Technology 1º & 2º ESO

8/14/2019 Technology 1 & 2 ESO

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This book is dedicated to you.I hope it will be your favourite book.

ISBN: 978-84-614-2786-42nd edition

2011

Author: Gonzalo Morillo Dez

Editors: Mathew Mendoza & Ann Taylor

www.esobook.net

[email protected]


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IndexSection 1 Technology and Projects

CHAPTER 1 - WHAT IS TECHNOLOGY? ....................................................................... 6

1.1 I S TECHNOLOGY RELATED TO SOCIETY? ............................................................................................... 6

1.2 N AMES OF THE TOOLS IN THE WORKSHOP ........................................................................................... 8

CHAPTER 2 - PROJECTS ........................................................................................... 14

2.1 R ESOLUTION OF TECHNOLOGICAL PROBLEMS ..................................................................................... 14

2.2 S TEPS OF A PROJECT .................................................................................................................... 15

2.3 E XAMPLE OF THE DOCUMENTS OF A PROJECT ..................................................................................... 20

Section 2 Drawing

CHAPTER 3 - DRAWING TOOLS AND BASIC TECHNIQUES. ...................................... 22

3.1 D RAWING TOOLS ........................................................................................................................ 22

3.2 B ASICDRAWING TECHNIQUES ....................................................................................................... 25

CHAPTER 4 - ORTHOGRAPHIC DRAWING ................................................................. 27

4.1 DRAFTING ..................................................................................................................................... 28

4.2 DRAWING ..................................................................................................................................... 284.3 STANDARDIZATION ......................................................................................................................... 29

4.4 FIRST ANGLE PROJECTION ................................................................................................................. 30

Section 3 Materials

CHAPTER 5 - PROPERTIES OF MATERIALS .............................................................. 36

5.1 C LASSIFICATION OF MATERIALS ...................................................................................................... 36

5.2 P ROPERTIES OF MATERIALS ........................................................................................................... 36

CHAPTER 6 - WOOD ................................................................................................ 42

6.1 P ROPERTIES AND COMPOSITION OF WOOD ........................................................................................ 43

6.2 P ROCESSING AND TREATMENT OF NATURAL WOOD ............................................................................. 43

6.3 S OME COMMONLY USED TYPES OF WOOD ......................................................................................... 44

6.4 A RTIFICIAL WOOD PLANKS ............................................................................................................. 46

6.5 A PPLICATIONS OF NATURAL AND PROCESSED WOOD. ........................................................................... 46

6.6 P RODUCTION OF PAPER ................................................................................................................ 47

6.7 T OOLS AND TECHNIQUES FOR WOODWORKING .................................................................................. 47


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CHAPTER 7 - METALS ............................................................................................... 52

7.1 STEEL

....................................................................................................................................... 537.2 C AST IRON ................................................................................................................................. 53

7.3 P RODUCTION OF CAST IRON AND STEEL............................................................................................ 54

7.4 S PECIALSTEELS ........................................................................................................................... 55

7.5 N ON FERROUS METALS AND THEIR PROPERTIES .................................................................................. 56

7.6 N ON FERROUS ALLOYS AND THEIR PROPERTIES ................................................................................... 57

7.7 M ETALWORKING ........................................................................................................................ 57

Section 4 Structures, Mechanisms and ElectricityCHAPTER 8 - STRUCTURES ....................................................................................... 60

8.1 T YPES OFSTRUCTURES ................................................................................................................. 60

8.2 S TRUCTURALELEMENTS ................................................................................................................ 63

8.3 T YPES OFUNIONS ....................................................................................................................... 63

8.4 F ORCES ON STRUCTURAL ELEMENTS ................................................................................................. 64

8.5 A PPLICATIONS ............................................................................................................................ 66

8.6 A NALYSIS OF STRUCTURAL BEHAVIOUR, USING DIFFERENT MODELS ......................................................... 66

CHAPTER 9 - MECHANISMS ..................................................................................... 68

9.1 B ELTS ....................................................................................................................................... 69

9.2 P ULLEYS .................................................................................................................................... 69

9.3 LEVERS ..................................................................................................................................... 70

9.4 G EARS ...................................................................................................................................... 72

9.5 CRANKSHAFT .............................................................................................................................. 74

9.6 CLUTCH ..................................................................................................................................... 74

9.7 BRAKES ..................................................................................................................................... 74

CHAPTER 10 - ELECTRICAL CIRCUITS ........................................ ................................ 75

10.1 W HAT IS AN ELECTRICAL CIRCUIT? ................................................................................................... 76

10.2 A PPLICATIONS OF ELECTRICITY ....................................................................................................... 77

10.3 E LEMENTS OF AN ELECTRIC CIRCUIT .................................................................................................. 78

10.4 E LECTRIC SYMBOLS ...................................................................................................................... 79

10.5 C IRCUIT DIAGRAMS ...................................................................................................................... 79

10.6 M AGNITUDES IN ELECTRIC CIRCUITS ................................................................................................. 80

10.7 TYPES OF CIRCUITS AND THEIR PROPERTIES ........................................................................................ 82


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Section 5 Energy and Machines

CHAPTER 11 - NON-RENEWABLE SOURCES OF ENERGY............................................ 84

11.1 URANIUM ............................................................................................................................. 86

11.2 COAL .................................................................................................................................... 87

11.3 CRUDE OIL ............................................................................................................................ 87

11.4 NATURALGAS ...................................................................................................................... 90

CHAPTER 12 - RENEWABLE SOURCES OF ENERGY ...................... ............................. 92

12.1 HYDRO-ELECTRIC DAMS ........................................................................................................ 93

12.2 W IND POWER ....................................................................................................................... 94

12.3 SOLAR POWER ...................................................................................................................... 96

12.4 NUCLEARFUSION ................................................................................................................. 97

CHAPTER 13 - THERMAL MACHINES ...................................................................... 100

13.1 EXTERNAL COMBUSTION ENGINES ....................................................................................... 101

13.2 INTERNALCOMBUSTION ENGINES ...................................................................................... 103

13.3 ENVIRONMENTAL EFFECTS OFFOSSILFUELS ....................................................................... 107

13.4 REFRIGERATORS AND AIR CONDITIONERS ........................................................................... 107

Section 6 Computing

CHAPTER 14 - HARDWARE AND SOFTWARE .......................................................... 110

14.1 WHAT IS A COMPUTER? ....................................................................................................... 110

14.2 HARDWARE .......................................................................................................................... 110

14.3 SOFTWARE ........................................................................................................................... 113

CHAPTER 15 - COMMUNICATION TECHNOLOGY: THE INTERNET ............................ 119

15.1 HISTORY OF THEWEB ........................................................................................................... 120

15.2 THE TECHNOLOGY BEHIND THEWEB ..................................................................................... 121

15.3 STRUCTURE OF THE INTERNET ............................................................................................... 122

15.4 SEARCHING FOR INFORMATION ON THE INTERNET ................................................................. 123

15.5 THE COMPUTER AS A COMMUNICATION TOOL : EMAIL, CHATS, VIDEO-CONFERENCING. ......... 125


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Chapter 1

WHAT ISTECHNOLOGY?

Technology is how we make things, things that make our lives more comfortable and ourwork more productive: ploughs, chairs, telephones...

In technology we use tools and knowledge to make things.

1.1 I s technology related to society?Yes, for example, thanks to telephones, we can talk to people who are far from us. Buttelephones exist because we want to talk to people who are far from us.

The relation between science and technologyis strong.

For example, telescopes help us understandthe universe, and understanding the universehelps us to construct satellites.

Homo Habilis started technology with atechnique to make fire.

This happened hundreds of thousands ofyears ago.

Fire was good for heating and grilling meat.


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Later, people converted natural resources into simple tools, for examplestone axes.

Axes are good for cutting trees.

Modern humans continue to inventthings.

The wheel (invented around 2700 BC)helps us to travel and transportmerchandise.

It is hard to imagine today`s worldwithout the wheel.

Recent technological developments, the printing press, the telephone, theinternet, etc. help us to communicate on a global scale.

Technology helps develop more advanced economies.

But we dont always use technologypeacefully. Weapons are now morepowerful.

Many technological processes produceunwanted by- products, called pollution .

Technological activities consume naturalresources.

Experts propose a change in our way oflife to reduce pollution emissions.

