Ballista

thingiverse

This is recreation of a Roman ballista. Its small (obviously), and isn't an exact replica (Romans didn't work in plastic). Its about the right size to fire a pencil. It should be fairly obvious how it works, but I have some instructions below, and a short movie. P.S. I am aware of the Thingiverse policy not to publish "weapons". I see this as a toy -- it can fire a pencil about two feet with considerably less force than I can throw it. However, please be careful as points can always put out eyes. Also I know someone could potentially beef this up until it fires knives at a 100 miles and hour. Please don't. TODO: this is a work in progress because there's some things I want to add. -- a mounting point so you can put it on a "table" (a stand on a pedestal). -- a ratchet, winch and trigger mechanism, that are vaguely period Instructions (1) Print out the parts: 1 of each of the body parts (technically these should be called the ladder) 1 pair of arms 2 frames 2 pairs of winders Clean the pieces up, and maybe smooth the bore of the body parts a bit. (2) Assemble: see pictures for some help if needed. put the two body parts together. They click nicely into place when made with my settings put the two frame parts around the matching inset part of the body. Again they should nicely click. put a pair of rubber bands through a winder, then an arm, and then a second winder. Then you can push the winders through the holes in the frame so that the arm is suspended between the frame. Repeat on the other side. Make sure the arms are facing the right way (see pictures). wind up the winders to put tension on the rubber bands. They don't need to be too tight, but its helpful to have the top and bottom be about the same. attach a piece of string to the ends of each arm, so that it is just under tension (i.e., not loose, but not too tight either). The string should pass through the slot in the body. now the fiddly bit -- pull back the arms, and the string between them so that you can just reach it through the back hole of the body. Tie a second bit of string to the middle of the first piece. the idea is that the second piece pulls back the first piece of string, and hence the arms. A big knot is OK here as it helps catch the pencil. Now you are done.