HOW TO DESIGNAND MAKE

AUTOMATAROBERT ADDAMS

CRAFT EDUCATION

22

Published by Craft Education, 8 Verona Avenue, Southbourne, Bournemouth, Dorset. BH6 3JW

Web Site: http://www.automata.co.ukThe web site is an educational tool available to everyone Worldwide,

as well as providing general information it also supplements parts of the book.

First published in 2001

Second edition 2002

Copyright © 2001 Craft Education

ISBN 0-9540596-0-3

All rights reserved

The right of Robert Addams to be identified as the author and illustrator of this work has been asserted by him in accordance with

the Copyright, Designs and Patents Act, 1988

Printed in the United Kingdom

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This book is dedicated with grateful thanks to my family, Beverley, Toby, Oliver and Dominic, who put up with so much during the writing andproduction. Also, special thanks to Selina Gamble and Ian Puttuck who had the task of proof reading and unralveling my transcripts.

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CONTENTSINTRODUCTION 6AUTOMATA, THE NATIONAL 7CURRICULUM AND EDUCATIONMAKING A START 7BASIC ENGINEERING PRINCIPLES

1) CAMS 82) CRANKS 163) GEARS 214) RATCHETS 315) PULLEYS 356) LINKAGES 397) BEARINGS, SHAFTS 42

FRICTION & LUBRICANTS8) DRIVES 439) LEVERS 45

10) SPRINGS 4811) FREE MOVEMENT 49

THE DESIGN PROCESS 51

DESIGN AND CONSTRUCTION 56

AUTOMATA FOR YOUNGER PEOPLE 64

TOOLS AND EQUIPMENT 70

CONSTRUCTION 74

1) WORKING WITH METALS 76

2) GLUING AND STICKING 77

3) SOLDERING 78

SUMMING UP 79

INDEX 80

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INTRODUCTIONThis book is intended as an overview to themechanical principles behind automata, aswell as guiding the reader through the designprocess to make successful, excitingautomata. The book also looks atconstruction methods, materials and usefultools.The primary aim of this book is to provideboth a stimulating project base for teachersdelivering Design and Technology at levels1, 2, 3 & 4, and help with lesson planning forthe National Curriculum. Sections of the bookcan be photocopied and used as handouts forstudents.In essence the book should provide astimulating resource for teachers who canthen disseminate the information to theirstudents in the way they feel is most effective.

Automata are fascinating mechanical marvelsthat utilise a wide range of the mechanicalprocesses found in modern machinery.Designing and making Automata covers arange of skills and processes from Art,Engineering and Maths through to craft skillsinvolving card, wood and metal. It is aninvolving process that has a lot of potential forstimulating the imagination of students andproviding a fun, practical learning platform.

Design and Technology in the NationalCurriculum provides a wide scope for theteacher to explore. The designing and makingof Automata lends itself extremely well to thissubject, encompassing all of the major criteriathat need to be covered. Importantly, it allowsthis to be done in a fun and stimulating way.Many teachers already set projects based onautomata and this book will be a useful guidefor expanding upon this. It also provides acomprehensive look at all aspects ofautomata making, as well as suggesting freshand exciting ideas for inclusion into lessons.“How to Design and Make Automata” fullycovers all aspects of the mechanical, designand construction processes, from simple tocomplex automata. It caters for all studentabilities and skill levels and gives valuableadvice on the design stage. As well asproviding a sound basis from which toevaluate the work.

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THE NATIONAL CURRICULUM MAKING A STARTEvery child in the UK has to undertake someform of Design and Technology activity. Thedesign and making of automata is a great wayof meeting the curriculum requirements.It encompasses all the elements of Key stages1, 2 ,3 and 4. Designing and making automatais a very wide topic, which covers skills not onlyin Design but Art, Maths and English. It can beused to help children understand more aboutthe machines that surround them. In education terms this book is designed to be aguide rather than offering prescriptive, pre-packaged course work, and to give practicaladvice as well as suggestions and ideas to beincluded into the lessons. The A4 format can beeasily photocopied for use as handouts or wallcharts. The design process has been coveredin detail, in order to meet the basis of Designand Technology curriculum requirements.Primary and junior schools may need to bemore resourceful when making automata, if youdo not have access to machinery or woodworking facilities, alternatives have beenexplored in most sections.A number of patterns have been included at theweb site, www.automata.co.uk, which youmay find useful as a practical introduction toautomata, or for inclusion into your ownprojects.

Although aimed at teachers and students thisbook will be of great benefit to anybodyinterested in making Automata or any othermechanical device, sculpture or toy. If youare not involved in education, parts of thedesign process can be tackled in a lessstructured way, without the need to beaccountable to an assessor.The book is broken down into logicalsequences, starting off with mechanisms.You will need to study this section first as itunderpins all the concepts and principlesneeded to make any automata or mechanicaldevice. It should also help to give you ideasfor your own projects, but feel free to copy oradapt any of the examples in the book.Any creative work involves challenges,difficulties, triumphs, tragedies and rewards.Making automata will offer these inabundance but do not lose sight of the needto keep it a fun and enjoyable process. Donot expect to start and finish in a day, you willsoon find out just how long it takes to makean automata, so give your self plenty of timeand be prepared for things to go wrong. Takeheart though, the more you make, the betteryou will become and the easier and fastereverything will come together.

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CAMSCams act like small computers, storinginformation that can be turned intomovement. They can be very simple orcomplex and the only limitation is their size.

The basic principle of the Cam is to turn acircular motion into a linear one. This isreferred to as reciprocating movement.

In automata the cam is very useful, and isprobably the most commonly usedmechanical action. As you will see, the Camis simple to make and very versatile.

Cams normally work in conjunction with a"Cam Follower". As the name implies thisfollows the movement of the cam andtransfers the movement to the working area.The cam follower is normally a rod made ofrigid material such as wood or metal, which issupported by a shaft that limits the movementand direction. The cam follower is designedwith a smooth end that can easily follow thecam’s movement. This is a very important asthe Cam and Follower will jam if not properlydesigned.

This cam is turning a circular motion into an up and down one. This is referred to asreciprocating motion. As you can see in stages 1-5, the cam follower steadily drops beforerising up again. The whole process repeats as long as the cam keeps rotating clockwise.

1 2 3 4 5

This block supports the cam follower andstops it from wobbling from side to side. Thishelps the push rod to only move up and down.In order for the Follower to rise and fall withoutjamming it is important to make this blockfairly thick and reasonably close to the cam.

WORKING AREA: Thisend delivers the power in the

form of an up anddown motion.

SUPPORT Or Cam shaft

CAM FOLLOWER

CAM

PUSH ROD

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CAMS

In order to design a cam you need to knowwhat you want it to do. It may have just one orseveral movements per revolution.Cams turn on a shaft and so need to be offsetto create movement. If you have a circle withthe shaft running through its centre thennothing happens. However, if you offset it youcan create a mechanism that can lift. Withthis lift you can create many marvellousautomata.

A circle with a shaftrunning through itscentre will simply turnand produce no lift.

It is very simple to calculate the amount of liftby simply taking the measurement from thecentre of the drive shaft to the lowest point ofthe cam and subtracting this from themeasurement to the highest point from thecentre of the shaft. This calculation will givethe amount of lift the cam will produce.

This cam produces a smoothuplift which suddenly dropsdown. It is often referred toas a snail cam because of itsshape or contour. This camcan only work in one direction. If you turn itthe other way the cam follower would jam.You need to bear this in mind when you aredesigning cams.

This cam produces severalshort up and downmovements from onerevolution.

This cam producesthree very distinct

movements from one revolution.

You can combine as manymovements as your cam will allow.Remember that the cam followerhas to work smoothly. If you tryto make it do too much ormake the contours toosteep such, as thisone on the right, it willjam. The cam followerscan only move on gentlecurves. Make them too tightand you will have problems!

Offset the centre andyou have made a cam.

The cam follower haslifted by this amount. Sothe more you off set thecam, the greater theamount of lift youproduce.

15 - 5 = 10

This simple equation will enable you to workout how much lift a cam will give. Later on wewill come back to this formula to accuratelywork out the lift of any given cam.

15

5

Different types of cam

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THE DROP CAMIf you dip below the circumference of the circlethen the cam follower drops, hence the termdrop cam. You can calculate the drop of the cam bymeasuring from the lowest point of the drop tothe circumference.A very popular form of drop cam is called thesnail cam. This has a sudden drop that slowlyrises to the next drop point. This cam is used alot in automata and is a blend of both drop andlobe cam.

CAMS

The lobed and drop cams arebased on a concentric circlewith the drive shaft runningthrough the centre. Obviously,without lobe or drop, this camwill not produce any effect onthe cam follower.

THE LOBED CAMIf you raise part of the circumference, youproduce a lobe, hence the name lobed cam.This will lift the cam follower by the maximumheight from the tip of the lobe to thecircumference of the circle. When the camfollower returns to the circle it will pause andthis is referred to as the dwell angle. You canproduce a pause or dwell angle on top of thelobe if you design it properly.

A lobe refers to any part of thecircumference raised above thebase diameter of the cam.

The distance from thecircumference of thecam to the highestpoint of the lobe willdetermine how muchlift it will produce. Inthis example the camfollower will smoothlyrise to12mm beforedropping.

When the cam follower is not beinglifted, that part of the cam isreferred to as the dwell angle. Thiswill produce a pause in the automataaction.

The camfollower is

rising

The camfollower is at itshighest point

The camfollower is

descending

The cam follower isstationary as it follows the

circumference or dwell angle

A “Drop” refers to any surface that goesbelow the circumference of the cam.

The distance from thecircumference of the camto the lowest point of thedrop will determine theamount of travel. In thisexample the cam followerwill smoothly drop to12mm, before rising.

This snail cam both dropsand lifts. You could evenadd some extra lobes anddrops on the cam face.

12 mm

LOBED AND DROP CAMSFrom the basic round cam you can increasethe diameter across one axis, to produce anegg-shaped, or “Lobed”, cam. Alternatively,you can create a recessed area that dropsbelow the circumference of the circle,producing a “Drop” cam. You can, ofcourse, combine these two elements in acam, which is why they are so versatile.

12mm

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SPECIALITY CAMS FOR AUTOMATAThe cams covered so far are fairly simple. They are the sort that can be found in many everyday machines like car engines andwashing machines, but there are a range of more unusual cams that can be used for added versatility or sophistication when makingautomata. They are, in themselves, very simple but may require more skill when making them.

The self-conjugate cam works at high speedand has an unusual motion, producing both upand down as well as side to side movement.

The skew cam has a thin plate which isattached to the drive shaft at an angle. As itturns, it contacts a forked lever which it turnsfrom side to side. This twists a vertical rod andso transfers the movement.

An offset cam not only moves things up anddown but also in a circular motion. You mustmake sure that the cam contacts the camshaft drive plate either side of the cam shaft.If it contacts directly underneath then it willonly lift. Offsetting 2 cams either sideproduces movement inopposite directions. Thisthen gives you both up anddown as well as a side toside movement.

In this example the cam hasbeen stretched out into a line.Instead of turning the cammoves back and forth, whichcauses the cam follower togently rise up and down.

The skew cam is in effect a wobbly plate andturns a circular motion into a side to side one.

The man in thisautomata shakeshis head from sideto side. There is asmall amount oflift but it is notreally noticeable.

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CAMS FOR AUTOMATA

FROG - USING A SINGLE LOBE CAM.This will produce a single, smooth up anddown movement.

CATERPILLAR - USING MULTIPLECONCENTRIC CAMS.Each cam is slightly offset from the precedingone. This gives a smooth, wriggling motion.

AEROPLANE - USING TWIN LOBE CAMS.The two cams are at opposite ends and areset at 180o to each other. This causes theplane to dip up and down from nose to tail..

The examples below show how you can use the cam when it comes to making automata. The key point to make in mechanical terms isthat it produces a linear movement from a rotating input and you can create an enormous amount of things with this. The illustrationsbelow show a range of uses for simple one lobe cams.

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CAMS FOR AUTOMATACams can often have more than one lobe. Multiple lobe cams produce even more diverse and exciting movement.

This cam has five lobes, one of which ishigher than the rest. The cat will make foursmall jumps and then one big one.

This pointed triangle will produce threeequal sharp movements in one revolution,snapping the jaws open and shut.

This drop or snail cam allows the hammerto rise smoothly and then suddenly drop.

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CAMS MATERIALSWhen you have designed your cam, you willhave to think about how you are going tomake it. The ideal material should be softenough to cut easily but strong enough not tobreak or wear out too quickly. Cardboard, forexample, can be a useful material. Severalthinner sheets can be cut to size and thenstuck together (or “laminated”) using woodglue or PVA. This produces a very strong anddurable cam. Alternatively you can use thickcorrugated cardboard.

MDF (medium density fibre board) can bebought in various thicknesses. 4-6 mm worksbest and it is fairly easy to cut and thenshaped with sand paper. The dust is harmfulto breath in, always use a mask if workingwith MDF. We don’t advise you let childrenwork with it.

Thin pine wood (again 4-6 mm) is anothereffective material to work with. It takes a littlemore time to cut and shape but is verydurable, works well and looks good.

The later chapter on materials and tools goesinto more detail.

DESIGN TIPSWhen designing a cam, think about itcreating a performance or event in onerevolution. This can be simple orcomplex. Remember to use gentlecurves to allow the cam follower tooperate smoothly. If you design a camthat produces several events you mayneed to make it bigger.

