Beating dead Horse - Hispanos x MGFF-20mm

Discussion in 'Game bugs' started by _strafe_, Oct 14, 2006.

  1. _strafe_

    _strafe_ Well-Known Member

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    I've read interesting articles about WWII fighters armament. Many discussion here was made considering the kinetic energy only. That is a function of the projectile weight and the velocity with which it hits the target. BUT in german projectile there was a chemical factor. It is well explosed in that old article:
    "WORLD WAR 2 FIGHTER ARMAMENT EFFECTIVENESS"
    http://www.quarry.nildram.co.uk/WW2guneffect.htm

    Carefull read lead me to these paragraphs:
    "There are two types of energy that may be transmitted to the target; kinetic and chemical. The kinetic energy is a function of the projectile weight and the velocity with which it hits the target. This velocity in turn depends on three factors: The muzzle velocity, the ballistic properties of the projectile, and the distance to the target. There are therefore two fixed elements in calculating the destructiveness of a projectile, its weight and chemical (high explosive or incendiary) content, and one variable element, its velocity. The key issue is the relationship between these three factors.

    "If we compare the values with the few data known from ballistic tests, we have some indications that the factors assumed in the calculations are realistic. The 20x80RB M-Geschoss and the 20x110 (Hispano) HE were rated as about equal; the greater blast effect of the M-Geschoss was countered by the greater penetration and kinetic damage inflicted by the Hispano. They do indeed emerge with similar scores. Also, the Luftwaffe reckoned that it took about four or five times as many 20 mm shells to destroy a heavy bomber as it did 30 mm rounds. The power relationship here is 3.6 times for the MK 108 and 6.2 times for the MK 103, which neatly brackets this observation.


    Who wrote that article is a specialized man, with large knowledgement about guns and ammunition.

    So some adjustments should be done in Hispanos decereasing his power or in MG-FF / MG151 increasing his power. That's not a luftwhining but a fact well explaned for anyone.
     
  2. --q---

    --q--- Well-Known Member

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    It will be called luftwhining or be ignored.
     
  3. Snakeye

    Snakeye Well-Known Member

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    No
    it will be called luftwhining AND ignored ;)

    Besides that's nothing new really...
     
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  4. _strafe_

    _strafe_ Well-Known Member

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    That a good technical source not a "luftwhining".
     
  5. -exec-

    -exec- FH Consultant

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    http://forum.wbfree.net/forums/showthread.php?t=23509
    here i tried to find out which aspects are decisive for armour penetration.
    as you can see this is not too simple and kinetics cannot be classified as only momentum or only energy.
    chemical energy effect is not an obvious too, since it can be spent to kinetic energy of fragments or spent for HE effect.
    and some even said that german detonators did not worked on fabric wings of early soviet fighters, pinning only a little hole.
    not long ago (year?), badger quoted an interersing test of shooting .303 and 7.92 at armoured seatbacks of spits and 109's carried out by britishes.
    mg 17 penetrated armoured plate much more effectively than browning. but at the second stage they shoot at blen/beau(?) fus, and found out that browning is much more effective in penetrating both fus and armoured plate than mg 17.
    therefore i'm against "unified effectiveness formula" similar to williams/gustin's one.
    especially "Multiplying this by ten gives a chemical contribution of 100%, adding the kinetic contribution of 100% gives a total of 200%."
     
  6. --q---

    --q--- Well-Known Member

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    great, it is in russian.

    I dont get it. Is kinetic energy somthing else then only kinetic energy ?

    I do not get the difference. Anyway no matter how the chemical energy is spent it is still en energy that is ultimately transfered to the airframe cousing structural deformations. Basic physics.

    This is modeled right now. The upper wing of i15 cannot be hit by bullets.

    This is off subject. The bug report is about 20mm shells effectivnes.

    I would expect U to be against increasing the dmg factor of chemical energy in ammo. This is becouse I think you are biased, and as a coincidence the russian 20mm shells had the lowest explosive load of all the ammo used in WW2.
     
  7. HoHun

    HoHun FH Beta Tester

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    Hi Exec,

    >therefore i'm against "unified effectiveness formula" similar to williams/gustin's one.
    >especially "Multiplying this by ten gives a chemical contribution of 100%, adding the kinetic contribution of 100% gives a total of 200%."

    If you scroll down on Tony's page, you'll find a comparison based on actual chemical + kinetic energy I prepared for Tony after I had criticized his original formula with similar arguments like you do.

