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Old 03-23-2016, 11:10 PM   #1
Michael Thayne
 
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Default Why isn't better limb armor available at TL8?

I've been playing around with the cutting-edge armor design rules from Pyramid #3/85, and the results are a bit surprising. A full suit of kevlar, thick enough to provide DR 12 and made without any weak points, should weigh 26 lbs. Heavy–but not outrageous compared to historical low-tech armor. And this is for armor made from one of the less-advanced ballistic materials available. Using "improved kevlar" reduces the weight by 20%, "ballistic polymer" by 40%, and "improved ballistic polymer" by 60%, down to 10 lbs., only slightly more than TL9 reflex armor.

I raised the question of whether this was realistic a few days ago, and the consensus seemed to be yes, though maybe "improved ballistic polymer" is speculation about what might be possible in the near-future. I've spent some time reading online about limb armor that the US government tried issuing to vehicle crews a few years ago. Supposedly it was made out of what Pyramid calls "ballistic polymer", added about 10 lbs. to a soldier's loadout, and was almost as effective as a soft bulletproof vest. From what I can tell, this is 100% consistent with the cutting-edge armor design article.

However, I get the sense that this limb armor wasn't very popular among soldiers–many complained it restricted mobility too much. A few hypotheses about why this might be:

1) Pre-firearms armor restricted mobility just as much, but firearms have changed what people consider an acceptable loss of mobility.
2) Kevlar and similar technologies have a high strength per weight, but less impressive strength per unit of thickness (since they're less dense than steel). Furthermore, their bulkiness is a much bigger problem for limb armor than it is for torso armor.
3) The pictures I've seen of real ballistic limb armor make it seem almost absurdly bulky. This fits with (2), except from what I understand bulletproof vests aren't that thick. Maybe the issue is that the military wants a couple sizes to fit all soldiers, whereas good-quality pre-firearms armor was tailored to the user? So maybe existing ballistic limb armor (along with bomb disposal suits) should be modeled as giving -1 to DX, but in principle custom-fitted armor ballistic limb armor could restrict mobility much less.

Which of these three explanations is correct? Or is it some combination? (3) would suggest interesting possibilities for what should count as realistic for Batman-style superhero armor.
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Old 03-24-2016, 12:49 AM   #2
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Default Re: Why isn't better limb armor available at TL8?

You can get some military limb armour (the DAP and ballistic leggings in HT) its just you don't tend to see it very often, it mainly being used in specific situations like close up assaults and stuff (I'm guessing SWAT teams are fans of it as well). I'm guessing up armoured elbow pads and are likely a thing to. I'd also recommend Pyramid 3-57 "gunplay" if you don't already have it, it talks about modern load outs a bit.

Contrast that to TL9 combat load outs in Pyramid 3-55, the cutting edge article is straddling these and even with a TL there is development etc.


However in terms of what your talking about I think it's ultimately a combination of

1). limb armour is tricky and fiddly to get right and keep mobility and use of the limbs.

2). Torso armour compared to limb armour saves your life (and while RPGs obsess about DR and exact reductions in damage, in RL "does this save you life" is really the key criteria in most trade offs). Which is why even torso armour didnt become a widespread thing again until it could reliably stop an assault rifle.

3). Those lovely new materials that make high DR limb armour more likely are just that new. Military procurement is slow. Give it 10-20 years and yep maybe high DR flexible limb armour will be ubiquitous for armies with the money to armour their troops full stop.

4). Armour in general is coming back on the scene after a period of it widely being seen as "not worth it" (not worth it being a combination of several factors some of which are not just about protection). Again these new materials may change that expanding its role and with that acceptable options

5). Load outs are constantly increasing, there a huge amount of time and resources being devoted to finding anyway of bringing it down, so any extra weight is a problem.


6). Kevlar Limb armour does exist, it just you see it more in riot police etc who are more likely to get into hand to hand combat, and less likely to be facing high velocity rounds. Or carrying around a full pack).

Last edited by Tomsdad; 03-24-2016 at 01:27 AM.
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Old 03-24-2016, 01:09 AM   #3
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Default Re: Why isn't better limb armor available at TL8?

It actually makes perfect sense to me that ballistic fabric might make for less comfortably flexible joints than articulated plate or mail. Even fabrics that aren't meant to stop gunfire are often not really much good at doing joints.
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Old 03-24-2016, 01:25 AM   #4
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Default Re: Why isn't better limb armor available at TL8?

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Originally Posted by Ulzgoroth View Post
It actually makes perfect sense to me that ballistic fabric might make for less comfortably flexible joints than articulated plate or mail. Even fabrics that aren't meant to stop gunfire are often not really much good at doing joints.
Its true. historically limb armour was basically high end bespoke tailoring with all the extra issue of useful protection on top. Now modern manufacture and design is going to to go some way to alleviate that, but only so far.

I'm guessing voiders of thinner more supple material in the inside joint, more rigid elbow and knee pads for the exterior joints.

But yes as you say I'm guessing there only so much you can do there will be some trade off here.
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Old 03-24-2016, 02:36 AM   #5
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Default Re: Why isn't better limb armor available at TL8?

