fuel cell book - awim.org · sae international is a nonprofit scientific organization dedicated to...

The Design Experience

The Fuel Cell Challenge

Lesson Plans are not included in this document.

Check out the sample lesson plan located in the curriculum

resources.

SAE International is a nonprofit scientific organization dedicated to the advancement of mobility technology in order to better serve humanity. A global society of nearly 121,000 members, SAE is the leading professional organization for engineers and scientists involved with land, sea, air, and space mobility. Its members come from all branches of engineering, science, and technology. SAE creates and distributes information through meetings, books, technical papers, magazines, standards, reports, continuing education programs, and electronic databases.

SAE’s educational goals include the promotion of excellence in math, science, and technology education in grades K-12 and beyond through the development of curriculum materials and volunteer mobilization. To this end, SAE invites and supports collaboration and partnership among schools, industry, community organizations, teachers, volunteers, and students.

Established in 1986, the SAE Foundation for Science and Technology Education secures funding from corporations, individuals and other sources to develop and sustain the K-University education programs of SAE International. One such program funded by the SAE Foundation is A World In Motion (AWIM).

The SAE Foundation strives to be a global leader in the promotion and support of science, technology, engineering and mathematics programs and seeks to expand the mobility engineering profession. To support these efforts, please contact the SAE Foundation at 724-776-4841.

Copyright © 2009 by SAE International™. All rights reserved. Permission to reproduce the teacher manual and student reproducible is hereby granted by SAE International to teachers for classroom use.

Development and distribution for the A World In Motion® Fuel Cell Challenge has been made possible through a generous grant from General Motors.

Acknowledgements This program is supported by contributions to SAE International® and the SAE Foundation, Warrendale, Pennsylvania.

David Schutt, SAE International, Executive Vice President & COOScott Klavon, Director, Educational ProgramsMatthew M. Miller, Manager, SAE K-12 Education ProgramsCarson Walburn, Director, SAE Foundation

Written and Developed by SAE InternationalDr. Charles M. Lovas, Project DirectorKen Francis, Program Developer, K-12 Education Programs

Layout by DesignWorksWayne Silvonic, Art DirectionLucy Matyjaszczyk, Graphic Designer Braxton Harris, Fuel Cell Animation

Illustrations by Zoltun Design, Pittsburgh, PAAmanda Swadlo, Amy Wohar, Warren Wolowiec

Advisors, Consultants, and ReviewersGreg Reiva, DeAndre Jamison, Kay Larson, Kathleen M. O’Connor, Joseph G. Langhauser, Chris Ciuca, Julie Nalducci, Gail Hartmann, Goodman Research Group

We would like to thank the following schools for their participation in the field testing of the curriculum.

Classroom TeachersJonathan Anderson, Dianna Bonney, Dan Butchko, Geoff Casey, Rick Comeau, Keri Domer, Rich Gebrosky, Dee Guarino, Walter Hickey, Mary Beth Jacquay, Elaine Kohen, Patrick Lalko, Susan Leeds, Kelly Leguizamon, Taherah Mahajerin, Susan McCoy, Judith Meier, Siobhan Sackey, Jennifer Sanderson, Minerva Santerre, Nancy Schunke, Janine Scott, Nicole Trombetta

Special thanks to:The students in the thermal design classes in the mechanical engineering department at Southern Methodist University for testing the materials.

The Department of Energy for promoting fuel cell education through their annual Middle School Science Bowl http://www.scied.science.doe.gov/nmsb/default.htm

Students Fueling The Future’s Jayne and Richard Howard for their tireless efforts in promoting fuel cell education http://www.studentsfuelingthefuture.com/

The National Academies for providing What You Need To Know About Energy booklet.

Asa Mercer Middle School, Seattle WABenjamin Franklin Middle School, Teaneck NJBradshaw Mountain Middle School, Dewey AZCarrollton Middle School, Carrollton MIConestoga Public Schools, Murray NEDerby Middle School, Birmingham MIDunbar Middle School, Lubbock TXHeilmann Middle School, Detroit MIHoward Middle School, Orlando FLIngomar Middle School, Pittsburgh PA

K-8 International Center, Miami FLLinwood Middle School, North Brunswick NJMaimonides School, Brookline MANorthwest Middle School, Travelers Rest SCOrangewood K-8 School, Phoenix AZPrairie Mountain School, Eugene ORSt. Patrick School, White Lake MIStanford School, Stanford MTVassar Jr. High School, Vassar MIWm Diamond Middle School, Lexington MA

The Fuel Cell ChallengeTHE ENGINEERING DESIGN EXPERIENCE

Table of ContentsIntroduction to the Challenge ............................................ i

Lesson Plan Structure ..........................................................x

Fuel Cell Design Challenge Activity Calendar ...... xii

1 Reading and Evaluating The Request for Proposals (RFP) ................................................................ 2

Request for Proposals .............................................6Evaluating the RFP Log Sheet ...............................8

2 Team Formation and Recordkeeping ...................... 9GDT Engineer Design Log ..................................15Design Log ....................................................... 16-19

3 Looking at Powered Vehicles ....................................21Automobile Components Sheet .........................25Identifying Automobile Components Sheet .....26Vehicle Forces Sheet ............................................ 27Identifying Vehicle Forces Sheet ........................28

4 What We Know About Fuel Cells ..............................29PEM Fuel Cell Data Sheet ...................................34PEM Fuel Cell: Student Diagram ......................35PEM Fuel Cell: Team Diagram ............................36PEM Fuel Cell Diagrams ................................37-42PEM Fuel Cell Operating Procedures ..............43

5 Chemistry of Electrolysis .............................................46Hydrogen And Oxygen Production Data Sheet ..........................................................51

6 Using the Fuel Cell to Produce Power .................52Producing Power at No Load Data Sheet ........ 57

7 Powering an Electric Motor and Gearbox ...........58Powering an Electric Motor and Gearbox Data Sheet .........................................................65Identifying Automobile Components Sheet .....66

8 Looking at Green Design .............................................67Green Design Guidelines Sheet ........................71Evaluating Materials for Greenness Sheet ....... 72

9 Writing the Design Brief ................................................74

10 Building and Testing the Prototype ......................80Vehicle Assembly Procedure ...............................88Prototype Test Data Sheet ...................................90Speed Test Data Sheet ........................................91Endurance Test Data Sheet .................................92Load Test Data Sheet ...........................................93

11 Assembling, Testing, and Adjusting the Final Design ......................................................................95

12 The Final Presentations ..............................................98

Student Reproducible Master ..................................... 102

Appendices ........................................................................... 121Safety and Precautions ...................................... 129Finding a Classroom Volunteer ........................ 131Reflecting on the Engineering Design Experience........................................................ 140Forces and Newton’s Laws of Motion ............ 141Electrolysis ............................................................ 143Energy, Work, and Power .................................. 145Looking At Gears .................................................147

Introduction to the Challenge

Introduction

i

To survive and thrive in the society of tomorrow, our children need educational preparation that builds upon the technology of today. The needs of our society mandate that we educate students to be scientifically and mathematically literate and be able to ask and answer questions, assimilate knowledge, solve problems, communicate, and work cooperatively toward common goals.

As educators we are called upon to go beyond the practice of dispensing scientific information and teaching students to manipulate rote formulas; we must also strive to help our students to achieve an inherent understanding of scientific phenomena and processes, and to use mathematics as an appropriate tool to solve problems.

Middle school students need to be competent and to feel confident in their abilities to use scientific methods to explore, conjecture, and reason logically and to gather and manipulate information in order to gain useful knowledge about the world around them. These abilities are nourished and nurtured when activities grow out of interesting problem situations, and they are further stimulated and developed through the interactive, cooperative processes of discussing, reading, and writing about their experiences.

Welcome to an adventure! The SAE International has developed A World In Motion: The Design Experience as an opportunity for students and teachers to use science, mathematics, and technology to explore the process of design. This three-week curriculum includes a manual for teachers, student reproducible masters, hands-on laboratory materials for constructing prototypes, and web-based tutorials.

LINKShttp://www.sae.org http://http://www.saefoundation.org/ http://www.awim.org

ABOUT THE CHALLENGEThe Fuel Cell Challenge is one of a series of challenge programs developed for the middle school curriculum A World In Motion: The Design Experience. It is intended for students in grades 6 through 8. For three weeks the students engage in a problem-solving context for which they must create a design to address a particular need.

Students receive a letter from a fictitious toy company, Green Design Toys (GDT). Green Design Toys is interested in receiving new designs for toys that are environmentally friendly and are powered with alternative power sources

ii

and fuels. This letter asks students to work in teams to design a vehicle that can meet specific performance goals. Students are asked to keep a design log in which they record the results of experiments, design sketches of their vehicles, and performance data. The program culminates in student presentations of their working models and a discussion of the design teams’ efforts to address the challenge.

This challenge presents students with the opportunity to investigate a new and developing technology; the fuel cell. Over the course of the curriculum, a variety of activities introduce students to the development and use of fuel cells, types of fuel cells, and hands-on experiments with a PEM (proton exchange membrane) fuel cell to produce electricity to power an electric motor.

Students begin the Engineering Design Experience (EDE) process with goal setting activities that encourage team building and identifying tasks. Students continue to work in teams to develop the prototypes of models through which they explore many of the science and engineering concepts central to the toys’ successful performance. Teacher-directed activities in science, mathematics, and technology education will cover the basic concepts and skills needed to understand the principles behind the prototypes and apply them when building the models. These lessons include demonstrations and hands-on experience examining fuel cell science, force and friction, energy transformation, simple machines, gears, motors, etc. In mathematics, students explore data collection and retrieval techniques by conducting controlled experiments. In addition, students apply their public speaking and writing skills as they prepare a workable proposal and presentation.

THE ENGINEERING DESIGN EXPERIENCEA unique characteristic of this program is its use of a problem-solving process favored by engineers in design teams and taught at many engineering schools across the country. The Engineering Design Experience (EDE) provides a problem-solving context in which students design a product or a solution to a problem. The students examine what must be accomplished; gather and synthesize information; predict a plausible solution; design, develop, and test a prototype or potential design, and prepare for a presentation of their design ideas.


