HE vs Armor

[Guest JonS]

Unfortunately, CrapGame, you've made a fundamental - though understandable - error in your analysis. When a shell casing breaks up into fragments it undergoes brittle fracture (I think the metallurgists load up the mix with carbon to make the steel brittle) which causes it to break into flakes.

It does NOT break up in the same way as a plate when you drop it on the floor(or, at least is not meant to - poor quality control can screw this up). What I mean by this is that each fragment doesn't have sections of both the inner and the outer surface. If this does happen it is considered a poor shell. A few years ago we had a batch of rounds from Singapore that showed this characteristic, and we've since stopped sourcing from there.

When BH said that the fragments from different shells were the same size and weight he was correct. Larger shells have a larger lethal radius because they start out with a greated total number of fragments, so a greater distance from the detonation point is required before the density of fragments per unit area of air (yes, I mean area, not volume. Think of the expanding envelope surface of the explosion - this is an area) falls below what is considered 'lethal' or 'likely to cause wounds'.

Regards

Jon

------------------

Ubique

[This message has been edited by JonS (edited 01-20-2000).]

[CrapGame]

JonS,

I agree totally with your analysis, however, in the context of BH's argument, he was postulating that the, "...88 isn't going to produce very many more fragments than the 75." He then states, "Assuming, however, that both shells make fragments about the same size, then there shouldn't really be much difference in effect between the two. First off, both shells will make very nearly the same number of fragments, and all fragments will be approximately the same mass."

Now we both know that the laws of physics state that one of these statements must be false as the shells are physically different in size by a substantial margin. I believe someone states roughly 60%.

Thus, if he is stating similar #'s of fragments, then the mass of the fragments must differ. If the fragments are uniform in size, as you and I believe, then the 88 must have substantially more fragments than the 75, as the shells are 60% different in size. This results in its greater effect as a fragmentation weapon.

There can be only one....

CrapGame out...

[This message has been edited by CrapGame (edited 01-20-2000).]

[Guest JonS]

Ok, I've just done some quick calulations to see how much more metal there is in an 88mm as opposed to a 75mm shell case.

Assumptions: ignorned both the base and the nose cone (these tend not to fragment very well anyway)

Both shells 30cm long

Both wall thicknesses 2cm.

Results: the 88mm will produce approx 20% more fragments than the 75mm.

My interpretation: Well, this is much less than the 60% figured that has been bandied about here willy nilly. I realise that there are some significant assumptions in the above calcs (esp using uniform wall thickness), son would put a margin of error of +-10% on the calcs. At the extremes this would put the figure at 45% more fragments from the 88mm - still much less than the 60% figure quoted.

Regards

Jon

------------------

Ubique

[Lee]

Charles, speak on this issue. We must know!

[Bullethead]

Crapgame said:

<BLOCKQUOTE>quote:</font><HR>As the 88mm shell has roughly 60% more internal volume than a 75mm shell one can extrapolate a little less than 60% (not the full 60% due to thicker walls of the shell) more HE is sitting in the cavity of the 88mm than in the cavity of the 75mm.<HR></BLOCKQUOTE>

Based solely on external dimensions, the 88mm HE shell has 57% more volume than the 75mm HE. However, in addition to the slightly thicker walls of the shell, the 88's fuse also takes up a larger proportion of the internal volume than does that of the 75. So, without having some internal drawings handy, I'd have to say that the 88 had no more than about 50% more explosive volume than the 75, at most. Maybe a bit less.

So what? That's not going to make the fragments fly faster. And that's what's important in the question of destroying halftracks with near miss HE shells.

<BLOCKQUOTE>quote:</font><HR>You said: "So where the difference between shell diameters is small, such as the 15% difference between the 75 and 88, most if not all of the theoretical advantages of having the larger shell wash out." - Definitely not true. You are combining several partial truths to make a bigger generalization that is less than true.<HR></BLOCKQUOTE>

Can you back up this assertion? I'd love to see some detailed numbers proving how the 88 HE was so much more devasting than the 75 HE vs. halftracks. That's my whole question here. Everything else I've said has just been bringing up factors to consider, trying to get BTS to examine this issue more closely. Because for the 75 HE to have NO EFFECT AT ALL while the 88 ALWAYS kills seems a bit of an extreme difference to me.

