I blame John Kovalic.
(Go read the strip now before I ruin the joke any farther. Back now? OK.)
I've got a few dice towers, but a dice trebuchet? Not so much. So clearly, I needed to make one.
The frame, made from 3/4" birch plywood, is easy. A little CNC work for the supports, routing out spaces for 22mm bearings at the top, cutting through all the way in the center to make room for the axle to move freely, and some sockets in the base for the uprights. A little sanding and it all fits together nicely
The other wooden parts are mostly made from standard stock. At the center of everything is a short section of solid 3/4" square birch. It has 5/16" holes bored at the ends and all the way through the middle. Why 5/16"? Because that's almost exactly the diameter of the 8mm holes in the centers of the bearings. A 5/16" dowel for an axle fits very snugly. Since I've got it around, more dowel forms the throwing arm and the counterweight arm. I'm increasingly using the 3d printer to create jigs and other placement aids, and this project was no exception. All drilling was performed with the use of a jig with a 5/16" bore and a small frame allowing it to be centered on a 3/4" width.
Then it's off to more 3d printing. The basket at the end of the throwing arm is 3d-printed and presents a vastly easier solution than cobbling together a more realistic but teeny sling and release mechanism. It's big enough to accommodate 3d6 for any reasonably sized dice if you're playing GURPS. I assume it'll hold die for other games, but why would you want to play those?
The counterweight is, appropriately, a small dice bag, so it can serve as an ammunition supply as well. There's a small hook on the counterweight end of the arm to hang it off of, but it can be taken off to add or remove dice, changing the force of the projectile. If dice aren't heavy enough (and, to be honest, they probably aren't), those little glass stones can be used which double as level markers
for games like Munchkin.
And how effective is it? It's not bad:
That's a fairly standard d6 being propelled across the length of a fairly standard dining table. With a bit of a backstop and/or a smaller counterweight (this was using a stone icosahedron), the trebuchet could actually be used to roll dice. Or to destroy your enemies.
UPDATE: For the benefit of those with CNC machines, I've published the Easel design on Inventables, so you can make your own.