I think I'm starting to get a much better idea of what needs to be done to improve this cannon.
First off to all the people who come into this topic to discourage PVC pipe usage:
PVC pipe is not the final solution!
We are planning to move away from it for later designs. This was merely the first prototype. In my opinion the way we were using it was perfectly safe. We are going to move to a more appropriate storage tank eventually but theres nothing like getting your feet wet first and PVC was the cheapest, most avaiable material out there. The barrel will probably remain PVC but I don't honestly see the material failing... there's a large hole in it where the balloons exit and I'm quite sure the pressure will force it's way out that way than through the side of hte barrel.
Now onward to the good stuff:
Doug - What a great idea with the water. I would have never thought of it and am kind of curious as to how you came across it. Good ideas all around, they will be a basis for our final design for sure.
Dick - Hmm.. Three in parallel.... that's not such a bad idea. I'm definately thinking about converting them to be pnumatically operated. Would just drilling the appropriate hole in the top of each one after epoxying the place the eletric soliniod used to be be and then connecting them all to one of the kit's pnuematic soliniods do the trick and provide for a quick enough release of the diaphram? How is yours set up?
JesseeK - I like the calculations. If I didn't have so many finals and the such I'd dig into them a little deeper. I plan to set aside some time once school is out and try to dive into physics.
I've started looking around for an air storage tank with a large port on it. 3" would be ideal, then I could have a three inch manifold with 1inch ports going to spinkler valves and get the full force although I'm pretty sure that without drilling my own holes not many tanks will have this feature. My friend is talking about using the air pressure of a scuba tank... as long as I can regulate it down to 100-120psi I'll be good with using it as a source of air for the tanks.
When you guys use large tanks do you use some sort of pressure rated flexible tubing or do you just mount the tanks with the gun so it all moves?