If that's realistic, then fine. I just want it proven so to my satisfaction. You gotta admit it seems odd on the surface. I just can't imagine anybody building an AFV that couldn't keep out fragments from light shells such as the 88, especially given the knowledge that such fragments are extremely common in the situations in which the AFV would be employed, from light arty and medium mortars. Given that such fragments cause the vast majority of battlefield casualties, and that the whole point of an APC is to deliver the troops safely to the enemy position through such fire, why build an expensive AFV that confers no defensive benefits to troops?

Also, IMHO a rifle bullet is WAY harder to stop than a small shell fragment of the same mass. The bullet is going much faster, it hits with all its energy concentrated on 1 point whereas the fragment often hits sideways, and the bullet often has a penetrator tip that the fragment lacks. If the halftrack can keep out bullets, why do shell fragments kill it. And more importantly, why do only SOME fragments kill it while others, of approximately the same energy, have no effect?

<BLOCKQUOTE>quote:</font><HR>"...so the 88 isn't going to produce very many more fragments than the 75." - definitely Not True. If the Volume of the 88mm is 60% larger than the 75mm, then there must be a mathematical relationship to the surface area as well.<HR></BLOCKQUOTE>

This doesn't really matter. For both shells hitting the ground in the same relation to the halftrack, only fragments coming out of the burst that hit the armor fairly close to plate normal will have a chance of penetrating. All the other fragments will either miss or glance off. Because all the fragments from both shells have approximately the same mass and velocity, then they should all have the same chance of penetrating.

The only difference is that the 88 will have a few more fragments. The significant dimensional difference is shell length, because of the narrow arc in which fragments have a chance of penetrating. Most pieces from further around the 88's wider curve will be outside the lethal arc. Because the 88 shell was only about 15% longer than the 75mm shell, you're talking on the order of no more than 15% fragments in the lethal area. Thus, most of the 88's larger surface area is irrelevant in this situation. And even if every potentially penetrating fragment of both shells penetrated, what difference would that make? You're still talking a relatively narrow section of the target taking the damage. The guys behind the armor there are casualties either way (or should be, IMHO), whether they have 1 hole in them or 2. Same with the HT's motor.

Thus, it seems to me that the larger number of 88 fragments is mostly irrelevant.

<BLOCKQUOTE>quote:</font><HR>"The only way it could do so is if each fragment was much smaller than those of the 75, which would make them LESS effective vs. an AFV." - Here you are ignoring your previous statement that the walls of the larger 88mm shell must be thicker than that of the 75mm.<HR></BLOCKQUOTE>

No, what I meant was that in this hypothetical case, each fragment of the 88 shell would use up much less external surface area, regardless of thickness of shell wall. Picture the 75 making essentially cubical chunks compared to the 88 making slivers like stacked razor blades. But I don't think this is the case anyway.

<BLOCKQUOTE>quote:</font><HR>You said: "Thus, fragments from either shell will hit the halftrack with very nearly the same energy..." - not true due to differences in fragment mass pointed out above<HR></BLOCKQUOTE>

KE is (mv^2)/2. The significant number, therefore, is velocity. This is the essentially the same for both sets of fragments. Differences in mass have very little effect on KE, especially when the difference in mass is small. So sure, on the average, an 88's fragments were an RCH heavier, so thus had an RCH more KE. Is this enough difference to have them kill the halftrack while the 75's fragments hardly scratch the paint? I seriously doubt it.

<BLOCKQUOTE>quote:</font><HR>"...and thus will have equal chances of penetrating. And because the number of fragments are nearly the same," - again, not true due to the 88mm shell being substantially larger<HR></BLOCKQUOTE>

You miss the point. KE (and impact angle, etc) is what matters for penetration. KE is essentially the same for both sets of fragments. It doesn't matter how much bigger the 88 was compared to the 75, it didn't make fragments with significantly more KE. True, it put out more fragments because it was a bigger shell, but most of these were outside the lethal area. Therefore, the 88 shouldn't ALWAYS kill halftracks that the 75 NEVER does, IMHO.

