[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 might be 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 ever 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
>> GPG FPR: 77E5 2B51 4907 F08A 7E92  DE80 AFA9 9A8F 852E 052F
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>