Are Arty Rounds Affected By Vehicle Armor Slope?

[Col Deadmarsh]

If you have a vehicle that has let's say, 8mm of armor on its side with a 30 degree slope, does the slope come into play in CM when an arty shell lands nearby? In other words, will the slope help in deflecting the round or is this only with tanks/AT teams?

[Stalin's Organ]

I doubt it. Unless the round lands on the vehicle then it's over-pressure damage to the entire side of the vehicle - if part of it is sloping to deflect the blast then part's probably sloped to catch it.

The coding required to sort this out would be pretty immense I think.

I think most arty damage is to running gear like tracks, or from occasional direct hits on top (esp on engines), and subsequent abandonment by s ****-scared crew (assuming it isn't real heavy arty that simply smearsa the machine or turns it over!).

[rexford]

If the armor is going to be hit by high velocity shell fragments after a ground hit and there is a danger of some or most piercing the armor, then slope would have a large effect.

Armor hardness would also be a factor against HE fragments, the harder the armor the better against small pieces of shell.

British and American tests show that slope effects are more pronounced for smaller projectiles. The Germans face-hardened their anti-tank gun shields to defeat bullets, and the extra surface hardening might help against HE fragments. British ATG shields were not face-hardened and tank MG bullets pierced them in North Africa.

U-Boat conning towers were reportedly face-hardened to help defeat 20mm aircraft cannon rounds. Aircraft also carry face-hardened armor.

[Col Deadmarsh]

Interesting Rex. Do you know if this is modeled in CM?

Has BTS ever stated that armor slope on vehicles/tanks will have an effect on richocheting arty shells?

I'm sure it's modeled on top for direct hits but what about the sides, front, and back for richochets? Also, what about skirts like the one on the Stug IIIG? Does this help in defelecting shells which land nearby?

I'd seriously like to know if BTS has ever stated this as it seems it would be very important to know, especially if one is on defense and has thin-skinned armor units in stationary positions for most of the game.

[Col Deadmarsh]

C'mon. I can't believe that no one knows the answer to this.

BTS, how about an official comment on this topic?

[rexford]

U.S. Army TM9-1907 has penetration data for HE explosions as a function of distance from blast. Might be interesting to compare the figures to armor on halftracks and armored cars.

HE penetration data might be against soft steel, whereas thin armor on lightly armored vehicles is usually very high hardness (designed to defeat regular bullets and HE frag).

I'll dig out my HE tables.

[Jeff Duquette]

DAMAGE PATTERNS.

a. As distinguished from damage tables, the damage patterns shown in figures 243 to 276 represent individual cases and vary with the remaining velocity of the projectile, the angle of fall, and the height of burst. Both damage tables and damage patterns presuppose a graze or air bursting with no shielding of target. The user of the data given here must make due allowance for target shielding and the penetration of the projectile into the ground before burst. The amount of this penetration will depend upon the remaining velocity, angle of fall of the projectile, the nature of the soil, and the projectile and fuze.

h. In the fragment damage patterns, shadings of different types indicate regions of decreasing density of hits. The regions distinguished are those where there is at least one hit per 1, 4, 10, or 25 square feet of area. These units of area are understood as normal to the fragment trajectories. Unshaded regions entering near the burst do not indicate that there are no effective hits in these regions, but merely that the density of effective hits is less than that belonging to the nearest shaded area. The white centers of the fragment patterns are used to indicate the origin of the polar system above which the missile bursts. In general, these areas suffer the highest type of fragment damage as well as blast damage.

SOURCES OF DATA.

a. The data from which the damage tables and patterns have been derived is taken from measurements of fragment velocity, retardation, shape, and penetration, and the mass and angular distribution of fragments as made at the various army and navy proving grounds and laboratories.

TYPES OF DAMAGE.

a. The types of damage considered are casualties, and normal perforations of mild steel of 1/8-inch, 1/4-inch, and 1/2-inch thickness. A casualty is supposed to be caused by a hit with at least 58 foot-pounds of energy. It is incapacitation and not necessarily death.