Some new technological developments raise ethical questions, especially in biotechnologyand genetic engineering.

1 Imagine the world without technology. Describe it.

2 Which do you think that is the best invention? Why?

3 Debate the present and future of technology in society. How do you thinktechnology will be in ten years?

4 Name three technologies that help us to communicate.


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1.2 Names of the tools in the workshop

Metal FileWe use the metal file to remove small amounts of metal.

You can also use it to remove small amounts of wood. We get abetter finish than with the wood file.

The finish is better with the metal file than with the wood filebecause the grooves of the file are smaller. That is also why themetal file removes less material.

Wood FileThe grooves of the wood file are large.

We use it to remove parts of the surface of the wood and to give afinish to the surface.

The wood file removes more wood than the metal file, but thefinish is worse.

HammerYou probably know how to use it, but be careful!

Hammers normally have a wooden handle ; wood is light andabsorbs vibrations well.

The head is metallic. Metals are heavy and resilient (resistant tofracture by impact).

RulerWe use the ruler to draw straight lines and also to measure things.

Normally, on one side there is a scale in centimetres andmillimetres and on the other there is a scale in inches and eighthsof an inch.

There are ten millimetres in a centimetre. There are eight eighthsof an inch in an inch.

In some countries people use inches as a unit of length. One inch is

approximately two and a half centimetres.


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Hand Clamp

We use the hand clamp to hold togethertwo pieces .

For example, if we want to glue twopieces of wood with a glue that takestime to set, we can use the hand clampto keep the two pieces together whilethe glue sets.

The jaws are made of metal.

The sliding jaw has an inner thread forthe shaft , which has a screw to tightenthe wood pieces .

Handles are made of wood or plastic with rubber.

The bars are made of steel or aluminium. They have stops to keep the sliding jaw in position.

If the bars are made of aluminium they are lighter; if they are made of steel they arestronger.

Bench Clamp

We use the bench clamp to hold pieces that we want

to work with.For example, we clamp a wood board to saw itcomfortably.

The bench clamp is stronger than the hand clamp andis fixed to the bench.

The bench is the workshop table, made of a thickboard.

5 When would you use:a) A wood file c) A ruler

b) A metal file d) A bench clamp

6 How many centimetres are 5 inches?

7 Name the parts of the hand clamp and explain their function.

8 Why do you think that we work more comfortably with the bench clamp?


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Flat screwdriverAs its name indicates, the head of the flatscrewdriver is flat.

It is used to screw and unscrew screws with a singleslot in their head.

Cross head screwdriverThe difference between the flat head and the crosshead screwdrivers is in the tip.

The cross head screwdriver has a crossed-head tipand the flat head screwdriver has a flat tip.

Pliers We use pliers for a variety of purposes. The mostcommon use is to grip objects to work with them,for example to undo a bolt or to bend a wire.

Pliers have parallel handles , a spindle where thehandles join, and parallel jaws that grip the object.

There are special pliers for specific purposes, suchas cutting wire or bending wire.

A special type of pliers is the plumber's pliers, onwhich we can adjust the width between the jaws.

Scissors

Scissors have two steel blades that rotate around aspindle screw .

A pair of scissors cuts better or worse dependingon how sharp the blade edges are.

In the handle there are holes for the fingers so thatwe can move both blades at the same time withonly one hand.

The handle is normally made of plastic glued to thesteel.


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Wood Saw

There are many types of saws, eachdesigned for a specific purpose.

Some are rigid so that the cut is straight.

Some are good to cut curves.

Some are good to cut big things.

If the teeth are big, the cut is rougher.

If the teeth are small, the end result is smoother.

Metal SawThere are many types of metal saws, but the most commonone (and the one which you probably have in theworkshop) is like the one shown here.

The difference from the wood saw is in the teeth of theblade.

The teeth of metal saws are smaller, so we remove lessmaterial with each stroke.

The teeth of metal saws are made of a much hardermaterial.

The teeth must be harder than the material that they cut.If not, the teeth soon wear down.

9Which tools have:a) A handle c) A spindle e) Teeth

b) One blade d) A flat tip f) Two blades

10 Name two tools that have a spindle.

11 Describe the teeth of the metal saw.

12 Name the parts of a pair of scissors.

13 Do you have tools at home? What tools? What do you do with them?14 Imagine a new tool. Describe what it does, its shape


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Vernier calliperWe use the calliper to measure small things with precision (0.1 mm).

1st We put the object that we want to measure between the two jaws.

2nd We slide the sliding jaw until both jaws gently enclose the object.

3 rd We look at the main scale of the caliper. The value of the main scale that coincideswith the zero mark of the Vernier scale is the length of the object in millimetres, forexample, 135mm.

4 th If the zero mark of the Vernier scale does not coincide exactly with a millimetre markon the main scale , we take the smaller value.

5 th To know the decimals of millimetre we look at the Vernier scale .

There is a mark on the Vernier scale that coincides with a mark on the main scale , itis the value of decimals of millimetre.

For example, if the mark that coincides is the 7, then it is 0.7mm.

Adding both numbers gives the dimension: 135.7mm.

Spanner Spanners are the tool to tighten and loosen nuts and bolts.

There are several types: the open spanner, the ring spanner and the adjustable spanner.

The story of the adjustable spanner started in Swedenin 1886, in the mechanical workshop of Johan PetterJohansson.

At that time there was no standardisation of the sizes ofnuts and bolts and it was necessary to have manydifferent spanners.

Johan thought of having only one spanner with anadjustable width and so he designed, patented and

made the first adjustable spanner.


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Activities

1 What is technology?2 Write six examples of the relation

between technology and society.

3 Name three inventions that helpus to communicate.

4 Which was the first technologicaldevelopment?

5 Search for information about theorigins of paper. Write down a 20lines summary.

6 Which type of file has smallergrooves? Why?

7 Why do you think that hammershave a:

a) Wooden handle

b) Metallic head

8 Using a ruler with two scales, onein centimetres and one in inches,draw a line of ten centimetres andthen measure it with the inchesscale. How many inches long is it?

Now, using the inches scale, drawa line two inches long and anothersix inches long. How manycentimetres long are they?

9 What happens if you saw with asaw that has:

a) Large teeth

b) Small teeth

10 Technology sometimes has aspecific vocabulary. For example,technological items are oftenmade of parts with specific names.

For example a boat has severalparts.

Choose another object, forexample a lamp, a bicycle, a tap draw it and write the names of itsdifferent parts.

11 What do we use the calliper for?12 With the calliper, measure the

width of an object.

Write down your reading. In theexample the reading is 47.2 mm .

Compare your readings with thereadings of other students.

13 Why did Johan invent theadjustable spanner?

14 Can youthink of anewinvention forthe future?


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Chapter 2

PROJECTS 2 .1 Reso lu t ion of t echn olog ica l p rob lem s

Finding solutions to problems or needs requirescomplex thinking; it is one of the most advancedintellectual functions.

We search for solutions when we do not knowhow to go from a starting point to a desired goal.

Resolution of problems is part of a larger processthat includes understanding the needs of theuser.

Projects in technology are normally done byteams, not by individuals working alone.

One person can do small tasks, like replacing alight bulb. Teams can do larger projects, likeconstructing a car.

One of the most difficult things is to decide what

tasks are necessary.

The team agrees on the tasks for each member.

For example, Sarah does the drawings, Thomascuts the wood, Anna glues the pieces andeveryone works together to complete the project!

If you want the team to work well, it is importantto learn the different steps of a project, frombeginning to end.

It is best to follow the steps in the correct order.


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2.2 Steps of a pr oject

There are many ways to organize a projectfrom beginning to end.

Normally we divide the project into steps.

To be sure that we all work in the sameway, we should all follow these steps:

1 Specify the needIn this first step, we describe the problem.

Listen carefully to the problem and the needs of the user.

It is important to have an open mind about what the userneeds.

For example, instead of saying I need a chair to sit downin front of the computer , you can say I need somethingto be comfortable while writing at the computer for fiftyminutes .

The first document of the project is the description ofwhat the user wants. This document is called thespecification .

2 Search for informationBefore we start to resolve the problem, we look forinformation:

How other people have already resolved the sameproblem in the past.

What solutions already exist in the market.

Asking someone who knows more.

Etc.

