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[Boatmurdered]

So I've been playing my first serious fortress, and decided that since I embarked near a magma pipe, that my next project would be to dig out a big room, and flood it with Magma and Water, endlessly farming the Obsidian. Unfortunately, I do not have access to Bauxite, so I'm stuck using the method I found here.

My problem is what to do when I need to remove the water. According to the link, I need floodgates on both levels of the farm, although I cant imagine needing the gates on the second Z-level. The other thought I've been having is: where should all the water go? I've considered making a large room a few more Z-levels down to dump the water in, so that it only reaches 1/7 deep, and evaporates, but I dont know how good of an option that is.

[Pigtail Cloth]

Closed(forbidden/lever) doors can stop water and magma, but once you open them in magma they are gone. In water you have to wait for the water to go away before you can close the doors again.

You only need 1 depth water and 1 depth magma to make an entire block of obsidian though.


Edit: also, watch out for the elephants 

[NW_Kohaku]

I'm going to assume you have some kind of infinite source of water, like an aquifer or a river, since that's pretty much required for serious obsidian farming, and that your water comes from that source.

You can make a cistern, but that would eventually fill up with water, unless you make a VERY large basin and ensure that all water has evaporated before you work the farm again.  A better solution is to just pump your water back into the source you took it from in the first place.  (See pump stacks.)  If you pump water so that it falls into a river from above, the river will carry water away until it hits its natural z-water-level, while oceans and aquifers will absorb infinite amounts of water.

[wagawaga]

The rule for melting stuff is the following:"Anything will be affected by magma only if it and the magma are on the same tile". Adjacent tiles do not count.

This applies to doors, floodgates, hatches, pumps etc and to all attached mechanisms.
To avoid a door breaking all mechanisms inserted in it and the door must be magma-proof(that means bauxite-only mechanisms in vanilla).

The only exception is when the object considered is made of wood, in that case being near to magma (still unsure how close-for how long) will cause it to burn after a brief time.


About disposing of water:

I think you better change the method slightly.
Make a large chamber, 3 z-level high.
On bottom level you put magma in.
Middle level is empty.
On top level you let water in, and the whole floor is replaced by a lever activated-brigde.
When both bottom and top chambers are full, close floodgates and pull lever to open bridge.
Thus water gets dropped on magma, hopefully leaving no excess.
Then lower bridge and open access shaft.

EDIT: I just noticed the page you linked to was named "no-bauxite" obsidian farming, so I assume you have no bauxite.
Instead of magmaproof floodgates with bauxite mechanisms, you can use this design:

Spoiler (click to show/hide)

Code: [Select]

# wall
M where magma comes from
m where magma should go
pP pumps, uppercase means output tile.
. channeled area
+ floor
g gear assembly that provides power to pumps

z-level 0
######
##..##
#gpp##
##PP##
mmmmm

z-level -1
##MM##
##MM##
######
######
######

As long as pumps aren't made out of wood this design will work fine without need of bauxite (make pipes and corks out of metal, any metal is good).

Toggle the gear assembly to "open/close" this pseudo-floodgate.

[NW_Kohaku]

I think the one he linked to should work fine - it assumes that water will pour in, make obsidian of the magma below it, and the next wave of water will keep on chugging forward, until all the tiles are magma-free.

He simply needed a place to put that extra water once everything was obsidian, and pumping it back to its source is the simplest method.  If he's using flood gates that only ever touch water (once the bottom floor is all obsidian), then he shouldn't need metal screw pumps, either, since it's just water touching it.  I actually wonder what the purpose of the bottom floodgates would be, since water should only ever be on the top floor, but I guess it would be if you for some odd reason released the water prematurely, and needed to clear out the puddles.  Just make sure that bottom floodgate is NEVER open when magma is in the chamber, or you could have quite a problem cleaning up the mess.

[wagawaga]

The problem with the linked page's method is that after digging out obsidian you will end up with puddles of water, and if there are puddles of water near the magma intake then as soon as the magma enters the bottom chamber it solidifies and blocks more magma from entering.

[Grendus]

I thought of a way to do this a while back. I've never tested this, every time I try to play with magma I have bauxite, but it should work. What you need to do is dig out a room to cast obsidian, and dig out a room above it (with a little extra over the tunnel the magma comes through, you'll see) in the exact same shape. Channel out the upper room and fill it with drawbridges, then connect it via floodgate/raised drawbridge/door/hatch to your infinite water source and fill it with water. When the lower room is full of magma, close the water tunnels. Then open the drawbridges on the upper room, instantly casting the entire mold. The trick is, because the two rooms are the exact same shape, there's no water left over. So long as you never mess up the levers and always seal the water tunnels before you dump water on the magma, you don't need drainage.

Now for the clever part. You have no bauxite, so you need something magma proof that can be placed and removed at will. Remember how I told you to dig the upper room so it overlapped your entire magma chamber and a few squares of the magma tunnels? That will be cast into rough hewn, completely magma proof obsidian walls. When you're ready to make more obsidian, simply channel out those extra walls from the floor above and let the magma in. Should work like a charm, obsidian farms without bauxite.

[Dorf3000]

My problem is what to do when I need to remove the water. According to the link, I need floodgates on both levels of the farm, although I cant imagine needing the gates on the second Z-level. The other thought I've been having is: where should all the water go? I've considered making a large room a few more Z-levels down to dump the water in, so that it only reaches 1/7 deep, and evaporates, but I dont know how good of an option that is.

