In a message dated 3/4/2003 5:25:06 PM US Mountain Standard Time,
jimlux@earthlink.net writes:
> I'd be interested to know the basis of the "verticality" requirement... 1
> part in 100 (about 1/2 degree) wouldn't appreciably change the loads at the
>
> base (1% using the "small angle approximation"), and hopefully the design
> isn't cutting it that close. (Assuming the guys are a reasonable distance
> away from the tower.. all bets are off if the guy anchor is 10 feet from
> the base of the tower...)
>
> There's a "do the job right" aspect, of course, and the advice to set it up
>
> now for inevitable adjustment later is certainly sound.
>
> For a contractual document (i.e. you're hiring someone to put up a tower)
> you need to provide "testable requirement". If standard industry practice
> is that it's easy to get it vertical to 1 part in 400, then there's no
> problem imposing that as a requirement.
>
> However, if you're doing the work yourself, you're not necessarily
> concerned about whether it meets some arbitrary standard, but more, whether
>
> it's safe, and the "safe" requirement might be substantially looser than
> the "pretty and good commercial practice" requirement.
>
> Jim, W6RMK
>
>
Hi Jim;
My EIA-222-D (yes, its old but its the most current I have here and this
section probably hasnt changed) says;
Section 6. PLANS, ASSEMBLY TOLERANCES AND MARKING
Section 6.1 Standard
Section 6.1.2.1 - Plumb - For guyed structures, the maximum deviation from
the true vertical shall be one part in 400. For self-supporting structures,
the maximum deviation from true vertical shall be one part in 250.
Just like KI7WX already mentioned.
The150' tower in question had a plumb bob (with possible wind deflection)
indication of 12" off vertical. (One part in 400 allowable tolerance equates
to 3" per 100' of tower. A 12" error in 150 ft of tower equates to 8"
deflection per 100' of tower or a one part in 150......unallowable by this
standard.
73,Bob K8IA
Mesa, Arizona USA
near the Superstition Mtns
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