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[Tutorial WIP] Cooldown Juggling Rapid Fire Dart Trap Engines (Animated Guide)


The Destroyer
[Edit 2021-01-12: url links to each gif added because embedded playback stopped working. Full gfycat album here.]

The principle with all of these designs is to stagger the firing times of a series of traps using a track of pressure plates (activated by some mob or player) and then lock in that staggered firing sequence by rapidly reactivating all the traps continuously thereafter, using a high speed 'engine'. Each trap will only fire a second time after their initial firing cooldown has ended. This means that they will repeat the initial firing sequence again and again, provided the repeater engine keeps firing steady and fast.

Hoik engines are great for this since they can ensure a perfectly locked-in sequence, never letting the pattern slip by even a single tick (at up to 60 activations pr second). Dummy powered hoik engines are ideal, since they are invulnerable to friendly or hostile attacks and will continue running while you are anywhere on the map. However, any steadily firing engine will generally do a fair job too (e.g. bird engine, minecart, etc) depending on your requirements. (See examples in my old Fastest Engines Guide.)

This type of dart battery design was first shown by @DicemanX here in this thread and the repeater concept was first proposed by @Unftf.

The approach has benefits over the previous designs that used a 1 second timer for each trap (or column of traps):
  1. You don't need to make a whole load of timers, each requiring a whole load of metal bars.
  2. Since Terraria 1.3 dart trap firing cool-downs were increased to 3.33 seconds, so would only fire a maximum of once every 4 seconds on a 1s timer. The newer method always fires them at full rate, a 20% improvement in damage output per trap.
My previous rapid fire dart trap guide shows a selection of designs for Terraria 1.2 which should still be valid for all platforms other than PC. But console and mobile uses should be able to craft most of these designs too, simply shortening their tracks by ~11% (rounded up/down) to save on wasted simultaneous firings. That old video guide shows a couple of usage scenarios for these machines: mob or invasion grinders, boss arena.
This guide also explains the ideal dart spacing to account for monster's 10 tick (1/6th second) damage cooldowns.
Also see Diceman's guides with several of his builds using rapid darts: rotten chunk/vertebrae farm, efficient dungeon guardian farm, Wall of Flesh auto-farm, ultimate chain auto-farm (all biomes mobs), (old) Truffle Worm farm, Surface autofarm (mobs, events and invasions, including pirates), etc, etc.

I've enumerated a series of different designs, below, that you might pick from depending upon how many dart traps (or super dart traps) you have available, how rapidly you want them firing, what statues you've found and what stage of the game you are at (post Mech boss for teleporters, etc). For each I've shown the exact layouts for firing darts in either direction. However, it is recommended to only fire the traps in the opposite direction to the direction of travel of the firing sequence priming agent (that is, fire to the left, the lower row of dart traps). That allows for perfectly looped firing pattern, due to the helpful offset between first and last trap. In the opposite direction the offset opens up a gap in the pattern instead. The faster the battery fires, the longer it is, the bigger the offset between first and last traps and the bigger the gap in firing.

Note that a stand alone dummy (or skeleton, etc) hoik engine can be added to any of these designs for convenient operation, but I've tried to show how you can use the priming agent in each case for the repeater engine too. For elegance and for fun.;)

In each design, the exact spacing and positioning of traps, plates, engine, etc, is important. However, traps can be placed above or below the plate run, staggered horizontally and have as many additional rows are you like. Don't forget to actuate your dart traps so they can fire through each other too (then remove the actuators)!

The "Soggy Flapper" - Water slows birds down to half their normal speed, allowing a compressed plate run, perfectly spaced for near optimal number of traps. Submerged birds always tack towards player, so when activating this you must stand at the far end, opposite the statue. The water level is deliberately low like that, so the bird can exit the water quickly at the end, to transition into the repeater engine.

The "Wet-foot" - Players basic move speed is the same as a bird, and water slows player movement down to half too, so this design produces the same firing pattern as the bird in water (above). Remember to take any speed boosting boots off first.

