Figure 10-39.-Entering the cut.
Figure 10-40.Loading the bowl.
Figure 10-41.-Loaded bowl.
The scraper work cycle has four phases of
operation: loading, hauling, spreading or unloading,
and returning to the cut.
When loading, enter the cut with the ejector
positioned at the rear of the bowl, open the apron enough
to allow material to enter the bowl (normally 4 to 8
inches above the leading edge of the bowl), and then
lower the bowl to cut a depth of 1 to 1 1/2 inches. The
gear that the transmission is engaged in depends on the
nature of the material being cut. For light, loose
material, a relatively high gear can be used. For heavy
compacted material, a low gear is used; however, to
obtain a full load, you should use a lower gear, even in
loose material. As the scraper proceeds through the cut,
the material is loosened by the scraper cutting edges and
forced into the bowl by the forward motion of the
scraper (fig. 10-39).
NOTE: Avoid spinning the scraper tires during cut
operations. Spinning the tires is nonproductive and
causes expensive premature wear of the tires,
differential, and transmission.
The material entering the bowl boils back against the
ejector and forward against the apron (fig. 10-40). When
the bowl is filled to capacity (commonly know as heaped),
close the apron, and at the same time, raise the bowl 1 or
2 inches above the ground (fig. 10-41). On scrapers
equipped with diverter valves in the apron hoist system,
the bowl automatically starts raising, while the apron
control lever is held in the lower position. After the scraper
is fully loaded and the bowl is raised, continue to travel out
of the cut with the scraper bowl at a height that spreads out
the material that piles in front of the cutting edges.
The push cat supplies extra power to the scraper
during loading operations. When a push cat is used, it
should be positioned about 45 degrees off the lane to be cut.
The scraper should start loading before the push cat makes
a smooth contact with the rear push block (fig. 10-42).
Figure 10-42.-Push block.