Hands-on Activity: Spool Racer Design & Competition

Contributed by: RESOURCE GK-12 Program, College of Engineering, University of California Davis

A photograph shows a pile of rubber bands of different colors, sizes, widths and materials, including elastic hair ties.
Students explore how elastic potential energy from twisted rubber bands can roll spools.
Copyright © 2014 Denise W. Carlson, ITL Program, College of Engineering and Applied Science, University of Colorado Boulder


Students see how potential energy (stored energy) can be converted into kinetic energy (motion). Acting as if they were engineers designing vehicles, they use rubber bands, pencils and spools to explore how elastic potential energy from twisted rubber bands can roll the spools. They brainstorm, prototype, modify, test and redesign variations to the basic spool racer design in order to meet different design criteria, ultimately facing off in a race competition. These simple-to-make devices store potential energy in twisted rubber bands and then convert the potential energy to kinetic energy upon release.

Engineering Connection

Engineers design motor vehicles to ensure safe and effective transportation. The key component of a motor vehicle is its engine, which serves as the "black box," converting chemical energy stored in gasoline into the kinetic energy of a moving car. Since energy conversion can take place between all different types of energy, fossil fuels are not the only kind of energy input engineers choose for their vehicle designs. For example, some vehicles use batteries to store electrical energy, which is converted into kinetic energy. In this activity, students play the role of mechanical engineers as they design spool racers that demonstrate how elastic energy stored in stretched rubber bands may be used to power spool-wheeled "cars," and experience how different design criteria affect the functionality of their spool racers.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

Suggest an alignment not listed above

Learning Objectives

After this activity, students should be able to:

  • Explain the difference between kinetic and potential energy.
  • Explain in simple terms the energy conversion mechanism of an engine.
  • Design with respect to certain design criteria.

Materials List

Each student needs:

To share with the entire class:

  • assortment of various elastic rubber bands, such as rubber bands of different sizes and materials, elastic hair bands, hair scrunchies, etc.
  • assortment of washers, such as metal and plastic washers of various sizes
  • extra toothpicks, in case needed
  • extra blank paper, in case needed for sketching additional designs
  • tape or some other way to mark off a racing track area
  • inclined plane for the end of the racing track ramp (<15°)


In the What Is Energy? lesson, we discussed that energy is the ability to make things happen. For example, energy is required to provide heat to the classroom when it is cold outside, and energy in the form of food supports our daily activities such as thinking and exercising. We know that energy can be neither created nor destroyed, so to obtain the energy we need, it must be converted from one form to another. For example, the thermal energy we feel from a heater is converted from some other form, such as the chemical energy stored in fossil fuels (such as when we burn natural gas) or electrical energy. Similarly, a motor vehicle converts some type of stored energy, such as gasoline, into movement, or kinetic energy.

The engines in vehicles, such as cars, airplanes and boats, make the energy conversion happen. Typically, engines consume gasoline to power the motion of vehicles such as cars and buses. Gasoline, which contains chemical energy in a highly compact form, is ignited in a closed chamber, producing a powerful, expanding gas that pushes pistons in a circular motion. A vehicle is moved forward or backward by transferring this circular motion into a linear motion through a crankshaft that connects the pistons to the wheels.

However, gasoline is not the only source of energy that can be converted to move vehicles. Many researchers are inventing, testing and creating vehicles that use new types of stored (potential) energy as alternatives to fossil fuels (which have a limited supply on Earth) to power our vehicles. For example, Tesla Motors uses lithium-ion battery packs to power their electric vehicles, so their cars do not need gasoline. Can you think of another type of potential energy that can be used to move an object?

No matter what kind of engine or battery a vehicle uses, these components must be well engineered to ensure they are safe, functional and reliable for people to use. In this activity, we will explore specifically how elastic energy—which is one kind of potential energy—can be converted into kinetic energy to spin a spool. You will play the role of mechanical engineers to improve your spool racer designs to meet certain design criteria.


energy: The ability to make things happen. More advanced definition: The ability to do work.

energy conversion: The change of energy from one form to another.

kinetic energy: The energy of moving objects. Anything in motion has kinetic energy. The faster an object moves, the more kinetic energy it has.

potential energy: Energy that is stored and can be used when needed. Energy can be stored in chemicals (food, batteries), height (gravitational), elastic stretching, etc.


Before the Activity

  • Gather materials and make copies of the Spool Racer Design Worksheet.
  • Place at one classroom location the supplies of assorted rubber bands and washers.
  • To see how to make the spool racers, watch Steve Spangler Science's Wind Up Racer – Sick Science #086 video (1 minute) at https://www.youtube.com/watch?v=k8yZwrEaXiw.
  • Provide floor space for students to test their racers.
  • Find space, inside or outside, to mark off a straight race track ending in an upward ramp. Use tape to mark off a track border that is no more than 5 feet wide with an inclined ramp (<15°) at the end of the track.

