Introduction: Easy Rubberband Car
This is an easy to make rubberband car using a paper towel tube for the body. I've made these cars with groups of kids at Library programs several times and it's always lots of fun. You’ll need a paper towel tube, two old CDs, a couple of pencils, one jumbo paperclip, about 5 rubberbands (these MUST be #14 size! it won’t work nearly as well, if at all, with fatter or thinner rubberbands), lots of masking tape, scissors, a ruler, a single-hole punch, and some corrugated cardboard for front wheels.
Step 1: Punch Holes for Axles
Use the hole punch to make holes for the axles, two straight across from each other on either end. It helps the car roll better if the wheel holes are lined up and square with each other, front to back and side to side. Using a ruler to draw a line down the side of the tube can make it easier to line up the holes.
Step 2: Enlarge Axle Holes in Tube
Use the big end of the jumbo paper clip to enlarge all the axle holes in the paper towel tube. If you just push a pencil through the hole punch hole it will be too tight to turn freely. Where the pencils fit into the wheels needs to be a tight fit. Where the pencil goes through the tube/body needs to be a loose fit (seems obvious, but it’s a common problem).
Step 3: Front Wheels and Axle
The front wheels and axle! I prepared the front wheels ahead of time, they are 2 1/2 inch diameter circles cut from corrugated cardboard with a starter hole poked in the center with a sharp pencil. Push the pencil through the wheels so that they fit tightly on the pencil--the pencil should turn freely in the holes in the paper towel tube.
Step 4: Build Up Rear Axle With Tape
Wrapping about 2 1/2 feet of masking tape around the pencil should build it up enough to fit tightly in the hole of a CD–but it depends on how neatly or messily you wrap. Both neat and messy wrapping work, but you may need to adjust by squishing down the resulting blob of tape, peeling away a turn or two of tape, or adding a turn or two. Do one on either side of the body, but not so close that it rubs!
Step 5: Put on the Rear Wheels
Squish the CDs onto the tape blobs on the back axle. These should be a tight fit and be more or less straight and parallel with the paper towel tube. You can add or take away tape to get a good fit.
Step 6: Make a Rubberband Chain
Making the rubber band chain. I’m not even going to try to explain this with words. Many adults already know how to do this. A surprising number of kids don’t, but it’s an important life skill. If you're working with a group and one kid is good at this, ask them to show the ones who don’t get it. Again, for best results, you really need to use #14 size rubber bands. The rubber band chain should be about 5 rubber bands long.
Step 7: Attach Jumbo Paper Clip to Rubberband Chain
Attach the jumbo paper clip to one end of the rubber band chain. Usually 5 #14 rubber bands is long enough, but it varies–they might need to take one away or add one. (You can’t really tell until it’s installed in the car and you try it out. Yep, that means you might have to take it all the way out and put it all the way back in again–aww, man!)
Step 8: Drop the Clip Down One Side...
Use the weight of the paper clip to drop one end of the rubber band part way down on one side of the rear axle.
Step 9: ...and Out the Other
Then flip the car over and tilt it up so the paper clip comes back out again on the other side of the rear axle.
Step 10: Pass Paper Clip Through the End Rubber Band
Thread the paper clip through the very end rubber band in the chain and pull it through all the way.
Step 11: Rubber Band Chain on Rear Axle
It should look like this. When you turn the axel one way the rubber band will catch and wind up. If you turn the pencil the other way it will just spin–so that it will free wheel after expending all its wound-up-ness. This won’t happen if you use different size rubber bands and the cars will just stop when the rubber band unwinds instead of coasting and cruising.
Step 12: Pass Rubber Band Chain Back Through Tube
Next, you just drop the paper clip back into the tube so that you can grab it when it comes out of the front end.
Step 13: Cut Two Slits to Hook Rubber Band Onto
Snip two little slits, maybe a half inch deep, into one side of the the front of the tube–this is so you can hook the rubber band chain onto the edge of the tube…
Step 14: Done!
When the rubber band is hooked onto the slits, it looks something like this. You can remove the paper clip at this point, or leave it if you’re just busting to wind this puppy up and give it a whirl!
Step 15: But Not Like This
One common problem with this part is that if the rubber band is touching the front axle before being hooked to the front of the tube, it will rub and the car won’t roll. Hook the rubber band straight to the front edge of the tube without going over the front axle.
I had hot glue guns on hand and all manner of fancy stuff for decorating the cars. I made a start and finish line with masking tape to facilitate racing. That's it--have fun!!