    According to German WW2 research, armour penetration is not a factor in aerial ballistics, by the way, since so little of the aircraft is armoured. The German mine shells attack the stressed skin of aircraft, destroying its structural integrity. They are the most effective type of rounds used in WW2.

    (This explains how they failed to be effective against fabric-covered parts. However, explosions are highly effective against wood surfaces, which develop quickly spreading cracks that damage a much larger area than the same explosion would on a metal aircraft.)

    Regards,

    Henning (HoHun)
     
  8. -exec-

    -exec- FH Consultant

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    Henning, can TNTkg equivalent (is it Joules?) express fugacity and brisancy of the ammo?
    speaking of damage we must speak about destructive characteristics that (not counting target structure) involve fugacity and brisancy parameters.
     
  9. HoHun

    HoHun FH Beta Tester

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    Hi Exec,

    >Henning, can TNTkg equivalent (is it Joules?) express fugacity and brisancy of the ammo?

    As any model, it's an approximation. As far as I know, it's the best available approxmimation.

    If you think you need better accuracy, it's possible to research the compositions of the explosives used in the different rounds. I actually did that for a number of rounds.

    (In fact, if you're smart enough to ask the question, you should be smart enough to find out the range between the weakest and the strongest explosive that was used in WW2 in order to quantify the error in my approximation.)

    >speaking of damage we must speak about destructive characteristics that (not counting target structure) involve fugacity and brisancy parameters.

    Well, how large could the possible error be? Based on the German experience, their MX round was supposedly 30% more powerful than their standard mine round.

    Just look at the energy values with TNT equivalent:

    20 x 110 mm Hispano Mk II HE: 4.86
    20 x 82 mm MG FF/M HE (M): 6.53

    That's a 34% advantage for the MG FF/M mine shell, and as it's less dependend on kinetic energy than the Hispano shell, its advantage is going to be even greater the further out you go.

    So even assuming a 30% error in the TNT assumption in favour of the MG FF/M, the mine shell should be equivalent to the Hispano shell in destructive power. It's going to be much harder to hit anything with the German gun due to its much lower muzzle velocity, but that's entirely independend of what happens if the shell hits home.

    Regards,

    Henning (HoHun)
     
  10. -exec-

    -exec- FH Consultant

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    in fact, i'm smart enough to find out that i am an ignoramus.
    the time i tried to investigate the matter, i understood that the problem is far more complex than i can imagine, and highly probably more complex than williams/gustin's try to representate (that's why i read W&G for only natural parameters, but i ignore imaginary parameters of W&G).

    thus when i created tabahost dm, i set scores mostly by intuition (except 12.7-13.2mm calibre, about which i was consulted by -echo-).

    saying "X 30% more destructive than ordinary Y that can be demonstrated comparing X versus Z" you intrigue me.
    X=Minengeschoß m. Zerl.
    Y=Brandsprenggranatpatronen L'spur m. Zerl
    Z=Hispano Mk. II high-explosive-incendiary round.
    can you explain it again slowly? %)

    another factor stated by W&G is belt composition in which we have:
    MG FF/M: 90pts / 89pts / 206pts (with average 128 pts)
    Hispano II: 201pts, 201pts, 201pts (with average 201 pts)
    with constant flames of great variety of shooting results, i supposed every projectile to bear fixed average damage score
    i.e. in tabahost dm every...
    ...hispano2 shell carries 35 high-explosive points and 31 armour-piercing points
    ...mg ff/m shell carries 25 high-explosive points and 16 armour-percing points
    equally.

    the question is not about my obstinacy, but good explication of the problem.
     
  11. HoHun

    HoHun FH Beta Tester

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    Hi Exec,

    >can you explain it again slowly? %)

    There are two mine shell types, the early/mid-war mine shell and the late war "MX" shell which was claimed to be 30% more destructive at about the same weight of explosive. That can be used to make an informed guess about the impact of different explosives.

    >MG FF/M: 90pts / 89pts / 206pts (with average 128 pts)
    >Hispano II: 201pts, 201pts, 201pts (with average 201 pts)

    That's Tony's model?

    I'd use energy:

    MG FF/M: 40,3 kJ/40,2 kJ/135,6 kJ (average 72.0 kJ)
    Hispano II: 106,2 kJ/106,2 kJ/106,2 kJ (average 106,2 kJ)

    I'd also use a 1:1:3 belting for the MG FF/M as suggested by the German "Schießfibel", yielding an average of 97,5 kJ.

