Plumb Bob vs. Transit de N4KG
Frankly, I am amazed at this claim that a plumb bob caused the top
of the described tower to be off plumb by 2 feet. Could the transit
be the problem and not the plumb bob?
I use two plumb bob's, at right angles, to sight the tower and believe
I can get within an inch or two with this method. I use stranded
insulated
#22 wire and a 5 lb. window weight. Once it is stable it makes an
excellent
straight vertical line to sight. I usually sit on the ground with my
feet in front
and arms behind me and move only my eye as I sight up and down the
tower / plumb bob wire. A portable tri-pod or other support comes in
handy.
de Tom N4KG
On Thu, 14 May 1998 10:48:19 -1000 Jonathan Starr <kalepa@maui.net>
writes:
>A Builders Transit is the only tool that can properly plumb a vertical
>structure. Any wind or slight convection will make a plumb bob
>useless.
>
>My 100' Rohn 80 tower on sloping ground was plumbed as best possible
>using a plumb bob, 8' level (while climbing up and down), the horizon,
>and eyes, and we thought it was pretty good. The only clue that
>something wasn't right was that the guys on one side sounded
>different,
>duller, when tapped sharply with a wrench. This turned out to be the
>down side.
>
>When I brought a Transit home from the pawn shop, I was shocked to
>find
>the tower over 2' out from vertical, necessitating two new big grips.
>Luckily we had left the guy wire ends trimmed long to loop through the
>turnbuckles.
>
>Using a transit is easy. There are two bubble levels that must be
>centered using adjusting screws, and then the crosshairs should ride
>right up a tower leg or the center of a pole as you elevate the
>telescope.
>
>The only thing that makes adjusting guys with a transit time consuming
>is having to move the transit between two locations. Two transits
>would
>make it a very quick job.
>
>I see used transits readily available now that surveyors and engineers
>are using laser and gps equipment. Check your local rental or survey
>equipment supplier for used gear.
>
>Aloha,
>
>Jonathan KH6X
>kalepa@maui.net
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