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[Oaktree]

The physics and weaponization of mine carts is being worked on and overseers have implemented them as defenses.  But I have not seen too many threads on the details of the actual installations and some of the accompanying issues that crop up.  So, a short write-up and description of the "gun" installed in Cryptdagger.

1. Range - The installation is designed for a surface level shot.  It will fire out through a fortification, across a ditch, and down a walled-in "corridor" that is five tiles wide.

2. Firing reaction time - Change to a hauling point departure criteria; followed by the time it takes a dwarf with cart hauling task to go to the cart and push it.

3. Effect - Cart moving approximately 1 tile/tick tosses a 25% load (~200 objects) of copper weaponry down the corridor.  If unblocked, a majority of the weaponry reaches the far end about 20 tiles away.  (Preferred weaponry mix right now is roughly 60% spiked balls, 30% serrated disks, 10% spears.)

4. Construction requirements - Tunnel, block for building track (installation is on a clay layer), copper weaponry for ammo, mine cart, and time.
 
Installation - Side View:

Code: [Select]

Surface   ______________X F      ___(targets)____X
Z-1        L===RRRRRRR===.X
Z-2               (r)====<X
X - Wall
F - Fortification
L - Launch Point (see below)
= - Track
R - Ramp-based Linear Accelerator (see below)
. - hole to Z-2
< - Roller to push cart
(r) - Return location for empty car (see below)

The Launch point is simply a stretch of track where loaded cart(s) can sit waiting to be pushed into the linear accelerator.  Cart can be loaded there (if close to weaponry, or loaded elsewhere and then guided or otherwise moved to the firing position.

(In Cryptdagger Stop 1 on the route is a single piece of track in the Armory where the cart is loaded to 25% capacity and then guided up to the firing position (Stop 2) where it sits with orders to wait for 50% load drawing from a stockpile that doesn't hold copper.)

The Return Location is where the cart ends up after being fired.  It is Stop 3 with an order to guide the cart back to the Armory for reloading.  If multiple carts are being fired then access can blocked by locking a door.  It potentially can also be used as a loading location if retrieved ammo is a shorter haul to this point rather than the Armory.

The Ramp-based Linear Accelerator (RBLA) is someone else's clever exploitation to get the effect of coasting a cart down ramps without changing Z-level.  For eastward acceleration a set of North&East track ramps are built with a wall along the north edge.  A cart pushed into them from the west "derails" onto the ramp and rolls down it to the east - gaining impulse.  It hits the next ramp from the west and the process repeats.  With six or seven ramps in a row acting in this fashion a mine cart will gain impulse speed of roughly 1 tile/tick; which is sufficient to "shotgun" cart contents.

The firing port itself is very secure.  It's 10+ tiles from the port to the operator firing the cart.  It's on a different Z-level than the operator.  It's behind a fortification and also walled and roofed in.  Stuff will get fired out while not allowing anything in.

=== Results ===

This installation has been fired twice. 

The first was a 20% load of mainly copper serrated discs into part of a human squad sieging the fort.  A lot of hits glanced off the human's bronze and iron armor, but there were also a number of lower limb amputations and some other wounds inflicted.  Also, a lot of the ammo only traveled 20 tiles or so.  (The RBLA was 6 ramps long at that point, it was lengthened to 7 ramps for the second use.)

The second shot was a 25% mixed load of copper serrated discs, copper spiked balls, copper spears, and some miscellaneous copper weapons into a half-squad of mounted goblins.  Including a goblin elite archer on foot.  Everything in the middle three tiles of the shot was obliterated.  The Elite archer was hit by four spiked balls for bone damage and then killed by a spear through the head.  The copper discs were once again not that effective on armored goblins, but they were excellent at taking out the unarmored cavalry mounts.  The lone survivor was on the edge of the shot width and still was hit by 3-4 weapons and suffered wounds.

The main logistical downside is clean-up.  Once you fling a couple of hundred items out there someone has to go pick them up.  Plus sweeping up the goblin bits.

[Di]

Why would you need the cart return system?
It's not like your canon is capable of multiple shots in a row and it's not like multiple shots require single cart.
First, you can reduce reaction time by replacing dwarf pusher with rollers that are connected to power source with a single lever flip.
Second, place second  route stop on the tile on which cart ends up after shot. Place stockpile that accepts the canon ammunition in the target sector, so that after shot all items ended up stored there. The pile should take from links only and not accept bins. Then place third stop of the route near it (or in the middle of it, you can place piles over tracks btw), you get the idea. Use burrows and alerts to prevent civies rushing to reload the canon during the siege.

[Oaktree]

Why would you need the cart return system?
It's not like your canon is capable of multiple shots in a row and it's not like multiple shots require single cart.
First, you can reduce reaction time by replacing dwarf pusher with rollers that are connected to power source with a single lever flip.
Second, place second  route stop on the tile on which cart ends up after shot. Place stockpile that accepts the canon ammunition in the target sector, so that after shot all items ended up stored there. The pile should take from links only and not accept bins. Then place third stop of the route near it (or in the middle of it, you can place piles over tracks btw), you get the idea. Use burrows and alerts to prevent civies rushing to reload the canon during the siege.

The return system is just getting the cart back towards the core of the fort for retrieval.  It does do multiple shots in a row given the with multiple carts lined up and loaded they can be triggered off in fairly rapid succession.  A lever-roller system is not in use because as far as I know rollers are still bugged and are always powered.  (An alternate I guess would be using a retracting bridge to drop a loaded cart onto the rollers.)

And there is an untested addition with a retracting bridge at the far end of the range that can be opened to drop any ammo that gets there down a level or two for safer retrieval.  Making that stop 3 (or a new stop 1) for reloading is an option - but I did not mention it since it has not been tested yet and verified to be effective.

[Di]

I've been using rollers as starters in every shotgun I've made. They don't remain powered if you disengage the gear assembly.
As for additional stops, well they did get the job done, but I've had to abandon that practice when I've started making curvy path for invaders. There wasn't enough place for piles because of all those shortcut bridges and cagetraps for leaders (which are a nice way to get gobbos standing where you need them).
Also, if you use corpses as ammo they will leave a nice red trail over every tile they fly through.

[Triaxx2]

Who needs rollers? The last tile can be a pressure plate actuated bridge. Plate one is 100 tic ks away and will close it. Pressure plate two is less than one hundred ticks away and opens it.That drops the old cart out, and then leaves a space for the new one to fire.

Or a hatch, because it's at the end of it's track anyway, and two pressure plates. Hatches are instant so it will open, dropping the cart and then close again right away, leaving it ready by the time the next cart arrives.

[TinyPirate]

This is really neat - is there any chance of a save somewhere? For one - I would like to look at the accelerator, for twoth, I'd like to possibly feature your work in a webcast I've got on for O'Reilly on Friday (full credit, of course).