Effective vs. Actual Thickness

[GRPitts]

An item I have long wondered about when observing individuals attempting to create a historical simulation of World War Two, is what appears to me to be a complete lack of understanding of effective vs. actual armor thickness.

If you have a metal plate 47mm thick, sloped zero degrees from the vertical it is 47mm thick at the horizontal. If you take the same plate and slope it 60 degrees from the vertical, it is 94mm thick at the horizontal.

In my experience, this is the defensive value that most seem to think the sloping of the armor provides, while in fact, they could not be more wrong. The effective thickness, in the example above, as it relates to ballistic missile protection is approximately 3.6 times the thickness if sloped at 60 degrees.

This gives the effective thickness of the armor mentioned above at some 169mm thick!

This information comes from Richard M. Ogorkiewicz, a world wide known expert on the topic. This information is found in his book, "Design and Development of Fighting Vehicles".

To boot, he states, "The exact effect of sloping armor depends on the projectile, sloped plates being more effective in the case of APDS shot than in that of full bore projectiles with caps, or with blunt noses which have been used with Russian tank guns".

Now there, IMO, is a revelation!

Attached is the graph.

[jtisdel]

I must agree - if one takes into account only armor thickness then the hours of work by munitions experts (like, say, E. E. "Doc" Smith of "Lensman" fame) to develop APCR and APDS rounds is forgotten.

The thickness (and slope which both effective thickness and "ricochet inducing") must also be balanced against the muntions. To date, I know of only two games that try to do this: Avalon Hills' Tobruk and (my favorite) Advanced Squad Leader.

Thanks for sharing the document, Greg.

[GRPitts]

You are welcome. Many years ago I began a rules set on WW2, but it simply was not my primary area of interest. I did a lot of research on weapons and armor capabilities, and had assistance from engineers who worked in the defense industry of the USA.

I knew the capabilities of weapons and armor of the period, but then I'd go play a "historical simulation" of the period and see German Pz III L/60's knocking out Soviet KV-1's at 1,000 yards! Simply did not happen.

I would love to see a decent WW2 historical simulation for miniature gaming that properly addressed weapons and armor capabilities of the period.

Thus far, I have seen none.

[jtisdel]

The ones that do a good job tend to be board games (and are a product of the 70's - Tobruk, Advanced Squad Leader, Panzer Blitz, etc). I've noticed that for most modern miniature rules the accuracy/simulation aspects are downplayed in favor of speed of play. More like Saving Private Ryan than World At War.

I've heard good things about Mein Panzer (for armor at least) but I've not played it. Flames of War is very far away from any type of accuracy (but its an enjoyable game).

[GRPitts]

I have played Mein Panzer, and agree it is the best I have seen in this respect.

[batesmotel34]

Originally Posted by jtisdel

The ones that do a good job tend to be board games (and are a product of the 70's - Tobruk, Advanced Squad Leader, Panzer Blitz, etc). I've noticed that for most modern miniature rules the accuracy/simulation aspects are downplayed in favor of speed of play. More like Saving Private Ryan than World At War.

I've heard good things about Mein Panzer (for armor at least) but I've not played it. Flames of War is very far away from any type of accuracy (but its an enjoyable game).

While Tobruk seemed very detailed and claimed to have done extensive research, the way it played ended up playing felt very much like a British apologists view of armored warfare in the dessert where the 2 lb gun was almost completely ineffective versus German armor frontally due to "face hardened" armor, while the German short 50mm did just fine against the British cruisers including the Crusader. So while they were very detailed rules, I'm not at all convinced that they got the right effects for all the detail.
(But then Tractics was the first set of WW II rules I played extensively. Talk about excessive detail with underwhelming accuracy of the results...)

At this point, when I look for a set of WW II rules, I am far more concerned with how well they represent top down elements like command and control, and the interaction between armor and infantry and artillery than with whether they get the gun versus armor interaction exactly right.

Frank Chadwick has a good essay on the Commnad Decision: Test of Battle site on how he approached the interaction of armor and guns. This is the set of WW II rules that I'm currently playing. While I certainly think there are details and issues that they don't get quite right, overall they do seem to give reasonably plausible results compared to historical accounts while also giving a playable game.

Chris

[GRPitts]

Chadwick's rules use 'actual' armor thickness to determine armor value. I do not see where he addresses 'effective' thickness in any way. Perhaps I missed it somewhere.

[batesmotel34]

I think the essay is more interesting for the general approach he took rather than the exact way he used details. You are correct that he doesn't take into effect specifically the increased effect of slope due to rounds deflecting as well as the increased amount of metal to be penetrated. He does discuss the measured penetrations as done by the British versus what it actually takes to kill a tank. Overall the approach he takes does seem to come up with numbers that give reasonable effects in the context of his rules.

