Page 374 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

8.36 THE WORK

FIGURE 8.26 Scraper patterns.

scraper can be straightened out to load just before it crosses the crest. However, the digging will
work the crest back and destroy the turnaround quite soon. It may therefore be wise to locate it
well back from the crest.
Whenever possible, a turning place should be wide enough for the machines using it to get
around without backing. Space requirements vary greatly in different sizes and types of scrapers.
Time may be saved, and accidents reduced, by providing more space than the minimum require-
ment, particularly for sharp-turning models.
A big scraper will need 30 to 50 feet to make a U turn (180 degrees) on good ground, up to 80
feet on bad footing. If it is not possible to grade enough space for a full turn where it is needed,
the machine must back one or more times, or go on until space is available.
The bottom of a cut for a four-lane undivided highway will usually allow somewhat more than
tight turn space for a scraper; two-lane cuts may not permit a nonstop turn. Wider roads and the
upper parts of any deep cut will allow ample space.

Deadheading. If the cut and/or the fill are too narrow for turns, or there are traffic difficulties,
the scrapers will go past the work areas to a turnaround. The extra travel is called deadheading
when traveling empty and is usually for only short distances.
At the cut the trip to the turnaround will be made in one direction at full travel speed, except
for any necessary slowing for traffic, while the return will be at the speed of the turn or only
slightly better, because of lack of space for acceleration. Beyond the fill the turn will be
approached at dumping speed; the return from it will be a part of the empty return and will be at
full acceleration if traffic allows.
Deadheading distances are often increased unnecessarily by careless dumping or loading that
leaves the fill or cut too rough for a turn, or by placing too many grade stakes to permit turning in
the work area.