Rubber-Band Powered Car

Skill Level: Beginner

Time: ~60 minutes

Engineering Fields: Mechanical Engineering, Robotics Foundations

You'll Build: A car powered only by a rubber band

Why This Activity Matters

Every engineered system, from cars to robots to spacecraft, starts with one question:

How do we turn energy into controlled motion?

In this activity, you’ll build a rubber-band-powered car and experiment like a real engineer. You’ll test designs, observe failures, redesign, and discover how tiny changes can make a big difference in performance.

No batteries. No motors. Just physics, creativity, and engineering thinking.

Rubber Band Car models using different materials:

Learning Objectives

By the end of this activity, you will be able to:

• Explain how elastic energy is stored and released

• Describe how torque and friction affect motion

• Build and test a wheel-and-axle system

• Improve a design using evidence from testing

Engineering Concepts You'll Use

• Elastic potential energy → kinetic energy

• Torque

• Friction (rolling vs sliding)

• Wheel and axle systems

• Engineering design cycle (build → test → improve)

Materials Needed

(Low-cost and easy to find)

• Cardboard (cereal box thickness works best)

• 4 bottle caps or cardboard wheels

• 2 wooden skewers or straight sticks

• 1–3 rubber bands

• Tape or hot glue

• Scissors

• Pencil

• Ruler

Optional

• Coins or washers

• Stopwatch

• Measuring tape

• Drinking straws (to reduce axle friction)

  
  

Step-by-Step Building Instructions

Build the Car Body

1. Cut a rectangle of cardboard about 15 cm × 7 cm.

2. This is your chassis.

3. If the cardboard bends, glue two layers together.

Create the Axles

1. Cut two skewers slightly wider than the chassis.

2. Poke holes near the front and back of the chassis.

3. Slide the skewers through the holes.

4. Optional but recommended:

   1. Add straw pieces around the skewers where they touch the cardboard to reduce friction.

Attach the Wheels

1. Poke a hole in the center of each wheel.

2. Push one wheel onto each end of the axle.

3. Secure with glue or tape so the wheels rotate with the axle.

4. Make sure all wheels touch the ground evenly.

Add the Rubber Band Engine

1. Loop one end of the rubber band around the rear axle.

2. Stretch the rubber band forward and attach it to:

   1. A paper clip taped to the front, or

   2. A notch was cut into the chassis.

3. The rubber band should be straight and centered.

Wind It Up and Launch

1. Turn the rear wheels backward to wind the rubber band.

2. Place the car on a smooth surface.

3. Release and observe what happens.

Test Like and Engineer

Don't stop at one run. Engineering test and compare.

Try Changing one variable at a time:

• Number of rubber bands

• Wheel size

• Added mass (taped coins to the chassis)

• Surface type (tile vs carpet)

  
  

Record:

• Distance traveled

• Time taken

• Stability (did it veer or wobble?)

Redesign Challenge

Choose one goal:

• Go farther

• Go faster

• Travel straighter

  
  

Change only one thing, then test again.

Ask yourself:

• What improved?

• What got worse?

• Why?

  
  

That’s real engineering.

Reflection Questions

• Where was energy stored before the car moved?

• Why does the car eventually stop?

• How does wheel size affect distance?

• Where is energy being lost in your design?

Real-World Engineering Connection

Rubber bands act like springs, which engineers use everywhere:

• Suspension systems

• Mechanical clocks

• Energy recovery systems

• Wind-up mechanisms

  
  

The same physics that moves your car also moves robots, vehicles, and machines.

Level-Up Ideas

• Add a gear system to the rear axle

• Build a race track and compare designs

• Graph distance vs number of wheel turns

• Design a car optimized for speed vs distance

  
  

What's Next?

Now that you’ve mastered energy and motion, you’re ready to explore:

• Gears and torque

• Structural strength

• Sensors and robotics