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Jojo Zerach





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PostPosted: Mon 26 Mar, 2012 1:00 pm    Post subject:         Reply with quote

Benjamin H. Abbott wrote:
Kel Rekuta wrote:
[Benny, that's apples and kumquats. A guillotine blade is extremely fine and functions as a shear. A punch is measured by blunt force exerted over a relatively rectangular area. Useless comparison.


It wasn't a comparison. I mentioned the guillotine kinetic energy figure as an aside. The punch numbers, however, do suggest that Marciano could have put a katar through a 3mm breastplate of the best steel. I find this exceedingly unlikely. If the Marciano measurement is at all correct, I doubt it applies to penetrating armor. If punching just delivers more energy than hand weapons, it's probably does so over a long period of time or in a different manner. The bottom line is that we need more studies of the kinetic energy delivered by swords, axes, spears, and so on.


I remember reading in an old book about armour (Edwardian period~), the author mentioned one of his friends tested an Italian breastplate (15thC?) by putting it on a table, and making a downward strike on it with a heavy rondel dagger, using all his strength. The dagger left a barely noticeable mark on the breastplate.
I imagine such armour would be proof against almost any melee weapon.
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Dan Howard




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PostPosted: Mon 26 Mar, 2012 1:13 pm    Post subject:         Reply with quote

Benjamin H. Abbott wrote:
The book From Sumer to Rome includes kinetic energy numbers for various ancient weapons. I'm skeptical that these tests reflects what experienced historical warriors managed.

That book is riddled with errors and is virtually useless as a source for anything related to the Bronze Age.
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Timo Nieminen




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PostPosted: Mon 26 Mar, 2012 1:27 pm    Post subject:         Reply with quote

Jojo Zerach wrote:

I agree that 21.7 J is much lower than an experienced ancient slinger would deliver., but 400 J seems a bit excessive.
I recall ancient Greek/Roman writers mentioning the slings ability to penetrate unprotected skin and cause bruises through leather armour, but it doesn't seem to have been a very effective weapon for penetrating armour.
The sling seems to have fallen out of favor as a combat weapon during medieval Europe, probably due to the greatly increased use of armour by medieval armies.


400J is realistic. About 100J per 100g if getting a range of 200m. A not-large lead egg is about 500-600g.

I've done 1000J with a staff sling.

(To easily get KE in joules from range in metres, KE = 5*range*mass, with the mass in kg. This ignores air resistance, and is therefore the minimum initial KE.)

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Timo Nieminen




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PostPosted: Mon 26 Mar, 2012 2:02 pm    Post subject:         Reply with quote

What we have available, as our starting point, are reasonably reliable numbers for penetration of metal plate that is held fixed in position, for penetration by a not-too-slow sharp arrow or a blunt bullet. Penetration in these cases depends on the energy of the projectile.

What are the problems?

Are the test plates suitable? Williams discusses the equivalence of test metal plates and real armour. This isn't a big problem. Only worry about this if the big problems get solved!

Penetration energy depends on the width of the arrowhead and the size of the bullet. A bigger head/bullet needs to make a bigger hole, and will need more energy to do it. For firearm tests where real bullets are fired at plates, we get this taken into account automatically. For different sizes of arrowheads, what to do? Take penetration energies as approximate only. (Thinner (thus lighter) arrows should get better penetration if they can manage the same energy (which would require a more efficient bow).) Heavy sling shot being larger than pistol shot, we might not get good penetration even if we can get to penetration-by-pistol energies.

I don't think we have any good penetration energies for sword or axe cuts. Thrusts by swords or spears or polearm spikes, or blows by polearms with side-spikes can be compared with arrow penetration (but might need more energy due to needing a larger hole). For cuts, and thrusts/strikes needing larger holes, the arrow energy provides a minimum energy that we would need. If you exceed that minimum energy, perhaps it still isn't effective. If you don't, then it won't be.

What about slow strikes, where a weapon is placed in position against armour, and pushed in? For a fixed plate, the same energy will still be needed - this is the energy required to deform the plate. Yes, this does depend somewhat on how quickly you do it, but the arrow energy is a usable approximation. But in this case, the initial energy of the weapon is not a useful quantity. What we would need to know is the force required to deform/pierce the armour, and the distance over which we need to apply that force as we push the weapon in. (The combination of this force and distance is what the energy tells us.) This would benefit from more tests. Might not be relevant when considering better than thin plate.

What about plates not fixed in place? An armoured human on the battlefield is not fixed in place - hit them, and they move. The energy required to penetrated the armour will be the same. But some of the energy of the weapon will become kinetic energy of the target, if the target moves, and not be available for penetrating armour. If you treat the armour + wearer as a single rigid object that is free to move, this is easy to deal with.

