DM Pragmatics: The Big Mistakes

[The_Mad_Linguist]

But the breaking rules saaaaaaaaaaaay...

...that you can break plywood with a quarter-inch dowel by swinging it hard enough? No, sorry, you can do your damage, but the laws of physics still apply.

Look man, I can fucking jump twenty feet straight up without trying.  We kicked physics to the curb five levels ago.
alternatively
What, and people can't break wooden boards with their fleshy meats?

[Whisper]

But the breaking rules saaaaaaaaaaaay...

...that you can break plywood with a quarter-inch dowel by swinging it hard enough? No, sorry, you can do your damage, but the laws of physics still apply.

Look man, I can fucking jump twenty feet straight up without trying.  We kicked physics to the curb five levels ago.
alternatively
What, and people can't break wooden boards with their fleshy meats?

Answer to first:

You are special. You are awesome. You are a pepper. You can do over 100 points of damage with a single attack, and hold your breath for six minutes. Your mace, however, is just a piece of metal. It is not strengthened by the fact that it's you holding it.

Answer to second:

Don't try that argument on a GM with a black belt rank. Wooden boards, and in fact concrete blocks, break a lot more easily than fists. This is because they are made of lots of little bones with shock absorbers between them.

[The_Mad_Linguist]

Your mace, however, is just a piece of metal. It is not strengthened by the fact that it's you holding it.

A tornado can drive a vinyl LP into a telephone pole.


A tornado deals 6d6 damage per round.  A melee brute is going to deal like five times that.

[veekie]

Me, I'd make the door hollow and filled with a nasty substance or make it a construct with fast healing(which then animates and initiates combat with the party with lasers)...assuming you want to stop them from passing it that much. You did put a door there and doors are meant to be opened.

Come on, bashing down a door, even with adamantine, takes time and is noisy as hell. Its like a drum only you're hitting a hell lot harder. I'll be glad enough that they're respecting the WALLS.

[Whisper]

Your mace, however, is just a piece of metal. It is not strengthened by the fact that it's you holding it.

A tornado can drive a vinyl LP into a telephone pole.
A tornado deals 6d6 damage per round.  A melee brute is going to deal like five times that.

That doesn't make the vinyl LP stronger than it is. It doesn't pay to be the telephone pole or the LP in that interaction.

Every action produces an equal and opposite reaction. Don't they make you kids take physics in college anymore?

[stranglebat]

Cutting power is the force divided Surface Area of the cutting utensil. Things like that LP would cut right in because it is focusing all that pressure on the tiny edge. It would had to have been a direct hit though otherwise it would have shattered. Id wager an Adamantine Dagger would cut through the door where the mace might not smash through it, it possible still can though.


But bringing physics into D&D is downright stupid and then being condescending about a limited amount of knowlegde that doesn't even apply to this situation (IE Physics does not apply to D&D) is untactful.
Argue your point if you must but saying stuff like "Don't you kids take physics anymore" just makes you look bad. Why don't you try proving your point rather than being contrite and just trying to discredit the other person.

[veekie]

The practical thing is considering why the door is there really, as a DM.
What role does it play?
If it's a puzzle and they skipped the puzzle, well theres drawbacks for such things. If it's a barrier, why the heck did you put a VISIBLE door there? PCs are known for going as far as straight through the walls with an OH YEAH!
If you don't want them going there don't start with a route there.

[The_Mad_Linguist]

And yet, you'll notice that the LP is perfectly intact.

Sure, the forces are equal.  And the mace is part of an elastic spring-damper system which allows it to dissipate the energy much more effectively.  The door, on the other hand, lacks a handy shock absorber.  In addition, you've got a hefty mechanical advantage working on your side.

A more rigorous analysis, of course, requires you to go through a non-static deflection analysis, approximating it as a flat plate with a fixed edge.  The math for this is a rather irritating set of nonlinear differential equations, and you're not paying me to work it out.  

In the static point-load case, deflection scales linearly with the area of your plate, and inversely with your thickness.  That alone makes a door possibly the worst possible shape to avoid deflection.

Additionally, from the "not real materials science" side of things, there's that unique ability of adamantine weapons to bypass hardness - an ability not possessed by other objects made of the material, so clearly there's some mystical bullshit going on as well that makes adamantine great for weapons.

I suppose I could simulate it with COMSOL if I had material properties for adamantine, but again, I'm not willing to work for free.

[Agita]

Every action produces an equal and opposite reaction. Don't they make you kids take physics in college anymore?

I'm a Physics student. If a melee character can do 100+ damage with an adamantine mace, he's getting past the door, Physics be fucked. There is no such thing as Physics in D&D.
If you don't want them to just brute force the door, veekie's approach is preferable IMO.

[McPoyo]

Addendum: I've put 3 grams of copper jacketed lead with a rounded nose through 3/8ths of tempered stainless with a curve on it with only mild deformation of the projectile. Game stats would be 2d6. Copper and lead are both really soft compared to steel. Steel tipped pointed arrows fired from a 120 lb hunting bow mildly dented the same thickness plate without the curve from a set mount mathmatically perpendicular to the plate face, with severe deformation of the head. 1d8 weapon (arguably mighty composite +2).

