[TowerTalk] Screw Anchor "Tripleye" Heads

[John Langdon]

The Chance anchors are widely used, but are usually put in by one of their
installers, who sample the soil and twist the anchors in and have the
equipment to confirm the calculated holding strength in your soil.  I would
not consider installing them yourself.  

73 John N5CQ

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Byron
Tatum
Sent: Wednesday, June 25, 2014 1:25 PM
To: TowerTalk at contesting.com
Subject: [TowerTalk] Screw Anchor "Tripleye" Heads

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
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk