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[Girlinhat]

I suppose this should technically be a magma-tower?  Or a lava-tower since it's above the surface?

Regardless, here's the situation.  I'm preparing for aggressive construction, building my tower upwards to the sky.  Given the scale of this (roughly 44,000 units of construction material, not counting furniture) I'm trying to go big, as opposed to broke.  It's now occurred to me that I could manipulate a lot of magma, through various abuse of pump stacks and windmills.

Here's the plan:
Pump stack, running down to the magma sea.  In this map that's ~80 levels, requiring 800 power and somewhere on the order of an 8x8 region of windmills (64 windmills consuming 24x24 floorspace, where my tower is 21x21 wide).  This will have a few options to it.  Namely, with the flip of a hatch and a few floodgates, it can pump water up from the caverns, which will support a staggering ~120 4-way waterfall, as well as probably some amount of overflow off the edges to allow for fanciful cascades over the edges of the tower.

Flipping the switch, the water supply is cut off, hatches open, magma pours up through the very same pumps (probably iron, I have a lot of that, maybe steel).  It pumps up into a sleeve around the top of the tower.  This 'sleeve' will be an additional layer, much like a thermos, where the tower sits in the center, the inner wall, a layer of magma, and then the outer, main wall.  This will give it a traditional "belltower" shape where it has the mace-head shape at the top.  Nested here, I'm approximating 10 Z's worth, it should contain about 880 units of magma at 7/7 depth suspended 90-100 levels above the surface.

In action:
This should allow me to flip a lever, opening a hatch at the bottom of the magma-tower, and drop magma down 90+ levels, to where it will shoot through a series of tunnels and the hopefully pressurized magma will shoot up, creative artificial volcanoes across the map and bubbling up exactly where I command via a series of hatches and floodgates.  My 3x3 embark is 20,736 tiles total, so I don't nearly have enough ammo to flood the entire map, but I can certainly trap some sieges and purge the map of that pesky grass shit.

The problem:
How does magma work under pressure?  If I have an active pump stack within the magma-tower, will it pressurize the magma that exits from an open hatch on the other side of the tower?  Also, what's the best way to submerge a pump-stack?  Taking hints from the aimable magma cannon that was created earlier by submerging a pump stack in a magma vent, I've decided the best way to reload this monstrosity is to submerge the stack and power-feed it.  Since I assume this is impossible to do in the actual magma sea, I'm likely to have a group of extremely over-worked pump operators pulling from the sea and into a massive cistern.  Also also, will a pump fill up beyond its level?  If I have a pump at the bottom of a 10 level cistern, will it fill up only the bottom, or will it fill above and over the top?

Thoughts and suggestions are greatly appreciated.

[bobhayes]

I am not a lava expert but I seem to remember reading that lava doesn't get pressurized by height, only by pumps - it will flow down your system beautifully but won't flow back up.

I am sure you will find some workaround, however - maybe mini-pump stacks scattered around the map with their own subterranean DWR network, with configurable 9-way outputs so that you can drop lava on most tiles.

But if you're going to do it, then you really ought to double pipe the whole thing for water rather than having it be one or the other. Sometimes you might want to drop blocks of obsidian on things or drown/water-push them instead of just burning them to death.

[Hyndis]

Magma can be pressurized, but only if it runs through a pump. Sometimes it also acts semi-pressurized when in a volcano. Its sort of weird. When pressurized it works exactly like water.

Easy way is to just make an enormous cistern and fill it with magma. Have iron bridges with iron mechanisms at the bottom. Pull lever and the entire thing will dump out almost instantaneous on whatever is below. If the map is small enough and the cistern is big enough it will cover the entire map with magma, cleansing it.

[Girlinhat]

I can make concessions for obsidian later, but right now the idea is to load the magma, let it sit, and use the water the rest of the time.  A separate section for casting obsidian could be constructed, probably above the actual reservoir, but the issue I have is that obsidian is hard to aim.  It doesn't move very far, while the magma could.

I'm aware of magma and pressure, which is why I'm curious about pump stacks and their proximity to the magma.  If this fails, then I'll be adding a pump on the level bellow, which drops magma directly outward, to ensure that it is pressurized.

Ninja'd: I don't want to drop magma.  That's too easy.  I want to channel it through the ground itself.  Make the earth shake and spew forth its burning vomit upon the heads of those pretentious elves who feign to try and besiege my outpost!

[Brandstone]

As long as the magma has a screw pump it will pressurize like water. As long as the magma in the wall is still connected to the pump stack and the pumps are still going, then the magma will come out your holes on the surface. The magmafall may present a problem, but I know water stays pressurized through a waterfall(tapping the bottom of a 20+ z-level waterfall teaches you some things about pressure) so magma should too.

[Misterstone]

If you want magma to come out of the ground, you have to have a pump above ground feeding magma into a u-bend, and the magma will rise up to the level of the pump if there is enough of it, if I understand correctly.  So you'd need to build a magma tank or something like you described, then a u-bend that goes under ground and has one opening on the surface, the other end inside the tank.

[Girlinhat]

The basic idea now, is to build the cistern at the top, and then a narrow, 1-3, maybe 9 wide drop from the cistern to the ground, enclosed with some fancy type of material so that it's not exposed to outside air.  This goes down, underground about 5 levels, and links into the tunnel network for eruptions.  The screw pumps that push the magma into the cistern will remain on during this time so as to sustain pressure, although their source will be cut off so that they don't overflow the tank.  This should sustain pressure, and allow it to go down, and then up again to make a 100 tall U-bend.

I think for added Fun, I'm going to build special out-spouts, or perhaps only one massive outspout.  The current idea is to make a hollow 9x9 tower, with a 7x7 platform above it, built to overhang the pillar a little and sorta make it look like a tree, with magma pouring up through the hollow center and out across all sides.  Possibly flood-gates to enable some directional aiming.  Alternative idea is something golden and phallic that erupts magma.

[gtmattz]

This setup has one thing to be concerned about that I can see, and that is that the shared parts of the system will need to be completely dry of water/magma before letting the magma/water in, or you will have chunks of obsidian gumming up the works wherever a stray 2/7 tile of water meets magma.

I was responding to the setup in the OP, looks like things have changed.

[Girlinhat]

Things have not significantly changed.  There will still be a shared pump stack, and allowing time to dry will be permitted.  Namely, by letting the pumps run dry for a while.  This will suck all the water up into the fort, over the mist generators, down into the cavern, and NOT back into the loop, because a floodgate will be closed.  After just a little while, the system should run dry and allow magma through.  Repeat for magma, letting it run dry and evaporate what's in the pipe, before changing over.  A bit of micromanaging here, watching for pools of stuff, but nothing abnormal.

[gtmattz]

Sweet, sounds like you have it all sorted, should prove to be mega awesome, even if a little (or maybe a lot) laggy 

[Girlinhat]

Probably have to disable temperature during the loading phase, simply for quickness's sake, but I'll be attempting to use the improved pump stack with the 3x3 mini-reservoirs and leaving temperature on.

Actually though, I have an Adamantine mound in front of my fort, as a big show of bragging to passing merchants and for some reason a handy place to spot elves.  They tend to go over the mound's many ramps, and get spotted.  I might hollow or relocate that, and use it as the spout.

[EveryZig]

My current map comes with what might work as a pre-made spout: a volcano that extends to 9 or so z levels above the peak of the mountain it is part of (no other terrain around it, just a 1 tile thick obsidian shell filled with magma). It's pretty strange to look at.

[Girlinhat]

I wonder how magma reacts when suddenly pressurized?  As in, have a large reservoir of magma, and have another reservoir above and to the side, with an active pump.  Suddenly remove a floodgate and connect the two.  Will the lower cistern suddenly bubble over?

[Valkyrie]

As I understand it, magma only gets pressurized in a very limited sense.  When a screw pump is moving a tile of magma, it picks the output location following pressurized-water rules.  After that, however, the magma acts unpressurized.  So a artificial volcano would erupt if a screw pump is actively pumping magma at it (potentially via a U-bend), but pumping magma to a high z and dropping it shouldn't yield pressurized behavior.

[Girlinhat]

Yet there's no difference between a U bend and a drop, really.  Basically, the side view is this:

Code: [Select]

W~~~~W
W~~%%
WWWWW
  W
  W
WWWWW WWW WW
WWWWW     WW
WWWWWWWWWWWWSo, it's pressurized from the pump, going down, and then U bending.  Does this change if the magma-fall is enclosed with walls to make a pipe?