Author Topic: The Void between Machine guns and cannons. (Read 9136 times)

Toad · « **Reply #90 on:** August 05, 2003, 05:46:33 PM »

Well Brady can you give me the Ballistic Coefficient of the more prominent LW projectiles their individual weights and their muzzle velocity?

The height of the gun sight above the actual barrel would be great as well. I know this varies between aircraft and even between guns on aircraft (wing and cowl).

With those numbers we could run some good trajectories and energy computations at various ranges.

Sable · « **Reply #91 on:** August 05, 2003, 06:07:36 PM »

Quote

Originally posted by john9001
very interresting sable , but exactly how do they know how a plane was shot down and what systems were hit? did the NTSB do a investigation of each crash site, or did the Air Force just make a "educated guess"?

I'd have to look at it again. I believe the study used aircraft that were recovered (i.e. ones that went down over land and could be found). There was a certain percentage of "unknown" losses too where they couldn't determine the cause of loss.

The one thing I really notice about this study is that it agrees very strongly with most pilots stories of combat I've read ... lots of engine hits, fire, and pilot hits.

Hooligan · « **Reply #92 on:** August 05, 2003, 06:42:52 PM »

From Aircraft Vulnerability in World War II
A. H. Peterson
Rand Corporation, 1950
Document number # RM-402
Page 53

Aircraft lost to hit ratio for hits on components (F4U, F6F, SB2C, TBM,
Note: all radial-engined)
From Japanese Aircraft Fire – Sept 44 –August 45

Hit location # hit #lost Loss %
Propellor 9 0 0
Powerplant 37 23 62.2
Structure 215 23 10.7
Pilot/flight controls 97 74 76.3
Surface Controls 27 0 0
Oil System 27 23 85.3
Fuel System 30 24 80.0
Hydraulic System 35 21 60.0
Electrical System 6 0 0
Other 18 5 27.8

Total 501 193 38.5

If I arrange the causes of losses in weighted order:

Hit location #lost % cause of total losses
Pilot/flight controls 74 43.0
Fuel System 24 14.0
Powerplant 23 13.4
Oil System 23 13.4
Structure 23 13.4
Other 5 2.9

Toad:

G1-Ballistic coefficients for German 13mm to 20mm rounds are in the range of .20 to .48. The 90g 20mm Mine shell (for example)has a g1-BC of .263.

G1-BCs for BMG .50 are in the range of .65 to .72.

round mass mv g1-bc
20mm Mine 90g 805m/s .263
20mm HE/I 115g 705m/s .48
13mm HE/I 34g 750 m/s .32
13mm AP-T 38.5g 710 m/s .36
US BMG .50 AP/I 42.9g 938 m/s .693

I'm sure you have already seen my comparison of .50 and 151 trajectories but... here it is anyway:

http://home.earthlink.net/~jayboyer/ballistics.htm

Niklas:

You're already argued with Pyro that Allied rounds don't decelerate properly. Admittedly you seem to have largely ignored what he said but perhaps you should look at the thread again.

http://www.hitechcreations.com/forums/showthread.php?threadid=28283&referrerid=1953

Hooligan

brady · « **Reply #93 on:** August 05, 2003, 07:46:21 PM »

Well Toad, looks like he beat to it, the rest of the data you mentioned is readly available on a ton of web sights in in a number off book's.

I am not entirely shure what the sight height has to do with anything being mentioned hear, but it could easly be arived at by doing some simple math, and what were realy talking about hear is effect on impact (or at least I am).

My main point is that the lower velocity HEI type rounds are suffering in their effect in the game since the damage effect seams to be tied to closely to the Velocity on impact, in other words the destrucive force (or damage on impact) is not being properly modeled for these rounds.

Now the other issues are not ones I am presently pursuing althought they do relate in a way to the above case.

The type 99 rounds should have the same effect on impact and in AH their is a big differance in this effect, all signs point to the engery on impact being the cheif culpert in this undermodeling, since the HEI rounds they fire are the same and since they should generate the same effect(or near to it) we seam to have a problem.

A quote from Tonys sight, taken from above:

""if the projectile is primarily relying on HE blast or incendiary effect, the velocity with which it strikes the target is almost immaterial. Provided that it hits with sufficient force to penetrate the skin and activate the fuze, the damage inflicted will remain constant. "

This effect is not I beleave represented in AH to any apricable degree which is why the Hispano and the 50cal are so effective in the game.

Toad · « **Reply #94 on:** August 05, 2003, 10:15:34 PM »

Brady, Hooli provided data for the Mg151 20mm Mine shell and the Mg151 20mm APHE shell. No data for the 13mm or 15 mm at all.

A "range" of ballistic coefficients is useless in the formula. You need THE BC of each projectile to get accurate trajectory.

Sight height deals with trajectory relative to line of sight. The bullet path with respect to the pilot's LOS, if you will.

