[TowerTalk] Screw Anchor "Tripleye" Heads

[Byron Tatum]

Hello-
( Preface: I will be the first to admit that I do not wish to get outside of any manufacturer ratings and make improper substitutions. This post is only to receive comment and to try and learn something that I may be overlooking or have not thought about.)
   I am considering using some of the Hubbell (AB Chance) extra heavy duty helical anchors for a 120' tower. These are screw type anchors with a 14" auger and 1-1/4" rod 8' long, grade A-575 (select forged) steel with the forged "tripleye" end connection. I am studying using them in concrete guy anchors,and how to interface between the "tripleye" end and 3 guy wires terminations ( 5/8" turnbuckles). I will be the first to say "why not just use the Rohn concrete guy anchors" but the particular ones I want (GAC5655top with 1-1/4" rod grade A-572-50 steel) will cost almost $1000.00 for a set of 3 shipped to me. The AB Chance anchors with 1-1/4" rods are of comparable low-alloy high strength steel, hot dipped galvanized and cost from 61.00  (10" helix) to 99.00 (14" helix) and are available locally.
         To interface to the set of 3 guy wires I am considering using one of the Crosby high strength alloy shackles, but it appears to me from studying the tripleye drawings that to attach a shackle of any size to the tripleye I will need to put the bolt of the shackle through the tripleye. It would seem better to have the curved part (bow) of the shackle engaging the tripleye, but it appears from drawings that a 5/8", possibly 3/4", shackle may be the largest one I could get on in this fashion. If I went this route I could install an equalizer plate on the 0.88" diam bolt of the 3/4" shackle, if it will fit on tripleye. A 3/4" alloy Crosby shackle would provide a 15,400# working load, proofed to 2 x working load, ultimate strength of 4.5 times working load.
   To use a larger shackle, from studying drawings of tripleye, it appears I could get a bolt of about maximum 1-1/4" diam through it, so that would alloy me to use a maximum of 1-1/8" shackle (over 30,000# working load). The anchor manuf (Hubbell) actually supplies an extension rod that has a clevis end with a 1" diam bolt that attaches to the tripleye. Although this is of no use to me, it shows that it is acceptable to pass a bolt through the tripleye and retain strength ratings. I was trying to avoid removing the tripleye as it is forged onto the rod and the manuf states it is stronger than the rod itself. Is it acceptable to use a large shackle as an "equalizer", with smaller shackles, of appropriate rating, connecting the 3 individual turnbuckles to the larger shackle? It appears this could be done without creating any off-angle, side or other such loads that can de-rate on any part of the system. Crosby states in their specs that
 single-point loads on the bow of the shackle are acceptable to full ratings. Another question is in order to do this the tripleye would need to be oriented horizontally (normally it would be oriented vertically), in order for the bow of the shackle to be oriented vertically. Someone may say that by the time you add up the cost of shackles the cost savings may not be so great, however I have a large collection of shackles here in my tower hardware inventory.
      I have thought about attaching a set of equalizer plates to the tripleye using a large high strength bolt, such as 1-1/4", with each equalizer plate half being 1/4" steel. What I do not like about this is the large size of the tripleye, requiring a spacing of well over 2" of the equalizer plate halves. This may not be an issue if I use large enough high strength bolts in the equalizer plates to attach turnbuckle eyes to, and spacers to keep the turnbuckles centered over bolts.
    I studied some installations of towers well over 100' tall using the larger helical anchors holding in soil (as depicted in pictures on internet), with various types of shackles attached to tripleye, so that prompted me to study this.
    Thank you, Byron WA5THJ