Introduction


Introduction

iii

Engineering Design ExperienceThe EDE, as modified in this curriculum for middle school teachers and students, comprises six phases.

Set Goals. Students define goals through activities that stress sharing ideas and identifying and setting priorities. They define the problem, identify parameters for developing a solution, and establish objectives for successfully completing the job. Students also begin to develop a plan for the development process and related tasks, as well as to clarify roles within the team. They begin to develop an identity as a team by developing design team logos and slogans.

Build Knowledge. Students engage in a variety of inquiry-based activities involving direct experiences with the materials to help them develop an understanding of the underlying phenomena and mathematical concepts.

Design. Students synthesize the information they have acquired with the new skills and concepts they have learned to propose solutions to the challenge. They then develop sketches and prepare a design brief that describes their proposed product.

Build and Test. Based on their proposed design, students select appropriate materials for prototype development and performance testing, and develop drawings and diagrams to guide construction. Students develop a testing plan to determine the likelihood of successful performance and the appropriateness of the solution.

Finalize the Model. Students complete the building of their prototype, carry out performance tests, and then modify the prototype based on the results, providing evidence to support their changes.

Present. Students produce written documentation as evidence of their development process, such as a proposal and product specifications. The proposal incorporates testing data and reflects their understanding of the design process and design team capabilities.


Introduction

iv

THE CURRICULUM CONTENTThe EDE is an applied process that enables students to see how the field of engineering integrates knowledge and skills from science, mathematics, and technology. In addition, the design challenge provides a context in which students can apply content and concepts from previous learning experiences. The challenge, as embodied by the EDE, embraces the direction of national standards in science and mathematics education.

Indeed, the Challenge is one of the few curriculum programs to address specifically the National Research Council standards to educate students to develop products and solutions to problems through technological design. The Challenge also addresses the National Council of Teachers of Mathematics curriculum standards emphasizing that students should see mathematical connections to the real world through mathematical thinking, modeling, and problem solving.

In addition to addressing the larger, overarching learning outcomes regarding design technology and problem solving, the curriculum also addresses specific objectives in each of the related disciplines described below.

Science• Studentsbegintodevelopanunderstandingofforcesactingonmoving

objects by exploring the design of a moving toy.• Studentsbegintodevelopanunderstandingoffuelcells,their

operation, hydrogen production, and energy transformations.• Studentsextendtheirunderstandingofsimplemachinesthroughtheir

explorations of gears, axles, wheels and motors. • Studentsbegintodevelopanunderstandingofalternativefuelsand

energy sources, and their use in transportation.• Studentsbegintounderstandthedifferencesbetweenscienceand

technology by developing the ability to use technological design processes and skills.

Mathematics• Studentsextendtheirunderstandingofratesandratiosasarelationship

between numbers.• Studentssystematicallycollect,organize,anddescribedata,andmake

inferences based on data.• Studentsusephysicalmaterialstobuildconceptualdevelopmentof

algebraic variables and relationships.

In the middle-school years, students’ work with scientific investigations can be complemented by activities that are meant to meet a human need, solve a human problem, or develop a product . . .

From National Research Council

SCIENCE AND TECHNOLOGYContent Standard E: As a result of activities in grades 5-8, all students should develop • Abilities of technological design• Understanding about science and technology


Introduction

v

Technology Education• Studentsusedevelopmentandproductionprocessestosolvea

technological design problem.• Studentslearntocreatedesignbriefs,sketches,andmodels.• Studentsexplorepropertiesofmaterialsindesigningproducts.

In addition, the curriculum addresses the following specific content objectives in the Language Arts.

• Studentsdevelopwritingskillsthroughavarietyofwritingproductssuch as design logs, journals, and proposals.

• Studentsdeveloporallanguageskillsthroughthepreparationandexecution of formal presentations.

• Studentsdevelopcommunicationskillsthroughperformingcollaborative tasks with their peers.

STUDENTS WORKING IN TEAMSTeachers will need to decide how students will be placed in design teams and how to handle the logistics of providing materials and support for individual teams. For a program of this nature, heterogeneous groupings make for the best combination of individual skills and interests.

However, a considerable amount of research indicates that young women in the middle school benefit from studying in all-female groups. At that age, young men in the group, who may well have had more experience working with materials and thus feel more confident doing so, tend to dominate explorations with the materials and discussions of phenomena. Many of the young women may be working with fuel cells, motors, gears, axles, and wheels for the first time and may be inhibited when talking about their emerging understandings of the phenomena. It has also been observed that teachers of both gender tend to ask boys more questions in activities of this nature.

It has been our experience that mixed-gender groupings work fine when teachers are aware of these issues and actively work to improve the comfort level of their female students. Ultimately, it is the teachers who are best able to decide which students can work together in groups. The success of the program is also influenced by how well students have worked in groups in the past, and the chances of success are further increased if the students are already familiar with collaborative and cooperative learning strategies.

GUIDE TO THE CONTENT STANDARDFundamental abilities and concepts that underlie this standard include• Abilities of Technological Design.• Design a Solution or Product.• Implement a Proposed Design.• Evaluate Completed Technological Designs of Products.• Communicate the Process of Technological Design.

From National Research Council National Science

Education Standards


Introduction

vi

VOLUNTEERS IN THE CLASSROOMThis program is unique in encouraging the active participation of volunteers in the classroom. Volunteers can play a key role in helping design teams to implement the challenge during various phases of the EDE. Some volunteers may act as advisers throughout the three-week period. Others may assist in one or two activities by describing how their own work relates to the students’ design experience. Throughout the activities, suggestions for using volunteers are provided in Volunteer Tips.

Volunteers may be identified through collaborations formed with the local business and industry community, as well as through parents in the school community. For more information on the use of volunteers, see the appendix Contacting Volunteers.

THE ACTIVITY SEQUENCEThe following outline describes how the Fuel Cell Challenge, through the EDE, may unfold in the school, classroom, and community context. While the description outlines the various phases of the EDE process, classroom implementation is iterative as students take in new information, constantly evaluate and gauge their design decisions, and explore other options.

Week 1Set Goals. Students receive a request for proposals (RFP) from a fictitious toy company, Green Design Toys, to develop designs for motorized toys made with environmentally benign materials and powered by alternative power sources and fuels. Each student design team is invited to submit a proposal and prototype model that meets very specific performance specifications provided in the RFP. These criteria provide opportunities to explore concepts and factors important to mobility such as speed, force, friction, alternative fuel sources, and energy transformations. The RFP specifies design guidelines, dates of completion, and standards of performance.

Build Knowledge. The activities in this phase encourage students to learn basic concepts and skills related to the EDE challenge. The need to meet the Challenge or solve the problem serves both as a context and motivation for learning. These activities are aligned to specific performance and design needs for the prototype designs. During this phase, students explore materials and phenomena through trial and error, experimentation, and questioning. From this hands-on work they begin to develop an understanding of the variables, constraints, materials and phenomena that affect design and performance. They investigate the concepts underlying vehicle dynamics, the hydrogen fuel cell, energy transformations, and the chemistry of electrolysis.

TEACHER TIP Refer to the Contacting Volunteer section in the Appendix for additional information.

STANDARD 4: MATHEMATICAL CONNECTIONSIn grades 5–8, the mathematics curriculum should include the investigation of mathematical connections so that students—• apply mathematical thinking and modeling to solve problems that arise in other disciplines, such as art, music, psychology, science, and business;• explore problems and describe results using graphical, numerical, physical, algebraic, and verbal mathematical models or representations;

From National Council of Teachers of Mathematics, Curriculum and Evaluation

Standards for School Mathematics


Introduction

vii

Students may find that in addition to conceptual understanding, they also need new skills to complete a task. Students will be presented with the need to collect, organize, and represent data, and to analyze the results. These activities and information feed back to the students’ design and development.

Throughout the process, teachers have a range of opportunities for assessing student learning. In many cases assessment and learning are integrated, as students’ performance on many of the tasks provide insight into their understanding. Student design teams maintain portfolios of their work and their design logs. The design logs contain a collection of checklists, worksheets, and report forms to be completed.

Week 2Build Knowledge. Students continue to build their knowledge about hydrogen fuel cells, motors, green design, and alternative fuel sources. Through experiments they build an understanding of the relationships between energy, forces, and motion.

Design. Students synthesize their newly acquired information to propose potential solutions to the challenge. In this phase they begin to design their final prototype vehicle. After experimenting with fuel cells and different materials, students predict that certain configurations are more appropriate for meeting specific performance criteria.

The processes of gathering information and proposing solutions is followed by a process of designing a solution, and developing drawings and diagrams to guide construction of the prototype.

Week 3Build and Test. The fuel cell and motor are now integrated with the chassis, gears, axles and wheels. The drawings from the design phase provide guidance on the placement of the fuel cell, the motor, and the connection to the gears to drive the axles and wheels. As the prototypes are developed, students use testing techniques to examine performance. The goal is to optimize their vehicle’s design and performance.

Some of the students find their initial design is not appropriate and some discover that their original assumptions and understandings about fuel cells, motors and gears were incorrect. They may have to re-examine their designs and retest their prototype. Students can repeat this cycle as often as they need to, eventually making only minor adjustments as they become happier with the performance and design.


Introduction

viii

During this time, students take on a range of roles. Some design, others build; some create experiments, others conduct experiments; some record and organize the data, others analyze the data. Everyone is essential; all participate.

Finalize the Model. Students begin the process of modifying the prototype based on the results of performance tests. This phase includes building the final models, preparing the reports, and developing the graphics for the presentation. Each member of the team takes responsibility for some aspect of the final product.

Present. For the culminating activity, the design teams present written, visual, and oral reports documenting the design and development process, the performance test data, solutions, and their design team capabilities.

To prepare for the presentation, teams develop charts and graphs displaying their test results. They work on their written proposals, resumes, and other visuals. Some members of the design team may put their prototype through its final paces.

At the same time, the teachers and volunteers assemble the review committee for the final presentation. Representatives from business and industry partners, the principal, parents, and community representatives may be asked to review the design team presentations. Representatives from the local television station, newspaper, and corporate newsletter may be invited to chronicle the event.

