[TowerTalk] Poly rod, Fiber glass rod, Fiber Protrusion rodtension?

[Jeff Blaine]

Hard to use a Loos gauge on bigger EHS though.  I've got 3/8 EHS on my 
top guys and when I hold the Loos up next to it, the EHS just laughs and 
calls me silly names as the nearly unbendable 3/8 EHS laughes at me...

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 15-May-18 6:01 PM, Chuck Dietz wrote:
> By the way, most guy lines like this are terminated with about 15 feet of EHS guy line so they are protected from fire and intentional harm. The Loos gauge will measure the tension on the EHS, not the Poly rod.
>
> Chuck W5PR
>
> Sent from Mail for Windows 10
>
> From: Grant Saviers
> Sent: Tuesday, May 15, 2018 1:54 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Poly rod, Fiber glass rod, Fiber Protrusion rodtension?
>
> I think the idea in different tensions vs height is to generate the same
> horizontal restraining force since that changes with the cosine of the
> guy angle with the ground.  i.e a horizontal guy (zero deg) provides
> 100% of its tension horizontally to the tower, and a vertical guy (90
> deg to ground) zero force.
>
> To stay < 10% of break strength, larger guy diameters are used for upper
> guys and need to be stronger since it takes more ultimate strength to
> restrain the tower from sway.  The amount of strain (stretch) with high
> wind forces increases the sway so larger guys stretch less per pound of
> tension.  (see the K7NV finite element analysis) btw EHS from what I've
> read, even though very high yield strength, does start to stretch
> permanently at about 60% of break strength.  So that is the "normal"
> limit of allowable tension. While stretch is only a few percent of
> length when stressed that high, that can change the initial tension.
> After a max wind "event" it is probably smart to check tensions.
>
> So with that in mind, I think the correct tension is what is specified
> for each guy level by the tower manufacturer, independent of the
> strength of the guy.  My considerably oversized guys (1/2" Phillystran,
> 25k# break) were specified by the PE at near normal Rohn pretension
> levels.  Another limiting factor is the compression yield strength of
> the tower sections.  The bottom section has the weight of all the metal
> above plus the vertical component of the sum of all guy forces from
> every guy level.
>
> So if your polyrod break specs are the same or better than 5/16 EHS all
> is well, follow what Rohn specifies for pretension.  One small
> difference might be the pretension stretch vs EHS, which is very low.
> Anyway, by tensioning to the Rohn spec that initial stretch is removed.
>
> Since you have a dynamometer, leave the Loos gauge in the toolbox.
>
> Grant KZ1W
>
> On 5/15/2018 9:20 AM, john at kk9a.com wrote:
>> What is the breaking strength of the rod?  5/16 EHS is 11200 pounds and
>> typically you tension it at 10% of breaking strength. I am not sure what
>> diameter Polyrod is. If it is large, measuring its tension with a Loos
>> gauge may be a challenge.
>>
>> John KK9A
>>
>> Ed K5OF wrote:
>>
>> Question: For those that have used what is commonly referred to
>> depending on discussion “poly rod”, “fiber glass rod”, “Fiber protrusion
>> rod”, etc. in lieu of ehs or phillystran what is the recommended tension
>> of said rod for 5/16” rod?
>>
>> I have done quite amount of research both on line and contacting
>> manufacturers and have found nothing that I can use for a reference or
>> make any sense due to the engineering specs the manufacturers provide me.
>>
>> I am not an engineer and cannot figure out what the recommendation would be.
>>
>> I have my current tower project spec’d on ROHN 55G 130 mph at 130 feet
>> 100 % guying (130 feet) and it calls for the lower guys if using EHS
>> spec ¼” at 665 lbs tension per guy and 5/16” at 1120 lbs tension per guy
>> for the upper guys. (3 sets of guys, the two lower ¼”, the final upper
>> at 5/16”)
>>
>> If I am correct if I was using phillystran the tension would be the same
>> based on the same equivalency of that material used to the EHS guy specs.
>>
>> Since I am using this 5/16” “rod" on all three guy levels I want to make
>> sure I do not under or over tension.
>>
>> Rod provided was second hand (no issues, brand new) and was a great
>> deal! I am all set to go up with tower but want to get this right before
>> proceeding further. I have Loos gauges and Dynaometer at my disposal
>> along with everything to get this project up as described above. Hope to
>> get going when I get back from Dayton. From what I have determined so
>> far it is best to tension everything up of course beginning with bottom
>> set of guys to roughly 250 lbs + or -, get plumb and go from there with
>> turnbuckle adjustment and get somewhere in the ball park of a safe and
>> secure tension on final product as we go up to the final set of guys
>> (#3) at 130 feet. 250 lbs is far off from 665 and 1120 but because of
>> the material possibly those tension specs are not in the ball park of
>> EHS or Phillystran? What say the group with any knowledge of using this
>> type of guy material? When I get back from Dayton I am working on
>> getting the tower up with a successful and safe out come? Thanks in
>> advance , if you see me at the Crowne or the venue stop and say hi! 73!
>> Ed K5OF
>>
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