If you have all most of the sections, you're still probably cheaper off
putting up the SSV. It's only one truckload of concrete. A Rohn 45G may
require 1/2 the concrete, but you have four holes to dig, guy anchors and
EHS or Phillystran to purchase along with the tower sections.
John KK9A
To: towertalk@contesting.com
Subject: [TowerTalk] Heavy duty free-standing tower options?
From: Howard Hoyt <hhoyt@mebtel.net>
Date: Thu, 7 Jan 2016 12:28:45 -0500
Hi Daniel!
As one who went down the Rohn SSV path, their method of sizing for wind
loading is a bit different, and largely unpublished. Their published
loadings are all limited by the smallest top section and wind speed they
specify. Depending on the height and wind rating this top section could be
the 1W/1WB, 2W or 3W/3WN. For example, each section is 20', so an 80'
tower uses four sections. Here are the relative ratings for different 80'
configurations, 80mph rating no ice:
4N/3WN/2W/1W = 3.3 sq. ft.
5N/4N/3WN/2W = 8.0 sq.ft.
6N/5N/4N/3WN = 21 sq.ft.
These were sent to me by a Rohn engineer, but not on stamped plans, so
they would not be considered certified, they were just to be used as
guidelines. Based on these guidelines I had planned a 120' tower using
9N/8N/7N/6N/5N/4N which most likely would have been rated at 24 sq.ft. @
90mph no ice. While I have obtained most of the steel, what has stopped me
from executing this plan is the foundation requirements, which are stout.
Referring to the Rohn foundation plans, the options for my requirement
vary between 7.8 and 9 cu. yds. Between the concrete, rebar and drilling
service, it would be many thousands of dollars for the foundations. I am
currently looking at a guyed 45...
Cheers & 73,
Howie - WA4PSC
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