Gyromonorail.docx

Gyromonorail.docx

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Gyromonorail

Gyromonorail

Thisarticlemaycontainoriginalresearch.Pleaseimproveitbyverifyingtheclaimsmadeandaddingreferences.Statementsconsistingonlyoforiginalresearchmayberemoved.Moredetailsmaybeavailableonthetalkpage.（February2008）

Thegyromonorail,gyroscopicmonorail,gyro-stabilizedmonorail,orgyrocaralldenoteasingleraillandvehicle,roadorrail,whichusesthegyroscopicactionofaspinningwheel,whichisforcedtoprecess,toovercometheinherentinvertedpenduluminstabilityofbalancingontopofasinglerail.

Brennan'sMonorail

ThemonorailisassociatedwiththenamesLouisBrennan,AugustScherlandPiotrSchilovski,whoeachbuiltfullscaleworkingprototypesduringtheearlypartofthetwentiethcentury.AnimprovedversionwasdevelopedbyErnestF.Swinney,HarryFerreiraandLouisE.SwinneyintheUSAin1962.ThissystemiscalledtheGyro-Dynamicsmonorail.

Thegyromonorailhasneverdevelopedbeyondtheprototypestage.

TheprincipaladvantageofthemonorailcitedbySchilovskiisthesuppressionoftheHuntingoscillation,whichwasaspeedlimitationencounteredbyconventionalrailwaysatthetime.Also,sharperturnsarepossiblecomparedtothe7 kmtypicalofmodernhigh-speedtrainssuchastheTGV,becausethevehiclewillbankautomaticallyonbends,likeanaircraft,[1]sothatnolateralcentrifugalaccelerationisexperiencedonboard.

Amajordrawbackisthatmanycars-includingpassengerandfreightcars,notjustthelocomotive-wouldrequireaconstantlypoweredgyroscopetostayupright.

Unlikeothermeansofmaintainingbalance,suchaslateralshiftingofthecentreofgravityortheuseofreactionwheels,thegyroscopicbalancingsystemisstaticallystable,sothatthecontrolsystemservesonlytoimpartdynamicstability.Theactivepartofthebalancingsystemisthereforemoreaccuratelydescribedasarolldamper.

Historicalbackground

Brennan'smonorail

Theimageintheleadersectiondepictsthe22tonne（unladenweight）prototypevehicledevelopedbyLouisPhilipBrennanCB[2].Brennanfiledhisfirstmonorailpatentin1903.

Hisfirstdemonstrationmodelwasjusta2 ft6inby12 inch（762 mmby300 mm）boxcontainingthebalancingsystem.However,thiswassufficientfortheArmyCounciltorecommendasumof£10,000forthedevelopmentofafullsizevehicle.ThiswasvetoedbytheirFinancialDepartment.However,theArmyfound£2000fromvarioussourcestofundBrennan'swork.

WithinthisbudgetBrennanproducedalargermodel,6 ft（1.83m）longby1 ft6in（0.46m）wide,keptinbalancebytwo5 inch（127 mm）diametergyroscoperotors.ThismodelisstillinexistenceintheLondonScienceMuseum.ThetrackforthevehiclewaslaidinthegroundsofBrennan'shouseinGillingham,Kent.Itconsistedofordinarygaspipinglaidonwoodensleepers,withafiftyfootwireropebridge,sharpcornersandslopesuptooneinfive.

Brennan's1909PatentPneumaticServo

Brennan'sreducedscalerailwaylargelyvindicatedtheWar

Department'sinitialenthusiasm.However,theelectionin1906ofaLiberalgovernment,withpoliciesoffinancialretrenchment,effectivelystoppedthefundingfromtheArmy.However,theIndiaOfficevotedanadvanceof£6000.0in1907,todevelopthemonorailfortheNorthWestFrontierregionandafurther£5000.0wasadvancedbytheDurbarofKashmirin1908.ThismoneywasalmostspentbyJanuary1909,whentheIndiaOfficeadvancedafurther£2000.0.

On15October1909,therailcarranunderitsownpowerforthefirsttime,carrying32peoplearoundthefactory.Thevehiclewas40 ft（12.2m）longand10 ft（3m）wide,andwitha20 hp（15 kW）petrolengine,hadaspeedof22 mph（35 km/h）.Thetransmissionwaselectric,withthepetrolenginedrivingagenerator,andelectricmotorslocatedonbothbogies.Thisgeneratoralsosuppliedpowertothegyromotorsandtheaircompressor.Thebalancingsystemusedapneumaticservo,ratherthanthefrictionwheelsusedintheearliermodel.

Thegyroswerelocatedinthecab,althoughBrennanplannedtore-sitethemunderthefloorofthevehiclebeforedisplayingthevehicleinpublic,buttheunveilingofScherl'smachineforcedhimtobringforwardthefirstpublicdemonstrationto10November1909.Therewasinsufficienttimetore-positionthegyrosbeforethemonorail'spublicdebut.

TherealpublicdebutforBrennan'smonorailwastheJapan-BritishExhibitionattheWhiteCity,Londonin1910.Themonorailcarcarried50passengersatatimearoundacirculartrackat20 mph.PassengersincludedWinstonChurchill,whoshowedconsiderableenthusiasm.Althoughaviablemeansoftransport,themonorailfailedtoattractfurtherinvestment.Ofthetwovehiclesbuilt,onewassoldasscrap,andtheotherwasusedasaparkshelteruntil1930.

