[TowerTalk] Phillystran and Pulleys

[K7LXC at aol.com]

In a message dated 6/22/2009 12:52:01 P.M. Mountain Daylight Time,  
towertalk-request at contesting.com writes:

>  I've got some of the smaller 1,200 lb test Phillystran that  I bought 
years ago for a wire antenna project that didn't happen. It's too  
small for the 120 ft Rohn 25 that I'm preparing to install, but I'm  
wondering if it would work on my high dipoles that are up 110 ft in  
redwoods? 

>  The existing antennas, 80/40 fans fed with  150 ft of RG11, are held 
up by ropes (the "good" stuff that DX Eng and  some other ham vendors 
sell) through good pulleys, but the black UV sheath  of these ropes 
gradually abraid from friction as the trees sway, and  eventually they 
fail. A 5/16-inch rope holding up my 160M Tee vertical  failed after 
two years -- the sheath wore through completely, exposing the  inner 
white material. Luckily I discovered it before it rotted in the sun  
and dropped, and was able splice in a new rope and pull it through.  

>  I'm not worried about the pulling strength, which is  certainly 
adequate, but I am concerned as to whether the Phillystran would  
stand up to continuous flexing at the pulleys as the trees sway in a  
storm. Each antenna is counterweighted (about 100#) at one end,  
pulleys at both ends. 
 
    No, it is not meant to be used as a moving  material. You might be able 
to get away with it for awhile since the core is  like kevlar but wouldn't 
be very permanent. 
 
    Are your pulleys big enough? Maybe that's a  contributing factor. The 
smaller the sheave, the more stress on the rope. Just  a thought.
 
Cheers,
Steve    K7LXC
TOWER TECH 



 
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