I don't have any books that give 13mm or 15mm BC's. I've searched the web and not found them.

Give me hand here, OK? Take a few minutes and give me the BC's for those with the sources and I'll check them out. I'm sure from what you've posted that you have all this stuff.

Your main point is that you think the chemical energy of the HEI shells is not being fully modeled? Is this for all HEI, or just LW? You think the Hispano is incorrectly or correctly modeled?

OK. What do you base this theory upon?

Specifically, on the Type 99 rounds your saying they should have the "same effect on impact" as what? Are you talking about the different versions of Type 99 or in comparison to other HEI rounds?

Hooligan · « **Reply #95 on:** August 05, 2003, 11:16:15 PM »

Toad: I added some data for you in an edit.

Hooligan

brady · « **Reply #96 on:** August 05, 2003, 11:50:50 PM »

Toad I beleave Holigan covered you their, but I never said didely about anything that had to with the balistics/trajectory of any of the weapons except in a very general since, I made no arguments aganst anything in AH except the relaive effectivenss of the Type 99's and I asumed that since these two guns the Type 99 MK I and MK II are so dislimer in their preformance on impact that their is quiet likely a conection to all other guns of a similar nature in AH.

In short that the Balistics/ trajectory of the weapons is not realy all that important hear ( nore was it realy a point i raised) since my main concern at present is the Type 99 isue, now if I am right on this issue then everything else would I asume warent futher looking into or it could just be a case specific problem in how one or both Type 99's are modeled.

Raed this Thread:

http://www.hitechcreations.com/forums/showthread.php?s=&postid=787074#post787074

Now all of my TM series books are presently about an hour away in Storage unfortunatly, if you nead some of the data in them I could arange to make a trip to my storage to dig them out, howeaver Pyro should have the coppy I made of the Japanese voulms I sent him, I beleave he has the German one and I think I sent him my coppyes from the Italian one that covvered the Breda gun's used in AH, it was about 2 1/2 years ago though that I sent them to him so I cant be shure on the later.

niklas · « **Reply #97 on:** August 06, 2003, 04:23:42 AM »

Hooligan: I did not ignore this thread, actually this is the 20mm chart i was talking about.
If you have it too (probably) you can see that the 20mm chart is for AP (!!!), which is not reprenstative for a HE shell. Unfortunatly Pyro never gave me a debug output of the 20mm HS shell at ~1000yards. And we DO have HE shells here imo.

Yes, the AH 20mm HS is more or less flying like this velocity chart imo, and this is wrong.

The HE shell starts at higher muzzle velocity and has naturally more drag, will decelerate faster at each distance point.

The HE shell has less mass, assuming same shape it will decelerate faster in ratio of the masses compared to the AP at each veloctiy (Is 2570grains to 2030grains the correct ratio? If so, the HE shell will decelarate at equal speed already more than 25% faster than the AP shell, ONLY due to the mass difference!!).

The HE shell has a flat nose which produces much more drag compared to the rather sharp nose of the AP, especailly at supersonic speeds. On the other hand i don´t know exact drag values, but i think minimum 20-25% more drag.

So alone due to mass and shape the HE shell will decelerate ~40-50% faster at a given veloctity compared to the AP!!! MINIMUM!!!
And this does not happen in AH, here the shell flies like a AP shell with the nice advantage of a higher muzzle veloctiy, because THIS is definitly modelled.....

Meanwhile i run a quick test. The mean velocity from 650y to 850y is probably still 70% of the mean velocity from 50-350y, comparing tracers.

niklas

Toad · « **Reply #98 on:** August 06, 2003, 08:25:06 AM »

Thanks Hooli!

I'll run some trajectories, probably later in the week. While trajectory doesn't deal with the chemical energy aspect, it does wonders (for those who understand ballistics) with respect to explaining range and hit probabilities. I wonder if the guys who grew up reading Jack O'Connor are the ones having trouble?

BTW, anyone have the BC's for the common Japanese projectiles, MG and Cannon?

Brady, I read the thread. You're concerned with the apparent difference in "leathality" between the early and later Type 99 since the chemical energy should be the same although admittedly the ballistic energy is different.

I think we can assume that Pyro knows/realizes/has the data on the differences and similarities in the two projectiles, right?

So now there's three possibilities:

1) There's an error in the modeling and the two projectiles should do very close to the same damage.

2) There's no error in the modeling and Pyro has some valid reason for making the "leathality" different.

3) Your test in the SEA was flawed for some unknown reason and you did not get accurate results.

Now, I have no idea which of these might be the "right" one or if these three are the only ones.

However, I do have a suggestion for you. Try a post directed at Pyro and lay out the case in an objective manner with supporting statements like Tony's.

