Figure 1-2.-Side view of crawler tractor chassis.
Dozers can move from jobsite to jobsite under their
own power at slow speeds; however, this is a poor
practice and tends to shorten the operational life of the
dozer. For this reason, dozers should be transported by
tractor-trailer from jobsite to jobsite.
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.
11-2
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.