Information helps us to think of good ideas in the nextstep (brainstorming).


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3 Brainstorm

Brainstorming is a technique to generate solutions to problems.

We brainstorm after specifying the problem and searching for information.

Brainstorming helps us to think of ideas and select a good one.

Think of ideas:

One member of the team writes a list of the ideas from allthe members of the team.

Every member of the team contributes with ideas to solvethe problem.

The ideas must be practical and reasonable. Don t proposeabsurd ideas!

Nobody should criticise other member s ideas; all the ideasgo on the list.

The second document of the project is the list of proposedideas.

Select the best idea:The members of the team discuss the advantages anddisadvantages of all the ideas.

Select the best three ideas by voting.

Draw a sketch of the best ideas and discuss and analysethose ideas further.

Then vote again to select the best idea to solve theproblem. Think if it is easy to design, construct and recycle,and if it is the best solution for the user.

The third document of the project is an explanation of whythe chosen idea was the best.

The third document includes a detailed sketch of the ideaand a description of the product: how it works, whatstructure it has...

1 Do a brainstorm with this specification:The sunlight reflects on the blackboard and it is difficult to see whatthe teacher writes.

The students want to see clearly what the teacher writes on theblackboard.


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4 Plan

This is probably the most difficult step.It is not more important than selectinga good idea but it is more complex.

Now we think about all the tasks thatthe team has to do and all theresources that the team needs.

Time and people are resources.

1st You need to know how much time and how many people you have.

2nd Give tasks and time to each team member.

3rd

Make a calendar with the dates for each part of the project.

The fourth document is a list of tasks for each member and the time for each task.

We can include what materials and tools we need.

5 Design

In this step we define the structure, the shape, the colour

During the design step we define in detail the chosen idea,considering its manufacture, sale, service and recycling.

At this step it is not very difficult to go back tobrainstorming, so maybe you want to think again.

We design for easy manufacture and to satisfy thespecification.

During the design we make a clean, clear and detaileddrawing with the necessary dimensions.

The drawing is in first-angle projection (see Chapter 4:

Orthographic Drawing), with a top view, a front view and aside view.

We specify the necessary materials and tools.

The detailed drawing is the fifth document of the projct.

2 The result of a brainstorm is to make a school bag with wheels:

a) Plan the project. b) Design the school bag.


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6 Construct

We construct our design: measurements, materials, colours

If during the construction we find mistakes in the design, or something that we can t make,or if we see that we can improve the design, then we go back to the design step and changeit.

The problem with changing the design is that nowwe have spent resources (time and materials) thatwill be wasted.

So, there must be a very good reason to makedesign changes (it would be worse not to make thechanges).

Don t forget to write a sixth document with the listof tasks that each member of the team did and howlong each task took, the materials and tools that weused, etc.

This sixth document is a bit like the planningdocument. But instead of a plan, i ts a description ofhow things happened.

7 TestWhen we finish the construction, we test it and see if everything works correctly.

The first time that we test the constructed project it might not work. Dont worry! It is acommon problem amongst great inventors. Look for possible reasons and make changes;then try again.

Sometimes the project doesnt work for simple things: a wire not connected, a piece in thewrong position

Hopefully it will work fine!


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8 Sell

At school we normally dont sell what we construct ,but if we plan to sell the product this is the mostimportant step.

The price doesn t depend on the production costs(you can t sell something at any price you want).

The price depends on what the customer isprepared to pay.

So, you should do the project only if the cost ofmaking it is lower than the expected selling price.

9 - RecycleWhen we finish using the object (and if we designedit with recyclable materials), we can construct otherobjects using the same material.

We can recycle some materials that we use in theworkshop.

For example, we can dismantle some of thecomponents: light bulbs, wires, etc. and put themback in storage.

Also, we can save large pieces of wood to makesmaller pieces in the future.

Recycling helps to save money, protects theenvironment and promotes a more sustainable wayof life.

We put cans, plastic bottles and cartons in theyellow container.


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2.3 Example of the do cu m ents of a pro ject

Specification

A model of tennis racket slips out of tennis players hands because the handle is too

slippery. Sales of this model are low.We want to increase sales.

List of ideas

Reduce the weight of the racket, this reduces the centrifugal force and the racketslips less.

Make the handle to the shape of the hand so that players can hold it better.

Cover the surface of the handle with rubber so that it has a better grip.

Tell players to hold it tightly because it slips.

Chosen solution

Cover the surface of the handle with rubber so that it has a better grip. This is thebest solution because it is cheap and solves the problem well.

Design

A strip of 1m long and 2cm wide rubber tape

wrapped around the handle and glued at bothends.

Manufacture

Costs: rubber tape : 0,35 euros; glue: 0,04 euros;labour: 4 minutes (1,24euros).

1st Glue one end of the tape.

2nd Wrap the tape around the handle . Add glueto the other end and clamp to hold the tape

while the glue sets.3rd Release the racket from the clamp.

Sale

We sell the racket in sports shops.

Recycle

We can melt rubber and mix it with chip stonesto make tarmac.


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Activities

1 When do we search for solutions?

2 What type of things do we do:a) As an individual

b) As part of a team

3 What is important to rememberwhen we specify the need?

4 How do we search forinformation?

5 How do we select the best idea?6 Read this specification:

There is a computer on a table.The person that uses thecomputer has to stand up all thetime and this is very tiring.

Something is needed to make lifemore comfortable for thecomputer user.

a) Do step 2 of the project and writehow you searched for information.

b) Do step 3 of the project. Write thesecond and third documents.

c) Do step 4 of the project and writethe fourth document.

Do step 5. When you design it (fifthdocument), make a good drawing and

additional notes: materials needed,etc.

7 With these specifications, do allthe steps in a project.

We need a container to hold thepens that we bring to school. Thecontainer must:

Be light and easy to carry.

Have a nice appearance.

Be durable and cheap.

8 Look at your daily rubbish.

a) Make a list of things that werecycle (newspapers, plasticbottles...) and another list ofthings that we dont recycle.

b) In which container do we put eachthing? (glass, paper, packaging,rubbish, others).

For example, banana skin goes inthe organic container.

9 What do we put in the yellowcontainer?

10 True or false?a) Projects in technology are

normally done by individualsworking alone.

b) When we plan, we think aboutall the tasks that the team hasto do.

c) The selling price of a product

depends on its productioncosts.


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Chapter 3

DRAWING TOOLS ANDBASIC TECHNIQUES

3.1 Draw ing too ls

RulerThe ruler is a useful tool for schoolwork.

On one side the ruler has a 1:1 metricscale (centimetres and millimetres ).

Sometimes, on the other side the rulerhas a 1:1 imperial scale (inches and

sixteenths of an inch ). This is useful incountries where people use inches as aunit of length.

One inch is approximately two and a halfcentimetres .

Sometimes rulers have holes on the long edge so that you can use it as a compass.

ProtractorThe most common protractor has 180 .

We use protractors to draw angles and tomeasure angles.

To use it, put the vertex of the protractor onthe vertex of the angle and the 0 line of theprotractor on one of the segments of theangle.

The other segment of the angle is under amark in the protractor, which indicates thevalue of the angle . In the drawing it is 30 .


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Pencil and rubberPencils have leads of different hardness in a scale that ranges from soft (B) to hard (H):

Softest 4B , 3B, 2B, B, F, HB, H, 2H, 3H, 4H Hardest

If the lead is soft, the lines will be dark and thick , but we consume the lead quickly.

To obtain dark, thin lines, we use a soft lead and sharpen the pencil often.

We use rubbers to erase what we draw with a pencil.

They also are softer or harder.

Softer rubbers erase better but we also consume them faster.

Compass

With the compass we draw arcs or circles inarchitectural and engineering drawings.

One arm of the compass has a needle . The other arm

has a drafting lead or a pen or a pencil .

First, adjust the width of the compass by placing thecompass needle at the centre of the circle and thelead at a point of the future circle.

Then rotate the compass to draw the circle or arc.

During rotation, lean handle in the direction of themovement.

1 Using a protractor, draw these angles:a) 30 b) 58 c) 10 d) 165

2 Which is the hardness of the leads of your pencils?

3 With the compass, draw these circles:

a) r = 6 cm b) r = 3 cm c) r = 4.6 cm d) r = 2.5 cm


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Triangle rulersWe use the triangle rulers to make simple lines, butalso parallel and perpendicular lines.

