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[melphel]

I got tired of stabbing, slicing, smashing, crushing, and melting my enemies, so I decided to try out something new...Freezing the little buggers in ice!  I can't get it to work though...

The basic plan is to melt the ice out from under the enemy's feet by pumping magma up under it, then letting the magma fall back down to have the water freeze.  This way the "moat" can be thawed and refrozen on command by toggling the pumps.  In theory it resets itself, no need to dig out the blocks of ice between waves of enemies.

Setup looks like this (side view)

Code: [Select]

z 0  _______[fort wall]
z-1  IIIIIIIIIIIIIIII
z-2  .PP....IIIIIIIII
z-3  MMMMMMM
I=natural ice wall
P=pump
M=magma
.=open space
The ice on z-1 is on a constructed rock floor, so it won't fall down into the magma when it melts (made that mistake the first time around).

After much work, I have the magma reservoir and pumps set up, but now I've hit a road block.  I can thaw and freeze the ice one z-level up just fine, but I can't thaw the floor above that one the surface (z0).  I've thought of pumping the magma up one more level to be right under the surface floor, but then once the floor melts, it will fall into the magma.  Which would not only leave a hole into my fort, but wouldn't leave any water to refreeze around the enemy.

Any ideas on how to get this to work?  Or is this approach not plausible?

[Vattic]

If the ice on top melted this would be much simpler than my ice trap.

I'd imagine ice floors would smash through floors bellow if dropped? If not you could use bridges around the edges so that the ice has no support when their foundations are melted. I think they will fall, puncture the floor bellow, and let the water solidify your magma.

[Tevish Szat]

You need to have the magma next to the ice you mean to melt.  however, there can be a "thin" barrier, like stone, or a constructed floor on which the ice/water sits, between them to prevent just obsidian-casting.

Try this...

Z+0 IIIIIIIIII
Z-1 .PP.......
Z-2 MMMMMMMMMM
The ice in pink should melt, the ice in yellow might (not sure), and the ice in teal shouldn't (but might!  don't quote me on that...)

I've done shamefully little work with magma and ice, though, so it will take ‼science‼ to confirm

[Vattic]

The problem he is having is that when ice is melted from bellow it leaves behind ice floors above.
So this:
             < surface (ice floor)
##########   < ice (stone floor)
             < empty chamber

Becomes this:
             < surface (ice floor)
≈≈≈≈≈≈≈≈≈≈   < water (stone floor)
≈≈≈≈≈≈≈≈≈≈   < magma filled chamber

[Tevish Szat]

Hm...  Channels?  if you channel out the ice floor while it's all solid, is there any ice left below to melt?

[melphel]

Sorry, my diagram wasn't clear enough.  I DO have a floor under that ice.  The first time I turned this on I didn't have floors and one of the guys at the pumps below got encased in obsidian.  I built a floor on the ice level and brought in more water and let it freeze, which was harder than it seems.  I can now melt that ice layer just fine without anything dripping into my magma, but the surface ice ABOVE that remains intact (Vattic's diagram is spot on).

I don't really want to let the surface floor cave in either.  If that takes out the constructed rock floor, that tears a hole into the fortress and prevents the moat from being reset.  If it doesn't punch through the rock floor for some reason, the water will still spread out under the bridges and then when it refreezes, it will create an ice wall that would support the surface ice floor...so I'd have to mine out the ice under the bridges before being able to trigger this thing again.

It might not be possible to have them drop into the water the more I think about it.

[Girlinhat]

The floor directly above magma is warmed, that Z+1, what you're describing puts the melting zone at Z+2 and will not work.  You need the method Tevish laid out, where you have a shallow basin of water (2/7 to prevent evaporation but allow pathing) held up by a constructed floor.  On the direct level under, magma should be supported by a bridge.  To engage the trap: activate the bridge, dropping the magma and causing the liquid water to cool and freeze.  To disengage: Push magma back onto the bridge, melting the ice in 7/7, and drain it so that it can be reduced back to 2/7.

