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[JimboOmega]

I personally consider doing anything that does not leave a 3-width path to my fort somewhat gamey (the idea being that's where the caravan would go, and I like to cover it, even though there is no caravan at the moment).  Using bridges/etc to make my fortress unaccessible, in particular, I do not like.  If I can raise the walls/etc and only have to worry about fliers... that takes the fun out of a siege.

I have a lot of traps, but because my dwarves have serious armor limitations (all armor grade metal is imported, since I only have galena).  I want something that can handle large numbers, in a meat-grinder fashion - without needing cleaning.  Hence I want a siege-engine based defense, and I have been hard at work producing masterwork siege parts and training my operators (3 legendary operators now).

Chewie's idea, albeit with 3 tiles wide, is one I'll work with...    accuracy is still a serious limitation, as the do have a tendency to fly 15-30 degrees wide.  For instance with the illustrated layout, I'd be losing about 1/3 of the arrows of the top and bottom weapons.  Well - assuming the open space at the end is enough that goblins in the fortification maze do not cause operators of the engines to flee.

Siege weapons are also, in my experience, the best way to deal with a troop of goblins with a captured leader, especially ranged ones.  Attacking a group of 20 goblins standing around their captured leader's cage is a recipe for a lot of fatalities; there's just no way to get your dwarves to attack in a coordinated-enough fashion for it to be otherwise.   One or two will lead the charge and take several volleys of arrows before the main group starts to engage them in close combat.  It also works the same with human sieges, which tend to mill around for a while.

I tend to wind up with milling-about goblins, usually because their leaders trip the early-warning cage traps.  In one brilliant effort they turned on the skinless administrator demon that came with them, but they could not really hurt him with their silver arrows, and wound up chasing him all over the map, resulting in more than a dozen in cages.  Now leaderless, the remainder milled about aimlessly.  I don't want casualties (and rag-tag-armored dwarves will have them), so what else can I do?

[krenshala]

To improve accuracy you should turn the path 90 degrees so folks on the path in are walking either toward or away from the ballistae.

Code: [Select]

Put the ballistae on either the left or right side of the path below:

               X
XXXXXXXXXXXXXXXX
X
XXXXXXXXXXXXXXXX
               X
XXXXXXXXXXXXXXXX
X
XXXXXXXXXXXXXXXX
               X
XXXXXXXXXXXXXXXX
X

I kind of like the idea of making the path be raised above a drop, so dodging gives the chance to fall to your doom.  Also, that would allow collection of bolts that hit the sides and fall, as someone else mentioned earlier in this thread.

[Fredd]

Being a idiot(dwarfy), I embarked with a proficient Siege Engineer(Read this, oh wiki authors). Took him about 2 years to produce masterwork ballista/catapult parts. After first migrant wave, assigned a dwarf to operate my first catapult non stop. I had set up a 3 square wide, 30 square long hallway leading to the main entrance(with channels on each edge), just for ballista death. With masterwork ballista parts, and arrows, the actually 5 wide space hallway, the bolt would fly down, sometimes not as straight as it needed to be. For step 2, set up one with masterwork parts, and standard parts, aimed from inside the city walls behind fortifications, to judge cone of fire. The masterwork had a much narrower cone of fire, perhaps 5 spaces max, up to its maximum range(edge of map). So at very long ranges, the quality proved superior in ballista. Somehow, I think toady designed the siege weapons for future use, at extended ranges, not hallway clearers. If you are going to use siege weapons, always include floodgates behind the fortifications, that you can close, in case of archers sniping at your siege ops

[blaize9]

well i had a fail with a Ballista. soo there was a gob siege going on and i forgot to pull up the bridge. so the first thing that came to my mind was use the Ballista and that did not end very nice.... it killed 8 of my dwarfs and 0 goblins  >.> ooh burrows why cant you work correctly so they cant use the stairs........ why me 

[Carnes]

I have had similar experiences as OP in .18.  I can't imagine burning that much metal in .19 unless it was silver (which would be great to use).  I could get maybe 6-7 bolts downrange before the siege ops had to scram.  Five bolts would impact walls or even the floor.. an impact is a total loss of the bolt (and metal!).  If i was lucky, 1-2 would sail straight and score a kill... if i was lucky.

The channeled corridor is a great idea though.  Excellent way to save bolts from being wasted.

My main defense is now a 1-wide serpentine with channeled sides.  Weapon traps with 5 spiked wooden balls each cause gobbos/trolls to dodge off the walk-way and down 4-z to an open room.  Most gobs survive with broken bodies.  Crossbowmen are lined up behind fortifications on one end of the open room.  It then becomes target practice.  If my axedwarves need practice, i can lower a bridge and move them into the room to chop at gobs that just fell.  There are stairs that lead back up to the middle of the serpentine.. gobs that make it that far usually dodge another trap on the way out and quickly break all their remaining bones at the bottom again.  Sometimes all the traps get clogged with bodies or something (during a big attack) and i have to fight invaders in the main hallway.  Have yet to encounter gobs on flying animals : /

TL;DR  Ballistae are painful to use.  I now use cheap tricks (but no cages).

