At some point, while waiting for parts to arrive in the mail, I became interested in building a small crossbow. I don’t know exactly how I’ll do the prod–the bow part–but I did succeed in making a trigger mechanism out of 1/4″ plywood tonight. It’s a rolling-nut style trigger.
I mounted it very temporarily to my drill-press block, hence all the extra holes. But the trigger does work: if you apply pressure to the notch extending up above the block, the circular nut engages the trigger. Pull the trigger and the nut slips free, releasing the shot. For a higher-poundage crossbow, you would need more leverage in your trigger. However, I plan on this one staying under 15 pounds.
If I can figure out a prod, I’ll build the crossbow and shoot some pencils with it.