WRITING AND DESIGN LOGSA World In Motion: The Design Experience encourages a fair amount of writing by students. Recording and keeping track of data and designs are crucial elements of the EDE. The design log becomes a tool for students to organize their design thinking and process systematically. Indeed, many engineers keep logs, journals, or sketches as evidence of their creative work should questions arise concerning copyright or intellectual ownership.

Writing also enables students to articulate and capture their emerging understanding of difficult concepts and phenomena. During the EDE, students should be encouraged to write in their design logs often. Each design team should have a three-ring binder as a design log. Student Reproducible Masters (SRM) may be copied, completed, and stored in the team design log. Individual student writings, such as journal entries, can be kept in special sections.


Introduction

ix

ABOUT FUEL CELLSThe design of the motorized toy as specified in the letter from Green Design Toys requires student teams to design and build a prototype powered with alternative power sources and fuel. This product line will use PEM (Proton Exchange Membrane) fuel cells to produce the electricity to power an electric motor that will drive the toy. The operation of the fuel cell, the electrolysis process, and the production of hydrogen are explored.

ABOUT MOTORSAn electric motor powered by the fuel cell will drive the motorized toy requested in the RFP from Green Design Toys. Students will explore operation of an electric motor and gearbox to meet the specifications provided in the RFP.

ABOUT ENERGY TRANSFORMATIONSStudents are introduced to energy transformations as they learn about fuel cells, motors, and gears. Students are exposed to the transformation of electrical energy to chemical energy during the electrolysis process as hydrogen is produced and stored. The energy is then transformed from chemical energy to electrical energy as the hydrogen is passed through the fuel cell to produce electricity for the motor. The motor then takes the electrical energy and converts it to mechanical energy to drive the toy.

ABOUT GREEN DESIGNThe RFP specifies that student teams design a motorized toy and build a prototype powered with alternative power sources and fuels and made from benign materials in such a way that the damage to the environment is minimized. Treating environmental concerns is part of the design experience and is commonly referred to as “Green Design.” Students investigate the use of the fuel cell as an alternative power source to power their vehicle. They study the effects that the materials they select for their product have on the environment.

ABOUT COLLECTING, ANALYZING, AND DISPLAYING DATAUsing and manipulating numbers as data are typical activities in middle school mathematics. At this age, students continue to develop a sense of how data are gathered, and grapple with making sense of the data collected. The design challenge provides students with a concrete opportunity for them to grapple with the use of numbers and information, use mathematical tools to process that information, and begin to interpret the information in ways that may be useful in developing their ultimate designs.

Lesson Plan Structure

Introduction

x

IntroductionThis section presents an overview introduction to the activity.

WHAT STUDENTS DO IN THIS ACTIVITYA description of what students will do in this activity.

RATIONALEA description of the reason(s) that students are performing the activity.

ObjectivesIn this section the educational objectives that the activity should address are identified.

TIMEThe time required for the activity is estimated.

MATERIALSThe materials required by the class, the design team, and/or the individual are listed in this section.

LINKSA list of computer links that can enhance the materials is given.

PREPARATION FOR THE ACTIVITYThis section identifies the preparation and actions that the teacher should accomplish in preparation for presenting the activity to the class.

Classroom ActivityThe following sub-sections describe some of the activities that take place in the classroom.

ACTIVITY DESCRIPTIONA brief description of the activity is presented. A typical data sheet may be included for some of the activities.

FACILITATING STUDENT EXPLORATIONA number of suggestions of ways that students may explore the material content is given.

SHARING AND INTERPRETINGThis section lists topics and ways that students may share the results to increase learning.

Lesson Plan Structure

Introduction

xi

TROUBLESHOOTING HINTSThis section lists hints on how to resolve problems that may occur during the activity.

Homework IdeasHomework ideas that students can present in the next class are listed.

GraphsA list of suggested data that should be graphed and the way the data can be interpreted is given. A typical graph of the data collected may be included for some of the activities.

NotesThis area is made available for teachers to record additional information.

Fuel Cell Design Challenge Activity Calendar

xii

Fuel Cell Design Challenge Activity Calendar

Week Monday Tuesday Wednesday Thursday Friday

One

1Reading and

Evaluating the Request for

Proposal

2Team

Formation andRecordkeeping

3Looking at Powered Vehicles

4What We

Know About Fuel Cells

5Chemistry of Electrolysis

Two

6Using the Fuel Cell

to Produce Power

7Powering an

Electric Motor and Gearbox

8Looking at

Green Design

9Writing the

Design Brief

Three

10Building and Testing the Prototype

11Assembling, Testing, and Adjusting the Final Design

12Present

Cor

rela

tion

to

Sta

ndar

ds

xiii

Ob

ject

ive

Ch

art

CM

Lo

va

s –

11

/15

/20

08

D

ow

nlo

ad

– 1

0/1

3/2

00

8

xv

AA

AS

Be

nc

hm

ark

s f

or

Sc

ien

ce

Lit

era

cy

– P

roje

ct

20

61

Fu

el C

ell

D

esig

n

C

hallen

ge

O

bje

cti

ves

Benchmark 1: Nature of Science A. Scientific Worldview

Benchmark 1: Nature of Science B. Scientific Inquiry

Benchmark 2: Nature of Mathematics B. Mathematics, Science, and

Technology

Benchmark 2: Nature of Mathematics C. Mathematical Inquiry

Benchmark 3: Nature of Technology A. Technology and Science

Benchmark 3: Nature of Technology B. Design and Systems

Benchmark 3: Nature of Technology C. Issues in Technology

Benchmark 4: The Physical Setting B. The Earth

Benchmark 4: The Physical Setting D. Structure of Matter

Benchmark 4: The Physical Setting E. Energy Transformations

Benchmark 4: The Physical Setting F. Motion

Benchmark 4: The Physical Setting G. Forces of Nature

Benchmark 8: The Designed World B. Materials and Manufacturing

Benchmark 8: The Designed World C. Energy Sources and Use

Benchmark 9: The Mathematical World A. Numbers

Benchmark 9: The Mathematical World B. Symbolic Relationships

Benchmark 9: The Mathematical World C. Shapes

Benchmark 9: The Mathematical World E. Reasoning

Benchmark 11: Common Themes A. Systems

Benchmark 11: Common Themes B. Models

Benchmark 12: Habits of the Mind A. Values and Attitudes

Benchmark 12: Habits of the Mind C. Manipulation and Observation

Benchmark 12: Habits of the Mind D. Communication Skills

Benchmark 12: Habits of the Mind E. Critical Response Skills

Th

e E

ng

ine

eri

ng

D

es

ign

Ex

pe

rie

nc

e

Use

th

e E

DE

as a

co

nte

xt

for

tea

ch

ing

an

d le

arn

ing

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Use

th

e E

DE

to

fu

lfill

a

sp

ecifie

d g

oa

l X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Sc

ien

ce

F

orm

ula

te a

pp

rop

ria

te

qu

estio

ns f

or

scie

ntific

inve

stig

atio

n

X

X

Co

nd

uct

scie

ntific

rese

arc

h u

sin

g a

pp

rop

ria

te

me

tho

ds

X

X

X

X

X

X

X

X

X

X

Inte

rpre

t scie

ntific

evid

en

ce

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Co

mm

un

ica

te t

he

re

su

lts

of

scie

ntific in

ve

stig

atio

n

X

X

X

X

X

X

Un

de

rsta

nd

diffe

ren

ce

b

etw

ee

n s

cie

nce

an

d

tech

no

log

y a

nd

use

of

de

sig

n p

roce

ss a

nd

skill

s

X

X

X

X

X

X

X

Un

de

rsta

nd

re

latio

nsh

ip

be

twe

en

fo

rce

s a

ctin

g o

n

an

ob

ject

an

d m

otio

n

X

X

X

X

X

X

X

X

Un

de

rsta

nd

fu

el ce

ll o

pe

ratio

n a

nd

hyd

rog

en

p

rod

uctio

n.

X

X

X

X

X

X

X

X

X

Un

de

rsta

nd

en

erg

y

tra

nsfo

rma

tio

ns.

