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[TowerTalk] Bolt torques

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Subject: [TowerTalk] Bolt torques
From: (Steve Zettel)
Date: Tue, 8 Apr 1997 12:15:46 -0700
Dear TowerTalkers,

Thanks for all your advice concerning my bout of temporary insanity that
prompted me to consider uninsulated guys on my tower. I have now returned
to my senses. Insulated they will be! But, another question rears it's head:

(I always had an "active imagination" as a child; will this change when I
grow up?)

A question that has been bugging me, and perhaps isn't readily answered, is
about a torque recommendation for the 45G leg bolts to join sections
together. None appears in the Rohn drawings, and calling Rohn didn't turn
up an answer. In fact the Rohn representative seemed rather surprised and
condescending, "We don't specify a torque value, these things are put up by
amateurs like yourself. Just tighten 'em up real snug -- not TOO tight, you
don't want to bend the legs, you know what I mean. . . " etc, etc. I tried
to explain to him that in the engineering world, WE DO specify torque
values, for just the reasons he so eloquently demonstrated trying to
verbally describe how to tighten the bolts -- it ensures consistant,
repeatable results without the danger of failure through undertightening,
or material damage through overtightening, regardless of who does the
tightening, or what "real tight" and "not TOO tight" means. I also
emphasized that I wasn't looking for one specific value, but a nominal
range for each size leg bolt. No joy. Surely there must be a torque spec
out there in the commercial world -- I can't believe that you just tell a
110 pound tower-monkey and his 230 pound tower-gorilla partner to each
"just tighten 'em tight, not TOO tight now, you know." This spec would not
be just a bolt spec, but would take into account the guage of the tower leg
and the stress required to elastically deform the leg enough for a strong
union without permanent deformation or weakening the union because of
"egg-shaping" the tower legs.

I looked through what little commerical literature I could find without
much luck, and I don't have any basic mechanical engineering texts at hand.
I have been hunting for a source for the Carrol Smith book about fasteners
(any leads appreciated for this, too). Perhaps one of the PE's in the group
has an opinion.

(A ham have an opinion???)

Thanks again for help and your patience with my many questions.

Steve Zettel  KJ7CH
Libby, MT  USA

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