Introductions: today, we’re going to make a machine which ... · BGA Workshop Presentation...

Introductions:today,we’regoingtomakeamachinewhichcouldrun forever.

Comments:• ThisimageWikimediaCommons.

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2minutes

Ashortintroductiontotheworkshopleaderincludingtheirworkwithgears.

Comments:Ifpossible,includea photographofyourselfinyourworkplace–aselfiewithyourproductorprojectcouldworkwell.Dobeawareofdiversityissues.

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4-5 minutes

Questions:• Have youheardtheword‘gears’before?• Canyoutellyourpartnerwhatyouknowaboutgears?• Canyourtablelistasmanyplacesastheycanthatusegears?

Comments:• You’lllikelybesurprisedbyhowmuchchildrenalreadyknow,orthinktheyknow.• Thisdiscussionalsosetsaprecedentofpairs/table/groupwork,andallowsyou

topracticehowyou’regoingtoregainattentionfromtheclass.Thisisagoodtimetotellthem:“WhenIraisemyhand,thatmeansI’dlikeyoureyesthisway,please,”orsimilar.

• Thisisalsogoodtimetoestablishassistancefromteachersandteachingassistants.They’llverylikelycirculatetablesandfacilitatediscussion,butdopromptthemifnecessary.

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About2minutesforalltheseexamples.

Bicycles• Wefindgearingsystemsonbicycles.• Thesearesimilartothegearswe’llexploretoday.• They arealsodifferent,becausetheyarelinkedbyachain.

Comments• Beconversationalthroughthis– childrenwilllikelycontributetheirideasand

knowledgeasyougoalong.Ifyoucan,incorporatetheirthoughts.• Respondpositivelywhereyoucan.”Icanseewhyyoumightthinkthat”isbetter

than“That’swrong”• Don’tbeafraidofsaying‘mechanicalengineering.’

Comments:• Thisimage:JonathanSanderson,NorthumbriaUniversity

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Gearsincars• Youmayalsoknowaboutgearsincars.• Doyourecogniseoneof these?• Doesitlooklikethegearsonabicycle?

Comments:• Thisimage:JonathanSanderson,NorthumbriaUniversity

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A gearbox• Thegearleverinthepreviousslideactuallycontrolsagearbox• Agearboxallowsthecar’senginetodrivethewheelsatdifferentspeeds• Youmighthavenoticedyourparents/carerschanginggearwhentheydrivearound

town• Whenacargetsfaster,yourparents/carersmightchangegear

Comments:• ThisimageWikimediaCommons:

https://commons.wikimedia.org/wiki/File:Cambio_H.jpg• We’dloveanalternative(better)photographfromaBGAmember!Pleasecontact

nustem@northumbria.ac.uk

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Ananalogueclock• Ananalogue clock– onewithhands– isdrivenbyamotor• Gearsareusedtoturn(rotate)thehandsatdifferentspeeds

Comments• Mechanical clocksareareallyusefulexample:it’scleartoeveryonethataclock

withhandswhichallmoveatthesameratewouldbeuseless.• Image:CC-BYfromFlickruserInfinityInstruments,

https://www.flickr.com/photos/75680924@N08/6976339493

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Handoutthegearkits,topairsofstudents.

ExploringgearsTaketheitemsoutofthebox/bag• Canyouworkouthowtheyfittogether?• Canyouworkouthowtheymove?• Putsometogetherandseewhatyoucanfindoutaboutgears.

FeedbackAsktheclassforfeedbackonwhattheyhavelearned fromtheirexplorationThismayinclude,andshouldbedrawnoutduringthediscussion:• Useofthewordturnorrotation• Discussionofrotationaldirection– clockwiseandanticlockwise• Descriptionofthegearsfitting(meshing)together• Descriptionofgearsmovingatdifferentspeedswhenturned

Comments• We’ve includedimageshereasahint– withoutthem,groupstendtomakeaxles

withwheels,orspinningtops,or…anythingbutgearsmeshingtogether.

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Yourfirstgeartrain• Ask thechildrentobuildthetwogeartrainsintheslide

Comments

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Calculatinggearratios• Explainthatwhenwehavetwogearsor differentsizes,onerotatesmorequickly

thantheother.• Showthevideoabove,whilstdemonstratinghowtocountthenumbersof

rotations.• Getthechildrentocountalongwithyou.• Youprobablywon’twanttoplaythroughthecompleteanimation.