Minecart Dummy Hybrid - Each booster track adds 15 tiles per second to the minecart speed. But the iron minecart is capped at a max speed of 48.4 tiles/s, so after slowing down with 3 reverse booster tracks: 48.4 - 45 = 3.4 tiles/s. A leisurely pace for a fairly compact battery. The last pressure plate starts a dummy ghost hoik engine, leaving the player free to go anywhere in the world with the darts still running (can be added to any other design here).

"Rail Repeater" - Same priming mechanism as above, tweaked slightly at the end to launch onto a minecart engine (in place of the hoik engine). "Boing, boing, boing!...". This can be built post Mechanic (pre-hardmode).

The "Bone Shaker" - Good old skeleton tech. A near perfect 5.5 tile/s walk speed and play-like dimensions makes these statue mobs great for this application. Able to step straight into a hoik engine at the end of a run. Be aware of Skeleton idiosyncrasies: they will try to attack the player first at night, but will always start off walking to the right during daytime, also they despawn instantly when off-screen during day at surface level.

The "Bunny Button Basher" - A gentler pace than the skeleton track, but just as workable in a carefully designed hoik engine. Be aware that bunnies are easily distracted, running away from nearby monsters (while priming the engine but ok when being hoiked).

The "Long Feather" - Without water in the pressure plate track, a bird primed battery can look a bit unwieldy. It is, however, a little less fiddly to build and modify when no liquids are involved. This demonstration has roughly the same firing profile as the "Soggy Flapper", but if you are swimming in dart traps there's no reason you couldn't double up the number of traps by filling the alternate spaces. As with Diceman's original design, top. This only adds a small amount of extra firepower (most the extra darts will be wasted during monster's damage cool-downs) but it will look awesome and may help hit the maximum possible number of times per second.

The "Chest Shuffler" - The weirdest of these designs. It utilities the unique behaviour of mimics trapped in a 'bottom hoik' slightly too big for them, smoothing out their leaps into little steps. This only works running left to right and requires that the player stands at the right hand side. There's no reason I can think of that this couldn't be made without teleporters, hoiking the mimics back, or terminating them (slowly) after each use.

The "Water Wing" - Bats are even faster than birds (in a straight line), so even halving their speed they are a little faster than optimal. Firings against the bats flight path results in a dart pattern that wastes 1 out of 3 darts (against a stationary target), while the slightly faster with-bat-flight (rightwards) firing wastes every other dart. (As you may be able to tell from the damage on the target dummies.) However: submerged bat hoik! :)

There are many more viable designs possible. Piranha have the same move speed at skeletons and there's no reason you couldn't use goldfish or even sharks, perhaps immersed in honey, to compact the track (a "sticky fin"?). So I'd love to see any other workable design, below! Or post if there's a flaw in one of my designs above, or they can be improved in some way! :)

In the next post (media embedding limit): a couple of spear and flame trap engines that use the same design concept...
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The Destroyer
Spear Trap Batteries

The cooldown juggling principle works just the same with the spear traps. Because spear trap cool-downs were actually decreased from 2 seconds to 1.5 seconds in the 1.3 update, my old rain-stick engine designs, that used one second timers, did not break.

However, the advantage of these updated designs is the ability to use about 25% fewer traps for the same damage output. Getting full value from a fairly rare commodity. The shorter cycle time also means the stacks of traps can be more compact. Plus, again, no resource hungry timers need to be crafted.

A minor disadvantage is a small, unavoidable gap in the firing pattern between first and last trap. This is due to the height of the stack and the inability to overlap their starting times (without using timers). This would become more noticeable with a faster priming agent and a subsequently taller stack of traps.

The "Stabby Bat" - Classic bat rainstick priming, ending with a crafty little bat hoik engine. Dart trap to terminate the bat. Makes for spear trap stacks 8 tall. Imperfect, with an unavoidable 1 tile gap between the last possible priming pressure plate and the activation for the hoik engine. Will still work very effectively.

