What is the most efficient way to build a danger room?
Depends on the size of the squads being trained, but technically, it can be done with a 1x1 tile like this:
OOOOOOOOO
OaDX++++
OOOOOOOOO
Where: O = wall
a = armor stand
D = door (internal, forbidden, pet-impassible)
X = Upright Spike Trap (fill with wood training spears)
+ = door (external, pet impassible).
Make the doors before the spikes pet-impassible, and the door between spikes and armor stand needs to be forbidden AND internal. then create a barracks room from the armor stand and enlarge it to cover the spike tile. This makes all dwarves stand in the same 1x1 space.
How large? Any specific size that works best to get whole squads in?
For style reasons, I go 3x3 for the spike room, but the only limits are mechanisms/materials and patience. If the room is defined as a barracks properly, squads will pack
themselves into the room on their training schedule.
I made one that was 4x4 and I still had trouble getting all 10 in.
Make sure you're defining the spike room as a barracks, and the dwarves will pack themselves in to train.
Then I decided I wanted more dodge armor and weapon training, and removed the shields. I lost a lot of very skilled dodgers and armor users on wooden training spears. Is it because they fell asleep or something? With a shield, I had a dwarf sleep through about 20 rotations.
1. Are you sure you used trining spears and not menacing spikes? I've never lost an adult dwarf to a danger room, though I've lost children to inattentiveness.
2. Make sure you have a robe or claok assigned to dwarves to cover their necks and other "odd" body parts. Training spears CAN kill, if they hit a vulnerable spot with no armor, but even a cloth robe will protect them. I typically use leather robes, as this gives me something besides quivers and backpacks to do with all of those hides...
How many spears per trap should I use? 1? I've been using 3.
Season to taste. 1 spear is the minimum, 10 the max. 10 will produce an absurdly fast training rate (10 attacks to deal with per frame) but this is seen as exploitative by some. I usually go with four or five in a small room (3x3), both to reduce the number of spears and mechanisms, and to keep the training rate somewhat reasonable.