Chris

[GRPitts]

I think it's the detail here that is the very foundation of the issue. Very simply put, if you do not take into account 'effective' thickness of armor, you are missing one of the most basic and fundamental aspects of tank combat.

It appears that he bases all of his weapons penetration assumptions on 'Face Hardened Armor'. While an approach, it fails to encompass correct effects of piercing caps fitted to armor-piercing shot vs. such armor.

Most armor in WW2 had a Brinell hardness of between 400 to 500. Face-hardened armor is actually in the range of 700 Brinell, and is intended to cause shot break-up. Unfortunately, face-hardened armor allows the piercing capped AP shot to attack the tank's softer armor underneath.

IMO, he would have been much more in the ball park had he used a typical representation of the 400-500 Brinell rather than the occassional face-hardened armor used in the field.

[batesmotel34]

Originally Posted by GRPitts

I think it's the detail here that is the very foundation of the issue. Very simply put, if you do not take into account 'effective' thickness of armor, you are missing one of the most basic and fundamental aspects of tank combat.

It appears that he bases all of his weapons penetration assumptions on 'Face Hardened Armor'. While an approach, it fails to encompass correct effects of piercing caps fitted to armor-piercing shot vs. such armor.

Most armor in WW2 had a Brinell hardness of between 400 to 500. Face-hardened armor is actually in the range of 700 Brinell, and is intended to cause shot break-up. Unfortunately, face-hardened armor allows the piercing capped AP shot to attack the tank's softer armor underneath.

IMO, he would have been much more in the ball park had he used a typical representation of the 400-500 Brinell rather than the occassional face-hardened armor used in the field.

If I was playing a game where it was my tank versus your tank, like some PC games have been, then I would be concerned about the importance of this level of detail for a set of rules. I would consider it more important in a naval game where the ofrces involved are a few capitaql ships are present on each side. (Of course then you need to worry about angle of impact as wel.) For any land game which involves forces at a higher level than that, even if it is only a platoon or two on a side, I believe that taking all the exact details of armor penetration into consideration in coming up with a formula for armor would be wasted effort. There are far more important aspects to simulate/represent than the exact effect of sloping on armor. I agree that I don't want to play a game where a German 37mm gun can easily knock out a KV at 1000 yards, but I'm also not incredibly concerned if the rules give the 37mm gun a slight chance to knock out a KV at 30 yards vs 50 yards or maybe even 100. The way Frank approached armor for CD4 seems to fall within what seems to give reasonable effects on the table top. (One of the aspects of CD4 I'm not entirely happy with is how he handles range categories uniformly for all weapons and especially when combined with the ammo depletion rules how it tends to prevent weapons like the 88mm Flak from having anything like the long range effectiveness they had a reputation for historically.

As a counterexample, while Tobruk claimed to take all the details of armor penetration and armor quality into account, it never did play very well as a game or as a simulation of anything more than a few tanks on one side versus the same on the other.

Ogorkiewicz is a very interesting read on AFV Design (although severely dated considering modern technology) but it would never be my starting point for writing a set of tactical WW II land rules.

While I agree that the interaction of armor and armor piercing rounds can be a fascinating subject, it doesn't make an interesting game. Reperesenting the interactions between the humans on both sides is generally far more interesting game wise.

Chris

[GRPitts]

And there you have it. What you are looking for in WW2 rules and what I am looking for are two different things.

That's why they make chocolate and vanilla!

[batesmotel34]

An interesting site I found has a simulator for gun penetrations versus armor for WW II German/US/UK equipment. Serendipitously found it mentioned in the CDTOB forums.

Chris

[GRPitts]

I've seen that before. I found one I thought was better once but seem to have lost the link. If I can find it again I'll post it.

[Mercedes1254]

I just joined this site, but I find your thread very interesting because we are in the process of developing just such a rule set right now. It will take into full account the armour type, metalurgy and slope, as well as the type of munition being fired. The project is about half complete at this time but will include almost all WWII vehicles , infantry, artillery and air assets when complete.

[GRPitts]

Welcome to the site James!

The design concept on your rules sounds very interesting and I hope you will share more with us as we go along.

One thing I have never been able to find are statistics that show a standard ammunition compliment for the various tanks of various nationalities in WW2. I'm sure this would vary depending on a number of logistical factors but to have what was the standard, desired, or normal compliment of each type of shell (HE, AP, APDS, so on & so forth) would really answer a lot of questions.