M = mass of armour + wearer.
m = mass of arrow (or other weapon)
v = speed of arrow.

Initial momentum is mv; this will be the final momentum (since momentum is conserved). So, the final speed will be

V = mv/(m+M).

So, the final kinetic energy will be

KE_final = (1/2) * (m+M) * V^2 = (1/2) mv^2 * m/(m+M).

Therefore, a fraction m/(m+M) of the initial kinetic energy is not available for penetration of armour.

For a 100g arrow and a 100kg target, we can ignore this. But it's worse than this, because the target isn't rigid. Hit the target in the arm with a halberd, and the arm can move independently of the body. Hit flexible armour (even with an arrow), and the armour will move easily. (Therefore, brigandine should offer better protection against arrow penetration through a plate, for the same thickness.) This gets very complicated, very soon.

The moral of this last story is that we can safely use the available penetration energies for big pieces of plate attached to weighty targets (like a torso), for weapons that aren't too heavy. Beyond that, they provide a lower limit to the required energy - you will need at least that much, and perhaps much more.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Jojo Zerach





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PostPosted: Mon 26 Mar, 2012 2:32 pm    Post subject:         Reply with quote

Timo Nieminen wrote:
Jojo Zerach wrote:

I agree that 21.7 J is much lower than an experienced ancient slinger would deliver., but 400 J seems a bit excessive.
I recall ancient Greek/Roman writers mentioning the slings ability to penetrate unprotected skin and cause bruises through leather armour, but it doesn't seem to have been a very effective weapon for penetrating armour.
The sling seems to have fallen out of favor as a combat weapon during medieval Europe, probably due to the greatly increased use of armour by medieval armies.


400J is realistic. About 100J per 100g if getting a range of 200m. A not-large lead egg is about 500-600g.

I've done 1000J with a staff sling.

(To easily get KE in joules from range in metres, KE = 5*range*mass, with the mass in kg. This ignores air resistance, and is therefore the minimum initial KE.)


I can see how it wouldn't be hard to get 400 J with a heavy projectile, but many ancient lead sling bullets were quite small.
A .38 special bullet at about 900 ft/s delivers roughly 200 J. Some ancient sling bullets were not much bigger than a .38 bullet, and moved 4-5 times slower. When you consider doubling velocity has an inordinate effect on energy, 20-30 J actually sounds reasonable for a light sling bullet moving at 200 ft/s.
Of course much larger projectiles were also used, so I guess it'd just depend on the ammunition.
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Timo Nieminen




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PostPosted: Mon 26 Mar, 2012 6:36 pm    Post subject:         Reply with quote

Jojo Zerach wrote:

I can see how it wouldn't be hard to get 400 J with a heavy projectile, but many ancient lead sling bullets were quite small.
A .38 special bullet at about 900 ft/s delivers roughly 200 J. Some ancient sling bullets were not much bigger than a .38 bullet, and moved 4-5 times slower. When you consider doubling velocity has an inordinate effect on energy, 20-30 J actually sounds reasonable for a light sling bullet moving at 200 ft/s.
Of course much larger projectiles were also used, so I guess it'd just depend on the ammunition.


Common small lead sling shot would be about 30g (1oz); clay shot of similar size would be about the mass of a .38 special. (At about 900fps, this should be about 400J.)

The "official" world record for lead shot range with a sling is 437m, with 52g shot; that's about 113J (There's a reported modern heavy stone (8oz, 375 yards) that would have been about 128J). Normal is 30-70g or so? But a good slinger with shot like that should manage 50J or more, shooting with a suitable sling and technique for range. This is much, much less than needed to penetrate even 1mm plate. Padding or other textile armour should be very helpful. Slings like this staying in use tell you that a significant part of the opposing armies didn't have armour of this standard

Vertical plane underarm doesn't give you the best range, but it's easy with heavy shot/stones. Likewise, staff sling. Because the shot gets bigger, the extra energy still won't be enough to penetrate armour. Injure through metal armour, perhaps. I wouldn't want to be hit like that through padding alone!