<BLOCKQUOTE>quote:</font><HR>"...the total amount of damage done should be very nearly the same." - WHEW!!!! As you know, this is completely false. Many partial truths and generalizations can no be lumped together and presented as fact.<HR></BLOCKQUOTE>

We're talking about the same, relatively small part of the halftrack for both shells. In this area, the 88 will strike with a maximum of maybe 15% more fragments than the 75. But all of these fragments will have essentially the same KE due to very nearly the same velocity and very nearly the same mass. So if 1 set can penetrate, so can the other, and if 1 set can't penetrate, neither should the other. The results should be about the same in either case.

-Bullethead

[CrapGame]

Ok, let's look at it this way.

JonS, I don't think that your assumptions are correct. I don't know for sure (for some strange reason, the government has never let me get my hands on 88mm and 75mm shells down at the Sports Authority ), but I don't think the length of the 88 and the 75 shells are the same. Bullethead states above that he calculated the difference in shell volumes based on external shell size alone to be 57%. I would think he has to know the external dimensions of both shells to calculate this. (Theoretically, I guess we could back into them mathematically, but unfortunately, I was not really paying much attention in that Calculus class ) His number is supported by the rough 60% number mentioned above by someone else. Therefore, I believe that BH's calculation is much closer to actuality than your 15% initial calc.

Bullethead, you have to let us know how to do that neat quoting thing. I have searched for it, and still can't figure out how to do it. Anyway, I must reply to your statement. I will agree to your 57% internal volume difference based on shells with identical wall thicknesses. How much thicker are the walls of the 88mm than the 75mm? I don't know, but I do not doubt your assumption that the thicker walls and larger overall fuse size reduce the volume difference between the two shells to 50%.

I never stated anything about the speed of fragments. I stated the assumption that the explosive used in the two shells was the same, thereby causing all fragments to travel at the same speed. That is why I was concentrating on the difference in size or quantity of the fragments between the shells, as fragment speed had already been eliminated as a variable in the equation.

I have no detailed numbers that support my assertion that most of the theoretical differences between the 75mm and 88mm shell wash out- You know that is impossible to have, especially since my local Wal-Mart stopped stocking 88mm shells as too many people were using them for deer season. However, I have not had any experience with the 75mm HE having no effect on a halftrack. This actually sounds quite preposterous to me. (I have had good luck with fragments from 60mm mortars causing havoc with the halftracks, though )

I agree with your bullet having greater penetrating ability than a fragment travelling at the same speed argument. It makes sense to me. I can only guess that some fragments kill while others don't due to what they hit - ie some might hit a critical function, while some might pass through the side and right out the other or the top. I really don't know. It does seem that luck must play some role in this.

You state: "For both shells hitting the ground in the same relation to the halftrack, only fragments coming out of the burst that hit the armor fairly close to plate normal will have a chance of penetrating."

OK, I will agree that this assumption is true.

Then you state: "...you're talking on the order of no more than 15% fragments in the lethal area."

OK, I will agree with this assumption as well.

Then you state: "And even if every potentially penetrating fragment of both shells penetrated, what difference would that make? You're still talking a relatively narrow section of the target taking the damage."

This is where I disagree. Having never been subject to an artillery barrage (other than the wife throwing frying pans and the like at me), I tend to believe that 15% greater fragmentation has to be quite a difference. However, I do not think that the apparent greater lethality is due entirely to the fragmentation effect alone. There must be some consideration given to the 50% larger HE charge of the 88mm causing higher casualties and vehicle damage due to the effects of the larger shockwave and concussion of the shell, and increased spalling, etc. This can not have no relation to the level of damage to vehicles and personnel caused by the difference in blast between the two shells.

I guess I am arguing these points because I have not run into the problem of 75mm HE not having any effect on halftracks. Which scenario has this confrontation? No scenario in the demo has Shermans versus halftracks.... So are you a Beta Tester???

CrapGame out...