    So the average MG FF/M projectile yields 92% of the energy of the average Hispano II projectile.

    You could also break this down for kinetic energy and chemical energy:

    MG FF/M: 20,0 KJ + 19,7 kJ + 3 * 22,5 kJ kinetic (average 21,5 kJ)
    Hispano II: average 48,1 kJ kinetic

    So the Hispano has a much higher armour-piercing capability (The MG FF/M has only 45%).

    MG FF/M: 20,3 KJ + 20,6 kJ + 3 * 113,1 kJ chemical (average 76,0 kJ)
    Hispano II: average 58,1 kJ chemical

    So the MG FF/M has a 31% higher explosive capability.

    (Note that rate of fire has not entered the picture yet.)

    The German experience and research indicated that much larger parts of the aircraft were vulnerable against explosives than against armour-piercing ammunition.

    Just for the sake of the example, assume that the ratio is 80% unarmoured target area, 20% armoured. Unarmoured area should be only susceptible to chemical energy, armoured area only to kinetic energy for our example.

    That yields:

    MG FF/M: 80% * 131% + 20% * 45% = 114%
    Hispano II: 80% * 100% + 20% * 100% = 100%

    That's a crude example and I don't say that it's anywhere near realistic, but it explains the idea behind the German mine shells. (For a better example, you'd have to use the probability of kill instead of the energy, but that's another can of worms :)

    Hope it's easier to understand now ;-)

    Regards,

    Henning (HoHun)
     
  12. -exec-

    -exec- FH Consultant

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    1.if minengeshoß is so effective, why no other nations used that? technologically nations were equal. may it's not as good as some suppose?

    2.kinetical energy cannot be easily converted to armour penetrating capabilities, since the function is non-linear, not even proportional to integer exponent. effect is not depending directly from kinetic energy or kinetic impulse. so i won't count on pure kinetics (and pure chem as well). KJ is not a convincing factor.

    3.how can we distinct early-mid war and latewar effect?

    i'd just raise MG FF/M scores from 25HE+16AP to 30HE+16AP
    Hispano (all versions) has 35HE+31AP points.

    btw, Navy Type 99 mod.I and mod.II must be raised too? now 25+16
    is it related to MG 151/20 as well? now 25+31.
    should ShVAK be changed? now 20+16.
    ____________________________________________________
    p.s.found a bug - Hispano V's AP must be lower. %)
     
  13. HoHun

    HoHun FH Beta Tester

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    Hi Exec,

    >1.if minengeshoß is so effective, why no other nations used that? technologically nations were equal. may it's not as good as some suppose?

    According to Tony, the mine shell principle was adopted by all nations after WW2. It had been a secret German development, and it required both the recognition of the basic effect and some special manufacturing technology that took some time to develop. (The thin-walled projectiles had to be drawn instead of milled, and they required special light-weight fuzes because the heavier standard fuzes would have caused the thin-walled projectiles to collapse on firing. The German developed chemical fuzes for that, though it might be they came up with more conventional fuzes later in the war.)

    To sum it up, I don't think it was easy to manufacture combat-ready mine shells, even if you realized their value which I think the Allies did not to the full extent until after the war.

    >2.kinetical energy cannot be easily converted to armour penetrating capabilities, since the function is non-linear, not even proportional to integer exponent. effect is not depending directly from kinetic energy or kinetic impulse. so i won't count on pure kinetics (and pure chem as well). KJ is not a convincing factor.

    While there are several variables influencing armour penetration, kinetic energy is clearly a highly important one. In fact, if we look at an identical situation and consider technology between the different powers as similar (which in the case of armour-piercing ammunition according to my knowledge should be justified), kinetic energy appear to be the most important factor.

    >3.how can we distinct early-mid war and latewar effect?

    Hm, I'm not sure what you refer to. Different explosive compositions?

    >i'd just raise MG FF/M scores from 25HE+16AP to 30HE+16AP
    Hispano (all versions) has 35HE+31AP points.

    Well, I don't know how these scores are evaluated in the Freehost damage model, but I'd think that the MG FF/M's "HE" score should be higher than the Hispano's.

    The mine shell lands 20.24 g of explosives with each hit. The Hispano HE shell only lands 10.4 g with each hit.

