- Mine, don't channel. Channelling out the shaft takes a ridiculously long time and is dangerous for your miners. Just mine out the shaft and drop a floor from above when you are done to break through all the floors. You can mass designate the shaft by holding down the mouse and going up and down in long z-level columns. Designating 150 z-levels takes around 5 minutes, and digging takes less than a year with 3 miners
I tried this. I mined out rings around the piston and then collapsed a floor above onto the top of the piston. However, the piston didn't collapse when the floor hit it. I believe the piston was being held up only by floors. Can someone please elaborate on what conditions the piston must satisfy so that it will fall and break the floors when the floor above collapses onto it?
It took me a bit to get that as well. There may be an easier way since my method was more involved than the piston itself but here it is:
Step 1: Decide how big you want to make your piston. Make sure that you have a plan on how to get magma into the bottom of it though don't do that yet. Note that you'll also need at least three floors of earth above where you'll want the magma to go (those who are VERY Dwarfy can find a workaround that one).
Step 2: Mine a ring around the piston to be along every floor of the piston. in the end, you'll have a ring from the very bottom where the magma will go all the way to one floor ABOVE where you want the magma to end up.
D = mined out spot
Top view:
DDDDDDD
D D
D D
D D
DDDDDDD
Side view:
D D
D D- Where magma will end up
D D
D D
D D - Bottom
Btw: Count the number of spaces you dug out in one floor. Add 2 to that number. That's how many Magma-safe Floor Hatches you need so start making them.
Step 3: Listen close to this one. TWO floors above your last dug out area, channel out a room that's the size of piston-to-be and DIG make a ring around that as well.
Top view: (C = Channel, D = Dig)
DDDDDDD
DCCCCCD
DCCCCCD
DCCCCCD
DDDDDDD
Side View:
DCCCCCCD
D D
D D- Where magma will end up
D D
D D
D D - Bottom
Step 4: Plop a Support somewhere on that top most ring you just made. Stick a lever somewhere within reach and attach the support to the lever. AFTER this is done, Channel around the ring. The result is this:
CCCCCCCCC
C
DDDDDDDC
C
DCCCCC
DC
C
DCCCCC
DC
C
DCCCCC
DC
C
SDDDDDDC
CCCCCCCCC
(Bold and underlines done for easier reading. Note that the Support, "S" can be on any spot of the dug out area)
Note: If a dwarf gets stuck, use a floor hatch to let them escape. You may end up losing the hatch when it's over though but don't worry (remember how many I told you to make? It was 1 more than you really need.
).
Step 5: Go one floor below and you'll see a newly made room with a ring of natural wall side it. Dig out that ring so you have this
DDDDDDDDD
DDDDDDDDD
DDDDDDDDD
DDDDDDDDD
DDDDDDDDD
One big open room, below the top floor with the Support and above the rest of the Pillar-to-be.
Step 6: Evict ALL dwarves from the pillar area. Hatch over the stairs and lock it if you have to.
Step 7: Pull the Lever
End Steps
The result: that dug out ring with the Support at the very top is being held ONLY by that support. Without it, it'll cause a cave in crashing through the open floor below it, then below every dug out ring all the way to the Bottom.
If it goes well, you'll have Two floors of open air, followed by a large block of earth surrounded by a ring of open air all the way to the Bottom. Congrats, you now have your Piston.
To do the final setups, Make some flooring one floor above the piston, put up a Support (and link it with a lever) where the piston starts so it's attached to the floor, and set up your hatches one floor BELOW where the piston begins. Result:
Floor Above: (F= Floor, O = open space)
OOOOOOO
OOOOOOO
OOO
FOOO
OOO
FOOO
OOO
FOOO
Next Floor: (G= regular Ground, S = Support)
OOOOOOO
OGGGGGO
OGG
SGGO
OGGGGGO
OOOOOOO
Floor under That: H=Hatch
HHHHHHH
H H
H H
H H
HHHHHHH
AFTER this is done, go to the very bottom, dig out that whole area and pump magma into it. Meanwhile, once all dwarves are away from the area, put Walls up to completely seal the floor with the Hatches and make sure there's no openings or stairways. Remember, there will be magma in there in a minute.
After all that, Pull the lever.
If it works, you're done. Congrats on your piston!
(note, I found that when I did it, I ended up with a room of magma that was 3/7 or 4/7 filled since the room the magma goes into is bigger than the amount that was pulled up. It looks like I'll have to pool up the magma somewhere. Small detail when I just dragged it up 50+ floors with FAR less resources than a mass pump stack.
Btw: if the above seems a mess and dangerous, it's FAR less dangerous than simply channeling the rings out since the miners WILL end up causing a cave in at some point unless you, manually tell them to channel out one floor at a time. Thus channeling is either A LOT more dangerous or a LOT more tedious.