Thanks to all who provided info and suggestions.
It appears that a practical solution to be able to use "old" Phillystran
might be to use wire rope saddle clamps at the right quantity and
tightening torque. So, based on posts, I am experimenting with 4
clamps with nut tightening torques (5/8" clamps for the nominal 5/8"
diameter PS I have 1800' of) at values of 25, 40, 55, and perhaps 70
ft-lbs (95 ft-lbs are recommended for 5/8" diameter wire rope).
I've talked with West Coast Wire Rope and Rigging here in Seattle, they
have a 5k to 500k lb pull stand for up to 180' long cables that costs
$150 per hour. However, this test cost would be prohibitive to test for
creep, so I've (reversibly) modified my H frame arbor press to be able
to do tensile testing up to about 20,000 lbs. This way I can test the
sample configuration under tension for days.
So I am now testing a 4' double ended section of old PS with 4 clips
each end to determine what loads and what torque values cause what
behavior. I've also done a limited literature search about Kevlar fiber
properties, and have not discovered any "show stoppers" for a saddle
clamp termination.
So far a test configuration has been adequately stable at 5000#
continuous load for 10 days. I will post more detailed results of the
testing after I am further along with the tests.
Grant KZ1W
On 1/13/2014 6:00 PM, Lloyd Berg - N9LB wrote:
Sorry, I meant to send this follow-up to the entire reflector.
The newer version Philly-strand is excellent - it has become the standard
for guying insulated AM broadcast towers, and is also used on some FM & TV
broadcast towers when guy lines have to pass thru the aperture of side-mount
VHF and UHF antennas.
73
Lloyd - N9LB
-----Original Message-----
From: Lloyd Berg - N9LB [mailto:lloydberg@charter.net]
Sent: Monday, January 13, 2014 5:15 PM
To: Grant Saviers;topband@contesting.com
Subject: RE: Topband: Ends for older Phillystran
Hi Grant!
I worked at WDAE Radio in Tampa, FL back in the 80's and 90's. The engineer
before me decided to try the new technology Philly-strand guy lines on th
AM directional towers because they had constant problems with the original
segmented steel guy wires/egg insulators constantly arcing over whenever
there was a thunderstorm in the area. To attach the Philly-strand, they
used traditional metal saddle clamps on this early ( somewhat experimental )
Philly-strand installation. It was a real neat looking job with 3 clamps 3
inches apart and all within 8 inches of the ends of the Philly Strand. Just
like you see on steel guy lines.
It was written up in Broadcast Engineering Magazine with lots of pictures as
the wave of the future for AM broadcast guyed towers.
In reality, it didn't work well because we were constantly having to
re-attach the lines because the inner strands pulled short inside the outer
sheath, leaving just the outer sheath holding the tower up! ( nude towers,
no antennas on top ). It didn't take long before we realized that we had
to use a lot more foldback length and a lot more clamps! We went with 36"
foldbacks with six clamps evenly spaced to keep things from pulling apart!
That worked and stayed together for the remaining 10 years I worked there.
Yes, we had to insert 6 feet of steel line at the anchor points to make up
for the lost length at each end of each guy lines.
No guarantees, but that was my experience with the original Philly-strand.
If you decide to keep it, be very careful and inspect it frequently! They
don't make that original Philly-strand for a good reason.
73
Lloyd - N9LB
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com]On Behalf Of Grant
Saviers
Sent: Monday, January 13, 2014 1:15 PM
To:topband@contesting.com
Subject: Topband: Ends for older Phillystran
Hoping for some help to be able to use some older Philly. The factory
tells me their grips won't work on "parallel strand" construction which
is what I have, epoxy potted sockets are required. However, they only
pot at the factory (liability etc etc) which means tossing 6 x 300' of
5/8" 45klb ultimate strength. Newer Philly (post 1991) is constructed
of 7 twisted strands, something like 7x19 wire rope (not exactly the
same, but similar) and the PVC sheath transfers the load effectively
with the Philly guy grips.
Any reports of success with field potting, materials, how to do it, and
where ends can be obtained (or a drawing, I will machine them) would be
appreciated. I would have a load test done on each guy post potting.
Grant KZ1W
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