We've all seen Boatmurdered and it's legendary lava system, but it can only really be replicated from within a hillside. How do we create a truly terrifying defense for a flat area that can dispense molten rock where it's wanted least by those we dislike?
For the answer, I give you the Doorstop. A Bunker design that is both compact, fortified AND can deliver lava in your preferred direction rather than a general distribution over the map
The screwpumps are locked in pairs that draw power from the level above and magma from the level below, discharging through fortifications so attacking creatures cant reach them.
Drawing from the axle in the top-left corner, power is distributed to one of the screw pumps in each cardinal direction and shared via the axles seen in the previous picture. The levers are place in an idiotproof design so you know just where your lava is going to come out. The corners are also Fortifications, so you can add insult to injury with marksdwarves.
Now, you may wonder how magma has reached the surface in the test site of Hamebalanced. Using a standard 'pumpstack' and an aquifer-driven power supply, magma is deposited in the large 3-level chamber shown below as a sort of battery to ensure there is always lava for those that deserve it most.
Although not shown as this is the level below the bottom of the Doorstop, magma is pumped from the lowest level of the tank up to this one, then drawn by the Doorstop magmaguns for discharge onto the surface. The square area the north and south screwpumps are filling is where the Doorstop pumps get their magma from
As with any successful device, it must be tested to make sure it works. Fortunately, we have test subjects ready and willing to melt for science!
subjects on their marks, we begin with a simple directional test. The West cannon is activated
Although slow, the lava is constant and has soon consumed Test Group Elf. The booze they brought with them exploding and burning probably didn't help. Oh well.
Test Groups One and Two, however, continues to approach the fortress with murder in mind for being told they were going to test adamantine weapons on fuzzy creatures and instead finding themselves in the Home Defense tests
Unfortunately, some of the intervening footage of the south guns being turned on for Group Two have been lost, but we did recover some footage of Test Group Troll
Meet Troll Subject Asno.
According to our remote sensors, she's proving our test of the Doorstop a raging success!
As our demonstration ends, I leave you with this;
edit: Slight change to the design, the control levers were moved to a room near the Dining Hall. Turns out the dwarves won't pull them when they can see goblins through the fortifications