Gyromonorail.docx
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Gyromonorail
Gyromonorail
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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