Sunday, June 06, 2010

On Building A Bottle Rocket Launcher

So I had this crazy idea that I would make bottle rockets with my kids this coming week. I fondly recall doing this in 7th grade, and the excitement and enthusiasm this project brought to everyone involved. Then I started planning out the nitty gritty.

One thing I failed to consider fully was how to actually launch these rockets. In 7th grade, the launch pads had been around the school for several years, made by some ambitious teacher years ago. I had no such resources, and set about to making my own launch pad.

I've never been one to look at pre-made plans devised by others, preferring to rough it out, and find my own way to doing things. So I set about designing my own launch pad. After some thought, I came up with these rather detailed blueprints on the back of a piece of 3/4" plywood:
However, I had failed to take into account a rather crucial element: I had no way to pressurize the rocket. I had an electric pump suited to fill up car tires, but this would not work. What would the children do as I filled up their rockets with a flip of a red switch? I would rather have the kids themselves pump up their rockets, since that's part of the fun. No, I would need a manual pump for this project. A manual pump I did not have. After debating with myself on whether to shell out the $10.23 for a Bell Bike Pump, since that amounts to an strenuous hour of yelling, running, and shepherding children, I bought the pump.

Now, being the thrifty fellow I am, I have never bought construction materials. I have built many many a things, ranging from chairs to a full size working ballista (it shot tennis balls), but have never paid for lumber or nails, or tools, for that matter.

My grandpa was a general contractor, and as such, left behind a large number of tools and materials after he passed away. Although my dad's parents lived with us for the last 15 years, I have never really known them on a terribly personal level. For whatever reason, I only got to know my grandpa after he passed away a few years ago, and of all ways, through his tools. He salvaged everything, from light switch cover panels to roofing nails. There's something about the way he stored all the odds and ends, nuts and bolts in old Macadamia nut cans, or the abundance of the stiff white nylon twine that he used to tie everything together with, that seemed oddly familiar, and oddly familial. I know it sounds corny, but I do feel a connection to him when I build things. With every turn of the hand-powered drill, with every stroke of the vintage Japanese saw, I can imagine my grandpa doing the same thing 50 years ago, back when Hawaii wasn't even a state, building not only houses, but a life for his family. I do feel proud, in an odd way, that I'm carrying on one of the few legacies our family has, even if I'm using it to build a rocket. My grandma gives me strange looks when she sees my projects, but she gave those same looks to my grandpa when he was alive, so I suppose not much as changed between generations.

Back to the rocket launcher. After 4 hours of Junkyard Wars-esque building, I finally assembled my rocket launcher. After hours of looking for a nut that would fit this one bolt, and trying to cut custom metal brackets, I produced this monstrosity:Though not the prettiest thing in the world, it works:

Tomorrow I'll do an actual test shot, since 9:00 at night is not the time to go to the park to try out such things.

Yup, four hours for something I could have bought online, or just decided it was too much work for a summer class I get paid way too little for. There are some moments when I have to stop and ask myself why I bother putting so much effort into these things.

My mom, being the superstitious type that she is, drew my attention to today's horoscopes for Aquarius:

You succeed because you work hard, and the tenacity and sense of purpose you bring to your work is rapidly becoming the stuff of local legend. A significant reward approaches.

Interesting, though such things are pure hokum. I'm taking the horoscope to mean some nice parent will bring me a box of cookies one day. Or a big wad of cash. One can only hope.

Truth be told, I'm really still a little kid at heart that likes to make cool things. This class is as much for my own amusement as it is for the kids. And plus, having my own bottle rocket launch pad will make this a very fun summer.


  1. Impressive! How does the launcher work? What are you pumping air into and how does the release mechanism work?

    I love reading these blog posts BTW. You have such interesting and funny experiences, thoughts, and stories to share.

  2. It's a simple launcher. The manifold basically works to press the stopper against the soda bottle. The bottle is held in place against the manifold by two nails, which are the release mechanism. Very simple, but it works very well.

    The air is pumped in by a bicycle pump attached to a standard sports ball needle.

    Thanks for reading these posts. It's nice to know I have loyal readers.

  3. Cool. I don't think I've ever made a bottle rocket before. I was just googling bottle rockets and read that adding some water to the bottle helps launch them further. Did you use water at all or was it purely air?

    And it's pretty cool you have like a junkyard of stuff at your house that you can use to build stuff. Reminds me of Junkyard Wars.