Please remember that the act of pressurizing a vessel can be dangerous and even deadly. If you are not sure if something is correct or doubt your construction in anyway, DO NOT USE IT.
USE COPIOUS AMOUNTS OF PRECAUTION AND COMMON SENSE.
This instructable is for information only and I assume no responsibility for your actions after reading it.
Step 1: The Basic Design
I wanted to be able to use both a bike pump and an compressor or compressed tank so there is both a schrader valve and a compressor fitting.
I wanted it to be electrically controlled, so I used a sprinkler valve and and string of 3 9v batteries to power the valve.
The most important thing I wanted to change was how the bottles were placed on the launcher, because they are 1/4 full of water other designs required the entire unit to be tilted down for loading. I thought this was dangerous since it allowed the possibility for an accidental horizontal launch if the system was primed. So I made a sort of quick change system that allows for much faster cycling and more fun per minute!!!