American Rural HighwaysAgg, T. R. (Thomas Radford)
Science
American Rural Highways
Agg, T. R. (Thomas Radford)
Roads -- United States
=Slip Scraper.=--The slip scraper differs from the wheel scraper in
that the scoop is not suspended from wheels but is dragged along the
ground. It is drawn by one team and the capacity is two to five cubic
feet, but the material spills out to some extent as the scraper is
dragged along and the method is not suitable for long hauls, 100 feet
being about the economical limit.
=Fresno Scraper.=--The Fresno scraper is one form of slip scraper
requiring four horses or mules for efficient work. It differs
somewhat from the ordinary slip scraper in shape and is of larger
capacity, but is a drag type of scraper much favored in the western
states.
SHAPING TO PROPER CROSS SECTION
If a road has been graded so that the profile is satisfactory or if
the existing profile of the location is satisfactory, and the surface
is to be shaped to a prescribed cross section, either the elevating
grader or the blade grader may be employed.
=Elevating Grader Work.=--If the elevating grader is used in shaping
the earth road, the apron will be lowered and the material will be
excavated at the sides of the road and deposited on the middle
portion. If slight changes in grade are desired, wagons will accompany
the grader and catch under the apron at the high places and haul the
material to the low places. After the earth has been deposited it must
be worked over to secure the correct cross section and be made
passable for vehicles. This requires that clods be broken, weeds and
grass that are mixed with the earth be removed by harrowing and
forking and that the surface be carefully smoothed with a blade
grader. This latter operation will have to be repeated several times
before a satisfactory surface is secured. But this miscellaneous work
is highly important and under no circumstances ought to be neglected.
Nothing so detracts from an otherwise creditable piece of work as
failure to provide a smooth surface for the use of vehicles. It is
especially uncomfortable for the users of a highway if sods and weeds
in quantity are left in the road after it has been graded. The humus
that will be left in the soil as the vegetable matter decays increases
the porosity of the road surface making it more absorbent than soil
without humus. This increases the susceptibility to softening from
storm water or ground water.
The tractor can advantageously be used to draw the elevating grader on
this class of work, but will be greatly handicapped if there are wet
sections along the road, through which the tractor must be driven. In
many cases its use is prohibited by such conditions and for all-round
service of this character, mules are preferred for motive power.
[Illustration: Fig. 12.--Tractor-grader Outfit]
Public-domain text, read in full here on John Shaqi.
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