The valve is the same sprinkler valve as in the plans. I used two 9 volt batteries in series with a momentary switch on a long wire for the release.
The results were great. We turned many heads in the park when we were launching. With each launch I turned up the pressure to see how high we could send the rockets.
A few burst because of the high pressures. The rockets we made did not have tape all the way around the tube body, leaving a spot for the rocket to burst. The next batch of rockets we make will be taped all the way around to avoid this failure mode. It was a lot of fun and fairly inexpensive at ~$20-30 for the total build. The sprinkler valve was the most expensive part at $12 from amazon, the rest was the pvc and the gauge. I had a handful of 9 volt batteries around, had the pvc primer and cement from an old plumbing repair a few years back and dug the switch, cross connect wire and small piece of perfboard out of the junk pile on my electronics bench. I may rebuild the trigger switch to be a nice hand held thumb switch or make a box to hold a plunger type switch, but those would just be for show, it works great now.
And a quick change of the rocket launcher tube and I have all the makings of a nice potato cannon, but that'll be a project for when the kids are a little older. The rocketry was fun, but who doesn't like shooting stuff with a cannon you made your self? I can't wait to bring this out in a few years with a new front end for launching projectiles instead of rockets.