There are two types of triangle rulers: the 45 rulerand the 60 ruler.

We also use the corners of the triangle rulers todraw angles: 30 , 45, 60, 90.

Drawing board

In the past, the drawing board was the drawing toolfor engineers and illustrators.

It was good for detailed drawings.

Now we use computers and CAD programs.

CADComputer- Aided Design programs(applications) are programs for technicaldrawing.

There are many examples: TurboCAD,Autocad, Catia

If we combine CAD with finite elementanalysis software (mathematical modell ingprograms) we can calculate, for example:

If the structure will resist forces.

Liquids flow speeds.

4 Draw two parallel lines and two perpendicular lines.

5 Why do you think that engineers now prefer to use CAD programs?6 What is the use of finite element analysis software?


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3.2 Basic drawin g techniq ues

Making parallels

We need two triangle rulers or one triangle ruler and onestraight ruler.

1st Put the triangle ruler on one side of the straight ruler.

2nd Draw a line with another side of the triangle ruler.

3rd Slide the triangle ruler along the straight ruler.

4 th Use the same side of the triangle ruler to draw another line.

Magnificent! We have two parallel lines!

Making perpendicular lines

1st Draw a line with the straight ruler.

2nd Put the triangle ruler on the straight ruler.

3rd Draw another line along the triangle ruler.

This second line is perpendicular to the first one.


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Drawing angles with triangle rulers

We can use the corners of the triangle rulers to draw angles,for example, in a 60 triangle ruler:

The bottom right corner is a 30 angle.

The bottom left corner is a 90 angle.

The top left corner is a 60 angle.

For example, to draw a 60 angle, we draw a line on each sideof the 60 angle corner.

We can combine different corners of the 90 and 60 trianglerulers to draw other angles. For example, with the 60 cornerand the 45 corner we draw a 105 angle.

Drawing a 60 angle with compass and ruler

1st Make a straight line with the ruler . It is a segment of theangle .

2nd Mark a point anywhere on the line. That point is thevertex of the 60 angle .

3rd With the compass, draw an arch of any radius.

The crossing of the arc over the straight line is a second point .

4 th With centre on this second point , draw another arc of thesame radius, cutting the first arc . This makes a third point .

5 th Draw a second straight line , starting at the first point(vertex) and passing through the point where both arcs cross.

The two straight lines are the two segments of a 60 angle .


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Activities

1 http://www.technologystudent.com/designpro/drawdex.htm Look at the drawing equipmentand do the first set of exercises.

2 Using a protractor, draw theseangles:

a) 55 d) 148

b) 26 e ) 31

c) 6 f ) 123

Draw the construction lines thinand the segments of the anglethick.

3 What pencil lead do we need todraw:

a) Dark lines

b) Light lines

c) Dark thin lines

4 If we use a soft rubber, which is:a) The advantage

b) The disadvantage

5 With the compass, draw a circlewith radius:

a) r = 5 cm c) r = 35 mm

b) r = 1.5 cm d) r = 280

mm

6 Using triangle rulers,draw 3 parallel lines.

7 Using triangle rulers,draw 2 perpendicularlines.

8 With triangle rulers, draw a:a) 60 angle c) 105 angle b) 30 angle d) 75 angle

9 http://www.mathopenref.com/constangle60.html Watch the animations on how todraw a 60 angle (click on nextor run).

With compass and ruler, draw a60 angle.

10 http://www.mathopenref.com/constangle60.html

Watch the animations on how todraw 45 and 30 angles and thendraw them on paper.

Dont forget: construction linesthin and angle lines thick!

To draw the 45 angle, we firstdraw a perpendicular line withcompass and ruler.

11 http://www.mathopenref.com/index.html In Plane Geometry click onAngles.

Then click on definition of anangle.

You can make the angle you wantby moving the orange dot . Thename of the angle changes as youmove the dot

a) What are the names of thethree types of angles?

b) Click on interior of an angle.What is the interior of anangle?

12 True or false?a) We use protractors to draw

angles.

b)

The drawing board is a newdrawing tool.


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Chapter 4

ORTHOGRAPHICDRAWING

Drawing is a way to transmit or represent an idea by defining shapes, dimensions, colours

Orthographic drawing is how engineers and architects draw.

4.1 Drafting

Drafting is a bit like sketching; it is a quick andbasic representation of an idea we have in mind.

It is the simplest way to graphically represent anidea.

We use drafting for a first evaluation in a project.

It is hand drawn and has no details.

If we select the draft as the chosen solution for aproject, and if the project is important, then wedraw it.

4.2 Drawing

The drawing must be clean, drawn with a ruler(or a CAD program), contain all necessary details(dimensions, scale, materials) and follow a setof rules (standardization).

If the drawing is bigger or smaller than the realobject, it should indicate the scale.


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4.3 Stand ardizat ion

Standardization is to make something always the same way.

For example, shoe sizes are standardized. We can buy a size38, or a size 39 , or a 40 but we can t buy a 39.763

The disadvantage is that we can t have exact ly our size.

The advantages are that we reduce costs by mass producingand stores have a small stock.

Until the Industrial Revolution thingswere handmade.

Standardization gained importance inthe industrial revolution, when westarted to make many things inproduction lines.

Sometimes we have ideas that we want to tell other people.

Maybe we decide to design something.

Then we draw the idea.

We use standardized rules to make the drawing.

Everybody knows the standardized rules, so when someonesees the drawing he/she understands it.

Thanks to the standardized rules, all theinformation is correctly transmitted.

Then what we designed is constructedcorrectly!


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4.4 First angle pro ject ion

Engineering drawing gives all necessary information to the user, or the manufacturer of thepiece.

Sometimes we can t describe all the information in a single view. To give the necessaryinformation we draw several views in a single drawing.

In first angle projection we draw the three sides of an object as if we are looking directlyat each of them independently.

Look at the drawing of the scale podium.

We put the podium near a corner.

There are three views: a front view , a side viewand a top view .

The front view is what we see if we look straightat the podium.

The side view is what we see if we look at thepodium from the left side.

The top view is what we see if we look at thepodium from the top, like a bird (bird s-eye view).

To put the three views on a single piece of paper, we rotate the views around the axis lines.

1 Why do we draw several views?

2 Which are the views in first angle projection?

3 Draw a simple object in first angle projection.


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Dimensioning:

To dimension i s to indicate the longitudinal measurements of an object .

We indicate all the necessary dimensions on the drawing, sothat the object can be made in the factory, or on theconstruction site, or wherever.

Dont let measurements clutter the drawing!

Don t repeat dimensions , each dimension must be in onlyone view.

If a dimension is not necessary, don t indicate it. Forexample, a dimension is not necessary when it can becalculated from other dimensions .

Use arrowheads showing the exact beginning and end points of your measurements .Keep the arrows away from the drawing. This is easy because we use reference lines (thinlines that go from the object to the arrow ); reference lines don t touch the object.

Dimensions are in mm. If you use another unit, indicate the unit, for example: 30 cm.

Tubes and cylindrical objects in general only need a front view and a side view because thetop view and the front view are identical.

The symbol means that the dimension is a diameter and the symbol R means that it isa radius.

4 Which dimensions do we draw? Why do we draw them?

5 Draw a simple object in first angle projection, with dimensions.

6 How many views we use to draw cylindrical objects? Why?


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Scale:

Scaling means drawing the object bigger or smaller than it really is.

If it is too large to fit in the space you have on the paper, then you need to draw it smaller.

If it is too small to see it, then we can draw it bigger (but not bigger than the paper!).

If we scale down (drawing smaller) we divide all thedimensions by a number, always using the samenumber.

We indicate the scale on the bottom left corner of thepaper with a 1 and then a colon : and then thenumber. For example 1:10 means we will divide byten.

If we are scaling up (drawing bigger than it really is) wemultiply all the dimensions by a number, always using thesame number.

We indicate the scale on the bottom left corner of thepaper, with the number that we are going to use tomultiply, then a colon : and then a 1. For example10:1 means we will multiply by ten.

We always indicate the real dimensions . Weonly change the drawing.

For example, we want to draw a person thatis 180 cm tall on an A4 size paper.

The drawings to the right show the sameperson in a 1:40 scale , then in a 1:80 scale .

