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[gchristopher]

The dwarves have built an oversized squirt gun and sent a miner (who drew a very short straw) down to invite some friends to visit.

A couple pets are staked out just inside the entrance to encourage the guests to rush inside as fast as possible, so they have no excuses about loitering or not making a wholehearted effort to enter the fort.

This is a quickly thrown-together demonstration of a revised minecart water autocannon design. It's very similar to QuantumMenace's Wave Cannon, which built on work by TinyPirate and everything from the Minecart Physics thread. This design features a very small cart loading area and impulse ramps going both down and back the acceleration section, so that part is roughly half as long. It's still stackable to an arbitrary number of barrels.

While this save does use Masterwork DF3 to test the effectiveness of the much larger globs from using magmatankers, the cannon design is 100% vanilla and works with minecarts. (Though, it's more sporting to the clowns with regular minecarts. With magmatankers it's just embarrassing.)

Here is the demonstration save. Just start it up, unpause, and enjoy the extremely goofy results!

The design isn't that complicated!



To start it, slowly drop a bunch of carts (at least 8?) into each barrel, then retract the bridges. It won't jam if too many carts are loaded, but might be unreliable with too few.

The pressurized water source is critical. This thing hurls an insane quantity of water and needs the loading area to stay at 7/7 water from pressure, so there's no risk of liquid flow moving carts around. There's lots of ways of getting water to an area, so that part's left out of the schematic.

This design re-uses the excellent firing range from QuantumMenace's Wave Cannon. Most important is how he uses pumps to quickly drain water from the firing range so it remains pathable and enemies keep coming.

Here's some previews of the results from testing:

The poor guests are strewn in bits and pieces all over the firing range.

Spoiler (click to show/hide)

This little guy really hung in there for a while!

Spoiler (click to show/hide)

Some random detrius:

Spoiler (click to show/hide)

A Frost Wraith left buttock!? I wonder what happens if you pick up a bodypart made of flames?

[Just Some Guy]

I don't understand how this works but it tears clowns to shreds. Tell me why.

[fricy]

Don't get me wrong, but I LOVE YOU!

[gchristopher]

I don't understand how this works but it tears clowns to shreds. Tell me why.

The first I heard about it was when QuantumMenace wrote: "Combat physics treats Water [833] as a giant rock weighing 459, IIRC, heavier than most boulders. So, what if you use it in a "minecart shotgun" setup?"

The unusable ramps are called "impulse ramps" and exploit a glitch that accelerates minecarts that roll over them. The long down-and back track section in each barrel accelerates a cart containing water to the maximum velocity allowed by the game.

When the cart is blocked by the stationary cart, it halts and ejects its contents. This water "glob" is now traveling extremely fast and is treated by the game as a boulder going the same ridiculous speed. That "boulder" hits the target, causing appropriate damage, then transforms back into water.

The 833 water from a minecart is enough to kill just about anything. Some extra-tough clowns might manage to walk the length of the barrel, taking a severe beating along the way. The 10000(!) water from the magmatankers used in this mod is enough to also knock back clowns, so they don't even have a hope of making it through.

Only a creature that is nearly unkillable and larger than the water glob has any real chance of making it past the cannon. For the giant water blobs, I guess it'd have to be something like a giant sperm whale thrall. (Not undead, just thralled.)

[Urist Da Vinci]

I don't understand how this works but it tears clowns to shreds. Tell me why.

The first I heard about it was when QuantumMenace wrote: "Combat physics treats Water [833] as a giant rock weighing 459, IIRC, heavier than most boulders. So, what if you use it in a "minecart shotgun" setup?"

The unusable ramps are called "impulse ramps" and exploit a glitch that accelerates minecarts that roll over them. The long down-and back track section in each barrel accelerates a cart containing water to the maximum velocity allowed by the game.

When the cart is blocked by the stationary cart, it halts and ejects its contents. This water "glob" is now traveling extremely fast and is treated by the game as a boulder going the same ridiculous speed. That "boulder" hits the target, causing appropriate damage, then transforms back into water.

The 833 water from a minecart is enough to kill just about anything. Some extra-tough clowns might manage to walk the length of the barrel, taking a severe beating along the way. The 10000(!) water from the magmatankers used in this mod is enough to also knock back clowns, so they don't even have a hope of making it through.