X

X

X

X

X

Obje

ctiv

e C

hart

xiv

Cor

rela

tion

to

Sta

ndar

ds

Ob

ject

ive

Ch

art

CM

Lo

va

s –

11

/15

/20

08

D

ow

nlo

ad

– 1

0/1

3/2

00

8

xvi

Un

de

rsta

nd

alte

rna

tive

fu

els

an

d e

ne

rgy s

ou

rce

s,

an

d t

he

ir u

se

in

tr

an

sp

ort

atio

n

X

X

X

X

X

X

X

X

Un

de

rsta

nd

eff

ects

of

ch

an

gin

g a

sin

gle

va

ria

ble

a

nd

re

latio

nsh

ip o

f tw

o

va

ria

ble

s

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Ma

the

ma

tic

s

Syste

ma

tica

lly c

olle

ct,

org

an

ize

an

d d

escri

be

d

ata

X

X

X

X

X

X

X

X

Ma

ke

in

fere

nce

s b

ase

d o

n

da

ta

X

X

X

X

X

X

X

Exte

nd

un

de

rsta

nd

ing

of

rate

s a

nd

ra

tio

s a

s

rela

tio

nsh

ip b

etw

ee

n

nu

mb

ers

X

X

X

Use

co

ncre

te m

ate

ria

ls t

o

bu

ild c

on

ce

ptu

al

de

ve

lop

me

nt

of

alg

eb

raic

va

ria

ble

s a

nd

re

latio

nsh

ips

X

X

X

X

X

X

Te

ch

no

log

y

Ed

uc

ati

on

De

ve

lop

an

d u

se

p

rod

uctio

n p

roce

sse

s t

o

so

lve

a t

ech

no

log

ica

l

pro

ble

m

X

X

X

X

X

Cre

ate

de

sig

n

sp

ecific

atio

ns,

dra

win

gs,

an

d m

od

els

X

X

X

X

X

X

X

X

X

X

X

X

Te

st

an

d e

va

lua

te a

d

esig

n

X

X

X

X

X

X

X

X

X

Exp

lore

pro

pe

rtie

s o

f m

ate

ria

ls

X

X

X

X

X

X

Obje

ctiv

e C

hart

xv

Act

ivit

y C

har

t

CM

Lo

va

s –

11

/10

/20

08

D

ow

nlo

ad

-

10

/13

/20

08

x

vii

AA

AS

Be

nc

hm

ark

s f

or

Sc

ien

ce

Lit

era

cy

– P

roje

ct

20

61

Fu

el C

ell

D

esig

n

C

hallen

ge

A

cti

vit

ies

Benchmark 1: Nature of Science A. Scientific Worldview

Benchmark 1: Nature of Science B. Scientific Inquiry

Benchmark 2: Nature of Mathematics B. Mathematics, Science, and

Technology

Benchmark 2: Nature of Mathematics C. Mathematical Inquiry

Benchmark 3: Nature of Technology A. Technology and Science

Benchmark 3: Nature of Technology B. Design and Systems

Benchmark 3: Nature of Technology C. Issues in Technology

Benchmark 4: The Physical Setting B. The Earth

Benchmark 4: The Physical Setting D. Structure of Matter

Benchmark 4: The Physical Setting E. Energy Transformations

Benchmark 4: The Physical Setting F. Motion

Benchmark 4: The Physical Setting G. Forces of Nature

Benchmark 8: The Designed World B. Materials and Manufacturing

Benchmark 8: The Designed World C. Energy Sources and Use

Benchmark 9: The Mathematical World A. Numbers

Benchmark 9: The Mathematical World B. Symbolic Relationships

Benchmark 9: The Mathematical World C. Shapes

Benchmark 9: The Mathematical World E. Reasoning

Benchmark 11: Common Themes A. Systems

Benchmark 11: Common Themes B. Models

Benchmark 12: Habits of the Mind A. Values and Attitudes

Benchmark 12: Habits of the Mind C. Manipulation and Observation

Benchmark 12: Habits of the Mind D. Communication Skills

Benchmark 12: Habits of the Mind E. Critical Response Skills

Th

e E

ng

ine

eri

ng

D

es

ign

E

xp

eri

en

ce

Use

th

e E

DE

as a

co

nte

xt

for

tea

ch

ing

an

d

lea

rnin

g

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Use

th

e E

DE

to

fu

lfill

a

sp

ecifie

d g

oa

l X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Se

t G

oa

ls

Re

ad

ing

an

d E

va

lua

tin

g

the

Re

qu

est

for

Pro

po

sa

l (R

FP

)

X

X

X

X

X

X

X

X

X

X

Te

am

Fo

rma

tio

n a

nd

Re

co

rdke

ep

ing

X

X

Bu

ild

Kn

ow

led

ge

L

oo

kin

g a

t P

ow

ere

d

Ve

hic

les

X

X

X

X

X

X

X

Wh

at

We

Kn

ow

Ab

ou

t

Fu

el C

ells

X

X

X

X

X

X

X

X

Ch

em

istr

y o

f E

lectr

oly

sis

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Usin

g t

he

Fu

el C

ell

to

Pro

du

ce

Po

we

r X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Po

we

rin

g a

n E

lectr

ic

Mo

tor

an

d G

ea

rbo

x

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Lo

okin

g a

t G

ree

n

De

sig

n

X

X

X

X

X

X

X

X

De

sig

n

Wri

tin

g t

he

De

sig

n B

rie

f

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Cor

rela

tion

to

Sta

ndar

ds

Act

ivit

y C

hart

xvi

Cor

rela

tion

to

Sta

ndar

ds

Act

ivit

y C

hart

Act

ivit

y C

har

t

CM

Lo

va

s –

11

/10

/20

08

D

ow

nlo

ad

-

10

/13

/20

08

xvii

i

Bu

ild

an

d T

es

t

B

uild

an

d T

estin

g t

he

Pro

toty

pe

X

X

X

X

X

X

X

X

X

X

X

Fin

ali

ze

th

e M

od

el

Asse

mb

ling

, T

estin

g,

an

d A

dju

stin

g t

he

Fin

al

De

sig

n

X

X

X

X

X

X

X

X

X

X

Pre

se

nt

Th

e F

ina

l P

rese

nta

tio

ns

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Student Reproducible Master102

Request For Proposals

Toys of the Future

Using Technology of the Future

Dear Designers:

Mobility Toys, Inc. (MTI) is a leading developer and manufacturer of toy cars, airplanes, boats, pull-toys, and other moving toys. MTI is well known for its Traveler line of toys that includes the Skimmer, the Jet Toy Car, the Motorized Toy Car and the Glider.

OUR DESIGN NEEDSMobility Toys has formed a new division, Green Design Toys (GDT), to produce environmentally friendly toys. GDT is dedicated to developing toys made with environmentally benign materials and powered with alternative power sources and fuels other than batteries. We are especially interested in a toy made of materials that do minimum damage to the environment and are recyclable.

This new product line of toys will use PEM (Proton Exchange Membrane) fuel cells to produce the electricity for a motor that drives the toy. The first products that we are looking to develop will be motor-driven wheeled vehicles that are either speedy, can travel a long distance, or can move a load. The toy must be safe, creative, and made of materials that are recyclable or reusable.

THE WRITTEN PROPOSALInterested design teams should submit a written proposal to GDT. Each written proposal should include these items:

• adescriptionofyourtoydesign,• designdrawings,• anexplanationofwhyyouthinkthedesignisenvironmentallyfriendly,• resultsfromperformanceteststhatshowthatyourdesignteammeetsatleastoneoftheminimum

criteria given below, and • abriefdescriptionofhowaPEMworks

THE DESIGN PRESENTATION MEETINGOn _____________________ GDT will hold a design presentation meeting. At this meeting a review panel will listen to presentations from each design team. Each design team should prepare to give us a 10-minute presentation on your toy design. In your presentation, you must present results of performance tests that demonstrate that your toy meets these requirements. Each presentation should include these segments:

• Introducethedesignteammembersandtheirrolesinthedesignprocess• Describehowyoudevelopedyourdesign• Describethesciencebehindfuelcellsandthetransferofenergy

Green Design Toys


• Demonstratethatyourdesignmeetsatleastoneoftheminimumperformancestandardslistedbelow

• ArguestronglyforwhyGDTshoulduseyourteam’sdesign

THE MINIMUM PERFORMANCE STANDARDSGDT is only interested in toys that meet minimum performance standards. In your presentation, you must demonstrate that your toy can meet at least one of the following three performance standards. Your toy must be able to do one of the following when fueled by hydrogen gas produced by the fuel cell in 30 seconds;

• traveloveracourseof5metersfromastandingstartunderitsownpowerin8secondsorless• travelamaximumdistancefromastandingstartofatleast10meterswithoutaload• travelatleast5metersfromastandingstartwithaloadof300grams

Duringeachofthethreetests,thetoymustnotdeviatefromstraightlinetravelbymorethan50mmforeach 1 meter of travel. You must also provide an area on the chassis to carry the 300 gram load.

We emphasize that these are minimum requirements. We expect that successful designs will exceed at least one of these performance standards, depending on the type of toy you design. At a later date, fuel cells, motors, gears, axles, wheels, and chassis materials will be given to design teams in order to build your prototypes.

At GDT our slogan is, “Toys of the future using technology of the future.” Our products are designed to give customers what they want. We look forward to seeing your successful proposals showing how your designs live up to our slogan.

Sincerely,

Director of New Technology Green Design Toys Subsidiary of Mobility Toys, Inc

Name ______________________________ Date _______________________


Evaluating the RFP Log Sheet1.WhatdoesGDTwantfromeachdesignteam?Listtherequirementsforasuccessfulproposal.

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

2.Whatkindsoftoydesignsmightbesuccessful?

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

3.Whataretheminimumperformancestandards?

_______________________________________________________________________________

_______________________________________________________________________________

4.WhatadditionalquestionsdowehaveabouttheRFP?

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________


GDT Engineer Design LogCONFIDENTIAL

Name: Jan Martinez Date: 10/25/2006 Page: 112

Part Weight, g

Chassis 20Fuel Cell 100Motor 40Gear Box 40Total 200

This is the layout of the fuel cell, motor, and gear box on the chassis designthatItriedtodayfortheModelX5.Irecordedtheweightofall parts mounted on the chassis. My goal is to reduce the weight of the toy so that the toy will travel farther on the power generated by the fuel cell. The layout of the fuel cell, motor, and gear box demonstrates that the chassis can be narrower. By making the chassis narrower, the weight of the chassis will be decreased.

Chassis

Fuel

Cel

l

MotorGear Box


Design Log Page ________________

Name _____________________ Design Team _____________ Date ________

OBSERVATIONS AND DATA

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________




OBSERVATIONS AND DATA

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________


Desi

gn

Lo

g

P

age

____

____

____

____

Nam

e _

____

____

____

____

____

____

____

____

____

__D

esig

n Te

am _

____

____

____

____

____

____

____

_ D

ate

___

____

____

____

____

__


Page ________________


Automobile Components Sheet

1. Axle – The axle is a central shaft for a rotating wheel or gear. Axles are an important structural component of a vehicle. The axles maintain the position of the wheels or gears relative to each other, and to the vehicle body. Axles permit wheels and gears to rotate.

2. Chassis – The chassis forms the main structure of the vehicle. This structure supports the engine, the body, and gears, axles, and wheels.

3. Engine – The engine generates the power needed to move the vehicle by converting the energy in the fuel into power. The internal combustion engine (ICE) is a heat engine in which burning of a fuel occurs in a confined space called a combustion chamber.

4. Gasoline – Gasoline is a fuel made from petroleum, or crude oil, and is used to fuel many engines used in automobiles.

5.Gears–Gearsarecircularcomponentsthatbrieflyinterlock(ormesh)astheyturn.Agearactsasarotating lever to change the speed, force and/or direction of a power source.

6. Gearbox or Transmission – When several gears are put together, it is called a gear train. This gear train may also be called a gearbox. In an automobile it is called a transmission. The gearbox or transmission transmits power from the engine to the wheels.

7. Crude oil – Crude oil, like coal and natural gas, is the product of compression and heating of fossil materials that died millions of years ago under the earth’s surface. Oil is extracted from the ground through drilling and is sent to a processing plant to be made into gasoline, jet fuel, tar, plastics, and other materials. Oil may also be used as a lubricant to reduce friction.

