My experience is that the tree grows around the rope over the limb
(pines, firs, cedars, not redwoods) and thus becomes immovable. So I
put a good $14 marine/ss pulley on the top end so it becomes a fixed
support. If the rope moves back and forth before it is grown around
then it frays and breaks, but there is little motion with a fixed rope.
The force needed to pull up antennas is also significantly reduced,
particularly if I spring for ball bearing pulleys.
Then the antenna hoist line thru the fixed pulley is a full loop so if
the antenna breaks I can't lose the antenna end. Or a 1/8" messenger
line on the end of a not looped (or looped) hoist line which can be
handy for tugging antenna wire thru/around branches. A full loop can
get surprisingly long since the antenna attach point can be a ways from
the tree base when the antenna is on the ground. Good pulleys are cost
effective vs line cost.
With very low wear, the 3/16 or 1/4 dacron line lasts, I'm reusing it
from 1986. Now and then some goes into a mesh bag in the washer and they
clean up nicely. I've done this with all sorts of gunked up lines since
my sailing days, but use a front loader which can't wrap them in an
agitator top loader mechanism (don't ask). But better not get caught by
the YL, and run a dummy load afterwards to clean the washer.
Bigger is better for pulley diameters but then they get very pricey if
marine quality. 8 to 10x rope diameter vs pulley (called a sheave)
diameter is the rule of thumb for modern fiber line running brigging on
a sailboat. 16:1 for wire rope to get 90% of break strength.
The "bungee in pvc pipe" is a great idea for tensioning, no big mass on
a spring effect with a bucket of rocks.
Grant KZ1W
On 8/11/2016 23:37 PM, Jim Brown wrote:
On Thu,8/11/2016 10:02 PM, Roger (K8RI) on TT wrote:
5/16ths is over 1700# strength, but a bit more expensive.
FWIW, I use the 5/16-in rope because it's easier to grab hold of to
pull tension on my very high dipoles. 3/16-in (and even 1/8-in) is
plenty strong enough for most antennas that aren't very high.
Wes, N7WS, described a system similar to one I rigged here soon after
I moved here, with help from Ira, K2RD, and others. I replaced it with
the system of pulleys that I now use because it allowed me to get the
antennas higher, and it also allowed me to rig a 20/15/10 fan in line
with the 80/40 fan that had loading coils for 160.
The system that Ira showed me how to rig had a continuous loop of
5/16-in that he launched over a limb with his pneumatic tennis ball
launcher (he cleared the tallest redwood on my property -- about 175
ft -- by at least 10 ft on the first shot). To that loop he attached a
pulley, then pulled the support wire through the pulley, then pulled
the pulley it all the way to the top.
That system survived at least one winter without a weight, because
there was enough "give" in the way the pulley was rigged to allow for
sway, but I'm not confident that the loop rope would have survived
over that limb for 10 years. :) Wes's experience suggests otherwise.
73, Jim K9YC
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