________________________________
From: K7LXC@aol.com [mailto:K7LXC@aol.com]
Sent: Saturday, December 02, 2006 3:03 PM
To: towertalk@contesting.com; kg5u@hal-pc.org
Subject: Re: [TowerTalk] Plumbing a Tower
In a message dated 11/28/2006 8:56:24 A.M. Pacific Standard
Time, towertalk-request@contesting.com writes:
> > I played around on the other day doing some mainteance.
I made up a little
jig out of string to suspend between the three legs of my
Rohn 25G. I
looped and loosely tied one string to one leg. I tied the
other end of the
string to the horizontal brace directly across from that leg
and halfway
between the two other legs. I did the same for the other
two legs and
strings. The point at which the strings all crossed each
other is supposed
to be the center of the tower...right?
> Umm, I'm not sure if I'm following all
that but all you have to do is to stand back aways and hold your plumb line
in front of you and look along each leg and you'll see how vertical it is.
You're allowed to be out three inches in 100 feet so it doesn't have to be
exact.
Hi, Steve
Basically the three lines intersect in the middle of the tower....at least,
that's how it worked in Geometry class.
I was standing out at the backyard guy post this afternoon thinking about
just what you described. Except, I was going to plant 2x4's each with a
little arm to hang the plumb lines out from each of the guy points. Then I
could make adjustments, walk back to them and bring everything into plumb
that way. I just wasn't sure how accurate it would be looking through the
upper portion of the string at the tower top 90 feet way. But, if you say
it a workable solution, them I'm on it.
> > I may have done this all wrong. I read N4KG/K7LXC's
comments about plumbing
a tower. I just used a deep 1/2" socket as my weight and
nylon twine as the
line. Way too light compared to N4KG's #20 wire and 5 lb.
window sash
weight. I haven't yet found a day since hanging the line
where the wind is
light enough to even let the string hang anywhere near the
center even 20'
down from where it's hung.
> Drop the end of the plumb line into a bucket of water
and the wind won't blow it around.
It wasn't a matter of the weight blowing around; at a point about 20 feet
below where it was hung, the line was arcing over nicely into the side of
the tower by the breeze. It seems like no matter how light the breeze, the
string is way over to one side. I can grab the weight, move it to the
center and pull down and the line straightens out, but let go and the air
moves it to the side. :-) I just need a heavier, much heavier
weight...like th 5 lb. weight N4KG used.
> > I also think maybe I should do the plumb thing in stages
-- in my case, my
tower is 70' and I have two sets of guys. Should I plumb
from the lower set
of guys to get that portion of the tower plumb, then plumb
from the upper
set of guys to the lower set? The plumb line would be
shorter and maybe
less influenced by any wind.
> > Has anyone tried a laser? Seems like it would be easy to
make up a laser
target jig to place through the tower, then, on the ground,
use a laser in
the center of the tower and aligned to the vertical. Anyone
done that?
> I think you're making a bigger deal out of this than
necessary. What I do is to climb up to the first set of guys with a little
bubble level and put it on each leg. You can have someone on the ground
tighten or loosen each turnbuckle until you've got it where you want it.
Again, it doesn't have to be exactly vertical.
Yeah...I do that...too much time on my hands...
> Then all you have to do is stand on the ground next to a
tower face and just look up. You can tell easily how much it's out of plumb
and which way because it'll be pretty obvious.
I'll get it sorted out this week. It's supposed to get up into the mid
sixties by Wednesday.
73,
Dale, kg5u
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