>> P.62
1-4BearingSelection(12)PreloadandloadPreloadmethodsandpreloaddirectionsThebearingpreloadmethodsareshowninFig.12-2"Fixedpositionpreload"andFig.12-3"Constantpressurepreload."Aswell,thepreloaddirectionsareshowninFig.12-4"Duplexfacetoface(DF)"andFig.12-5"Duplexbacktoback(DB)."•PreloadmethodsFig.12-2FixedpositionpreloadPreloadmethodFixedpositionpreloadAdvantagesBearingsarefixedwithregardtooneanother,effectivelyenhancingrigidityDisadvantagesTemperaturechangesleadtochangingpreloadamountsduetoexpansionandcontractionofbearingsandsurroundingpartsPreloadmethodAdvantagesFig.12-3ConstantpressurepreloadConstantpressurepreloadTheuseofaspringforpreloadkeepsthepreloadamountrelativelystableevenwhenthetemperaturechangesDisadvantagesLoadontheshaftorhousingfromtheaxialdirectionchangesthepreloadamount62