The designer of this camwanted to create 4 up anddown movements perrevolution. This design wouldprobably jam and notfunction properly.

This bigger cam will do the same job,

but now the cam follower is able to follow thecontours as they are more gradual. It will stillproduce 4 varying up and down movementsper revolution.

CARD

MDF

PINE

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MAKING AND MEASURINGThis final section shows you how to use asimple mathematical formula to work out thelift for concentric cams.

The concentric cam, is a circle with an offsetcentre. By offsetting the centre we are able toproduce the lift and the further you moveaway from the centre point the greater theamount of lift you produce. Do not overdothings, it is better to make a larger cam thatrises gently than a small one that rises rapidly.They will both do the same job but the smallercam is more likely to jam.

TWIST AND TURNINGA rather annoying characteristic of the cam isthat it produces a turning motion on the pushrod. This may only be very slight but cancause problems. The leaping frog for instanceslowly turns round as it moves up and down,which in some instances could be a problem.To eliminate the turning affect you can eitherbuild stops to prevent turning, (this can affectthe overall look of your automata) or anothermethod is to use square tube and rod whichare readily available in brass, copper andplastic.These hold the push rod firmly in placeand eliminate any turning action.

CAMS

Both cams lift by the same amount but thelarger circumference of the bigger cam willproduce a much smoother lift. As a roughguide, try to make the biggest cam that willcomfortably fit into your Automata.

When making Automata, you need to workthings out fairly accurately. This applies tocams when you need to produce lift to aspecific height. The following formula is verysimple and shows you how to quickly andaccurately work out the centre point for thedrive shaft.

For every millimetre that you move away fromthe centre point, you must double this figure,in order to calculate the amount of liftgenerated by the cam.

In this example you can see that the centrepoint has been moved up by 6 mm which willproduce a lift of 12mm

You can confirm this by using the formula welooked at earlier by subtracting the twodistances from the new centre point

18mm - 6mm = 12mmIt’s as simple as that. Remember you onlyhave to accurately locate the centre point.The actual diameter of the drive shaft isnot important.

6mm

24mm18mm

6mm

newcentrepoint

A small pin can beplaced behind thefrog which will stop itturning. Usually onlyone stop is needed asthe motion is in onedirection.

A square tube and rod eliminates any twistingaction.

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Cranks are similar to simple cams. Theyconvert circular movement into a reciprocalone (up and down motion) or vice versa.There are, however, some fundamentaldifferences. Firstly, cranks only ever work in acircular motion and they only have one driveaction per revolution. That said, when itcomes to automata you can make someamazing machines based on the crank.

CRANKS

The crank has many uses. Firstly it is oftenthe driving mechanism for hand operatedautomata. It is important to support the crankwith some type of bearing. In this case it isthe sides of the box that provide the support.(We will be looking at bearings and shafts ina later chapter).

The con rod or slider islinked to the crank pinand transfers themovement

The crank shaft both supports thecrank and rotates it.

Crank Pin

The amount of up and down movement is called the throw of a crank,and is measured by the size of the circle it scribes when turning, which will be twice the diameter.

This crank will have athrow of 4cm.2 + 2 = 4

Although the crank only works in a circularmotion, its drive can be made to go from side toside as well as up and down (which can’t beeasily achieved with a cam) and when appliedto Automata you can create some very specialeffects.Another big advantage with the crank is havingpower on both the upward and return strokes.This means you don’t have to rely on gravity,which can be a problem with cams.

Thisdiagramshows how thecrank linkage or slidercan be made to give a side toside movement. By adjusting theheight from the opening you can increaseor decrease the amount of sidewaysmovement. Adjusting the size or aperture ofthe opening will also have an affect on theamount of lateral movement. As with manyaspects of Automata you will find that trial anderror play a big part in making things work.

2cm

2cm

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THE SCOTCH YOKEA variation of the crank is the scotch yoke.This is more complex to make, but has anumber of advantages.

CRANKS

As the crank rotates so the sliding con rod willbe powered vertically up and down. TheScotch Yoke was used a lot in steam engines.Because of the design there is no lateralmovement. If you want a simple reciprocatingmovement which is constantly powered andhas no lateral play, then this is the perfectsolution. The throw of the crank is used to determinethe amount of movement and must be lessthan the sliding mechanism on the con rod.

As the drive shaft rotates so the crank, which is offset, pushes the sliding con rod up and thenpulls it down. Because the crank is able to slide back and forth, the con rod can be restrainedand will only move in a vertical path.

The sliding con rod is held in position bysupports placed either side. There should bebe just enough room to let the slider move.The supports are attached to the main shaftand rotate with it.

CRANK PIN

SLIDING CON ROD

SIDE SUPPORTS

Here,a scotch yokeis used to bothpush and pull thepig. As it rises up anddown, fixed linkages makethe wings move in the oppositedirection of the pig and it looks like it is flying.

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THE ECCENTRIC CRANKThis next crank is known as the EccentricCrank. The crank pin is greatly enlarged andsits within the con rod (or eccentric strap).This crank will produce up and down as wellas side to side movement. It also uses astraight drive shaft and is therefore strongerand easier to make. It is necessary to supportthe con rod either side to stop it falling off thecrank pin. There only needs to be two circlesattached to the main shaft.The distance from the centre of the shaft tothe highest point of the crank pin willdetermine the throw. When constructed this isquite an elegant looking mechanism its realadvantages over the traditional crank is thestraight drive shaft, vertical travel and abilityto fit into tight spaces.

DRIVE SHAFT

ENLARGED CRANKPIN

CON ROD

SUPPORT BLOCK

The concentric crank again raises and lowers the push rod as it rotates. As the push rod is freeto rotate it can, like the scotch yoke, constrain the push rod to a vertical path or with a wideropening in the support block be used to also produce a side to side motion.

The side supports are attached to the driveshaft constraining the crank pin. This stops anylateral movement.

DRIVE SHAFT

The eccentric crank is usedto push the cleaning lady

up and forwards, thenback again. She ispivoted at the kneesand her arms are

pinned and free moving. Asthe crank is turned sheappears to scrub back andforwards furiously on thefloor.This crank is excellent forproviding a slightly irregular

movement when notconstrained.

ENLARGED CRANKPIN

CRANKS

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The fast return actuator crank.This next crank is similar to the scotch yoke,in that it, too, is a positive drive mechanism.The main difference being that this crank hasa pivoting con rod. The further you place thecrank pin from the pivot the less lift itgenerates. You can also construct this crankwith the crank pin under the con rod so thatgravity pulls it down.

CRANKS

The crank pin lifts the con rod and eithergravity or some other form of force (ie. a spring)then pulls it back down.

Fixed pivot pin. This constrains thepivoting con rod, allowing it to onlymove up and down.

A POSITIVE DRIVE FASTACTUATION RETURN CRANK.

The crank pin constantlypowers the con rod.

The con rod pivots at one end and produces driveat the other.

This rod is also free to pivot and connects and transmits the power.

DRIVE SHAFT

Thisautomata usestwo positive drive returncranks that are offset and connected tolinkages which in turn move the arms upand down. Turn the handle and the bakerfuriously chops the bread.

1

2

3

4

A positive drive fast actuationreturn crank in action.

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CRANKS

This now has a side to sideoutput.

Up & Down input

Input

Output

In this example the action is reversed, soas the input pushes, the output pulls.

THE BELL CRANKThis very useful little device, so-namedbecause its action resembles a tolling bell. Itoperates in quite an unusual way, althoughtermed a crank it works in a reciprocatingmovement, not a circular one.It is very effective for changing the directionof movement. In the example below, as theinput moves up and down, the output movesfrom side to side.

STRINGS ATTACHEDMost con rods are made of resistant materialsuch as metal or wood. A great alternative incertain circumstances is nylon cord. Thismethod works best if you need to pull ratherthan push. The automata below and oppositerely on gravity as a secondary moving force.

The policeman’s truncheon is pulled up by anylon thread as the crank reaches its lowestpoint. When the thread slackens, gravity thenpulls it down.

The two pieces of the heart fall apart helpedby gravity and a weighted arrow. As the crankturns, it pulls the nylon cord which, in turn,pulls the two halves back together.

Pivot point

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GEARSTHE WAY GEARS WORKGears are very versatile and can helpproduce a range of movements that can beused to control the speed of action.In basic terms, gears are comparable tocontinuously applied levers; as one tooth isengaging, another is disengaging. Theamount of teeth on each gear wheel affectsthe action on the gear wheel it engages ormeshes with. The gear wheel being turned iscalled the input gear and the one it drives iscalled the output gear.Gears with unequal numbers of teeth alter thespeed between the input and output. This isreferred to as the Gear Ratio.

The drive gear is known as the input gear.

The gear that is beingturned is referred to asthe output gear.

CALCULATING RATIOSThe following example shows how the ratiosare calculated.

10 teeth 30 teeth

Input gear

Output gear

If the input gear (A) has 10 teeth and theoutput gear (B) 30 teeth, then the ratio istermed 3 to 1 and is written down as 3:1

Ratio = No. of teeth on the output gear B (30)No. of teeth on the input gear A (10)

= 3 and is written down as 3:11

Simply divide the amount of teeth from theoutput by the intput gear to work out the ratio.In the above example, for every completerevolution of the input gear the output turns 1/3of the way round. In other words it takes 3turns of A to rotate B once. This means youare slowing down the action and is referred toin engineering terms as “Stepping Down”. If Bwere the input gear and A the output gear,then the opposite happens and we “Step Up”.Then it would take 1 turn of the input gear toturn the output gear 3 revolutions, giving aratio of 1:3.

Stepping up produces a much faster outputspeed, but mechanically delivers less power.Be aware of this as you may find that yourAutomata does not work properly or thehandle is very hard to turn. However, it isuseful if you want something to move morequickly in relation to other components.

Gears also alter the direction of rotation. Inthe above example gear wheel A is rotatingclockwise but as it turns, gear wheel B ismoved anti-clockwise.

Stepping down has the advantage ofproducing more power although at a slowerrate. This is often a big advantage withautomata as some of the mechanisms canget stiff or are under tension so it makesturning the handle easier.

Input

Input

Output

Output

A B

BA

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GEARSGEAR TRAINSAs we have seen, gears not only affect eachother in the amount of movement they makebut also in the direction they move. This is notnormally a problem but there may be timeswhen you need to keep things moving in thesame direction. This problem can beovercome by introducing a third gear wheelwhich is the same size as either the input oroutput gear. (Gears are a bit fiddly to make soI would always go for the smallest one).When you have three or more gears in a linethey are referred to as a Gear Train.

Input GearOutput Gear

Idler Gear

The idler gear will reverse the direction so thatthe input gear now turns in the same directionas the output gear. Providing you have the same amount of teethas the input or output gear then your ratios willnot be affected.

COMPOUND GEAR CHAINAutomata tend to be fairly small, somechanisms are sometimes packed in a bittight. To save space when working with gears,more than 1 may be placed on the same axle.This is called a compound gear train.You can have different size gears on thesame axle, but this will affect the output andneeds to be taken into consideration whencalculating the Ratios.

InputOutput Output

Input

The above example shows a compound geartrain. Output Gear B and input Gear C sharethe same axle. The gear ratios are as follows:A= (20) - B =(80) This gives a ratio of 4:1So for every one revolution of A, B turns 1/4of its full cycle.C =(10) - D = (30) This gives a ratio of 3:1So for every one revolution of C, D turns 1/3of its full cycle. You must take intoconsideration that B is moving slowly at 1/4of the input speed of A. This needs to be takeninto account in order to find the final ratio.

20

80

1010These two gearsshare the sameaxle.

3030

AB D

C

Although this is starting to get complex, let’slook at it in automata terms and workbackwards. You will have to turn the handleand make gear A turn a little over 12 times inorder to make gear D turn once. The trick is towork out what you want from each set of gearsand then combine them.Do not worry if you find that the maths isgetting complex. You are very unlikely to needto use a compound gear chain in the earlystages of automata. They do not really comeinto their own until you move onto the morecomplex automata, by which time you will havea much better understanding of the mechanicsinvolved and will be able to refer back to thissection.Below is the equation needed to find out thefinal drive ratio of Gear D in relation to A.

Gear Ratio = No. of teeth on Output gearNo. of teeth on Input gear

For gears A and B,= 80 = 4 4:1

20 1For gears C and D

= 30 = 3 3:110 1

Gear ratio of compound gear = 4 x 3 =121 x 1 1

Gear ratio of the compound gear train = 12:1This means it takes 12 revolutions of A to turnD once.

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GEARSGEAR TOOTH SHAPEWhen it comes to designing automata, gearsare very useful. I like to think of them as timemachines that slow things down or speedthem up. Until now, the automata we havelooked at using cams or cranks complete theirperformance on one revolution. This is fine inmany circumstances, but there are times indesigning automata when it would be nice toslow things down. This extends theperformance, allows more things to happenand builds up audience expectation.Gears can be made from a range of materialsas we will see later. The most important thingis to make sure that the teeth are of equalsize on all the gear wheels. If they are notthen they will jam. The shape of the teeth canvary, so lets look at some examples. This gearbox from a car uses just about

every type of gear you can think of. Most ofthe machines in our homes and work placesmake use of gears and they are probably themost widely used of all the mechanisms.Gears are used to control both speed andpower. In the world of engineering you do notget something for nothing, and this certainlyapplies to gears. You can have more speedor more power, but you cannot have both atthe same time.

