Vehicle hit points

[Ulzgoroth]

That article has a couple parenthetical remarks about 'special rules for cannons', with no referent I can locate. What's that talking about?

Originally Posted by Kallatari

Correct me if I'm wrong, but does that article not basically say for every +1/-1 in SM difference between the attacker and the target (assuming the attacker's weapons are designed/scaled for his size), you divide or multiply injury - or in other words, apply an additional wounding modifier - along a 6-step log scale of the Range/Speed Table of 1.5, 2, 3, 5, 7, 10, etc.? Wouldn't that be an easier way to define it instead of trying to rate weapons as pi+6 or cut-5?

Since most of GURPS is geared for the human scale (SM+0), does that then not translate into - on most occasions other than when using vehicular weapons - a target of SM +1 divides injury by /1.5, SM +2 by /2, SM +3 by /3, SM +4 by /5, etc. That makes it an easy "rule of thumb" to apply for most gaming situations with human-sized PC.

That parenthetical assumption is being asked to do a lot of work and doesn't include the tools to do it well.

Consider that human-scale weapons under RAW range from pi- (which is more like pi-2 by numbers) to pi++/imp. Your suggestion doesn't provide any infrastructure for that variation, let alone for applying that range of variation at other scales.

(Plus that variation is already quite inadequate - human-scale weapons include things like 40mm grenades and 80+mm LAWs)

[maximara]

Originally Posted by the-red-scare

Pretend you’re in charge of choosing the hit point system for GURPS Vehicle Design. Unlike David Pulver in the real world, you have no mandate to be even slightly consistent with established 4e vehicle stats, but do have to remain consistent with the rest of GURPS mechanics and weapon damage values. You can choose any of the existing systems or build your own.

3e: multiply surface area by 1.5, with a 0.1x to 2x modifier based on frame strength. Cars have around 200 HP, an SM +10 space cruiser might have around 150,000 HP.

4e: multiply the cube root of empty weight by 4. Cars have around 60 HP, the same space cruiser has around 1,000.

Unused 4e (from Pyramid “Extreme Damage”): multiply the square root of empty weight by 1.7. Cars have around 100 HP, the space cruiser has around 7,000.

Damage never changed from 3e to 4e, but vehicles are anywhere from 2x to 150x or more easier to destroy. I know there’s lots of ways to mitigate that via house rules, but suppose you were staring over: what kind of HP formula actually makes sense for vehicles and makes them appropriately easy or hard to kill?

Perhaps I am missing something but by the square-cube rule the base 4e should make vehicles harder to destroy.

[Polydamas]

Originally Posted by the-red-scare

Pretend you’re in charge of choosing the hit point system for GURPS Vehicle Design. Unlike David Pulver in the real world, you have no mandate to be even slightly consistent with established 4e vehicle stats, but do have to remain consistent with the rest of GURPS mechanics and weapon damage values. You can choose any of the existing systems or build your own.

3e: multiply surface area by 1.5, with a 0.1x to 2x modifier based on frame strength. Cars have around 200 HP, an SM +10 space cruiser might have around 150,000 HP.

4e: multiply the cube root of empty weight by 4. Cars have around 60 HP, the same space cruiser has around 1,000.

Unused 4e (from Pyramid “Extreme Damage”): multiply the square root of empty weight by 1.7. Cars have around 100 HP, the space cruiser has around 7,000.

Damage never changed from 3e to 4e, but vehicles are anywhere from 2x to 150x or more easier to destroy. I know there’s lots of ways to mitigate that via house rules, but suppose you were staring over: what kind of HP formula actually makes sense for vehicles and makes them appropriately easy or hard to kill?

If you remember his username, David Pulver posted an alternative model around 2006 based on data from the Falklands War and WW II (I don't remember his username so I can't give you the link). But a basic principle of GURPS is that everything should use the same model, so GURPS' HP model would have to change to fix issues like "rifle-calibre machine gun sinks galleon" (another poster, possibly Bill 'whswhs' Stoddard, noted that by the 18th century warships totally have thick wooden armour which should give DR).

Edit: Here is the post by Pulver

[Ulzgoroth]

Originally Posted by maximara

Perhaps I am missing something but by the square-cube rule the base 4e should make vehicles harder to destroy.

There's no square involved, it's just a cube root.

[Anthony]

Originally Posted by Kallatari

Correct me if I'm wrong, but does that article not basically say for every +1/-1 in SM difference between the attacker and the target (assuming the attacker's weapons are designed/scaled for his size), you divide or multiply injury - or in other words, apply an additional wounding modifier - along a 6-step log scale of the Range/Speed Table of 1.5, 2, 3, 5, 7, 10, etc.? Wouldn't that be an easier way to define it instead of trying to rate weapons as pi+6 or cut-5?

Then you run into the oddity of 'the exact same weapon, used by a different creature, causes different wounding'. If you want it to scale with the weapon instead of the wielder, you wind up needing to note somewhere in the weapon description the effective SM, at which point you might as well just put it in the damage.

[Varyon]

Originally Posted by Anthony

That's pretty much what I did with expanded wound size modifiers.

I tried my hand at that, but couldn't resolve how to handle cr and cut. For the former, a good explanation of the problem can be found with the flanged mace (standard GURPS Mace) vs the round mace (introduced in LT). The former was invented as an improvement over the latter, and concentrates the force of the impact into a smaller area, resulting in better armor penetration as well as better wounding against even unarmored foes. But, if we're scaling WM based on the cross-sectional area of an impactor, the round mace should have a larger WM than the flanged mace. Even if the difference is only +1 to WM (for x1.5 to Wounding) - which is likely far too small, given the size difference - that means the flanged mace has to deal 1.5x as much basic damage as the round mace to simply equal its wounding - and even that underestimate is too much improvement in armor penetration.

For cut... a sharp edge is a sharp edge. Size is more an issue of the length of the cutting edge - it may be too short to reach anything important, or long enough to be able to cut the target in half, but judging that is... a bit difficult.

The only solution I could think of was to just not have cr and cut have any scaling, always being x1 and x1.5, respectively... but that just feels off.

Originally Posted by Varyon

The article is "Ten for Ten," from Pyramid #3/70. The preview, unfortunately, doesn't include the rule in question, so I'll have to wait until I get home to my personal computer to check it (or wait for someone else to find and mention it, at least).

Able to check it now, the part of the article that references vehicles being unduly susceptible to small arms fire is under Damage Reduction (referring to the Injury Tolerance of the same name), and he just notes that the trait "contains the seeds of solutions to many problems (e.g., making it harder to destroy huge vehicles and buildings using small arms)."

[Anthony]

Originally Posted by Varyon

I tried my hand at that, but couldn't resolve how to handle cr and cut.

Unfortunately, the real answer is that the exact same armor thickness has different protective value against cr and cut depending on the size of the wearer (and also the GURPS dr model is in general not very applicable to cr and cut, because unlike piercing an impaling, the protection from armor is not "stops everything until you get through it and then stops nothing", it continues to absorb a fraction of damage as the wound gets larger).

[Ulzgoroth]

Originally Posted by Anthony

Unfortunately, the real answer is that the exact same armor thickness has different protective value against cr and cut depending on the size of the wearer (and also the GURPS dr model is in general not very applicable to cr and cut, because unlike piercing an impaling, the protection from armor is not "stops everything until you get through it and then stops nothing", it continues to absorb a fraction of damage as the wound gets larger).

Also applicable to some impaling weapons - plenty of those have an ongoing taper along their length rather than being basically constant cross section.