In a message dated 98-06-21 14:45:35 EDT, n4kg@juno.com writes:
> 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.
>
> 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.
I have used many different methods to establish tower plumb. The easiest
and fastest is to use a string/cord with a plumb bob on the end. I use a
wrench, big nut, etc. for the weight. When the wind is blowing, get a bucket
of water and drop the weight into the water. It'll dampen it just fine.
For new tower construction, I use a bubble level at the first set of guys
and then just sight up the tower for additional sections/guy levels. Anything
that's out of plumb looks pretty obvious.
Once you have something plumb, use it as a reference. I've used a nearby
cellular monopole, building edge or known tower to line up another tower.
BTW, tower specs allow 3 inches out of plumb per 100 feet.
> >
> >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.
Another reason not to use a pier pin base. Congratulations for
listening to the guy wire sounds and getting an instrument to verify
everything.
KH6X - BTW, your tower and antennas look pretty impressive on the cover
of the latest Force 12 catalog.
Cheers, Steve K7LXC
www.championradio.com --->>> Check it out!
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|