Make and Test Projects in Engineering Design

Andrew SamuelWith a Foreword by William Lewis

Make and TestProjects inEngineering DesignCreativity, Engagement and Learning

With 242 Figures

123

Andrew Emery Samuel, BMechE, MEngSci, PhD, DEng HonResearch ProfessorEngineering Design GroupMechanical and Manufacturing EngineeringUniversity of MelbourneVictoria 3010Australia

British Library Cataloguing in Publication DataSamuel, A. E. (Andrew E.), 1934–

Make and test projects in engineering design: creativity, engagement and learning1. Engineering design 2. Testing 3. Engineering models 4. Engineering educationI. Title620′.0044

ISBN 1852339152

Library of Congress Control Number: 2005925182

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Springer Science+Business Mediaspringeronline.com

…for my family and especially to Eva for just being…

Some day, when I'm awfully low,When the world is cold,

I will feel a glow just thinking of you...

Discovery is seeing what everybody else has seen and thinking what nobody else has thought. Albert Szent-Györgyi

Writing in a more relaxed age the French essayist, Montaigne, was scepticalof the value of knowledge divorced from personal experience. He wrote inhis essay “On Pedantry”:

I do not fancy this acquiescence in second-hand hearsay knowledge: for though wemay be learned by the help of another’s knowledge, we can never be wise but byour own wisdom.But life is more complex in the twenty-first century than Montaigne

could ever have envisaged. In engineering education, educators and stu-dents have to reconcile the thirst for an ever-expanding body of scientificknowledge with the need to engender and develop the crucial attributes ofprofessional life. This is the conundrum: professional engineering endeav-our is characterised not by the accumulation of knowledge but by responsi-ble action. Action centred around the identification and solution of techni-cal problems for the long-term benefit of the societies of which the engi-neers are members.

Efforts at reconciling knowledge and wisdom constitute an on-goingdynamic, ultimately enriching the lives of those who participate, those whoengage thoughtfully in the dialogue between the resources available to soci-ety and the fact that “great things are not done by those who sit down andcount the cost of every thought and act” (Daniel Gooch in his eulogy ofIsambard Kingdom Brunel).

Engineers continually reach out to test the limits of contemporary possi-bilities. The laws of science are inexorable, but this did not disconcert theyoung Whittle who recognised very early on in the development of the gasturbine jet engine that “our targets of performance for [the engine’s] com-pressor, combustion chamber assembly and turbine are far beyond anythingpreviously obtained with these components”. It is perhaps not surprisingthat Whittle gathered around him a design and development team of prima-

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FOREWORD

rily young engineers. Some of his dealings with older design engineers werevery negative; too often years of experience in a particular industry had ledto inflexible habits of thought; for them engineering design had become aroutine, a result which was the very antithesis of Whittle’s programme ofinvention and innovation.

How then to translate these thoughts into a successful programme ofendeavour in an undergraduate engineering course? We, the readers of thisbook, are fortunate that its author, Professor Andrew Samuel, has turned hisattention to the resolution of this conundrum. Professor Samuel has unri-valled experience as educator, author, researcher and practitioner, a personwho has reflected on and thought deeply about his life experiences in uni-versity and industry, who has published widely, and who outside his profes-sional work has designed and built his own home. So the business of trans-lating ideas into hardware is something with which he is very familiar.

Make-and-Test (MaT) projects afford a unique opportunity for engineer-ing students (and academic staff who should be encouraged to take part andlead by example) to put their talents of creativity and knowledge of physicsto the test, to combine sustained analytical thinking with the exercise of cre-ativity and imagination. And the results cannot be finessed. Participants –students and academic staff alike – have to accept responsibility for ademonstrable, tangible and public outcome. In a university career stretch-ing over several decades I have taken part in and witnessed many MaT proj-ects, and observed that successful outcomes were always achieved by a com-bination of imaginative synthetic thinking, sound physical understandingand unremitting attention to detail – all characteristics of good professionalpractice.

