Figure 1-2.-Side view of crawler tractor chassis.Dozers can move from jobsite to jobsite under theirown power at slow speeds; however, this is a poorpractice and tends to shorten the operational life of thedozer. For this reason, dozers should be transported bytractor-trailer from jobsite to jobsite.TRACKS AND TRACK FRAMEThe undercarriage of the crtiwlcr-mounted dozercontains two major components: track assembly andtrack frame. The undercarriage (fig. 11-2) showspositive traction, allowing efficient operations.Track AssemblyThe track assembly consists of a continuous chainsurrounding the track frame and drive sprocket. Thelinks of the chain provide a flat surface for the trackrollers to pass over, as they support the equipment. Trackshoes are bolted to the outside of the chain links anddistribute the weight of the equipment over a largesurface. The distribution of the weight is the groundbearing pressure.TRACK CHAIN.— Figure 11-3 shows a cutawayview of a section of track chain, showing the internalarrangement of the pins and bushings. As the dozeroperates, the drive sprocket teeth contact the track pinbushings and propel the dozer along the track assembly.The pins and bushings wear much faster than otherparts of the track because of their constant pivoting, asthe track rotates around the track frame. The pivotingresults in internal wear of both pins and bushings. As thepins and bushings wear, the track lengthens. When itdoes, the track should be adjusted to remove any slack.11-2Extensive wear on the outside of bushings is a goodindication of inner wear. Manufacturers have setspecifications for the maximum wear allowed before atrack has to be rebuilt. To determine if a track should beremoved for rebuilding or replacement, measure theoutside of the bushings and track pitch (length of thetrack). Measure the outside of the bushing at the locationat which it shows the most wear using a caliper and ruler,as shown in figure 11-4. Compare this measurementwith the manufacturers’ specifications. Measure theFigure 11-3.—Track chain.
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