In a message dated 11/28/2006 8:56:24 A.M. Pacific Standard Time,
> I played around on the other day doing some mainteance. I made up a
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.
> I may have done this all wrong. I read N4KG/K7LXC's comments about
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.
> 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
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.
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