Weapons versus plate armour -- myArmoury.com

Timo Nieminen · Posted: Sat 24 Mar, 2012 3:43 pm Post subject: Weapons versus plate armour

How much energy is required to penetrate plate armour?

From "The Knight and the Blast Furnace", we have for mild steel (0.15% carbon), hitting straight on (at normal incidence, rather than a glancing blow), the following energies (in joules) required for penetration:

Thickness Arrow Bullet
1mm 55J 450J
2mm 175J 750J
3mm 300J 1700J
4mm 475J 3400J

Historical armours would have had higher slag content, and could have been substantially weaker. The best armours were hardened steel, so stronger. For different irons/steels, you can multiply these energies by:

Munition quality iron: 0.5
Low-carbon steel: 0.75
Medium-carbon steel (Milanese): 1.1
Hardened steel: 1.5

Add to these energies about 50J to defeat padding (e.g., 16 layers of linen), and perhaps 50J to actually cause serious injury or death. (Williams uses slightly higher values, for a total of 150J after the plate is penetrated.)

So, 1mm low-carbon steel plate + padding needs arrows with about 120J to defeat armour and wearer, 2mm plate needs about 230J, 3mm plate 325J.

Also from Williams, an arrow with 120J could penetrate mail (real 15th century mail) and padded jack. So, to defeat armour and wearer, 170J.

So 1mm plate looks inferior to mail, and 2mm plate much better. If you want to stop close-range archery with mail, use heavier mail and/or more/better padding than in Williams' test. Lamellar of about 1.2mm looks comparable to mail.

So, we can assume that 2-3mm plate is good against most archery, including most crossbows. Not adequate against the better firearms (1500J should be defeating 3mm low-carbon steel plate, 1000J for 3mm iron); a pistol or carbine would give about 1000J, arquebus 1200-2000J, muskets 2-3000J.

Soft armours require about 100J to defeat with a blade (or more, if thicker, 100-180J to defeat 5-26 layers of linen). This is more than needed by an arrow; the arrow is better at making holes for the same energy. Good mail and plate will be cut-proof - about 200J to defeat mail with an edged weapon, more against plate. More than most people will manage, but possible. Williams has 60-130J for approximate energy of sword and axe.

This gives a good base for estimating the effectiveness of armour against archery and firearms: 2-3mm low-carbon steel plate to stop archery, 8-9mm of iron to stop short-range musketry.

For sword and axe, mail + padding is good, or the thicker jacks. Of course, also plate (unless possibly the very thinnest and worst?).

What about other armour-piercing weapons?

Javelins might reach 250-300J, and might defeat arrow-proof armour. From literature, we know javelins are good against armour (Roman sources praising the pilum for penetration, though to Conquistadors noting the effectiveness of javelins).

From home experimentation, polearms can be effective. Long hafts allow a lot of energy to be delivered. How much? This could be estimated from high-speed video, from which the speed of the head of the weapon can be measured, and with the mass of the head, gives the kinetic energy of the head. It might be possible to obtain a reasonable estimate using a ballistic pendulum (this would give the momentum of the weapon, but from this, the kinetic energy can be found). I don't have any numbers for polearm energies, and can't find any. Does anybody have anything that might be of use? Anybody willing to try making a measurement? If the energy exceeds 200J, then they should be a good weapon against light armour (mail, thin plate).

Maces and other blunt weapons are highly-praised for anti-armour effectiveness. I don't think we can say much about these on the basis of energy required to penetrate armour, since they don't penetrate the armour.

Benjamin H. Abbott · Posted: Sat 24 Mar, 2012 7:14 pm Post subject:

Where are you getting the notion that you add an additional 50 J to Williams' figures to defeat the wearer? My understanding is that's already assumed in the tests. At 120 J, mail fails enough to allow potentially fatal penetration. You certainly don't need 50 J to pierce skin and flesh with a pointed weapon; sharp points can do that with a mere 1-3 J. If it took 170 J to kill through mail with an arrow, this would have hardly ever happened. Only a heavy yew warbow with a heavy arrow would manage so much as 150 J as close range.

As far as kinetic energy figures for close-range weapons go, I haven't found much concrete. Modern measures of the underarm thrust with knife peak at 72 J, while overarm gets up to 115 J. Most folks can only manage 20-30 J, or even less, which further refutes the notion that you 50 J to inflict a serious injury. A test of a two-foot stone mace, presumably wielded in one hand, produce the result of 130 J. Baseball bats and golf clubs seem to deliver 200-400 J in the hands of professional athletes. As such, I think Williams underestimates the kinetic energy of swung weapons. I imagine simple single-handed sword thrusts from experienced warriors/soldiers would be 60-80 J at the least because swords weight more than knives and the person to got 72 J wasn't a giant or anything.

