Hey all, I finally got a semi-coherent plan and most of the components together for this concept that's been bouncing around the drawing pad for quite a while. Jeorg supplied the kick start with his rubber-powered throwing knife tosser. The very weekend I had everything lined up and no other plans or commitments, I lost power for five days along with a lot of other folks in the U.S Capitol area. The juice came back just in time for July 4th. I got as far as you see here and then my old camera gave out, still haven't replaced it.
I've made some great progress since this photo was taken, mainly cutting the interior track components. Anyhow, I've got two 18", 80# fiberglass pistol prods mounted in an aluminum rectangular tube that is 1x2" outer dimensions with 1/8" walls, giving a track area 3/4" wide. The protype projectile is resting on top, along with the shuttle it fits into that rides the track opening in the center, between the two prods. The shuttle I cut from 1/4" Delrin, and the prod tips I cut from a 1" rod of the same. Steel pins hold brass pulleys from a cheap rope cocking device. What I learn from this project will go into a design for a larger, compound version. The string is just a cheap stand-in, I'll wind my own. I'll probably have to replace the prods, too, as these have gotten a bit beat up by test fitting.
It got more interesting for me after the camera died. At my job I use a Zund G3 digital cutter that I've used in the past with a blade attachement to cut cardstock templates for marking my lumber and metal stock. I finally figured out how to cut some of the parts themselves on the machine with the router attachement. I cut the interior tracks and filler sections from 1/4" UHMW sheet, as well as prod clamp plates from the Delrin sheet. My hand cut and tooled pieces work great, but the machine cut pieces look so much nicer! I'm thinking of doing the trigger/lock components in Delrin, too. Speaking of which, that's where I could use some advice. I've got a few ideas, but nothing I'm in love with. I was thinking this would be a bullpup pistol, now I'm thinking a short shaft mounted to the back would be nice.