(of breath)

[dalem]

folks-

I've never been a cannon-cocker or rifle-locker or under a barrage, but I guess I'm thinking more along the lines of the guys actually *IN* the halftrack than the shrapnel that may or may not be riddling it with holes. There are other HE effects like blast and shock (same thing?) that come into play, right? And even with my little pinheaded noggin below the lip of the armor and plugs in my ears, wouldn't these "other effects" do something to me?

And I don't imagine that a violently shaking HT can be much good for me if it say, breaks my wrist.

I guess that maybe I'm abstracting too much for the tastes of some folk, but I'm okay with a slightly bigger shell doing more damage to a thinly-armored box. If it's on the screen as a flaming wreck with 10 KIA when in real life it was really just a spine-breaking shake-em-up with 5 guys "out of it" and the other 5 "carrying them to the rear", well, that's fine with me.

I understand that one of the original points was "was the 88 HE THAT much more effective than the 75"? and that my little blurb above doesn't really address that. But since I don't want to experience the real thing, I'll trust BTS's research and execution. I've enjoyed the hell out of it so far. And I've enjoyed this thread so far as well.

If battlefield conditions were easy to model perfectly, they wouldn't be so fascinating to read about.

-dale

[Bullethead]

<BLOCKQUOTE>quote:</font><HR>Bullethead, you have to let us know how to do that neat quoting thing.<HR></BLOCKQUOTE>

It's in the UBB Faq link. You put the word "quote" within square brackets adjacent to the front of the text and "/quote" in square brackets at the end (only without the quote marks )

<BLOCKQUOTE>quote:</font><HR>I never stated anything about the speed of fragments. I stated the assumption that the explosive used in the two shells was the same, thereby causing all fragments to travel at the same speed. That is why I was concentrating on the difference in size or quantity of the fragments between the shells, as fragment speed had already been eliminated as a variable in the equation.<HR></BLOCKQUOTE>

Sure. But like JonS says, all fragments from all shells designed for the same purpose are intended to be about the same size, and the metalurgy of the shell casing helps achieve this. Of course, in practice you get all sorts of irregular shapes and sizes even from properly made shells. So some of the 75's fragments will be bigger than some from the 88. However, if you collected and weighed all the fragments from both, you'd get very close to the same average mass per fragment for both shells. Maybe the 88's would be an RCH heavier on average, but this difference wouldn't be significant.

<BLOCKQUOTE>quote:</font><HR>However, I have not had any experience with the 75mm HE having no effect on a halftrack. This actually sounds quite preposterous to me. (I have had good luck with fragments from 60mm mortars causing havoc with the halftracks, though )<HR></BLOCKQUOTE>

The way I got the halftrack targets was experiementing in the LD scenario. I had the Tiger and StuGs shoot at the German halftracks. The only way to get this to happen is to issue area fire main gun orders with the target point right under the halftrack. Try this yourself sometime .

In this experiment, the 88 ALWAYS "knocked out" the track with a single shot and often killed the majority of people in it. OTOH, the 75 usually had no effect at all--after several shots, it would "immobilize" the track in a "crater," and I think the immobilization was from the appearance of the crater, not from damage to the track. In any case, only very rarely did a 75 shell hurt anybody inside.

The differences in effect in this experiment, and also the differences between other weapons such as the 60mm mortar, are what led me to start posting all this blather.

Something seems wrong to me here:

1. 60mm mortar HE near misses often take out halftracks and some occupants.

2. 75mm HE near misses hardly ever hurt halftracks or occupants at all.

3. 88mm HE near misses always kill the track and many of its occupants.

There are 2 ways of looking at this. Either the 60mm and 88mm are right and the 75mm is getting the shaft, or the 75mm is correct and the 60mm and 88mm are way too powerful.

For reasons previously stated at great length, I favor the latter view. Fragments from 75s and 88s are essentially identical from the halftrack's POV. Because the main purpose of halftracks is to prevent troops from getting hurt by such fragments, it seems logical to me that only rarely should an HE near miss by either shell do any damage to the track or its occupants. This is especially the case when the halftrack does a pretty good job of keeping out rifle-caliber bullets, which IMHO are harder to defend against. And 60mm mortar shells should have even less chance of hurting an AFV than the 75 or 88 shell, because not only is the 60mm proportionally smaller, but it also has very thin walls due to its very low velocity. Thus, its fragments would be smaller on average and have less chance of penetrating.

