TRACKS AND TRACK FRAME

The undercarriage of the crtiwlcr-mounted dozer contains two major components: track assembly and track frame. The undercarriage (fig. 11-2) shows positive traction, allowing efficient operations.

Track Assembly

The track assembly consists of a continuous chain surrounding the track frame and drive sprocket. The links of the chain provide a flat surface for the track rollers to pass over, as they support the equipment. Track shoes are bolted to the outside of the chain links and distribute the weight of the equipment over a large surface. The distribution of the weight is the ground bearing pressure.

TRACK CHAIN.- Figure 11-3 shows a cutaway view of a section of track chain, showing the internal arrangement of the pins and bushings. As the dozer operates, the drive sprocket teeth contact the track pin bushings and propel the dozer along the track assembly.

The pins and bushings wear much faster than other parts of the track because of their constant pivoting, as the track rotates around the track frame. The pivoting results in internal wear of both pins and bushings. As the pins and bushings wear, the track lengthens. When it does, the track should be adjusted to remove any slack.

Extensive wear on the outside of bushings is a good indication of inner wear. Manufacturers have set specifications for the maximum wear allowed before a track has to be rebuilt. To determine if a track should be removed for rebuilding or replacement, measure the outside of the bushings and track pitch (length of the track). Measure the outside of the bushing at the location at which it shows the most wear using a caliper and ruler, as shown in figure 11-4. Compare this measurement with the manufacturers' specifications. Measure the

Figure ^11-3.-Track chain.

Figure 11-4.-Bushing wear measurement.

Figure 11-5.-Track pitch measurement.

track pitch with a ruler or tape measure after tightening the track to remove any slack, as shown in figure 11-5.

TRACK SHOES.- The most common track shoe is the grouser shoe, as shown in figure 11-6. This shoe is standard on crawler-mounted dozers. The extreme service track shoe shown in figure 11-7 is equipped on crawler-mounted dozers that operate primarily in rocky locations, such as rock quarries and coral beaches. Notice the grouser, or raised portion of the shoe, is heavier than the one on the standard grouser shoe.

Figure 11-6.-Standard grouser shoe.

Figure 11-7.-Extreme service track shoe.

NOTE: The grouser absorbs most of the wear and its condition can indicate when a track needs replacement or overhaul.

Track Frame

The track frame serves as a framework and support for the track assembly, rollers, front idler, recoil spring, and adjusting mechanism.