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Introductions:today,we’regoingtomakeamachinewhichcouldrun forever.
Comments:• ThisimageWikimediaCommons.
1BGAPrimaryGearsWorkshop
2minutes
Ashortintroductiontotheworkshopleaderincludingtheirworkwithgears.
Comments:Ifpossible,includea photographofyourselfinyourworkplace–aselfiewithyourproductorprojectcouldworkwell.Dobeawareofdiversityissues.
2BGAPrimaryGearsWorkshop
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.
3BGAPrimaryGearsWorkshop
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
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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.
8BGAPrimaryGearsWorkshop
Yourfirstgeartrain• Ask thechildrentobuildthetwogeartrainsintheslide
Comments
9BGAPrimaryGearsWorkshop
Calculatinggearratios• Explainthatwhenwehavetwogearsor differentsizes,onerotatesmorequickly
thantheother.• Showthevideoabove,whilstdemonstratinghowtocountthenumbersof
rotations.• Getthechildrentocountalongwithyou.• Youprobablywon’twanttoplaythroughthecompleteanimation.
10BGAPrimaryGearsWorkshop
Calculating yourowngearratios• The childrenshouldnowusetheworksheettocalculatethegearratiosofthefirst
twoexamples(ontheslide)• Theworkshopleadershouldcirculatearoundtheroomtosupportthisactivity
Feedbackanddiscussion• Onceeveryonehasananswer,collecttheanswersfrotheclass• Showtheanswersontheslideabove.
CommentsYou’llnoticethatwearen’tusingformalrationotationtodescribethegearratios.Forthissessionitsenoughtosaythattheredgearturns3timestoturntheyellowgearonce.Henceananswerof3fortheRed-Yellowtrain.We’vemadethischoicesothatthesessionisaccessibletoasmanychildrenaspossible.
11BGAPrimaryGearsWorkshop
Whymight gearratiosbeuseful?Askthequestion.Allowtimefordiscussionandfeedbackanswers.
Answersmightinclude:• Thecanchangetherotational(turning)speedofthegears• Theymovethelocationofrotation.
CommentsAparticularlygoodexampleoftheimportantofgearratioisananalogueclock.Thissectionmaybemoredidactic,youmaywanttotell(orshow)thegroupwhygearratiosareuseful.
12BGAPrimaryGearsWorkshop
Coaxial GearExplaintothechildrenthat:• Inthisgeartraintheblueandred gearsaremounted(fixed)coaxially.• Thatmeanstheyareonthesameaxle.
CommentsThisisanewpieceoftechnicalvocabulary.Besuretouseitrepeatedlythroughoutthesession.Alsotrytoprovideopportunityfortheclasstouseit.
13BGAPrimaryGearsWorkshop
Calculating gearratiofromacompoundtrain• Demonstratehowtocounttheoverallratioofthis geartrain.• Getthechildrentocountalongwithyou.
CommentsOnecommonmistakemadebychildrenhereisthattheycounttherotationsofthecoaxiallymountedgears.Forthisexercise,allthatmattersistherotationsofthethefirstandlastgearsinthegeartrain.
14BGAPrimaryGearsWorkshop
Calculating gearratiofromacompoundtrainThechildrennowbuildandcalculatetheoverallgearratiosofthesecompoundgeartrainsandmarktheanswersontheirworksheets.
15BGAPrimaryGearsWorkshop
Calculating gearratiofromacompoundtrainShowthechildrenhowtocalculatecompoundgearratiosbymultiplyingtheratiosofthepairedgears.
CommentsYoucouldmakeanothergeartrainandaskthemtocalculatetheratiousingthemethodabove.
16BGAPrimaryGearsWorkshop
Making a larger gear train• Thechildrenaregivenadiagramfromwhichtobuildasetofcompoundgears.• Inpairstheybuildtheirgeartrainandthenpairitwiththeotherontheirtable.• Onceallthesystemsarebuilt,theworkshopleadercombinesthemalltocreatea
largegeartrainofmultiplecompoundgears.
CommentsThere aretwodiagramsAandB,makesuretheseareevenlydistributedthroughouttheclass.Otherwiseyou’llhavetroublebuildingthefindmachine.
17BGAPrimaryGearsWorkshop
Ahugegearratio• Usethenextslidestocalculatethefinalgearratioofthemachinetheclasshave
built.• Thechildrenmaybeabletosuggestthenextanswer bymultiplyingthecurrent
slidebythree.
CommentsWe haveassumedthatyouhavebuiltamachineusing4ADiagramsand4BDiagrams.
18BGAPrimaryGearsWorkshop
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Ourfinalratio• Turningoncepersecond,theendgearwouldturnoncein166days.
CommentsThisisas faraswerecommendyougowithassemblingthegears(ifyouevengethere).Sinceyoucan’treallyseethegearsmovingatthisstage,it’sbesttoshiftattentiontothegearratio.
32BGAPrimaryGearsWorkshop
Whatif…• Puttogetherallthegearsacross theclass,andyou’dgetthismonster.• Turningtheinputoncepersecondagain,thisisoneturnoftheendgearinabout
27thousand years.• Joinwiththeclassnextdoor,andyou’dhavearatioof3^((3*16)+1)⋍ 2.4x10^23:
oneturnoftheendgearwouldtakemuchlongerthantheageoftheuniverse.
33BGAPrimaryGearsWorkshop
InsummaryAsk thisquestionoftheclassandallowthemtimetodiscussandthenfeedbackanswers.
34BGAPrimaryGearsWorkshop
Andfinally…Iftimepermits,askthechildrenistheyhaveanyquestionsaboutgearsor yourjob.
CommentsYoumightwanttodisplayanotherimagefromyourworkplaceonthisslidetostimulatequestionsfromthegroup.Ifyouwereabletobringanexampleofgearsfromyourworkplace,thiswouldhelpthegroupunderstandareal-worlduseofgears.
35BGAPrimaryGearsWorkshop