In a message dated 1/15/01 9:38:39 PM Pacific Standard Time, w8ik@subich.com
writes:
> When major portions of the country is in other than 70 MPH wind
> zones, it would make sense to do at least sample calculations
> for 80 and 100 MPH (or 110 MPH) wind zones. Manufacturers of
> guyed and freestanding towers (including Trylon on your web site)
> provide 70, 80 and 100 MPH loading information standard.
Some manufacturers have more information available than others.
>
> > Being insulted when you want something for nothing and don't
> > get it is a typical ham reaction.
>
> I was ready to buy, but the vendor/manufacturer was not willing to
> provide the basic information necessary for me to make an INFORMED
> purchasing/product selection decision ... damn straight I'm insulted!
> Most intelligent people confirm a product is suitable for its
> intended use and environment before they make a significant purchase
> commitment. Part of the decision requires careful evaluation of the
> manufacturer's specifications ... the customer should not have to
> pay just to see the specifications.
>
Someone has to pay for those calcs to be done - in the instances you
cited the factory paid for them. I guess the tower manufacturer you talked to
isn't willing to do it.
There's no in-between on these calculations - either they are calculated
by a qualified engineer or they don't exist. The problem is liability and
insurance. Tower manufacturing companies are insurance-driven and they're not
about to give you an opinion on the suitability of one of their products
without having an engineer run the calcs. The manufacturer will NOT give you
an 'opinion' or 'back of the envelope' calculation because it leaves them
wide-open for liability exposure. You want the calcs - you pay for them.
In the case of Rohn, most of their products go into the commercial world
where many companies that buy and install their products have engineers on
staff. Also their tower structures are much easier for someone to calculate
the forces for. Crank-ups go mostly to amateurs who sometimes don't pay
attention to factory specs which opens up a big can of worms liability-wise.
> I simply asked for maximum load ratings (square feet of projected
> area) extended and retracted for two or three candidate towers at
> 100 MPH - which is what the charts show for this county (it's not
> as if I asked for a set of wet stamp drawings for each tower!).
>
It still takes someone to make the calcs.
If you can find a crank-up that'll take 100 MPH extended, you let me know.
Cheers, Steve K7LXC
Tower Tech
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