Only a creature that is nearly unkillable and larger than the water glob has any real chance of making it past the cannon. For the giant water blobs, I guess it'd have to be something like a giant sperm whale thrall. (Not undead, just thralled.)

Also, IF the creature that is struck weighs less than the projectile AND the creature is standing right in front of the muzzle of the weapon AND there is a wall right behind the creature AND the projectile is travelling near the maximum velocity in the game, the creature will be blown apart as if it fell a large distance.

[smakemupagus]

Nicely done

[Shoruke]

Gods, I just love what people can do with these minecarts. This is genius.

I'll have to load up that save later; I'm at work currently, so I can't just now.

[Itnetlolor]

Anyone got a DFMA video made of this thing in action?

[Urist Mcfortwrecker]

now find a way to make it kill giant sponges, or shoot slade

[BastiBasti]

It's funny, now we have mine carts and other clown-mincers we're going to need to have a super-hell, or something to keep us entertained

[Girlinhat]

I'm working on a magma version.

[vcordie]

few questions about this. How exactly does the water drain from the firing range? How pressurized does the water have to be (and how to build up water pressure, but that's not exactly on this topic and something for my own research), and how feasible is this trap. I mean, for real. Why should someone do this versus just the old dodge-me trap+ballistas.

[Ubiq]

How long does it take water to freeze if it has been launched this way?

Does it just freeze the second it leaves a subterranean tile, after it hits something and coats the ground, or does ice form in mid-air?

[gchristopher]

few questions about this. How exactly does the water drain from the firing range? How pressurized does the water have to be (and how to build up water pressure, but that's not exactly on this topic and something for my own research), and how feasible is this trap. I mean, for real. Why should someone do this versus just the old dodge-me trap+ballistas.

The level above the firing range has pumps pulling up through floor grates. Water is pulled up off the range continually by the pumps, then flows out and down to an aquifer.

You need enough water pressure to keep up with the firing rate and keep the trench full. A four barrel cannon running at maximum speed will (possibly depending on the flow pattern) outpace a single pump pulling up from an aquifer. (This one, using modded "magmatankers," runs slower than optimal.) The easiest way to keep the trench pressurized is to have a large amount of water one level below, continually refilled by an aquifer, then pulled up into the trench with 2-4 pumps.

Minecart/water traps are a lot of work to build, but far more effective than siege engine traps, work against flying enemies that don't fall in pits, never jam and require no dwarves to operate or ammunition to be constructed. Even with normal minecarts, you can laugh off sieges without risking a single dwarf. Even most megabeasts don't have much of a chance. It's pretty game-breaking in that sense, though worth building for the fun of making a giant preposterous defense monstrosity. If you download the savegame, unpause, and watch the carnage, the point comes across.

I built one using a single dwarf in a Hermit game. It took him about 20 years by himself to finish the project, but he also had to do everything else in the fortress, too.

The biggest feasibility issues I run into for these traps are space and complexity. My example here is 20-30 tiles long for the cannon barrels and another 40-50 for the firing range, plus whatever bridges/cage traps/etc you want to have. Also, you only have to misplace one ramp or drop one minecart at the wrong place during construction and suddenly instead of a cannon, you have a meat grinder that can murder half your fortress while you try to fix it. Once built correctly, you can lock it away and never have to touch it again, but especially if you have to fix a mistake after putting some carts in the system, it's dangerous.

I'm working on a magma version.

Bwahahaha! Can't wait to see it.

How long does it take water to freeze if it has been launched this way?

Does it just freeze the second it leaves a subterranean tile, after it hits something and coats the ground, or does ice form in mid-air?

I don't know how fast water freezes. While flying, it's not "water," but it's actually a generic projectile "glob" that happens to be made of water. When the glob hits something, it turns back into 2/7 water (7/7 for the silly modded globs) at the point of impact. At that point, it's water again and freezing physics probably start being applied at that point for any transition to ice.

[Ubiq]

I don't know how fast water freezes. While flying, it's not "water," but it's actually a generic projectile "glob" that happens to be made of water. When the glob hits something, it turns back into 2/7 water (7/7 for the silly modded globs) at the point of impact. At that point, it's water again and freezing physics probably start being applied at that point for any transition to ice.

So exposing the firing range to the outside in a cold weather biome might create a freeze ray then?