Realistic DR for rigid armor

[DouglasCole]

Originally Posted by Gustavus Adolphus

Well, in current linear DR increment rules, the TL3 iron is more resistant than RHA steel.

2,54 cm of RHA steel = DR 70
2 mm of TL3 iron (medium plate) = DR 6; 2,54 cm of TL3 iron = DR 76.2
A TL3 medium plate armor for a colossal fantasy titan is more resistant than tank RHA covering, according to GURPS rules.

RHA is not great armor, never has been. It's a test medium whose primary property is that it's homogeneous, not that it's good protection. High Hardness Armor (HHA) and other optimized systems are much better.

[malloyd]

Originally Posted by DouglasCole

RHA is not great armor, never has been. It's a test medium whose primary property is that it's homogeneous, not that it's good protection. High Hardness Armor (HHA) and other optimized systems are much better.

The other huge factor for comparing rectangular blocks of stuff to armor for people is that thin sheets of stuff can vary hugely in the amount of stress they can resist without seriously deforming depending on how they are shaped. Bend a piece of paper. Now put a crease in it and try to bend it again. This makes comparing statistics of an inch of anything to a shaped thin plate of the same stuff pretty much useless.

[Polydamas]

Originally Posted by Gustavus Adolphus

Actually, if you use Mosteller formula to calculate body surface area, a DR 6 20 lb breastplate made of iron for a standard-sized man (1.72 m x 70 kg) is exactly 2 mm thick. Iron, not steel, steel armor has an extra +1 DR.

The formula which Dan Howard used is that a very light cuirass and fauld is about 1 mm thick and weighs 8 lbs, and each +0.5 mm adds +1 DR. Medium plate represents armour with an average thickness of 2.5 mm, although in practice it will be more like 3 mm over the most important spots and 2 mm over the ones which are least likely to be struck. The DR allows for clothing and light padding underneath, and for curved armour being stronger than a flat plate. Be careful about those assumptions ...

Originally Posted by Gustavus Adolphus

@Polydamas: strangely, I find more accurate the melee damage, at least until ST 16, the human ST limit (extremely rare but possible, ex. the GoT character "The Mountain").

What do you mean by “more accurate”? How do you know?

[Anthony]

Originally Posted by DouglasCole

RHA is not great armor, never has been.

It's not great armor, but it's still TL 6 armor steel, it's better than anything producible in bulk at TL 5- and should be superior to TL 3 wrought iron, though it's reasonable for TL 4 hardened steel to outperform it at much higher prices.

[Gustavus Adolphus]

Varyon

I realize now I misunderstood what the Construction Weight Modifier for Plate really represents - it's for the angling of the armor to reduce the chance of a blow "biting," as well as weight reductions in areas that aren't considered very vulnerable (Chinks in Armor and Armor Gaps). A 20 lb iron breastplate that was 2 mm thick would lack such modifications and thus wouldn't have weak points, but would be more-or-less impossible to construct for the human form. Such a theoretical breastplate would use the Solid (rather than Plate) construction, and would provide DR 4.76 (which we could be kind and round up to 5). As it stands, a 20 lb Plate breastplate is going to be mostly around 2.25 mm thick (it can probably get away with being a bit thinner, thanks to angling tricks), but with some thinner areas (Chinks in Armor) and outright gaps making up the difference.

Already considered in my formula as "Form Factor": flat surface armor has x0.833 DR (lorica segmentata or asian mirror armor, and they have more gaps) and fluted surface armor x1.166 DR. It's impossible a weight of only 20 lb for a cuirass of 2.25 mm, considering the fact that the armor's total surface is a bit major than the flesh surface that the armor covers.

Anthony

It's not*great*armor, but it's still TL 6 armor steel, it's better than anything producible in bulk at TL 5- and should be superior to TL 3 wrought iron, though it's reasonable for TL 4 hardened steel to outperform it at much higher prices.

Not exactly, in fact you can do high-quality steel THIN armors (up to 2 mm thick for "superior quality steel" with W 1.5, and up to 3.25 mm for good steel with W 1.1) in middle TL4 Europe. But with TL2-4 methods, you can't produce thick quality steel (thicker than 4mm), because the steel loses quickly his quality and worsened, becaming comparable to high-scories content steeled iron.

Polydamas

The formula which Dan Howard used is that a very light cuirass and fauld is about 1 mm thick and weighs 8 lbs, and each +0.5 mm adds +1 DR. Medium plate represents armour with an average thickness of 2.5 mm, although in practice it will be more like 3 mm over the most important spots and 2 mm over the ones which are least likely to be struck. The DR allows for clothing and light padding underneath, and for curved armour being stronger than a flat plate. Be careful about those assumptions...

It's impossible a weight of only 8 lbs for a 1 mm complete torso cuirass.
Using Mosteller formula, the total area surface of a 1.72 m x 70 kg man is 1.83 m². The torso covers (following GURPS rules) almost the 31,25% of body surface, in this case 0.572 m² circa. Specific weight of steel is 7.8 kg/dm³ and the armor is 1 mm thick, so the weight of the 1 mm thick cuirass is 9.9 lbs (circa, a little of weight is lost on armpit's gaps but a little more is added because the rounded surface for deflect hits who isn't adherent to the body.