<BLOCKQUOTE>quote:</font><HR>"And even if every potentially penetrating fragment of both shells penetrated, what difference would that make?

This is where I disagree...Having never been subject to an artillery barrage (other than the wife throwing frying pans and the like at me), I tend to believe that 15% greater fragmentation has to be quite a difference.<HR></BLOCKQUOTE>

Picture an area a few feet wide on the side of the track. Picture say 2 grunts sitting on the other side of this area. Picture say 30 75mm fragments scattered evenly over this area and all penetrating (which I think highly unlikely, as noted above, anyway). The 2 guys on the other side are Swiss cheese. Now picture the results of adding 15% more fragments, for a total of 34 holes. The guys are still just as dead.

Conversely, if, as I believe, neither set of fragments should be able to penetrate (at least not very often), the 75 gives you 30 paint scratches, the 88 gives you 34.

In both cases, the effect on the target is the same.

<BLOCKQUOTE>quote:</font><HR>However, I do not think that the apparent greater lethality is due entirely to the fragmentation effect alone. There must be some consideration given to the 50% larger HE charge of the 88mm causing higher casualties and vehicle damage due to the effects of the larger shockwave and concussion of the shell, and increased spalling, etc.<HR></BLOCKQUOTE>

The side of the halftrack is going to protect the troops from the shock effects of the blast, at least enough to keep them in fighting trim although their ears might be ringing (see long thread on muzzle blast from last month). Because even medium arty shellbursts have little blast effect on prone troops a few meters away (in terms of incapacitating casualty effects), I figure the halftrack's side would afford adequate protection from the blast of smaller things like 88s at similar distances. Thus, the 88's larger explosive content would make no difference to the occupants from a blast standpoint, IMHO. And because the explosion is happening some distance from the track instead of right against the armor, I don't see its force being concentrated enough to spall armor.

However, mechanical damage to the halftrack is perhaps another story. The main thing I see is shredding the track assemblies and tires. These weren't armored so the "limited penetration zone" referred to above for personnel casualties doesn't apply. So in this case, the larger 88's greater number of fragments would make a bigger difference. Thus, it would be reasonable to give the 88 a somewhat higher chance than the 75 of immobilizing the halftrack.

I don't see any addition mechanical damage from blast alone, however. While mines can screw up transmissions from shock (besides removing wheels/tracks), it's my understanding that this requires the explosion to be transmitted directly through the drivetrain components from actually hitting a mine--blast from a similarly sized (or probably smaller) 88 shellburst some distance away wouldn't do it.

Also, while sufficient blast can tip over vehicles, I don't think the 88 had the macho to do it. This comes from observations at arty direct firing ranges. A very near 155mm HE miss can make a 6x6 truck hulk turn a flip in the air, but I've never seen one do more than shake a much heavier APC hulk. If the 155 couldn't do it, then I doubt the 88 could.

-Bullethead

[Doug Beman]

Lemme try:

<BLOCKQUOTE>quote:</font><HR>I had the Tiger and StuGs shoot at the German halftracks. The only way to get this to happen is to issue area fire main gun orders with the target point right under the halftrack. Try this yourself sometime <HR></BLOCKQUOTE>

I don't think is a very productive battle tactic,BH:

"Uh, Herr Feldwebel, der Tiger ist stoppingk right next to uns. Und now he's turningk his turret....Oh, scheiss!"

DjB

[Lee]

Charles, be merciful, please explain these extreme

differences in performance between the 75mm and 88mm

HE shells in CM. The pain of not knowing is unbearable.

[Guest Big Time Software]

Well, I tried to reproduce BH's situation with the current build, but it was NOT possible because the TacAI has changed a lot.

1. Tank area fire (main gun) will cease if there are friendlies in plain view that can be harmed. So a could not fire at 251/1 HTs with German tanks.

2. Trying to shoot at M3 HTs didn't work out because their armor is less thick and not sloped. Two out of four were KO'd by MG fire, the other two drove out of the HE killing area.