As is usual for GURPS armor figures, the weights are grossly underestimated. Modern level IIIa body armor (Dyneema, typically) is around 1.1 lb/sf areal density, or around 22 lb for full coverage (listed armor stats are generally for armor that covers 25-50% of the torso).
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Old 03-24-2016, 02:53 AM   #6
Rupert
 
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Default Re: Why isn't better limb armor available at TL8?

Quote:
Originally Posted by Michael Thayne View Post
1) Pre-firearms armor restricted mobility just as much, but firearms have changed what people consider an acceptable loss of mobility.
2) Kevlar and similar technologies have a high strength per weight, but less impressive strength per unit of thickness (since they're less dense than steel). Furthermore, their bulkiness is a much bigger problem for limb armor than it is for torso armor.
3) The pictures I've seen of real ballistic limb armor make it seem almost absurdly bulky. This fits with (2), except from what I understand bulletproof vests aren't that thick. Maybe the issue is that the military wants a couple sizes to fit all soldiers, whereas good-quality pre-firearms armor was tailored to the user? So maybe existing ballistic limb armor (along with bomb disposal suits) should be modeled as giving -1 to DX, but in principle custom-fitted armor ballistic limb armor could restrict mobility much less.

Which of these three explanations is correct? Or is it some combination? (3) would suggest interesting possibilities for what should count as realistic for Batman-style superhero armor.
It's a combination - bulkiness is a real problem, and weight on limbs tires you disproportionally fist compared to body (and even head) armour. It also slows your arm and leg movements down, so you run slower and bring your weapon to bear more slowly.

As for why this was acceptable to the wealthy and some others in pre-industrial times - they often rode everywhere, didn't wear their full harness outside of battles, and their battles were relatively short affairs. They also didn't carry a whole pile of kit into battle.

Today the people who most need all that armour, aside from the EOD types who have it already, (infantry) walk a lot, with lots of gear. They can't predict when they'll need the armour, so they have to wear it all the time, and in many cases are too far from a base or vehicle to be able to simply put it on when the party starts anyway.

So, currently the main reason is that most of the people who need it, can't carry it.

I expect it see it on SWAT teams before I see it in general infantry issue. The other types who'll have it will be teams in specific assault situations where they can gear up just before a short assault - the military equivalent of a SWAT's assault. I don't think specops units will wear it in general, as they rely on surprise and speed, and will want to keep their mobility.

Obviously if it gets to the point where we can make 'bullet-proof' jeans every soldier will have a 'bullet-proof' uniform (and the issue weapons will not fire bullets that uniforms stop) until nobody uses normal guns on the battlefield any more.
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Old 03-24-2016, 02:56 AM   #7
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Default Re: Why isn't better limb armor available at TL8?

Quote:
Originally Posted by Tomsdad View Post
Its true. historically limb armour was basically high end bespoke tailoring with all the extra issue of useful protection on top. Now modern manufacture and design is going to to go some way to alleviate that, but only so far.
A fair number of armoured vests over the years were designed by people who fairly obviously could've done with some time studying old breastplates, mail shirts, and quilted armour jackets to see how to make armour actually fit and be wearable.
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Old 03-24-2016, 04:28 AM   #8
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Default Re: Why isn't better limb armor available at TL8?

Quote:
Originally Posted by Rupert View Post
A fair number of armoured vests over the years were designed by people who fairly obviously could've done with some time studying old breastplates, mail shirts, and quilted armour jackets to see how to make armour actually fit and be wearable.
The more you move away from the direct one on one artisan relationship between armourer and armour wearer (and armour wearer's purse). And move towards some one in a procurement office buying x0,000 units with a budget that has gone through it's own process as well a supplier selection process, your going to tend "towards one size fits all",

And to be fair it's not just a modern thing (IIRC it was an issue for the legions for example)
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Old 03-24-2016, 04:30 AM   #9
Peter Knutsen
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Default Re: Why isn't better limb armor available at TL8?

Quote:
Originally Posted by Rupert View Post
A fair number of armoured vests over the years were designed by people who fairly obviously could've done with some time studying old breastplates, mail shirts, and quilted armour jackets to see how to make armour actually fit and be wearable.
Wouldn't trying to make the armour fit better and be more wearable result in a more expensive manufacturing process?

Also, medieval plate armour was tailored to the wearer, when it first got introduced (fairly late in the medieval period). Later you got mass-produced stuff that fitted worse.
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Old 03-24-2016, 06:38 AM   #10
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Default Re: Why isn't better limb armor available at TL8?

Assuming the limb armor you're talking about covers the entirety of the arms and legs and is made of optimized fabric, 10 lb Dyneema gets you DR 20 and is nearly half an inch thick, meaning it's no longer GURPS Flexible. So, some loss of mobility isn't entirely unlikely there. Another issue, which GURPS doesn't cover, is that weight carried on the torso (as torso armor, in a pack, etc) doesn't "feel" as heavy as weight carried on the arms and, especially, the legs. A lack of tailoring to fit the individual soldier may indeed also factor in.

All of these taken together, combined with the fact that soldiers are going to be wearing such armor over fairly long patrols, means using it is going to be rather uncomfortable. This may be under GURPS resolution, just like getting hit in the face with a weak punch, but in real life it is going to cause soldiers to complain and likely opt to simply forgo such armor.
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