The larger the scale , the smaller thedrawing.

We now draw an ant, using a 1:1

scale , a 2:1 scale , a 4:1 scale and a10:1 scale .


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Example of first angle projection:

A podium drawn in first angle projection:

The scale is 1:20. That means that the drawing is twenty times smaller than the dimensionsit indicates.

In the text box we write the information that we think is relevant: the name of the objectdrawn, the materials, the name of the person who draws it, the date when the drawing wasfinished, indications for the manufacturing process i nformation that we can t express inthe drawing.

Sometimes we can write in the views, with a line indicating the part of the object to whichthe indication refers.

All lines must be in black. These drawings have orange , blue and green only to help in theexplanation.


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Activities

1 What is drafting?

2 What is the difference betweendrafting and drawing?

3 What is standardization?4 Name the advantages and

disadvantages of standardization.

5 What happened during theIndustrial Revolution?

6 Why do we have standardizedrules for drawing?

7 Which are the top, front and sideviews?

8 Draw these figures in first angleprojection:

a)

b)

9 http://metal.brightcookie.com/2_draw/draw_t3/htm/draw3_2.htm

Find out how to represent hiddenlines and what symbol we use toindicate that the drawing is in firstangle projection.

10 Which is the top, front and sideviews of each figure:

a)

b)


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11 Draw these figures in first angleprojection:

a)

b)

c)

12 Some more good web pages tolook at if you want to know moreor see a demonstration are:

http://www.btinternet.com/~hognosesam/gcse/page9.html

http://www.technologystudent.com/designpro/ortho1.htm

http://www.tpub.com/content/engineering/14069/css/14069_156.htm

13 What is the scale?

14 Give five examples of things thatyou would scale down to drawthem.

15 Give five examples of things thatyou would scale up to draw them.

16 When would you not use a scaleto draw?

17 Draw yourself infirst angleprojection with a1:20 scale.

18 Measure thedimensions of yourpencil sharpenerand draw it in firstangle projectionusing a 4:1 scale.

19 Measure the dimensions of yourchair and draw it in first angleprojection using a 1:12 scale.

20 True or false?a) Drafting is a complex way to

graphically represent an idea.

b) We use drafting for a firstevaluation in a project.

c) Until the Industrial Revolutionthings were handmade.

d) Standardization is not

important if we make things inproduction lines.

e) Drawing rules arestandardized.

f) We normally use three viewsin first angle projection.

g) If we scale down we multiplyall the dimensions by anumber.

h) To draw an ant, we normallyscale down.


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Chapter 5

PROPERTIES OFMATERIALS

Differentmaterials behave

differently.

Knowing thedifferences helps

us choose thebest material tomake an object.

5.1 Classif ic at ion of m aterialsThere are many ways to classify materials. One of them isto classify them as raw materials and processedmaterials.

Raw materialsThey are those materials that exist in nature and whichwe use as they are: wood, stone, etc.

We cut the trees into logs and the logs into wood planks,but we do not change the wood itself.

Processed materialsWe transform raw materials to make processed materialswith different properties.

For example, we extract iron ore from mines. Iron ore is araw material. We process the iron ore to make steel.

Steel is a processed material, stronger than iron.


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5.2 Prop ert ies of m aterials

Mechanical properties

Elasticity is the ability of a material to change itsshape when we apply forces to it, and to recover itsoriginal shape when the forces stop.

A good example of elastic material is rubber. We canstretch, squeeze, bend or twist it, but when theforce stops it recovers its original shape.

Malleability is the ability of a material to squeezeinto a new shape when it is under compressionforces, and to keep the new shape when the forces

stop.In other words, if you hammer something and itchanges shape and keeps the new shape, it ismalleable.

Metals are malleable. Hot forging is shaping themby hammering them when they are red-hot .

In the old days, blacksmiths forged metals byheating them in a furnace until they were red-hot ,and then hammered them into the desired shape.

Ductility is the ability of a material to stretch into anew shape when it is under pulling forces, and thento keep the new shape when the forces stop.

This property is useful for making wires.

Hardness is the capacity to scratch other materials.

Hard materials scratch softer materials.

For example, diamonds are harder than glass, so you canscratch glass with a diamond. But glass is harder than wood, soyou can scratch wood with glass.

Toughness is the resistance to breaking. It is difficult to breakobjects made of tough materials, even if they suffer repeatedimpacts.

For example, steel is tougher than stone, so we use steel andnot stone for hammer heads.

1 http://www.technologystudent.com/joints/matprop1.htm Read about the properties of materials. Then c lick on PDF FILE -CLICK HERE FOR PRINTABLE EXERCISE, print the exercise page (orcopy it in your notebook) and do the exercises.


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Physical propertiesDensity is a relation between weight and volume.

Imagine we have 1000 litres of air, which has amass of 1 Kg (1).

Then we compress the air with a piston, reducingthe volume to 500 litres (2).

The compressed air is more dense:

Electrical properties

Electrical conductivity is the ability of a material to letelectrons flow through it.

When we want the electricity to flow easily, we useconducting materials.

When we don t want the electricity to flow, we useinsulating materials.

Inside a wire there is copper or aluminium, because theyare good conductors.

The outside of the electrical wire is plastic, because it is aninsulating material.

2 Calculate the density of these materials:a) 2 litres which weigh 15 Kg. b) 5 litres which weigh 13 Kg

3 In electric wires, why do we use:a) Copper b) plastic c) aluminium


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Thermal propertiesThermal conductivity is the ability to let heat flow through amaterial.

For example, heat flows easily through metals, but notthrough wood, ceramic or plastic.

That is why we use metals to make cooking pots and pans, sothat heat from the fire transmits easily to the food.

When cooking pots were made of ceramic, heat wastransmitted slowly and cooking was slow.

Fireplaces are best made of a metallic material because heattransmits well through metal, so the room is warm. Be careful don t touch it!

We use ceramics to make roofs because they are thermalinsulators.

Heat has difficulty passing through the ceramic, so little heatfrom the house escapes to the atmosphere.

Technological properties Mouldability is the ability of a material to fill a mould.

When the material is a liquid we put it in the mould. Whenit becomes solid we take the piece out of the mould.

We can make cakes in a mould. We put the mixture in themould and the mould in the oven. When the cake is readyit has the negative shape of the mould.

Extrudability is the ability of a material to be pushedthrough a hole with the desired shape.

A good example is toothpaste. When you squeeze the tubeyou extrude the paste through the hole.

Aluminium bars and tubes are easily manufactured byextrusion.

4 To build the wall of a house, is it better to use ceramics ormetals? Why?

5 Think and write three examples of moulding.

6 What property is toothpaste a good example of? Why?


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Ecological propertiesToxicity is the capacity of a substance to damagean organism by ingestion, inhalation or skincontact.

The damage depends on the toxicity of thesubstance and on the dose.

The dose is the quantity of a substance or thelength of time of exposure of a person to a toxicsubstance.

Pollution affects the atmosphere and the water.

It is important to use non-toxic materials forobjects that are in contact with people, food orwater.

Some substances are not toxic but they damagethe environment. For example, carbon dioxideproduces the greenhouse effect, but it isn t toxic ifwe breathe it.

Recyclability is the capacity of a material to beused again to make another object.

This is not a property of the material, it dependson how we use the material in the object, therecycling technology available, and if users putthe object in the bin.

For example, if we put glass bottles in the greencontainer, the recycling company melts them in anoven.

With the molten glass we make new bottles.

It is more difficult to make new glass if the old glassis mixed with rubbish.

This property of materials is more important a sthe world gets more populated; there is morewaste and there is less space for landfill sites.

7 The damage caused by a toxic material depends on which two things?Describe them.

8 Search for information about the technology we use to recyclealuminium cans and write a summary.


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Activities

1 Classify these materials as rawmaterials or processed materials:wood, wool, plastic, stone, glass,iron ore, steel, crude oil, clay,bronze, cotton, sand.

2 What properties of materials doyou think that are important for:

a) A suitcase.

b) A dish.

3

Calculate the density of:

a) Steel (14 kilograms occupy 2litres).

b) Pine wood (7 kilograms occupy10 litres).

4 http://www.bbc.co.uk/schools/ks2bitesize/science/materials.shtml

Do the Characte ristics ofmaterials activity f ollowing theinstructions.

