I am a retired engineer (a nuclear engineer to be
specific, sort of a mechanical engineer with more
calculus and physics classes). My engineering
common sense told me that cable stiffness that
differed from the stiffness of the cable used to
calibrate a Loos PT-2 type tension gage would
result in an error in measured tension. I was
curious as to how much so a couple years ago I did
an experiment using a Loos PT-2. I connected a
piece of Loos 3/16" SS 1x19 302/304 wire ( type
that Loos says the PT-2 is calibrated for) to a
length of ROHN 3/16" EHS. I tensioned the
assembly with a come-a-long and a big game scale
between two big maples in the back yard. I set
the tension to 400# on the scale and measured the
tension on the Loos SS cable with the PT-2 at very
close to 400#. With the same tension on the
assembly I moved the PT-2 to the 3/16" EHS and
read a tension on the PT-2 of 500# (the game scale
still showed 400#). I then relaxed and
re-tensioned the assembly several time to check
the repeatability of the results. The results
were quite consistent. I reached the conclusion
that at the recommend 400# of tension ( ROHN
recommendation) a PT-2 will read 500# on their
3/16" EHS cable. I didn't bother to check the
error at differing tensions since the only tension
of concern was 400#. Common sense says the
greater the tension, the less the difference in
cable stiffness will affect the measurement.
73,
Dale AA1QD
Message: 6
Date: Thu, 28 Jan 2016 09:04:23 -0500
From: Steve Maki <lists@oakcom.org>
To: towertalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] [Bulk] Re: I think it
might be worth
investing in a guy wire tension gauge
Message-ID: <56AA1FE7.5040107@oakcom.org>
Content-Type: text/plain; charset=windows-1252;
format=flowed
Of course at low tensions the difference is large.
As you tighten the
cable, the cable stiffness becomes less of an
influence.
I'm looking at the chart for my Penn-Tech TM-800.
For the wire sizes
where it give both 1x7 and 1x19 conversion
factors, such as 9/16", the
difference between the two construction types
becomes vanishingly small
as you approach the 10% initial tension point,
which for 9/16" is 3500 lbs.
-Steve K8LX
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