OK, here's a toss up that should generate some real discussion:
Rohn 45 and Rohn 55 have essentially the same face width and
the same cross bracing. The Rohn 55 has slightly thicker wall
side rails -- the center to center spacing of the side rails
is only 1/4" more (about 1.5% larger) than that of Rohn 45.
I am confused when comparing the Rohn 45 and 55 catalog specs
for 100' at 110 MPH. The 45 design uses 1/4" EHS at the top and
3/16" for the intermediate guys ... it is rated for 7.9 sq. ft.
The 55 design uses 5/16" EHS at the top, 1/4" EHS in the middle
and 3/16" EHS at the bottom ... it is rated for 15 sq. ft. The
guy anchors for the 55 design have about 25% more concrete (.84
cu yd vs. .67 cu yd).
I can't imagine the difference in rated capacity is explained by
the modestly larger side rails. Does this indicate that Rohn 45
could safely be loaded more heavily if the guy wires were upgraded
(e.g., to the Rohn 55 design or by using TA45 "star" guy brackets
and double guys at each level)? I also know that many users have
significantly overloaded towers when compared to Rohn's catalog
designs and gotten away with it.
Is the added cost (about 25%) for Rohn 55 "worthwhile" -- is it
really that much stronger or is Rohn 45 "as good" when guyed the
same way as 55?
... Joe, K4IK
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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