Damage occasioned by perforation of 1/8-inch mild steel is considerably effective against airplanes on the ground. In antiaircraft fire against modern bombers, the most effective damage varies from that with 1/8-inch perforation to 3/8-inch perforation of mild steel. Damage in which there are perforations of ¼-inch or ½-inch mild steel is effective against trucks, light armored vehicles, railway rolling stock, and targets of similar resistant nature.

Here is an example of burst pattern and fragmentation distribution:

http://www.geocities.com/tigervib_2000/Crap/105mmHE.html

[Username]

I find it interesting that the 105mm shell that is detonated at a very low angle gives a better all around performance. The round landing at a higher angle is less deadly to the front and rear. this goes against people like rexford who claim such great things about low velocity howitzers over tank guns.

Lewis

[rexford]

Lower velocity often results in thinner shell walls and more fragments per unit area. This is why U.S. 75mm HE puts out a higher number of effective fragments than 76mm and 90mm HE, and comes very close to 105mm output at distances close to detonation.

[Stalin's Organ]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Username:

I find it interesting that the 105mm shell that is detonated at a very low angle gives a better all around performance. The round landing at a higher angle is less deadly to the front and rear. this goes against people like rexford who claim such great things about low velocity howitzers over tank guns.<HR></BLOCKQUOTE>

Really? It matches exactly what little I know of gun/howitzer and mortar fragement patterns.

After a while the pattern changes again - the best angle for impact is, of course, 90 deg from horizontal, where a nice circular pattern of fragments is generated.

Oh, and of course if you are going to worry about it then you need to remember that every shell generates different fragments, and that every fragment hits the armour at a different angle and a different velocity..........

Perhaps when we've all got the equivalent of a couple of Crays on our desk tops it'll happen, but not until then IMO!

[ 07-01-2001: Message edited by: Stalin's Organ ]

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rexford:

Lower velocity often results in thinner shell walls and more fragments per unit area. This is why U.S. 75mm HE puts out a higher number of effective fragments than 76mm and 90mm HE, and comes very close to 105mm output at distances close to detonation.<HR></BLOCKQUOTE>

If you look at the website above, you will see that its only the angle that is changing. They compare a 105mm shell at two different angles. Why you must always mix everything up in your rambling style amazes me.

[Michael Dorosh]

I think its time we all lobbied BTS to ban you know who. He's said one pissy thing after another in every thread he's bothered to post to and I for one, while not affected directly, am getting tired of it. It's one thing to disagree with someone, its another entirely to act like an ass constantly.

[ 07-02-2001: Message edited by: Michael Dorosh ]

[Mattias]

I’m inclined to agree with you Michael.

But, on the other hand, I am convinced that BTS tolerant way of handling the “bad” minority is closely linked to the “good” atmosphere that, after all, prevails here.

BTS is doing a good thing in keeping the banning to an absolute minimum. Working rather on creating a positive environment than repressing a negative one.

A way of thinking one would really like to see extended far beyond the confines of this forum

Just see him as a test of character...

M.

[ 07-02-2001: Message edited by: Mattias ]

[Matthew_Ridgeway]

USeR Said: “If you look at the website above, you will see that its only the angle that is changing. They compare a 105mm shell at two different angles. Why you must always mix everything up in your rambling style amazes me.”

Careful USER, your ignorance is showing again. Remember now yellow = HE.

[Herr Oberst]

User:

Now let me see if I read this correctly.

From the referenced website:

Left figure was "Ground Burst, Shell horizontal at rest", and clearly states 0 degree angle of shell.

Right figure was "Ground Burst, remaining velocity 800 f/s, Range 7,000 yd., charge 5, 105mm How., M2A1", and clearly shows 30 degree angle of shell".

It might just be me, but I'd say there's a fairly big difference between a shell going 0 f/s and one traveling 800 f/s impacting at a 30 degree angle.

Rexford was following on to your earlier comment. You led in with statements concerning "deadliness" and low velocity howitzers. Rexford followed with a potential explanation of why low velocity shells might produce a more "deadly" fragmentation pattern, even in a smaller caliber shell.

