In a message dated 96-12-20 17:23:25 EST, you write:
> And like antenna
>>manufacturers, crankup tower manufacturers sometimes play games with
>figures.
>
>The density of the air hasn't really changed, and the wind speed is still
>the wind speed.
That's true but that's why they still ADVERTISE 50 MPH wind load
figures in a 70 MPH world.
>
>> In order to upgrade the towers to a 70 MPH minimum would require:
>1)
>>recalculating all of these towers (it would be expensive and no
manufacturer
>>is really interested in doing it again since they've already spent the
>>engineering expense once);
>
>Yea, like *I*'m in a better position to perform these calculations, even
>if I were a PE (which I'm not).
>
That means that if you want the figures, YOU have to pay someone to do
it.
>> 2) down-rating ALL of the above towers to comply
>>with the (as you pointed out) MUCH larger wind pressures;
>
>How is this down-rating? They would merely publish the ratings for the
>designs as they currently ARE. They aren't changing the ratings, just
>stating them more correctly.
>
Down-rating means lowering the wind load to comply with the higher
wind speeds.
>> Do you think that amateur radio operators (a bunch of widely
recognized
>>cheap bastards) would be willing to pay for these more expensive towers? I
>>don't think so; they complain enough about the cost of anything as it is.
>> Everything gets back to manufacturing cost so the manufacturers are
>>unwilling to increase the cost of their products unless absolutely forced
>>into it.
>
>OK, so where does that leave us?
>
Well, basically SOL. Unless you pay someone to re-calculate a tower
for your wind speed zone and load it to those numbers or try to finesse the
exisiting engineering data through your building department.
>I just want to put a tribander up on a modest height of 45-49 feet. Guyed
>towers aren't practical in my lot, and crank-ups offer advantages to the
>neighbors. Tubular crank-ups especially so. But, if my 50 mph tower falls
>in 70 mph winds, my insurance company may decide they aren't going to
>cover it, since it was underrated for the conditions.
>
Your insurance company won't know anything about it unless you tell
them; all they want is an estimate for repair from a reputable company so
they can pay the claim and close the file.
>If the manufacturers aren't willing to rate their wares effectively, and
>insurance requires it, doesn't it open them up for potential liability?
>
Yes, that's why US Towers has made a statement that cables and pulleys
should be replaced every 2 years. Is that practical or even necessary? In
almost all cases - no, but it gives them a huge weasel clause in case
anything happens to your US Tower. "Had an accident with your crankup? Did
you change the cables and pulleys every two years? No? SORRY, it's not our
problem."
Your choices include Rohn HDBX, Rohn RTP, roof-mounted tower and
aluminum self-supporters in addition to crankups. Do you have a copy of my
"Building A One Tower Station"? SASE to TOWER TECH, Box 572, Woodinville,
WA, 98072, will get you a copy.
73, Steve K7LXC
TOWER TECH -- professional tower supplies and services for amateurs
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