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Jojo Zerach





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PostPosted: Mon 26 Mar, 2012 7:35 pm    Post subject:         Reply with quote

On average, ancient armies didn't wear as much armor as late medieval armies, which is probably one of the reasons the sling was so popular.
Across the ancient world, the sling seems to have been regarded as a fair equal to the bow in it's effectiveness. But when the Spanish deployed sligners against the English at Najera in 1367, it was a complete disaster.
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Benjamin H. Abbott




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PostPosted: Mon 26 Mar, 2012 7:58 pm    Post subject:         Reply with quote

The 400 J calculation comes from Melvin Gaylor's distance record, which would require 365 J in a vacuum. The actual kinetic up close would probably be somewhat more than 400 J. Similarly, Vernon Morton's record produces the minimum figure of 354 J. I suspect these numbers reflect the performance of the best Spanish slingers at Nájera in 1367, whom Froissart claimed broke helmets. That's probably an exaggeration, but I bet heavy stones from strong and skilled slingers could potentially knock out an armored foe. While the Spanish slingers and crossbowmen lost the confrontation with English archers, they fought well enough to earn an honorable mention in the chronicles. That's more than you can say about many of the missile troops who opposed the English during this period. In the fifteenth century, you have a volley of a thousand crossbow bolts against English archers that did no more harm to them than "a shower of rotten apples." I'm still trying to figure that one out. Confused
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Dan Howard




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PostPosted: Mon 26 Mar, 2012 11:01 pm    Post subject:         Reply with quote

Jojo Zerach wrote:
Across the ancient world, the sling seems to have been regarded as a fair equal to the bow in it's effectiveness.

I'm not sure that this is true. Commanders usually only resorted to slingers when they couldn't field archers. If a particular soldier was competent in both bow and sling then he would use a bow.
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Benjamin H. Abbott




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PostPosted: Mon 26 Mar, 2012 11:40 pm    Post subject:         Reply with quote

As far as effectiveness against armor goes, the Spanish considered slings more dangerous than bows in the Aztec and especially Inca areas of the Americas. That could be because neither group had especially potent archers, but you have accounts of Incan slings breaking swords and killing horses. Cortes complained about getting battered by stones.
Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Johan Gemvik




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PostPosted: Wed 28 Mar, 2012 4:49 am    Post subject:         Reply with quote

Wasn't that the Atl-Atl slung javelins rather than sling stones getting the supposed plate penetration?
"The Dwarf sees farther than the Giant when he has the giant's shoulder to mount on" -Coleridge
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Randall Moffett




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PostPosted: Wed 28 Mar, 2012 5:56 am    Post subject:         Reply with quote

Ben,

That is interesting. That said I have never seen large numbers of slingers sent to the americas. By and large until the 1530s the majority of missile troops were crossbowmen.

I agree with Dan. Almost all the evidence I have seen puts slings in the hands of what are usually deemed less effective troops. IN late medieval England for example a few towns field slingers from women and children for the towns defense clearly because they were more archers, men at arms, armed men, etc.

RPM
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Benjamin H. Abbott




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PostPosted: Wed 28 Mar, 2012 7:57 am    Post subject:         Reply with quote

Randall Moffett wrote:
Ben,

That is interesting. That said I have never seen large numbers of slingers sent to the americas. By and large until the 1530s the majority of missile troops were crossbowmen.


I was referring to the sling in the hands of the Spaniards' Amerindian opponents. And it was the atlatl that Bernal Diaz wrote could penetrate any armor. As far as kinetic energy goes, the atlatl is an interesting case. One test produced figures up to 770 J, with an average of 200-350 J with the heavier darts. However, some enthusiasts dispute these numbers because they can only manage 43 J. So atlatls hit considerably harder than bows or significantly weaker, depending on who you believe. To be fair, there is one middle ground study that got 72-110 J.

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Jojo Zerach





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PostPosted: Wed 28 Mar, 2012 9:37 am    Post subject:         Reply with quote

I think this whole notion of "X amount of joules are needed to penetrate X armour" is entirely unrealistic.
Reality doesn't work like a points system in a video game.
I could heft a large rock and generate as much energy as many types of bullets, but that doesn't mean my rock would be as lethal, or have anywhere near the penetration, of the bullets.
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Bartek Strojek




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PostPosted: Wed 28 Mar, 2012 10:17 am    Post subject:         Reply with quote

Obviously, if you the same given arrow though, you can pretty much roughly compare it's effects at different energy right before the impact.

Differences between particular arrows/armors will cause problems, but still some rough estimations will be alright, I guess..

Anyway, those 700 and 300 J with atlatls seems straight out unrealistic to me....

http://paleoplanet69529.yuku.com/topic/26013/...3NECOXow_4


With light ~ 55g dart, distance is 'only' 230m.... Even considering heavy, more than 5 ounces dart, velocity would have to be in regions of 100 m/s to approach 700 Joules.

