Deemed the "Slider" gun in reference to it's key part, the exhaust valve.
Basically it is a fancy barrel sealing tee valve. The exhaust valve used is a homemade version of McMaster part number 4622K57. In the forward position, the input holes are connected with holes going to the chamber. In the back position, the input holes are isolated and the holes going to the chamber are exhausted to atmosphere. That means input flow is cut off in the same motion that exhaust the pilot chamber. The piston has a built in one way valve for a quick fill without harming performance. If I had a high flow air source available I could get up to .25" input flow, but currently flow is limited by the quick connect fitting. The stock can be pushed into the chamber when the gun is not in use, and I tried my best to give it a fancy paintjob. (3 days ago, waiting 7 days is impossible). I can get about 2 shots off per second. Faster ROF could probably be obtained with an electric 3 way valve instead of the slide valve, but I wanted to stay away from electronics.
OK, pictures say 1000 words so:
<a href="http://members.cox.net/ecyrb/slider/top.jpg">Best view IMO</a>
<a href="http://members.cox.net/ecyrb/slider/right.jpg">Right side</a>
<a href="http://members.cox.net/ecyrb/slider/left.jpg">Left side</a>
<a href="http://members.cox.net/ecyrb/slider/grip.jpg">Hand position</a>
<a href="http://members.cox.net/ecyrb/slider/piston%20parts.jpg">Piston with one way valve parts</a>
<a href="http://members.cox.net/ecyrb/slider/slide%20parts.jpg">Two parts from the slide valve</a>
<a href="http://members.cox.net/ecyrb/slider/slide%20assembled.jpg">Slide valve by itself</a>
<a href="http://members.cox.net/ecyrb/slider/slideclosed.jpg">Closed, filling position</a>
<a href="http://members.cox.net/ecyrb/slider/slideopen.jpg">Open, vent/firing position</a>
Anyway, of course I needed a loading system to keep up with the gun. I decided to use paintballs because they are cheap and fit with the scale of the gun. Seems to work fine. I find paint in there sometimes, but I think it is from the 3 year old paintballs, not a problem with the loading. Currently I just use a clip, but I am planning on getting a hopper to work.
<a href="http://members.cox.net/ecyrb/slider/bolt.jpg">Crude paint diagram</a>
<a href="http://members.cox.net/ecyrb/slider/noclip.jpg">Side view, no clip</a>
<a href="http://members.cox.net/ecyrb/slider/barrel%20position1.jpg">Top view, normal position</a>
<a href="http://members.cox.net/ecyrb/slider/barrel%20position2.jpg">Bolt midway through movement</a>
<a href="http://members.cox.net/ecyrb/slider/barrel%20position3.jpg">Closed position</a>
<a href="http://members.cox.net/ecyrb/slider/barreldisassembled.jpg">Inside parts of the loading system</a>Curently I am using a sprinkler valve spring, but I will try to make my own sometime.
<a href="http://members.cox.net/ecyrb/slider/finalwithclip.jpg"> Everything together, view 1</a>
<a href="http://members.cox.net/ecyrb/slider/finalwithclip2.jpg">view 2</a>
<a href="http://members.cox.net/ecyrb/sliderdemo.avi">Video of the gun in action</a> 3MB, encoded with DiVX. Let me know if you have trouble playing it, I can reencode it with something else if people have problems
UPDATE: Animation of the gun provided by GalFisk
http://galfisk.kaaven.net/img/cannons/c ... deauto.gif