The *only* thing I can say here is that the two HTs were killed by one Tiger and one StuG. The remaining two HTs managed to escape one Tiger and one StuG without damage. So at the very least, BH's assumptions about Tigers scoring 100% kills is not supported by my quick test.

As I said, a lot has changed since the demo and "scientific" tests without an editor (and even WITH one) are very hard to do. So since this whole discussion is based on assumptions coming out of the Beta Demo I say that this isn't worth bothering with any more until after the final comes out

Steve

[Colin]

Wow! Steve's online right as I'm typing this. It's almost magical isn't it?

------------------

Visit my Combat Mission for Mac page! A;; of CCJ's tweaked graphics for Mac!

cm4mac.tripod.com

[This message has been edited by Colin (edited 01-21-2000).]

[Bullethead]

<BLOCKQUOTE>quote:</font><HR>As I said, a lot has changed since the demo and "scientific" tests without an editor (and even WITH one) are very hard to do. So since this whole discussion is based on assumptions coming out of the Beta Demo I say that this isn't worth bothering with any more until after the final comes out<HR></BLOCKQUOTE>

OK, thanks for taking the time to look at it . I'll take another good look myself once I get the game.

Oh no, what if Steve decides to sit on the game rather than have me bring this up after it's releases?

-Bullethead

[Lee]

Darn, I was looking forward to those test results.

Oh well, after the game goes gold you guys can run

some tests on this I guess (maybe Charles can disable the

tacAI so it won't mess up the experiment next time ).

This whole monster thread has got me *really* curious about

this issue. And while I tend to doubt Charles would make

a mistake in the math behind the modeling of these shells,

the results seen seem so odd that one almost has to conclude

that something is amiss. I just wouldn't want CM to

ship with significantly inaccurate HE shell performance.

Someone make note, we have to get back to this issue

after CM goes gold. Until then, the mystery lives on.

[This message has been edited by Lee (edited 01-21-2000).]

[Guest John Pender]

A very interesting and well debated thread gentlemen.

I have little technical knowledge to add but it seem odd to me that HE fragments would so easily penetrate the side armor of the 251/1 D.

I would think that an irregular shaped fragment after first penetrating the side stowage box and it contents would lose enough of its energy that it would have a difficult time penetrating armor (thin as it may be) that was designed to withstand small arms fire.

I think it would be even less likely for the fragments to penetrate the sloped armor of the upper hull in that they would be traveling up from ground level and impacting at such a low angle.

The big question is what is the reality here? Does anyone really know?

I can honestly say that my understanding of the abilities and limitations of WWII AFV's is largely influenced by the games I play or have played (with in reason). . I Started with Tobruk, then SL, ASL, Then Steel Panthers. By the time Close Combat came out I knew enough to know you cant trust all game makers to portray these abilities correctly.

I play WWII games to learn about the tactics and reality of the period. CM is doing a great job in their attempts to model real world results and I hope they model this situation as realistically as possible.

Take care and thanks for listening

John

[Fionn]

I have seen pictures of 251/1s absolutely shredded by treeburst and groundburst artillery fire..

I have one group in which roughly a dozen 251s were in an area when an arty stonk came down and literally every one of them is shredded from front to rear. Great gouging holes are ripped into these vehicles on both sides.

I can categorically state that at least 10 didn't receive any direct hits (a few look blackened and burned so I can't say if they did or didn't) but they were definitely knocked out by shrapnel.

Personally I've been surprised by the vulnerability of a lot of the lighter armoured vehicles in CM to HMGs and arty BUT then when I look at my books etc I see a lot of occasions where these vehicles WERE knocked out by just such weapons in real life.

I don't have perfect data to back this up though since it was war and they weren't collating hit percentages etc but I've seen a LOT of HTs knocked out by arty with major holes ripped through their sides.

------------------

___________

Fionn Kelly

Manager of Historical Research,

The Gamers Net - Gaming for Gamers

[coe]

Hmmm, tried to get my 88 mm to fire

AP at a mortar position but it wouldn't,

I was kinda desperate to silence it.

[Lee]

For the record, I'm not saying these HE shells shouldn't be

able to take out a halftrack. I'm just saying that the

*huge* difference in results between the 75mm and 88mm

shells that has been reported just doesn't seem to make

any sense. And thus would like to see some tests run

by Steve and Charles to see if there is a problem there.