ANGLED TEETHThese are slightly more complicated to make, butwork well and allow for greater inaccuracy beforethey jam.

SPIKED TEETHThese are simple to make and work well. I usethem a lot when making automata.

SQUARE TEETHThese are fairly simple to produce but you mustbe very accurate or they will jam. You will need tomake the spaces wider than teeth in order forthem to mesh.

DIRECTIONAL GEARSSo far we have looked at gears that runparallel to each other but as well as slowing orspeeding action, gears can also be used tochange the direction of the drive shaft whichcan be very useful when making automata.

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GEARS

Input

Output

These gears are running at 90o to each otherallowing you to change direction. By varyingthe sizes of gears you can also change the ratio.

I usually make these types of gears usingpanel pins (small nails) which are hammeredinto wood after which I cut the heads off. Youcan also use wooden dowel which works verywell and is surprisingly strong. If you findmaking gears too difficult at the beginning,you can use plastic ones which can beobtained from model shops.

DESIGNING GEARSWhen designing and making gear wheels youneed to apply a little common sense. Theload or pressure put on the gears in automatais usually very small compared to that of a cargear box, for example. This allows you to getaway with things that you couldn’t in othermachines. However, you still have to followsome simple engineering guidelines.You will need to identify what you want to getfrom the gears so try running through thissimple check list.

1) Do you want the gears to step up or step down (speed up or slow down the performance)?

2) Do you want the gears to run parallel, or at an angle of 90o to change the direction of the drive?

3) What size do you need to make them? (small space means making smaller gears and this can get tricky)

4) What is the best or easiest material to make them out of? (this may well depend on how heavy a load you want them to drive)

Each automata you make will have differentdesign criteria to meet, but there are somecommon design and construction solutionswhich work well.

You can use panel pins orwooden dowel to make bothparallel gears and bevel gears.

Bevel Gears

Parallel Gears

Bevel Gears

25

GEARSDESIGNING WITH GEARSWhen drawing gears they are represented as eithera circle with just a few teeth at the point that theymesh, or as twin circles denoting the teeth.

Although this may seem very technical it is goodpractice to visualise gear wheels like this, especiallywhen it comes to drawing up your plans for makingautomata.Opposite is a sample of drawings from my sketchbook showing how I indicate the gears and othermechanisms. I work totally free hand and never usedrawing tools. This is purely a personal way ofworking, and you may be happier working in amore technical way. Which ever method you use,clear indication of your intended mechanisms andthe ability to interpret your drawings are the keyfactors. I often write notes to accompany mydrawings precisely for this reason, as I often cannot remember the details solely from the sketch. Afew notes can explain a complicated mechanism.At the time of designing it all makes sense, butwhen you return to your plans 3 weeks later you willbe surprised at how difficult it is re-interpreting yourwork - so make notes!

26

GEARSGETTING MORE OUT OF GEARSA useful trick, when using gears, is to offsetthe two supporting shafts so that additionalmechanisms can be used.By offsetting the drive shafts, you will be ableto run cams or cranks at different speedswithout jamming or hitting other components.This can help to give your automata severalspeeds of movement and make things reallyexciting.

The output gear (shaft B) turns once for every three turns of the crank handle (shaft A). Theinput gear is fixed to shaft A and turns a larger gear wheel on shaft B, therefore creating a ratioof 3:1. You can now use shaft B to run extra cams or cranks which will be running a third of thespeed of shaft A, which you can also run cams and cranks from. To make things really excitingyou could create a gear train and have another drive shaft!

By offsetting the two drive shafts, as onthe automata below, you can get twospeeds of movement.

You obviously need to offset the two driveshafts, but the secret is to do it by just theright amount. This will enable you to driveother objects with cams, pulleys even cranks.The amount you offset is limited by thephysical space available in your automatahousing (Trial and error is the usual way ofmeasuring.) The distance between A and Bis determined by the amount you offset.

Drive Shaft A

Drive Shaft B

This automata called the “Mad Scientist”slowly raises a large knife above his head andtries to split the atoms that are leaping aboutwildly on the table. The scientist is pulledback by a cam running at a third of the speedof the handle on which the atoms areattached. The atoms move up,down, backand forth very rapidly in relation to thescientist . The whole thing works bysimply offsetting the two driveshafts, A & B.Note, you can not run them verticallyparallel as the top shaft will block thedrive shafts, cranks, etc.

A B

27

GEARSMATERIALS AND CONSTRUCTIONGears are both challenging and fun to make.You can use a number of different materialsand, as the mechanical load is very light, cardand even paper can be used. these arecheap to buy and easy to work with. Othermaterials such as wood and metal are alsovery versatile.After designing your automata, you can makethe gears in thin card first to sort out anyproblems. Amazing strength of constructioncan be achieved by using paper and card,and many automata are built solely usingthese materials.The automata you make will all have differentcriteria to meet, but there are some commonsolutions which work. Before you start, bearthe following golden rule in mind:

KEEP THINGS SIMPLE

You will want to experiment with your owngears, construction, and materials. But if youfeel unsure about making gears then you canbuy ready made ones from model supplyshops. These are usually made from plasticand come in a range of sizes and ratios.

The gear set below is quick and relativelyeasy to make. It is used a lot, as it tends to domost jobs well and can easily be expandedupon. For ease of construction, work in pinewhich is a relatively soft wood that is easy tocut and at the same time reasonably strong.

You need to work out the size of the outputgear ( The biggest that will fit in yourautomata) and then divide it into twelve parts.The next stage is to work out the depth of theteeth. 10 to 15mm is a good rule of thumbbut, again, you can experiment. It alsodepends on the size of the gear wheel.

The output gear has onlyfour teeth made from eitherpanel pins or woodendowel. The four pins shouldform a perfect square; thecentre of which gives youthe point to put the shaft in.

You need to space them in such a way thatthey engage the teeth on the output gearwithout jamming. Ideally they should justtouch at the bottom ofthe spiked gear wheel.

You can make the gears mesh a little higherup without any problems, to as much as5-6mm depending on the size of your gears.

This set up produces a3:1 gear ratio

input gear (4 teeth)

Output gear(12 teeth)

28

GEARSMASTERING GEARSAim to get the pins meshing about two thirdsdown the slope on the gear tooth. The ideal isto get the pin to just touch at the bottom. Bygetting the pins to touch further up allows forany inaccuracies that can occur and stillallows the wheels to keep moving withoutjamming.A little trial and error is needed when youstart making gear wheels. Do not bedisappointed if things do not work perfectlyfirst time, as it may take several attempts.When you have got the technique masteredyou will be able to construct working gearsets to any size and ratio, and that is someachievement.

The best way to construct the spiked gear wheel is to divide a circle into 24 segments. Then draw asecond circle to give you the height of the gear teeth; 10 -15mm is a good average. Then simplyconnect the lines to draw out the twelve teeth and you are ready to cut them out. This method canalso be used to construct a pin wheel.

WORKING OUT SIZE AND RATIOWhen designing and making your gears youhave to be very precise with yourmathematical equations. You will need totake into account the number of teeth, theratio and the size of your gears. Here is apractical example to help explain how to dothis.The “Mad Scientist” Automata had a gearratio of 3:1. Assuming that the larger outputgear would have to be 60mm in order to fit,this meant that the input gear would have tobe 20mm. The measurement was calculatedby dividing 60 by 20 to give a 3:1 ratio. So20 goes into 60 three times.

By working backwards you can decide on thelargest most practical gear wheel first and thencalculate what the drive gear will be. You canof course do this the other way round.The next thing to calculate is the number ofteeth. Having twelve teeth on the larger outputgear meant that they needed to be spaced atintervals of 30 degrees. (360 / 12 = 30).Theinput gear would have to have1/3 as manyteeth. In this case four (360 / 4 = 90) and wouldneed to be spaced at 900 from each other.The formula below is used to work out thevelocity ratio of gears:

Velocity ratio= number of teeth on output gear (12)number of teeth on input gear(4)

VR= 124

Therefore the velocity ratio or Gear Ratio is 31

It is unusual to write this as a fraction so thegear ratio is 3:1

The first figure relates to how many revolutionsthe input gear moves in relationship to theoutput. In this example, 3 revolutions of theinput gear moves the output gear 1 revolution.

The maths for working out the number of teethfor each gear is not difficult, but it has to bedone so that the teeth mesh properly.

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This automata has several actions going on atonce which all culminate in a final outcome. Itis then ready to start again. Let’s take a closerlook at the mechanisms and some of the

problems encountered. The automatarelies heavily on gears to slow down orspeed up various movements. Calledthe “Silly Explorer”, the main figuregently tips back and forwards beforesuddenly dropping into the crocodile’smouth. The crocodile’s mouth thensnaps down onto the explorer , whose

legs rapidly thrash up and down whilehis body jerks several times inside

the crocodile’s mouth. Finally thecrocodile’s mouth springs openand the explorer rises up so theperformance can happen again.

GEARSTIMINGYou are aware now of how gears can be usedto either slow things down or speed them up.Most automata take advantage of gearsslowing down and extending theperformance. Another advantage is that“stepped down” gears produce more force(first gear on a car or low gear on a bike) andso can power the automata more easily.The last thing to look at is timing. When usinggears you may want several movements toculminate in a final activity and then startagain from the beginning. Thisobviously needs to be worked outso that gear ratios and speeds allcoincide from one starting point,and end at a common finishingpoint.The examples opposite shows howto tackle this problem. It is fair tosay that you are getting intoadvanced Automata-makingterritory at this stage. If you do notfeel up to it come back to this partwhen you are ready.

30

GEARS

The mechanisms here show the linkages thatmove the feet up and down. A bar is raised bya snail cam and lifts both feet clear of the conrods that rotate directly on the main driveshaft and are moving all the time. The snail cam drops the bar, so the feet areable to move up and down rapidly.

The mechanisms below include the snail camwhich controls the leg linkages. There arealso two square cams that provide the rapidleg movement. A larger snail cam controls thedropping and pulling up of the explorer, and atriangular cam provides a rapid movementthat jerks the explorer’s body up an downwhen inside the crocodile’s mouth. This isconstantly moving as are the two squarecams.

The gear ratio for this automata is 3:1. Theoutput shaft is used to slow different partsdown. A large snail cam controls the openingand closing of the crocodile mouth, whileopposite is another snail cam that controls theexplorer’s body. All the parts aresynchronised, so that by the fourth turn of thehandle everything lines up and starts againfrom the beginning.

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RATCHETSALTERNATIVE GEARSThe ratchet is really another form of gearing.Unlike gears, which can be used to speed upor slow down movement, the ratchet can onlybe used to slow things down and it happensin a very jerky manner. Below and opposite isan explanation of how they work.

For every 8 turns of the crank, the ratchetwheel turns one complete revolution. Thisgives a ratio of 8:1.

The pawl is rotated on a crank and pushes theratchet wheel one notch for every revolution. Itwill take 8 turns of the crank to produce onecomplete turn of the ratchet wheel.

This 2nd pawl is lightly sprung, and locks intothe ratchet wheel stopping it movingbackwards.

The crank turns clockwise which helps to pushthe pawl, or catch, down onto the ratchet

If you add more teeth to the ratchet wheel itwill take longer to rotate. With fewer teeth itwill take less time.

CRANK

PAWL

RATCHET

PAWL

Below is a 3D drawing of a simple ratchet. There are only a few moving parts to makebut as with all mechanical things you do have to work out fairly accurately the size anddistance of all the various components.

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RATCHETS

This gear set has10 teeth on theinput gear and 80teeth on theoutput gear, givinga ratio of 8:1

The gears above would turn constantly andgive a very smooth action but cutting 80 teethis a lengthy task. The gear wheel would needto be pretty big which would take up a lot ofspace. The ratchet on the other hand onlyhas 8 teeth, is simpler to make and uses lessspace.If you want to slow down movement a lot thenthe ratchet is a good alternative to gears. Itdoes however give a jerky movement.

TAKING ADVANTAGEThe ratchet’s inherently jerky movement canbe used to advantage. The automata belowuses this movement to build up suspensebefore culminating in a big finish.

In the Automata above, the man’s arm lifts up, hovers and then swats down on the fly. The ratchet has asnail cam attached to the same shaft so is turning at the same speed. The cam progressively lifts the armand provides the sudden drop with a little help from gravity. The movement is jerky but doesn’t detractfrom the performance, if anything it adds drama.

This ratchetwheel has 8 teethso the equivalentratio (like thegear set below) is8:1

1

2

3

4

SLOWING THINGS DOWNAs we have seen, most automata benefit fromslowing down movement. The ratchet doesthis in a fairly simple way.

33

RATCHETS

In the sequence shown above, the ratchet is being driven by aclockwise rotating crank. The ratchet has 8 teeth so it take 8 turns ofthe crank to complete one turn of the ratchet wheel. The black dotshows you that the ratchet turns 1/8 of a cycle per push of the crank.

The rotating crank pushes the ratchet wheel for half of the time andthen pulls the pawl for the other half. In other words, for every completecycle of the crank, it is only supplying an input motion to the ratchet forhalf of the time. This is why the ratchet has a jerky motion.

1 2 3

4 5 6

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RATCHETSDESIGN Like gears, the first thing you need toestablish is the ratio you would like. This isvery simple to work out as the ratio willalways be something to 1. The pawl onlyturns or pushes once per revolution, unlikethe input on a gear wheel which could havemany teeth. The output or ratchet wheeldetermines the ratio. For practical reasonsthe smallest amount of teeth would be fourbut the upper limit is only determined by theamount you can fit on to the ratchet wheeland what size you want it to be.Between 8 and 12 teeth will accommodatemost automata needs while not being toodifficult to make.There are two kinds of ratchet teeth you canmake, referred to as square cut or rounded. Itis far easier and quicker to make square cutteeth.

