Overmatching, why some tanks sloped armor just didnt work

I disagree the angle of attack from low vel round makes alot of sense

 

Or, Kelly, by using mortar rounds. High trajectory and a low velocity which fits your calculations perfectly.

I agree Fivetide. In simple terms (for I am a simple person...no comments ) the more force you can put into a thinner thing the more chance of penetration.

I have drawn up something to help explain. Will edit this when I upload it.



Number one is a shell that is perpendicular to the armour at the time of impact. the horizontal distance (the funky thing under the armour line) is exactly 5 pixels wide.

Number Two is the same situation (ie, identical velocity) except the angle on impact is now 45 degrees. the horizontal distance is 6 pixels.

If you want I can e-mail you the image itself.

Basically, the total distance the shell has to penetrate is in a straight line through the armour, thus the highest potential for a 'sucessful' hit with penetration will only occure whe the AoI is exactly 90 degree to the slop of the armour. I have no idea who this helps more.....whatever.

 

If we are talking about artillery and mortars, I completely agree with his statement. However if we are referring to tank shells at regular combat ranges, then the statement is incorrect. Arty shells could neglect the angle of armor, but they are shot from a long ways away, and mortars are simply fired at high angles.

Again, I am working on digging up info, but trust me when I say shells don't change angle that much. The German Mark 4 series with the short barrel 75 L/24 only dropped 5 degrees at 2000 meters, and considering the dispersion on that gun, chances are it wouldn't hit anything anyways. Considering this gun was one of the lower velocity guns of WWII, you can bet the shells don't angle a lot. Yes, shells can drop several feet over over a few hundred feet, but they don't re angle themselves.

 

Actually the States test fired the first aimed artillery shell a while ago...same tech can and probably will be applied to future tank ammunition.

But that's beside the point isn't it?

 

Okay someone on the WWIIOL forums was nice enough to post this.


I have no interest in doing those calculations, but a general rule of thumb is that what ever angle the gun is elevated at, that is the angle the shell will hit the ground at.

If you look at the 6 pounder, its barrel was only raised 5 degrees to go 3000ms. To neglect an angle of 30 degrees means you would have to raise the barrel 30 degrees or so for the shell to come in at that angle.

 

... provided both tanks were on a perfectly flat surface.

Although unless the terrain was very disturbed it would not make much of a difference.

 

THough we will never know I wonder what the percentage of "first hits", actually knocked out a MBT. I can understand the first tank to be targeted say in a ambush to be high, but during a large Tank battle ?

 

True, but 3000m was a pretty impractical range to shoot at an enemy. Probably the best thing is just to figure that unless on a hill, there is little chance of sloped armor being neglected bu the way a shell falls.

 

How is this slope multiplier found? if I use pure geometry the equivalent of 45mm at 60° (30°from horizontal) is 90mm:

http://www.panzerworld.net/armourcalculator.html

Regards.

 

I noticed, regarding the armor improvement in the M4A3 series in 1943, the change in the front hull of earlier marks with a thicker but less sloped plate the armor quality is given as the reason for the improvement in protection. This doesn't recognize the major improvement in design.
Armor quality of the earlier M4, M4A1, M4A2 may not have been as bad as has been suggested. The M4A3 front hull armor revision reduced the vulnerability of the front plate by eliminating the near vertical armor over the bow machine gunner and driver positions. Only the hull MG remained a weak point and the transmission armor remained unchanged. Considering how much of the area of the front glacis of the basic M4 design was near vertical the change in design of the M4A3 should have improved the tanks protection alone.

 

The thread being from November of 2006, and the last post being from April of 2019, I am hesitant to post this reply. However...

The increase in protection with regards to the glacis plate of the M4 comes from more than the reshaping and thickening of the plate. Although those factors were quite major, it should also be noted that the early production layout of the glacis was quite the mess. In addition to having the two protrusions to house the hatches and vision ports, the armor was further weakened by being constituted of five plates rather than a single, uniform sheet.

