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[TowerTalk] Loose tension gauge query.

To: <>
Subject: [TowerTalk] Loose tension gauge query.
From: (
Date: Tue, 13 Mar 2001 16:40:05 EST
In a message dated 3/13/01 9:14:09 AM Pacific Standard Time, writes:

> I've asked this related question before, and maybe it falls under the
>  heading of "no matter nohow," but I think it's generally understood that
>  the pretensioning of guy wires is intended to take them from
>  "take-out-the-droop" mode to "stretch" mode.  

    "Pre-tensioning" isn't a concept covered by the TIA-222-F, "Structural 
Standards for Steel Antenna Towers and Antenna Supporting Structures" which 
is the tower design bible. They do define "initial guy tension" as "the 
specified guy tension in pounds [newtons] under no wind load conditions, at 
the guy anchor at the specified temperature".

    You may be thinking of "pre-stressing" which is "the removal of inherent 
constructional looseness of the guy under a sustained load". This is 
unnecessary for small diameter guys like typically used for ham 

    When you're constructing a guyed tower, there is an initial tension that 
is a moderate amount used when the guys are first attached to the anchors so 
that you can equalize them and then plumb the tower. I use 2-3% or so (not 
critical) of the ultimate breaking strength (UBS). 

    What you're describing is just "tensioning". 

>  Since Phillystran is
>  significantly lighter than EHS, it should approach a straight line under
>  less tension than EHS does.  For that reason, couldn't it be used with less
>  pre-tensioning than EHS, giving slightly greater ultimate load capability?

    As the tension on a wire rope-type material is increased, the closer its 
characteristics get to a solid rod. Lighter doesn't make much difference and 
it has no bearing on the UBS.
>  And yes, I know that it is spoecced for the same pre-tensioning as EHS, but
>  I'm just wondering whether that's correct, or just seat-of-the-pants by
>  some spec writer...  

    Some 'spec writer' being the Telecommunications Industry Association 
which is analogous to ANSI, SAE, etc. 

    While the UBS for different sizes of EHS are widely known, the guy 
tension per temperature is not. Here's a table for guy tension that appeared 
in my column "Up The Tower" in CQ Contest magazine:

Table B: Temperature change chart for 3/16" and 1/4 " EHS guy tension
Temp F          3/16" EHS   1/4 " EHS
120 degrees 300 pounds  501 pounds
90 degrees      350 pounds  583 pounds
60 degrees      400 pounds  670 pounds
30 degrees      450 pounds  747 pounds
0 degrees       500 pounds  830 pounds

    In all things, follow the LXC Prime Directive (DO what the manufacturer 
says) and you'll be just fine. 

Cheers,   Steve   K7LXC
Tower Tech 

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