Figure 8-39 - Typical 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.
Figure 8-40. - Expansion anchor.Continue Reading