Then click on Revision Bite andclick again on Materialproperties. Copy into yournotebook the definitions oftransparent , opaque , waterproof ,strong , flexible , hard , magnetic and conductor .

Go back to the first page and clickon Quiz. Complete the quiz.

5 Describe these materials:(strong/weak, light/heavy, etc.)

a) Paper

b) Cardboard

c) Cork

d) wool

e) Wood

f) Plastic

g) Metal

6 Fibrous materials (wood, forexample) have differentmechanical properties dependingupon the direction of the force.This is because their fibres arealigned in one direction.

Cut two identical pieces of wood(dimensions: 5 mm x 10 mm x 50mm).

Piece A - Fibres across the piece.

Piece B - Fibres along the piece.

Test them to see which one breaksmore easily.

Which is stronger, the fibres or thematerial that bonds the fibres?Explain your answer.

7 What materials do we use to makeelectric wires?

Why?


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Chapter 6

WOOD Wood is a fibrous material.

Fibrous materials are made of fibres (which arerelatively strong) and glue (which is relatively weak).

In the case of wood, the fibres run along the treetrunk, so we can make long wood planks with thestrong fibres running along the plank.

There are three common fibrous materials: fibreglass,carbon fibre and wood.

Of the three, only wood is natural.

If we mash a piece of wood, as in this picture, we can seethe fibres.

Wood comes from trees, but not all the parts of the tree trunk are good quality wood. Thebest parts are the heart wood and the sap wood. They are stronger and more durable.

The cambium is a very thin layer; it is difficult to see. The phloem produces the bark. Thebark is the protective cover of the tree, like skin.


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6 .1 Proper t i es and com pos i t ion of wo od

Fibrous materials have different properties depending on the direction of the force.

Their best properties are with the direction of the fibres, because the fibres are strong and

the glue has no work to do.One advantage of fibrous materials is that if one fibre breaks, the rest stay intact, so thecomponent doesnt break.

Another advantage is that fibres are flexible (because they are very thin).

In the case of wood, the fibres are structural proteins called cellulose, which form the wallsof vegetable cells and which give strength to the plants.

A protein is a long molecule formed by a chain of carbon atoms.

The cells themselves form the relatively light and soft material that bonds the fibres.

6.2 Process ing and t rea tmentof na tural woo d

We first cut the tree trunks into logs.

We transport the logs by lorry or by floating them downrivers to a sawmill where we cut them into wood planks.

Xylophagous insects eat wood.

To protect the wood from these insects, we addinsecticides to the wood planks.

Another protection for wood is the varnish.

Varnish is a hardened resin spread over the surface ofthe component after the final object has beenmanufactured.

It covers the surface of the item and protects againstxylophagous insects, makes the surface harder, andalso is ornamental.

1 Name the parts of the tree trunk.

2 Which parts of the tree trunk are good quality wood?

3 Name two advantages of fibrous materials.

4 What is cellulose?

5 What is varnish?


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6.3 Some com mo nly used types o f woo d

There are as many types of wood as there are types of trees.

Even two trees of the same species produce different wood depending on their growingconditions.

PinePine trees live in climates that arecold or dry, or both, or where thesoil is not fertile.

Pine gives a soft wood which is

easy to carve.Carpenters say that pine wood isthe wood to use because it is ofgood quality, cheap, easy to workwith and durable.

It is the most widely used type ofwood.

Pine comes in several varietiesand all of them make greatfurniture.

It is easy to stain pine wood.

The largest producers of pine wood are Russia, Finland and Sweden.

OakOak trees live in some humid and fresh regions of thenorthern hemisphere.

Oak wood was commonly used for furniture, until its pricerose.

Oak is strong and easy to work.

White oak is better for making furniture because it isresistant to moisture and we can use it for outdoorfurniture.

Also, white oak has a more attractive pattern

than red oak.


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BeechBeech grows in some humid parts of Europeand the northeastern U.S.A.

Beech wood is heavier and harder than pine,but not as heavy or as hard as mahogany orteak.

The wood of the beech tree has a palebrown colour.

FirFir grows in the cold climates of northern Europe,Siberia and Canada.

Fir wood is very soft, and has a red-brown colour.

We use fir in construction and sometimes for furniture.

It isnt expensive.

AshAsh wood is of a very pale brown colour, almost white,and it has a straight grain.

It is easy to work and easy to stain, but ash is gettingharder and harder to find.

Ash is a good substitute for white oak.

MahoganyThe mahogany tree grows in the tropical forests ofCentral and South America and in tropical Africa.

The wood colour is red or brown.

It is one of the best woods for furniture, butmahogany forests are disappearing quickly due to

excessive exploitation, so you shouldnt buymahogany products without guarantee of asustainable origin.

6 Which type of wood is the favourite of carpenters?

7 Which types of wood would you use to make furniture? Why?

8 Which types of wood have a dark colour?

9 For what would you use:a) Fir b) Ash c) Oak d) Pine

10 Should you buy mahogany products?


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6.4 Art i f ic ia l w oo d planks

Sometimes called engineered wood or composite wood, we make artificial wood bygluing wood particles, fibres or veneers.

PlywoodWe make plywood with thin layers (1mm thick) ofwood that we call veneers.

We glue veneers on top of each other, as many asnecessary to obtain the desired thickness.

Alternative veneers have their fibres at right anglesto each other.

We make veneers using whole logs.

Plywood is very resistant to splitting and shearing because the fibres go in two differentdirections.

It has excellent dimensional stability.

It is easy to make large plywood boards wi thout defects such as knots.

FibreboardFibreboard is made of a mixture of glue and wood

fibres and particles.

Is much cheaper than natural wood because it ismade from spare wood bits and saw dust.

Fibreboard is heavier than natural wood because thefibres and glue are compressed to make the board.

Fibreboards do not accept nails or screws because the fibres would crumble.

We use fibreboard to make cheap furniture, but we cover the visible pieces with a veneer togive the furniture the appearance of natural wood.

6.5 Ap pl ica t ion s of natura l and pro cessed w oo d.

Our ancestors used wood more than we do; we nowhave other materials which have replaced it in somecases.

However, some products are still made of wood, such asfloors, roofs, doors, tables, chairs, crates...


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6 .7 Tools and techn iques fo r wo odw ork ing

Basic TechniquesThink and plan before you start to cut wood! This is important because after cutting it isdifficult or impossible to undo the work done.

You should follow three steps:

1st

Make a drawing with dimensions.

In the drawing you define what youare going to make, its shape anddimensions

The drawing also helps you to thinkabout the manufacturing process. Forexample, how you plan to assemblethe different parts made.

2nd

Mark (on the wood) the linesalong which you are going tosaw.

Use a ruler so that the lines havethe correct dimensions.

It is better to use a square ruler.It helps to make the lines parallelor perpendicular.

3rd

Choose carefully the best type of saw to cutyour piece.

Then if everything seems right start tosaw.

Saw carefully to get the piece exactly as youwant it.


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Wood sawsThere are many types of saws, eachdesigned for a specific purpose.

We can classify wood saws depending onthe size of the teeth or the shape of the

blade.

The rip saw has large teeth. We use it to cutalong the fibres.

Large teeth cause more splintering, but it doesnt matter because we are splitting the wood along the fibres.

The cross-cut saw has medium teeth, we use it to cut acrossthe fibres.

The smaller teeth cause less splintering.

The panel saw has small teeth. We use it to cut panels.

The smallest teeth cause the least splintering, in panels we donot want any splintering.

The handsaw is the saw most often used bycarpenters to cut timber, planks, and boards.

The handsaw has a wide blade. There arefiled teeth along one edge of the blade .

There is a handle at one end of the blade .

The blade is made of steel and the handle ismade of wood or plastic.

When we make the blade , we heat the teeth until they are red hot and then we cool themquickly by dipping them in water. This

process is called heat treatment andmakes the steel very hard.

The rest of the blade is not heat-treated because it would become brittle.

Handsaws are good for cross-cutting and for ripping.

17 Why do we plan before we start to cut wood?

18 Which are the three steps we should follow to cut a wood board?

19 Why do we heat treat the teeth of t he blades of the saws?

20 For what do we use the cross -cut saw?


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The coping saw is the saw to cut curves.

The coping saw has a U shaped frame.

