A pneumatic cannon for launching plastic soda bottles.... or ketchup packets. Almost all parts can be obtained from home depot and probably any local hardware store with a plumbing section.
Bigger is cool looking... But not always better. I have found smaller more robust designs to be far more fun that the gigantic heavy cannons. I can recharge (with a foot pump) and reload in less than 30 seconds and hold this thing much easier than its heavy breathing counterparts. Other than this design, I no longer build using PVC as it does fail catastrophically.
I made this particular cannon to be used for physic's demos for middle and high school physics students. 2l bottle fail at surprisingly high pressures (relatively) and have served as a reservoir very well.
Step 1: Parts List
All parts are 0.5" unless specified
1 2l bottle of soda - minus the soda and washed out
1 .75" sprinkler valve with manual switch
1 45 elbow
2 female/male 90 elbow
1 female/threaded adapter
1 end cap
1 .5" thread-> .25" threaded bushing (mine is galvanized)
3 1.5" long pieces of pipe
2 2-2.5" long pieces of pipe
2 .5" female - .75" threaded adapter
1 4 wayfitting
1 Tire Stem with schrader valve (walmart or autoparts store) - home depot did not have this item
1 male threaded cap OR 1 gauge (might be listed as manometer)
Optional Add on (for bypass and a later project)
3 more 1.5" tubes
1 ball valve
1 45 elbow
1 3 way Tee