Skip the clever little insinuations that HTC is deliberately biased in their modeling like this one:

Quote

Originally posted by brady
I think Urchin is being to cleaver again:) " The Allied High" nick name, for ah was after all earned:)

Because if I read that in a post directed to me or about my work, I'd be thinking "screw you chum... I'm not even going to deal with a person as clearly biased as you are".

Then, if you don't get an answer in a reasonable amount of time, pick up the phone. I think Pyro will address your concerns IF you present them in a non-confrontational way.

Good luck. I hope to read the explanation here soon.

Hooligan · « **Reply #99 on:** August 06, 2003, 10:34:10 AM »

Quote

And we DO have HE shells here imo.

As far as I understand: HTC does not model mixes of shells in the belt, nor do they do in-depth modelling of HE or AP effects when the shell hits... All rounds are treated as hybrids and they share some of the benefits and deficiencies of both the HE and AP rounds.

As far as the ballistics of a particular gun, maybe HTC picks one shell type (AP or HE) and bases ballistics off all guns on the same type. Maybe they average the mass and BC of the AP and HE rounds and use that.

However my bet is that whatever they do for the Hispano, they do exactly the same thing for the Mg151 (and every other damn gun). In general ballistics for HE shells are better out to 300-500 yards because of their higher initial velocity. At longer ranges AP rounds will perform better. If HTC is modelling HE round ballistics for everything, then this makes the guns a bit better at medium and short ranges. If HTC is modelling AP ballistics for everything then all the guns will be a bit better at long and extremely long range.

HTC could purposely be modelling two weapons with wildy different assumptions so as to intentionally provide a weapon with an unrealistic advantage. I don't think this is happening, although you clearly do.

No matter what uniform modelling criteria HTC is using, the end result is going to be the same: i.e. Hispano rounds of all types have both a much higher initial velocity and much superior BC to equivalent German 20mm rounds. Hispano trajectories will be much flatter and quicker. Get over it.

Hooligan

MANDOBLE · « **Reply #100 on:** August 06, 2003, 12:54:39 PM »

About ballistics and aiming, they are also related to gun shaking the wings. The gun disposition on wing roots (the stronger and less flexible part of the wings) for 190/Ta or central for 109 should be a clear advantage over the outer wing hispano mounting on Spits, Typhs and HogsC. Recoil effect should also be much more noticeable for hispanos. This effect is almost unnoticeable on AH hispano armed planes, so, the aiming is extremely easy even with prolonged burts.

Hooligan · « **Reply #101 on:** August 06, 2003, 02:06:17 PM »

Use the .target command to look at the dispersion of the gun packages. Guns which are mounted far out on the wings clearly show worse dispersion than centered mounted guns or guns that are mounted close in. All of this stuff has been beaten to death before on the BBS. If you are a crappy shot, maybe you should avoid gun packages with poor ballistics.

Hooligan

MANDOBLE · « **Reply #102 on:** August 06, 2003, 06:19:20 PM »

Quote

Originally posted by Hooligan
Guns which are mounted far out on the wings clearly show worse dispersion

Really? Opposite effect in my test with Spit hispanos compared to 190A8 2x20mm, conv set at 300 yards and target at 300 yards. Have u really done that test?

Tony Williams · « **Reply #103 on:** August 07, 2003, 01:01:19 AM »

Quote

Originally posted by brady

The type 99 rounds should have the same effect on impact and in AH their is a big differance in this effect, all signs point to the engery on impact being the cheif culpert in this undermodeling, since the HEI rounds they fire are the same and since they should generate the same effect(or near to it) we seam to have a problem.

A quote from Tonys sight, taken from above:

""if the projectile is primarily relying on HE blast or incendiary effect, the velocity with which it strikes the target is almost immaterial. Provided that it hits with sufficient force to penetrate the skin and activate the fuze, the damage inflicted will remain constant. "

Well, only the M-Geschoss relied heavily on blast effect (and possibly the light IJA 20mm Ho-5 HEIs), the more strongly constructed rounds like the Hispano and Type 99 relied more on kinetic damage via shell fragments, plus starting fires. It also depends on the fuzing - a delay-action fuze enables a heavy HE to inflict kinetic damage on the way in.

I think that the 99-2 should inflict more damage than a 99-1, but not much more.

Tony Williams: Military gun and ammunition website and Discussion forum

brady · « **Reply #104 on:** August 07, 2003, 01:26:12 AM »

From the other thread:

I said:

"So a 50% diferance in the Destructive effect of the round as evidanced from my testing would not be correct in terms of preformance modeling. If we are to sight your figures from above they should be far closer to one another, somthing on the order of 80% as effective for the Type 99 MK I, compared to the Type 99MK II. "

Tony Said:

"I agree with you that there should not be a huge difference in destructive effect between the two. Probably the major advantage of the higher velocity of the 99-2 was that it improved the hit probability. "

Again TY Tony for all the help you give many of us in better understanding this very interesting subject.