[EveryZig]

I wouldn't throw away silver like that. Silver makes some great hammers (in fights between steel armored grandmaster dwarfs in the testing arena, the silver warhammers did about as well as addy battle axes)

(Just remember that silver hammers only work on creatures with innards to crush (not bronze colossus))

[JimboOmega]

I wouldn't throw away silver like that. Silver makes some great hammers (in fights between steel armored grandmaster dwarfs in the testing arena, the silver warhammers did about as well as addy battle axes)

(Just remember that silver hammers only work on creatures with innards to crush (not bronze colossus))

All my dwarves have silver warhammers.  I also use silver spike balls in my traps. 

Is metal required to make accurate or damaging arrows?

Also, does anyone know the distance for operators running away?  A longer zig-zag pattern - where operators can fire at a greater width of enemy - might do me better, but operators would flee from enemies at each end unless I give them enough space.  Speaking of which, I *did* channel the area nearest to the operators, the "buffer" before the hall starts - when arrows hit the side there (as they often do), I can recover them (that they hit the wall before going 10 tiles is disappointing though

The downside of the channeled sides is that they would have to be a place dwarves have access to (and are thus a risk), and also they're a place dwarves can get lost in.  I once set up a  long bridge to access my fort, with the result being a lot of dodging casualties.  Of course, it also improves goblin dodging casualties, which is a plus.  But I have a hard time keeping my military from going 80 tiles off station chasing down one goblin hammerman, so I like to stay safe.

[Carnes]

I think you want your arrows to be as heavy as possible (more kinetic damage), so silver is great.

[Urist Da Vinci]

Tested ballistas and catapults on flat ground:

Ballista range:  200 tiles
Catapult range: 210-220 tiles

Shots fall evenly within a 20 degree cone (10 degrees each side). This is roughly equivalent to 5 tiles forward, 1 tile sideways. At max range, the cone is +/- 38 tiles from the center (76 tiles wide). So having several ballistas side-by-side increases the chance of a hit in the center if all are shot at the same time.

Operator skill shortens reloading time. I don't know how accuracy is affected yet.

Marksdwarves open fire at the same range that siege operators get scared (20 tiles).
The minimum catapult range is 30 tiles.

I'd build a battery of catapults, and have a lot of dwarves trained to use them, so I could unleash a shotgun-like stone rain at a goblin siege group.

Catapult stones fly over trees. Ballista bolts smash trees and keep going.

If you force a ballista operator to walk over a pressure plate to get to the ammo or to leave the room, you could wire a door to open in front of the ballista bolt. This may allow bolts to be fired at close range without the operator getting scared, but I haven't worked out the timing yet.

[JimboOmega]

Shots fall evenly within a 20 degree cone (10 degrees each side). This is roughly equivalent to 5 tiles forward, 1 tile sideways.

Hence - for a 3 width hallway, 5 forward/1 sideways is going to see all of the arrows miss by 15 tiles out (deviating 3 tiles in any direction means a miss, even with the north ballista deviating south).  Given that they get scared at 20 tiles, in order to hit something at that distance, you need a tighter cone.   Because the gobbos are headed down the hall pretty fast, 40 tiles is the range you need to be effective at, probably.  Even with legendary operators,  and arrows only a few tiles away, having only 1 in 10 still be in the hallway that far down basically renders them ineffective.

Zig-zag hallways are better, but the limit of about 20 tiles to keep operators at their posts means you're already seeing deviations around 4 tiles, by your research, which means that in a triple-zigzag 3 tile wide corridor (9 tiles total), bolts fired from dead center are already falling off the mark.

[rephikul]

stones launched from cats seem to cause damage BEFORE they touch the ground and thus have an area of potential destruction larger then 1x1. I'd assume all of those stones are actually 200 tiles range.

Markmen can aggro at ridiculous range also, not just 30 tiles.

[BodyGripper]

I wonder if the "Ballista Checkpoint" in this map would have been effective?  I never came anywhere close to finishing it, mainly due to bugs and stuff.

[JimboOmega]

I just managed to hit a group of goblins with an exceptional silver arrow and an exceptional wooden arrow.  The latter hit 4 goblins more than 10 times, the former hit more than 6 times across 2 goblins.

One goblin got its skull jammed in, but all other hits were bruises.  Often deep bruises, to guts or liver, but bruises nonetheless.  No broken bones or disabling injuries.

Kind of disappointing, for the exceptional silver arrow in particular.  Even the fatal strike ALSO bruised the head, not break it.  (yet it somehow jammed the skull into the brain).

[JimboOmega]

Here's a very typical example of the damage - a masterwork silver arrow hits a goblin in leather armor and...


Bruises.  Great.  I'll admit though, this one hit another goblin and it broke his arm, while also bruising the guts - guts bruising was bad enough to cause vomiting and unconsciousness, so at least that's a point for slowing them down.

My favorite was when an exceptional silver arrow hit a goblin in the throat and caused a bruise.  I can't imagine anything that could rightly be called a siege weapon hitting anything in the throat and only leaving a bruise.

(FYI, Legendary Operator, masterwork/masterwork/exceptional ballista)

[Cotes]

Yeah, I don't think ballista arrows benefit from the weight of the material the same way hammers and maces do.

Those things were ridiculously powerful at some point, regardless of what kind of arrows they used, if I remember correctly. They were toned down a lot for DF2010, but I'm not sure it was a good adjustment, given that a ballista fired at mid-range should be ridiculously powerful, and that the inaccuracy, immobility and the slow production of ammunition already balances them (not to mention siege operators crapping their pants).