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[ShDragon]

So I'm working on one of the first forts I've ever "planned out" instead of just building semi-haphazardly, and I'm pondering trading depot designs.

I have a main front drawbridge to the fort, and from there, I have two paths: One that leads to my traps of doom/military HQ/front door and one that leads to a trading depot/back door. I was thinking a good way to protect this backdoor was to "airlock" it between two drawbridges, one which would be up and one down at all times. (when there's a trade caravan coming, the outer bridge if down, and the inner bridge is up, letting the traders get to the depot. Once they get there, flip both bridges and I can carry stuff up the back entrance, to the now protected depot to trade)

Problem is I'm still somewhat new to Dwarven mechanics, so I'm looking for a way to control this. I read on the wiki somewhere, that one lever hooked up to two things that are "out of phase" won't work, so both bridges would end up matching, both up or both down. I know the easiest way to do it would be two levers, one for each bridge, and just make sure I pull them in the right order (So the down one goes up, before the up one goes down)

But does anyone have a way of building that kind of system into a single idiotproof(/Dwarfproof) lever? Optimally, I'd like it to raise the down bridge first before it lowers the up bridge, to make sure there's never a path available through the back door.

I was thinking of some weird thing with water and pressure plates and pumps, but I'm not good enough at Dwarfgineering yet to figure it out.

[Brandstone]

This is actually very simple. Have the outer bridge like normal, but the inner bridge should have either downward ramps or stairs under it instead of an entrance behind it. You can also use floor hatches instead for a quicker reaction time after the lever is pulled.

[ShDragon]

.... Oh my goodness. Build the back door UNDER THE BRIDGE. That's brilliant. Thanks!

Both bridges will trigger at the same time if hooked up to a single lever, correct?

[Dorf3000]

Yes, although if you're making raising bridges, put them a few tiles away from the depot.  I had a couple of merchants meet an unhappy end because they decided to stand just to the side of the depot.   

[Akjosch]

You can also use a bit of animal logic to trigger one bridge on while the other is off. Just remember to have an override lever somewhere ...

[JAFANZ]

Why use 2 bridges?

Build the entrance route so that lowering the 'Back' "Door(s)" opens the pathway to the 'Front' "Kill 'em All Hall".

Building it out of Floor Hatches would unfortunately require additional Mechanisms, but apparently Building Destroyess no longer choose to attack bridges if they're down, but will auto-destroy hatches, thus routing them straight to your deathtrap even if you didn't notice their arrival.

[gtmattz]

Another option would be to use floodgates in place of a bridge for one of the openings, and a bridge for the other.  Floodgates and raising bridges have opposite 'closed' states, so a single lever linked to both will raise the bridge and open the floodgates, or vice-versa.

[Akjosch]

Another option would be to use floodgates in place of a bridge for one of the openings, and a bridge for the other.  Floodgates and raising bridges have opposite 'closed' states, so a single lever linked to both will raise the bridge and open the floodgates, or vice-versa.

The problem with that is: building destroyers can then reach the floodgate ...

Now, flying building destroyer are still a problem, but thankfully there aren't all that many of them in the game.

[Shoku]

If you're interested in the more complex solutions you can create a pump with a pressure plate close behind it and an opening near the plate. If the pump is on it's going to be 7/7 deep and if it is off it should all drain quick enough that the plate doesn't get toggled very quickly. The first lever obviously starts the pump going as well as toggling a bridge while the plate is set the other way so that it will keep the other bridge out of sync.

For something a little more complex still you can have the water pumping into a closed area with another pump to dry that out. These need to be on separate power supplies so that with the flip of your lever you simply connect the in-pump but also overload the out-pump's power trail. If the out pump has one water wheel of power you just need to throw a couple of extra mechanisms into the mix to require more power than there is available.

And if you want to go more complex than that: Welcome to the world of computing. It would be better to learn about how to set up the NOR gates and such in a thread made by the people that know how that stuff works.

[ShDragon]

Why use 2 bridges?

Build the entrance route so that lowering the 'Back' "Door(s)" opens the pathway to the 'Front' "Kill 'em All Hall".

