Ramble on tanks, armor and other stuff...

LemoN said:

Btw, lack of consistency in terms of hardness doesn't say anything about the quality of the plates themselves. So that's another factor that comes into play.

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No - but it does have implications on quality control being very poor, which makes the quality of the plate pretty suspect too, as it suggests that the steel was poorly made and, potentially, shortcuts taken on plate rolling and who knows what else. But conjecture is always fun!

That Kummersdorf set of reports would be useful material...

Edit: yes, it was a Poldi test, which is why they give a range of results in their tests on the plate. They were aware of the inaccuracy, so giae a spread of results.

LemoN said:

Actually, the maths behind it is both simple and complex. It's "rather easy" to implement a basic penetration system that'll generally do well at calculating theoretical numbers. Where the system itself get's complex is the point when you start implementing things like variations in the armour and round quality, shattering, spalling, APHE bursting charges, effect of different angles and hardnesses of armour and it's effect on different rounds etc.

Look here for an easy to use calculator that needs only a few inputs on the geometry, hardness and density of the penetrator and the same for the armour.
[url]http://www.longrods.ch/[/URL]

The real problem is the difference in data available to feed into the system. For instance, every major nation used different quality ammunition for their penetration tests, had different criteria as to what a successful penetration actually is, used different hardness targets, different target angles, etc.

Now all this theoretical data has to be analysed and "evened" in order to get somewhat accurate results. And this was done the combat accounts start rolling in. And then you find a test that will throw over half of the other tests you based your data on. Alan's job definitely isn't easy.


tl;dr version: All Data has to be "evened" out and interpreted, resulting in EVERY penetration system with real world data being different and possibly being incorrect. The only way to make the system more realistic is by matching the results of your system to other systems and RL tests and then adjusting the data accordingly.

If your system says that a tank can't be penetrated by a specific round at a very low distance while another system says that it can be penetrated at over 9 miles, there's something wrong with either one or both of the systems or the data that was fed into them.

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Now, to be completely fair - a very well reasoned and sensible post, Lemon

I guessed the link was Willi Odermatt - I am SO looking forward to the day when we do modern tank combat! The amount of research post-WWII is HUGE in comparison to pre-1945. People forget that most of the armor penetration mechanisms active during the war years were just about obsolete at the end of the war, as all sides were shifting to APCR/HVAP/APDS - particularly APDS, which went on to become APFSDS and gave us all the modern long-rod penetrators (see Odermatt...).

Correct: "normalising" what data you can find is a ***** - see the debates above as just one example. The different measurement techniques don't help. And all the variables when you take that to the battlefield.

On top of that, everyone makes one key mistake: they assume the numbers are "absolute". A penetration figure given on a German datenblatt of 93mm at 1000m/30 degrees - what exactly does that actually MEAN?

The Germans did their measurements by firing at a test plate, lowering the muzzle velocity until they JUST got 5 rounds in a row to penetrate, giving them a "limit velocity". One single number. From that one single number, they would then interpolate, using their own tables (which disagree, for example, with US equivalents on slope effects) what the "penetration" would be at certain ranges/angles. In game, there are a number of possible results for an impact, based off a probablistic bell curve:

• Off the bottom end of the curve - below the 1st percentile - guaranteed failure.
• Off the top end (over about 98th percentile) - guaranteed penetration
• In between - generates a probability off that bell curve... random chance against that probability number

I hear some people say "but that is a problem for competitive play - it isn't KNOWN". Well - tough. That is a good model of the real world - and, if you know what you are doing, you'll be making shots at the top end of that curve, quite deliberately. But there will be plenty of shots where you have "a chance" of succeeding - your call - take the shot, or don't! That is what they had to do on the battlefield. 75mm Pzgr.39, good flank shot on a T-34, 600m - you're going to penetrate, so pick your spot for maximum damage. Other shots - harder

But Lemon is right - getting what data there is into line and then into the game is hard. The math, given all the variables, is evil. Then compare against the real world... adjust until it "feels" right in as many situations as possible. Oh - then wait for the modders to change it all around

Shockingly, we're agreeing

I read that the "hotter" ammo was causing the casing to expand just that tiny bit too much and the extractor couldn't cope, leaving the empty casing stuck in the breech. Which would be a complete bugger in a combat situation - loader desperately scrabbling at the end of the casing!

LemoN said:

Not on the distance the PzGr. 39 should be able to take out the T-34's glacis.

Overall, Bird&Livingston present some really good reasoning (and have done extensive research on the subject we're discussing here), although their results seem to be a bit "extreme".

Have you seen the early 1942 statistics of T-34's taken out by different calibres?
Get's to show that the KwK 39 was surprisingly effective (and also that it was the most common German gun at that time).

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I like stats - show me the stats!