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Walk Under Guy Anchors:

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Subject: Walk Under Guy Anchors:
From: (Wendell - W5FL)
Date: Mon, 16 Dec 1996 18:37:13 -0600
I ordered the standard Rohn 45 Foldover double guy kit with the 64 foot =
tower, but want to use walk under guy anchors (instead of the 4 screw =
anchors they furnish) to get the guy wires up so I won't run into them.

Question:  Any suggestion on how to best adapt 4.5 inch pipe anchors for =
attaching the Jaw of the 1/2 in x 12 turnbuckles.? =20

I have drilled the four (4) anchor holes on a 25 foot radius as Rohn =
recommends (35 ft between anchors).  The guy anchors will be 4.5 inch od =
1/4  in wall oilfield pipe 10 feet long.  The holes are 18 inch in =
diameter and 5 1/ 2  feet deep (IN SOLID ROCK starting at 24 inches).  =
This will leave the pipe sticking out of the ground 4 1/2 feet (no rebar =
in anchor holes). I need to weld an adapter of somekind to the pipe such =
that a 1/2 inch hole can be made to mount the jaw of both 1/2 x 12 inch =
turnbuckles Rohn furnishes.  Their guyline is 1/4 inch EHS with guys at =
29 and 58 feet.  The base is 30 inches in dia x 4 1/2 feet deep (also in =
solid rock starting at about 24 inches). =20

If you want to comment on my calculation, or can find an error in them, =
I would appreciate all suggestions as I hope to pour concrete next week: =

Rohn 45 Foldover Tower at 64 feet. =20
Antenna load =3D 17 sq ft
1 set control cables & feedlines per leg (7/8 + 1/2)
Windspeed 112 mph =3D 50 psf ( I believe 30 psf is probably adequate for =
most conditions but I lost 40 sheets of plywood with roofing attached =
off my house last year in a Texas thunderstorm!)

Note:  Maximum load occurs in line with guy wire where it is 30 deg from =
guy wire for 3 guys.
Loading in top set of guys at 58 feet =3D 1713 #         (6650# breaking =
strength for 1/4 inch)
Loading in lower set at 29 feet =3D 1308 #            (Turnbuckles rated =
at 11,000# break)
Anchor uplift =3D 2347 # (about same as 150 ft tower with guys at 80% of =
Base Down Force =3D 9389 #  (Rated at 18,960#)

I guess I have to also finalize the grounding system for the tower =
before I pour concrete:  I have a lot of questions about the best way to =
ground the tower and anchors based on polyphasers book when you have =
24-30 inches of gravely/rocky soil on top of a solid rock ledge that is =
at least 9 feet thick-but that is another story.

Wendell Wyly   -   W5FL

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