john@kk9a.com wrote:
> Apparently solid leg Rohn 45 does exist (model# 45GSR) and its windload
> ratings are quite impressive - similar to Rohn 65G.
>
> John KK9A
>
But what's the cost comparison? My gut feel is that 65G would be
cheaper than 45G. 65 is also larger overall diameter than 45, which
helps with the overall buckling load (you have to figure out the loads
for the buckling of the little sub-tubes and the whole tower as a
complete column)
off rohnnet.com, I found this:
65G 1.9" OD tubes, .625" solid rod diagonal braces, 26.25" face width
45G 1.25" OD 9 tube (14 ga), 7/16" brace, 16.76" face width
So the question is, is a 1.25" solid member more cross sectional area
(1.23 sq in) than a 1.9" tube (of some TBD wall thickness), and, more to
the point, is its section moment comparable? That 4th power adds up
real fast.
Cost is probably pretty close to proportional to weight.
It kind of depends, too, on whether the limiting load is the buckling,
or just straight compression.
(I guess that's why people pay Engineers to figure this stuff out)
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