Hi, Dale.
I don't have a tower up yet (planning one for this coming spring), but I
would definitely vote for the laser. My wife and I have been building
our own 4500 sq ft home for the last four years and one of the best
investments I ever made was a really good self-leveling 5-beam laser.
There were times I got lazy and tried using a plumb bob instead of
walking a hundred feet to grab the laser, and every time it was a mistake.
I would either buy an inexpensive laser level and fixture it to point
vertically from the center of the tower base, or I'd check around to see
if anyone locally in the construction trades would let you borrow a
professional one. My Pacific Laser Systems PLS-5 (a new one sells for
less than $350 now on eBay) is rated to have an accuracy of 1/8 inch at
100 feet ... can't beat that. It self levels so you just position it
with the downward beam pointed to the center of the tower base and the
upward beam will set your target up the tower.
Dave AB7E
Dale Martin wrote:
> 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?
>
> 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.
>
> 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?
>
> Comments? Suggestions?
>
> 73,
> Dale, kg5u
>
>
>
>
>
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