The coping saw has a thin blade held in the frameby clamps with butterfly bolts. Sometimes the

clamp is operated by turning the handle.

When you insert a blade in the frame, the teeth should point toward thehandle so that the cutting is done on the pulling stroke rather than onthe pushing stroke.

If you want to make a shape in the middle of a wood board, first drill ahole and then pass the blade through it.

To pass the blade through the hole you obviously have to unclamp itfrom the frame.

The backsaw is the saw we use to makevery straight cuts.

The backsaw has a reinforcement onthe blade, which makes the blade stiff.

The reinforcement is a strip of brass orsteel on the back of the blade.

Hold the wood board on the benchclamp, close to the line along whichyou saw.

The free hand can rest on the reinforcement to help guide the movement of the saw.

During the first strokes, raise the handle slightly, then put it parallel to the wood.

It is not possible to make cuts deeper than the width of the blade with the back saw becausethe reinforcement is thicker than the blade.

The hacksaw is used by metalworkers.You can also use it to cut wood. The small teeth give acleaner cut and a smoother finish.

The frame is rigid to hold the blade firmly in line.

Blade tension is adjusted by turning the butterfly bolt.The blade must be a bit tense.

Han dle

Blade

Frame

butterfly bolt

21 What saw would you use to:a) Cut metal b) cut curves c) cut very straight

22 How deep can the cut be with a backsaw?


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Activities

1 What do we use to protect wood?

2 Which type of wood would you use to make a boat? 3 Name the different parts of a saw. 4 What type of saw would you use to cut across a

wood plank? Why?

5 Practice in the workshop.Materials: a small piece of natural wood, a small piece of plywood, a small piece offibre board and three thick nails.

Hammer a nail through each of the pieces. Then write a report about whathappened in each case.

6 Working in the workshop, hammer a thin nail on a very small piece of natural wood.Then hammer a thick nail.

Is there any splintering? In which case? Write a short report.

7 Construct a modeltable.

To make the legs, use 4 roundbars 100 mm long and 5 mmin diameter.

Use thin plywood to cut thetable board.

Nail the board to the legs.Make sure that the nails arevery thin to avoid splintering.

If you want a more solid construction, you can use woodscrews instead of nails. In this case, to avoid splintering, you

need to drill a hole (thinner than the screw) and thenintroduce the screw along the hole.

8 Put some papers or cardboard for recycling in abucket of water and leave them to soak for at least oneday.

Then mash them thoroughly with your hands.

Using a rod, laminate the paste over a flat surface. Try toobtain an even thickness of 1mm. It is important that thethickness of the whole page is even.

Then let it dry. The result is recycled paper!


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Chapter 7

METALS We often classify metals as ferrous and non-ferrous.Ferrous metals are those that contain iron.

The only two ferrous metals are steel and cast iron, but

we use them a lot because of their low price and theirgood mechanical properties.

There are many non-ferrous metals. Copper, aluminium,nickel and magnesium are some examples.

We usually use them mixed into alloys.

Alloys are a mixture of various metals.

For example, bronze is a mixture of copper with tin, zinc,lead or nickel.

Metals are important materials for us. Historical eraschanged when people started using metals.

The use of metals started in the Middle East, and thecommunities that first learned to obtain and workmetals founded kingdoms and empires.

The first metal to be used was copper.

Later came bronze. Minerals containing copper also oftencontain tin; as both metals melted, they mixed together.

And finally came the Iron Age. Pure iron is a softmaterial, but when a bit of carbon mixes with the molteniron, the result is steel.

Metals were expensive (especially silver and gold).

People used metals to make coins.

Coins helped develop long distance trade.


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7.1 St eel

Steel is a mixture of iron and carbon. Between0.2% and 2% is carbon (C) and all the rest isiron (Fe).

Properties of SteelThe properties of steel depend mainly on thepercentage of carbon that it contains.

They also depend on the type and quantity of the other elements mixed with it.

The properties are influenced by the speed of cooling the steel from liquid to solid.

In the Iron Age, the most important characteristic of steel was that it hardened if it washeated until red-hot and then cooled quickly in water.

Mild steel is steel with less than 0.25% of carbon. It does not harden if cooled in water.

As the percentage of carbon in steel increases, its strength increases. But this also increasesits brittleness, and it becomes less flexible.

The three main properties of steel are that it is:

tough (its difficult to break)

resilient (it can absorb a lot of energy on impact)

malleable (we can compress it into the shape we want, especially when its hot )

7.2 Cast Iro n

Cast iron is a mixture of iron and carbon.Between 2% and 6% is carbon (C) and all therest is iron (Fe).

Properties of cast ironThe properties of cast iron vary depending onthe percentage of carbon it contains. But in

general, when compared to steel, cast iron is:resistant to vibration (we can make itvibrate a lot and it does not break)

resistant to compression (when weapply compression forces, it squeezesvery little)

less flexible

less resistant to tensional forces

cheaper than steel

1 How do we classify metals?2 What is an alloy?3 Name three properties of steel.4 What is cast iron?

5 Which has a higher content ofcarbon, steel or cast iron?


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7.3 Produ ct ion of cas t i ron and s teel

The blast furnaceMiners extract iron ore from the earth. Ore is a mineral in which there is a mixture of rockand iron oxide (Fe2 O3).

In the blast furnace the iron is separated from the oxygen , transforming the iron oxide intopure iron (a bit of carbon dilutes in the iron ).

We put iron ore , coal and air in theblast furnace.

The coal burns with the air .

The carbon atom in the coal would

like to burn forming a molecule withtwo atoms of oxygen from the air tomake a carbon dioxide (CO2)molecule.

But there is not enough air , so eachcarbon atom only finds one oxygen atom, forming carbon monoxide (CO).

Carbon monoxide , if possible, wouldlike to find more oxygen to becomecarbon dioxide , which would reallymake the carbon happy !

Hot gases go up, so the hot carbonmonoxide gases (1300C) go up.

On the way up, the hot carbon monoxide sees the oxygen of the iron oxide (Fe2 O3) and, asit is very interested in more oxygen , takes the oxygen from the iron oxide , becoming

carbon dioxide and leaving pure iron .

Hurray!!!

We have de-oxydized the iron!!!

The molten pig iron and the slag exit from the bottom.


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The pig iron is the pure iron (Fe) with a bit of carbon(C) (because there was too much coal and too little air ).

The slag is iron ore without the iron. In other words, it isthe mineral from which the iron has been taken.

Processing the pig iron into steel orcast ironTo produce steel and cast iron we reduce the amount of carbon in the pig iron .

There are many ways to do this. The most common way is to mix the pig iron with oxidatedscrap steel at melting temperatures.

The oxidated iron in the scrap steel is iron combined with oxygen (Fe2O3).

The pig iron contains Fe and C.

The oxygen of the iron oxide combines with the carbon, forming carbon dioxide (CO2) whichis a gas and goes to the atmosphere.

7.4 Spec ial st eels

The properties of steel depend on the percentage of carbon, on the way we cool it, and onsmall percentages of other metals that we add to the steel, making steel alloys that we callspecial steels.

Stainless steel

We add chromium to the steel (until 10% of the steel ischromium)

Chromium combines with oxygen, but forms a really thinlayer of oxide on the surface of the steel known as apassive layer.

The passive layer stops further oxidation or other forms ofcorrosion of the material.

Sometimes we make stainless steel by adding nickelinstead of chromium. Nickel also makes a passive layer.


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7.5 Non-ferrou s meta ls and thei r pro per t ies

Non-ferrous metals are those that are not iron and do not contain iron.

There are many non-ferrous metals, but we use them for specific applications when theirspecific properties are important. This is because their price is normally higher than that ofsteel.

CopperCopper is the third best electrical conductor, and it is very ductile. For these two reasons it isa good material for electric wires.

It is also a very good thermal conductor, so we also use it for heat exchangers in boilers.

We also use it for pipes in plumbing. In the past, water pipes were made of lead, but

scientists found that lead was toxic.

AluminiumAluminium is a light metal. It is resistant to rustbecause it forms a passive layer, like stainless steel.These are the two main reasons for almost all of itsapplications.

It is the second best electrical conductor. This thirdproperty is the reason we use it for the wires of theelectric power grid.

TinTin is very resistant to corrosion and this property makes it suitable for coating other metals.For example, steel cans are sometimes coated with tin on the inside.

