>> What is the useful height of a Rohn 45/55G section? I am trying to
>> figure out how many sections I need to get 110' feet in height.
>
> A Rohn 45G section is 10' 5" long and the leg coupler is 9 inches. The
>net length of a "10 foot" section is 9' 8".
>
> For a 110' tower, you'll need 11.38 sections.
>
> It sounds like you need the Rohn catalog. TOWER TECH has them for five
>bucks. You can't do any Rohn planning without it.
>
>73, Steve K7LXC
Steve, I have an older Rohn catalog and I guess they might have changed
the design in the last few years, but if they haven't I would suggest that
you check those bifocals out! HI
Overall length of the Rohn 45 section is 10ft 5in. That 5 inches is the
length
that the coupling extends past the end of the 10ft long leg. (The coupling is
actually 71/4 inches long overall.) The 9 inches you refer to is the
length from the end of the coupling to the first horizontal brace.
If you add up the 15/8 from the end of the coupling, plus the 15/8 hole
spacing, plus the 15/8 on the small end of the leg, you get 47/8 inches
of engagement in the 5 inches of the coupling. This extra 1/8 inch is
for tolerances to work out. This results in an actual stacking length
of 10 ft 01/8 inches. So 8 sections of tower will actually be an extra inch
longer than 80 ft. Of course this all assumes that the new catalogs
agree with my older one and that the design hasn't changed.
Just for the record.
73 John W0UN
So stacking Rohn 45 results in towers that are exact multiples of 10 ft
(well, +/ tolerances but that is typically pretty small).

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