Scherl'scar

JustasBrennancompletedtestinghisvehicle,AugustScherl,aGermanpublisherandphilanthropist,announcedapublicdemonstrationofthegyromonorailwhichhehaddevelopedinGermany.ThedemonstrationwastotakeplaceonWednesday10November1909attheBerlinZoologicalGardens.

Scherl'sMonorailCar

Scherl'smachine[3],alsoafullsizevehicle,wassomewhatsmallerthanBrennan's,withalengthofonly17 ft（5.2m）.Itcouldaccommodatefourpassengersonapairoftransversebenchseats.Thegyroswerelocatedundertheseats,andhadverticalaxes,whileBrennanusedapairofhorizontalaxisgyros.Theservomechanismwashydraulic,andpropulsionelectric.Strictlyspeaking,AugustScherlmerelyprovidedthefinancialbacking.TherightingmechanismwasinventedbyPaulFröhlich,andthecardesignedbyEmilFalcke.

Althoughwellreceivedandperformingperfectlyduringitspublicdemonstrations,thecarfailedtoattractsignificantfinancialsupport,andScherlwroteoffhisinvestmentinit.

[edit]Schilovski'swork

FollowingthefailureofBrennanandScherltoattractthenecessaryinvestment,thepracticaldevelopmentofthegyro-monorailafter1910continuedwiththeworkofPiotrSchilovski[4],aRussianaristocratresidinginLondon.HisbalancingsystemwasbasedonslightlydifferentprinciplestothoseofBrennanandScherl,andpermittedtheuseofasmaller,moreslowlyspinninggyroscope.Ratherthandevelopingarailvehicle,hedesignedagyrocarwhichwasbuiltbytheWolseleyMotorCompanyandtestedonthestreetsofLondonin1913.Sinceitusedasinglegyro,ratherthanthecounter-rotatingpairfavouredbyBrennanandScherl,itexhibitedasymmetryinitsbehaviour,andbecameunstableduringsharplefthandturns.Itattractedinterestbutnoseriousfunding.

[edit]Post-WorldWarIdevelopments

In1922theSovietgovernmentbeganconstructionofaSchilovskymonorailbetweenLeningradandTsarskoeSelo,butfundsranoutshortlyaftertheprojectwasbegun.

In1929,attheageof74,Brennanalsodevelopedagyrocar.ThiswasturneddownbyaconsortiumofAustin/Morris/Rover,onthebasisthattheycouldsellalltheconventionalcarstheybuilt.

[edit]Principlesofoperation

[edit]Basicidea

Thevehiclerunsonasingleconventionalrail,sothatwithoutthebalancingsystemitwouldtoppleover.

Basicprinciple

Aspinningwheelismountedinagimbalframewhoseaxisofrotation（theprecessionaxis）isperpendiculartothespinaxis.Theassemblyismountedonthevehiclechassissuchthat,atequilibrium,thespinaxis,precessionaxisandvehiclerollaxisaremutuallyperpendicular.

Forcingthegimbaltorotatecausesthewheeltoprecessresultingingyroscopictorquesabouttherollaxis,sothatthemechanismhasthepotentialtorightthevehiclewhentiltedfromthevertical.Thewheelshowsatendencytoalignitsspinaxiswiththeaxisofrotation（thegimbalaxis）,anditisthisactionwhichrotatestheentirevehicleaboutitsrollaxis.

Thisfundamentalbehaviourisbestillustratedbyatoygyro.

Ideally,themechanismapplyingcontroltorquestothegimbaloughttobepassive（anarrangementofsprings,dampersandlevers）,butthefundamentalnatureoftheproblemindicatesthatthiswouldbeimpossible.Theequilibriumpositioniswiththevehicleupright,sothatanydisturbancefromthispositionreducestheheightofthecentreofgravity,loweringthepotentialenergyofthesystem.Whateverreturnsthevehicletoequilibriummustbecapableofrestoringthispotentialenergy,andhencecannotconsistofpassiveelementsalone.Thesystemmustcontainanactiveservoofsomekind.

Intheinterestsofsafety,theactuationwouldbedesignedsuchthatfailurescausetheservoto‘float’andapplyminimalforcestothegimbal,givingtimetostopthevehiclebeforethesituationbecomesserious.

[edit]Passivebehavior

Inordertoassesshowthevehiclewouldrespondintheeventofservofailure,weneedtoconsiderhowthebalancingloopbehaveswithoutaservo.

Thevehicle/gimbal/gyrosystemdescribedaboveisessentiallyaspinningtopwithtopplingmomentappliedinoneplanebutnottheother.Themotionisdescribedastwooscillations—ahighfrequencynutationmode,andalowfrequencyprecessionmode.Withnofeedbackatalltothegimbal,thegyroisjustdeadweight,sothevehiclewouldsimplytoppleover.

Thetopplingmomentonaspinningtopincreasesasthetopdisplacesfromtheverticalandtendstoincreasethedisplacementfurther.Therollingmomentonthemonorailvarieswithrollangleinasimilarfashion,butafreegimbalhasnomomentappliedtoit.

Inordertoemulatethespinningtop,themomentonthegimbalmustalsotendtoforcethegimbalfurtherawayfromtheequilibriumposition—thegimbalmountingmustbeunstable.Thiscouldbearrangedusingatogglemechanism,suchasistypicallyusedinabathroomlightswitch.T