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SteveL
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PostSubject: Bulletproof vests   Tue Jan 27, 2009 6:29 pm

Can a bullet that does not penetrate a bulletproof vest (made of Kevlar or other pliable material) cause serious or significant injury?
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kubera

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PostSubject: most certainly   Tue Jan 27, 2009 8:30 pm

kevlar spreads the force of the bullet to a wider footprint and stops penetration(so long as its not a cop killer bullet designed to pierce kevlar)

a great deal of the kinetic energy however is still directed inward and a test I saw on myth busters (i believe) showed a 6 inch wide 3 inch deap dent in a clay model of a body. The impact alone from a bullet can break ribs, cause internal bleeding and at the very least deep bruising akin to a baseball bat to the area. People do die from non penetrating gun shots wearing kelvar. There are however 4 or 5 levels of kelvar protection up to the ones with additional ceramic plates that can stop dead 1 shot before they shatter. They are rated by the range of calibers they stop but some rounds that are pointed and steel jacketed or teflon coated can still defeat kevlar.

this wiki http://en.wikipedia.org/wiki/Bulletproof_vests
appears to be accurate as far as my meagre knowledge can discern
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Kevlar soft armor had its shortcomings because if "large fragments or high velocity bullets hit the vest, the energy could cause life-threatening, blunt trauma injuries" in selected, vital areas.
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PostSubject: Re: Bulletproof vests   Tue Jan 27, 2009 9:09 pm

[mrburns]Excellent.[/mrburns]

I wanted to verify that an arrow can kill even if it doesn't penetrate pliable armour like mail.
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PostSubject: well I don't know   Tue Jan 27, 2009 9:27 pm

I'd like to see the comparative numbers for impact strength between a military bullet and a arrow before I jumped to any conclusions,

erg vs erg

chain is also a hybrid of both flexible force dispersing armour and rigidity of the iron links, as well as having a padding underneath.

Unlike Bullets I do not know what actually happens in a strike. However kelvar defeating pointed bullets are barely inconvinienced by the presence of kevlar , similar to how I think chain would react in the case of bodkin type arrow heads which are narrow enought hit less rings on impact.

I just don't know!
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PostSubject: Re: Bulletproof vests   Tue Jan 27, 2009 10:01 pm

kubera wrote:
I'd like to see the comparative numbers for impact strength between a military bullet and a arrow before I jumped to any conclusions,

erg vs erg

chain is also a hybrid of both flexible force dispersing armour and rigidity of the iron links, as well as having a padding underneath.

Unlike Bullets I do not know what actually happens in a strike. However kelvar defeating pointed bullets are barely inconvinienced by the presence of kevlar , similar to how I think chain would react in the case of bodkin type arrow heads which are narrow enought hit less rings on impact.

I just don't know!
It's easy to delve into these issues, but the challenge is to represent as much reality as possible in as playable a manner as possible.

For example, a piece of armour has an Armor Rating (AR); e.g., a mail hauberk is, I think, 4. (An unarmored man has an AR of 0, a plate breastplate is 6 or thereabouts.) AR reduces damage in a straightforward way (e.g., an AR of 2 subtracts 2 damage). I was thinking of adding PR (Penetration Resistance); e.g., a Kevlar vest would have a low AR and a high PR. Remember my idea for instant kill puncture attacks? Now I'm thinking of adopting the GURPS idea of multiplying the damage of impaling weapons by 2 but only for the damage that exceeds PR.

Example: if AR is 2 and PR is 4 (perhaps thick hide), 11 points from a mace would be reduced by AR to 9. Because a mace can't impale, the inflicted damage is 9.

But now imagine the same damage delivered by an arrow. As before, AR would reduce this to 9. Of this remaining 9, 5 penetrates (i.e., 9 minus the PR of 4). The non-penetrating damage is "blunt" or "crushing". Thus, damage sustained is 14 (4 "blunt" + double the 5 that penetrates = 14).

Too much to calculate? Perhaps. But GURPS seems to be much more math intensive than this, and we're not idiots.

Imagine an unarmoured man hit by an arrow for 11 points. Since he has no AR or PR, all the damage is considered to have penetrated him, so he would sustain 22 points.