With the Students

  1. Hand out to each student: 1 spool, 1 toothpick, 1 pencil and 1 worksheet.
  2. Have each student choose from the classroom piles 1 rubber band and 1 washer.
    A photograph shows a pencil attached to a spool by a rubber band that goes around the pencil and through the center of the spool.
    A spool racer made from a pencil, rubber band and spool.
    Copyright © 2016 Victoria Lanaghan, ITL Program, College of Engineering, University of Colorado Boulder
  3. Direct students to follow these fundamental steps to make a basic spool racer:
  • Pinch and push the rubber band through the hole of the spool. It helps to use a toothpick or pencil to push it through.
  • Secure the rubber band at one end of the spool by inserting a toothpick into the rubber band loop that sticks out of the spool hole and taping the toothpick and rubber band loop to the spool. Break off any length of the toothpick that is wider than the spool diameter.
  • On the other side of the spool, pinch and push the other end of the rubber band through a washer. Then slide a pencil through the rubber band loop that sticks out from the washer.
  • Holding the spool in one hand, use your other hand to move the pencil around the spool two times, so it winds up the rubber band inside the spool.
  • Set the spool and pencil down on a counter or floor and let go. Watch the spool racer go!
  1. Present students with the engineering design challenge: Modify the design of your basic spool racer to meet the following three criteria—one criterion per trial (write these on the classroom board):

Criterion A: Make the spool racer run as fast as possible.

Criterion B: Make the spool racer run as far as possible in a straight line without overturning.

Criterion C: Make the spool racer run as far as possible over an inclined ramp (<15°).

  1. Direct students to each choose one of the three criteria and then brainstorm ideas for how they could modify their basic spool racers to better meet that criterion. Tell them they are permitted to use more than one of any single material, and swap out materials for different ones from the pile. (Or create your own design constraints.) Have students document on their worksheets their initial designs to meet one criterion. Let students assemble their spool racers according to their initial designs and give them time to test these prototypes in an open area and make changes to best meet the chosen criterion. After testing/improvement iterations, direct students to document on their worksheets their final designs.
  2. Next, have students choose a different criterion and repeat the initial design > prototype > testing > redesign process. Then repeat the process again with the third criterion, so that each student has designed to address each criterion. As needed, provide extra paper for students to document their designs.
  3. Next, challenge students to each design one spool racer that satisfies all three design criteria in the same prototype. Tell the students that these final designs will compete in a class tournament to determine a class champion. By now, expect students to be familiar with the process: brainstorm > design > prototype > test > redesign and repeat as long as time permits. Advise students to apply what they learned from experimentation with the previous designs.
  4. Group student into pairs to race their spool racers. For each paired race, the spool racer that travels to the higher point on the ramp within the marked boundary wins. From each race, the winner goes on to the next round to continue racing other winners. The final winner is the class champion of spool racing.


Safety Issues

Watch that students do not shoot rubber bands at each other.


Pre-Activity Assessment

Brainstorming: After walking through the steps for how to make a basic spool racer, have students independently come up with plans for how to modify their spool racers to best meet one design criterion. Before sketching these initial designs, ask students to discuss them in small groups: Why is this design criterion important? Is the energy conversion mechanism improved through enforcing this design criterion?

Activity Embedded Assessment

Design Presentations: After students build their spool racers based on their initial designs, give them 10-15 minutes to test their first prototypes and make changes. Walk around to check their progress. Several factors may contribute to the spool racer performance, such as:

  • Type of materials used
  • Quantity of each material used
  • Winding/overwinding of the rubber band
  • Position of the pencil on the side

Have students complete their final designs in the same fashion. Pick three or four students to explain to the rest of the class how their final designs met the design criteria and how energy conversion was improved.

Post-Activity Assessment

Project Reflection: After the tournament, have students compare their first and final designs. On their Spool Racers Design Worksheets, have them circle (or describe) the changes they made and explain why they made those changes. Ask them to make conclusions on how their final designs are coherent with all three design criteria. Ask the students: Did you have to give up some design ideas that you had for addressing individual criterion in order to satisfy all three criteria? Why is it important to address all three design criteria? (Keep in mind that an engine must be well engineered to ensure safe, functional and reliable transportation.) What is the trade-off you made between improvement of energy conversion and assurance of reliability?

Discussion: As a class or in small groups, have students discuss what other forms of potential energy might be used to move an object, such as a car. From where do these potential energies come, and what are the mechanisms of energy conversion behind them?

Additional Multimedia Support

For teacher and/or students to see how to make the spool racers, watch Steve Spangler Science's Wind Up Racer – Sick Science #086 video (1 minute) at https://www.youtube.com/watch?v=k8yZwrEaXiw.


Eric Anderson; Jeff Kessler; Irene Zhao


© 2014 by Regents of the University of Colorado; original © 2013 University of California Davis

Supporting Program

RESOURCE GK-12 Program, College of Engineering, University of California Davis


The contents of this digital library curriculum were developed by the Renewable Energy Systems Opportunity for Unified Research Collaboration and Education (RESOURCE) project in the College of Engineering under National Science Foundation GK-12 grant no. DGE 0948021. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: July 15, 2016