Figure 8-39Typical screw anchor.
with gripping teeth could penetrate and damage the
protective coating of guy cables and should not be
used In step A of figure 8-38, the coffing hoist is
shown in series with a dynamometer to measure the
tension. A turnbuckle is shown in position to receive
the guy tail. In step B, an additional cable grip and
hoist or tackle are attached above the cable grip shown
instep A. The lower end of this tackle is provided with
a second cable grip that is attached to the guy tail
previously threaded through the turnbuckle. The
second coffing hoist is operated until sufficient
tension is applied to cause the reading on the series
dynamometer to fall off. Step C shows the guy in final
position secured in place with clamps. With the tower
properly plumbed to a vertical position, only one guy
at a given level need be tested with the dynamometer.
On some installations, other procedures for
tensioning guys may be necessary because of the type
of guys and hardware supplied with the antenna. For
example, preformed wire helical guy grips are
sometimes used for attaching guy wires to the
adjusting turnbuckles. In such cases, the techniques
used for the guy assembly, the connection of the guy
wire to the anchor, and the tension adjustments must
be determined for the detailed installation plan or the
appropriate antenna technical manual.
Antenna design and installation plans specify the
anchor type, the location, and the hole depth required.
Anchor shafts, or rods, must project above the
grade sufficiently to keep all of the connecting guy
wire attachments free of vegetation and standing
water. Shafts and connecting attachments should be
thoroughly cleaned and then coated with a petroleum
preservative to retard the effects of weather.
SCREW ANCHOR. The screw anchor shown in
figure 8-39 may be used for temporary guying and for
anchoring guys for lightweight towers. This anchor is
installed by screwing it into the ground in line with the
direction the guy will take.
EXPANSION ANCHOR. The expansion anchor
shown in figure 8-40 is suitable for practically all
guying applications where the soil is firm. This anchor
is placed with its expanding plates in the closed
position in an auger-drilled inclined hole, not less
than 3 feet deep. The plates are expanded into the firm,
undisturbed sides of the hole by striking the expanding
bar at point B with a hammer and thereby forcing the
sliding collar downward the distance D shown in
figure 8-40. The anchor installation is completed by
backfilling the hole with thoroughly tamped backfill.
CONCRETE ANCHORS. Poured in-place
concrete anchors are normally used for high stress
applications and where multiple guys are attached to
a single anchorage.
Figure 8-40.Expansion anchor.