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[gchristopher]

The basic unit is a 1-wide tunnel. You can make them in a bank (you need a perpendicular water supply pipe 1 level up). In the tunnel is a pressure plate set to trigger on hostiles. Friendlies will therefore travel right through without a problem. The plate is attached to three hatches. Two are fore and aft over holes in the floor. Right above the plate is another hatch, holding back the water supply. Gobbo clicks on plate, opening all three hatches, and is then flushed through a hatch. If there's no drainage, then the gobbo's drown. I made a 1x3 space under the plate, with a 1x3 bridge on the bottom for occasional collection of the trap contents.

That would be very neat if you got it working reliably. Have screenshots or a diagram?

How's it stand up to building destroyers? Wouldn't they target a hatch before reaching the pressure plate? (At least Trolls for a siege. Titans/FBs might be harder; they're strong swimmers.)

How sensitive is it to degree of pressure in the water source? i.e. Does it require flow, so you'd have to limit the rate of inflow from above?

How's it hold up to things that try to climb back out, since the trench is only 1z? Is it manually reset if used as a drowning trap?

[Reelya]

Well a sideways cross section would look like this for the basic set-up:

Code: [Select]

XXX#XXX
  _^_ 
XX___XX
^ = plate, # = water source held back by a hatch
_ = floor hatch, ___ = bridge (for clearing)

Further along the tunnel you need some drainage grates or something to clear excess water.

once on the plate, the hatches open and water buffets the creature. Swimming ability shouldn't help them. They just get dislodged before they have time to do anything. When they're dislodged, they fall into the hole, then the hatches close. So there's no "climbing out" going on.

I never had a problem with flow. The flow continues until the creature is no longer on the plate, then the hatches close. You just want to make sure there's good pressure. The 3x1 cavity below the hatches quickly fills with 7/7 water and all the excess goes sideways. That doesn't stop 100% of enemies going into the holes however. Not sure about how flying enemies would go though.

building destroyers don't target a closed hatch if they can walk over it. So they'd only target the hatches once it opens. But they get dislodged before being able to do that, and once in the hole, they have hatches above them and a bridge below them. I don't think they're allowed to target either one.

As to what else you connect to this basic design, well that's down to imagination. But it's very effective and completely automated. Obviously you need countermeasures for FBs, but you'd need that with cage traps anyway.

One idea would be to have multiple levels of bridges underneath the bottom trap. e.g. top level is drowning, then they drop to a drying level. Under that, a drainable magma level. So you have near-automated capture, death and disposal, with cleaning of goblinite.

[ToastGoats]

I don't know if these will work with the things and time I have.

I'll share some info.

1: My fort in built on a hill, there is an entrance on the top of the hill and the side of the hill.

2: The goblins spawn near the top of the hill.

3: I don't have an airlock on the top yet.

3.5: The last siege didn't use the entrance on the top.

4: I have a small bridge and moat on the side entrance.

5: I think I have around 10-20 real life minutes to prepare.

6: I have ballistas.

7: I have TONS of animals.

[Reelya]

Possible solutions

- go full turtle, and cultivate anti-gobbo systems underground. Easiest solution, but you lose access to migrants and caravans.

- build a lever-linked atom-smasher which the gobbos will path through, with raising bridges to form an airlock (or pressure plate/hatches to stop them pathing in too far). Kinda cheesy, but effective. Though you lose materials.

- Animal grenade + assault forces. All animals into a cage, lever linked, build it in a strategic spot. Draft any useless dwarves + proper squads. Basically you want to time things so your troops enter the fray very soon after the gobbos start fighting the animals. The extra useless dwarves are to further reduce the amount of hits your main force takes. This would be the most fun, but probably not the most sustainable, unless you really toughen up your military before the next siege.

- If the gobbos don't bring building destroyers then you can trap them with simple hatch/pressure-plate combos. e.g. a room with a bridge for a floor (and a pit below: make sure to lever-link the bridge), and at each end there are entrances each with a pressure-plate/hatch combo. They can path in, but not path out. Building destroyers throw a spanner in the works because they break the hatches. Which traps the current gobbos in there, but prevents more pathing in. Later, you can do something like flood the pit.

[ToastGoats]

Alright, here's my current plan.

I have to type this on a phone, so please excuse the poor quality of this diagram.

B: Ballistia
C: Cage with animals
T: Various traps
=/|: Wall
[\\\\]: Bridge over a moat
#: Fortification
[]: Pressure plate
E: Entrance
D: Dogs

                 ===========       D
                 |B#              [] T  |
                 ===  =========
                      |T|
                      |  |
========== [] =======
E[\\\\]               C            |
===================

[Kogan Onulsodel]

You should leave some space behind the fortification before putting in your ballista, the siege operators will run away as gobbos/trolls get close. Also, if you use cage traps, I recommend setting up an "inside" burrow, setting it on a civilian alert, and then using it to keep all your civilians from resetting the cage traps (and keep them inside in general, but my point is that, in my experience, the simplest solution to the reloading cage traps problem is to make your civilian alert keep them away from the cage traps as well).

