Simple Rubber Band Car With Cardboard Tube STEAM Activity

This is part of a series of Instructables detailing free science kits and activities developed by the spectrUM Discovery Area in Missoula, MT. The kits and activities are for use at home, in the classroom, or in a distance learning setting with teachers.

For more on how our museum shares these activities with students and teachers, see this video on YouTube.

Making a rubber band powered car is a great STEAM activity to do in the classroom or at home with some very inexpensive or free supplies you have lying around the house. These little cars travel pretty fast and far, and are a great way to experiment with various designs. Make a rubber band car from a cardboard tube (toilet paper or paper towel work great), rubber band, and some pieces of cardboard or food container lids.

We'll explore potential and kinetic energy, and extension activities also allow for explorations of torque.

Supplies

2x some sort of circular lid (peanut butter jar, mason jar lid insert, old CD or DVD, etc). To make these in bulk for the long term we've ordered these cardboard discs from Uline then drilled a hole in the middle.
A way to cut or drill a hole in the middle of the lid (drill, scissors, razor blade - use caution!)
Rubber band
Straw or wooden dowel
Pony bead (a piece of stiff tubing, metal hex nut or thick washer works just as well)
Paper clip
Tape or glue (optional)
Markers, paper, scissors, crayons to decorate (optional)

Step 1: Add Your First Wheel

If you want to decorate your car, it's easiest to draw or color on the cardboard tube before doing the next steps, so get your paper, crayons and markers and make it your own!

You'll need to create a hole in both of the lids or discs or whatever you use for the wheels of your car. The wheels just need to be bigger in diameter than your cardboard tube, and can be anything from peanut butter jar lids to discs made of cardboard. Depending on what you have and the material, a pair of scissors or razor blade or drill and drill bit will do nicely. They should be about 3/16" to 1/4" (4-6mm) in diameter, too much bigger than that and they might not work very well.

Then string the rubber band onto the paper clip so that it stays in place on the clip relatively well. Poke the other end of the rubber band through a hole in one of the wheels and pull it through so the paper clip rests right against the side of the wheel. The paper clip holds the rubber band in place when we wind it up - if you find that it spins around a bunch, simply add some hot glue (use caution) or tape to help it stay in place.

Step 2: Add Your Second Wheel

This part can be tricky - pull the rubber band all the way through the tube. It helps if you dangle it inside as far as it will go, then pull it through the other end. Keep it tight so it doesn't spring back inside the tube, and fish it through the hole in the other wheel. Once you get it through you'll need to keep tension on it until it's finished, but be persistent if it keeps springing back! If your rubber band does not fit easily through the holes in your wheel, create a bigger hole or use a smaller rubber band.

Step 3: Add the Bead and Straw

Next you'll want to add your pony bead (or suitable replacement). Push the rubber band through the hole in the middle of it, then keep tension on it - we're not done yet! This piece acts as a bushing for the car, keeping the straw from rubbing up against the wheel. As mentioned in the supplies step, you can use a washer of similar diameter to the hole, hex nut, piece of thick plastic tubing, etc. As long as it's relatively smooth on both sides and has a hole in the middle like a donut it will work, so get creative!

After you've added your bushing, just poke the straw through the loop at the end of the rubber band. Once done, this will keep the whole thing together. If you don't have a straw, try using a piece of dowel or popsicle stick, plastic cutlery, etc. Experiment with what works best for you.

Step 4: Launch Your Rubber Band Car and Experiment!

Now it's time to send it off! Hold the cardboard tube and spin the straw around a bunch to wind up the rubber band. If your paper clip spins around every once in a while, it's okay but you might want to put a piece of tape on it so you don't lose all of the energy you're storing for your launch.

Once you've wound up the rubber band, simply put the car on the ground and watch it roll away. How far did it go? For more about this step, see our video here:

Experiment with different designs for the car, or add pieces to it to change how it rolls. Try a few of these ideas if you're stuck:

What would happen if you added some other sized lids as wheels for your car?
Try adding a second rubber band tied onto your first - does your car go further or faster?
Will it go up a small incline or hill?
Does it go straight or pull to one side - how can you change where it goes?
How does it roll differently on different surfaces (carpet vs. a smooth floor vs. outside on rocky ground)?
What happens if you make the straw longer or shorter?
What happens if you use other things in place of the straw like a popsicle stick or plastic spoon?

Step 5: What's Going on Here?!

When you spin the straw around, the paper clip on the opposite side of the cardboard tube holds that end of the rubber band in place (if it doesn’t try adding a piece of tape or hot glue to secure it). The rubber band twists inside of the cardboard tube. Rubber bands are elastic, and when you spin them around with one end secured they turn into a spiral. This stores potential energy. When they twist back to return to their original, circular shape the energy is released as kinetic energy. This makes the straw spin around, but when it's on a surface it pushes against it instead of spinning freely like a propeller. As the straw tries to spin, it pushes the car along the ground.

To explore how torque - or rotational force - works, try using different sized wheels than your first two or vary the length of the straw.