That just not compute both with data I can find and with the observatgion that darts don't travel nearly as fast as arrows, while quicker than hand thrown javelins, obviously. While they're lighter than javelins, and heavier than arrows. Some middle ground between them, I guess. Wink

http://www.worldatlatl.org/Articles/TakochCD/...evised.pdf
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Mackenzie Cosens




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PostPosted: Wed 28 Mar, 2012 3:00 pm    Post subject:         Reply with quote

There is an interesting discussion on what is better heavy or light arrow at http://www.physicsforums.com/archive/index.php/t-195119.html is somewhat related to this topic.
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Timo Nieminen




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PostPosted: Wed 28 Mar, 2012 9:04 pm    Post subject:         Reply with quote

Not so relevant, since that focusses on depth of penetration into soft tissue, and not penetration of armour plate. The short answer is that penetration into soft tissue depends on momentum, and penetration of armour plate depends on energy (if we can ignore the various other factors which limit the applicability of this, as discussed above).

A lot of war arrows tend to be heavy: 90g for European longbow, 100g for Manchu, over 100g for Japanese. This is to get more energy - out of the same bow, a heavier arrow will get more energy. This sacrifices range and accuracy.

However, it's thought that one of the evolutionary pressures on the Manchu bow was big game hunting (in Manchuria, before the Manchu conquest of China). The heavy Manchu arrows will have given better penetration into large game (like tigers and bears). This will also, with a high draw weight bow, give lots of energy, which will be good for armour penetration. Win + win!

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Benjamin H. Abbott




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PostPosted: Wed 28 Mar, 2012 9:24 pm    Post subject:         Reply with quote

Given that the best javelin-throwers unquestionably manage to impart as much as 360 J into their missiles, the 350 J figure from the Hutchings atlatl test makes sense. While the atlatl uses lighter darts, it also provides mechanical advantage. If we accept other tests as the limit of atlatl power, the accounts of Bernal Diaz, Garcilaso de la Vega, and company become incoherent. At Whittaker's 43 J, the atlatl seems strictly unsuitable for war. Few if any military bows dipped below 80lbs, and any decent 80lb bow should impart at least 50 J.

As far as arrow weights go, the textual English evidence suggests four ounces (113 g) as a common number. I'm intrigued by the weight of Japanese arrows, because I've encountered various scholars and enthusiasts alike that dismiss the Japanese bow as weak and inferior to continental Asian designs.

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Timo Nieminen




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PostPosted: Thu 29 Mar, 2012 12:39 am    Post subject:         Reply with quote

Japanese archery sportified in the 1600s. (Hurst's Armed Martial Arts of Japan discusses this.) Arrows became lighter, bows became weaker (and lighter, so fast) - fast light arrows are good for target shooting, or for "clearing the hall" (getting arrows to the end of a covered verandah without hitting ceiling or floor). "Clearing the hall" records stand at over 8000 arrows within 24 hours (over 13000 arrows shot to achieve the top score), so lower draw weight bows were rather useful. Lighter arrows were good for more speed for more range.

But Japanese warbows were high draw weight, and are pretty optimised for energy at the expense of accuracy. I haven't see a good figure for weight of Japanese war arrows, but I'd guess that most of them were over 100g, possibly well over. Judging Japanese military archery on the basis of mid to late Edo period archery would be like judging Medieval and Renaissance English archery on the basis of Victorian archery.

Compared to continental Asian designs, the Korean/Ming/Mongol bow is lighter and more efficient, and will put a lighter arrow (the Turkish and Indian bows are similar, and then we'd be talking 20-40g arrows) a lot further. The Japanese bow will lack range in comparison, but should exceed the light continental bows in energy (mainly due to a longer draw). Archery duels with Mongol armies (i.e., mostly Chinese and Korean soldiers) will not end well if the Mongols choose the range.

Compared to the Manchu bow, it's probably about even. The Manchu bow, for the same draw length and draw weight, should give more energy. The Japanese bow is cheaper to make.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Mackenzie Cosens




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PostPosted: Thu 29 Mar, 2012 11:35 am    Post subject:         Reply with quote

This one of the quotes that I think has reliance:

Quote:
Second of all, let me point out that the geometry of a projectile may be very important to penetration performance at subsonic velocities. You didn't mention this in your post, but I think you ought to keep it in mind. It is quite possible that the KE or momentum measurement is a moot point, when the geometry of the projectile may in fact be the dominant factor. So, we will also assume that the geometry is "good enough". In other words, the geometry is optimized for best performance, at all weights.


So looking at a single projectile comparing KE is just fine, but when you look across projectiles the situation may be more complex. Of course knowing how much energy you can produce with a particular weapon system is a good place to start.
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