8. Wheel – The wheel is a circular object that is mounted on, and rotates on, an axle. The wheel is a simple machine that acts as a rotating lever to transfer force from the vehicle to the ground, causing the vehicle to move.


Page ________________


Powering an Electric Motor and Gearbox Data Sheet Fuel Cell Type _____________ Fuel Cell Number _____________

Time of Hydrogen

Production, sec

Weight, gms

Distance, meters Time, sec Work,

joulesPower, watts


Page ________________


Identifying Automobile Components SheetSelect one of the automobile components(parts) from the list below and place the component next to the function the component performs.

Gears Gasoline Axles Chassis Transmission Internal combustion engine Crude oil Wheels

Function Automobile Component

1. source of fuel

2. fuel for engine

3. converts fuel into power

4. changes force and speed

5.transmitspowerfromenginetowheels

6. transfers force to ground

7. permits wheels and gears to rotate

8. supports components


Page ________________


Vehicle Forces Sheet

Free Body Diagram (FBD)

Weight – The weight of the vehicle is the force produced on the mass when the mass is acted on by gravity. Weight is a force equal to the mass of the object multiplied by the acceleration due to gravity.

Resisting Force – The resisting force is an equal and opposite force that balances the weight of the vehicle to be in equilibrium.

Friction – Friction is the force that occurs when two objects are in contact with each other. Kinetic friction occurs when one object rubs or slides against another object. Rolling friction occurs when one object rolls over another object.

Air resistance or drag – Air resistance or drag results from the friction of air flowing over the vehicle. The amount of drag depends on the shape, velocity, and “smoothness” of the vehicle. Drag increases as the vehicle speed increases.

Driving force – The driving force is provided by the engine and is applied by the wheels to the ground to move the vehicle. The driving force must overcome the friction and the drag forces. The larger the vehicle, the larger the driving force.


Page ________________


Identifying Vehicle Forces Sheet

Identify each of the numbered forces by name and place the name of the force and its effect on the vehicle next the appropriate number.

Force Effect on Vehicle Remedy

1.

2.

3.

4.

5.

kfrancis

Text Box

5

kfrancis

Text Box

3

kfrancis

Text Box

4

kfrancis

Text Box

1

kfrancis

Text Box

2


Page ________________


PEM Fuel Cell: Student Diagram

The parts of a PEM fuel cell are the anode catalyst (usually platinum), the membrane, and the cathode catalyst (usually platinum and iridium). Label the three parts with the words in the boxes.


Page ________________


PEM Fuel Cell: Team Diagram

The parts of a PEM fuel cell are the anode catalyst (usually platinum), the membrane, and the cathode catalyst (usually platinum and iridium). Label the three parts with the words in the boxes.

Describe how a fuel cell works.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

Fuel Cell Operation Directions

Appendices

117

FUEL CELL OPERATION AS AN ELECTROLYZERThe fuel cell has two sides that can be identified by a decal near the top nozzle and are also color-coded: red (positive) is the Oxygen side and black (negative) is the Hydrogen side. When using the fuel cell in the electrolyser mode the polarity is extremely important because the fuel cell can be ruined if a current is applied to the fuel cell incorrectly; always attach the red (positive) clip from the battery pack to the Oxygen side and the black (negative) clip to the Hydrogen side.

Before using the fuel cell some flexible tubing will need to be attached to the pressure relief valves and the syringes so that they may be attached to the nozzles on the fuel cell. A one inch long piece should be attached to each pressure relief valve, and a two inch long piece attached to one of the syringes, and a three inch long piece attached to the other syringe.

Step 1Hydrate the membrane of the fuel cell by adding distilled water to the Oxygen side of the fuel cell. Do this by drawing about 1ml of distilled water into a syringe and injecting it into the bottom nozzle of the Oxygen side of the fuel cell (some water will leak from the top nozzle). Never operate the fuel cell without insuring that there is water in the oxygen side of the fuel cell. Remove the syringe from the bottom nozzle and attach a pressure relief valve to this nozzle. Also attach a pressure relief valve to the lower nozzle on the Hydrogen side of the fuel cell.

118

Step 2Insert banana clips into both sides of the fuel cell (these will be the contacts for attaching leads to the fuel cell; remember – red is positive and black is negative; red is the oxygen side and black is the hydrogen side).

Step 3Attach a syringe to the top nozzle on each side of the fuel cell (these will be for gas storage).

Step 4Make sure that the battery pack is turned off! Attach the red and black leads from the battery pack to the banana clips extending from the fuel cell (do not allow the other ends of the leads to come in contact with each other – that would create a short circuit!); red lead on the oxygen (red) side and black lead on the hydrogen (black) side. After everyone on the team checks that the connections are correct, turn on the battery pack and the electrolysis begins. Turn off the battery pack when enough gases are collected and disconnect it from the fuel cell.


Appendices

119

FUEL CELL OPERATION AS A POWER SOURCEThe fuel cell has two sides that can be identified by a decal near the top nozzle and are also color-coded: red (positive) is the Oxygen side and black (negative) is the Hydrogen side. When using the fuel cell in the power source mode the polarity isn't as important; it will simply affect the direction of the motor.

Step 1Attach the red lead to the banana clip from the Oxygen (red) side of the fuel cell and attach the black lead to the banana clip from the Hydrogen (black) side; do not allow the other ends of the leads to come in contact with each other – that would create a short circuit!

Step 2Attach the other end of the red lead to the motor contact with the red dot; attach the other end of the black lead to the other contact on the motor.


Appendices


Page ________________


PEM Fuel Cell Data Sheet

Motor Run Time, secTime to Make Hydrogen, sec


Page ________________


Green Design Guidelines Sheet1. Be aware of the environmental effects of the materials used in products.Every step in the Green Design figure requires energy, produces waste products, and may deplete resources. It may not be realistic for the engineer to know the environmental details of every material used in a product. However, it is important to know about those materials that may have high environmental impact.

2. Design components that are reusable, recyclable, or renewable.A design goal is to use only recyclable materials. The makers of automobiles are striving for this goal. Therefore, it is important that the parts of the product are easily separated and each part is identified so that it will be easy to tell the difference between those parts that can be reused and those that can be recycled. Identification means to be able to tell after disassembly exactly what material was used in the manufacture of each component.

3. Be aware of the environmental effects of the material not reused or recycled.About 40% of solid waste in landfills is plastic and metal. All of this material could be reused, recycled, or renewed. If the product uses materials that can not be recycled or reused, it should be degradable. The designer should be aware of the amount of degradable material and the time it takes this material to degrade.


Page ________________


Evaluating Materials for Greenness Sheet

MaterialMaterial is

Reusable Recyclable Renewable Disposable

Bio-Degradable

Non-Degradable

Balsa Wood

Plastic

Steel

Aluminum

Rubber

Paper

Lead

Cardboard

Styrofoam

Aluminum Foil


Vehicle Assembly Procedure

Appendices

Vehicle Assembly ProcedureThe pre-drilled holes in the chassis provide many options for assembling the vehicle. The front axle will be attached though the single hole in the front of the vehicle and the gearbox will be attached through the two pre-drilled holes at the back of chassis. The other holes in the chassis are for attaching the fuel cell; there are ten different ways that it can be mounted.

Another element of assembly that can be altered is the gas storage. In the initial experiments the syringes are used to store the gases so that certain quantities can be identified and related to performance. Another way to store gases is in the tubing itself, using the clamps provided to close off one end of the tube. An advantage of using the tubing is the reduction in mass of the assembled vehicles.


Vehicle Assembly Procedure

Appendices

Step 1Using the two longer bolts and washers and nuts from the kit, attach the gearbox through the two holes at the rear of the chassis; check to see that the gears are visible through the slit in the chassis. Tighten with the screwdriver. Press the wheels onto the axle with enough force to engage the spline; they do not need to completely cover the spline.

Step 2Attach the front axle brace to the chassis using a small bolt, lock washer, washer and nut; use the screwdriver and wrench to tighten. The brace may be attached on the top or bottom of the chassis. Slide the axlethrough the brace, install a spacer on eachside, and press wheels onto this axle with enough force to engage the spline; they do not need to completely cover the spline.

Step 3Attach the fuel cell to the brace using the two larger nuts from the kit; tighten with the wrench. Attach the fuel cell and brace to the chassis using two small bolts, washers and nuts; tighten with the screwdriver and wrench. The fuel cell can be mounted ten different ways depending on how you would like to configure your vehicle.


Page ________________


Prototype Test Data SheetPrototype Weight _____________

Fuel Cell Type _____________ Fuel Cell Number _____________

Time of Hydrogen Production, sec

Time Vehicle Traveled, sec Observations

10

20

30

40

50

60

70


Page ________________


Speed Test Data SheetPrototype Weight _____________ Distance 5 m

Trial Number

Timesec

Deviation from Straight at 5 m

In mm

Deviation less than 250 mm ObservationsYes No

1

2

3

4

5

6

7


Page ________________


Endurance Test Data SheetPrototype Weight _____________ Distance _____________

Trial Number

Distancem

Deviation from

Straight at 10 m,In mm

Time to travel 10 m, in sec

Deviation less than 500 mm Observations

Yes No

1

2

3

4

5

6

7


Page ________________


Load Test Data SheetPrototype Weight _____________ Distance _____________

Trial Number

Distancem

Deviation from

Straight at 5 m,

In mm

Time to travel 5 m,

in sec

Deviation less than 250 mm Observations

Yes No

1

2

3

4

5

6

7

Safety and Precautions

Appendices

129

Remember, you the Teacher are responsible for what happens in your classroom. The SAE Foundation does not have liability for any injuries or damage that may occur from the use of this equipment or the performance of these experiments. Review the equipment, experiments, and procedures to make sure you are comfortable with that responsibility.

Read directions carefully before beginning the experimentation. Follow instructions and have them available for reference.

GeneralAll persons

• involvedinthesetup,operationormaintenanceofthefuelcellmustread and follow the operating instructions.

• presentduringexperimentsmustweargoggles.• involvedinthesetup,operationormaintenanceofthefuelcellmustbe

trained in the operation of the fuel cell.

Sources of Danger• Removeanythingfromthevicinityofthefuelcellthatcouldignitethe

gases produced by the fuel cell (flame, materials that can be charged with static electricity, substances with a catalytic action).

