Writing up metallurgy for a campaign
 

I've decided to undertake the humongous task of making a (somewhat) detailed writeup of the available metals (and related materials) in this fantasy world I'm working on. I've hunted the various books and supplements I own without much luck to guide me, and my Google Fu is abysmal (probably I have Incompetence: Google Fu).

Anyway, what I'm looking to do is making a plausible (or at least semi-plausible) stat block for each of the materials, which would include Density, Hardness/HP per inch, cost (this world conveniently has a natural center of trade that could be used to define standard/benchmark prices), and other properties (such as breakage odds, electrical properties, magical properties, availability, refining processes, skills or skill levels required to be able to work with it (if applicable)).

I get from the Basic Set that steel has a hardness of 50-70 DR/inch. Without much else than that to extrapolate from, it's very difficult to go further while still keeping it in touch (and balanced) with already published content.

So, it comes down to this: I seek guidance, either in the form of books and/or supplements that I might find useful, or in the form of helpful advice (or actual help) here. Or links to other useful stuff.

Re: Writing up metallurgy for a campaign
 

I found this when I was trying to figure out how to work a system for making guns into Metatronic Generators. Since it gives Density in g/cc and lb/ci, you can use it to solve your density issues. For fantasy metals, you can just look to the source and assign a number based on the number it gives relative to teel or iron

Re: Writing up metallurgy for a campaign
 

That's still just arbitrary. For instance, what kind of steel is 50 DR/inch? What is 70 DR/inch? What types of steel are in between (and what are their real world hardness)? How much is iron? Is "hardness" to DR in GURPS an exponential scale? Logarithmic? Linear? It's quite easy to find real world data for hardness and density. It's the conversion to GURPS that gets tricky, as I can't really find any benchmark reference to extrapolate any kind of trend or formula from.

Re: Writing up metallurgy for a campaign
 

At least in 3e GURPS, it was canonical that the type of steel called Rolled Homogeneous Armour (RHA) has a DR of 70/inch. One problem in a fantasy setting is that alloys of iron and of copper do not have standardized properties: two lumps of "Spanish iron" or "latten" could be quite different in composition. GURPS “DR” measures resistance to penetration not hardness as engineers use the term. The engineering term hardness is only one factor in resistance to penetration.

The hit points of a solid sheet of material are determined by its mass according to a formula in the Basic Set (4e).

Re: Writing up metallurgy for a campaign
 

This is exactly the point. How would one go about writing up the differences between ordinary steel (whatever we call it), very fine steel (Damascus steel, maybe?), pig iron, etc.'? Just having some properly grounded baselines for these differnt types of steel could allow for some extrapolation. It'd be even better if one could add the same things for different types of bronze (cornthian bronze, hepatizon, orichalcum, etc.). Then for each other material, it could be compared to these figures.

Indeed. And in engineering that is (AFAIK) a combination of hardness, plasticity, elasticity, etc. (tensile strength, ductile strength, w/e). So this is abstracted down into a single figure, and for brittle or semi-brittle materials, we just define them as ablative or semi-ablative, respectively. Big question is, how would the scale for DR go? A material with double the strength have double DR? Or is it quadratic, cubic, or something else entirely?

As with most homogenous objects. This is the easy part.

Re: Writing up metallurgy for a campaign
 

You can't do it realistically. If you want to do it for a game then you just pick some arbitrary figures.