Finally, imagine a man wearing a Kevlar vest (say, AR 1, PR 10) taking the same arrow. The 11 is reduced by AR to 10, but the arrow does not penetrate. Thus, the man takes 10 damage. This damage is kinetic (blunt or crushing); my original post here was to determine the plausibility of this very outcome.
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PostSubject: Re: Bulletproof vests   Wed Jan 28, 2009 1:50 am

I don't know how this will affect your ideas, but I remember Hoppy putting a knife through his Kevlar vest with no difficulty at all (it went in to Harrison's dining room table!). I would think that an arrow with a thin pointed head would be affected much less than one with a broad pointed head when dealing with chainmail.
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PostSubject: Re: Bulletproof vests   Wed Jan 28, 2009 12:23 pm

kubera wrote:
I'd like to see the comparative numbers for impact strength between a military bullet and a arrow before I jumped to any conclusions,

erg vs erg


Kinetic Energy (KE) = 1/2 MV2

safe to say that bullets are much more powerful. 250 fps versus 600 to 5000 fps. i'd say that even with the higher weight of an arrow the power of a bullet is easily an order of magnitude higher. Note too that for lower muzzle velocity (eg 600fps for a .38 special) soft kevlar vests are quite effective.
see this for lots of interesting (and some disturbing) info...has interesting explaination of where damage comes from at different velocities

and look at this one too as an example of bow arrow kinetic energy there is also some information about penetration etc. and links to some crazy stuff too
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PostSubject: Re: Bulletproof vests   Fri Feb 20, 2009 3:44 pm

Jonathan wrote:
I don't know how this will affect your ideas, but I remember Hoppy putting a knife through his Kevlar vest with no difficulty at all (it went in to Harrison's dining room table!). I would think that an arrow with a thin pointed head would be affected much less than one with a broad pointed head when dealing with chainmail.
I remember that incident. At first he was going to allow us to stab the vest while he wore it. It's a good thing we convinced him of the danger.

True, mail is less resistant to impaling weapons than to edged weapons. I have simplified this by providing each armor type with a PR (penetration resistance) rating, which is a catch-all value to include edged and puncture weapons. I don't think this is terribly unrealistic. I can always separate PR into IR (impale resistance) and ER (edged resistance).
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PostSubject: Re: Bulletproof vests   Fri Sep 04, 2009 3:59 pm

jeez i rememeber that too! The look on Hoppy's face when he realized the truth was priceless. Laughing
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PostSubject: Re: Bulletproof vests   Fri Sep 04, 2009 5:56 pm

Didn't see this topic before...



The arrow goes much slower yet with greater mass, but it's working surface, the sharpened edge, is much smaller, so per unit of area, it applies more force. Also steel is hard, lead is soft. Some of the energy of a firearm is redirected to deforming the lead, which makes it less likely that it will immediately start pushing the fibers aside.

Bullets smash through (or try anyways), arrows slice through.

Note, however, that dull 'practice point' arrows will fail to penetrate armor that a broadhead will cut right through.

The above applies to knives as well. If you can cut the fibers with scissors, an arrow or knife will cut them as well. Kevlar is tough on scissors but it can be cut - you can also open up the weave if the point of the weapon gets through.
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PostSubject: Re: Bulletproof vests   Mon Jun 15, 2015 8:48 pm

Interesting question.
38 special 158 grain, 885fps muzzle, 256ft-lbs
High tech modern bow: 450grain, 347 fps, 120ft-lbs
Speed o sound: 170grain, 1127fps, 480ft-lbs
223 varmint: 80 grain, 2500fps, 1110ft-lbs
30-06: 150 grain, 2970fps, 2937ft-lbs
30oz Baseball bat: 13125grain, 88fps, 225ft-lbs

Probably more interesting is that this comparison has become almost trivial (due to web information availability) in so short a time.
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PostSubject: Re: Bulletproof vests   Mon Jun 15, 2015 9:07 pm

Actually I'm amazed at how light a modern arrow must be, I was expecting the ft lbs to be higher because I expected the weight to be several times higher

So I guess this would preclude death from a non piercing arrow unless you get damn lucky and collapse a larynx, hit the base of head, side of temple , or rupture someone's balls, they may not die immediately but they'll probably kill themselves in the near future.

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PostSubject: Re: Bulletproof vests   Tue Jun 16, 2015 8:37 am

The arrow example is from a high tech modern hunting setup. And it looks like 347fps is near to the limit for a compound bow that someone could actually draw. Olden time arrows were likely much heavier, but "muzzle velocity" would be much lower...most of the stuff I saw pegged long now velocity around 200fps, and since velocity is a second order term (compared to first order weight); a 4 or 5 oz arrow wouldn't yield a significantly higher energy at realistic historic speed.
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