[TowerTalk] Tower guy wires / EHS size

[donovanf at starpower.net]

Dale,

Inadequate guy tension causes excessive guy catenary. Guy catenary is a function of guy tension and the weight of the guy wire and all associated hardware (e.g., insulators and guy grips).

Excessive guy catenary allows excessive tower movement during wind events.  Tower movement slackens the down wind guy(s) during wind events. Repeated slackening and tightening leads guy hardware failure.

73!
Frank
W3LPL


---- Original message ----
>Date: Wed, 25 Apr 2007 10:23:42 -0500
>From: "Dale Martin" <kg5u at hal-pc.org>  
>Subject: Re: [TowerTalk] Tower guy wires / EHS size  
>To: <towertalk at contesting.com>
>
> 
>Thanks, Frank. Good info. 
>
>I'm still curious, though.  Is there that much slack in 1/4" EHS tensioned
>to 400 lbs. -- 10% 3/16" strength?  Is it the weight of the cable
>introducing a sag that 400 lbs. tension cannot remove that wears away at the
>hardware?    
>73,
>Dale
>
>> 
>> Dale,
>> 
>> Using 1/4 inch EHS rather than 3/16 inch EHS will not be a problem.
>> 
>> Initial guy tension is normally set at 10 percent of its 
>> published breaking strength, with upper and lower limits of 
>> 15 and 8 percent.
>> 
>> Guy wire tension less than 8 percent places excessive wear on 
>> guy attachment hardware as the guy slackens and tightens 
>> repeatedly during wind events.  There have been many 
>> documented cases of guy attachment hardware failure as a 
>> result of excessive wear caused by inadequate guy tension.
>> 
>> Guy tension is excess of 15 percent of breaking strength 
>> reduces the useful load capacity of the tower by placing 
>> unnecessary vertical loads on the tower.
>> 
>> 73!
>> Frank
>> W3LPL
>> 
>> ---- Original message ----
>> >Date: Tue, 24 Apr 2007 13:04:03 -0500
>> >From: "Dale Martin" <kg5u at hal-pc.org>
>> >Subject: Re: [TowerTalk] Tower guy wires / EHS size
>> >To: <K7LXC at aol.com>, <towertalk at contesting.com>
>> >
>> > 
>> >
>> >I'm curious, Steve, where 1/4" EHS is used in place of 
>> recommended and 
>> >spec'd 3/16" EHS, does one tension the 1/4" EHS to 400 lbs. as one 
>> >would do with 3/16" or to whatever tension 1/4" is rated for?
>> >
>> >Looking from another aspect, is the 400 lbs. tension specified when 
>> >using 3/16" EHS on a Rohn 25g based on the tower type/heighth where 
>> >3/16" EHS conveniently has a stength of 4000 lbs and the 400 lbs 
>> >tension is just right for the tower?  Or should the tension 
>> be 10% of 
>> >whatever guy wire size strength is being used...e.g., 670 
>> lbs. based on 1/4" EHS strength of 6700
>> >lbs.?   
>> >
>> >73
>> >Dale, kg5u
>> >
>> >   
>> >>  
>> >> In a message dated 4/23/2007 9:03:02 A.M. Pacific Daylight Time, 
>> >> towertalk-request at contesting.com writes:
>> >> 
>> >> >  I am in the process of erecting a few towers at the new
>> >> QTH  and have
>> >> > a guy
>> >> wire size question.   Two of the towers will be  Rohn 45 @ 
>> >> 100' and the third
>> >> will be Rohn 25 @ 100'.  They will all  have multiple yagis at 
>> >> various heights on them, so not just a top mounted 
>> antenna.  The Rohn 
>> >> book indicates that each tower should be guyed at  three 
>> elevations 
>> >> and the bottom two guys should be 3/16"  EHS.
>> >> 
>> >> >  QUESTION:  I have LOTS of 1/4" EHS and guy  grips.  Is 
>> the 3/16" 
>> >> > mandatory
>> >> to
>> >> meet the specs (as in the 1/4" is  too heavy) or - is the 3/16" 
>> >> simply suggested (as in the 1/4" is not  necessary but acceptable)?
>> >>  
>> >>     While the LXC Prime Directive to "DO what the 
>> manufacturer says" 
>> >> still applies, what you're proposing is a little bit of  
>> >> over-engineering (which is not discouraged, BTW).
>> >>  
>> >>     The capacity of any tower is a function of its  leg 
>> strength. By 
>> >> using bigger guys you'll be putting more compression on 
>> the  legs but 
>> >> at the heights you mentioned, it's not a big deal. 45G will go to  
>> >> 300' and 25G will go to 200' so you're not overstressing anything.
>> >>  
>> >> Cheers & GL!
>> >> Steve     K7LXC
>> >> TOWER TECH -
>> >> Professional tower services for hams
>> >> Cell; 206-890-4188
>> _______________________________________________
>> 
>> 
>> 
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>
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