I commend this book to all those who think, as I do, that engineering edu-cation should offer memorable and liberating experiences to those partici-pating in a unique social enterprise. Practising designers too can employthis text as a self-learning resource, something to dip into whenever theyfeel the need for intellectual rejuvenation, the need to clear away the men-tal cobwebs accumulated through extended bouts of work on those routinematters of bookkeeping and administration always present to a greater orlesser extent in professional life.

William Lewis, University of Melbourne

April, 2004

Make-and-Test Projects in Engineering Design

viii

This is a book about inventing and testing of ideas. Of course, ideas don’tjust happen. They need to be engendered by some appropriate problem orproblem situation. My main purpose then is to describe how to generateengaging and motivating problem situations within the skill ambit of youngengineering students. It is hoped that many new ideas will be generated bythis process. Socrates used maieutics2 for seeking to expose ignorance and atthe same time to inspire a search for new knowledge. The basic purpose ofthe projects described in this book is to act both as an engaging challenge forstudents of engineering as well as a maieutic for giving practical birth tolatent ideas. Without this maieutic influence the projects might have theempty character of children’s play exercises.

Testing of ideas in a practical way challenges not only the validity of theideas but also the manufacturing skills of the participants. Because the scenefor all this inventing and testing sits within the engineering design course atMelbourne,3most of the project work is planned around the use of simplematerials such as balsa wood, newsprint paper and readily available plastics

ix

PREFACE: THE NEED FOR THISBOOK

The problem interested me because it illustrated the kind of invention which I like,one which nobody asked me for– You’re not sure there’s any good reason for it,but suddenly you begin to question “Can it be done?” And when you ask the ques-tion, the solution follows. One of the big tricks in inventing is not so much to inventthe “how”, but the “what”. In other words, the creating of the problem is as bigan invention as the solving of the problem– sometimes, a much greater invention.

Jacob Rabinow1

You see things; and you say “Why?” But I dream things that never were; and I say“Why not?”

George Bernard Shaw, The Serpent, in Back to Methuselah, Act 1, “In theBeginning”

1 De Simone (1968).2 Maieutic: serving to bring out a person’s latent ideas into consciousness (from Greek, maieutikas, to act as amidwife).3 Samuel (1984).

such as polyurethane foam, for example. Sometimes more exotic materialsare used, such as fibre glass–epoxy composites, candle wax, rubber balloons,aerosol deodourant, mousetrap springs and even spaghetti. Yet, in spite ofthe varied and sometimes unfamiliar nature of these materials, all of theseinventions are intended to be well within the ingenuity and skill range offirst and second year engineering undergraduates. Occasionally profession-al engineering societies offer creative challenges to anyone interestedenough to be challenged. This book is also addressed to participants in suchprojects, whatever their background or skill level. In essence then, the mate-rial tries to encapsulate the experience of engineering design, from theuncertainty of “Can I tackle this problem?” to the “aha!” experience of thejoyous discovery of a suitable solution. Although the major part of the bookis devoted to “neatly frozen” case examples from the Melbourne design pro-gramme, there are many opportunities and exercises throughout the text toexplore new make-and-test (MaT) projects. In fact Jacob Rabinow’s wordsabove set the scene for the primary purpose of this book, namely to articu-late the process of inventing challenging and interesting MaT design exer-cises for undergraduate engineering students.

Bernard Shaw’s quotation above provides the background for exploringthe nature of engineering education. Engineering science provides the basictools for predicting the behaviour of materials and processes we use forbuilding artefacts. Engineering design uses these basic tools to build newartefacts. A problem intrinsic to engineering education is how to combinethe progressive serial thinking needed in engineering science, with the lat-eral “thinking outside the square” style of thinking needed in the world ofdesign synthesis. In this context, the book is also addressed to engineeringeducators who may be grappling with this problem.

