CASE CONSTRUCTION 1150M - Page 141

6-WORKINGOPERATIONS
Packing
Packingmaterialsarematerialsthatsticktoorpackaroundthemovingcomponents.Tracksmustbeadjustedas
oftenasrequiredwhenworkinginthistypeofsoilcondition.
Packingmaterialscauseamismatchbetweencomponents,particularlybetweenthechainandsprocket.Thepacking
materialstightenthechaincausingincreasedstressandstrainonlinks,pins,bushings,andthecontactsurfaces
betweenmatingparts.Asmismatchoccursduetopackinginthesprocketroot,eachtrackbushingrideshigherin
thesprocket.Thisconditioncausesrapidandsevereforwardandreversewear,andachaintosprocket“jumping”
thatisindicatedbyaloud“banging”and/or“popping”noise.Thisresultsinhighimpactloadsthatcauseadditional
wearandcracking.
Packingconditionscanalsostoprollersfromturning.Whenthishappens,thetrackchainslidesoverthatspotonthe
rollercausingaatspot.Packingmaterialsincreasetheabrasiveeffectofmostmaterialbynotallowingthematerial
toescape.Wearwillbeaccelerated.
Whenapackingproblemcontinues,installrelievedtracksprockets.
Intermittentpackingcanalsooccurbetweensomeofthesprocketteeth.Intermittentpackingcancausethetrackto
tightenedandreleaserapidly.Thiswillcausetherecoilspringtocompressandrelease.Aloud“banging”noisewill
result.
Extremereverseloading
Extremereverseloadingoccurswhenthemachinebacksuphill.Thetopofbothtrackchainsbecometight,com-
pressingtherecoilsprings.Whenthemachineisdrivenforward,aloud“banging”noisemayoccurasoneorboth
recoilspringsrelease.
TrackShoes
Theshoesmustprovideadequatetractionandotation,butshouldbenowiderthannecessary.Flotationistheability
tostayonthesurfaceofsoftgroundormud.Correctotationoccurswhenthegrouserspenetratefullyintotheground
withoutlettingthetrackshoesgobelowthesurface.
Trackshoesthataretoowidecanhaveadamagingeffectonmanyoftheundercarriagecomponents.Themiddleof
thetrackshoeisfastenedtothetracklinks,andthelinksactasafulcrumandmustabsorbortransmitanyleverageor
twistingforcesthatoccurasthemachinemovesoverunevenorrockyterrain.Alloftheothercomponents(sprockets,
trackrollersandidlers)resistandrestrictthetwistingforcesofthelinks.Thisresultsinwearanddamagecausedby
thetwistingaction.Thetwistingactioncanalsodamagethelinks,pins,bushings,andtrackplatemountinghardware.
Widetrackshoeseffects:
1.Resistancetoturning-resultsinwearontheshoecornersandtwiststhetrackchain.
2.Bending,crackingorbreakingthetrackshoes,shoehardwareandlinks.
3.Constantproblemswithlooseshoehardwarethatmakestheboltholeslarger.
4.Increasedwearonlinks,rollerangesandidlerangescausedbyaconstanttwistingofthetrackchain.
5.Decreasedpinandbushinglifeordecreasedlinklifeduetoelongatedpinandbushingbores.Thisisaresultof
thetwistedlinks.
6.PossiblelossoflubricantintheLubricatedTrackpins.Thiswillresultinearlypinandbushingwear.
Partiallycontrolledwearfactors
Speed
Unnecessaryspeedcancauseahigherwearrateonpins,bushingsandsprockets.Thefasterthespeed,thefaster
thewearrate.Highreversespeedacceleratesbushingandsprocketwear.Reversespeedsarefasterthanforward
speeds.Wearrateisafunctionofspeedanddistancetravelednotjusthoursworked.
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