Rounded cut teeth.

When designing your ratchet you will have to give careful consideration to the size and location ofthe pawl. This must be positioned in such a way that it pushes the ratchet wheel one notch andthen comes back and drops down in position ready to push the ratchet wheel on the nextrevolution. The second pawl, or catch, will have to be positioned in such a way as to lock theratchet wheel.

The pawl must be free to push the ratchet wheel and then drop back. To work out the position of the pawlyou need to calculate the amount of travel the pawl must move, so that it is able to drop down onto thenext tooth. The pawl in this model is rotated in a clockwise direction which then helps push the pawl downonto the ratchet wheel. The reverse would be true if the model were reversed. You need to take this intoconsideration.The diagram below shows that the crank has a throw of 26mm while the ratchet face is only 24mm. Thisallows the pawl to clear the ratchet and drop down. The position of the crank and the length of the pawlwill probably need a little fine tuning in order to work. Ratchets are very useful in automata and wellworth experimenting with.

Square cut teeth.

26mm

24mmCrank

Ratchet Face

Note that the crank sits higherthan the ratchet which allowsthe pawl to drop down

Pawl

CONSTRUCTION TIPLike gears, you can laminate several piecesof card to make a strong ratchet wheel. Thesame can be done with the catch and pawl.You can use elastic bands instead of springsand art straws or pencils can be substitutedfor wooden dowels. Alternatively you canwork with wood or metal. Pine is easy to workwith and fairly strong.

35

PULLEYSTHE POWER OF THE PULLEYPulleys work in a similar way to gears, exceptthey are not directly joined but linked by a beltmade from elastic bands, tubular springs orsome other flexible but strong material. Acommon example is the fan belt in a car thatlinks a number of pulleys.To stop the pulley belt slipping off, pulleyshave grooved rims. This also keeps the beltrunning in a straight line.Pulleys that use some form of belt drive arereferred to as “Friction Drive” mechanisms.

Pulleys have several advantages over gears,but also some disadvantages.The main advantage is the fact that they aresimple to make and can be used at a distancefrom each other, unlike gears that need totouch in order to work. The disadvantage isthat they work by friction and so can slip,which could seriously upset the timing of acomplex automata. You can get a toothed pulley and belt whicheliminates any slipping or timing problems.Many cars have a cam belt that works on thisprinciple. Some model suppliers sell specialtoothed pulleys but they tend to be veryexpensive and are rarely used in automatawhich generally have a “Friction Belt” system.This is simple and very effective in mostcases.The belt can also be substituted by a chain, abicycle being a good example of this system.Model suppliers often stock small plastictoothed pulleys or chain sets which arereasonably priced.

Toothed pulley and belt

Sprocket and chain

A bicycle chain

36

PULLEYS

Like gears, you can use the pulley to eitherstep up or step down the drive. But instead ofcounting teeth as with gears, you simply makethe diameter of the pulley wheels larger orsmaller.

By dividing the input diameter by that of theoutput, you can work out a final ratio. In theabove example, the ratio is 2:1. This meansfor every 2 revolutions of the input pulley theoutput turns one full revolution. You couldreverse the input and output pulleys.You can see that pulleys rotate in the samedirection (unlike gears which do the opposite).

Pulleys are useful for getting the drive actionto happen in awkward places. You can usethe drive pulley to transmit its motion to theoutput pulley which may be some distanceaway. We can also use pulleys to reverse the actionby putting a twist into the belt. This makes theoutput pulley move in the opposite direction.Again this can be very useful.

A twist in the belt reverses the direction of theoutput pulley

The Automata opposite uses a pulley totransmit the motion over a long distance. Italso slows the action down and transmits it tothe output pulley which is in a confined space(Nelson’s body). Pretty good going for asimple pulley system!

Input

Output

Pulleys rotate in the same direction

37

PULLEYSAPPLYING PULLEYS TO AUTOMATAWhen you want to transmit the drive oversome distance, pulleys are an ideal choice.As we have seen, they are simple toconstruct and take up comparatively littlespace. In fact, they share many of the virtuesof the ratchet, with the big advantage ofproducing a constant and smooth drive force.But it doesn’t stop there; the pulley canperform one other vital function, which is tochange the direction of drive. This can be toany angle but the most common use wouldbe to turn the drive through 90 degrees. Thissame task could be performed by gears butwould be significantly more difficult to make.When It comes to making automata, thissimple trick of changing the drive directioncan be invaluable for its simplicity andeffectiveness.

Pulley belt

The drive is nowturned through 900

The “Cat eating Fish” automata above uses the pulley twisted at 900. This avoided having the crankhandle at the front and middle of the mechanism housing. The pulley drives a larger one in the cat’smouth which slows the action down slightly and, as with gears, provides more force. The fish ispainted onto clear plastic which is shaped like a snail cam, so as it goes round it opens the cat’smouth. If the pulley slips it doesn’t matter.

38

PULLEYSCONSTRUCTION TIPSLaminating is one of the easiest ways tomake a pulley wheel: cut several circles ofwood or card making two of them slightlybigger (around 5mm). Glue them together,sandwiching the smaller ones in the middle.Make sure that the pulley is a little wider thanyour belt, and try to keep the centres lined up.When the glue has set you can drill the centreout to the size of the drive shaft.If you are working in wood then you can sandthe inner edge down to create a bevel. Thiswill help guide the belt onto the pulley.Use wood glue even on card, as it is verystrong when dry.

The running dinosaur above is driven by a pulley.The top pulley is also an offset crank which turnsthe legs. Because the pulley has a lot of work todo, it was geared down. Sandpaper is wrappedaround the drive shaft, giving the elastic bandmuch more grip.

PUTTING IT ALL TOGETHERFitting the elastic band is often the final partof the assembly process before gluingeverything. Should you find that your elasticband breaks, you could substitute it for aflexible steel spring driving belt. It comesopen ended and can be cut shorter orextended by joining another spring to it.These can be purchased in most modelshops and offer superior performance overelastic bands, which are prone to stretching,and can disintegrate if left in direct sunlightfor long periods.Finally, make sure everything is strongenough to take the tension of the pulley.Remember you are dealing with a frictiondrive, so the tighter the belt the less chanceyou have of it slipping. Make sure that anyaxles are strong enough to take the load.

Sandpaper Pulley

Elastic bands make good cheap drive belts buthave certain limitations. Flexible steel springdriving belts are much tougher.

This automata shows how useful a pulley canbe. What makes this one so interesting is itsuse of linkages to move the arms and head.

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LINKAGESWHAT IS A LINKAGE ?“Linkage” is the term applied to the parts of amachine or mechanism that connect movingparts together. Many of the different drives that we havelooked at use some form of linkage orconnecting rod to transfer the power ormotion. Linkages can be used to controlmovement as well.The flying pig below uses a good example oflinkages. The body is pushed up and down(by what is effectively a linkage) and, as thewings are held in position, it gives the illusionof the pig flying.

In this automata the linkages are used to bothcontrol and transmit movement.The cranks have linkages attached to them,which are in turn attached to the man’sarms.They pull the arms up and push themdown. As the cranks are offset by 180O theymove up and down alternately.

This linkage movesthe arms as the legsmove around.

40

LINKAGES

Linkages can be made from a range ofmaterials, but wood and metal are perhapsthe strongest and most commonly used.It is important to note that where there ismovement between materials there must besome form of free movement otherwise themechanism will jam.Linkages are used to transfer motion, so theymust be properly designed in order to functionas intended. Although the mechanicalstresses in automata are very low, you stillhave to apply good solid engineeringprinciples. Let’s take a closer look at theautomata on the previous page and see whatdoes and doesn’t work.

The Pig’s wings are linked to the body and are pivoted, which allows them to move freely upand down, but not backwards and forwards.As the pig is moved up and down, the wings are forced to either rise or drop. This can onlyhappen if the linkages are not attached, otherwise the wings would not move.

With the man and his chopping knives, thelinkages play a vital part in allowing themovement to happen. The ends of thelinkages are made into rings and joinedtogether which allows them to move freely.You may find that, very occasionally, thelinkages jam because the ends allow for toomuch freedom of movement.

This mechanism is more complicated to makebut is a much better design, as it only allowsmovement in its intended direction (up anddown) not side to side.

The rings allow for movement in the requireddirection but also in unwanted directions.

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LINKAGESThe Golden

Mechanical Disciplines.

Design your mechanical partsso that they are free to move,

but constrained to only move inthe intended direction. It is

often better to make things alittle on the loose side. But beaware that for every slack partin the mechanism there will be

a loss of input motion. It ispossible to make a machine

with so many slack parts thatall of the input motion is lost

and the output is nil.

TRANSMITTING AND CHANGING MOTION

Linkages can be used to transmit and changethe direction of movement. One of the mostcommon methods to use is the bell crank.

It is important that the linkages are free tomove when attached to the bell crank.Linkages are a vital part of making Automatafunction. With careful thought and design youshould be able to produce the exactmovement you require.

Input

Output

In the example above you can see how theinput linkage pushes, so the output linkagepulls in the opposite direction.

This automata usesanother variant of the bellcrank. The cam pushes arod up and down, with ahorizontal linkage thatconnects with the twobell cranks, and makesthe hands clap as thediner tries to catch the flyin his soup.

42

BEARINGS, SHAFTS, FRICTION AND LUBRICANTSLOW SPEED, LOW STRESSSo far we have looked at very simplemechanical mechanisms which, when appliedtogether, are capable of producing verycomplex automata. For the most part, woodand metal have been the most convenientand best materials to use, although there arealternatives such as card, paper and strawsetc. All the automata we have looked at so farhave several things in common in engineeringterms. They can be described as working atslow speeds, under low stress and with lowoutput. In practical terms this means you donot have to worry about special lubricants andbearings to keep things moving. Howeverhere are some simple ways to keep thingsrunning smoothly.

BEARINGSLets start by looking at bearings. Bearingsusually support a moving shaft and help itrotate freely under as little stress as possible.Many commercial machines have bearingsmade up of a metal case called a “chase” thathouses hardened steel ball bearings. An innercase holds them in place and is attached to arotating shaft. The ball bearings help spreadthe load and force of the shaft, they areusually lubricated to cut down friction. It isusual to construct an open box to house themechanical parts of an automata, which arepowered be a central shaft. This shaft sitswithin the outer wooden walls and is free torotate, so the box acts as the bearingsupporting the shaft.

You need to make sure that the drive shaft isfree to rotate and is not “sticking” as it turns.The hole it goes into should be slightly largerthan the shaft itself but not so big as to to giveyou too much play. This could cause moresensitive mechanisms, like gears, to jam.

LUBRICANTSAn ideal lubricant to use when working withwood is graphite, which is used in leadpencils. When applied to wooden surfaces, itmakes an ideal lubricant.

Apply the graphite from a pencil in to the hole(bearing) or drive shaft to enable the shaft toturn more freely. Do not get it on any areasyou need to glue.

Graphite works well on cams and camfollowers. It also works well on copper orbrass tube. Never use oil, as it is notnecessary and can cause the shaft to stick.

43

DRIVESELECTRIC MOTORSOne advantage of electric motors is that theygive a constant output, so the automata isless likely to be damaged. This is animportant consideration if your work is goingto be on display and used by the public.Most electric motors turn at very high speeds.The typical revolutions per minute (or rpm) ofa small 12 volt motor is between 200 and12,000 rpm, so you will usually have to stepdown. Most hand crank speeds work out tobe between 30-50�rpm, which is a goodspeed to aim for.The best options for stepping down speedsare either gears, pulleys or a combination ofthe two. Many electric motors come with asmall gear wheel, which is a good startingpoint.

If you decide to use a motor there are a fewthings to consider. Firstly, what voltage does itrun at? Most cheap motors run at between1.5 to 9 volts. As a rough guide, the higherthe voltage the more powerful the motor.Even a small 1.5 volt motor can give out a lotof power when stepped down.The second consideration is how easy themotor will be to attach to a board, or anchordown. Better motors have two lugs with holesto allow them to be screwed or bolted down.

HAND POWERThere are two main ways of powering yourautomata. One is to turn it by a handle (humanpower), and the second is to use a motor, themost practical being a small electric one.I design all my automata to be hand driven,which helps bring the mechanism to life andmakes the user feel part of the performancethey are watching.Power is transmitted through a crank, which ismore than sufficient to work an automata, andis quite comfortable for the operator to use.

44

Drives can be broken down into two types:

Positive Drive and Friction Drive

Positive drive means that the input and outputforce are connected directly. They are lockedor synchronised and can’t slip out of place.

DRIVESA friction drive relies on two surfaces grippingwhen the force is applied to them to transferthe movement. “Slipping” is the term givenwhen the drive input and output do not turnproperly because there is not enough frictionto keep the drive in contact. Pulleys are verysusceptible to this. A screeching car fan beltis a good example a slipping friction drive.

The crank handle is a positive drive. The crankis connected to the drive shaft and is turned byhand.

Gears are positive drive. They can’t slip as theyare always in contact with each other.

The pulley is a friction, or indirect, drive. It relieson the friction of a pulley belt to keep the twowheels connected. It can easily slip and is notrecommended where synchronisation is needed.