In the heady days of the industrial revolution and through the early partsof the last century, the arts and crafts of engineers were often acquiredthrough a master–apprentice process of learning. James Watt was appren-ticed to his father Thomas Watt as an instrument maker. Michael Faradaywas a laboratory assistant to the nineteenth century chemist Sir HumphreyDavey, the discoverer of the element chlorine. Thomas Telford, the nine-teenth century civil engineer was an apprentice stonemason and eventuallythe surveyor of public works. Robert Stephenson was apprenticed to hisfather George as an enginewright. When academic resources were plentifuland there was time to experiment with learning programmes the master-apprentice learning process translated into the small tutorial style of men-toring. In a world of shrinking academic resources and growing need to jus-tify how we spend these resources, it is prudent to examine such issues as“educational effectiveness” and “educational efficiency”. The first of these

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Make-and-Test Projects in Engineering Design

issues, educational effectiveness or the basic question of “Have we learntanything useful from this experience ?” may well be addressed at the occa-sionally perceived to be frivolous nature of MaT projects. The fundamentalthesis of this book is that, if properly organised, planned and administered,significant learning takes place during MaT projects. In this context admin-istration does not refer to the simple nuts and bolts of how many studentsto a group or how many groups to a tutorial class, but to the way in whichMaT projects areplanned and executed. Moreover, organisation and plan-ning also embrace the way we elicit the thinking progression and self-aware-ness of students in their reporting process. This is the main Socratic maieu-tic embedded in MaT projects.

Educational efficiency is the ratio of some quanta of learning to the edu-cational resources spent in the process. MaT projects set the scene for themore traditional style of design projects, and I conjecture that virtually thesame quanta of learning are acquired in those traditional design exercises asin the deceptively simple MaT project. The uninformed may perceive MaTprojects as frivolous or even trivial. After all, who in our professional lifewill ever ask us for the design of a balloon-driven vehicle? The essence ofan introductory MaT project is its engaging quality. Experienced educatorsare well aware of the critical differences between teaching and learning.Teaching is planning and delivering educational programmes. Learning mayor may not take place in these programmes. As children develop theyacquire knowledge through their various senses. Touch and feel presentopportunities for exploring the world around us as infants. Open-ended art-work and colourful constructions in paper and other materials lead the wayto further discoveries in preschool. Much learning takes place during achild’s progress through to formal school. Once there, however, resourcelimitations preclude the use of experiential exploration of the world aroundus. Formal educational programmes have a kind of regimented quality aboutthem. MaT projects are a way of re-engaging the informal exploration of theworld through challenging engineering problem situations. Once re-intro-duced to this type of informal childlike explorations of engineering, formaleducational programmes inherit the benefits of engagement. This is thebeginning of thinking like engineers. At the other end of the value scale MaTprojects should not be treated as lifelong learning experiences. Taking thembeyond these early introductory design experiences is weighed down withthe real danger of identifying the serious goals and value systems of designwith these early play-exercises. Engagement with engineering design think-ing can occur in brief one-off MaT projects. Taking them beyond that mayseriously reduce their longer-term effectiveness.

xiPreface

As an anecdotal frame of reference I recount the tale of two university cul-tures and their widely different approaches to the teaching of undergradu-ate engineering design. One culture is arbitrarily titled the ClassicalEstablished University (CEU) and the other is equally arbitrarily called theNew Age Caring University (NACU).

At CEU design is treated as an adjunct to the meat and potatoes of the engi-neering sciences. Design tasks are often reheated or slightly modified versionsof design projects that have gone before, with staff and students merelygoing through the motions according to an established educational formu-la. This is a metaphor for the pejorative classical definitions of lectures asquasi-educational activities, where the lecturer’s notes are merely tran-scribed into the student’s notebook without entering into the minds ofeither party.

At NACU the design task is embedded in a matrix of various right-brainstretching activities such as finger-painting to jazz, evocation of fantasy sit-uations and an almost evangelical approach to creative behaviour. Yet neitheruniversity seeks to examine, in a scientific way, the effectiveness or efficien-cy of their teaching methods in design. They make no attempt at bench-marking their approaches to those of other institutions. In fact, a key simi-larity of the vast majority of undergraduate engineering design programmesthroughout the world is their lack of comparative evaluation with othercourses. Many such courses offer the type of MaT projects described in thisbook. These projects, as do almost all properly resourced design projects,absorb significant staff and student resources. It would seem reasonable toevaluate the amount of learning to be gained from such projects in relationto the quantity of resources they consume. Yet few if any engineering designprogrammes carry out such comparative studies.4

The primary purpose of this book is to help engineering design educatorsin planning and delivering MaT projects and to help young engineering stu-dents in planning the solution to MaT projects. A secondary, though equal-ly important, purpose is to examine the benefits and costs of MaT exercisesfor all concerned, the educators as well as the students. In addition, ques-tions are raised (not all of them answered) about the process of learning inengineering design, about problem solving in groups and about communi-cating engineering design ideas.

