I put up a 555 in a very windy location several years ago, and I would not
recommend trying to install a new bolt in the existing foundation. The
stress on the bolt in the wind is enormous, and even with top quality epoxy,
it might still pull out if the concrete suffered even a small crack of any
sort. The original bolts are rather long "J" bolts that go down into the
middle of the 6 foot-deep base. Your best course of action is to have a
good welding shop "move" the hole in such a way that structural integrity of
the T-bar is not compromised. Even though your proposed method might work,
it sounds more expensive.
From: Jepilot@aol.com <Jepilot@aol.com>
To: email@example.com <firstname.lastname@example.org>
Date: Sunday, March 21, 1999 5:11 PM
Subject: [TowerTalk] Rplacement stud bolt
>Problem: How to install a stud bolt in an existing concrete base.
>Background: WD5FHG and I are in the process of installing/erecting a new
>foot crankup, self supporting tower (US Tower, HDX555). This tower is
>replacing an earlier HDX555 which was destroyed when the cable broke on the
>fully extended tower. What a mess.
>The new HDX555 tower has the same type of base as the previous tower.
>stud bolts are installed in the massive concrete base, a steel T frame base
>bolted to the three stud bolts, two legs of the tower are bolted to the
>frame, and the tower is pulled up with an erection fixture to the vertical
>position. I imagine a few hundred readers have been through this process.
>However the problem arises because one of the mounting holes in the steel
>frame does not match up with the stud bolt in the concrete base. The holes
>each end of the top of the T match perfectly but the hole for the bolt at
>bottom of the T is not even close. So we propse to install a new bolt in
>existing concrete base.
>Proposed Solution: We propose to have an all thread bolt fabricated by a
>local machine shop using high quality steel (same specs used for the
>furnished studs). The stud would be 1-1/8 inch diameter and about 18
>long, threaded its entire length. A 1-1/2 inch diameter hole would be
>drilled in the concrete base about 12 inches deep which will allow the stud
>extend about 6 inches above the top of the concrete. The stud is to be
>threaded it's entire length to allow a better grip for the epoxy
>adhesive.Obviously there is 3/16 of an inch between the wall of the hole
>drilled in the base and the stud.
>Issues: What is available to hold the stud in place? In the old days,
>liquid sulphur was used for this purpose, which when cooled held the stud
>very well. I suppose there is now available some type of epoxy for this
>purpose. Any thoughts on this?
>Is 12 inches deep enough for this application? The concern is, of course,
>failure of the epoxy and/or this method of installation while the bolt is
>tension, allowing the bolt to be pulled out of the base.
>Is a 3/16 annulus too little, too much, just right, to allow adequate space
>for the epoxy to bind the bolt threads to the side wall of the hole?
>Any other thoughts? Thanks for your comments, advice and suggestions.
>Jan Rehler, W5KNZ, Corpus Christi, Texas
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