In a message dated 99-01-28 20:20:19 EST, rjbro@MISNET.COM writes:
> I have a twelve foot long piece of galvanized pipe I want to use for a
> mast. On the pipe is stamped in red "
> " Wheatland cbw rn 1176 cbw rm 1504 astm A53 -f- gra 40 A 21 foo
> 32698 DI."
> This has an outside Diameter of one and three quarter inches. It
> just does fit through the rohn 2" thrust bearing... I want to use it to
> mount a beam with a 4.9 square foot wind surface at the top of the
> mast pipe which is sticking ten feet out of the top of a flat top
> rohn 25 top section with the rohn thrust bearing on the flat top
> and a rotor in the usual place. How much wind would it take to bend this
> pipe??
First of all, Jackson County is a 100 MPH windspeed zone - pretty
severe.
I think you've got some galvanized pipe which is pretty weak for mast
applications.
Nonetheless, the situation you describe creates a bending moment of
26,200 in-lbs on the mast. The recommended mast should have 50,000 PSI yield
strength and 0.250 inch wall. Since even Schedule 40 has a maximum strength of
around 35KPSI, it's not even close to being good enough. You need some steel
tubing, not pipe.
The above calculation is from my Mast, Antenna and Rotator Calculator
program - MARC. Both it and windspeed ratings for all counties in the US are
available at http://www.championradio.com. The windspeeds are free. MARC is
$9.95.
Cheers, Steve K7LXC
Champion Radio Products
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