Chapter 1 is a brief introduction to design problems and designthinking. Chapter 2 is specifically addressed to the design educator.The chapter explores issues concerned with learning effectivenessand efficiency with special focus on the discipline of engineeringdesign. Although there is a considerable volume of literature on engi-

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Make-and-Test Projects in Engineering Design

4 Weilerstein (1999).

neering education, some of the issues being re-discovered in this fieldhave been well explored in the greater body of general educationalresearch. There are pointers and references to some of these issues inChapter 2. Chapter 3 introduces the genesis of MaT projects, together withnotions of creative behaviour, student engagement and a brief taxon-omy of MaT projects.

Chapter 4 is a compendium of material properties, with special refer-ence to the unconventional materials and devices used in MaT proj-ects. The focus here is on experimental exploration of material behav-iour where data from established sources are not readily available.The experimental evaluations make use of readily available simplehousehold equipment. Apart from documenting material propertiesand energy sources for MaT projects the intention of this chapter isto encourage students to experiment and to collect their own evi-dence of material behaviour wherever possible.

Chapter 5 presents documented case studies of MaT projects dealingwith static structures, representing a selection from those conductedover a period of 25 years at the University of Melbourne. Chapters 6 and 7 introduce dynamic MaT projects and documentedcase examples of a sample set from those conducted at Melbourne. Chapter 8 concludes with a brief introduction to open-ended styleMaT projects and opens the horizon to a substantial set of similarprojects, together with some sources for generating similar MaT proj-ects. Because these types of projects are generally untidy student and staff

experiences, with some degree of confusion during progress, the documen-tations are sanitised versions of reality. In general, engineering design expe-riences recounted in reports read better than they lived. This feature ofMaT projects is very similar to the experiences of professional engineeringdesigners during the early ideation and development phases of “real life”engineering projects. Perhaps an unusual feature of some documentedMaT projects presented is those where we have asked our students to devel-op a mathematical model of their MaT exercise and to predict the behaviourof the specific structure or device being constructed.

The book concludes with a substantial reference list and bibliography aswell as appendices with conversion tables and some simple models of struc-tural and dynamic behaviour.

Throughout the text there are many exercises to stimulate engagementand attention. Solutions to selected exercises are offered in the appendix. As

xiiiPreface

well, there are many proposals for suitable MaT projects, with some sug-gested performance criteria, but complete specifications are left for the userto prepare. This aspect of MaT projects is probably the most challengingand should engage both the educator and the student.

Andrew SamuelMelbourne, April 2004

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Make-and-Test Projects in Engineering Design

Quite apart from the many design teams involved in delivering those some-times ingenious devices described in this book, there are many colleagueswho encouraged, inspired, supported and, at times, consoled me during thisproject. The “project” I refer to is not only the book, but all the many designexercises that led up to its production. The most inspiring feature of designeducation is the wonderful and often challenging intellect that shinesthrough countless interactions with design teams. The student participantsin my “project” are too numerous to mention individually, but I am eternal-ly grateful for the opportunity to have had the privilege of working with allof them.

There are many colleagues to whom I also owe a debt of gratitude, notonly for the encouragement and inspiration, but also for the continued sup-port of the MaT project programme at Melbourne. First and foremost Imust acknowledge William (Bill) Lewis, who was mostly responsible for myfreedom to pursue these unconventional, and sometimes crazy, design proj-ects. It is hard to pin down the origin of some of the MaT projects describedin the book. Some came from personal interests, others were suggested bycolleagues, but many came from, or were substantively refined at, coffeetable discussions in the Mechanical Engineering Staff Common Room andat University House. For their never-ending enthusiasm and ideas I amindebted to Ken Brown, Collin Burvill, Bruce Field, Ted Grange, TonyPerry, Peter McGowan, Bob Steidel, Craig Tischler, John Weir and severalothers, whose names have sadly left my increasingly feeble memory.

