out stating fiction as fact. With your current track record on here I suggest you start asking more questions and reducing the number of stated "facts". maybe admit to being wrong once too.

No way talking about "another time"....and by the way...if you could read my posts you will see that i admit that it is possible (if ignoring side orientation and further decreasing penetration effectiveness because of the big angle)

So calm down