[TowerTalk] Fw: free-standing tower vert plomb accuracy

[Al Williams]

----- Original Message -----
From: "Al Williams" <alwilliams@olywa.net>
To: <towertalk@contesting.com>
Sent: Friday, October 13, 2000 12:35 PM
Subject: free-standing tower vert plomb accuracy


>
> According to FirstCall, the rejuvenated triex towers are selling well.
> Other new owners
> are likely to also be interested  in the following two part question:
>
>   1. How accurate should a free-standing towers vertical plomb be?
>
>   2. How to measure the vertical plomb?
>
> (The motorized SKY470/LM470) does not have levelling nuts for adjusting
the
> towers' vertical plomb for leveling the tower.  The base fixture must be
> levelled before the concrete sets.  The suggested method is to use a level
> set on top of the three base mounting plate ears and move the base fixture
> until level in all three directions between the three plate ears.  The
> distance between mounting plate ears is 24 inches.)
>
> I believe that with care, I can easily detect an error of .03 inch in 24
> inches using an aluminum bubble vial level.  (I shimmed one end of the
level
> and measured the shim with a dial caliper.  Then turned the level
> end-for-end to verifyy the accuracy of the level.)  If my calculations are
> correct, this translates to 1.275 inches at the top of the 70' tower with
> 15' of mast extending.
>
> Unknown is the tower mfr's vertical plomb inaccuracy of the mounting holes
> and the tower legs themselves.
>
> The stress analysis that I have reviewed (I am not a mech or civil
engineer)
> do not make any reference to the vertical plomb requirement.  My "feeling"
> is that the tower rated at 15 sq ft at 70' height for  80mph wind can
> withstand considerably more vertical plomb deviation than 1.275 inch--but
> how much?????
>
> k7puc
>
>
>


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