AII!!!TheEngineering .Resource For Advancing Mobility 400COMMONWEALTH DRIVEWARRENDALE, PA15096 r····w (s 850462 Optimisation ofSpurGearsinaPlanetary Hub Reduction Set SeanS.Timoney University CollegeDublin Reprinted fromSP-619­ Passenger CarTransmissions International Congress &Exposition Detroit,Michigan February 25-March1,1985Downloaded from SAE International by University of New South Wales, Monday, September 17, 2018Personswishingtosubmitpaperstobeconsidered forpre­ sentation orpublication through SAEshouldsendthemanu­ scriptora300wordabstractofaproposed manuscript to: Secretary. Engineering Activity Board,SAE.ISSN0148·7191 Copyright 1985SocietyofAutomotive Engineers, Inc. Thispaperissubjecttorevision. Statements andopinions ad~ vancedinpapersordiscussion aretheauthor'sandarehis responsibility, notSAE's;however, thepaperhasbeenedited bySAEforuniformstylingandfannat.Discussion willbe printedwiththepaperifitispublished inSAETransactions. Forpermission topublishthispaperinfullorinpart,contact theSAEPublications Division.12pagebooklet. PrintedinU.S.A.Downloaded from SAE International by University of New South Wales, Monday, September 17, 2018850462 Optimisatiorn ofSpUlrGearsirnaPlarnetary HUlb RedUlctiorn Set SeanS.Timoney University CollegeDublin ABSTRACT Thispaperdescribes acomputer pro­ gramforoptimising thebending andcontact strength ofthespurgearsinaplanetary hubreduction set.Classical optimisation techniques arenotemployed because ofthe complexity oftheproblem andthenumber and variety ofconstraints encountered. Instead. theapproach described covers thecomplete design space andsuccessively filters out solutions thatdonotmeettherequired con­ straints. Thustheverylargedesign spaceisreduced toarelatively fewpossible solutions whose properties canthenbe examined bythedesigner, leaving thefinal trade-offs tohisdiscretion. THECOMPUTER PROGRAM described inthis paper wasmotivated byarequirement to up-grade anexisting vehicle hubreduction unittoaccomodate largerinputtorques. The hubisillustrated infig.1.Inthishub design thedrivecomesinonthesungear, theplanets arei.neffectidlers mounted ona carrier fixedtotheindependently suspended stubaxle,andtheroadwheelisattached to theringgear[1]'- Theunitwasoriginally designed bythe Timoney Groupwith20·involute spurteeth fortheir10tonne, 4x4Armoured Personnel Carrier. Itispresently operational ona24 tonne8x8FireCrashTender anda12tonne 4x4RapidIntervention Vehicle, bothforair­ portfireprotection. Thecurrent design has unmodified 25°involute profiles. *Numbers inparentheses designate refer- encesatendofpaper. 71Figure 1:Planetary hubreduction unitfor Timoney FireCrashTender. Theobjective istoup-grade thehub unittooperate satisfactorily invehicles of similar performance butloaded to4tonne perwheelstation. Tomaintain maximum com­ monality ofpartsitisdesired toachieve thisbychanging thenumber ofteeth,the metric module ordiametral pitch,andthe profile ofthegearsinsuchawaythatthey willberetrofitable intheexisting hubs. TheBritish Standard Institution's PD6457 [2]isanexcellent guidetotheuse ofaddendum modification withstandard geom­ etrytoolstoachieve optimum toothpropor­ tionsandtoadapt agearpairtoapre­ determined centre distance. TheuseofDownloaded from SAE International by University of New South Wales, Monday, September 17, 2018addendum modification, particularly ina planetary gearset,widens thedesign space enormously, leading toarequirement for sometypeofoptimisation. Savageetal.[3] andCarrolletal.[4]havepresented methods foroptimal design ofspurgearsets.Both papers dealtwiththedesign ofunmodified gearsandtheiraimwastominimise thecen­ tredistance foragiveninputtorque. Thedesign problem addressed heremay besummarised asfollows; giventhegear centre distanc~ theapproximate sun/ring ratio,andthemaximum rootdiameter ofthe ringgearofaplanetary system, maximise theallowable torque inputtothesungear. MAINPROGRAM CONTROL Thestrategy followed istolooparound allfeasible combinations ofgeometry, as showninf