[other traps]

Multishot Pellet-Gun Trap

I usually focus on making it difficult to find and disarm a simple explosive-cap trap, but this year I wanted to change things up a bit and focus on the effect itself. In particular, I wanted to make a box trap that would shoot darts out in all directions, machine-gun style. It had to be completely mechanical (what can I say, I like the style better), and had to be stable enough to ship through the mail without going off or getting jammed. After many failed attempts at designing a mechanical rotary slug-thrower (modeled after the Portable Electromechanical Slug Thrower) I landed on this rather elegant sprung-hammer design.

The trap is designed around an octagonal wooden box with a deep hinged lid (purchased on sale from Pier One). I mostly built my own scaffolding and left the box unmarred, but as you'll see below I did need to make a few nail holes in the lid. Each pellet is propelled by a dedicated spring-steel "hammer" that is poised behind the pellet's firing hole. When the trap is set, the hammers are held back by three wooden barriers. As the lid is closed, these barriers hook onto a metal ring around the inside of the lid. The next time the lid is lifted, the barriers go with it and allow the hammers to spring back to their original position, thus whacking the pellets out of their holes.

Warning: This trap fires small pellets and should only be disarmed or opened by people wearing eye protection. This kind of trap should not be left unsupervised while armed.

Equipment

• 1 Box with deep lid
• 3 wooden tiles, sized to peek about 1cm above the lip of the box when placed just inside the wall.
• 10 hammers twisted from spring steel and cut about 2cm shorter than your wood tiles. I got my spring steel from my recently-replaced windshield wipers, but you can also salvage some from an old leaf rake or in some areas find it in the streets after it's broken off of street-sweeper bristles.
• 3 thin wooden barriers, with hooks screwed into their tops. I used shaped moulding from the hardware store, which had the added benefit of being slightly angled.
• Metal ring that fits fairly exactly inside the box lid. I got lucky here and found a $3 metal trivet base at my local Chinese grocery, but I'm sure you can find something else to do the same job.
• Thick (about 2cm) octagonal wooden board, cut to fit snugly on the floor of the box after tiles are screwed into the sides.
• 10 small plastic spheres to act as darts. I used 6mm Soft Air Ammo that I found at Wal*Mart.

Construction

Parts: Most of the construction time is spent making the various pieces. Cut the board that will form your "floor" into an octagon, slightly smaller than the floor of the box itself. You'll want it to fit snugly into the box after you screw the tiles onto the sides. Cut the wooden tiles such that they just peak over the lip of the box, and bend and cut your spring-steel into hammers slightly shorter than the tiles. Drill three or four firing holes in the tops of each of the tiles. The holes should be slightly smaller than the diameter of your ammo, such that the pellets stay in place but can be knocked out. You'll want to experiment with hole diameter first, as it depends a little on the type of wood you use for the tiles. Then put two small screws into each tile, positioned just below and to the left and right of each row of holes. These screws will keep the barrier from being pushed down past the hole-line when the lid is closed. Cut the barriers such that they cover a complete row of holes along a tile. They should be long enough to sit on the two small screws you just put in. Screw a hook into the top of each barrier. Depending on the shape of your barrier, you might want the hook to angle slightly back (away from the hook part).

Tiles & hammers: Place the hammers such that their heads stick through the holes, then screw the tile to the edge of the floor board, with the hammers on the inside of the box peeking out through the hole. The base of the hammers should be sandwiched between the floor board and the tiles, such that they spring back when plucked. When they're all attached, place the floor board into the box. If necessary, shim the board so it doesn't move around, or just screw it into the box bottom itself.

Lid: Place the steel ring into the lid such that it fits snugly, and fasten it in place. I just used straight nails pounded at an angle, but double-headed nails or screws would work better if you can find a good angle to drive them in.

You may have to adjust the angle of the hooks in the barriers, the position of the tiles or the position of the steel ring slightly to get the trap to arm properly (see below). Experiment until the hooks catch smoothly every time.

Arming

Assuming everything is aligned well in the construction, arming the trap is simple:

1. For each tile, pull its hammers back and place a wooden barrier between the hammer and the hole, with the hook facing out. The barrier should rest on the small screws on either side of the row of holes and should be held in place by the tension of the hammers. Make sure that each hammer is still directly behind its hole.

Placing each barrier

Loading

2. Stuff each hole with a pellet.

3. Carefully close the lid. The ring should come in contact with the hooks, such that if the hooks were solidly held in place they would block the lid from closing completely. However, since the hooks are only held by the tension of the hammers (and since they're resting on the small hooks and can't be pressed down any further) the ring will push each hook towards the inside of the box. As the lid continues to close, you should hear a click as each hook snaps into place over the ring.

   This is the step where you find out if everything is properly aligned, and you may need to change either the angle of the hooks in your barriers or the position of your tiles and/or ring to make everything work smoothly.

Firing

When you open the lid, the hooks all catch on the ring and are pulled up with the lid. When they clear the holes, the hammers fire and shoot the pellets out in all directions.

Disarming

Since this is a dart-style trap, the easy way to "disarm" it is to just open it from the back (that's what Jay did). It's also possible to open the lid just enough to access the ammo and then (in theory) pull each pellet out with tweezers, though that can be tough for pellets that are deep in their holes. Another friend of mine managed to stick a coat-hanger wire in through a crack near the back hinge and knock several hammers out of alignment enough that they wouldn't fire. He didn't manage to get all of them and the hammers have enough force that they'll work even if they aren't perfectly straight, but Jay and I agree it was a heroic effort all the same.

Of course, your intrepid trap-disarmer needs to recognize that he's dealing with a dart trap first. The pellets in my version are pretty obvious, and anyone who has experienced a dart trap before will recognize it as such, but I can imagine designs where the pellets are disguised in some way or made to look like ornamental parts of the box. There are also cracks on either side of the hinge that are wide enough to see through one while shining a flashlight through the other — giving the person disarming the trap a clear view of the hammer mechanism. Since I didn't think Jay needed any help, I inserted a piece of paper so he'd see a different view.