The comeback can: a (mostly) easy project!

Comeback can

Here’s another fun and (mostly) easy project to keep your kids busy during the school break. Have you heard of a comeback can? It’s a can that you roll away from you, and when you call it, it rolls back! Okay, it sounds like magic, but in fact, it’s just a simple science project that uses a rubber band to store energy. I used to make these when I was a Girl Scout! (Today, I followed the instructions here, but you might want to check out the video at the end for an easier setup!)

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All you need for this project is a can with a securely fitting lid, some rubber bands, a moderately heavy weight (we used an old wheel lock nut), a pipe cleaner, a small screwdriver, and a hammer.

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First, I used the screwdriver to poke two small holes in the lid of the can, about 2 centimeters apart.

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Next, I used the screwdriver and a hammer to poke similar holes in the bottom of the can.

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I cut the rubber band once, so it was one long strip. Now comes the tricky part – you have to thread the rubber band through the holes in the bottom of the can, and through the holes in the top of the can, and tie a knot to secure the band. I’m sure I made this more complicated than I needed to, but you get the picture.

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Wrap the pipe cleaner around your weight and twist it at the top, leaving two “bunny ears” sticking up when you’re done.

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Attach the weight to the rubber band (just one side, not both), inside the can.

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Fix the lid back on the can with the weight hanging inside, and you’ve done it! Now show your kids how the comeback can works: place it on the floor, and gently roll it away from you. Eventually the can will stop, and will begin to roll back! If your kids learn the timing right, they can tell the can, “Come back!” just before it starts rolling back. It’s a pretty cool “magic” trick to impress the kids in the neighborhood.

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If my instructions are confusing, check out this YouTube video. It makes it look much easier… (Actually, he uses a slightly different method, and I think his is much simpler!!!)

The only downside to this project is that I had only one can, so the girls are fighting over it. Ah, the joys of school holidays! Claire and Heidi go back to school tomorrow (YAY!), but I know many of you still have several weeks to go! I hope this comeback can gives you some respite…

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