Returning on quadratic aspect of DR and BD by themselves, this aspect creates a lot of bugs. I'll show some examples:
A 10 BD attack (real quadratic value = 10² = 100) strikes against 1 DR (real quadratic value = 1² = 1). Using quadratic progression of DR and Damage, the force that pass the armor is 10²-1²=99 times major than DR, but the damage done in game is 10-1=9, 9²=81 times the DR. So, DR 1 in this case is 19 times plus strong than his effective value.
Also, quadratic progression of basic damage isn't compatible at all with wounds and stopping power. This is a great bug and this is why I still trying to convert damage and DR in linear absolute value.

Anthony
The fact that TL6 steel is automatically better than TL4 steel; actually, in our TL8 era, some types of industrial iron or steel aren't suitable for medieval-armor production.

[Anthony]

Originally Posted by Gustavus Adolphus

Not exactly, in fact you can do high-quality steel THIN armors (up to 2 mm thick for "superior quality steel" with W 1.5, and up to 3.25 mm for good steel with W 1.1) in middle TL4 Europe.

How does that conflict with what I said?

[DanHoward]

Originally Posted by Polydamas

The formula which Dan Howard used is that a very light cuirass and fauld is about 1 mm thick and weighs 8 lbs

I based it on the fact that the lightest cuirasses are around 5-6 lbs in weight but they only cover the chest. Thicknesses on these cuirasses vary between a little more than half a mm on the back and sides to a little more than a mm in front. I just averaged it to 1mm to make things simple. Realistically the average thickness would be a little under 1mm. I think the weight discrepancy between real examples and the Mosteller formula is due to a lot more being lost around the armpits than many suspect. The fauld weight was simply calculated using the hit location percentage. Using real data for faulds doesn't help much because this armour overlaps part of the chest and thigh armour which isn't accounted for in LT.

[Anthony]

Originally Posted by DanHoward

I think the weight discrepancy between real examples and the Mosteller formula is due to a lot more being lost around the armpits than many suspect.

I suspect it's mostly not realizing how little area the thicker parts of the armor cover. It's no different from high tech armor with a realistic coverage of around 30% being treated as full coverage.

[safisher]

Originally Posted by Anthony

I suspect it's mostly not realizing how little area the thicker parts of the armor cover. It's no different from high tech armor with a realistic coverage of around 30% being treated as full coverage.

It's really the difference between treating known historical artifacts as being identical to armor designed with a notional system. Which you cannot do. Both are going to be pieces of armor that do what they do -- protect the body. But they are two _entirely_ different ways to approach "How much does my armor weigh?" Which is different from "How much of my body does my armor cover?" Neither of these approaches to these questions has ever, in GURPS, really dealt with normal human size variations, such as body weight calculations, body composition, or gender differences. And all of these are _major_ factors in armor weight and coverage in real life.

When people quote known historical armor weights, only, they are missing so much of the other questions about variation that make comparing a given armor's material effectiveness very difficult. Then you add in the other elements -- that so few functional tests of the actual armor have been undertaken, that so few existing artifacts have been tested and sampled, that there is an unknowable background behind many pieces of armor make it difficult to discern whether it is exceptional to the point of being a useless baseline data point, and so on.

The end result is that you have a bunch of very strongly held opinions that are often founded on rubbish, both from the standpoint of GURPS game mechanics, and from the study of historical artifacts and material culture. On top of that, you then must deal with the material sciences and how they work within the game.

The real issue then is NOT "what is realistic?" but "what is consistent within the game?" because any number of strongly held opinions and misunderstandings can result in decisions that can change the starting and end points. Players and GMs ought to first consider what they want the game to look like, and then make the decisions about armor effectiveness from there, because the case can easily be made for a wide amount of interpretational variance, none of which are wrong, but just different from one another.

[Tomsdad]

Originally Posted by Gustavus Adolphus

...
Returning on quadratic aspect of DR and BD by themselves, this aspect creates a lot of bugs. I'll show some examples:
A 10 BD attack (real quadratic value = 10² = 100) strikes against 1 DR (real quadratic value = 1² = 1). Using quadratic progression of DR and Damage, the force that pass the armor is 10²-1²=99 times major than DR, but the damage done in game is 10-1=9, 9²=81 times the DR. So, DR 1 in this case is 19 times plus strong than his effective value.
Also, quadratic progression of basic damage isn't compatible at all with wounds and stopping power. This is a great bug and this is why I still trying to convert damage and DR in linear absolute value.
...

TBH given the fact that damage in GURPS while linear in progression, isn't actually linear in result due to the various thresholds that come into play (major wound, crippling, bleeding, etc, etc) I don't think you'll gain much trying to wrangle the difference between quadratic scales in there.