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5E Giant Boulder vs. Immovable Rod

jasper

Rotten DM
according to my bing search a 10 ft wide boulder would be are 21,875 pds but they depends on what stone it is.
 

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MarkB

Legend
Unless it's going incredibly fast, like, way more than 10ft/second, then they shouldn't need to save if the players actually say "we dodge to the side". If a player ums and ers about it, sure, an easy-ish save might be warranted, but the thing is 15' tall, so you barely even need to duck to avoid it, given it's a sphere, in a roughly square corridor, if you just move to the side, which, assuming the corridor is barely 15' wide and you're in the middle, takes under a second (just try walking 7.5'). If it's a total surprise and coming at level 30+ mph or something then a save might make sense, but 10'/second is 6.8mph.

This is kind of less of a trap and more of a feature.
And that's when they release the acid down the gutters in the sides of the corridor.
 

TheDelphian

Explorer
Does the boulder have to be solid?

Could be a lot lighter and still maintain some integrity.

just a thought to justify the players plan might work whatever the consequences to the rod.
 

MatthewJHanson

Registered Ninja
Publisher
The widest point would be at 7', which is over the heads of most PCs.
but the thing is 15' tall, so you barely even need to duck to avoid it
The thing about the 7.5 foot gap is that it's also infinitely thin. So would be crushed under the boulder, just between the boulder and the wall, which is not that much better. If you want even six inches of width, that reduces the height to under five feet of height, and if you want a whole foot of width you'll need a height of less than four feet. (I'd maybe be okay with a small creature managing it, especially since the only small creature in the party is the NPC kobold "guide."
I think lying down is more plausible, but still trying to situate yourself in such a way that none of you gets hit by a boulder passing over in the span of six seconds seems tricky enough to me that I think it's worth a roll.
(Here a graph of what it would look like: Desmos | Graphing Calculator
according to my bing search a 10 ft wide boulder would be are 21,875 pds but they depends on what stone it is.
So my math is that volume of a sphere is 4/3 pi r^3 = 4/3/ pi 7.5^2 = 1767.15. I googled what a cubic foot of granite weighted and got 168 about pounds. 168 x 1767.15 =298,856.
Does the boulder have to be solid?
It doesn't have to be, but I think it makes the most sense to be. (Though maybe there's something else fun inside.)
 



Bawylie

A very OK person
The concrete ball is hollow like a chocolate bunny.

That’s the only way this trap can get reset anyway.
 

Eltab

Hero
The concrete ball is hollow like a chocolate bunny.

That’s the only way this trap can get reset anyway.
The hollow rock is full of a magnetic liquid. Wile E. Coyote and an ACME Giant Magnet can drag the rock back up the slope. (Be careful about getting out after setting the hidden panel - especially if he is still carrying the magnet.)
 

Sabathius42

Bree-Yark
Real world story. I work in a warehouse. A "heavy" skid for me is 1500 or so pounds. I can move this around fairly easily with a pallet jack by hand, but it takes a little bit to get it moving. The wheels of the pallet jack aren't incredibly large and are coated in rubber.

If you somehow run over the SMALLEST THING (like, not exaggerating, a penny or computer screw) while moving that pallet jack the entire thing is IMMOBILIZED. No amount of brute force will get that 1500 pounds of servers up and over that penny. Its so ridiculous, but its true.

Unrelated to pennies and pallet jacks....if, as a player, I identified a trap and made a reasonable plan to avoid it killing me, I would expect the GM to render it safe or at least tell me that its not a guarantee that its safe before I trigger the trap. If the GM did a GOTCHA and ended up killing my PC off when the trap wasn't neutralized, then one of two things is going to result.

1. I don't want to play in that GMs game anymore.

2. If I do play in that GMs game I will check out of any scene involving traps. My character will go a different way (or even stay behind) rather than me interacting with the trap.
 


Al'Kelhar

Adventurer
...
Oh, oh, wait! Here's what you do...

Get yourself a big honkin' wedge of really stout oak, possibly bound in iron bands if you can manage it. Set it in the center of the corridor. Place the immovable rod against the downhill side of the wedge, and activate it. Yes, there will be more than enough force to deactivate the rod, but not before that rolling ball - that is traditionally only just big enough to fit in the corridor - will have tried to at least a bit roll up the incline, gotten several inches of wood under it, and wedged itself solidly in the corridor, unable to roll down.
"10' pole?"
"Check!"
"50' hemp rope?"
"Check!"
"Hooded lantern, flasks of oil, and some more flasks of oil?
"Check!
"Friggin' great big wooden doorstop?
"Ch.. wait, what?"
 

If you somehow run over the SMALLEST THING (like, not exaggerating, a penny or computer screw) while moving that pallet jack the entire thing is IMMOBILIZED. No amount of brute force will get that 1500 pounds of servers up and over that penny. Its so ridiculous, but its true.
Added to that, such a heavy rock would likely crumble under it's own weight, and quickly stop being a sphere, bringing it to a grinding halt. The difficulty isn't stopping such an object, it is keeping it moving.

A steel sphere would be more practical if you wanted it heavier, brass even better.
 



MarkB

Legend
A cylinder wouldn't be as likely to crumble as a sphere, but if it went even a tiny bit out of alignment it would wedge firmly against the sides of the passage.
You'd just need to add a raised curb to the sides of the corridor to act as a channel and keep it aligned.
 

Umbran

Mod Squad
Staff member
A cylinder wouldn't be as likely to crumble as a sphere, but if it went even a tiny bit out of alignment it would wedge firmly against the sides of the passage.
Look, dude, if you are going to go through the trouble of managing a single 300,000 pound rock for the purpose of squishing people, you can manage this.

What is the point of going through the work of that rock, and leaving huge gaping holes a halfling could just walk through?!?!
 

What is the point of going through the work of that rock, and leaving huge gaping holes a halfling could just walk through?!?!
Maybe I've been designing my dungeons all wrong. What was I thinking adding all those secret passages, treasures and easily escapable traps?! From now on all my dungeons will be hopeless rewardless death traps. :LOL:
 

Umbran

Mod Squad
Staff member
Maybe I've been designing my dungeons all wrong. What was I thinking adding all those secret passages, treasures and easily escapable traps?! From now on all my dungeons will be hopeless rewardless death traps. :LOL:
You miss the point - scaling the boulder up to that grandiose size is what makes it escapable, and thus foolish. Adding the size makes it a worse trap, not a better one.
 

Oldtimer

Great Old One
Publisher
This makes me think about the rolling boulder trap I had in a dungeon (used as a convention competion event) some forty years ago. The sloping corridor ended with a false door and touching it released the boulder. Almost all players realized the obvious way to avoid being crushed (round boulder in a square cross section corridor), but one group actually panicked and rolled repeated Open Door rolls (those where a thing in those days) until the boulder crushed their characters.
Oh, happy days.
 


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