Tower loading pt. 1
Thu, 6 Feb 1997 14:28:40 -0500 (EST)
In a message dated 97-02-06 10:31:46 EST, you write:
>> If this whole capacity calculation thing bothers you, why don't you
>>put up a bunch of 55G and quit trying to outguess Rohn specifications and
>>other practical advice you have received from TowerTalk?
>Are we getting a little short here, Steve??
Perhaps. But this is the third time I thought I've answered your
specific question while you continue to pursue it.
>It is not my intention to "outguess" Rohn, but to do several, iterative
>calculations myself. Rohn tower applications as drawn/described in many
>pages, are over engineered for safety.
IMO there's no need to re-invent the wheel (re-do the manufacturer's
calculations). It seems to be totally redundant to do it. According to
Rohn, the #1 reason for ham tower failures is overloading.
>Also, if you would perform some of the calculations yourself, you would
>see that some examples are much, much more overengineered as compared to
>the next example 10' taller, but list almost the same windloading
>Maybe that was this limiting factor the whole time. But who here can tell
Call Rohn and talk to one of their engineers. Don't forget that 1) they
have a huge liability exposure for every single product they ship out the
door and would prefer people do things correctly (to THEIR specs) and 2)
their specs are for ONE specific scenario. In order to standardize their
bases, anchors, hardware, notes, loadings, etc., they have had to make some
basic assumptions and sometimes the numbers are different from configuration
to configuration. For example, 80% isn't the only guy anchor spacing in the
>And is one to hire a PE every time he changes an antenna?? Wouldn't it
>be a lot better if you could figure it out for yourself? This is the reason
>I do not want to get a PE involved at this point.
Okay, then build a brute stout tower and go nuts. In a worst case
scenario of a catastrophe of your tower falling down, unless you did
everything exactly to Rohn specs, YOU are liable and not Rohn.
You don't need a PE to work out a couple of tower capacity vs. antenna
system configurations; it's a pretty simple process.
>Did Hiram hire someone else to do his work? Marconi? If you cannot do the
>calculations, that's fine. I would like to speak TO ANOTHER HAM, who
>does know how.
I think that the exact people who have the insight you're looking for
may be equally reluctant to expose themselves to any liability. PE's have
the training and insurance to do what you're asking. I'll bet you a nickel
that Marconi used an engineer to design and build his antenna supports.
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