To get rid of excess water there are 3 main ways, they are:
1) drain off the edge of the map.  This can be underground with fortifications or on the surface.  It depends where you dig the obsidian farm if this is a good idea or not.
2) evaporate.  You need a large room underground, much larger than your farm, or pump to the surface.  Again it depends where you put your farm if this is a good solution.
3) add more magma!  Probably not the best solution since you're building an obsidian farm with no bauxite, although you can do this with the design you are using.  You'll probably have to channel out the magma entrance several times until the water is mostly gone.

The best solution is to control the amount of water you can put in, usually with some kind of cistern or storage room that holds a fixed amount of water and can't be open at both ends at once.

[Ashery]

Bladeshoots uses the precisely measured water drop to leave no remains. If I were to design a farm without bauxite, I'd use pumps with hatches over their intake tile. It accomplishes the same thing as the gear assembly method wagawaga showed, but it looks neater and takes less power
 
You still need to have some type of emergency drainage available, though, as chances are you'll screw up with the levers at some point and flood a farm (I've had three such mistakes in my 200+ batches (100ob each batch), usually when sleep deprived). Better yet, have an emergency water cutoff lever outside of the farm in case it floods and your levers become inaccessible.

Grendus' method also works, but I'm too paranoid to trust my miners to channeling the magma cap safely.

Here's the method I used for Bladeshoots. As was mentioned before, just replace the bauxite bridges with non-wooden pumps and control their flow through either a gear assembly or some hatches. I've definitely made mistakes with the design I used for Bladeshoots, though. Most notably, the dwarves have access to all four sides of the level above the magma. This became a problem due to dwarves pathing through the farm while it was filling. Adding in restricted traffic zones and tearing down the ramps up to two of the sides prevented most dwarves from pathing through (Only problem is the occasional dwarf sidestepping in due to high traffic), but pets still regularly die as they ignore the traffic designations. Another big one is that I built the control levers in the farm itself to allow for easy management. That's all well and good until you flood the farm and can't cut off the water feed, heh.

Also, from experience, 1/7 puddles of water just evaporate when they come into contact with magma. I ended up trying that out after I flooded one of my farms and the magma flowed in just fine.

[Hyndis]

I dig out narrow but long runs for obsidian farming.

I also construct walls on either side of the magma channel, mostly just so I don't accidentally have them dig into the rock I want them to leave alone.

The channels usually go from the magma pipe across the entire map to the other side. I have just a regular dwarf powered pump that will pour in water from the very top near the magma pipe. At the end of the channel I have fortifications carved into the edge of the map so any excess water can drain off enough that the water can evaporate.

Each production run takes about a year from start to finish, but yields massive amounts of obsidian. I have massive stockpiles set to accept only obsidian, so as its mined its hauled up from the channel to allow for more production.

Once the water has mostly dried up I get my dwarves busy carving the entire thing into ramps. The blocks are then hauled away. I also use the obsidian for engraving practice, and put my engravers smoothing the top of the newly formed obsidian as well as the empty basin once the miners go at it.

Each production run is a massive undertaking, mostly just due to all the hauling required to get the obsidian out of the basin so I can refill it with magma, and the amount of rock produced from it is staggering. Easily several thousand per run.

I usually have two of these working in parallel, so that while one of them is being filled with magma or cooled with water, the other is being mined out. I then alternate back in forth so there is always one in production.

[BigD145]

About disposing of water:

I think you better change the method slightly.
Make a large chamber, 3 z-level high.
On bottom level you put magma in.
Middle level is empty.
On top level you let water in, and the whole floor is replaced by a lever activated-bridge.
When both bottom and top chambers are full, close floodgates and pull lever to open bridge.
Thus water gets dropped on magma, hopefully leaving no excess.
Then lower bridge and open access shaft.

EDIT: I just noticed the page you linked to was named "no-bauxite" obsidian farming, so I assume you have no bauxite.

You can still work the 3 level system by having an "overbite" on the water chamber. Dig a shaft over where the magma comes in, which you're likely to have anyway if you're channeling out a wall to initially open the bottom level. Make a tiny lock with a floodgate and floor hatch that can be filled with excess from the main water chamber and you've got yourself a water+magma=obsidian plug that can be dug out again.

[wagawaga]

I thought of a way to do this a while back. I've never tested this, every time I try to play with magma I have bauxite, but it should work. What you need to do is dig out a room to cast obsidian, and dig out a room above it (with a little extra over the tunnel the magma comes through, you'll see) in the exact same shape. Channel out the upper room and fill it with drawbridges, then connect it via floodgate/raised drawbridge/door/hatch to your infinite water source and fill it with water. When the lower room is full of magma, close the water tunnels. Then open the drawbridges on the upper room, instantly casting the entire mold. The trick is, because the two rooms are the exact same shape, there's no water left over. So long as you never mess up the levers and always seal the water tunnels before you dump water on the magma, you don't need drainage.

That's exactly what I tried to say in my first post.

[Hyndis]

I just use iron pump towers to get the magma from one place to another. No mechanisms needed at all. Normally I just dig out the bottom most level on the map and just let gravity do all the work for me. The magma flows on its own without needing any pumping.

Water uses a vertical shaft with a pump at the very top to dump water in. Just a small shaft, maybe only 2 tiles wide or something. Then a couple pumps up at the top linked up to a river or brook. I turn on the pumps when the magma needs to be cooled into obsidian.

Once its been cooled and the water has mostly drained away/evaporated enough that the dwarves can get to work, and they usually can get to work almost instantly because it'll only be about 2/7 depth, they start carving it up into ramps and hauling the obsidian away.