The cam can be both a direct and frictional drive. Anoffset cam will directly drive the cam follower butalso act as a friction drive to give a circular motion.

The crank is a positive drive, as the connectingrod that transfers the motion is directlyconnected to the crank and so can’t slip.

The ratchet is a positive drive mechanism. Onepawl stops the ratchet slipping, while the otherprovides the transfer of motion.

Sprocket and chains are linked so the drive can’tslip. They can be considered to work like gears.

45

LEVERSA lever is a device that applies or transfersforce. It is a simple mechanism that usuallyconsists of a rigid length of wood or metal,which pivots round a fixed point called afulcrum.

Most machines employ some form of lever,and you will find that they are used a lot inautomata. It is useful therefore to understandhow they work and how to use them in yourown designs.Levers work on the principle of “mechanicaladvantage”, which can be calculated by asimple equation, and is used to compare theeffort applied to the load moved. We will lookat this formula a little later on.Archimedes established the Law of theLevers in his book “On the Equilibrium ofPlanes”. He described the three separatetypes (or orders) of levers, which have theirfulcrum, effort and load arranged in differentways.

First order lever.A first order lever has its fulcrum pointbetween the load and effort.

A good everyday example of a first orderlever is a pair of scissors.

Second order lever.A second order lever has its fulcrum andeffort at opposite ends, and the loadsomewhere between the two.

A good, everyday example of a second orderlever is a wheelbarrow.

EffortLoad

FulcrumFulcrum

Effort Load Load

Fulcrum

Effort

LF

E E

F

L

46

LEVERSThird order leverThe third order lever has the fulcrum and loadat opposite ends with the effort somewherebetween the two.

A good, everyday example of a third orderlever is a shovel

A little bit of theoryA lever can produce a small output motionfrom a large input force, as when using acrowbar. A lever can also be used the otherway round, where a small input movementcan be increased by a lever to create a largeroutput movement such as a pair of scissors. Moving the fulcrum point, the effort or loadpoints can change the effectiveness of alever. For example if you move the fulcrumpoint on a first order lever towards the effort,the load travels further but takes more forceto move it. The opposite happens when youmove it towards the load.

The important thing about levers is the waythat they can be used to transmit, amplify ordecrease movement. In engineering termsyou are experimenting with the “MechanicalAdvantage” of the lever. When a small effortmoves a larger load the smaller effort has tomove a much greater distance than the largerload. There is a price to pay for gainingmechanical advantage. However, at the scalewe normally work with in automata, much ofthis will not really affect you.

The formula for working out the ratio of alever can also be used to work out the“Amplification”, or amount of movement alever will travel. Just like a cam, this isreferred to as the “Throw” and can be used togreat advantage when designing and makingyour own automata.

Mechanical advantage = Loadeffort

If we apply this formula to the example belowyou will see how to calculate both the ratioand the throw of the lever.

We can see that the ratio of A to B is 6cm to2cm, so applying our formula we get a ratio of3:1. This means for every 3cm of travel ateffort (A) the load (B) will move 1cm. Reversethis by moving the fulcrum towards the effortand we magnify the movement for every 1cmof travel on the effort (B), so the load (A) willtravel 3cm. It is also important to rememberthat levers travel in (describe) an arc and donot move in a straight line.

Effort

Load

Fulcrum

Large movement of effort

Small movement of load Fulcrum

EffortLoad

A B

L

F

E

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LEVERSUsing levers in automataYou will find that you use all 3 types of leversin designing and making your automata. Theycan be used to produce a variety ofmovements, but their main function will betransferring motion from cams or cranks.They are, in effect, used as linkages, and youwill probably not be too concerned aboutthings like mechanical advantage. However,understanding how they work is important asyou will need to explore their full potential atsometime.

FIRST ORDER LEVER

SECOND ORDER LEVER

THIRD ORDER LEVER

L

F

E

L EF

L

E

F

Levers play an important role in transmittingmovement within automata mechanisms. Theyare often used as linkages, but the rules of thelever still apply. You can increase or decreasethe amount of travel they have. It is important tobe aware of this when you design and makeautomata, as you may well find parts of yourmechanism moving too much or too little.The model on the left is a good example of this.The distance from the Effort to the Fulcrum isquite short and the distance from the Fulcrum tothe Load is about fifteen times longer whichmeans that only a small amount of movementwas needed in order to lift the arm quite high.The original cam needed to be made smaller asit caused the arm to lift too much.

This automata is called the “Angry Diner”.He rapidly bangs his knife and fork on thetable, impatient for his dinner. His arms actas levers, amplifying the lift from the cam.

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SPRINGSMost automata, when designed properly,should use mechanical force or gravity toachieve the desired motion. There are timeswhen things need a helping hand. Springsare very useful for providing that little bit ofassistance when necessary. Keeping thecam follower on a cam is a good example ofwhere a spring can come in handy.As you design your automata, you willprobably find the need to use springs. Theyare very useful in helping to overcome somedesign inadequacies. It is not cheating, justcreative problem solving!Springs come in three main varieties.

A B C

A is called a Compression spring. When squashedit tries to push back to its original shape.B is called an Extension spring. When stretched ittries to pull back to its original shape.C is called a Torsion spring, and can be used toboth pull or push.

In the example above, the compression springkeeps a wire (which is acting as the camfollower) pushed against the cam

In this example, the con rod (which is attachedto a crank) is pulled back by the extensionspring.

The Automata below uses a torsion spring inside the crocodile’s mouth to help it close with afast snap.

Most model shops sell bags of mixed springsranging in shape and size. They are useful tohave, but do not become over-reliant on them.It is very easy to put a spring in when amechanism is not working properly. Try toresolve the problem or redesign the parts if youcan.You should only use a spring as a lastresort or when it is vital to have one. Springs provide varying tensions, not aconstant load. Trying to find the spring with theperfect tension can be difficult, as they areoften too strong or too weak. You can makeyour own out of sprung steel, such as pianowire if you are unable to buy a suitable one.

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FREE MOVEMENTGETTING SOMETHING FOR NOTHINGSo far we have looked at a wide range ofmechanisms and engineering principles. In thissection I would like to show you how to getsomething for nothing!The automata and mechanical principles that wehave covered in previous chapters have allbeen carefully designed to move in a certainway. But we can also tap into the power byapplying the principles of free movement. I willexplain this phenomenon with the examplebelow:

The Robot’s body is fixed to a con rod attachedto a crank. As it moves back and forth, the arms,legs and head flop about as they are free to move.This gives much more life and action to theautomata. The beauty is in the simplicity. Thereis no need to make complex linkages to do this.

Try to explore and exploit “free movement” inyour automata wherever possible. It is a greatway of getting in extra action without extrawork.

The fish turns back and forth but, because thetail and head are free to move, they swing fromside to side. This use of free movement makesthe automata far more exciting and life-like anddoes away with extra complex mechanisms.

The key to achieving free movement isenabling parts to be free to move. This maysound obvious, but you have to make surethat joints and linkages are designed to movefreely. You also have to give thought to thedesigning of your automata and work outprecisely what is going to happen.Given the random nature of free movement itcan often bring an automata to life.Movements are sometimes jerky and may notfollow a precise path. But this can all add tothe charm. If you want precise and smoothmotion you have to control thingsmechanically.

The Dragon’s body is made to move in acertain way using a crank but the mouth ishinged and flaps about freely.

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FREE MOVEMENT

This automata explores free movement to thefull. The twin cams rock the boat up and down,while everything else is free to move. Gravitypulls the oars back and forth which in turn makethe sailor rock to and fro. The cat rolls in andout of the boat whilst the sea gull wobbles abouton a spring. Finally, the fish on the end of theline leaps about as if it is very much alive.This fish is a good example of theuncertainty of free movement. It wasexpected mainly to wave to and fro, butsomehow it picks up the variation of themechanism and wildly leaps about. This wastotally unplanned, but is a real added bonus.

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THE DESIGN PROCESSINSPIRATIONMechanical toys and automata often appearto have a life of their own, the simplemechanical parts seeming to produce analmost magical response in the figures thatthey move. Automata come in a vast range ofsizes and varying degrees of complexity.Some may keep your interest for severalminutes whilst others you may just pass over.What makes an automata “good” is verysubjective. We all like different things and wedo not all find the same thing funny. As theold saying goes: “You can’t please all of thepeople all of the time.” So where do you start.The check list below gives some simplesuggestions against which to test your ideas.

1) Is it visually exciting?

2) Is it funny?

3) Will it intrigue the viewer?

4) Will it hold the viewers attention?

5) Is it too complex?

6) Is the humour too obscure?

7) Will I enjoy making it?

This is just a general check list, and is by nomeans a fool-proof system for producing theperfect automata, but it will help to weed outgood ideas from the bad. At the start, baseyour ideas on something that you areinterested in such as a sport or a hobby.Animals can provide a wonderful subject onwhich to base a theme for an automata.As with any creative process, coming up withthe idea is often the hardest part of the wholeprocess. You may, on the other hand, belucky and be brimming with ideas. But it isprobably fair to say that most people have towork hard at the inspirational, or ideas, stage.

RESEARCHOnce you have come up with an idea, thenext stage is to research it. The purpose ofresearch is to get as much information as youcan about your subject. This helps you towork out how something moves, the colours,the scale etc. Research can be broken downinto two areas.

1) Primary Research: This is where you make drawings of your subject from life.

As an example, you may draw a camel at thezoo. You do not have to be a great artist, butjust looking and observing will help youunderstand your subject. You may not alwaysbe able to draw from life, and the temptationis always to work from the easiest sourceshowever, the best and most creative worksevolve from good observation. This is true forall arts and crafts, and is the reason whymany artists spend so much time drawing.

2) Secondary Research: Refers to things such as photos, pictures, photocopies etc.

This is usually the most accessible material toget hold of. The library is a good place tostart, and you can often photocopy relevantpages from books.

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THE DESIGN PROCESS

Designers often put together a “Mood Board”or “Ideas Sheet” which is made up from arange of materials that reflect the theme. Itcan include colours, textures andsurroundings. They are often used in thefashion industry yet are of great benefit to anydesigner. In its simplest form you could pasteup all of your research material onto A3 or A2paper. Remember your ideas sheet is there toinspire you, so make it interesting.

Designing:When you have got your research material,you need to begin developing it, into aworking solution. A good idea is to start bywriting a “Statement of Intent”. This is simplya few sentences about the automata youwant to make. It is a great way of focusingyour thoughts and forms the basis for adesign brief. The following headings will helpas a guide to the sort of things you need tothink about.

1) Who is my automata intended for? A small child, 12-14 year old or adult etc?

2) What size will it be? Automata can range from miniature pieces for dolls houses, through to hand held ones or large scale works.

3) Simple or complex? One golden rule is to keep things simple, but even simple automata can get complicated.

4) What materials do I want to work in? Automata can be made in paper, wood, or metal. Often you will work in a range of materials.

5) Deadlines: How long have I got to make it?

You will find you often have to complete yourwork within in a certain time. So you will needto plan carefully.Once you have established a basic workingbrief you are ready to start designing yourautomata. Begin by thinking about themovements needed to make it behaverealistically, and then try to match these to themechanisms covered in the first part of thebook.Start sketching out your ideas. For complexautomata, you may find it easier to breakdown all the movements and design themechanisms individually. When this is doneyou can then work out how to join the wholething up.The actual design process is both excitingand frustrating. Once you have solved theinitial mechanical problems, it is often helpfulto evaluate your work and see if you cansimplify anything. It is vitally important to keepsketching down your ideas. It is helpful tomake accompanying notes as well. Thereason for this is that what appears to be verysimple and straight forward can often turn outto be confusing and complex when looked ata week later. You may think you understanddrawings at the time, and all the mechanismsmake sense, but things do not always stayclear. A few accompanying notes can help toexplain and make sense of your drawing.They can also jog your memory.

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Design NotesIt is a good idea to work in black felt tip penwhich makes a committed and permanentmark, and will help you to draw and sketch ina clearer, more simplified way. Try it foryourself and see. You should also work in asketch book which can be purchased from artshops and stationery stores. This keeps allyour drawings in one place so there are noindividual bits of paper to lose and you canalso refer back to past work for inspiration orto find solutions to mechanical problems.

THE DESIGN PROCESSDevelopmentYou will need to take your ideas through to afinal design and eventually draw them up infull detail, showing how all the mechanismsand moving parts will work.You may find that none of your initial ideaswere suitable, so a modification orcombination of ideas can be put together toprovide a workable solution.Developing your work is a vital part of thedesign process. You will need to be veryobjective about your own work, whilst notbeing too dismissive of your ideas. Taking anidea and developing it into a final solution isthe very essence of the design process. Soenjoy it and have fun “pushing” your talents tothe limits.

Working ModelMaking the working model helps to highlightany design and construction problems. It canalso save you a lot of time and effort later on.At this stage the design can be modified andconstruction details finalised. It is also a vitalpart of the design development process, asthe working model helps you to evaluate yourideas and, if necessary, make changes. Insome extreme cases it can highlight the factthat the automata just will not work asintended and a major redesign is called for.This is where the phrase, “back to thedrawing board” originated from, and ithappens to all of us at some time or another.The working model or prototype is best madewith card, wood and string as they are flexibleand quick to modify. Card is surprisinglystrong and can be used for the final automataif you wish.Your working model or prototype plays a bigpart in the evaluation. At this stage thepracticality and feasibility of your design canbe assessed. You will find that there is almostalways something that needs changing inorder to make things work, and you oftendiscover an even better way of constructioncomes to light. It is also at this point you should evaluateyour work, and make sure that it still fits youroriginal criteria, ie: intended use, etc.