It has a nice shine, like silver, so it is often used in decoration.

It melts at a low temperature for a metal (232 C), so it is the material used for weldingelectronic components.

Titanium Titanium is lightweight and very resistant to corrosion.

It is abundant in nature, but is not concentrated in a mineral so it isexpensive to extract.

It is almost as strong as steel.

It is normally used for structural elements where it is worthincreasing the cost to reduce the weight.

Because it is lightweight and because it remains strong in a verywide range of temperatures, it is used for spacecraft (outer space isvery cold).


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7.6 Non -ferrous al loys and thei r pro per t ies

An alloy is a mixture of two or more metals.

The alloy has different properties from the metalsthat are in it.

Aluminium - copper

Adding a bit of copper to aluminium improves itsmechanical properties. It is good for structuralcomponents.

Adding copper also lowers its melting point, so youcan manufacture by casting.

We use aluminium alloys to make wheels, bicycleframes, airplanes, cooking pots...

Bronze

Bronze is an alloy of about 88% copper and about12% tin.

It is very resistant to corrosion.

It has little metal-on-metal friction, so we use bronzein mechanisms when it is not possible or convenientto have grease or oil for lubrication.

We also use bronze for statues because it is easy tocast and weld and has a nice appearance.

6 What is a non -ferrous metal? 7 Which metal would you use to make electric wires? Why?8 Name two light non-ferrous metals.9 Name four uses for aluminium.10 Which metal would you use to make a spacecraft? Why?11 What is an alloy?12 To make an alloy wheel, would you use an aluminium-copper alloy?

Why?

13 To make statues, which alloy would you use? Why?


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7.7 MetalworkingMetalworking is the process of working with metals to give them shape.

CastingWe heat up the metal until it is liquid, then we put the liquidmetal into a mould. We also call this process moulding .

When the metal is cold (and solid), we take the metalcomponent out of the mould.

Hot formingWhen the metal is hot it is easy to change its shape.

Extrusion

Extrusion is a technique to push hot metal through a hole with a shape. After passingthrough the hole the metal has the negative shape of the hole.

Forging

Forging is a technique to change the shape of the hot metal by repeated impacts, normallyhammering.

MachiningAlso called cutting, we cut the metal when it is cold.

DrillingDrilling metal is harder than drilling wood. We normallyuse a fixed vertical drill like the one in the picture.

The tip of drills that cut metal have a triangular tip. Thetip has two sharp and hardened cutting edges.

Filing

We file metal components to give them a smoothsurface.

WeldingWe put two metal pieces together and we heat the place they touch until they melttogether. The molten metal of both pieces mix and when the metal cools it is one piece.

Another technique is to put liquid metal between two solid pieces.

14 In which metal working processes is it necessary to have the metal liquid? Why?15 In which metal working process would you use:

a) A hammer c) A hole with the negative shape of the final productb) A mould d) A metal file

16 Which are the two welding techniques?17 Which are the two techniques to weld metals?


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Activities

1 List, in chronological order, thefirst metals used.

2 True or false? a) Cast iron is more resistant to

vibration than steel.b) Steel is more flexible than cast

iron.c) Steel is cheaper than cast iron.d) Steel is more resistant to

tensional forces than cast iron.

3 What isiron ore?

4 What do weput in ablast furnace?

5 What does the carbon atom formfirst in the blast furnace, CO orCO2? Why?

6 How does the carbon monoxide inthe blast furnace become carbondioxide?

7 What things exit the blastfurnace?

8 What is pig iron? 9 What do we make with the pig

iron?

10

How do we reduce the percentageof carbon (C) in the pig iron?

11 What is the difference betweensteel and cast iron?

12 http://www.bbc.co.uk/history/british/victorians/launch_ani_blast_furnace.shtml There is an animation that showshow a blast furnace to producespig iron.Click on Launch the animation.

Click on start and watch how thecoke (special coal for steel

production), the iron ore and theair go in. Also how the slag andthe pig iron exit.Click on Build It. A virtualteacher asks you questions. Withevery right answer you construct apart of the blast furnace.Continue with the activity untilyou construct the furnace.

13 The properties of steel depend onwhat three things?

14 Why do we add chromium tosteel?

15 Which metal would you use tomake: a) Spacecraftb) Decorationc) Water pipesd) Bicycle

frames

16 Name three properties ofaluminium.

17 What happens if we add a bit ofcopper to aluminium?

18 To make a mechanism withoutgrease or oil, which alloy wouldyou use? Why?

19 Which alloy would you use tomake: a) Structural componentsb) Statues

20 Search for information to find outthe properties of silver and write aparagraph about them.

21 Imagine a world without metals.Describe how you think it wouldbe.


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Chapter 8

STRUCTURESA structure is a group of elements united to support aload with stability.

The structure maintains the shape of things under theforce of gravity, the force of wind, or any other force.

For example, humans have a skeleton, bicycles have aframe, houses have columns , beams and a roof .

8.1 Types of s t ruc tures

Frame structures

The frame structure is the most common type of structure.

These structures have long elements (bars, tubes...) joined to each other at the ends.

The elements of frame structures are made of strong materials.

The space between the elements is empty space.

A bicycle frame supports the load that it carries on the seat.

The elements in the bicycles frame are the aluminium tubes; the unions are the aluminiumwelding, the nuts and bolts...

Advantages of frame structures: they arerelatively easy to design and build,inexpensive to manufacture, lightweightand do not require much material.

Disadvantages: They are not good for verybig loads or strong impacts.


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Shell structures

Shell structures are made of a thin outer layer of materialaround a volume. That volume can be empty space or containsomething with no structural relevance.

The shell keeps the shape and supports the loads.

The shell can be thin because the forces are spread throughoutthe whole structure, dissipating the load all over the shell.

There are many examples of natural shell structures: eggs,shellfish

There are also many examples of artificial shell structures:cardboard boxes, bottles, balloons, cars, aero planes

ArchThe Romans invented the arch.

There are many types, but the semicircular arch, which was theRoman arch, is the most common.

In Roman times, arches were made of stones. The stone at thevery top is called the keystone .

Its own weight is the main load.

The geometry of the arch displaces the forces to the sides, so that

there is a large free space under the arch.Arches are good for bridges because the large space underneathcan span a river or other obstacle.

Mix and Match Very often, we combine different types of structures into a morecomplex structure.

For example, houses have brick walls (mass structures), columnsand beams (elements of a frame structure), etc.

1 What happens if something doesnt have a struct ure?

2 Give two examples of elements of a frame structure.

3 Define: a) Element b) Union c) Load

4 In a shell structure, what supports the loads?

5 What is the key stone?

6 What does the geometry of the arch do to the forces?


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Mass structures

Mass structures are a thick lump of low-qualitymaterial.

To make mass structures we pile up materialsinto a shape or design.

- Examples of natural mass structures aremountains and coral reefs.

- Examples of man-made mass structures aresandcastles, dams, load-bearing walls (walls thatsupport the weight of the building).

Advantages: the structure is held in place by its own weight; losing small parts haslittle effect on the overall strength of the structure.

Disadvantages: heavy; needs a lot of material; and occupies large amounts of space.

Suspension structures

A suspension structure holds an element(often a beam ) by cables that are held fromthe top of a tall column.

The space (distance) between one column and

the next is called the span . This type ofstructure has the longest span of all structures.

Because of this, suspension structures areoften best for bridges that cover big rivers oreven small parts of the sea.

Advantage: good for covering a very large span .

Disadvantage: expensive to build.


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8.2 Struc tural elem ents

An element is the simplest part of the whole.

In a structure, we calculate the forces for

every element and we design theelement (i.e. beam or column) tosupport them.

The foundation is an element united tothe ground by friction.

The foundation is also united to thecolumn by friction.

The column is another element, unitedto the foundation and to the primarybeams .

The beams and the column are united bywelding if they are metallic.

In some cases the beam is laid on thecolumn (united by gravity).

8.3 Types of un ion s

The structural elements must be united to each other.

The structure is often united to the floor/ground.

Permanent unions

These are for structures that we dont need to disassemble.

Examples: welding, rivets, glue

Non-permanent unionsWith non-permanent unions we can assemble and disassemble theelements of the structure.

Technology 1º & 2º ESO

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Transcript of Technology 1º & 2º ESO