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[slothen]

I'm considering the design of my fortress entrance.  My plan is to have a downward tunnel from the surface (3 wide) at a 45 degree angle, using channels/ramps.  Or I could build it at a 30 degree angle, alternating downward ramps with a single horizontal tile. I want to build a cistern and use pumps to pump water into the top of the tunnel.  My hope is that enemies will be washed down the ramp.  at the bottom of the tunnel ramp would be drainage, and a pit.  I don't need this to be 100% effective at capturing entire sieges, and it can always be converted to a drowning chamber, but I do hope that the water coming down will prevent enemies from climbing up the path, and ideally knock them into the pit.  I'm aware that you need water below 7/7 for it to flow and push enemies.


_____surface___________________
\  \       ------------------
 \   \    |       cistern       |           Pp=pump
   \   <Pp                       |
     \   \ ------------------
       \   \_______________________
         \___    _____traps_____ to fortress->
              |  |
              |  |<- retractable hatch can be closed to stop drainage, start drowning.
            |grate|    archer target practice room
              |  |
              |  |
            spikes/drainage



second idea, I think this would be much more efficient.

2 wide path in horseshoe shape.  Inside is a cistern.  On the outside of the path is a drop off or pit.  The cistern is blocked first by a wall of floodgates, and then fortifications.  Enemies crowd around the path, floodgates go up, gravity-pressurized water flows out through the fortifications and onto the path, washing enemies into the pit on the outside.

[Urist Imiknorris]

It looks like it should work. Try it and report back.

The water flow should be more than sufficient to prevent enemies from climbing back up.

[duckInferno]

Yup.  You don't even need to run it downhill

Code: [Select]

top-down

_______|  |
|      |  |__
|      X   ..|
|      X   ..|
|  c   X   ..|
|      X   ..|
|      X   __|
|______|  |
       |pp|

      entrance

c = cistern, pref. several Z's high with bottom level with entrance coridoor
X = floodgates
. = deep pit
pp = pressure plates linked to floodgates
Fill the cistern to the brim, link up the pressure plates, make a pump stack or something to drain the pit .

You can just let the intruders drown, or pump out the water at the bottom as it enters, or create a separate drain cistern separated with grates from the pit. 

[Uzu Bash]

I know the pump outputs enough pressure to kill a cat on impact with a retaining wall.

Now I wonder if it's possible to do that to fully armored adult goblins. How much pressure would it take to completely shatter them to component bits?

[Urist Imiknorris]

About 15 z-levels of free-fall.

[Hyndis]

You can also use water to push things off a ledge. On one side of the walkway have a row of pumps (behind fortifications to protect from building destroyers) and on the other side have a pit. You'll want a cistern feeding the wall of pumps and some way to drain the pit, but the flow of water will push everything off into the pit, where it will either explode upon impact or drown.

Disadvantages:
It works on caravans and migrants.

Advantages:
It works on caravans and migrants.
Kobolds and ambushes are not immune.

[Uzu Bash]

Could this be done with horizontal pressure? Does surplus power of the stack make a difference in pressure, and if so, would it be enough to shoot them like a projectile against a wall?

[slothen]

I know the pump outputs enough pressure to kill a cat on impact with a retaining wall.

please elaborate

[Uzu Bash]

If I let the water blast at the top of my pump stack, it'll spray out like a shotgun, so I added a wall at that z-level so gravity will bring it down. A cat crept in after I finished some repairs, so I tested it with the cat inside. The water hit the cat, the cat hit the wall, died on impact.

[slothen]

edit: accidental double post.

[slothen]

Yup.  You don't even need to run it downhill

i want to try this because if i put the water at one end of the corridor and a pit at the other, i'm concerned the pumps will pump too fast, and one end will be filled with 7/7 water and drowning goblins before the leading wave of the water even gets to the pit.

[thehippopotamus]

I like the looks of this, I've been considering doing a similar trap for a while and look forward to some positive results... now if only I can get off my ass and try one... I just keep getting sidetracked by OCD residential quarter design.

[slothen]

Yup.  You don't even need to run it downhill

Spoiler (click to show/hide)

Code: [Select]

top-down

_______|  |
|      |  |__
|      X   ..|
|      X   ..|
|  c   X   ..|
|      X   ..|
|      X   __|
|______|  |
       |pp|

      entrance

c = cistern, pref. several Z's high with bottom level with entrance coridoor
X = floodgates
. = deep pit
pp = pressure plates linked to floodgates

Fill the cistern to the brim, link up the pressure plates, make a pump stack or something to drain the pit .

You can just let the intruders drown, or pump out the water at the bottom as it enters, or create a separate drain cistern separated with grates from the pit.

2 things, there's a delay on floodgates, and pressure plates will send an off signal as soon as something steps on them.   Do you often get problems with this?  I would think that if an ambush walks through this trap the floodgates would end up out of sync with the pressure plates.  Does this require a backup manual "close" lever?

[Shoku]

Ah the old high pressure shooter topic. Back in the 40d days we had a ton of veterans always spouting off about how pressurized water doesn't push things around- that hasn't changed has it?

If you want to make sure the water drifts about one pump per five to seven tile wide opening should output the right volume of water. May need to delay it slightly so that the initial water in the cistern can make it's way out though.

[LoSboccacc]

Yup.  You don't even need to run it downhill

..snip..

Fill the cistern to the brim, link up the pressure plates, make a pump stack or something to drain the pit .

You can just let the intruders drown, or pump out the water at the bottom as it enters, or create a separate drain cistern separated with grates from the pit.

you really want fortification in front of those floodgates, as the Unfortunate Accident With Dragon shown me.