If you have a solid ice area atop of constructed floor, you can push magma under it to cause flash melting, which will stop goblins and such easily, but it will not stop fliers or amphibians, including goblins riding giant toads.

[melphel]

I did a little testing and found out that wouldn't work.  If water is less than 5/7 when it freezes, it does not create a wall.  I put a puppy in some 2/7 water and let it freeze, and all that happened was there was an ice floor under the puppy.  Even if I got them in there and froze them, when I thaw out the walls, there will be an unsupported floating floor the z-level above that.

[Girlinhat]

Really?  That's against my own experience and hearsay, but that's interesting, may have to science that.  My own attempts with ice have usually been a bit messy, can't say for sure I was counting depth right all the time.  Either way, you can freeze a moat, replace one tile with a constructed wall, place a pressure plate upon this wall, and link the plate to the magma.  Then, when approaching, the goblins will hit the plate, the magma rushes in, the ice melts and they fall into water, and then the magma rushes out and they freeze solid.  Miners and/or remelting can then retrieve goblinite.

And that's how you "mine for iron" in a glacier!

[melphel]

I kinda cheated and used dfliquids to do the puppy cyrogenics experiment, so maybe that had something to do with it.

But anyway, I think I have a way to melt the floor underneath them and not just the z-level of ice below.  If ice melts when there is magma in an adjacent tile in any direction, I can't melt the surface floor by pumping magma into z-2, but I CAN melt the surface floor by pumping magma into z+1!  If I build a container above the surface to hold flowing magma and have magma pumping into z-2 at the same time, I should have that sudden drop into ice water I've been looking for.

Atomsmashing works on magma, right?  I could use that to wipe out the magma on z+1 quickly without having to wait for it to flow/evaporate and get that flash freeze in.  A bit wasteful, but I can always pump up more magma.

...Although it just occurred to me that the surface ice floor might melt into 7/7 water...

[Girlinhat]

Ice melts int0 7/7, yes.  Magma does seem to melt in adjacent directions, but only 1 tile.  Ice, a wall, and then magma, will cause no melting as the magma is adjacent to the wall, not the ice.  However, magma above ice should work, as evidenced by murky pools.  When digging my surface forts, I tend to put a small area underground as a basement, for underground farms, booze storage, and early workshops before I can set up the outer walls.  When doing so, I often build on Z-2 to avoid murky pools, and I get digging cancels because of the murky pool above the digging site.  This seems to imply that magma would heat up things under it, because moist walls and warm walls seem to function identically.

You should be able to build a whole floor of floodgates or doors above the ice, open them all so the area is clear, and then drop magma.  This will cause melting of the ice.  Closing the floodgates will atom-smash the magma and cause instant freezing.  Because of the way floogates work, you could simply have a magma reservoir above the machine, directly linked.  Opening the floodgates will drop magma, and closing them will destroy it AND prevent more from flowing in, making for a simple setup.  A more complicated setup could be used to drop exactly 2/7 magma onto the melting plate, to conserve liquids and plumbing/FPS concerns, but would not be entirely difficult to set up.

[melphel]

Well I know walls melt into 7/7, but if floors do the same, that might throw a monkey wrench into the works.  If z0 suddenly had a significant amount of water in it, enough to flow beyond the area heated up by magma on z+1, it might freeze into ice walls around the whole area and block it all off until I go mine it out.

I really want a trap that doesn't need mining or anything extensive to reset.  I'll try it out tomorrow and see how it goes.

[Girlinhat]

I don't believe so, but I don't think ice floors are lethal anyways...

[Roraborialisforealis]

I remember one trap I made that was just a buncha mined ice on the floor, when I ran water over the ice the room would freeze. I could then mine the dead foes for the ice back + Their butchered corpse and gear.

[Girlinhat]

Wait, just ice boulders, and then flood the boulders with regular water?  That's... well, kinda...  hmm...  If the area was outside, then it would freeze water anyways, but then the water would freeze solid in the pipe and not spread anywhere.  If it was warm enough for water to flow, then the ice boulders would just be water.  What?