Figure 10-46.-Shuttle loading.
is used where the cut is fairly long,
making it possible for the push cat to pickup two or more
scraper loads without back tracking, as shown in figure
10-47. The push cat push loads one scraper, then moves
in behind another scraper, moving parallel to the first in
an adjacent lane.
Optimum loading is an operation when loading time
and maximum output are critical. Push-loaded scrapers
should be loaded within 1 minute and within a distance
of 100 feet. More time and distance may be used to
obtain more material when the haul is long enough, and
the added material is great enough to offset hauling
fewer loads because of longer loading time.
When scrapers are backed up at the cut waiting for
push cat assistance, let the scrapers cut without attaining
a heaped load. When push cats are waiting for scrapers,
increase loading time to achieve maximum loading.
Make sure push cats use wait time to dress the cut. In
some cases, it will increase production to use a dozer
full time to dress the cut. At the end of a workday, take
the time to shape the cut for good drainage.
NOTE: Maintaining adequate drainage throughout
a cut and fill operation reduces compulsory downtime
caused by bad weather.
The rule of thumb used for computing the number
of push cats required for a scraper operation is to divide
the scraper cycle time by the push cat cycle time. When
computing cycle time for a scraper, take the total time
of loading, hauling, unloading, and return; for instance,
Figure 10-47.-Chain loading.