Building it out of Floor Hatches would unfortunately require additional Mechanisms, but apparently Building Destroyess no longer choose to attack bridges if they're down, but will auto-destroy hatches, thus routing them straight to your deathtrap even if you didn't notice their arrival.

I'm not sure how to lay this out.. Part of the reason I was using two bridges was that I wanted it to be an "airlock" in that there was never ever a complete path to the back door. There would be no point in time when an enemy could path over both bridges and down the back. (thus leading to hilarious consequences when the system inevitably backfired years later and an enemy gets in the entrance that I forget to defend)

The plan was basically so that I could leave Depot access available, even when I'm under attack. Since the invaders would have to path through the front door, while the traders could path to the depot. Then when the traders get in, Pull Zee Lever and the Depot is now protected "Inside" the fort, so I can carry crap up there to trade.

[Urist McKing]

Could you link a pressure plate that goes under the first drawbridge to the second one?

[decius]

Use one bridge, that the wagons pass over when it's down, and the dwarves walk across the top when it's up.

Code: [Select]

z0
*******
***>***
*DDDDD*
*DDDDD*
*DDDDD*
*DDDDD*
*DDDDD*
**...**
*BBBBB*
*.....*
z1
*******
***<..*
*****.*
*****.*
*****.*
*****.*
*****.*
*****.*
.bbbbb*
*******B=raised bridge b=top of raised bridge >=up stairs <=down stairs
Even if a buildingdestroyer knocks out the bridge, he can't get in this way. Bonus: put a meeting room somewhere in the depot area, and migrants should go there if no other meeting area is accessible. Wait until they arrive, throw the switch, and let 'em in. Or throw the other switch, and cleanse them with fire. (It's already a depot, so you should have magma ready to go...)

[Hyndis]

I prefer just using two drawbridges with two levers. This gives me perfect control over how the airlock design is being used. If need be I can open both doors if I want easy access. Or close one door but not the other. Or close both doors if I want to capture something inside the airlock.

[Shoku]

Use one bridge, that the wagons pass over when it's down, and the dwarves walk across the top when it's up.

Code: [Select]

z0
*******
***>***
*DDDDD*
*DDDDD*
*DDDDD*
*DDDDD*
*DDDDD*
**...**
*BBBBB*
*.....*
z1
*******
***<..*
*****.*
*****.*
*****.*
*****.*
*****.*
*****.*
.bbbbb*
*******B=raised bridge b=top of raised bridge >=up stairs <=down stairs
Even if a buildingdestroyer knocks out the bridge, he can't get in this way. Bonus: put a meeting room somewhere in the depot area, and migrants should go there if no other meeting area is accessible. Wait until they arrive, throw the switch, and let 'em in. Or throw the other switch, and cleanse them with fire. (It's already a depot, so you should have magma ready to go...)

That's one way to do it but probably not quite what people had in mind. Having a retracting bridge cover up the stairs/ramps to go lower and into the fort should still be safe from building destroyers because they'd kill it at the far end. Unfortunately this would leave the space vulnerable to archer types.

Now, you could still do this but instead of one long bridge make it two drawbridges that raise up to make a wall in the middle of what they span. The space under the far one could have a moat or such and the closer one could have the space your haulers run up through.


Personally I prefer using pressure plates and an animal though.
███D█D███
DHPH_HPHD
door, hatch, plate. Each plate connects to the hatches next to it and the doors lead out to the owner of the animal. You just keep the two top doors locked normally. Then unlock the one near the pet and it can get around the hatches to rush at the other door where it will trigger the plate and trap itself again.
There's a tiny, tiny delay between the bridges toggling but the hatches are instant so the animal won't get out. If you leave both doors unlocked the animal will bounce back and forth for awhile until it gives up- which is obviously no good for your bridges so you need to toggle the door twice or just remember to toggle both of them whenever you use it.

The advantage over levers, even with nice water logic to automate everything for you, is that you don't have to wait for someone to pull the lever.

Also you can use that middle space for a plate if you want to trigger just one thing.

[decius]

Shoku: That seems needlessly complicated and prone to fail for so many reasons. I like it.