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Below is a flow diagram of the design process:

INSPIRATION

RESEARCH

DESIGN

DEVELOPMENT

WORKING MODEL& PRELIMINARY EVALUATION

FINAL OUTCOME

EVALUATION

THE DESIGN PROCESSFinished AutomataWith the working model complete, functioningproperly and evaluated, you are ready to starton your finished piece.The choice of materials to work with is up toyou, as the designer. An appropriate choiceshould logically come out of the designprocess and working model. Wood, metal andhard plastic, termed “ resistant” materials, arehard and strong and should be used if theautomata needs strength, otherwise use cardor paper. The working model can form a template fromwhich to make many of the mechanical partssuch as cams, gears and pulleys. Be preparedfor some things to need modification.Resistant materials are less tolerant thensofter ones, and whereas a card gearwheelmay work, a wooden one may jam or stick, ifnot properly designed.

EvaluationThe final evaluation is used as a guide withwhich to test the success of your designagainst your original intentions.Every stage of the design process will includesome form of evaluation. Indeed designing isreally a continuous process of evaluation.The evaluation may just be a process ofmaking mental notes about what did and didnot work. Alternatively you can write up notesin your sketch pad. This is the best method toadopt as it forms a valuable source ofresearch material to refer to in the future,especially when you encounter problems.

A finished automata is a wonderful thing and you can rightly be proud of your achievements. Fewthings are as rewarding as seeing people enjoying your work and asking , “How does it work”?

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THE DESIGN PROCESS - SUMMARYTwo golden rules to keep in mind whenstarting are:

1) KEEP IT SIMPLE

2) MAKE IT INTERESTING

When you have come up with an idea for anautomata run it through this check list:

1) Is it visually exciting?

2) Is it funny?

3) Will it intrigue the viewer?

4) Will it hold the viewers attention?

5) Is it too complex?

6) Is the humour too obscure?

7) Will I enjoy making it?

You will then need to do some research aboutyour subjects, trying to get as much visualinformation as you can. There are two maintypes of research:

1) Primary Research: This is where you make drawings of your subject from life.

2) Secondary Research: Refers to things such as photos, pictures, photocopies etc.

After making the initial working model, it is useful toevaluate its effectiveness and highlight any designproblems that may still need to be resolved.

1) Does it work the way it was intended?2) Can anything be improved or

simplified?

3) Is it going to be reliable?

In the final evaluation you need to test against

your original intentions. Below is the

procedure you run through.

1) Does it appeal to its intended user?

2) Does it work as intended?

3) Is it safe for use by the intended user?

4) Can it be improved in any way?

5) Is it going to be reliable?

6) Will any of the parts wear out too

soon?

7) How easy will it be to repair if

something goes wrong or breaks?

8) Were suitable materials used for

the final construction?

9) Could alternative materials be

used (recycling)?

10) Can it be adapted in any way?

The following headings should help as a guideline as to the sort of things you should bethinking about when you start designing.

1) Who is my automata intended for? A small child, 12-14 year old or adult etc?

2) What size will it be? Automata can range from miniature pieces for dolls houses, through to hand held ones or large scale works.

3) Simple or complex? One golden rule is to keep things simple, but even simple automata can get complicated.

4) What materials do I want to work in? Automata can be made in paper, wood, or metal. Often you will work in a range of materials.

5) Deadlines: How long have I got to make it?

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DESIGN & CONSTRUCTIONWhere to startKnowing how the mechanisms work and whatmovements they are capable of making is ofgreat importance when it comes to designingyour automata.But just how do you come up with ideas andmake them work? This section looks at thedesign process and gives suggestions andideas on which to base your own work.It is a considerable challenge to design andmake automata, so keep in mind two goldenrules:

1) KEEP IT SIMPLE

2) MAKE IT INTERESTING

These two design criteria are useful to baseall your work against. If the designs pass thissimple test then go on and make them.Look for inspiration from the people andthings happening around you. The animalkingdom is a very rich source of ideas, andcan be a good point from which to start yourown work.The following section runs through thecomplete process of designing and makingtwo automata. This should help give you aninsight to the principles to follow and theproblems you may encounter, as well as waysto find solutions.

The FrogStage 1) InspirationThe inspiration for this automata came from arubber that goes on to the end of a pencil.Frogs have interesting features as well as anexciting way of getting around which is verydistinctive and relatively simple to emulate.

Stage 2) ResearchThis is one of the most important processes. Ifyou want to get the best out of your automatathen this is the stage you need to get right.Begin by producing an “Ideas Sheet”. This issimply a large piece of card onto which arepasted as many images of your subject as youcan find. They can range from simple cartoonsto drawings, paintings and photos. Magazinesare a good source of material. You can takephotocopies from books and if possible try andtake some photos first-hand.From the ideas sheet start making simple linedrawings to determine the best shape andangle to work at. Simplify the shapes as youare going to work in wood or card eventually.Try and find the thing that makes a frog looklike a frog etc. (The key features of shape andform that make the frog or your subjectrecognisable).The next thing to do is try and simplify themovement of the frog by looking forcharacteristic movements. (In this case ahopping or jumping movement).Finally choose the main colours to work with.In this case it was easy - Green.

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Stage 4) A Working ModelFrom the design sheets, a working model ismade out of a mixture of card and wood. Thisis the exciting part of the process where yourdrawings come to life. It is also a time fordiscovering what does and does not work.You can save a lot of time and energy byproducing a working model even though thetemptation is to go ahead and start on thefinal one.

A number of things came out from thisworking model that were not apparent in thedrawing. One is that the crank handle needsto be bigger so that children with small handscan turn it easily. Secondly the frog needs tobe double sided. This will enable left and righthanded children to use it.

DESIGN & CONSTRUCTIONStage 3) DesignThis is the stage where you make decisionsabout size and colour, and begin to devise thesimplest mechanism which will make yourautomata work.The first thing to establish is a “User Profile”.Simply put, decide who the automata isintended for, i.e. children or adults. The frogautomata or mechanical toy is intended foryoung children aged 3 upwards. This nowmeans designing something which is strong,durable and with no sharp edges or smallpieces that could break off. It also needs to becolourful and slightly cartoon like (whimsical).With this information you can begin designing. The frog needs to move up and down, whichprovides a choice of two mechanisms - a camor crank. The cam in this instance seems thebest choice. The crank could be adapted butwould make the mechanism morecomplicated.The next decision is what sort of cam to use.A single lobe would give one big jump, atriangle or square would give a faster action.Earlier research showed that frogs jump in bigleaps, so it makes sense to go for a singlelobe cam. Small children should be able tofollow the action better if it is slower.

The basic design is starting to look like this.There are still a lot of problems to resolve, butdrawing ideas helps to clarify the designprocess.

The next task is to finalise the design as aworking drawing. At this point decisions aboutthe mechanisms, the box they are housed inand the materials to work in will all be made.Next the design of the frog is developed.A “working drawing” will contain all theinformation needed in order to construct a“working model”. At this stage everything istheoretical and it should work, but problemscan still arise.

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DESIGN & CONSTRUCTIONStage 5) Evaluation and DevelopmentAfter making the initial working model it isuseful to evaluate its effectiveness and tohighlight any design problems that may stillneed to be resolved. Try working to a simplecheck list:

1) Does it work the way it was intended?

2) Can anything be improved or simplified?

3) Is it going to be reliable?

4) Does it look and move in afrog-like manner?

Inevitably, you will need to adapt some aspectof your design. Apart from a larger handleand the need to paint the frog on both sides,in this instance a much bigger problem hasbeen highlighted. The frogs legs are too longand do not leave the base when the frog is atthe top of its travel. The cam is just about asbig as it can go so a major re-think is calledfor. One possible solution would be to slightlyshorten the legs and make the cam larger.The most practical solution is to replace thecam with a crank, and the scotch yoke crankis a good choice if side to side movement isto be avoided. This makes it a morecomplicated automata than originally planned.

Stage 6) Final automataAll the design problems have, in theory, beenironed out, so the final stage is to make theautomata out of what is termed “resistantmaterials”. Wood was chosen (in particularpine which is soft and easy to cut).The final automata is assembled and painted.Most of the parts are made directly frompatterns that were produced for the workingmodel and have been tested so should workwithout any problems. The scotch yoke hasbeen substituted to provide more lift. Itworked well in card and so should be finewhen constructed in wood. Because of thenew design, the frog is attached permanentlyto the rest of the automata which makes itsafer for younger children. In this caseswitching mechanisms has proved useful,and shown how things can easily beoverlooked.Now finished, and working as intended, therewas a teething problem with one of the legssticking. This was due to the paint taking outthe free play in the joint. A bit of vigorouspush-pulling soon bedded it in.Several problems were highlighted whendesigning and constructing this simpleautomata, so take heart when you encounterproblems with your own work. There isusually a way to overcome the setbacks youmeet. The final automata works as intended and has

evolved into a more practical toy for thechildren it was intended for.

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DESIGN & CONSTRUCTIONStage 7) EvaluationThis final stage is very important and you nowneed to test against your original intentions.Below is the procedure that was run through.

1) Does it appeal to its intended user?

2) Does it work as intended?

3) Is it safe for use by the intended user?

4) Can it be improved in any way?

5) Is it going to be reliable?

6) Will any of the parts wear out too soon?

7) How easy will it be to repair if something goes wrong or breaks?

8) Were suitable materials used for the final construction?

9) Could alternative materials be used (recycling)?

10) Can it be adapted in any way?

The procedures that are followed arecommon to most designers. It is important towork in a clear and methodical manner. Thisdoes not have to be at the cost of creativitybut, if anything, should help you channel yourideas and energies towards a successfulsolution. It is worth mentioning that you facetwo problems. The first is what to make, thesecond is how to make it.I try to design and make automata that have afun aspect to them. Often they turn out assimple jokes or whimsical aspects ofeveryday life. Do not be offended in the leastif people think of your work as toys becausethat is exactly what they are; objects to playwith and stimulate the imagination.The design process is essential in order toproduce a working solution. Making automatais not easy, but it is a rewarding and satisfyingthing to do, especially when they work!As you can see from this example, things donot always go to plan. However, a thoroughapproach to the design process will help youmake successful and exciting automata.

Be prepared to have to make and modifyseveral versions of the final automata.

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DESIGN & CONSTRUCTIONThe submarineThe submarine needed to rise up and down.A simple double cam achieved this.

Mechanisms and Design processThis section looks at the process of designinga complicated automata, and takes a moredetailed look at the mechanisms.

1) Inspiration The idea for this automata wasbased on reversing objects in theirenvironment. I felt that it would be fun to seea fish taking a bath.

2) Research An ideas board was made upwith fish and baths cut out of magazines aswell as drawings from life at a local aquarium.

3) Design The initial designs came frommaking different sketches based on theresearch material. The automata needed tobe simple, so the big problem was to keep itflat yet 3D. This could be achieved by workingin layers rather like a theatre set which wouldgive the automata a feeling of depth. Having sketched out a simple diagram,objects were added in the bath to liven thingsup. At this point there was no thought of howthey would move or what mechanisms to use,so that was the next thing to resolve.In this example the mechanisms weredesigned individually and then combined atthe end of the design process.

The spiderThis needed to appear to crawl up and downout of the tap. The best way to achieve thiswas to have some fishing line on a crank,which lifted the spider up while gravity pulledit down. This meant that it had to made out ofsomething heavy, which was importantbecause the line passed at least 3 placeswhich restricted movement.

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DESIGN & CONSTRUCTIONThe duckThe duck needed to give theimpression of bobbing upand down as if on choppywater. Two cams on theinput shaft (for speed) wereplaced next to each otherand offset, giving a nicebobbing motion.

The fishThe fish needed to give an impression ofscrubbing his back, requiring a back and forthmovement. The best way to do this was bypivoting the fin and moving it up and down.The brush was then pivoted on the end of thefin. This made the brush’s movement fairlyflexible. It also needed to follow the contoursof the fish’s back, so the brush was indentedensuring it stayed in position. A Scotch yokewas used to power the fin.

The next step was to put all the mechanismstogether

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All the mechanical problems have beenresolved. A working model made in wood wasadapted for the final automata. The workingmodel showed that the brushing movementwas sufficient, but not really convincing. Acrank with a longer throw was thereforesubstituted. The other objects, duck, spider,fish and submarine were all fine, however thesecond output shaft had to be cut andsupported half way along. This was becauseit jammed the submarine and spidermechanisms something totally overlooked atthe design stage. A gear ratio of 3:1 wasused to both slow down the movement of thefish and also to add contrast to the fastbobbing duck. Overall this has been asuccess.

DESIGN & CONSTRUCTION

The illustration below shows the main crankshaft. It was made with the shaft runningthrough the cranks which kept everythingstraight whilst the glue set. Then the unwantedparts were cut away.

Waste parts

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DESIGN & CONSTRUCTIONThe last automata we looked at was fairlycomplicated, involving several mechanicalcomponents. If you break things down and donot try and be too ambitious, most things areachievable.I hope you have found this section ondesigning helpful, especially those peopleusing this book as part of the educationcurriculum and who need to help theirstudents to document the design process. While it really does pay off to do thingsthoroughly, as you get more experienced youmay well find yourself going straight into thefinal work without making a working model. There is a wealth of inspiration for ideas, butlike most creative activities you may findstarting a bit of a stumbling block.Be prepared for things to go wrong with yourfirst few automata and do not bedisheartened. Even experienced makers stillhave disasters every now and then, but learnso much from these attempts so thatsuccessive automata are much better.Personal experience has shown howfrustrating those early attempts can be. Eventhe simplest automata will need a bit of finetuning.If younger people are making automata, it isvitally important that they do not try anythingtoo complicated, as failure will quickly lead tofrustration and lack of interest.