Even in this brief acknowledgement it would be remiss of me to leave outmention of the inspiration I have gained from yet another source. There wasa time in academia, now almost lost in the mist of economic rationalism,

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ACKNOWLEDGEMENTSMorris read through the letter. Was it a shade too fulsome? No,that was another law of academic life: it is impossible to beexcessive in flattery of one’s peers.

David Lodge, Small World 1984

when academic staff were able to meditate on the purpose and meaning oftheir existence. A special agency that aided and supported that process wasMcAree-Meikle International, an organisation deeply committed to poking funand occasionally nail-biting parody at anyone who took themselves too seri-ously, including me and several of my “driven” colleagues. For their contri-butions I am most grateful to Ross McAree, Peter Meikle and their closeassociates, Mustafa Camel, Dr. H. Jorgen, S. Mantra Prahabu and last, butby no means least, that doyen of neatness and fashion cravat, once voted themost beautiful person on the planet, Harvey Waston.

Andrew SamuelMelbourne

2004

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Make-and-Test Projects in Engineering Design

Foreword vii

Preface ix

Acknowledgement xv

1. Introduction 1

2. Invention, Creativity, Engagement 132.1 Inventing, Inventions and Design 172.2 An Instructive Example: The Can Opener 232.3 Cognitive Science, Creativity and Analysis in Design 312.4 Engagement and Learning 382.5 Some Examples of Generic MaT Projects in

Engineering Design 422.6 The Benefits and Costs of MaT Projects 452.7 Chapter Summary 52

3. The Genesis and Development of MaT Projects 533.1 MaT Projects Using Static Structures 53

Design for Axial Loading (Struts) 54Design for Transverse Loading (beams) 55

3.2 MaT Projects Designed to Use Moving and Dynamic Devices 58Energy Sources 58Potential Performance Requirements and Variables 59Wheeled Vehicles 59Vehicles Designed to travel in or Over Water 61Airborne Vehicles 63Devices with Mixed Performance Requirements 63

3.3 Some Key Materials of Construction 653.4 Level of Difficulty and Complexity of Projects 663.5 Team Dynamics 70

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CONTENTS

3.6 Morphology of MaT Projects 713.7 Chapter Summary 76

4. Properties and Application of Some Unconventional Engineering Materials 774.1 Balsa Wood 78

Mechanical Properties 804.2 Newsprint 82

Mechanical Properties of Paper 884.3 Polymers, Composites, and Other Strange Structural

Materials 89Rigid Polyurethane Foam and Foamcore 89Bamboo Skewers 90Drinking Straws, Spaghetti 91Cotton Thread 92

4.4 Establishing Mechanical Properties for Materials Used in MaT Model Construction 93Testing Balsa Wood 93Testing Newsprint 95Testing of Other Unconventional Structural Materials 96Some Additional Notes on Testing and Failure Behaviour 97

4.5 Adhesives 984.6 Test Results for Mechanical Properties of MaT

Project Construction Materials 1014.7 Chapter Summary 106

5. MaT Projects for Static Load-bearing Structures 1075.1 Sample MaT Project Problems and Presentation 1075.2 Case Examples of Static MaT Projects 113

5.2.1 Balsa Bridge 1135.2.2 Balsa Structure 1165.2.3 Paper Column 1185.2.3 Urethane Foam Structure 122

5.3 Supplementary Opportunities for Static MaT Projects 125

5.4 Chapter Summary and Caveats 128

Make-and-Test Projects in Engineering Design

xviii

6. Dynamic MaT Projects: Things That Go “Bump” 1296.1 Energy Sources and Their Measurement 130

Thermal Energy 130Potential Energy (Gravity Driven) 132Kinetic Energy 133Elastic Energy 135Electrical Energy Sources 139

6.2 A Panoply of Dynamic MaT Projects 142Fetch and Carry MaT Projects 143Navigationally Challenged Vehicles 144“How Can it be Done?” Projects 144