And the bone you had to pick with this was what exactly?

[Shipmonkey25]

This isn't a exact answer to your question, but I play the Audey Murphy scenerio a couple of weeks ago, and to my friends and my own surpise we watch several 105mm shells ricohet off the tops of the Jagdpanthers. My best geusss would be that the slope mattered for artillery.

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Herr Oberst:

It might just be me, but I'd say there's a fairly big difference between a shell going 0 f/s and one traveling 800 f/s impacting at a 30 degree angle.

And the bone you had to pick with this was what exactly?<HR></BLOCKQUOTE>

"The round landing at a higher angle is less deadly to the front and rear. this goes against people like rexford who claim such great things about low velocity howitzers over tank guns."

Rexford has previously gone on about how high velocity weapons are inferior, in general, to low velocity EVEN WHEN FIRING THE SAME HE SHELL. His big case is against a german 75mmL70 vs a 75mmL24 if I recall. He claims theres certain dynamics in the vertical dispersion as he calls it.

This is what I am refering to. the graphs refute it.

But He is also refering to here, another one of his theories about uber-sherman shells. I am not sure of all the "math" behind it but he will be more than willing to sell a book about it.

As for your 0 fps, I dont quite get it. A high velocity round lands pretty much flat on the ground. Are you looking for some forward acting force on the graphs?

And as for the canadian guy trying to get the "we" together, no comment. The Ridged guy wouldnt know if he was made a fool of in a thread so I wont even address him.

Lewis

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Colonel_Deadmarsh:

If you have a vehicle that has let's say, 8mm of armor on its side with a 30 degree slope, does the slope come into play in CM when an arty shell lands nearby? In other words, will the slope help in deflecting the round or is this only with tanks/AT teams?<HR></BLOCKQUOTE>

It would certainly come into play in the case of a german halftrack. The downward sloping sides would not protect the occupents to a very near miss. The upwardly projected fragments would strike this area orthoganal. They would more than liekly hit the germans in the butt.

Lewis

[Matthew_Ridgeway]

You know USeR I have always been curious as to weather English is a second language for you? You seem quite adept at gibberish or perhaps it’s mumbo-jumbo. I can’t quite place the origins of your dialect.

[Herr Oberst]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Username:

...Rexford has previously gone on about how high velocity weapons are inferior, in general, to low velocity EVEN WHEN FIRING THE SAME HE SHELL. His big case is against a german 75mmL70 vs a 75mmL24 if I recall. He claims theres certain dynamics in the vertical dispersion as he calls it.

This is what I am refering to. the graphs refute it.

...

As for your 0 fps, I dont quite get it. A high velocity round lands pretty much flat on the ground. Are you looking for some forward acting force on the graphs?

<HR></BLOCKQUOTE>

My impression is that there are multiple differential kinetic forces working on the two shells used to generate those graphics.

(For simplicity, left and right refer to the graphics and their respective shells)

The left shell was at rest with 0 f/s forward movement and 0 rpm rotational speed. I would expect a more uniform circular dispersion of fragments with less at the "rear" of the dispersion pattern owing to the heavy weight of the tail of the shell.

A very nice "clean" test. I'd like to see comparable dispersion patterns for different sizes and types of shells under the same conditions.

The right shell was travelling at 800 f/s, combined with some unknown rpm of rotational speed, and impacting at a 30 degree angle.

So, for this second test we have what I would call an extremely "dirty" comparison, with potentially three confounding factors ignoring all interactions between factors:

<UL TYPE=SQUARE><LI>Factor 1: Angle of incidence at impact.<LI>Factor 2: Unknown rotational speed imparting some unknown force on the fragmentation pattern.<LI>Factor 3: 800 f/s forward motion of the shell that is imparted to the fragments.

So, which factor or factors in what combination caused the results to come out that way? Is horizontal speed the most influential factor? Or is it angle of impact? Or is it the rotational speed? Or what combination?

In lieu of any other data, and with healthy skepticism, I can only conclude that the two dispersion patterns do appear to be different, but I hesitate to say which factor(s) most influenced the outcome.