Re: Writing up metallurgy for a campaign
 

Various low-tech metals that I'm aware of:

Bronze (copper-tin alloy): low tin content (2%-7%), regular tin content (~8%-12%), high tin content (up to 20%)
Brass (copper-zinc alloy): same zinc contents as tin with bronze
Pewter (tin-lead-antimony alloy)
Electrum (amalgam of gold and silver)
Iron: wrought iron (low carbon content), various grades of steel, cast iron (high carbon content)
Copper
Gold
Silver
Lead
Tin
Zinc
Quicksilver/Mercury

Re: Writing up metallurgy for a campaign
 

The problem with associating DR with a single property is that there are different modes of failure.

e.g. a thin sheet of ductile material used as armor may plasticly deform and transfer the energy (damage) through whereas a thicker sheet may nees to actually be penetrated (exceed toughness and cause rupture) to allow the residual energy to reach the target.

q.v charpy test http://en.wikipedia.org/wiki/Charpy_impact_test

This differs from (but is somewhat related to) hardness. http://en.wikipedia.org/wiki/Hardness

Recall also that good metallic armors (just like the good weapons attempting to defeat them) are not going to be homogeneous. Even a thin tempered plate can have a hardened (and somewhat brittle) surface covering a softer but tougher core. Heat treatment of steel is a VERY complex issue.

If I were to attmept a project such as you are proposing, especially in a fantasy campaign with mystical abilities and materials, I would start by listing properties and then assign processes/names/costs/skill levels/exclusivity to those properties.

Things like the reduced weight, corrosion resistance, supernatural effects, shape memory, magnetism, etc. Make them optional treatments for some materials with specialized skills (probably at high cost or requiring special materials).

I believe there is a good start to this kind of 'power-up' method in the DF series already. Anything that attempts to incorporate more rules out of a materials textbook is likely to fail on the effort/fun*accuracy rating.

Re: Writing up metallurgy for a campaign
 

Many people mistakenly believe that steel has a higher C content than Iron. This is inaccurate.
Compare C content listed here
http://en.wikipedia.org/wiki/Carbon_steel
with
http://en.wikipedia.org/wiki/Cast_iron

The trick isn't getting in more Carbon but rather getting Carbon and Oxygen out to leave purer Fe and THEN carefully controlling the additions of alloying agents.

Re: Writing up metallurgy for a campaign
 

What do you mean by “strength”?

I think that even trained metallurgists rely heavily on experiments to predict the properties of a new alloy, and the formulas which they have are very complicated and assume a world which does not work the way many fantasy settings do (one without spirits, undead, disintegration rays, or enchantments of unbreakability but with industrial processes which can make identical sheets of metal).

This could be a great excuse to learn some metallurgy, but I don't think you will learn much that is helpful for gaming.

Re: Writing up metallurgy for a campaign
 

Is this realistic fantasy? It would be interesting to create a variety of fantastic material with different properties...

Re: Writing up metallurgy for a campaign
 

For fantasy, I wouldn't worry too much about the minutia of how much DR or HP a bar of different metals has.

What matters is: who does equipment made of this material differ from equipment made of the standard material (especially weapons and armor). This is a much simpler enterprise.

FREX: Treat Bronze as Steel, except CF 5. Mythril weapons never break and weigh 1/2 as much CF 100. Mythril Armor has +4 DR and 1/2 Weight for CF 100, or can be made thicker: +8 DR, full Weight, -1 DX, CF 200. Etc...

Only very rarely will you have to determine how difficult it is for your adamantium axe to cut through the mythril bars of a jail cell. In those situations, just make something up.

Re: Writing up metallurgy for a campaign
 

As a cheat, you can always use the stats for high tech materials and just call them by different names.

GURPS Low Tech, GURPS Fantasy and some of the Dungeon Fantasy books have material you can mine - so to speak.

Re: Writing up metallurgy for a campaign
 

Long time without me having time to check back in here. Okay, some thoughts.

See, this is the question I'm trying to figure out myself. How does GURPS define "strength" in relation to DR/inch?

True. However, I'm mostly interested in existing metals and alloys, and then new ones can be extrapolated. Just need to have a few, well-known basics in place first.

This is not entirely true. The most commonly used iron alloy was wrought iron, containing less than 0.25 % carbon, whereas steel is less than 2.1 %. Cast iron, with carbon content of 2.1 % and up, were not in common use before the rennaissance (in Europe, at least). Cast Iron is very brittle and hard, whereas steel is quite soft and malleable. Which you can actually also read from the links you posted, if you also look at the sidebar containing references to other iron alloys.

