[TowerTalk] torque arms or not?

[Grant Saviers]

A technique I was shown to distribute the guy forces to all legs is to 
pass the guy wire rope thru the Z brace weld above and below (e.g. right 
and left Z braces facing the leg) where the guy meets the tower.  Thus 
the guy force is transmitted to the other two legs via the Z brace rods 
rather than thru the leg welds to the Z braces.  On Rohn 65 the factory 
attachment has specially shaped u-bolts that go around the two Z braces 
that meet on a leg, so to transmit the guy loads to the other 2 legs.

I have a large shackle into that bracket with two smaller shackles to 
one of a pair of guys on two 24" faces. The guy pairs to a single anchor 
are perpendicular to the 24" face, thus resisting twist. I think 
important since there are ring rotators with large yagis that could all 
be pointed at the same azimuth, generating a significant moment on the 
tower from the wind.

On Rohn 25 a properly threaded guy wire probably works as well 
structurally, although there is some risk of wear and sharper bending of 
the wire rope than minimum specified since there is no thimble.  So 
better to do it properly for permanent towers.

Grant KZ1W

On 1/12/2017 17:04 PM, J. Hunt via TowerTalk wrote:
> Hello Roger - thank you for your post.
> I was planning the same approach.
>
> The use of torque arms (bars) does reduce tower twist, but will not eliminate it.
> Usage of a Star Guy assembly (which features 2 parallel cables per 120 degrees) provides extreme anti-twist and tower stability.
>
> A torque arm and Star Guy assembly encircles the entire tower, which dissipates the stress in the same fashion.
> With this in mind, stress on individual tower legs and the accompanying welds is greatly reduced.
> Use of thimbles protect the guy cable within these devices.
>
> ... a little of me ...
> I am also a certified tower technician, with welding endorsements.
> I have 3 years of collegiate engineering physics, 2 years of structural architecture.
> Electrical - yes, including grounding and terminations.
>
> I am contracted out occasionally by 3 different companies, from new to repair.  As towers and related equipment age, finding a qualified welder (above grade level) is few and far between.
>
>
> Respectively Submitted,
> James
> ki5dq
> --------------------------------------------
> On Thu, 1/12/17, Roger (K8RI) on TT<K8RI-on-TowerTalk at tm.net>  wrote:
>
>   Subject: Re: [TowerTalk] torque arms or not?
>   To:towertalk at contesting.com
>   Date: Thursday, January 12, 2017, 5:16 PM
>   
>   Although it's a common practice with hams, Guys should be attached to a
>   bracket, not individual tower legs.
>   It's not normally a problem, but guy brackets like ROHN sells puts no  strain on
>   an individual tower leg.  On a heavily loaded tower,(near its  wind load limit), when the guys are
>   attached to individual tower legs,   in high winds, the tower leg on the windward side takes the
>   strain. With  a guy bracket encircles the tower with the guy strain taken by the
>   bracket and converted to a downward force, putting far less strain on  the tower.
>   
>   You don't see commercial towers with the guy wrapped around a leg.
>   
>   73, Roger (K8RI)
>   
>   On 1/11/2017 11:27 AM, Steve London wrote:
>   > K7LXC wrote:
>   >
>   > Correcto mundo. In the years before the TIA-222,  ham wisdom was that
>   > the foot long or so torque arms were a necessary part of  tower  construction.
>   > Turns out that they really didn't do anything for tower  torque but were
>   > useful only by taking some of the twist out of the movement  while being
>   > climbed.
>   >
>   >
>   -----------------
>   >
>   >
>   In recent years, I have seen the suggestion that using the torque arms
>   > eliminates the possibility that the guy wires could "chew" their way
>   > through the tower bracing or legs. I could imagine this happening over
>   > a period of years as the twisting of the tower causes abrasion of the
>   
>   > tower by the guy wire. I have never heard of this actually happening.
>   >
>   > 73,
>   > Steve, N2IC
>   >
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>   --
>   
>   73
>   
>   Roger (K8RI)
>   
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