At 05:32 PM 2/3/97 -0500, you wrote:
>
>Hi Everyone,
>
>I got a question for you. Do you think a 4130 Cromolly Mast 20' x 2" x
.375" would hold a KLM 2 EL. 40 meter beam (45lbs - 6 ft2 - 16' boom) 15
feet above the tower? I will be using a thrust bearing. Let me know what you
think!
>
>Thanks and 73,
>John - WM9U
John, if I use 1.65 sqft for the effective mast area and that acts from an
equivalent point half way up the mast (7.5 ft) and I use 6 sqft for the
antenna at 15 ft above the tower, and I use 90,000 psi for the 4130
(a little conservative) I get wind survival for the mast as 102 mph.
But that ignores dynamic loading caused by gusting and resonance
on what would appear to be a somewhat "springy" installation.
I'd want to be sure the tower itself could handle this amount of
force with the long lever arm, not to mention the usual rotator issues.
Hope that helps--
73 John W0UN
John Brosnahan
La Salle Research Corp.
24115 County Road 40
La Salle, CO 80645 USA
voice 970-284-6602
fax 970-284-0979
email broz@csn.net
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