Improvements to the tank gradually saw the elimination of the aforementioned bulges, the thickening of the armor, and the introduction of a single uniform plate. It's difficult to put an exact value on how much this actually helped, but from a metallurgical standpoint, the difference must have been quite pronounced.

All of that having been said, it's curious that in one of the tank historian's bibles (WWII ballistics: Armor and Gunnery by Bird and Livingston) it's said that the late Sherman glacis was actually worse. By the calculations presented in said book, the early style hull offered an effective 123-mm of resistance vs. 75-mm projectiles. The later hull offered a mere 118-mm resistance.

While this has little to do with the original post of this thread, I hope this clears up any questions about the Sherman's armor plate.

 

This forum is a gold mine

Another important effect is the normalization/de-nomarlization. A short, sharp nosed shell hitting sloped armor tends to deviate from the perpendicular angle to the armor thus increasing the efficacy of the latter. Instead a long, blunt nosed shell will angle towards the normal, thus shortening the path and easing penetration. Length of shell seems very important, thus the short shells used in WW2 tended to get de-normalized and make sloped armor effective. APCR and early APDS were less effective against strongly sloped armor than "regular" shells. If the core of the APCR was blunted then the de-normalization effect was reduced. As I understand it normalization/de-normalization is independent from the overmatching effect discussed above, thus it should be considered independently. However the small diameter of de-calibrated shots makes overmatching less likely to occur, because their diameter would be less than the thickness of many armor plates used by the opponent. In this site from WarThunder Wiki you can find these effects explained, the people writing there seem competent, do you guys think it is a legit source?
Damage mechanics - War Thunder Wiki
I also found a calculator of WW2 guns vs armor:
WWII Gun vrs Armour Calculator

Regarding Sherman armor, Wikipedia says: A Waffenamt-Pruefwesen 1 report estimated that with the M4 angled 30 degrees sidewards, the Sherman's glacis plate was invulnerable to shots from the Tiger's 8.8 cm KwK 36 L/56 and that the Panther, with its 7.5 cm KwK 42 L/70, would have to close in to 100 meters (110 yd) to achieve a penetration in the same situation.
The armor was vulnerable at lesser angles however. Wikipedia says: other German documents suggested that the glacis of a Sherman could be penetrated at a range of 800m by the Tiger I. I think this refers to hits from the front close to the normal on the azimuth plane. That is, if the gun fired from a position directly in front of the Sherman the glacis was vulnerable at least from medium distances. What do you guys think?

 

From Ostfront details I know the 88 mm was effective against the T-34 From a distance of 1400 meters alone. The T-34 had no chance. They were shot dead from a distance they could not fire any good shots.

 

Thank you - If I'm honest I didn't realise that it was still 'live' - my understanding was that it had been archived. I'm delighted to find it up and running again

 

I recall reading from the Ostfront battles that the Panther frontal armour at least was clearly more brittle since Germans did not have any more enough minerals that hardened the armour steel as well from ca 1944. The armour might not be pierced the first time but shattered the sloped armour and the next round would penetrate it. Only read this about Panthers but might be the same for other German tanks.

 

Maganese is needed for the steel to be tough (as opposed to hard). The Soviets lost their access to it when the Germans overran their mines. The T-34's armor could be hard, but that made it brittle (hence tough is better). This resulted in non-penetration hits that resulted in spalling with bad results for the crew members. The same may be said of the late war German Panther.

BTW, I read in Mortar Gunner on the Eastern Front how a 150 mm infantry howitzer shelled and destroyed a KV-1. Top armor tends to be thin.

 

As I understand it, it's not so much the angle or the thickness as much as the projectile's momentum once it touches the armor, versus the armor's compressive strength. So you have to assume the weight and velocity of the shell, and assume it is strong enough to retain much of its weight once it hits. In addition to this, the toughness (ability to resist deformation) of the armor and its weight.

 

I think they all add to the end result if I understood properly all you mentioned. Rommel had PAK front where he lured the enemy tanks deep enough for the AA 88's to do their job. Simple but worked well.