In a message dated 1/26/2008 9:02:51 A.M. Pacific Standard Time,
towertalk-request@contesting.com writes:
> Looking at the specs for the Universal Towers TX-455
versus the Tashijian LM-354 tower they are very
similar. Same height, same weight, etc. However the
LM-354 is rated at 23 sqft load at 85mph while the
TX-455 is rated at only 12.3 sqft at 70mph.
> I wonder if there is a good reason the LM-354 is rated
higher or if it may be exagerating its limits?
Boy, this is a good one. Before the TIA-222 and other building codes
were so prevalent, crank-ups used to be rated at 50 MPH windspeeds. Nowadays
it's not even a wind until it reaches 70 MPH - the lowest windspeed rating
in the US. Very few, if any of them, could meet the 70 MPH spec.
Both of those towers were originally designed by the same guy - Lou
Tristao - so they are reasonably similar structures. The difference is that
one has a #3 top section (the 354) and the other (the 455) has a #4 top
section. Since the 455 is known to conform to current codes, I'd say that its
capacity is realistic. And in that vein, I'd say that the 354 is incredibly
generous in its capacity rating. I don't think I've ever seen ANY crank-up
tower
that could take 23 sq.ft. @ 85 MPH. Karl is a PE so I'm assuming he knows what
he's talking about but I'm very skeptical.
Cheers,
Steve K7LXC
TOWER TECH n-
Professional tower services for hams
Cell: 206-890-4188
**************Biggest Grammy Award surprises of all time on AOL Music.
(http://music.aol.com/grammys/pictures/never-won-a-grammy?NCID=aolcmp003000000025
48)
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