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Calculating yourowngearratios• The childrenshouldnowusetheworksheettocalculatethegearratiosofthefirst

twoexamples(ontheslide)• Theworkshopleadershouldcirculatearoundtheroomtosupportthisactivity

Feedbackanddiscussion• Onceeveryonehasananswer,collecttheanswersfrotheclass• Showtheanswersontheslideabove.

CommentsYou’llnoticethatwearen’tusingformalrationotationtodescribethegearratios.Forthissessionitsenoughtosaythattheredgearturns3timestoturntheyellowgearonce.Henceananswerof3fortheRed-Yellowtrain.We’vemadethischoicesothatthesessionisaccessibletoasmanychildrenaspossible.

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Whymight gearratiosbeuseful?Askthequestion.Allowtimefordiscussionandfeedbackanswers.

Answersmightinclude:• Thecanchangetherotational(turning)speedofthegears• Theymovethelocationofrotation.

CommentsAparticularlygoodexampleoftheimportantofgearratioisananalogueclock.Thissectionmaybemoredidactic,youmaywanttotell(orshow)thegroupwhygearratiosareuseful.

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Coaxial GearExplaintothechildrenthat:• Inthisgeartraintheblueandred gearsaremounted(fixed)coaxially.• Thatmeanstheyareonthesameaxle.

CommentsThisisanewpieceoftechnicalvocabulary.Besuretouseitrepeatedlythroughoutthesession.Alsotrytoprovideopportunityfortheclasstouseit.

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Calculating gearratiofromacompoundtrain• Demonstratehowtocounttheoverallratioofthis geartrain.• Getthechildrentocountalongwithyou.

CommentsOnecommonmistakemadebychildrenhereisthattheycounttherotationsofthecoaxiallymountedgears.Forthisexercise,allthatmattersistherotationsofthethefirstandlastgearsinthegeartrain.

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Calculating gearratiofromacompoundtrainThechildrennowbuildandcalculatetheoverallgearratiosofthesecompoundgeartrainsandmarktheanswersontheirworksheets.

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Calculating gearratiofromacompoundtrainShowthechildrenhowtocalculatecompoundgearratiosbymultiplyingtheratiosofthepairedgears.

CommentsYoucouldmakeanothergeartrainandaskthemtocalculatetheratiousingthemethodabove.

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Making a larger gear train• Thechildrenaregivenadiagramfromwhichtobuildasetofcompoundgears.• Inpairstheybuildtheirgeartrainandthenpairitwiththeotherontheirtable.• Onceallthesystemsarebuilt,theworkshopleadercombinesthemalltocreatea

largegeartrainofmultiplecompoundgears.

CommentsThere aretwodiagramsAandB,makesuretheseareevenlydistributedthroughouttheclass.Otherwiseyou’llhavetroublebuildingthefindmachine.

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Ahugegearratio• Usethenextslidestocalculatethefinalgearratioofthemachinetheclasshave

built.• Thechildrenmaybeabletosuggestthenextanswer bymultiplyingthecurrent

slidebythree.

CommentsWe haveassumedthatyouhavebuiltamachineusing4ADiagramsand4BDiagrams.

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Ourfinalratio• Turningoncepersecond,theendgearwouldturnoncein166days.

CommentsThisisas faraswerecommendyougowithassemblingthegears(ifyouevengethere).Sinceyoucan’treallyseethegearsmovingatthisstage,it’sbesttoshiftattentiontothegearratio.

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Whatif…• Puttogetherallthegearsacross theclass,andyou’dgetthismonster.• Turningtheinputoncepersecondagain,thisisoneturnoftheendgearinabout

27thousand years.• Joinwiththeclassnextdoor,andyou’dhavearatioof3^((3*16)+1)⋍ 2.4x10^23:

oneturnoftheendgearwouldtakemuchlongerthantheageoftheuniverse.

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InsummaryAsk thisquestionoftheclassandallowthemtimetodiscussandthenfeedbackanswers.

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Andfinally…Iftimepermits,askthechildrenistheyhaveanyquestionsaboutgearsor yourjob.

CommentsYoumightwanttodisplayanotherimagefromyourworkplaceonthisslidetostimulatequestionsfromthegroup.Ifyouwereabletobringanexampleofgearsfromyourworkplace,thiswouldhelpthegroupunderstandareal-worlduseofgears.

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