• Removeinflammablegases,vapors,andliquidsfromthevicinityofthefuel cell.

Emergency Shut-DownIf leaking hydrogen ignites

• Immediatelyremovethecurrentsupplycablefromthefuelcelltostophydrogen production.

• Initiateallnecessaryfire-fightingmeasures.• Immediatelyensurethateveryonekeepsasafedistanceofatleast10m

from the apparatus.• Afterawaitingperiodofatleast10minutes,approachtheapparatus

with suitable protective goggles, and close down the operation of the apparatus.

Safety and Precautions

Appendices

130

Fuel Cell• Thefuelcellmustbeoperatedinawellventilatedroom.• Thefuelcellmustbefilledwithdistilledwateronly.Useofanyliquids

(e.g., those containing electrolytes) like tap water will destroy the fuel cell.

• Thehydrogenandoxygenreactingtogetherinthefuelcellrepresentsources of danger if handled improperly.

• Donotoperatethefuelcellempty.Alwaysmakesurethefuelcellcontains sufficient water during operation.

• Operatethefuelcellonlyatroomtemperatureandambientpressure.• Donotmakeanymodificationstothefuelcell.• Onlyusethegasstorageunitsbelongingtoorsuppliedwiththesystem

to store gas.

Electrical• Shortedbatteriescangetveryhot,whichwillresultinburnsandother

hazards.• Donotdisposeofbatteriesinafireastheymayexplode.• Theelectrolyteinbatteriesiscorrosiveandcancausedamagetotheeyes

and skin.

Mechanical• Thesmallcomponentsandsharppointedwirespresentahazardand

can cause injury if handled improperly.• Thegearboxcontainssmallpartsthatmaybehazardoustosmall

children.• Keepfingersfrommovingparts.

Finding a Classroom Volunteer

131

My Requirements as a TeacherClassroom InstructionAWIM is a teacher-led activity with volunteer support. Meet or talk with the volunteer to go over the curriculum and expectations. The teacher maintains all regular responsibilities such as classroom management, student discipline, photocopying, and assessing student understanding. The volunteer is in the classroom to share his or her expertise and work experience.

Monitoring VolunteersAll AWIM volunteers must follow regulations for school visitors set by the individual school or district. Please be sure to inform your classroom volunteer about your school’s procedures, which may include, but are not limited to: background checks, � ngerprinting, signing in & out, and participation in safety drills.

Flexibility of VisitsThe number of times the volunteer visits your class varies based on the school schedule, the volunteer’s schedule, and how in-depth you wish the lessons to be. Schedule visits in advance. Check with the volunteer a day or two ahead of each planned visit to con� rm arrangements. Be � exible. Volunteers are taking time away from their job or adjusting their hours to assist in the program. Your volunteer’s schedule may change and a visit may be canceled or postponed. Be sure to have a backup plan incase a volunteer needs to reschedule.

Volunteer UpdatesDetermine the best means of communication between you and the volunteer. If you rely on phone calls, be sure to exchange school and/or home numbers and best times to call. If you plan to communicate by email, let each other know how often you check your mail. Communicating with your volunteer about lessons prior to and after classroom visits will bene� t both of you. If e-mail communication is possible, it is helpful to share lesson plans, handouts, articles, or other documents that will be used during class. Providing your volunteer with student feedback can be helpful and rewarding. If students are confused about a concept covered during class, let the volunteer know. The more your volunteer knows about where your students stand in their understanding of the material, the better able he or she will be to tailor each visit to your students’ needs. Keep in mind that re-entering the classroom can be intimidating for some volunteers. Any positive feedback that you share can help ease this apprehension.

132

133133

Looking for Volunteer Support

Who to Ask ForWhen calling a local company consider asking for a representative in Human Resources, Communication or Community Relations as an initial “point of entry.” Many companies like to get involved in their community and managers in these functional areas either work on those aspects or can connect you to the correct person. A World in Motion is an excellent bridge to link education and industry. Schools show that they are teaching their students relevant technologies, while companies show that they are involved in supporting their local community.

SAE International SupportResources at SAE International may be able to help you in your search for Industry Volunteers. Visit www.awim.org to � nd some other helpful hints.

Contacting Volunteers – Ways to Reach OutAWIM provides the curriculum and materials to teach the concepts of physical science to elementary, middle and high school students. It is important to remember these concepts form the basic principles of science that we all learned when we were in school. The potential pool of volunteers is much larger that you might � rst realize.

Potential volunteers may include members of your PTA, parents or grandparents, even current school volunteers. Consider calling a local chapter of a professional organization as a lead for volunteers. Potential volunteers may include university students studying education, mathematics, science or engineering.

Types of Companies to ContactThe AWIM curriculum is designed to provide students with an Engineering Design Experience by designing a vehicle. So it is natural to think of engineers as potential volunteers.

The engineering profession has many specialized � elds including:

Aeronautical Agricultural Automotive Biomedical Ceramic Chemical Civil Computer Science Electrical Engineering Physics Environmental

Health & Sanitary Geological Marine Mechanical Metallurgical & Materials Mining Nuclear Oceanic Petroleum Systems Textile Transportation

LaboratoriesIndustrial Plants Construction Sites HospitalsService Garages

When looking for a volunteer, don’t limit yourself to engineers. Remember the AWIM concepts are the basis for all technology � elds. Industrial volunteers may include scientists and other professionals that use technology. Keep in mind the goals of having a volunteer in the classroom: building awareness of engineering and other technical professions, and to support the teacher in the classroom.

Consider these locations when looking for a volunteer:

AirportsThe Department of TransportationCity Municipal Of� cesOutdoors

133

Time Commitment – Suggested VisitsA World in Motion offers volunteers � exibility in scheduling classroom visitations. Visitations are typically one hour (on site classroom time). Over the course of the program volunteers can commit anywhere from one to six hours to dedicated classroom visitation. Many volunteers choose to commit more time and resources. Because of the unique concept of volunteers leaving work to visit the classroom there is no visitation schedule outlined in this guide. Time commitment and schedules need to be topics of discussion between the Industry Volunteer and teacher.

During a Volunteer VisitDuring a classroom visit the follow roles and responsibilities may apply:

Teacher

• Responsible for Classroom Management and must remain present in classroom during all volunteer visits

• Communicate openly with volunteer(s)

• Implement the AWIM program with your Industry Volunteer partner(s):

• Work with student teams in advance of each classroom visit to ensure each team is prepared

• Ensure implementation of all volunteer and non-volunteer sessions

• Evaluate student learning

• Recognize student participation

Volunteer

• Be familiar with school safety/security protocol:

• Parking

• Entry/exit & check-in procedures

• Evacuation/take shelter procedures and mustering areas

• Work with your teacher partner to:

• Review program content

• Identify available presentation resources

• Maintain cadence established by the schedule

• Be prepared for each visit

• Attend all scheduled sessions, notifying teacher/volunteer team in advance of absence

• Serve as a role model and provide relevant ‘real world’ examples to students

• Coach students by asking questions to guide them toward solutions

• Make learning fun for the students!

Asking Permission from Management (Volunteers)

Many volunteers need to request permission from their supervisor to leave work to volunteer for AWIM in the classroom. Provide your volunteer with information on the AWIM program. Explain that an important element of the program is having a volunteer who can relate the AWIM concepts to the business world. Volunteers provide an important aspect to the class by explaining how science, technology, engineering & math are used every day in industry.

It is also helpful to have a tentative schedule for the AWIM volunteer sessions that the volunteer can provide to his or her supervisor. In most cases the volunteer will spend 1- hour in the classroom each week for up to six weeks. Be sure to consider the time required traveling to the school and any meetings scheduled with the teacher prior to the program beginning.

A � rst time volunteer may also need to schedule time to prepare for the classroom session by reading the lesson plan or science notes. This work can be done outside of the work day.

The AWIM program is an excellent opportunity to build community relations. The teacher and volunteer may consider contacting a local newspaper to participate in the � nal presentations at the conclusion of the AWIM program.

134

Volunteer Requirements

Volunteer Recruitment ToolsProgram Introduction LetterAPPENDIX A provides a sample letter that can be used to solicit potential Industry Volunteers.

AWIM BrochureAPPENDIX B provides a two-page brochure that can be used to share a basic program overview with potential Industry Volunteers.

The Script (Talking Points)APPENDIX C provides a talking script to be used to guide a one-on-one conversation with a potential volunteer.

135

136

(Engineer, Community Member, Industry Volunteer)

(Grandview Elementary School) needs your help! I am starting an exciting new program

that introduces students to engineering design using an approach known as the

Engineering Design Experience. Students live the Engineering Design Experience as

they are presented a real life problem from a fi ctitious toy company. Once the students

receive the challenge, they need to develop a series of steps to solve the problem.

This is where your help is needed. I would love for you to volunteer a small amount of

time to come to my classroom and discuss your everyday experience with the students.

Your fi rst hand knowledge of (engineering and/or your specifi c technical fi eld) would

really lend itself to the students’ experience. If you are interested please contact me using one of means below and I can share more

information about our partnership in educating our students in science, technology,

engineering and mathematics. Respectfully,(Ms. Smith – 5th grade teacher Grandview Elementary)

([email protected])(724-555-1234)

Appendix A

Fun, Fantastic & FREE!

Expand your curriculum and bring math and science to life for your students through this Standards-based, highly interactive, fun program – and at no cost to you. Through volunteer engineers and scientists, A World In Motion® (AWIM) will open a window of possibilities for your students as they discover the exciting application of science principles right in the classroom.

The AWIM curriculum joins together teachers, students and, volunteer engineers and scientists to engage students in grades 4-10. AWIM blends math and science while incorporating the laws of physics, motion, fl ight and electronics into age-appropriate Challenges. Each Challenge is designed to reinforce classroom STEM curriculum.

When you participate in the AWIM program, you are helping to prepare students for the challenges of tomorrow through personal discovery. As the teacher who provides information about exciting, science-related careers - you are playing an important role in the development of future engineers and scientists.

Find out how AWIM can enhance your curriculum and sow the seeds of endless possibilities for a future generation. Who knows…one of your students could become the next great innovator!