Player Spear Stick Dummy Hybrid - This may be the ultimate design for a cooldown juggling spear trap engine. The last priming plate activates the dummy ghost hoik engine, locking in those spear timings for as long as you like! Does not work correctly in space, due to slower fall speed. Possibly watch out for some fall speed modifying accessories too.

Note - in both videos, above, the diagonal array of spears is primarily there to better show the exact sequence timing. You can, of course stagger your spear traps a little horizontally, to cover more ground than keeping them in a nice, neat vertical column.
Flame Trap Sequencers:

Flame trap's activation cooldown was also increased from 3 seconds to 3.33 seconds in the 1.3 update. So with a one second flame duration you technically need a 4 phase cycle for total coverage, absolute max damage. For that you could use 4 x 1s timers with chained activations in a loop. But where would be the fun in that?! To be honest, a trio of one second timers, manually activated (or used in place of a repeater engine), will generally do.

Even though a hoik engine to re-activate flame traps is a little over the top, here's a fun, compact design for a juggling engine that uses goldfish in super-slow honey!:
The "Sticky Flame Fin" - Place the flame traps however you like, red wire to one in 3, blue wire to a different one in 3 and green wire to all of them. Spear trap is most convenient to terminate the fish in it's little hoik engine enclosure.

Thanks for reading and watching this guide. It's still currently a little bit provisional, so by all means suggest additional engine design types, ask questions, etc. For those thinking about their own designs there's detailed info on all the traps laid out here, and on the current statue mobs, here.

Also, I'm going to cross my fingers that it doesn't all become immediately obsolete with the 1.3.1 update. If so, I guess it this will, at the least, be relevant to console and mobile, to some extent now and more so once they eventually get 1.3.0 (with dummies and changed timings, etc). :)
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The Destroyer
Is it possible to make a slower firing dart trap battery by using a bat that flies up or down instead of forward?
Sure, and if you happen to be firing darts vertically, using the the new trap orientations, then that might make sense. But there are such a plethora of different statue mobs and statue critters now that we are totally spoiled for choice. Should always be able to find close to the exact move speed you want, in which ever plain. Especially since you can also slow down (some of) the mobs using water or honey.


Sure, and if you happen to be firing darts vertically, using the the new trap orientations, then that might make sense. But there are such a plethora of different statue mobs and statue critters now that we are totally spoiled for choice. Should always be able to find close to the exact move speed you want, in which ever plain. Especially since you can also slow down (some of) the mobs using water or honey.
My main problem at the moment is that I do not have a bird statue :) (I do have a skeleton one through which might work)


The videos aren't working for me. Did they break or is the issue at my end?

[Edit:] Never mind, I figured it out >.<

[Edit 2 3:] Forget I said anything *sheepish*
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MQ Walkman

Another outstanding guide from ZeroGravitas! (Who, I discover, is member number 96! Only 96! Amazing.)

All of the above engines are very good, with my personal favourite being the “Bone Shaker”, except using a Medusa Statue. However, the above engines aren’t without some problems:
  1. Animal cruelty variability (in ZeroGravitas’s words, “distracted bunnies”; “Skeleton idiosyncrasies”), or
  2. Seizure-inducing screen vibration, and
  3. Dummy ghosts are (alas!) only available in Hardmode, with teleporters.
For my ongoing Engineer Playthrough, I needed a pre-Hardmode solution to both of the above problems. Here it is:


It is animal-free, helpfully uses only four traps (as opposed to DicemanX’s very resource-heavy early creations), and almost perfectly mimics the 7.5-tile optimal distance between traps. It works because a timer cascade reactivates spaced dart traps as soon as possible (200 ticks rounding up to 4 seconds). To turn it off, wait until the green torch is lit. As I have done, many can be stacked on top of one another, as I’ve done.
You might think that, because of the four different wire colours, the design wouldn’t work on pre-1.3.1 or the Old-gen console version. Actually, it would, in a modified form; their 3-second cooldown for dart traps matches their three wire colours. So, there you go. Wiring traditionalists, eat your heart out.
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