6.3 Administration and Conduct of Dynamic MaTProjects 145

6.4 Case studies of Dynamic MaT Projects 1496.5 Experimental Evaluation of Energy Available

from Various Sources 150Energy from Toy Rubber Balloons and Mousetraps 150

6.6 Chapter Summary 154

7. Case Examples of Dynamic MaT Projects 155Projects with Special Focus on Energy Capture and Conversion 156Projects Involving Water-based Transport 156Projects Using Ground Transport 157Airborne MaT Projects 157

7.1 A Generic MaT Project Case ExampleA Beverage Can Roller (ABC) 157Sample Entries 159

7.2 Three More Documented Case Examples 168Case Example 2 – Walking on Water (Aquaped) 168Case Example 3 – One Candle-power Engine (OCPE) 176Case Example 4 – Mechanical Frog (JFC) 186

7.3 A Brief Description of Other MaT Projects 193Daring Young Designers and Flying-machines(DYDaF) 193

xixContents

Payloads on Pools (PoP) 194Projects Involving Direct Head-to-head Contests (Drawbar Pull) 196Projects Using Various Novel Forms of Energy 197Climbing and Jumping MaT Projects 197

7.4 Some Concluding Notes on Design Guidance andEngagement 201

7.5 Chapter Summary 202

8. Concluding Notes and Some “CUTIEs” 2038.1 CUTIE 1: Temperature-controlled Soldering Iron 2048.2 CUTIE 2: Galileo’s Thermometer 2058.3 CUTIE 3: Tensegrity Structures 2078.4 CUTIE 4: Renewable Energy Sources 209

Wind Farms 209Energy from the Ocean 209

8.5 Demonstration of Physics Principles 211MaT Project Metaphor 211

8.6 Some Further Interesting Problems 218The Shape of Things 219The Way Things Work 221Limits of Performance 223Some Not-so-clever Inventions 223Creative Ideas and Patents 225

8.7 Chapter Summary 228References and Bibliography 229

Engineering Case Library 241Readings for MaT Project Planning 242

Appendix A1. A Primer on Mechanics 243A1.1 Statics 243

A1.1.1 Forces 243A1.1.2 Planar Pinned Structures 245A1–1.3 Bending 248A1–1.4 Torsion 251

A1.2 Dynamics 252A1.2.1 Force and Acceleration 252

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Make-and-Test Projects in Engineering Design

A1.2.2 Work and Energy 254A1.3 Very Elementary Gas Dynamics 257A1.4 Newton or Aristotle? 261

Appendix A2. Units of Measurement and Conversion Factors 263

Systems of Measurement and Standardisation 264The Seven Fundamental SI Units 265Some Derived Units and Dimensions 265Conversion Factors 268

Appendix A3. Some Properties of Plane Sections and Answers to Selected Exercises 269

Index 273

xxiContents

Basic Design Terminology

Unlike Carroll’s Humpty Dumpty, design professionals cannot simplyinvent meanings for words. In 2000, Samuel et al. remarked:5

Engineering designers invest substantial effort in intellectual argument. There arenational or international engineering design conferences almost every year. Oftenthere are several such conferences in the same year. There are several journals thatprovide communication between the engineering design community. Yet we use ter-minology in the engineering design context rather loosely. The result is that “designlanguage” is treated by practitioners and others in the same way as any other spo-ken language, namely as context based interpretive reasoning. This rather cavalierapproach to the fundamental tool of design, namely “codified reasoning based onlanguage” has tended to relegate design to a soft discipline.

Although certain words may be imposed on design by necessity of dealingwith an eclectic range of design problems drawn from a wide variety ofengineering sources, some design terms must be seen as basic and almostinviolable to communication between designers and their clients. An excel-lent start for identifying the proper meaning and usage of some of thesebasic design words is the Oxford English Dictionary (OED). This work isprobably the greatest literary achievement in the English language, and is inno small way responsible for English being the second most spoken lan-guage in the world. It would therefore seem arrogant to ignore the OED’setymology6 when using the English language as a means of formal commu-nication. Historically our language (English or design) is organic and isundergoing changes as our life experiences change. Some words diethrough neglect (e.g., the archaic meaning of shambles is a market place or