You Can Influence Future GenerationsA World In Motion is a wonderful opportunity for engineers, scientists and corporations alike to help students discover the exciting world of science, and how it applies to real life. You can play an important role in encouraging students to consider science-related and technical careers and help develop future generations. Your support of AWIM programs could open a window of opportunity for children throughout your community.

To learn more about becoming a volunteer, sponsoring a school, or making a donation, visit www.awim. org, email [email protected], or call 1-800-457-2946.

Helping teachers bring math and science to life –right in the classroom using Standards-based,STEM curriculum

www.awim.org• Teach • Volunteer • Donate

137

Appendix B

A World In Motion Challenges:A Motionn CChhChC aalllleennggeess::Elementary ActivitiesSkimmer Students construct paper sailboats and test the effect of different sail shapes, sizes, and construction methods to meet specifi c performance criteria. Friction, forces, the effect of surface area and design are some of the physical phenomena students encounter in this challenge.

JetToyStudents make balloon-powered toy cars that meet specifi c performance criteria; travels far, carries weight, or goes fast. Jet propulsion, friction, air resistance and design are the core scientifi c concepts students explore in this challenge.

Electricity & ElectronicsThe Electricity & Electronics - Elementary challenge provides teachers with activities that focus on principles of electronics by providing hands-on experiments involving static electricity, batteries and capacitors.

High School Electricity & Electronics The Electricity & Electronics – High School activities guide student teams through in-depth experiments involving transistors & semiconductors, analog integrated circuits, and digital integrated circuits.

Middle School ActivitiesMotorized Toy Car Students develop new designs for electric gear driven toys. The students are involved in writing proposals, drawing sketches, and working with models to develop a plan to meet a specifi c set of design requirements. Force and friction, simple machines, levers and gears, torque and design are the core scientifi c concepts covered in this challenge.

GliderStudents explore the relationship between force and motion and the effects of weight and lift on a glider. Students learn the relationships between data analysis and variable manipulations, and the importance of understanding consumer demands. The glider activity culminates in a book-signing event where each design team presents its prototype and the class presents its manuscripts to Mobility Press “representatives” and members of the local community.

Electricity & Electronics The Electricity & Electronics – Middle School activities provide teachers with activities that guide student teams through experiments involving series & parallel circuits, magnetism and an introduction to electronics.

P80322

www.awim.org• Teach • Volunteer • Donate

CURRENTLY UNDER REVISION

CURRENTLY UNDER REVISION

138

Appendix B

Appendix CThe Script (Talking Points)Below are some talking points that may help you start your conversation with the company representative or potential volunteer. Once you contact the correct person; introduce yourself, explain why you are calling, what you are looking for, and how they can get involved.

Introduce yourself.Why:

I am introducing my students to a dynamic curriculum focused on the engineering design process. The program is designed to help students see how math and science connect to the real world.

An important aspect of this program is fostering positive attitudes toward science, technology, engineering & math. There is no better way to do this than by exposing the students to people who have a passion and make a living working with technology.

What:

What is AWIM?

AWIM is a unique program that steps students through the Engineering Design Experience, used by engineers in design teams. This method provides a problem-solving context in which

student design a product or devise a solution to a problem. Teams of three students examine what must be accomplished and who the product is for; gather and synthesize information; design, develop, and test a prototype design; and prepare a presentation of their ides.

Through the Engineering Design Experience students identify problems, generate and evaluate ideas, plan and implement solutions, evaluate solutions, and communicate results – just as professionals do in industry.

I am calling because your company is rich in technology and I am hoping you might consider a partnership with me by volunteering or encouraging your employees to volunteer in my classroom.

How:

The curriculum actually walks the students through the engineering design experience with a hands-on project that is completed by a team of students.

Volunteers in the classroom will support classroom activities and share their professional experiences with the students.

Each class session lasts about 1-hour. Volunteers can participate in as little as one session or participate in all classroom sessions, depending on their availability.

Explain if volunteer training is available (either through SAE orone-on-one with you).

Explain if the classroom schedule is fl exible and if you are able to accommodate the

volunteer’s availability

Closing:

Are you available to meet to discuss the program in more detail?

Consider bringing an example of one of the completed challenge vehicles. If time permits, build one during the meeting. If possible, bring extra materials that can be given to the volunteers. In addition, bring a copy of the challenge description, a description of the roles & responsibilities and a tentative timeline.

P82102

139

Reflecting on the Engineering Design Experience

Appendices

140

A project-based unit is usually made up of various parts. Students often don’t realize how much they needed to do to complete a project, because they are so focused on a final product. Students need to assess their experience by reflecting on the process, not just the product. Assessment provides students with the opportunity to reflect on the work they did in each of the phases of the engineering design experience. It is an opportunity to discuss what the engineering design experience is.

Discuss the engineering process, including the characteristics of each phase. Remind students of the different phases and activities.

• Whathaveyoulearnedabouthowengineersdesignproducts?• Whatarethephasesengineersgothroughwhendesigningaproduct?• Whatisuniqueorimportantabouteachphase?• Whatdoyoulikebestabouteachphase?Whatdoyoulikeleast?• Whataresomeofthethingsengineershavetoconsiderwhendesigning

aproduct?• Whatskillshaveyoulearnedthatareimportantforengineerstohave?• Whatskillswouldyouliketoimprove?

Discuss with the class the interdisciplinary nature of the work they did in the unit.

• Whataresomeofthewaysengineeringdrawsonmath,scienceandlanguagearts?

• Howweremathandsciencerelatedinthedesignexperience?• Howdidwritinghelpsolveproblems?

Students can discuss the dynamics of their design teams.• Howwelldidyourdesignteamworktogether?• Didithelpyoutorelyoneachothertocompleteallthetasks?

Students should discuss how they might proceed to solve the challenge differently if they were to do it again.

TEACHER TIP Have all student team members present to reflect on the experience.

VOLUNTEER TIP Ask an engineer or design volunteer to attend the class for this final discussion. Students can ask the volunteer about how the engineering design experience they have had in the unit compares with the engineer’s design experiences.

Forces and Newton’s Laws of Motion

Appendices

141

Students will investigate forces and the effect of those forces on vehicle movement as they progress through the activities during the 3-week design Challenge. The design of the vehicle must provide sufficient power to overcome these forces to achieve their goals.

Free Body Diagram. The free body diagram is a tool for visualizing and understanding the forces acting on an object. An object is “freed” from surrounding attachments and all forces are placed on the object. These forces must be balanced if an object is to remain at rest. If there is an unbalance in forces then the object will “accelerate” or move. The free body diagram provides a visual “picture” of the forces acting on an object, and provides a platform for discussion on Newton’s Laws of Motion.

Forces. The first step in evaluation of forces and the effect of forces on an object is the identification of the forces acting in a given situation. Forces acting on a vehicle similar to the toy to be designed by students in this activity are

Weight – The weight of the vehicle is the force produced on the mass when gravity acts on that mass. Weight is a force equal to the mass of the object multiplied by the acceleration due to gravity.

Weight = mass x g

Resisting Force – The resisting force is an equal and opposite force that balances the weight of the object when the object is in equilibrium.

Friction – Friction is the force that occurs when two objects are in contact with each other, and the objects slide or roll relative to each other. Kinetic friction occurs when one object rubs or slides against another object. Rolling friction occurs when one object rolls over another object.

Air resistance or drag – Air resistance or drag results from the friction of air flowing over the object. The amount of drag depends on the shape, velocity, and “smoothness” of the object. Drag increases as the speed of the object increases.

Driving force – In a moving vehicle, the driving force is provided by the engine. This force is applied through the wheels to the ground to move the vehicle. The driving force must overcome the friction and the drag forces. The more the vehicle weighs, the larger the driving force must be to move the vehicle at the same speed.

Forces and Newton’s Laws of Motion

Appendices

142

Newton’s Laws of Motion. These three laws of physics relate mass, force, and acceleration of an object. Students will use Newton’s Laws of Motion to help them in selecting elements of their toy during the design process. They will also apply Newton’s Laws to help them in predicting the performance of their newly designed toy.

First Law: An object in motion stays in motion and an object at rest stays at rest unless a force causes a change.

Second Law: Relates the force needed to accelerate a mass.F = ma

where F is the force acting on an object, m is the mass of the object, and a is acceleration of the object due to the force acting

on the object If the acceleration on an object is due to gravity we substitute a “g” for

the “a” in the equation to get

F = mg = Weight

where g is the gravitational acceleration

When the acceleration is due to gravity the force (F) now becomes the weight (W) of the object.

Third Law: For every action there is an equal and opposite reaction.

Electrolysis

Appendices

143

Electrolysis is an area of chemistry concerned with the direct conversion of chemical energy into electrical energy. Electrolysis is a chemical reaction that takes place when an electric current is applied to a liquid or gas. Water is one of those liquids whose properties can be changed with the application of an electrical current.

Water is a chemical compound composed of two atoms of hydrogen chemically bonded to one atom of hydrogen (H2O). During the electrolysis process water molecules are decomposed to diatomic molecules of hydrogen gas (H2) and oxygen gas (O2). The reaction is endothermic requiring energy to create the final products.

2 (H2O) 2 (H2) + O2

A PEM (proton exchange membrane) fuel cell can facilitate the decomposition process of water. The reversible PEM fuel cell operates in 2 modes: the electrolyzer mode and the fuel cell mode. When operating in the electrolyzer mode the PEM fuel cell will convert electrical energy into chemical energy. Operating the PEM fuel cell in the fuel cell mode will convert chemical energy into electrical energy.

In the electrolyzer mode water is injected into the fuel cell and electrical energy from a power source is applied to the PEM fuel cell. At the positively charged side of the cell, electrons are stripped away from the hydrogen atoms and hydrogen gas molecules are produced. At the negative terminal, oxygen molecules are produced.

The hydrogen ions produced by the chemical decomposition of water instantly begin to share electrons with other hydrogen ions, thereby creating diatomic hydrogen molecules. This result is the production of diatomic molecules of hydrogen atoms (hydrogen gas).

