[High-Tech] Drills: what's the point of the Armour Divisor?
 

Greetings, all!

PCs are considering drilling holes in a concrete ceiling to let through an endoscope. Looked up the DR and HP of 8" Reinforced Concrete at DR 96* and HP80, looked up power drill/hammer (the heavier one) damage at 2d+2(2). Okay, so what's the point of the (2)? It doesn't make a difference against steel thicker than about ¾" (unable to make a hole in it at all), and it has an absolutely negligible effect on the time it takes to drill anything made of concrete.

Thanks in advance!

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

Concrete drills are pretty specialised; I'm not sure how you'd do them in GURPS.
Otherwise, you're mostly relying on the ablative (or semi-ablative, I don't remember off the top of my head) nature of the DR. Which, like you said, means the divisor doesn't much matter (except to further diminish the minimum DR, I guess).

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

You can also drill wood, brick, etc...
Technically, the damage is the same as 5d pi-.

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

No it isn't. That's my point. The armour divisor doesn't contribute to drilling wood/concrete, and is too low to allow gradually drilling a steel wall. It's unclear what purpose it serves.

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

You have DR 96, HP 80. Repeated huge piercing attacks (pi++) lower DR as if ablative (footnote, p. B559), to a minimum DR 3. Against a homogenous target like concrete, huge piercing has a wounding modifier of ×1/2 once it penetrates DR (p. B380).

With 2d+2 pi++, you'll average 9 points of damage per second. You'll need 10 seconds to ablate DR 90, leaving DR 6. On the 11th second, you'll put 3 points past DR 6, which will inflict 1 HP, and also ablate down to DR 3. Then you'll be putting 6 points per second past the minimum DR 3, inflicting 3 HP per second, for the next 26-27 seconds. Total time: 37-38 seconds.

With 2d+2(2) pi++, you'll average 9 points of damage per second. But now DR is halved! You'll need five seconds to ablate DR 45, leaving DR 3. Then you'll be putting 8 points per second past half the minimum DR 3, inflicting 4 HP per second, for the next 20 seconds. Total time: 25 seconds.

The main advantage is that if you're boring dozens of these a day on a worksite – say, to pass cable – you're taking 2/3 as long to do it. That's a huge savings in labor. When you're trying to be sneaky . . . well, a rotary hammer isn't the tool for the job! But 2/3 as long to be noticed should be good for reducing whatever bonus the GM gives your opponents for a sustained racket.

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

Wait, I don't get it:
2d+2(2) halves DR for purposes of penetration . . . but reading the entry on Semi-Ablative (B47) and DR loss on concrete (B559), it doesn't care about armour divisors, and is reduced based on damage rolled, not injury sustained.

Where does the faster ablation come from?

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

Where does either rule say, "ignore armor divisors"? Nowhere, because you don't do that. An attack with a divisor faces less DR in the first place. It's this DR that's reduced, not full DR. If I have a divisor (2), then I need to carve away DR 40 to get through a DR 80 ablative target. On the other hand, if another attack comes along, I've only carved away DR 40, so that attack still faces DR 40, because the DR just has a little hole in it.

Please check my examples again. Nowhere am I using injury. I only start applying the injury rules once the damage begins to penetrate DR. That's when homogenous kicks in.

The fact that pi++ is treated as ablative, not semi-ablative. The footnote on p. B559 is quite explicit on this point: "Repeated impaling, piercing, and large piercing . . . semi-ablative; repeated burning, corrosion, crushing, cutting, or huge piercing . . . ablative." And p. B47 is quite clear on how ablative DR works; namely, it's carved away on 1:1 basis by damage points. This is why just about all tools intended for slicing through bulk matter are either burning (burn) or huge piercing (pi++).

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

Where does it say that armor divisors apply? There's no obvious reason they should, either realistically or from the game text. Also, from a game perspective, having armor divisors apply is a bad idea, it should be possible for attacks to have different performance for purposes of penetration vs damage to armor.

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

...So when you start drilling, the idea is that the (2) is supposed to tell you to divide the DR into two piles, one of which the attack ignores and the other of which the attack ablates?

I would never, ever have guessed that one.

Re: [High-Tech] Drills: what's the point of the Armour Divisor?
 

The general principle is that unless a rule is explicitly ruled out in a situation where it would apply (and I think a mechanic for DR depletion and a mechanic for DR reduction clearly apply to DR), it does apply. We don't explicitly say that cutting damage gets its ×1.5 injury vs. targets that aren't alive, but it does . . . we just leave it out of Injury to Unliving, Homogenous, and Diffuse Targets and assume that people will apply the multiplier because we didn't say not to. Most rules work like that in GURPS. The onus of proof is on those setting out to prove that rules don't apply, not those merely asserting that rules continue to apply.

Whether this is a good rule isn't what I'm discussing here. I'm explaining how the rules actually work.