The other thing to mention is the amount oftime it takes to make an automata. It willsurprise you just how long the whole processis, so do not rush, and allow plenty of time forplanning and making. There are many skills to learn and you mayfind you have to use a range of unfamiliartools. Also you may be working for the firsttime with wood and metal.

This automata is made from thin cardand is very strong. It was also easy to cutout and glue.

Do not overlook the properties of card, thereis not much it can not be made to do, and it isideal for younger people to work with.

The automata on the left used both wood andmetal in its construction. The tall buildings andcars were all made out of thick card.

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AUTOMATA FOR YOUNGER PEOPLEPossibilities, Problems and SolutionsThis section looks at the possibilities,problems and solutions for younger peoplemaking automata. It is important to start bystating that you should never underestimatethe capabilities of young children. However,do not encourage them to tackle too complexor ambitious work at the start. This is becausechildren, especially younger ones, can havean over-abundance of natural enthusiasm,which needs careful guidance. Properlychannelled they will be inspired andenthralled with the automata they make.Repeated failures, or work that doesn’t meetexpectations, will soon leave themuninterested in the whole process.Personal capabilities differ for every child, andmany factors, such as manual dexterity,concentration or artistic ability will have abearing on their level of skill. So as a guidethis section is divided into 2 age categories:5-7 and 7-11. There will obviously be somecrossover between the two, but splitting themhelps to identify key skill areas within eachgroup.

Younger Children 5-7The design process was covered in somedetail in the previous chapter, and this needsto be simplified for young children but can beused as the basis from which to start.Many factors come into play with youngerchildren in this age group (manual dexterityand conceptual awareness of the designprocess are, for many, likely to be fairlylimited). Help and encouragement fromadults, teachers and even older brothers orsisters will help them to achieve a higher levelof success.

Inspiration and ResearchAnimals are a great starting point for youngerchildren. They can start by cutting out animalsfrom magazines and sticking them down onan “Ideas Sheet”. You may want to theme thisi.e. farm animals, dogs, cats, or be able tocoincide this with a trip to the zoo. The bestapproach is to focus on some aspect of theanimal kingdom and then look for keymovements such as a snapping crocodile,kitten chasing its tail or frog jumping.When it comes to designing, stick to the verysimple mechanical movements such as camsand cranks. These will still produce a range ofexciting actions. Making the animal formsshould also be simplified and either kept flator constructed from simple shapes.

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AUTOMATA FOR YOUNGER PEOPLEGetting results fastYoung children want results fast, in order tokeep them interested. You may decide to skipa working model and go straight into the finalwork. This can result in some fine tuningbeing needed to get things working properly.You should test each component as it is madeso all the parts should work when combinedtogether.Working with card and paper is recommendedas these materials are easily cut and worked.Household packaging is very useful;toothpaste boxes, plastic bottles and drinkscartons, for example, can all be used toconstruct bases or animals. Simple origamianimals can also be very effective whenincorporated into automata.You may find that for very young childreneven simple cranks and cams may be toocomplex, so push-pull mechanisms can beused instead. Pecking chickens are an a oldfavourite and rely on weight and gravity toproduce movement. Pulling the string on asimple figure makes the arms and legs moveand is a very simple way of producing andlearning about movement. This is an areawell worth exploring, and can be easilyadapted for many things.The following automata make use of linkages and levers to createmovement.

This simple mechanism is very versatile. Asmentioned, the pecking chickens are an oldfavourite, but you can adapt the movement tomost things. In fact, you can replicate theaction of a simple crank, without having tomake any mechanical parts. It is thissimplicity and adaptability which makes this agreat starting point for young automatamakers.

The trick when using this technique is tomake sure that the parts you want to moveare pinned in such a way as to allow gravityto pull them down. It is also important thatthey can move freely. In the example to theleft you can see that that the pin is placedclose to the string, the neck of the chicken isquite long and so dips down, the swingingweight then pulling it up. The weight shouldbe fairly heavy; a large nut or wooden ballworks well.

The hungry diner is thumping his knife and fork as he waitsimpatiently for his dinner

Pin attaching the neckand tail to the body

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AUTOMATA FOR YOUNGER PEOPLE

The cat and monkey work byplacing two sticks of wood ofslightly different lengths on topof each other. The charactersare hinged at the ends andwhen the sticks are slid backand forth the animals leap upand down. A simple eye- screwis used to guide and hold thesticks together.

This toy uses elasticthreaded through twosticks and then crossedthrough the character’sarms (see above ).When the lower ends ofthe sticks are squeezedtogether the elasticstretches and twistswhich makes theacrobat leap up anddown depending on thepressure applied.

Using lolly sticks or something similar you cancreate a scissor like action that extends whenthe ends are squeezed together andcontracts when opened. This simple deviceis easy to make and is very effective. Themore sticks that you use, the greater thereach and more dramatic the action. Theexample below is made from lolly sticks thathave been drilled to allow split pins to join thesticks together. Two separate jaws arecentrally hinged and taped on each end,which will create the snapping action. Thiscould be adapted for different animals. Youcan substitute thick card or art straws for thelolly sticks.

Jumping Jacks can bemade from wood or card.When the string is pulled itmakes a single jerkymovement, pulling the limbsup, and then when you letgo gravity pulls them backdown. The simplest way toconstruct one is to use cardand split pins, making surethat everything can movefreely. The diagram on theleft shows how to thread thecord.

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AUTOMATA FOR YOUNGER PEOPLEOlder Children 7-11As children get older their comprehensionand dexterity improve. A consequence of thisis that individuals are able to undertake morecomplex tasks. They still need a littlesupervision, but should be able to play amuch more active role when makingautomata. As with younger children, it issuggested that they take ideas from theanimal kingdom and use them as the basisfor the first couple of automata they make.Then look at the child’s interests forinspiration; football, cars, dinosaurs, horsesetc. Remember to keep things simple. Olderchildren tend to be far more ambitious withtheir ideas, and may need help in scalingthings down to achievable levels. It isimportant to negotiate and explain why anidea needs modifying. Children must feel thatthey are playing an active role and not justbeing told what to do.You may also want to start working, in part,with resistant materials, especially with 10-11year olds. You will also find that older childrenare able to work through the design process,but keep it within their scope and make it asenjoyable and interesting as you can.Encourage them to research and design theirown automata. The drawings may be crudebut they will feel they are part of the processand in control.

You will probably have to “down size” initialideas, but this can be negotiated and used aspart of the design and evaluation process.Children enjoy drawing and find it comesnaturally. Making and painting things is a littlemore difficult as they are not everydayactivities. It takes time to make even thesimplest of automata, so try and break thingsdown into stages rather than trying tocomplete them in one session.As with younger children, you may findworking in card easier to begin with.Recycling old household objects andpackaging also offers many possibilities.Balsa wood is another malleable material,which can be easily and safely cut andsanded into shape. Although fairly soft it canbe used successfully to make the casing tohouse simple mechanisms.

Mastering MechanismsCams and cranks offer the best mechanicalprinciples for this age group. They canproduce a wide range of movements, yet arestill relatively easy to make. Simple gearing orpulleys could also be introduced for moreambitious and able students. This allows formore complex actions to take place, and canhelp slow or speed things up. Again, simplematerials can be used such as woodendowels, art straws and lolly sticks. Papier-mache and “mod rock“ make goodmodelling materials and offer a lot of scope.

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AUTOMATA FOR YOUNGER PEOPLE

As with the “pecking chickens” and“sliding sticks”, you can adapt thesemechanisms to make more sophisticatedautomata. They are still easy to make, but offermore creative scope.

This snappy lobster makes use of 2 cranksthat alternately pull the claws open. Thiscould be adapted to the pendulum mechanism

A simple crank is a good mechanism to startwith. It can be adapted in many ways toproduce exciting and lively movement. You canmake all these automata out of card and wire.

You can make good use of householdpackaging. The recycling is a very positiveaspect. The automata below use a smalldrinks carton to hold the mechanism. Florist’swire is used to make the crank and handle,while a drinking straw has been cut for use asspacers to keep the crank pins in place andmake a handle. You can adapt this to use

bigger boxes for larger automata

In this example the eelwriggles up and down aswell as side to side.

The fish are made from colouredpaper and folded origami style.They bob up and down as well as side to side. Below you can see themechanism inside the drinks carton.It is very simple and effective.

The “Bed Bug” leapsabout on top of the sheets.

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AUTOMATA FOR YOUNGER PEOPLE

The robot, above, again makes use ofa cardboard box (the robot is also made ofcard), with a simple wire crank that lifts hislegs and arms up to give him the appearanceof walking. This automata could be adaptedto other characters, andyou could even have 2 ormore figures moving.You can make a strongercrank out of thickcorrugated card and usepencils for the shafts.

The automata on the right uses a simplecam to make the owl’s beak and headsnap up and down. The con rod also linksthe wings, which act as bell cranksand give the appearance offlapping. This entire automata ismade from paper and card.The lobed cam is constructedfrom thick corrugated card. Aswith cranks you can use pencils, art strawsor wooden dowels to make the supportingshafts, cranks and con rods. Wood glue orPVA can be used to stick all the partstogether. This automata can be adapted veryeasily to make other birds such as Penguinsor Parrots, and even animals or people.

The lobed cam above is made fromcorrugated cardboard. The base ismade out of a cereal box.

This illustration shows youhow the mechanisms areconstructed. The head ishinged at the back and ispushed up by the con rod.The wings are slottedthrough the body (which actsas a pivot) and are attachedto a rod that is in turnconnected to the con rod.This provides the lift for thewings. Both the head andcam follower are assistedby gravity which provides

the downward force.

Con Rod

Cam Follower

PivotPoint

GearsOlder children can be introduced to theprincipals of gearing. They can make veryeffective gears out of lolly sticks, pencils andwooden dowel stuck tocardboard. The exampleon the right uses a ratioof 2:1 The driver has 8lolly sticks whilst thedriven gear has 16. (Thismeans that the drivengear’s circumference willhave to be twice that ofthe driver gear.) This sortof gearing is very simpleand fun to make.

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TOOLS & EQUIPMENT TOOLSYou don’t need a vast range of tools in order to make automata but there are a number of essential items you will need towork with. Power tools are great labour saving devices, but all the hand powered equivalents work well and can be better touse especially when working on small scale pieces. Below is a list of useful tools to have when working in resistant materialssuch as wood, metal or plastic.

Wood SawA small wood saw with a 12 inch blade andrough teeth (which gives a rougher cut) iscapable of cutting to any depth and is mucheasier to use on larger pieces of wood. Thisagain is an essential item.

Fret SawThis saw has a very fine, thin blade which iskept under tension so that it can not bend.The saw frame is deep, enabling you to workon larger pieces of wood. The fret saw ismainly used for cutting out intricate shapesand patterns. The blade is thin, so it iscapable of turning very sharply, giving it extraversatility. It is useful for cutting out shapessuch as animals in ply wood. A fret saw canbe used on both wood and metal (usingspecial blades) and is also essential.

Tenon sawA tenon saw is a good tool to cut wood. It hasa fine blade which cuts both hard and softwoods very cleanly. It should be used inconjunction with a wooden mitre, which helpsto hold the wood firmly and lets you cutaccurate straight or angled lines. The tenonsaw has a metal seam running along the topof the blade this gives it strength but alsolimits the depth of cut to about 10cm. Thetenon saw should handle most small scalejobs and is essential.

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TOOLS & EQUIPMENTPOWER SAWS:Power tools are great labour saving devices and can considerably reduce the time it takes to make automata. However, theydo demand a great deal of care and common sense when being used. Power saws are the most dangerous tools to workwith as mistakes can be very harmful. When working with power tools always wear safety goggles, and keep jewelleryand any loose clothing or articles away from moving parts.

BAND SAWSThe band saw is a very versatile power tool. Itenables you to cut wood in a very straight line(with the use of a mitre), and there areattachments to enable you to cut circles, oreven turn it into a scroll saw. When used witha narrow blade you can cut curved shapesand, with care and practice, quite intricateshapes can be cut out of wood, plastic andeven thin metal. It is not really practical forusing on small work .Band saws come in all shapes and sizes andare often referred to as two or three wheeltypes. This refers to the actual wheels theblade rotates around. Many come withvariable speeds, which is useful when cuttingmaterials such as perspex that need to beworked at a slower blade speed to stop itmelting and rejoining.The band saw is a very useful tool to have andsmall relatively inexpensive ones are availablefrom many tool suppliers. Although for theserious automata maker they are useful butnot essential. Children should never use one.If you do not like the idea of working with aband saw then stick to hand saws.

Scroll Saw:The scroll saw has a very fine blade that ispowered up and down at about 1400 rpm. It isthe power version of the fret saw and can cutvery intricate shapes, even to quite a smallsize.As with any power tool, avoid getting yourfingers too close to the moving parts. Thescroll saw is quite forgiving (unlike a bandsaw) but should still be used with care. Whenoperating a scroll saw your fingers are oftenvery close to the blade and it is important notto push them into the front of the part whichhas the cutting edge. However, an accidentwith a scroll saw is unlikely to cause a veryserious injury. It is this comparative safety thatmakes them popular in schools and suitablefor older children to use if closely supervised.The scroll saw can be fitted with a range ofblades and can cut wood and metal up to twoinches thick. They are extremely versatile anduseful labour saving devices. A real must forthe serous automata maker.Check the web site www.automata.co.uk fordetails of our training video.

