Hi Nik. My current setup is a 8 ft vacuum with a pvc piston pressure chamber (2" about 3 ft long). My main problem is when I fire the pressure chamber, the pvc piston is moving pretty fast, but not fast enough to let out all of the pressure at once, so there is a build up in pressure at the mylar film that breaks it just a few microseconds too soon so that the actual pressure going into the vacuum is not at full strength. My idea to fix this is to double up the mylar or add an additional layer or something... so that it takes a much bigger force to break the barrier before it lets loose. I have only run 1 test so far, and got 911 mph (1466.11km/h). It got cut off from the video, but the bulk of the air was released wwaayyyy after the ball was shot out.
In any case, going to have some fun this week shooting things supersonic
