Minecart Airlock
it basically involves 2 track stops (no tracks required) with 3 tiles in between, the tile in the middle is a pit, and both stops are set to ride on a set amount of days or when the cart is full of certain items.
S+.+S
the pit separates one section of the fort from another, so a dwarf rides the cart from the first stop and it jumps over the pit onto the floor tile on the other side of the pit and then stops on the track stop, then it can be rode back.
5 tiles is the minimum setup for the cart to jump over the pit, with 3 tiles the cart falls on the pit.
one of the stops has to have at least 1 day more of dealy to avoid the same dwarf to ride-in and out again.
if one of the stops is set to push and the other is set to ride you get a one-way entry system:
dwarf 1 rides in, dwarf pushes cart back out, dwarf 2 rides in, and so on...
I was trying this as a way to have automatic air-locked outposts for gathering resources outside the fort while keeping the fort closed to invaders and keeping dwarves from randomly wandering outside...
For instance, my plant gatherer can be gathering plants and my woodcutter can be falling trees outside the fort, they bring the plants and wood to a small stockpile outside, then they load the items on the minecart and ride over the pit into the fortress to eat/drink/sleep...
At least that was the original idea.. in practice they fall sleep in the middle of the countryside since they can't path to the beds inside the fort, drink water from the brook since they can't path to the booze and eat the raw plants or vermin since they can't path to the meals, of course they are not smart enough to ride inside, enjoy all the fort has to offer and then ride outside to keep on working.
I was thinking on setting up small quarters outside with a bed, table and chair, meeting zone, and quantum stockpiles with commodities delivered by minecart... but it kind of breaks the simplicity and they idea of not having stuff that invaders can path to....