    With the typical belting patterns, 60% of the MG FF/M's rounds are mine shells, but only 50% of the Hispano rounds are HE shells.

    (For the MG FF/M, it's 20% HEIT with just 3.68 g of explosives, and 20% API with just 3.627 g of incendiary. For the Hispano, it's 50% API projectiles with 10.4 g of incendiary.)

    So you could go into more detail:

    10 rounds MG FF/M: 121.44 g explosives, 14.614 g of incendiary, 2 armour piercing shells at 40.3 kJ total energy each.

    10 rounds Hispano: 52 g explosives, 52 g of incendiary, 5 armour piercing shells at 106 kJ total energy each.

    Assuming the Hispano is 100% explosive, 100% armour piercing, I'd say the MG FF/M would have a score of 234% explosive, 15% armour piercing.

    (100% explosive effect is not necessarily equal to 100% armour piercing effect in destructivity. That's another can of worms.)

    To check it with our previous assumption of 80% unarmoured, 20% armoured area:

    MG FF/M: 187,2% explosive effect, 3% armour piercing effect on target.

    Hispano: 80% explosive effect, 20% armour piercing effect on target.

    >btw, Navy Type 99 mod.I and mod.II must be raised too? now 25+16

    The Japanese had no mine shells. Their HE shells only had:

    20mm Type 99-1: 7.68 g explosives
    20mm Type 99-2: 7.68 g explosives
    20mm Ho-5: 9.48 g explosives (Tony also lists AP shells for this gun)

    >is it related to MG 151/20 as well? now 25+31.

    The explosive/incendiary content of the MG 151/20 is the same as for the MG FF/M. Only the shell velocities are higher.

    >should ShVAK be changed? now 20+16.

    Hm, I think someone pointed out that Tony's data was not accurate for the ShVAK, but here is what I have:

    20 mm HE: 5.7 g explosives
    20 mm API: 1.92 g incendiary, total energy 37.7 kJ (at 750 m/s)

    So we could compare it to the Hispano, too, assuming 1:1 HE/API:

    ShVAK: 74% explosives, 36% armour piercing.

    (This is not entirely fair for the ShVAK since its HE shells are faster than the MG FF/M's and thus add some additional damage - which of course also applies to the Hispano's. That's why it's sensible to use total energy for the explosive rounds, too.)

    Regards,

    Henning (HoHun)
     
  14. -exec-

    -exec- FH Consultant

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    again, as i mentionned earlier here http://forum.wbfree.net/forums/showthread.php?t=23509
    armour penetrating measured in mm of etalon armour is not energy neither impulse.
    it's roughly b≈power(m*V*V*cos(a)*cos(a);2.0/3.0)/d*power(cos(a);n) where n is a factor of b/d (armourthickness/diameter).
    where's energy here?
     
    Last edited: Oct 27, 2006
  15. -exec-

    -exec- FH Consultant

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    will reread later carefully
     
  16. HoHun

    HoHun FH Beta Tester

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    Hi Exec,

    >armour penetrating measured in mm of etalon armour is not energy neither impulse.

    >it's roughly b≈power(m*V*V*cos(a)*cos(a);2.0/3.0)/d*power(cos(a);n) >where n is a factor of b/d (armourthickness/diameter).
    >where's energy here?

    Ekin = 1/2*m*V*V

    =>

    b≈power(2*Ekin*cos(a)*cos(a);2.0/3.0)/d*power(cos(a);n)

    :)

    Regards,

    Henning (HoHun)
     
  17. RolandGarros

    RolandGarros Well-Known Member

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    no bits about temperature or Mach number?
     
  18. _strafe_

    _strafe_ Well-Known Member

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    I'm very proud of you Henning about your wonderful contribution to this post and helping game's improvement. W T G ! :cheers:

    You're able to explain clear what some guys has been tried for several times. You are a master teacher. :@prayer: :@prayer:
     
  19. Gunther

    Gunther Well-Known Member

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    WTG hohun:cheers:
     
  20. badger

    badger FH Beta Tester

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    Looking at the numbers i would say that Hispano would be a hell more effective against real WWII plane, because of its 3x incendary content and kinetic power to deliver it to the flamable spots on planes.

    MG-FF/M would do VERY nice local damage, but that's all, you need to hit it in the "soft" spot to shot down the plane, cause due to very thin walls of the round it doesn't produce much fragments to carry the damage futher inside the plane.