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