moved was considerably deeper than desired. Re-
First grading and inspection
Following the initial passes with the bulldozer
moval of thick layers of ice also encouraged "chat-
or V-blade and the snowblower, most of the ice
ter" or hopping of the grader, which left a choppy
surface of the Pegasus runway was still left with a
and gouged ice surface. Thus, it was necessary to
covering of snow (Fig. 32). To expose the ice and
grade the ice in more modest cuts, with 14-cm
allow close inspection of the surface, we next
layers being manageable with no ill consequences.
rough-graded the runway using the Caterpillar
The geometry of the chisel-teeth and the angle
14G grader equipped with a custom-built blade
of attack when grading are of utmost importance
edge (Fig. 33) designed to scrape the ice surface
when attempting to grade ice. Following guid-
and to shave short wavelength bumps (less than 6
ance in Mellor (1977) and somewhat by trial and
m or 20 ft). This was a somewhat laborious and
error, we manufactured the chisel-teeth on our
subjective process because the grader operator
first blade with a height of 7 cm (2.8 in.), an inter-
nal angle of 42, and with side relief angles of
needed to choose areas that clearly had high spots
about 35. The basal relief angle was a little more
and would work them until he was satisfied that
than 30 with the blade aligned perpendicular to
the surface was down no more than a few centi-
meters above its surroundings. The runway gen-
the long axis of the grader (Fig. 36). However,
erally received its first grading along the entire
when grading ice, the blade was positioned at an
angle between 27 and 33 to the direction of
length in grader-width strips, progressing from
one side to the other. When a region of bumps
travel to allow the spoil to be efficiently removed,
so that an actual relief angle of about 26.5 trailed
was identified, the grader would operate back
and forth to bring them down to a reasonable
the chisel tooth in the direction of travel. The
level before continuing work along its chosen
blade position also caused the ice to be attacked
north-south swath.
with a pointed edge of the chisel-tooth, rather
We discovered that the 14G grader, equipped
than head-on as one would normally use a wood
with the chisel-tooth blade, could remove as much
chisel or as in the case of the cutting edge on an
as 20 cm (8 in.) of ice in one pass (Fig. 34). This
ice auger. In trials on the first ice blister, we quickly
often resulted in propagating down into the ice
found the proper setup angles for the grader to
the radial cracks that are nearly always associ-
facilitate smooth and efficient ice grading.
ated with large ice blisters (Fig. 35). In some cases,
It was probably helpful that initially we oper-
a very large slice of ice was broken loose as the
ated the grader without any type of traction aids,
result of catching one of these cracks when grad-
since it forced us to discover the most effective
ing a thick layer of ice. Usually, the "divot" re-
combination of angles to minimize power and
Figure 33. Custom-built aggressive grader blade used for initial rough grading of runway.
35
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