Hopefully we'll get those test results fairly soon.

[tss]

I just went through my reference books trying to find the stats of the 75 mm and 88 mm HE rounds. The shell weight of 88 mm was 9.0 kg according to "Itsenäisen Suomen rannikkotykit" and 20 lbs (9.1kg) according to "Handbook of German Military Forces". The weight of the 75 mm HE shell was given as 12.7 lbs (5.4) kg in "Handbook". My other sources don't mention the weight of that particular type of 75 HE shells but in general, 75 and 76 mm HE rounds weight about 6 kg. Unfortunately, no source mentioned the amount of explosive in any shell types.

-Tommi

[Guest Big Time Software]

Yeah, good discussion for sure.

To echo what Fionn just said about how vunerable lightly armored vehicles are in CM, I too am constantly surprised at how easily these suckers are knocked out. This actually was an internal point of discussion even before Fionn got a crack at the Alpha this summer. Charles and I constantly evaluate how "right" something feels, especially when it runs counter to other games we have played. We usually assume the other games have it wrong, but we double check to make sure simply because we know we will have to defend CM when people question its version of reality.

We know that the core ballistics routines and armor penetration code is sound. A bug or two might effect something on the oddball end of things, but we think we have found all the common and uncommon ones already. Rare ones might still be in there, but by definition they aren't statistically important in the overall sense. And of course if they are identified we will fix 'em.

Now, having stated that we are comfortable standing behind the physics of CM, we look at the simulation's results. Again, history is called up here to see if things feel right. We concluded long ago that things are just fine.

The reason why light armor has such a short life in CM is that most often the scenario designers have put AT capabilities in for the opposing side. This spells trouble for such vehicles So if you use your vehicles correctly and wisely, you have a decent chance of retaining them. But if you use them like they are invunerable, or just get VERY unlucky, then you will lose them. To cite an example of the latter, my staging area was hit by indirect 105mm artillery. In quick succession I lost 4 M3 Halftracks from direct and near direct hits. That pretty much stopped my attack cold for about 10 turns. OUCH

Steve

[Guest Zigster]

Projectile weights for the 75 given in Hunnicut are:

APC M61: 14.96 pds

HVAP T45: 8.40 pds

AP M72: 13.94 pds

HE M48: 14.70 pds

Note that these are projectile weights only. Shell weights are much higher.

Muzzle velocities for the M3 75mm gun are:

HE M48 (Supercharge): 1,980 ft/sec

HE M48 (Normal): 1,520 ft/sec

Muzzle Energy of HE projectiles (1/2 MV^2):

HE M48 (Supercharge): 400 ft-tons

HE M48 (Normal): 235 ft-tons

[Bullethead]

Steve said, in the Thread that Would Not Die:

<BLOCKQUOTE>quote:</font><HR>Now, having stated that we are comfortable standing behind the physics of CM, we look at the simulation's results. Again, history is called up here to see if things feel right. We concluded long ago that things are just fine.<HR></BLOCKQUOTE>

Is HE vs. armor really modeled in terms of fragments penetrating? When I look at the detailed info on a weapon, I see "Blast Firepower XX", which I assume refers to the HE ammo. This is 48 for the Tiger I's 88 and 32 for the StuG's 75. This is the only thing I see that might refer to HE, and there is none of the armor penetration details you see for AP ammo.

So my question: is this Blast Firepower number the only thing, or at least the main thing, taken into account when figuring HE damage? As in, this same number gets plugged into routines for figuring damage to armor and infantry? If so, then perhaps it's a bit too abstract for the very different effects sustained by troops and armor from HE near misses.

From looking at these numbers for the StuG and the Tiger, it appears they are based pretty much directly on relative shell explosive volume (assuming the 88 had about 50% more than the 75, as roughly calcu-estimated in previous posts). But everything I know or think I know about HE effects on armor lead me to believe that simple explosive volume isn't very important when it comes to taking out light armor with a near miss. Sure, this number would be a good starting point for effects on unprotected grunts, but it has very little or no effect (to my understanding) on the ability of fragments to penetrate armor from some distance away.