BAND SAW

SCROLL SAW

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TOOLS & EQUIPMENT DRILLSHand drillsA good bevel gear hand drill will give you lotsof control, and is an essential item to have.You do not often have to drill deep holeswhen making automata, so hand power is nottoo exhausting. The trick to using a hand drill(in fact any drill) is to try and keep the drill bit(that's the the part that does the cutting) asvertical (90o ) to the work as possible so thatthe hole is straight. This can be a little trickywith hand drills, as they tend to wobble a bitwhen you turn the handle.

Power hand drillsPower drills are really a little too big andfierce, especially when working on smallerpieces. However, smaller battery poweredones with variable speed control can beuseful, and are much safer to work with.

Mini DrillsVariable speed (12 volt) mini drills used bymodel makers can be very useful. They takea range of specifically made accessories forcutting metal, grinding, polishing, as well asvery fine drill bits. I find them particularlyuseful on small delicate work. Their bigadvantages are size and controllability.

Pillar DrillsThe pillar drill normally has five speeds whichare changed by repositioning the drive beltonto different size pulleys. They are operatedby a handle that pulls down the drill bit. Thisgives you control over the depth of hole aswell as a straight vertical cut. The work canbe held in a vice which increases safety. Thepillar drill is a very versatile power tool, whichcan be purchased for a very good price(similar to that of a powered hand tool - but amuch safer alternative). A must have item forthe serious automata maker!

Try to keep the brill bit as straight as possibleto the work.

Correct

Incorrect

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TOOLS & EQUIPMENT When working with resistant materials youwill find it useful to have a range of smallhand tools.

Long Nose Pliers

Short nose pliers

G clamps

Wire cutters

Junior Hack Saw

Tin Snips

Small Pipe Cutter

You can make working prototypes of yourautomata or even finished work usingcard. Below is a list of equipment you willfind useful to work with:

Large and small pair of scissors

A scalpel or craft knife

A steel rule, with a handle that keeps yourfingers away from the edge

General items that you will find useful areas follows:

A compass

2B Pencil

Rubber

Masking tape

Rubber Bands

Sellotape

Wood glue (this can also be used on paperand card).

Mitre Square

Protractor

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CONSTRUCTIONAn open sided wooden box is an idealhousing for automata mechanisms, and isvery simple to make. You will need to workout the length and depth needed, then simplyglue together, placing the ends onto the baseand then the top. Wood glue sets fairlyquickly, so you only need to put pressure onthe pieces for a couple of minutes beforeletting go, or you can g-clamp them inposition.You can vary this design; if you are good atwood working you may want to dovetail jointthe box to give it a professional look.Alternatively you may want to use woodendowels to pin the sides together. Whateverconstruction method you use, this simpledesign is a good starting point.6mm pine is a nice wood to work with. Youcan, of course, use whatever is to hand, evenplywood and thick balsawood will work.Fairly thin wood can still be alright especiallyfor smaller automata but, as a rough rule, thelarger the automata you make, the thicker thebase needs to be in order to support themechanisms.

A simple 4 sided box makes an ideal housing foran automata mechanism. You can make it outof a range of materials such as cardboard orwood.

If you are good at woodwork you may want tomake simple dovetail joints to create the box.

To join the pieces together and to make astrong joint use wooden dowels, wood glue orboth.

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CONSTRUCTIONCams, gears and figuresMost components can easily be made out ofpine. It is a lovely soft wood, easily shapedand sanded which is very useful whenmodifying your cam’s shape. 6mm thick pineis fine for constructing most cams. Avoidwood with knots on the surface, these causeproblems when cutting. Do not use MDF as itproduces a harmful dust when sanded or cut.Plywood can be useful for making cams but ismost suitable for figures such as animals,people or dinosaurs. It comes in a range ofthicknesses, also referred to as “plys” orlayers. 3ply is the thinnest you can get. It isworth working with a quality plywood ascheaper ones tend to splinter very easily.

Plywood is made by gluing strips of woodtogether with their grains running in oppositedirections. This gives it tremendous strength;the more layers it has, the stronger itbecomes. For making automata, the outerwood face should be of a high quality such asbeech. This will give you a much better finish.The inner sections are often made of cheaperwood. When cutting small intricate shapes apoor quality plywood can break or split, andsmall pieces of the inner layers can fall out.Because of it’s construction plywood is verystrong, this also makes it tough to cut. Handsaws are fine on the smaller thicknesses butthicker wood may need to be cut with apower saw, if you want to produce moreintricate shapes.

If you want to produce more detailed work(which may involve whittling or wood carving),then lime is excellent to work in as it isreasonably soft but holds a good edge. Thisallows you to put in very small details. Morecomplicated characters are often made up ofseveral types of wood.If you are carving wood then make sure thatyou always cut away from yourself and holdthe work squarely in a vice. It is worth readingup on the subject and there are many goodbooks on wood carving for the beginner.

Bench Hook

Workbench Vice

A work bench offers a safe and convenientplace to work when making automata out ofwood or metal. You should also use a benchhook or vice to hold work securely whencutting or carving.

You can use a combination of woods to makedifferent parts of an automata. In the aboveexample the boat, cat and waves were made withplywood whilst the fisherman was made out of lime

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CONSTRUCTIONWorking with metalsSometimes you may want to work withmetals. Linkages are an example where thinbrass rods are very useful.The most common metals used in automataare copper, brass, tin and mild steel. All canbe easily worked and can be joined bysoldering or even gluing.Brass tubes and rods make excellent camfollowers; they are easily cut with a juniorhack saw or mini tube cutter. Thin brass andcopper sheet can be cut with scissors andformed into shape. The flying pig’s wingswere made from brass sheet. It is a veryquick and effective way of putting detail intoyour automata. I use brass for much of myown work. It is easy to bend, cut or solder andhas a lovely bright finish.

Brass wire comes in many thicknesses. 2mmis excellent for making linkages, as it caneasily be bent with long nose pliers to makehooked or circular ends.

Brass and copper tubes and rods come in allsizes. Square rods and tubes are very useful,as they can stop the turning action of the camand follower which you get with round tubing.Whichever tubing you work with make surethat the inner rod moves freely. Use graphiteas a lubricant, not oil, which causes themechanism to drag. Metal to metal contact isfine. Most automata work at a slow speedsand under fairly light loads, so friction will notbe a problem.

Be aware that when working with metal that it can have sharp edges that can cause cuts.Cutting metal can also create sharp edges. These can be smoothed down with emerypaper or a metal file.

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CONSTRUCTIONGluingThere are a number of glues that work verywell for various needs.

Wood to wood, cardboard or paper:Wood glue is a great all round adhesive. Itdries clear and sets fairly quickly. Paper andcard are wood in origin, so it works well withthem. There are many different brands on themarket; they all seem to do a good job andare readily accessible from most hardwarestores. If you can find it professional woodworking glue (which is often yellow, andsometimes referred to as aliphatic resin)gives excellent results.

Wood or metalA two-part epoxy resin is very useful as itdries in about 10 minutes and sets clear. Youthoroughly mix equal parts and, when firstmixed, the glue is fairly runny. As it begins toset, it gradually becomes stiffer until iteventually starts hardening, When stiff, youcan place it on the objects that need joining.Be watchful, as the glue very quickly turnsfrom stiff to set. Give yourself enough time towork, and only mix up as much glue as youcan use in that time.Warning: Two part epoxy resin glues containharmful chemicals. They should be used withcare, and if you get any on your skin, washimmediately with soap and water.

Two part epoxy resin glues are incrediblystrong, dry quickly and stick most things.They work very well on metal and wood, andare an invaluable aid to the automata maker.

Glue guns:Glue guns are very useful. They use sticks ofordinary or wood working glue. Be warnedthe glue is very hot when it comes out andburns if touched. However, It does coolquickly. It will join most materials together,although it does not form such a strong bondas wood glue or epoxy resign.You do not have much control over thespread of glue, so a trigger type of gun isrecommended. This at least lets you controlthe flow of glue and can be used with onehand. A glue gun will work on metal, woodcard and paper, depending on the glue stickyou select.

A useful tip for using wood glue (to make abase for example) is to put a few spots ofglue down with the glue gun and then usetraditional wood glue. The hot glue will dry inabout a minute and hold the work whilst thewood glue sets in about 15 - 20 minutes. Thiswill avoid you having to clamp the work.

Hot glue from gun

Wood glueThe secret to epoxy glues, is tomix both parts thoroughly and ineven amounts. (Always followthe manufacturers guidelines.)

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CONSTRUCTIONPaper and card gluesWood glue is excellent for bonding paper andcard but is not suitable for children to use.PVA glue is a good alternative. It takes a littlelonger to dry, but is relatively harmless andsafe for younger people to work with undersupervision. All purpose adhesive is excellentin its solvent base form. It dries very quicklyand makes a strong bond. Again this is notsuitable for children. It also comes solventfree, a form that is safe for children and workswell.

If you are working with card or paper thenthere are several glues you can use that are safeand solvent free. You can also use tape to stickthings down.

PaintingIt is often nice to finish automata by paintingthem. Acrylic paints work well, they give agood finish and are non toxic. You can alsoget craft paints made specifically for wood.They come in a gloss or matt finish (I preferthe gloss) and again give very good results.Finally a word of caution, when you paintwood with waterbased paints it invariablyswells a little. This means the parts cansometimes jam, as the free play disappears.This can be overcome by moving (easing) theparts until they move freely again.

SolderingBrass, steel and copper can all be soldered inorder to join them. There are a number ofgood quality lead free solders on the marketthat work well and are safer to use. Many alsohave a flux core that helps the solderingprocess. The soldering iron needs to behandled with care as it gets very hot, as dothe splashes of solder that can drop off theend or from the soldered parts. You shouldwear goggles and take care not to breathe inany fumes.Soldering takes a little practice, but producesa very strong bond between metals. You mustmake sure that all surfaces to be soldered areclean and grease free.

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SUMMING UPMaking automata can be challenging,frustrating, and fun. Sometimes mechanismswork well initially, but the next day they don’twork properly. Bits drop off or they fall apart.On other days everything works well andkeeps on working, so you know you arehaving a good day! Whatever you do, do it forfun. It really does get easier and, likeanything, the more practice you have thebetter you get. It is easy to be dismissive ofautomata as just whimsical toys, but they aremuch more than that. Even the simplestpiece of work can encompass a whole host ofartistic and craft skills, not to mentionengineering theory and practices. But whenyou turn the handle something magicalhappens as your work comes to life. Wehumans love movement and in this modernage we are bombarded with it, yet it stillcaptivates us. You will have triumphs and tragedies. Manyautomata makers who have been workingover a period of time have a collection of oddmechanisms and body parts which are atestament to their failures. The parts stillmaintain something special, which is enoughto keep them, and they can often be recycledinto other automata.Be proud of what you make and enjoy thewhole process. The automata you maketoday could be tomorrow’s antiques, so a littlebit of the magic can live on.

This automata called “Jungle Jimmy” wasmade out of an old plastic chair and covered inpaper pulp to form the shapes. When you turnhis tail the animals on his back jump about.

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INDEXA

Archimedes 45Axle 42

B

Ball bearing 42Bearings 42Bell Crank 20Belt 35, 38Bicycle chain 35Block 8

C

Cam 8calculate 9designing 10drop 11concentric 15follower 8friction drive 44lobed 10materials 14offset 11reciprocating 8skew 11support 8snail 10throw 15

Chain 35, 44

Crank 17crank pin 17crank shaft 17crank slider 18crank throw 17concentric crank 19eccentric crank 19fast return crank 20scotch yoke 18

DDesigncams 10gears 25ratchets 34

Design process 51Designing 52Development 53Drillsbits 72hand 72mini 72pillar 72power 72

Drives 43friction 43hand 42indirect 43positive 43

EEccentric 18Electric motors 43

Engaging 22Evaluation 55, 58

F

Follower 8Fret saw 70Friction 36Fulcrum 45

G

G-clamp 73Gears 22bevel 24parallel 24

Gear chain 22Gear trains 22Gear tooth 23Gearbox 23Gravity 20, 48, 50

H

Hand power 43Hand tools 73

I

Idler 22Input 22Inspiration 64Intermittent motion 31

J

Joining 38Jumping 35Junior hack saw 73

K

Kinetic art 79

L

Levers 45, 47Archimedes 45first order 45effort 45fulcrum 45second order 45theory 46third order 46

Linkage 39bell crank 41transfer 40transmitting 41

M

Mechanical advantage 21Metals 76, 77Mechanisms 60,67, 79Movement 49

N

Nails 24Notes 25

O

Observation 51Offset 10Offsetting 11Output 21, 43

P

Panel pins 24Pawl 31Permanent 53Pillar drill 72Plierslong nose 73short nose 73

Pivot 40Protractor 73Pulleys 35

R

Ratchets 31Reciprocating 8

S

Skew 11

Self-conjugate 11Scotch yoke 17Shaft 8Soldering 78Springs 48Sprocket 44Snail 10, 30Synchronised 30

T

Teeth 23Timing 29Tin snips 73Transmitting 41

W

Web site 2Wood glue 74Wood saw 70Working model 53

.

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