Design Challenge

You are a team of engineers given the challenge of examining the braking process using the materials provided. Then, you’ll design an improvement for a bicycle braking system that will make it brake more smoothly and safely. As a team, present your design to the class.

Criteria

• Must brake more smoothly and safely.

Constraints

• Use only the materials provided.

1. Break class into teams of 3-4.
2. Hand out the Give Me a Brake worksheet, as well as some sheets of paper for sketching designs.
3. Discuss the topics in the Background Concepts Section. You may also direct students to look at the brake systems on their own or a friend’s bicycle in advance of the activity.
4. Review the Engineering Design Process, Design Challenge, Criteria, Constraints and Materials.
5. Provide each team with their materials.
6. Instruct teams to examine the braking process using the materials provided to them.
   ● Consider the marble or small ball to be the object in motion which they need to slow, stop, or prevent from moving.
   ● Roll the ball through the three tubes provided. One is a stiff PVC pipe, the second is a paper towel roll, and the third is a foam tube used to insulate water pipes.
   ● Use your hand, a rubber band, string, or other materials, see if you can prevent the ball from going all the way through the tubes. If you succeed, you’ll have applied a brake within the tube.
   ● Try to simply slow it down using the materials provided.
7. Ask students to answer the following questions about their examination:
   ● What advantages did the foam tube have over the other two materials in terms of the ability to slow or stop the rolling ball/marble?
   ● Which material do you think would hold up best over time? Why?
   ● Which material gave you the greatest control over the speed of the ball traveling through the tube? Why do you think this was?
   ● What provides the “force” in your tube experiments? Where is the friction?
   ● Which tube material required the least amount of friction to stop the ball/marble? Why do you think this was true?
   ● Bicycle rim brake pads are made of a moderately hard plastic, and are sometimes made of leather. Why do you think these materials are preferred?
8. If possible, have students examine how the common rim brake operates on a working bicycle.
9. Instruct teams to decide what they want to change in the design to improve bicycle safety. They should discuss materials they might use (metals, plastics, foam, leather), whether they think the size of the pads, or the number of pads might impact the performance of the brake, and finally how easy their new brake will be to operate for someone new to bicycling.
10. Students sketch their new braking system and include a list of the type of materials they will use in construction. They should call out the areas of the design they have changed and explain why their team came up with these ideas, specifically how it will increase safety.
11. Teams present their designs to the class.
12. As a class, discuss the student reflection questions.
13. For more content on the topic, see the “Digging Deeper” section.

Student Reflection (engineering notebook)

1. How do you think your design revisions will impact the manufacturing cost of the brake?
2. What materials will be used in manufacture? Why did you select these?
3. What is unique about this design? (two sentences maximum)
4. How will your new design impact the longevity or functional life of this brake?

The lesson can be done in as little as 1 class period for older students. However, to help students from feeling rushed and to ensure student success (especially for younger students), split the lesson into two periods giving students more time to brainstorm, test ideas and finalize their design. Conduct the testing and debrief in the next class period.

Force: By pushing or pulling on an object we give it energy and cause it to move, stop moving, or change direction. For example, when we apply a bicycle brake, we exert force on the wheel causing it to slow or stop rotating. The force produced may cause the body to deform — in bicycles, the wheel is compressed.

Kinetic Energy: energy that a machine or material possesses, caused by its motion.

Friction: a term that describes how much resistance there is for two objects to move over another. The greater the friction, the more difficult it is for the two objects to move smoothly. With less friction, objects move easily and smoothly against one another.

Heat: a form of energy associated with the motion of matter. Heat can be generated in many ways, such as chemical or nuclear reactions, and friction.

• Braking System: System used to slow, stop, or prevent the motion of a machine, such as a car or bicycle.
• Constraints: Limitations with material, time, size of team, etc.
• Criteria: Conditions that the design must satisfy like its overall size, etc.
• Engineers: Inventors and problem-solvers of the world. Twenty-five major specialties are recognized in engineering (see infographic).
• Engineering Design Process: Process engineers use to solve problems. 
• Engineering Habits of Mind (EHM): Six unique ways that engineers think.
• Force: By pushing or pulling on an object we give it energy and cause it to move, stop moving, or change direction. For example, when we apply a bicycle brake, we exert force on the wheel causing it to slow or stop rotating. The force produced may cause the body to deform — in bicycles, the wheel is compressed.
• Friction: A term that describes how much resistance there is for two objects to move over another. The greater the friction, the more difficult it is for the two objects to move smoothly. With less friction, objects move easily and smoothly against one another.
• Heat: A form of energy associated with the motion of matter. Heat can be generated in many ways, such as chemical or nuclear reactions, and friction.
• Kinetic Energy: Energy that a machine or material possesses, caused by its motion.
• Iteration: Test & redesign is one iteration. Repeat (multiple iterations).
• Prototype: A working model of the solution to be tested.
• Rim Brakes: Force is applied to the tire by the bicyclist squeezing a level on the handlebar.

Internet Connections

• Bicycle Brake Systems
• A Short Course on Brakes

Recommended Reading

• How Cars Work by Tom Newton (ISBN: 0966862309)
• Automotive Brakes and Antilock Braking Systems by Kalton C. Lahue (ISBN: 0314028382)
• Brake Systems by L. Carley (ISBN: 1557882819)

Writing Activity

Write an essay or a paragraph describing how the brakes operate on another machine to slow, stop, or prevent motion. Choose from the following products: motorized wheelchair, basic wheelchair, car, airport luggage cart, walker.

