In a message dated 98-10-07 21:44:02 EDT, d.dimitry@mci2000.com writes:
<< Needless to say, most of these guys have aluminum masts with the towers. I
think it is true that some aluminum masts are on the light side. However,
several years ago we started offering HAMS heavier walled material. No
doubt, many chrome-moly masts would still have a greater yield strength.
The question is: Is it necessary, and are you willing to pay the extra
change? Consider also, that you may be paying more for a nearly invincible
mast, only to have your antenna torn to shreds in serious winds.
The answer is: in most cases, yes. Heavier walled tubing doesn't change
the material yield strength. 6061-T6 is rated at 35K psi yield, normally
usable in smaller systems ONLY and in moderate windspeed zones (70 MPH or so,
the lowest rating).
I'll respond again after I've run the bending moment numbers on the
original question.
There are several grades of steel alloy tubing between the aluminum 35K
and 4130 118K or so psi. I've found SAE 1027 a good moderate choice at about
55K psi. Again, the only way to be sure is to run the numbers through the MARC
(Mast, Antenna and Rotator Calculator) Program. www.championradio.com for more
info.
>>Aluminum towers in general have stood the test of time. In addition to
their strength, they offer the corrosion resistance and light-weight, that
some owners both want and need. No one can reasonably argue that they fill
a niche, but even that is a large understatement. One last comment: like in
anything else, compare apples to apples. There are different manufacturers
of aluminum towers, just as there are different car manufacturers,
everything from Chevies to Cadillacs. Do your homework.
I think the original question was about masts and didn't have anything
to do with crank-up towers, aluminum or otherwise.
>> I would be happy to provide thorough calculations to any interested HAMs
about contemporary designs that meet strict up-to-date engineering codes. >>
Ah, now HERE'S a topic of interest to TowerTalkians. Yes, would you
please either post some general discussion relating to your "contemporary
designs" vis-a-vis "strict engineering codes" to TowerTalk, make them
available on your web site or send them to interested individuals? Which
codes - UBC, TIA, ...? Do you provide PE stamps? What states? Now that would
be a worthwhile contribution.
We certainly encourage manufacturer contributions but comments are best
appreciated when backed up with real information relative to the topic under
discussion.
Cheers, Steve K7LXC
Champion Radio Products
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