Alright! Finally back with some more results. Wall-o-text awaaaaay!
The leader would usually be flushed first, right? Then why not let the leader be flushed down a chute without a stair and provide an alternative way to the bottom chamber - lined with cage traps which will be triggered by goblins trying to reach the leader without all that "Oh my leader is caged I will not continue or flee" jazz. I'll have to try this out sometime - maybe someone else could redesign his system to try this?
^^
This; that ridiculous staircase is gone out of the middle of the pit. What I have now is open access to the bottom of the pit, reachable only through the inside of the fort (Guards' barracks, to be safe), so invaders will still walk through the door traps to try to get down to their leader's smouldering remains. Tested in the latest siege, and they cooperated.
As a possible improvement, pressurizing the reservoir above would would likely make the response time faster, and then just expand the drain/sump to a fortification-map-edge for drainage.
I originally thought so too, but what with the magma revisions Toady did in... 34.07, I think?... it flows really fast on its own anyway. And the reservoir is big enough that I haven't run out during any sieges so far.
That's very cool. I also note that the system could use water instead of magma, and flush enemies off a narrow walkway into a pit.
Definitely; and that way you wouldn't hafta worry about installing grates because 1/7 water doesn't block pathing. I just wanted to take care of bodies/clutter all in one fell swoop =D
magma recycling
That's why I embark on volcanoes when possible; don't need to worry about levels too much =P It'd be workable if you wanted to; but as pointed out it won't be perfect so you'll need to refill at some point. As above, you could use water instead and maybe a spike-lined pit. Too much cleanup for me that way, though.
Couple other things I've noticed:
1: Bodies and clothing/armor frequently end up on the grates as enemies either try to retreat or the magma pushes them there. The bodies/clothing usually burn away pretty quickly, but metal things stay. Not too much of a problem, but still more cleanup than I'd like. Thinking I should attach the grates to a lever in the dining hall so I can drop everything into the pit on demand. Also, what with the new code making creatures aware/afraid of heat sources, burning things on the grates will block goblin pathing until they burn away (only a couple seconds).
2: According to the wiki, Trolls and other building destroyers must be
orthogonally adjacent to the thing they're trying to destroy. If that is indeed true, I can make the grating access path diagonal and they'll be forced to stand right on it to try and destroy it. Then they're either cooked by passing goblins releasing magma or (If grates are attached to a lever) I can just drop 'em into the pit to fry later. It might not matter too much either way: on my latest siege, the trolls standing adjacent to the grate to destroy it were lit on fire by the magma passing
next to them, which would be a wonderful thing if that's standard behavior for the heat transfer system now. Will need more testing.
3: Not sure how I ever missed this before, but apparently
Goblin Snatchers do not pick locks. I felt years of betrayal by my own brain the minute I realized that. Solution I rigged up: another short path (slightly longer than the magma path so the nasty Kobold thieves won't use it), one tile wide, filled with wood-training-spear dodge-me traps and lined on either side with one-z pits. The pits have an open exit that comes out
between the magma doors and the southern forbidden door, forcing sneaky snatchers to path through the trap in the other direction. Seems to work well so far, although I did have one manage to dodge through to the end without falling, to be taken care of by my war animals/military. But many, many more died in the trap. This dodge-me system seems to work for ambushes, as well. Tempted to let it try and take care of a siege. I'll put up some pictures of it soon.