[Montieth]

Yeah I have one I devised that works great. But you need a good water supply, e.g. river water. The goal was to devise a system more effective than a cage-trap corridor, because my dumb dorfs would keep trying to clear cages during a siege. To keep them safe would involve a lot of opening and closing gates and careful micro so that dwarves don't go collecting where uncaged hostiles happen to be. Plus, sieges too large for the number of cages were a problem. A set-sized trap that captures as many as needed is required.

Alerts and Warrens prevent this.

Your warren should cover the safe area of the fort and NOT the entry hall or places where you have early protection traps. Set a civilian alert and everyone runs inside and even if a trap is tripped, they will not go into the non-safe areas where the traps are even if the doors are open.

[ToastGoats]

I'm putting the airlock underground so I have more time to build the traps.

[Reelya]

Yeah I have one I devised that works great. But you need a good water supply, e.g. river water. The goal was to devise a system more effective than a cage-trap corridor, because my dumb dorfs would keep trying to clear cages during a siege. To keep them safe would involve a lot of opening and closing gates and careful micro so that dwarves don't go collecting where uncaged hostiles happen to be. Plus, sieges too large for the number of cages were a problem. A set-sized trap that captures as many as needed is required.

Alerts and Warrens prevent this.

Your warren should cover the safe area of the fort and NOT the entry hall or places where you have early protection traps. Set a civilian alert and everyone runs inside and even if a trap is tripped, they will not go into the non-safe areas where the traps are even if the doors are open.

But the problem is that the dwarfs need to clear the traps some times when there's an X-sized invasion, where "X" is bigger than you planned for. Gates need to be opened and closed, alerts turned on and off, and uncaged enemies gather around caged ones when there's a big invasion. So there's a lot of micro still needed. The water-based trap is to avoid needing the micro: it's a plan to secure sieges of unlimited size without need 1000's of cages, or having to split up and cage the siege in sections. Because that invariably gets messy with stragglers hanging around their caged team-mates.

[ManaUser]

Well a sideways cross section would look like this for the basic set-up:

Code: [Select]

XXX#XXX
  _^_ 
XX___XX
^ = plate, # = water source held back by a hatch
_ = floor hatch, ___ = bridge (for clearing)

Further along the tunnel you need some drainage grates or something to clear excess water.

This looks great. I'll have to try it. Will a pump stack work for the water source? Or do I need a raised reservoir?

[Reelya]

I think a single pump stack would be plenty. I just had a 1-wide tube straight off a river. Worked flawlessly. But if you're pumping water up many levels, then maybe you want to look at recycling the water with single pumps:

Code: [Select]

---> <---
X %%#%% X
   _^_   
XXX___XXX
The arrows show the direction of pumping. This would only lose water from evaporation on the tiles in between the pump inlets, so not too much. This could in principle be filled any way you like, between or during sieges as needed. Obviously a large reservoir would be an advantage with this set up.

You'd basically assume that up to 5 units of water would evaporate per capture in this pump-based set-up (in reality, less, if the captures are close in time). So to capture a siege of 20 guys, you'd want water holdings of at least 14 full tiles.

And you could in theory set up a pump stack from the drowning level ... so you could select "drown" or "capture" modes (more water will evaporate in "capture" mode however). What's below that level, well that's where it gets creative.

[ManaUser]

Water conservation won't be an issue, it'll be sourced from an aquifer. Although stopping items from getting lost down there may be an extra engineering challenge. I don't have much elbow room because the surface freezes. I like the idea of a non-lethal mode, but maybe I better safe that one for a non-aquifer map.

[Montieth]

But the problem is that the dwarfs need to clear the traps some times when there's an X-sized invasion, where "X" is bigger than you planned for. Gates need to be opened and closed, alerts turned on and off, and uncaged enemies gather around caged ones when there's a big invasion. So there's a lot of micro still needed. The water-based trap is to avoid needing the micro: it's a plan to secure sieges of unlimited size without need 1000's of cages, or having to split up and cage the siege in sections. Because that invariably gets messy with stragglers hanging around their caged team-mates.

Any cage traps should have a tower set near them so you can put crossbow fire upon those obstacles.

As to cleaning the traps, that should happen AFTER the siege is ended and you're harvesting your goblinite and discarding the troll fur socks.

[ToastGoats]

I have another idea.

1: Put two bridges in an underground airlock.
2: Have two pressure plates to close each bridge.
3: Make dorfs put in walls and close off the airlock.
4: Flood the airlock.

I doubt this is practical, but I'll post a screenshot of my entrance later so I can get a clear plan.

[Reelya]

Water conservation won't be an issue, it'll be sourced from an aquifer. Although stopping items from getting lost down there may be an extra engineering challenge. I don't have much elbow room because the surface freezes. I like the idea of a non-lethal mode, but maybe I better safe that one for a non-aquifer map.

That's why I have a bridge under the whole thing. It's for dumping the contents out for retrieval.