On Sat, 11 Aug 2007 15:04:05 -0400, "Rick (W-A-one-R-K-T)"
wrote:
What do you all think of using heavy duty nylon rope instead of wire for
guys?
I use it in areas where the stretching and elasticity is not a problem
such as guying to the middle of my AV640 vertical which is on top of a
40 foot tower. I put them up knowing they will stretch a *LOT* and
have to be re tightened several times in the first couple of weeks.
I have a Rohn 25G up 50 feet with a 2M/220/440 vertical on a 10-foot mast
on top of the tower. It is guyed at 30 feet with standard steel guy wire.
"Standard steel guy wire" is a pretty broad statement, but without a
whole lot of information. Steel guys vary from soft steel to the
Extra High Strength (EHS) that ROHN recommends. The steel guy wire
sold by Radio Shack can be pulled in two with just two men pulling.
I've done it. Galvanized wire rope is much better and easier to work
with, but it still has less strength than EHS or Phillystran.
I was just up the top of it two days ago installing the vertical, and it
seems rock solid.
I would not use Nylon rope on a tower as it would allow too much
flexing should you get a strong wind before the rope has aged and
finally taken a set. Nylon is not UV proof, but it will last a few
years.
You essentially have a 60' system and ROHN recommends two level guying
using 3/16" EHS steel tensioned to 400#. That means it's probably
4000# working strength or the same as HPTG40001 Phillystran
Even going to the 50' tower they still say guying at two levels with
3/16" EHS at 23 and 45 feet. With the array on top of a 10' mast I'd
put the top set one foot below the top of the tower and the other at
roughly 27 or 28 feet.
Why not use Phillystran (
http://www.texastowers.com/philly.htm ). I
use it on a 100' ROHN 45G with a very large array on top.
You could use the HPTG12001 which is 1200# test at 45 cents per foot,
or the HPTG21001 which is 2100# test at 59 cents a foot. IF the
loading is light and you don't live in a high wind area.
Don't forget to tension the guys at 10% of their working load.
http://www.rogerhalstead.com/ham_files/Tower29.htm
The tower is guyed at three levels using Phyllistran HPTG40001 @ 4000#
test at 32 and 68 feet and HPTG67001 @ 6700# test at 97 feet.(IIRC)
http://www.rogerhalstead.com/ham_files/Tower30.htm The bottom set of
guys is almost impossible to see.
Note the bend in the AV640 due to the strong winds when the photo was
taken. The Nylon guys are in place. It had only been up a month or
so. That tower has since gone through a game of "musical sections"
with the top and base sections being replaced and a straight section
added above the base section to make 40 feet.
Now my next project is to put up a 3-element tribander, and while my guess
is it'll probably be OK without any additional guying, the paranoid in me
says "hey, bozo... put up another set of guys!".
A lot depends on the current installation, but you have the VHF/UHF
array at 60 feet. Being 10 feet above the top of the tower that is
quite a bending moment although to do that I'd assume you have the
rotator down inside the tower.
I'm wondering if heavy duty nylon rope will be sufficient. It'll sure be
easier to work with, and there won't be the issue of having to break up
the guys every so often to keep them from resonating.
There is a ham on the other side of town that has FOUR (4) Rohn 25G's up
120 feet each, arranged in a square, and fed with a phasing network as
phased verticals for 80 meters. Each of the four towers is guyed in two
or three places with polypropylene rope. Been up a long time and seems
OK. But, there isn't a tribander and rotator on top.