Material makes less of a difference in those types equations than material shape. The damage is there, he deals over 100 points, which blows through more than three inches of iron, minimum. Impact force and cutting shear is irrelevant, mechanically, it's durability you are looking into and material deformation resistance, ie a combination of brittleness vs hardness. The fact that there's a dampener attached to the mace (an arm) goes a really long way to mitigating damage, and the shape of the head makes a huge difference. Best case would result in the mace dealing half damage to the door due to damage type instead of full. Mechanically represented damage to the weapon? Not a chance. And that doesn't involve the mystical hardness bypassing of adamantine.

[LordBlades]

Some food for thought (I'm not a mechanic expert, but studied this a bit in college): the door is supported only at the edges. Hitting it in the middle would create some form of torsion forces that would get amplified by the distance between the impact spot and the support points. My educated guess is that if you try to bash a metal door with a metal mace, it will start curving inward around the impact point until the edges pull away from the supports, and the door gives in.

I really think the feat is doable because you're putting the mace's resistance to compression (sorry if there's a specialized word for this that I'm missing) vs. the door's resistance to bending, and most metals are much more resistant to compression than bending.

[McPoyo]

Some food for thought (I'm not a mechanic expert, but studied this a bit in college): the door is supported only at the edges. Hitting it in the middle would create some form of torsion forces that would get amplified by the distance between the impact spot and the support points. My educated guess is that if you try to bash a metal door with a metal mace, it will start curving inward around the impact point until the edges pull away from the supports, and the door gives in.

I really think the feat is doable because you're putting the mace's resistance to compression (sorry if there's a specialized word for this that I'm missing) vs. the door's resistance to bending, and most metals are much more resistant to compression than bending.

If they aren't more resistant in the way you state, then they have a really high brittleness, and would shatter instead.

[veekie]

The trick is to use Doors of Force. Or some kind of solid goo.

[McPoyo]

My players would walk out if I had a dungeon that had doors made of ballistics gel...

[veekie]

Psh, ballistic gel Ooze sandwiched between iron plates.

[Agita]

Psh, ballistic gel Ooze Living Make Whole sandwiched between iron plates.

Fixed.

[The_Laughing_Man]

player: I'll smash that metal door with my adamantium mace.

DM: Your mighty blow weakens the door. The sound of impact echoes in the caverns. [roll a dice for listen check for nearby monsters]

player: We cast silence. I'll smash again.

DM: Your blow yet again weakens it. As it is silent on this side of the door, you'll feel the slight tremor on the ground caused by the blow. [monsters may be approaching but you don't hear it]

player: I'll smash until it breaks.

DM: It starts to break down. Little bit of rocks drop to your head. The tunnel roof does not look so good.

player: I'll continue smashing. (or strengthen the roof before that)

DM: You continue smashing. [cave-in?]

DM: The door breaks down. [surprise round for monsters?, roll initiatives?, you see an empty tunnel ahead]

Quite many options to play

[The_Mad_Linguist]

My players would walk out if I had a dungeon that had doors made of ballistics gel...

OK, Jamie wins initiative.  Everyone, make ten reflex saves.

[Sinfire Titan]

My players would walk out if I had a dungeon that had doors made of ballistics gel...

OK, Jamie wins initiative.  Everyone, make ten reflex saves.

+1 Internets to TML.

[Whisper]

And yet, you'll notice that the LP is perfectly intact.

Indeed, which implies it hit with much less force than a quick look at the photograph might suggest. Upon closer examination, it appears to be jammed into a vertical crack in the telephone pole (no mean feat, but not the same as slicing through wood with vinyl).

Sure, the forces are equal.  And the mace is part of an elastic spring-damper system which allows it to dissipate the energy much more effectively.  The door, on the other hand, lacks a handy shock absorber.  In addition, you've got a hefty mechanical advantage working on your side.

Indeed. The entity that would be in danger would be the shaft of the mace, not the head. It really depends what those 100 points of damage represent. Do they represent kinetic energy in some absolute sense? Or an abstract measure of the skill of the attacker at hitting the right location? Does "damage" mean the same thing when applied to a non-homogeneous structure with moving parts (people) as it does to a slab of metal (door)?

A more rigorous analysis, of course, requires you to go through a non-static deflection analysis, approximating it as a flat plate with a fixed edge.  The math for this is a rather irritating set of nonlinear differential equations, and you're not paying me to work it out.

Understandable.  

It may seem hard to imagine damaging a mace by striking a metal slab with it, but in most scenarios we might imagine, the limiting factor would be the strength of the wielder. If we have to take as given that the striker is a superhuman individual who can actually bash through a 4 cm metal plate... well, it might well be different.

Additionally, from the "not real materials science" side of things, there's that unique ability of adamantine weapons to bypass hardness - an ability not possessed by other objects made of the material, so clearly there's some mystical bullshit going on as well that makes adamantine great for weapons.

I suspect when they came up with that, they were thinking of sharp weapons. One might well imagine bypassing damage reduction with the sort of edge that could be held by a material as hard as glass, and as durable as low-carbon steel.

This probably got extended to blunt weapons more in the service of balance than rationale.