Very difficult question. Yes, and no. Yes in the way that the physical world needs to make sense and be realistic (or at least well grounded). Once that foundation has been laid, magical and other exotic materials and effects will be added.

And yeah, it's very interesting to create a host of fantasy metals. Where does your quote come from?

I didn't find anything of particular use in Low Tech. I haven't had the patience to figure which one(s) of the DF books I could potentially use (there's like a million of them). Fantasy actually didn't occur to me, I'll have a look. If you can guide me to which ones of these books (and maybe also chapters/pages), it would be fantastic.

Re: Writing up metallurgy for a campaign
 

GURPS does not define "strength" in that context. It defines DR as resistance to penetration by projectiles, and scales it so that RHA steel has DR 70/inch and other materials have strength in proportion. Some people find the proportion by research and others make it up.

Re: Writing up metallurgy for a campaign
 

The problem--or, at any rate, a problem--is that I suspect that you're after a formula which is far beyond the scope not just of GURPS but of just about anyone who isn't a technical specialist. As I understand it, RHA-equivalent is sort of the yardstick for discussing modern armor, so people who come to GURPS with real-world armor stats expressed in RHAe can come up with an equivalent DR. However, coming up with an RHAe for something is what scientists call Very Difficult, and doing the massive work involved is the realm of materials engineers with government grants. So GURPS authors don't have a method for determining DR beyond:

1) If there's a published RHAe for the material/item, use that.

2) If not (which is probably universally the case for anything historical), make something up that looks good.

At any rate, even if you were to come up with RHAe values for a range of the sorts of alloys one finds historically, the inability of ancient smiths to precisely control their materials and manufacturing conditions puts some significant error bars of the quality of what they make from batch to batch. So you'd end up having to track a list of "Platonic ideal" materials and how close any given smith got to that on any given batch of material while smelting and alloying and the extent to which a later smith, making an item from that batch of metal, changed it. Oh, and without sophisticated testing technology, neither the smith nor his customers will be able to tell the difference with much more granularity than "this is junk," "this is OK," and "this is pretty good."

Re: Writing up metallurgy for a campaign
 

Sure. The big question is, in relation to GURPS game balance compared to weapon damage output, how does it scale? Does half the RHA of steel means half the DR?

Haven't someone made a "formula" for damage in relation to "muzzle velocity" or some other measure of power for HT and UT weaponry? In that case, how? And how does it compare to the stats of armors/DR?

Which is all pretty good. The idea is just to get some sort of guideline as to what RHAe means in relation to DR. And for this, only a select few handful of materials are needed stats for. Just three would do, I think, if stats for both DR and RHAe could be had. That's enough to extrapolate from. Just finding the relation/ratio/scale between RHAe and DR in the first place is what I'm after.

Re: Writing up metallurgy for a campaign
 

Low-Tech assumed that a 1mm breastplate of RHA equivalent steel was DR 3 and that every +0.5mm granted an extra +1 DR. Bronze was exactly the same except that it cost more. Hardened steel added a flat +1 DR. The problem is that the DR includes the fact that breastplates have a deflective component that used to be PD in the old GURPS. The DR also incorporates some light underpadding that isn't thick enough to be DR 1 on its own. This seems to work ok at breastplate thicknesses but not at vehicle plate thicknesses. You have to use some variant of Douglas' "Armor as Dice" mechanics for those.

Re: Writing up metallurgy for a campaign
 

As I said, armour equivalent to 1” of RHA has DR 70. Armour equivalent to twice or half that thickness has twice or half the DR. Projectile damage scales roughly with the square root of kinetic energy divided by diameter, and the DR of a flat plate scales roughly with thickness. (It seems that things get more complicated at very high velocities and high energies, but this works well enough for bullets and arrows).