Yes, I used to be a statistician, and I curse you both for making me think that way again...

In my own poor opinion (and refusing to do any math for this post), if appears to me that the "nose" of the dispersion pattern is buried in the ground, that the "wings" are canted forward on account of the forward momentum of the shell, and the "tail" either plowed into the shell hole, or was at an elevation that caused its fragments to miss the alloted "counting area". But this is just a WAG, nothing more.

As to the differential effects of a low velocity round versus a higher velocity round, would we expect to see a large differential caused by largely differing rotational speeds of the shells at impact?

Logically I think yes. Can I back that with any data? No.

[ 07-03-2001: Message edited by: Herr Oberst ]

[Col Deadmarsh]

What the hell are you guys talking about? I asked what color the sky is and you launch into a discussion on meteorology.

Is there anyone out there who can speak in layman's terms and tell me if what I asked about in my original question is modeled in CM?

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Matthew_Ridgeway:

You know USeR I have always been curious as to weather English is a second language for you? You seem quite adept at gibberish or perhaps it’s mumbo-jumbo. I can’t quite place the origins of your dialect.<HR></BLOCKQUOTE>

Oh the weather is fine here. Thanks for asking Mr. Yellow Shells.

Whether or not your area of the world has education past the grade school level is my burning question.

Lewis

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Colonel_Deadmarsh:

Is there anyone out there who can speak in layman's terms and tell me if what I asked about in my original question is modeled in CM?<HR></BLOCKQUOTE>

I thought I had.

Since the shell produces fragments that are 'attacking' the armor from all different angles themselves, then they have an angular component themselves.

In the case of the 251 halftrack, it can go both ways.

I doubt that the game models this and probably abstracts it somehow.

Lewis

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Herr Oberst:

So, for this second test we have what I would call an extremely "dirty" comparison, with potentially three confounding factors ignoring all interactions between factors:

<UL TYPE=SQUARE><LI>Factor 1: Angle of incidence at impact.<LI>Factor 2: Unknown rotational speed imparting some unknown force on the fragmentation pattern.<LI>Factor 3: 800 f/s forward motion of the shell that is imparted to the fragments.

So, which factor or factors in what combination caused the results to come out that way? Is horizontal speed the most influential factor? Or is it angle of impact? Or is it the rotational speed? Or what combination?

]<HR></BLOCKQUOTE>

I applaud your approach but feel the angle is the reason for the difference.

Most people ignore that the shell is spinning. Just as a sidenote, it can be in the 10's of thousands of RPM. Its effect does not change the pattern in the pics, but it would offset the angle somewhat from the fragments on the side of the shell. The nose parts and tail parts would probably come off spinning but in the same pattern.

The forward motion of the shell can be compared to the related rate of the fragments. In other words, the front pattern would stay the same (but the fragments get a velocity 'kick' in relation to the ground) and the fragments from the shell's side would have an angular component.

In a high velocity gun, the shell lands damn near flat on the ground. I dont think that the translational or rotational velocity would effect the pattern that greatly.

Lewis

[rexford]

WW II German ballistic analysis of HE fire ground patterns due to dispersion show that slow rounds are more accurate against point targets on the ground. My review of the mechanics verified the German findings.

If a 75L42 and an 88L56 are firing HE at a ground point target, the middle of a group of soldiers at 700m, and both rounds have the same vertical scatter about the average flight path, the 75L24 HE will land closer the aim point more often.

Will 75L24 HE be more lethal than 88L56 HE if both land the same distance away? If 75mm fires Sprgr. Patr. KwK(34) and 88 fires any HE round available, 75mm HE will have a higher HE filler % of total weight, and probably will have thinner walls, and should put out more average fragments per unit area.

75mm will land at a higher descent angle than 88mm, but both are landing at relatively shallow angles.

My analysis stopped at which HE lands closer to aim point and which puts out more fragments per unit area (on average).

If there are graphs that dispute this post them on this site for review. Several folks posted data and scans that supported the German ballistic analysis of HE ground dispersion pattern (where shell lands, NOT fragment pattern).