Sure, ARTILLERY fragments could, can, and will SHRED light armor. I've done it myself numerous times. But artillery worthy of the name (say 105mm and up) is a very different thing from a relatively high velocity, small caliber round like the Tiger I's 88.

I echo a previous comment that it would be nice to disable the "no friendly HE fire" part of the AI, or do something to otherwise set up a "target gallery", so that the effects of HE near misses can be studied "scientifically." This is something that's been bugging me with more frequency ever since I saw a screenshot on CMHQ of a Stuart being immobilized by an 88 near miss that was, I believe, AP.

Anyway, thanks for your time.

-Bullethead

[This message has been edited by Bullethead (edited 01-23-2000).]

[Fionn]

In the current beta build HE Armour Penetration IS LISTED just the same as it is for AP rounds.

You have penetration at the 3 distances and 3 slopes for HE and AP. Is that not in the beta demo ? I thought it was but it's been so long I forget.

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Fionn Kelly

Manager of Historical Research,

The Gamers Net - Gaming for Gamers

[Bullethead]

Fionn said:

<BLOCKQUOTE>quote:</font><HR>In the current beta build HE Armour Penetration IS LISTED just the same as it is for AP rounds.<HR></BLOCKQUOTE>

But is that for a direct hit? Having the explosion go off directly on the armor, along with all the momentum of the shell pushing on that one point, is a very different thing from just fragments hitting the armor from an explosion some distance away.

-Bullethead

[Bullethead]

It occurred to me it might be helpful to discuss why fragments from big arty shells do such damage to light armor compared those from smaller shells.

This is where fragment mass becomes really significant. Like JonS said, the ideal anti-personnel fragment size is pretty small, about the size of your thumbnail. And the smaller the shell, the easier it is to consistently get fragments of this size. But as shell size increases, there is an increasing tendency for a lot of the shell casing to stay in much bigger chunks.

So where a small fragment might weigh an ounce or so, the big ones can weigh one or more pounds (say 16 times as much). Hell, battleship shell fragments can weigh hundreds of pounds. With equal velocities, therefore, a 1-pound fragment has 8 times the KE of a 1-ounce fragment, and thus significantly higher chances of penetrating any armor encountered.

As I understand it, the reason for this has to do with fusing. When the fuse goes off, the shell's explosive filler starts to burn both radially and longitudinally from where it touches the fuse. The burning happens nearly instantaneously throughout the shell, of course, but still takes some time. Thus, the burning or at least the build-up of bursting pressure reaches the sides of the shell near the fuse sooner than it does the back of the shell.

With small shells, this isn't really a problem because the fuse sticks back into the shell for a significant proportion of the total filler cavity length. Thus, while it is still usually farther from the end of the fuse to the back of the shell than it is from the side of the fuse to the side of the shell, at the speed the filler burns, this difference isn't significant. For practical purposes, the whole thing goes off essentially at once.

With bigger shells, however, the distance from the end of the fuse to the back of the shell is much greater than from side to side. Thus, before the explosive in the rear part of the shell even begins to burn, the front part of the shell is often already breaking up.

But whatever the real cause is, there is a real tendency for big shell casings to break up into longitudinal gores somewhat like a banana peel instead of shattering into tiny bits throughout their whole length. Between these long gores, however, you do get bunches of the small stuff, and for medium-sized (say 105-120mm) shells the gores often break up into sections the about 4-8" long instead of being the full length of the shell. This type of fragmentation makes big shells true dual-purpose weapons capable of ruining light armor as well as exposed troops with near misses. This is a desirable feature for big shells--there are enough of both types of fragments to do both jobs well at the same time--so I doubt anybody will try to change things.

It's somewhat fuzzy as to the caliber of shell required before this type of "big chunk" fragmentation starts to become a significant feature. It certainly happens for heavy arty (155mm and above), it sometimes happens for medium arty, but I'm pretty sure it doesn't happen much at all for light arty. In fact, it would be counterproductive for light arty because such shells don't have enough surface area to generate enough of both types of fragments to do small anti-personnel and large anti-vehicle fragments at the same time.

-Bullethead