Alignment to Curriculum Frameworks

Note: Lesson plans in this series are aligned to one or more of the following sets of standards:  

• U.S. Science Education Standards (http://www.nap.edu/catalog.php?record_id=4962)
• U.S. Next Generation Science Standards (http://www.nextgenscience.org/) 
• International Technology Education Association’s Standards for Technological Literacy (http://www.iteea.org/TAA/PDFs/xstnd.pdf)
• U.S. National Council of Teachers of Mathematics’ Principles and Standards for School Mathematics (http://www.nctm.org/standards/content.aspx?id=16909)
• U.S. Common Core State Standards for Mathematics (http://www.corestandards.org/Math)
• Computer Science Teachers Association K-12 Computer Science Standards (http://csta.acm.org/Curriculum/sub/K12Standards.html)

National Science Education Standards Grades 5-8 (ages 10-14)

CONTENT STANDARD B: Physical Science

As a result of their activities, all students should develop an understanding of

• Motions and forces 
• Transfer of energy 

CONTENT STANDARD E: Science and Technology

As a result of activities in grades 5-8, all students should develop

• Abilities of technological design 
• Understandings about science and technology 

National Science Education Standards Grades 9-12 (ages 14-18)

CONTENT STANDARD B: Physical Science 

As a result of their activities, all students should develop understanding of

• Motions and forces 
• Interactions of energy and matter 

CONTENT STANDARD E: Science and Technology

As a result of activities, all students should develop

• Abilities of technological design 

Next Generation Science Standards Grades 2-5 (Ages 7-11)

Matter and its Interactions 

Students who demonstrate understanding can:

• 2-PS1-2.  Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose.

Energy

Students who demonstrate understanding can:

• 4-PS3-1. Use evidence to construct an explanation relating the speed of an object to the energy of that object.

Next Generation Science Standards Grades 2-5 (Ages 7-11)

Engineering Design 

Students who demonstrate understanding can:

• 3-5-ETS1-1.Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
• 3-5-ETS1-2.Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
• 3-5-ETS1-3.Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

Next Generation Science Standards Grades 6-8 (Ages 11-14)

Engineering Design 

Students who demonstrate understanding can:

• MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

◆Standards for Technological Literacy – All Ages

The Nature of Technology

• Standard 1: Students will develop an understanding of the characteristics and scope of technology.
• Standard 3: Students will develop an understanding of the relationships among technologies and the connections between technology and other fields of study.

Technology and Society

• Standard 4: Students will develop an understanding of the cultural, social, economic, and political effects of technology.
• Standard 7: Students will develop an understanding of the influence of technology on history.

Design

• Standard 8: Students will develop an understanding of the attributes of design.
• Standard 9: Students will develop an understanding of engineering design.

Brake Operation

Optional Advance Step: Have students examine the operation of standard rim brakes on a bicycle.  This may be done as a group in the classroom if a bicycle is available, or students could be directed to examine the operations of the rim brake on their own or a friend’s bicycle outside of class.  Have students draw a sketch that illustrates how the brake operates (showing pads, tire, and rim in both the “released” and “braking” positions.

Step One:

As a team, you will examine the braking process using the materials provided to you.  Consider the marble or small ball to be the object in motion which you need to slow, stop, or prevent from moving.  Roll the ball through the three tubes provided.  One is a stiff PVC pipe, the second is a paper towel roll, and the third is a foam tube used to insulate water pipes.  Using your hand, a rubber band, string, or other materials, see if you can prevent the ball from going all the way through the tubes. If you succeed, you’ll have applied a brake within the tube. Try to simply slow it down using the materials provided.

Step Two: Answer the questions below

Questions:

1. What advantages did the foam tube have over the other two materials in terms of the ability to slow or stop the rolling ball/marble?

2. Which material do you think would hold up best over time? Why?

3. Which material gave you the greatest control over the speed of the ball traveling through the tube? Why do you think this was?

4. What provides the “force” in your tube experiments? Where is the friction?

5. Which tube material required the least amount of friction to stop the ball/marble? Why do you think this was true?

6. Bicycle rim brake pads are made of a moderately hard plastic, and are sometimes made of leather. Why do you think these materials are preferred?

Your challenge is to work as a team to devise an improvement in design for a bicycle braking system that will make it brake more smoothly, and therefore more safely. You may work to improve the rim brake, or come up with a completely new design.  Propose your ideas and theories as a group. Then, as a team, develop a proposal which you will present to your class.

Step One: Observation

1. Examine how the common rim brake operates…if possible look at one on a working bicycle.
2. Decide — as a team — what you want to change in the design to improve bicycle safety. Discuss materials you might use (metals, plastics, foam, leather), whether you think the size of the pads, or the number of pads might impact the performance of the brake, and finally how easy your new brake will be to operate for someone new to bicycling.
3. Draw a sketch of your new braking system on the other side of this paper, and be sure to include a list of the type of materials you’ll use in construction. Call out the areas of the design you have changed and explain why your team came up with these ideas, specifically how it will increase safety.

Step Two: Answer the questions below

Questions:

1. How do you think your design revisions will impact the manufacturing cost of the brake?

2. What materials will be used in manufacture?  Why did you select these?

3. What is unique about this design? (two sentences maximum)

4. How will your new design impact the longevity or functional life of this brake?

Present your ideas to your class….pretend they are individuals who are considering funding the manufacture of your new brake system.

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