Bill, K4XS, asks:
>What is the maximum height that one continuous length of Rohn 65 tower
could
>be 'walked up' and set by crane on top of the stub sticking out of the
>ground?
When I asked a similar question about Rohn 55, opinions were split as to
whether I could do 100 at once or not. People reported doing the following
successfully:
100' of Rohn 25
130' of Rohn 35
140' of Rohn 55
I picked up 90' of Rohn 55, about 10' from the top, and there was no
appreciable bending. I put the top 10' on separately because it had a lot
of added weight with rotors, etc, which in retrospect seems overly
conservative.
Unfortunately, my Rohn catalog doesn't have the specs on a 65 section. But,
given that 65 has about 2x the wind load capacity of 55, arguably its 2x as
strong as one could thus pick up about 2x as much. So 200' might be
possible. Probably the more practical problem is how expensive a crane you
are willing to hire; that may set the limit. Around here, a $100/hr crane
can only
practically get up about 165' or so.
I've been meaning to calculate how much bending moment a piece of 55 can
take,
but I never got around to computing it before it was time to put it up. (Not
having
a civ-e background, I have to do a bit of textbook work before I know I'm
doing it right,
so it will take me a bit longer...). It would be interesting if someone did
this to
supplement the anecdotal evidence.
73 de Bill N7VM
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