Dan Howard · Posted: Sat 24 Mar, 2012 7:39 pm Post subject:

Williams defined plate failure as penetration by 40mm or more (p. 929).

Timo Nieminen · Posted: Sat 24 Mar, 2012 8:44 pm Post subject:

Benjamin H. Abbott · Posted: Sun 25 Mar, 2012 11:58 am Post subject:

Various strange inconsistencies appear throughout The Knight and the Blast Furnace. The additional 100 J doesn't appear in most of his examples. See the pikeman on 947, for instance. On page 943, he notes that at 120 J, the arrowhead put a 35mm dent in the plastilene behind the modern mail and jack. How tough is plastilene? Even if it's only as resistant as human skin and flesh, 1.4 inches of penetration in the right spot could be fatal.

Dan Howard · Posted: Sun 25 Mar, 2012 1:10 pm Post subject:

Ahmad Tabari · Posted: Sun 25 Mar, 2012 3:14 pm Post subject:

Just out of curiosity, does anyone know the ring measurements of the 15th century mail Williams tested? I am asking because I have seen a great amount of variation in 14th and 15th century mail. Some is very light and clearly designed to be worn under some form of plate armour, while others seem to be heavy enough to be used as standalone armour.

Dan Howard · Posted: Sun 25 Mar, 2012 3:37 pm Post subject:

IIRC one of the test pieces was a 15th C voider and the other was a replica made by Erik but I don't have any other details.

Ahmad Tabari · Posted: Sun 25 Mar, 2012 3:48 pm Post subject:

Oh I see. I think the test would have done much more justice to mail had he used a replica patch of a 14th century hauberk such as the one in the Cleveland museum. With the exception of the groin area, most voiders covered non vital areas of the human body and so I would imagine they would have had lighter rings than those used to cover the chest in a hauberk.

Dan Howard · Posted: Sun 25 Mar, 2012 5:13 pm Post subject:

The armpit is definitely a vital area. A wound here can sever the brachial or subclavian arteries and the nerves controlling the arm before puncturing the lungs and the heart.

Benjamin H. Abbott · Posted: Sun 25 Mar, 2012 8:07 pm Post subject:

Just the muddy the waters, I'll mention the rather high energy figures one finds for the simple punch. Rocky Marciano supposedly managed 1,254 J. I don't know what to make of such accounts. As an aside, the kinetic energy of a guillotine blade has been calculated at 300 J. So that's an upper limit for reliable decapitation.

Kel Rekuta · Posted: Sun 25 Mar, 2012 11:04 pm Post subject:

Kel Rekuta · Posted: Sun 25 Mar, 2012 11:08 pm Post subject:

Timo Nieminen · Posted: Mon 26 Mar, 2012 2:24 am Post subject:

Benjamin H. Abbott · Posted: Mon 26 Mar, 2012 7:49 am Post subject:

Bartek Strojek · Posted: Mon 26 Mar, 2012 8:16 am Post subject:

Benjamin H. Abbott · Posted: Mon 26 Mar, 2012 9:53 am Post subject:

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. The sling figure of 21.7 J, for example, strikes me as laughable. The best baseball pitchers can impart over 150 J without any mechanical aid. If ancient slingers only achieved 21.7 J, they'd hardly have hurt anybody, much less performed the feats attributed to them. Calculations based on contemporary distance records suggest a kinetic energy of up to 400 J with heavy projectiles, which makes far more sense. The From Sumer to Rome test assigns nearly the same kinetic energy (137 J) to gladius swing and stone mace blow despite the wildly different balance on the mace. They conclude that the 1.8lb mace could not knock someone out through a helmet and note its decline as a military weapon in ancient armies. Maybe, but if that's the case, then later maces must have performed much better. We have various accounts to indicate that 15th- and 16th-century cavalry maces could induce unconsciousness through a helmet. It's important to remember that hand weapons don't generate kinetic energy, people do. I have a feeling we should double (or triple, quadruple, etc) the numbers from most tests of modern folks. After all, most archers these days draw 50-60lb bows, while military archers drew 100-180lbs.

Jojo Zerach · Posted: Mon 26 Mar, 2012 12:04 pm Post subject:

Mackenzie Cosens · Posted: Mon 26 Mar, 2012 12:44 pm Post subject:

Some numbers for punches and the like:

Gary Teuscher · Posted: Mon 26 Mar, 2012 12:53 pm Post subject:

Really what is probably needed is the amount of joulles needed for multiple weapons vs multiple types of armour.

I.E. Sword cut, axe chop, spear thrust, dagger thrust, sword thrust etc.