280OPERATION
FootBrakeValve
Thefootbrakevalveisdirectlyconnectedtothebrakepedal.Thevalvegivesa
progressiveoutputagainstthepedaltravel.Thisallowsbettercontrolofthepressure
inthersthalfofthepedaltravel.Inthelasthalfofthepedaltravel,thepressure
outputincreaseisfaster.
Thefootbrakevalveappliestheservicebrakes,incorporatingboththeprimary
andsecondaryairsystems.Theprimarysystemcontrolstherearbrakesandthe
secondarysystemcontrolsthefrontbrakes.Thefootbrakevalvereceivesairfrom
thecompressedairtanks.Airpressureisthendeliveredtothewheelbrakechambers
asrequiredbytheamountofpressureexertedonthefootbrakepedal.Thebrake
chamberforcethenappliesthewheelbrakes.
Fromtheoperator’sviewpoint,operatingthefootbrakevalveofavehicleequipped
withairbrakesdiffersverylittlefromtheoperationofaconventionallybraked
vehicle.Becausetheoperationofthebrakepedalrequiresscarcelymoreeffortthan
depressingtheaveragethrottlepedal,airbrakesarenaturallymucheasiertocontrol.
Ifthedrivergivesfullattentiontothefollowingsuggestions,alittleexperiencewill
makehim/herthoroughlyfamiliarwiththeair-controlledbrakingofthisvehicle.
DANGER
Failuretoobservetheseprecautions
canresultinlossofvehiclecontroland
seriouspersonalinjuryordeath.
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