D&D General Is this a fair trap?

[Charlaquin]

I found some of that stuff too. But having had some friends who did doctoral work on rheology and non-Newtonian fluids (both where chemical engineers) I am confident that the maths will be beyond my ability to interpret or apply! (A warning sign for me: as soon as the paper/web page starts talking about shear forces I know I'm not going to be able to follow it!)

I did learn that higher Bloom value in a gel usually means greater transparency, so a gelatinous cube probably has very high bloom value, given that it is almost perfectly transparent. I can’t do anything with that information, but I guess it’s kinda neat

 

[Maxperson]

I did learn that higher Bloom value in a gel usually means greater transparency, so a gelatinous cube probably has very high bloom value, given that it is almost perfectly transparent. I can’t do anything with that information, but I guess it’s kinda neat

Google says the higher the bloom value, the greater the gelatin strength. What that means to a 85 ton hunk of rock falling onto the cube, I have no idea.

 

[pemerton]

I did learn that higher Bloom value in a gel usually means greater transparency, so a gelatinous cube probably has very high bloom value, given that it is almost perfectly transparent. I can’t do anything with that information, but I guess it’s kinda neat

So your post pushed me to look up the Bloom test on Wikipedia: Bloom (test) - Wikipedia

I learned that a high Bloom number gelatin needs a 300+ gram plunger of 1.252 cm diameter (0.5 inch for any non-metricoids following along) to depress 4 mm without breaking. Wikipedia didn't tell me anything about the motion of the plunger in the Bloom test; the static pressure of that plunger is 0.3 kg * g / (0.01252 m)^2 = 0.3 * 9.8 / 0.0001567504 = approx 18,756 Pa.

That's about one-thirty-sixth of the pressure I calculated in post 125. So I tentatively infer that, unless the collision takes over 3 seconds for the block to decelerate once it hits the Cube, then the Cube will break as a result of being depressed by the block.

I think that speaks to a modest degree in favour of the mechanical feasibility of this trap!

EDIT: I've treated my plunger as square. As a circle its area has to be multiplied by pi/4, which makes 4/pi an additional multiple of the pressure, which makes the pressure approximately 23,880 Pa. That's a bit less than a twenty-eighth of the post 125 value. So the non-breakage deceleration time is a bit less than 3 seconds, but more than 2.5 on these numbers.

 

[pemerton]

Google says the higher the bloom value, the greater the gelatin strength. What that means to a 85 ton hunk of rock falling onto the cube, I have no idea.

See my post just above this one for a tentative conjecture.

 

[Ruin Explorer]

I'm still not seeing a single scenario which avoids all four of the failure modes for the Yellow Mold that I described. There's just no way around the facts that it only has a 50% chance to go off, and only hits on top of the block (assuming this ludicrous magic rope, magic pulley scenario which is not in the original somehow results in an impact strong enough to trigger it, which is questionable).

Honestly at this point I feel like we should be calling Mythbusters.

Hell, maybe we should do a Mythbusters of old-skool traps? I.e. first we analyze them exactly as written, and probably a lot of them fail, but then we figure out how we could make them work.

 

[pemerton]

Here is the relevant text for Yellow Mould, from the AD&D MM, p 71:

A more common underground fungus is yellow mold, which is pale yellow to a golden orange in color. Any creature which touches this mold is attacked by its enzymes. It also affects wood, albeit more slowly. It does no harm to metals or stone. If the substance is contacted roughly, there is a 50% chance per contact that the colony will release spores. These deadly spores shoot out in an asphyxiating cloud, 1" by 1" by l", originating from the center of impact.​

So the spores are a 10' x 10' x 10' cube about the centre of the impact/rough contact. How does that relate to the size of the mould colony? It seems counter-intuitive that the larger the colony the proportionately smaller the cloud; so I think that if the whole of a 10' x 10' colony is roughly contacted then the cloud will be 10' all around it.

Does dropping 10' on a stone block count as rough contact? I think it's pretty reasonable to suppose that it does. How many contacts does it amount to, for the purposes of 50% chances? I don't know, and I don't think AD&D has a canonical answer to this. Looking up the Rules Cyclopedia, it says that each touch of a torch has the requisite 50% chance, but nothing more. I think the fall of the block must count as more than one touch - maybe one check for each 5' x 5' quadrant?

 

[Ruin Explorer]

So the spores are a 10' x 10' x 10' cube about the centre of the impact/rough contact. How does that relate to the size of the mould colony? It seems counter-intuitive that the larger the colony the proportionately smaller the cloud; so I think that if the whole of a 10' x 10' colony is roughly contacted then the cloud will be 10' all around it.

Absolutely not. How the hell would you get 10' all around it from that? 5' all around it. The cloud is 10' wide, not 20' wide. It would need to be 20x20x10 to work the way you're describing.

If you have a 9.9x9.9x10 block or similar, well first off that's going to jam, but whatever, ignoring that, if the ENTIRE upper surface is covered with Yellow Mold, and each bit blows, you can get coverage on 5' squares around the block but only because you'd get partial coverage (which is usually considered enough).

I would agree that it's valid to roll separately for each 5' square which has Yellow Mold on it, so you'd likely trigger at least two Molds on the average drop, if the drop was hard enough.

Does dropping 10' on a stone block count as rough contact?

It's not as reasonable as you think, because the forces involved are extremely low. It's a short drop. If it's a 9.9x9.9x10 block and the GC is nearly incompressible, then it's slightly more reasonable, but the problem is, it'll detonate when it HITS the GC, not AFTER it hits the GC - that means the TOP of the block will be still nearly at the ceiling when they go off, which means that the spores really aren't easily going to hit anyone.

The logical flaws with this are just huge. You solve one problem, you create another.

And the whole thing could easily be made to work perfectly as intended with the redesign I suggested early in this thread. If you switched to a 9.9x9.9x5' or less block you'd be in a better situation for what you're proposing.

 

[akr71]

I voted yes, but it is needlessly convoluted. Who hides their treasure under a 'cube? What if you need it? It got a yes because as long as the adventurers have a chance to notice & disarm it, its fair game. Would I use it? No.

 

[Quartz]

I've sblocked the trap description:

Doesn't matter. The question you need to ask yourself is, "Is it fun?" Does it add to the players' enjoyment of the adventure?

 

[pemerton]

Doesn't matter. The question you need to ask yourself is, "Is it fun?" Does it add to the players' enjoyment of the adventure?

When this trap was invented there wasn't really the adventure; there was the dungeon. I think this trap would be a part of the dungeon players would be likely to remember.