Two Molecules Two diatomic molecules of hydrogen gas

One diatomic molecule of oxygen gas

decompose +

+

Electrolysis

Appendices

144

The electrical energy required to initiate this chemical reaction is transferred into the water molecules creating a hydrogen gas fuel source. It is this fuel currency (hydrogen gas) that can now be used in fuel cells to make electricity, stored and used later, or transferred to any other location for consumption. As a fuel currency, the hydrogen gas has been created from the transfer of electrical energy into chemical energy.

Energy, Work, and Power

Appendices

145

Machines have been used for thousands of years to improve the life of individuals. Machines do work and produce forces. Machines do not produce energy, but machines can transform and transmit energy.

Energy. Energy is the ability to do work and all matter has some energy. Energy comes in many forms, including mechanical, heat, electrical, chemical, solar, and nuclear energy. All energy can be transformed from one type of energy into a second type of energy. The law of conservation of energy states that the total energy is conserved during these transfers.

Energy Transfers. These energy transfers can take place in many different ways. Some typical energy transfers are listed below, with the energy transfers used in the curriculum highlighted in bold:

• mechanicalenergytoheatenergy• electricalenergytochemicalenergy• chemicalenergytoelectricalenergy• electricalenergytomechanicalenergy• solarradiationtoheatenergy• solarradiationtochemicalenergy• solarradiationtoelectricalenergy

Work. Work is one way of transferring energy. Mechanical work means the application of a force over a distance. The force must be in the same direction as the motion. Again machines do work and produce forces.

Work can be determined by the following relationship:

Work (joules) = Force (newtons) x Distance (meters)

In this challenge the PEM fuel cell provides an electric motor with electric power to do work. The motor winds up a string with an attached weight off the ground to a certain height. The pulley is doing work on the weight equal to

Work produced = Weight (newtons) x distance by the motor (joules) traveled (meters)

Energy, Work, and Power

Appendices

146

Power. Work measures what is done while power tells how fast that work was accomplished. Power can be determined from the relationship:

Power (watts) = Work (joules) / Time (sec.)

In this challenge the motor lifts the weight off the ground to a height in a given time period. The longer it takes to lift the weight through the distance the less power is generated by the motor. More power is generated when the weight is lifted in a shorter time.

Looking At Gears

Appendices

147

Remind students that the RFP from GDT requests motor-driven vehicles that are either speedy, can move a load, or travel a long distance. Students need to understand how gears can be used to increase speed or increase torque to meet one, or more, of these requirements.

The speed of an object and the torque used to move the object depends on 1) the torque and speed of the motor and 2) the train of gears between the motor and the wheels of the object. Since a motor produces only one speed and one torque, the gear ratio for the train of gears between the motor and the wheels determines the speed and torque at the wheel axle.

What Are Gears and How Are they Used? Gears are circular components that briefly mesh as they turn. The motor drives the first gear that meshes with a second gear that drives the wheels. The ratio of the diameters of the two gears determines how fast the second gear turns.

Many machines that use gears have gears that are not visible as the machine operates. The automobile has a transmission that uses gears to transmit power from the engine to the axles and wheels. These gears cannot be seen without “cutting away” the housing of the transmission.

TEACHER TIP At this point, if most students have access to bicycles at home, you may want to assign the questions about bicycle gears as homework.

Looking At Gears

Appendices

148

What Do We Know About Gears? An easy way to understand gears and how they operate is to explore a machine where the gears are visible. One machine that uses gears that are visible is a bicycle. Arrange for a derailleur bicycle to be brought to the classroom to aid in discussions.

Ask students• Howmanyofyourideabicyclethatallowsyoutochangegears?• Howdoyouusethegearswhenridingabicycle?• Whatdogearsdoonabicycle?

Some students may say that they use some gear combinations to go fast and other gear combinations to climb hills. You can then ask if any students have investigated which gear combinations they use to go fast, or to climb hills.

Ask students: What sprocket combination would you use to go as fast as possible?Whyisthissprocketcombinationbestforgoingasfastaspossible?

The combination that turns the rear wheel the fastest is the largest pedal sprocket and the smallest wheel sprocket.

Askstudents:Whatsprocketcombinationwouldyouusetogoupasteephill?Whyisthissprocketcombinationbestforgoingupasteephill?

The best combination for climbing a steep hill is the smallest pedal sprocket and the largest wheel sprocket.

Askstudents:Whatdothegearsdo? Gears allow the rider to change the number of times the rear wheel rotates

for each pedal rotation. This affects the distance the bicycle travels with each pedal rotation. Gears also allow the rider to change the force with which the rear wheel turns. This allows the rider to get more turning force to go up a hill or start from a standstill. These two characteristics are related. The more times the rear wheel turns relative to the pedal, the less turning force it has. The fewer times the rear wheel turns relative to the pedal, the more turning force it has.

Askstudents:HowdoestheanswerfromthelastquestionrelatetotheRFP? The first performance standard requires that the vehicle goes fast. The third

performance standard requires that the vehicle move a large weight.

Looking At Gears

Appendices

149

Gear Ratio and Speed. The relationship between the rotations of the two gears in a pair of gears is constant. It does not depend on how many times the gears rotate, or on how fast they rotate. We use the word ratio to describe this constant relationship between two values. A gear ratio is the ratio of the number of rotations of a driver gear to the number of rotations of a driven gear.

gear ratio = rotations of a driver gear / rotations of a driven gear.

Driver Driven Gear Gear

Foreveryrotationofthe45-toothgear,the15-toothgearmustrotate3times.Thisistruenomatterhowmanytimesthe45-toothgearrotates.Theratiobetweentherotationsofthe15-toothdrivergearandthe45-toothdrivengearis 3 to 1. That is, the gear ratio is 3 to 1. A colon is often used to show a gear ratio. Using the colon notation, the gear ratio is 3:1. A gear ratio is always given as the ratio of the rotations of the driver gear to the rotations of the driven gear.

Note that the gear ratio can also be expressed as

Gear ratio = number of teeth on driven gear / number of teeth on driver gear

Using this equation with the number of teeth, then

Gearratio=45/15=3/1=3:1.

MAKING CONNECTIONS This activity should be done after the What Do We Know About Gears?

TEACHER TIP For a more thorough coverage of gears, see the AWIM challenge on the motorized toy car.

Looking At Gears

Appendices

150

The “best” form of the equation will depend on the information that is easiest for us to find. In many cases it is easier to find the number of teeth on the gears, by counting the number of teeth.

The smaller number of teeth on the driven gear for the same driver gear will result in a larger speed. The larger number of teeth on the driven gear for the same driver gear will result in a slower speed.

SCIENCE MATHEMATICSGear Ratio and Torque. Torque is the tendency of a force to cause rotation. Torque is expressed as the product of the force and a lever arm.

Torque = Force multiplied by Distance

T = F x D

A driver gear transmits a force between its tooth and the mating tooth on the driven gear. This force depends on the torque supplied by the motor and the radius of the gear. Force is the torque divided by the radius.

Force = Torque / Radius of the gear = T / R

A good demonstration of torque is the tightening of a bolt with a wrench. When the same force is applied to two wrenches, the longer wrench will supply a larger torque to tighten the bolt because the longer wrench has a larger radius.

(Make Driven Gear 2 (and T2) larger.)

A driven gear transmits a torque to its axle, which depends on the force applied to its teeth and the radius of the driven gear.

MAKING CONNECTIONS This activity should be done after Gear Ratio and Speed. The teacher will find the information from these activities useful when working on the relationship between force, lever arm, and torque.

Looking At Gears

Appendices

151

Torque = Force multiplied by Radius of the gearA is the radius of the driver gearB is the radius of the driven gearF is the force at the rim of the gear. These forces are equal and opposite.

F x A = T1 T1 is the torque at the axle of the driver gearF x B = T2 T2 is the torque at the axle of the driven gear

Note that for the same force F transmitted from gear A to gear B, the torque on a gear and axle will be largest when the second gear B has the largest radius, and hence the largest number of teeth.

Remember, the torque changes from the driver gear to the driven gear because their radii are different. However, the force on the two meshing teeth will be the same, always. If the forces were different at the point of contact where the teeth mesh, then, from Newton’s law of motion, one of the teeth would accelerate faster than the other; this is impossible.

Also, since the teeth on both gears must be the same size, the number of teeth increases with circumference of the gear. Hence, the number of teeth on a gear will increase with increasing circumference, and increasing radius. The larger number of teeth means a larger radius, and hence a larger transmitted torque.

The Evaluating Gears sheet can be distributed to the students for practice. This sheet requires students to determine which of the two sets of gears (gear set 1 or gear set 2) in each trial yields the largest speed and which yields the higher torque. A typical result will look as follows.

Looking At Gears

Appendices

152

Number of Teeth onGear RatioA:B

Wheel - Driven Gear Check 1 or 2 that gives the Largest

Value of

Gear Set

Motor - Driver Gear A

Wheel - Driven Gear B

Speed Torque

1

2

15

15

45

75

3:1

5:1X X

1

2

10

10

50

100

5:1

10:1X X

1

2

9

9

45

40

5:1

4.4:1X X

1

2

5

5

90

58

18:1

11.6:1X X

1

2

45

45

15

5

1:3

1:9X X

TEACHER TIP Teachers can generate discussion by asking students if they recognize any pattern of ratios that appear in the data. Discuss with the students the inverse relationship between gear ratio and the number of teeth.

Facilitating Student Exploration. Ask the students what they have learned that will help them respond to the RFP. What have they learned that will help themachievetheperformancestandardsintheRFP?

• Thetimetoexceed5meterswithoutaload• Themaximumdistancetraveledwithoutaload• Thedistancetraveledwithaloadof300grams

Sharing and Interpreting. If students investigated bicycles as homework, discuss their answers to the questions as described in the What Do We Know About Gears section.

Ask students to share the results of the Evaluating Gears sheet. Have them explain how they reached their results.


Page ________________


Evaluating Gears Sheet

Number of Teeth onGear

Ratio A:B

Wheel - Driven Gear Check 1 or 2 that gives

the Largest Value of

Gear SetMotor - Driver Gear A

Wheel - Driven Gear B

Speed Torque

1

2

15

15

45

75

3:1

5:1

X

X1

2

10

10

50

1001

2

9

9

45

401

2

5

5

90

581

2

45

45

15

51

21

21

2

fuel cell book - awim.org · sae international is a nonprofit scientific organization dedicated to...

Documents