The 3rd grade boy across the street is pretty smart, and his mom is doing her best to make sure he’s got some pretty broad horizons (He goes to a Waldorf inspired charter school, I went to a Waldorf school through 7th grade, so we’ve got some similar background).
Anyway, he and his mom came over to ask if I had some scrap wood for some raised planters, then he found an inner tube we’d cut up for some project, and started playing with the valve, and that led to us launching a soda bottle with compressed air. Then we knocked on another neighbor’s door to apologize for the intrusion and retrieved our bottle from her yard, but got thinking about launchers rather than doing it manually.
So he and I went into the shop to see what we could come up with. With a little help he learned how to use a drill press, and a Japanese pull saw, and a file, and we ended up with this:
Yeah, there’s an additional piece of wood that probably isn’t strictly necessary, but when a third grader tells you “I think we need a piece there”, well, who am I to argue?
YouTube video of a launch here, or embedded below
We wrapped the baking soda in paper towel to slow down the reaction long enough to put the thing on the launcher, which is all that goop left on the launcher.
-- Dan Lyke, Petaluma California, http://www.flutterby.net/User:DanLyke