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GLOSSARY OF COMMONLY USEDDESIGN TERMS AND SYMBOLS

“I don’t know what you mean by ‘glory,’ Alice said.Humpty Dumpty smiled contemptuously. “Of course you don’t–till I tell you. I meant ‘there’s anice knock-down argument for you!’”“But ‘glory’ doesn’t mean ‘a nice knock-down arument,’” Alice objected.“When I use a word,” Humpty Dumpty said, in a rather scornful tone, “it means just what Ichoose it to mean–neither more nor less.” Lewis Carroll, Through the Looking-Glass (1872)

5 Samuel et al. (2000).6 Etymology is the account of or facts relating to formation of words and development of their meaning(OED).

xxiv

slaughter house – OED) and others are born to facilitate communication in achanging world (e.g., Internet, software and afterburner are typical examples oftwentieth century word inventions). The OED is based largely on commonusage that existed in written text in 17th and 18th century literature. In par-ticular early 18th century writings had amazingly numerous word inven-tions that were intended to make the writer appear more erudite. In writingabout the word lists of the time Simon Winchester notes:7

So, fantastic linguistic creations like “abequitate”, “bulbulcitate” and “sulleviation”appeared in these books alongside “Archgrammacian” and “contiguate”, withlengthy definitions…

Communicators in engineering design are equally capable of the odd ver-bal invention. Perhaps (to this author) the most disturbing example is thereckless use of ontology, for what is in reality a taxonomy or classification ofwords and meanings.8 Bearing these matters in mind, the only caution tointending design communicators is that if there is a useful and readily avail-able plain English word for whatever one would wish to communicate, thenavoid inventing a new one. The following words should be regarded as invi-olable engineering design terminology(some have well defined etymologyin the OED):9

• Design Need: The primary motivation for a design investigation(usually expressed in the form of a problem statement – e.g., “Thereare too many automobile accidents during holiday periods” or “My arthrit-ic aunt is unable to open her milk carton”);

• Design goal: The primary functional objective of a design (usuallyexpressed in terms of outcomes without reference to embodi-ment – e.g., “a means for delivering a payload along a water channel”rather than “a boat” );

• Design objectives, or design requirements: Desired features or charac-teristics of a specific design (e.g., “safe”, “reliable or robust”, “cheap”);

• Constraint: Mandatory design requirement (e.g., “the device mustweigh less than 5 kg”, or “It must be inflammable”);

• Restriction: Flexible design requirement (e.g., “The lecture theatreshould accommodate 200 students”, or “The cockpit should accommodate98% human population size”);

• Criterion (or criteria – plural): The scale on which the “fitness forpurpose” of the design is measured (e.g., for cheap the criterion is $,

Make-and-Test Projects in Engineering Design

7 WInchester (1999). 8 Samuel et al.(2000), Ibid.9 Refer also to the Design Lexicon at www.mame.mu.oz.au/eng_design/language/language.html.

or whatever monetary unit is in use, for reliable or robust the crite-rion is mean time to failure or mean time to repair, for comfortable thecriterion is the subjective judgement of a group of end users of the prod-uct).

Criterion is probably the most often misunderstood or mis-used engi-neering design term. Yet, equally probably, it is the single, most preciselydefinable, basic design term in the brief list offered here. Proper use of thesefew terms in the early definition stages of a design can yield substantial ben-efits for the design team.

Commonly Used SymbolsA, a area, cross-section area, accelerationCp, Cv specific heat (at constant pressure or volume = heat

energy needed to raise the temperature of a gas by one degree K)

D, d diameterE Modulus of elasticity, (Young‘s modulus)F, f force, friction factorg acceleration due to gravityIzz second moment of area, mass moment of inertia

k, K spring stiffness, kinetic energyl, L length dimension m massp pressurer, R radiusSU ultimate tensile strength

SY yield strength

t, T time, material thickness, temperaturev, V velocity, electric potential a thermal coefficient, angled small change in quantity, deflection of beame strain (fractional change in length)q, f angle, twist/unit lengthm Poisson’s ratio r densityp ratio of circumference to diameter of circles direct stresst shear stress

xxvDesign Terminology