Archive June, 2011

Rocket Piñata

19 June, 15:28, by Simon Clark

For the last year or so, we’ve been using rocket launchers, based loosely on the Make Magazine design, as a community outreach tool, taking them around to various community events and letting kids build and fire their rockets. Recently though, I wanted to up the ante a bit, and give the kids a reason to take care with their rocket building. Target practise was the obvious answer, but you know what’s better than targets? Targets that vomit candy and toys when you hit them, that’s what.

I started out with four balloons tied at their knots, classic flour and water papiér maché, taking care to make the walls as thin as I could. Our last piñata for my daughters birthday party was so solid, it took a grown man with a baseball bat, walloping it against a concrete floor to break it. I can still hear the kids crying. No, for this one, one layer of paper, with a second ‘patch job’ to just fill in any gaps. The resulting piñata felt flimsy enough that I felt the need to be extra careful transporting it.

For piñata fillings, I had to be careful too. The plan was to hang this thing 40′ up in a tree on a hot day, so chocolate was out, so was anything heavy, like the 12 large rubber bouncy balls that I bought. (As a side note, our local Old Navy has a bubble gum machine that spits out large kick-ass bouncy balls for a quarter. Best bouncy ball deal out there). I also stuffed a couple of sheets of dollar store tissue paper in the piñata to slow the candy down from a single puncture.

To get the pinñata into the tree, we used a rocket to fire a string over a branch that was about 40′ up. The launcher was set at about a 15º angle from the piñata.

As for the rockets themselves, the kids typically run with their own ideas, but our official design for these have evolved over time. We have rolling tubes for making the body out of letter-sized paper and masking tape. These have three strips of packing tape applied lengthwise, so that the rockets are not too tight over the launch tube. An end cap under the nose cone has proven to be very useful to prevent nose cone blowouts. We also have a nose cone jig that makes rolling nose cones a snap. This was made from a drumstick ice cream wrapper, filled with a glue and lentil mix to firm it up. Fins are cut from this pattern. If cut, folded and taped carefully, they’ll provide a stable and aerodynamic fin profile with a 1.5º rifle, giving the rocket added stability.

Our launcher has an adjustable incline, and an integrated pressure gauge, making it good for repeatable accuracy firing. I’d ideally like to refit it with a cammed clutch for inclination adjustments, and a built in inclinometer.

We introduced the world to rocket piñata at our park party on June 18th. We had a table where the kids could make their rockets, tons of supplies, and lots of kids. The rocket designs ranged from precise and well-built to super creative (one had leaves for fins) to completely wobbly. At thirty feet, about 1 in 4 rockets were able to hit it, As for the piñata, it ate 6 rockets whole before finally giving up and spewing forth it’s delicious contents. All in all, a raving success. We’ll be doing this again.