[TowerTalk] wind load

[Stan Stockton]

I am curious how many guys have first hand knowledge of an amateur radio 
tower (properly guyed) coming down as a result of overloading and how 
many instances there really are as compared to the number of towers that 
are severely overloaded?

I had a tower buckle one time because a tree fell on the top set of guy 
wires, but honestly have had seen a lot of towers WAY overloaded, beyond 
what I would even do, and in 40 years cannot remember ever knowing 
anyone who had a tower failure with ham antennas installed.

In most cases the tower specs include a huge amount of safety factor 
along with specs that include multiple, large coax cables from top to 
bottom.

Everyone has a comfort level which needs to be satisfied.

73...Stan, K5GO


----- Original Message ----- 
From: "Charles Coldwell" <coldwell at gmail.com>
To: "Tower Talk" <towertalk at contesting.com>
Sent: Thursday, February 18, 2010 1:37 PM
Subject: Re: [TowerTalk] wind load


> On Thu, Feb 18, 2010 at 1:34 PM, Stan Stockton <stan at aqity.com> wrote:
>>
>> I could be wrong about this but have always thought (from an old Rohn 
>> book)
>> that 70 MPH equated to 30 pounds per SF of antenna.
>
> OK, so in my example if the maximum wind load at 70 MPH is 15 sq ft,
> and we have 30 pounds per square foot, that works out to 450 pounds of
> force.  That sounds reasonable.
>
> If we believe the force grows as the wind speed squared, and that a 70
> MPH wind puts 30 pounds per square foot of force on the tower (and
> that a 0 MPH wind puts 0 pounds), then the constant of proportionality
> is 30/4900.  So that means the general formula would be
>
> F = 3/490 * W * W * A
>
> where F is the force in pounds, W is the wind speed in MPH, and A is
> the antenna effective cross-sectional area in square feet.
>
> What's the title/author of the Rohn book?
>
> -- 
> Charles M. Coldwell, W1CMC
> "Turn on, log in, tune out"
> Winchester, Massachusetts, New England (FN42kk)
>
> GPG ID:  852E052F
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