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## Re: [TowerTalk] wind load

 To: "Tower and HF antenna construction topics." Re: [TowerTalk] wind load "Stan Stockton" Stan Stockton , "Tower and HF antenna construction topics." Thu, 18 Feb 2010 14:20:59 -0600 mailto:towertalk@contesting.com>
 ```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" To: "Tower Talk" Sent: Thursday, February 18, 2010 1:37 PM Subject: Re: [TowerTalk] wind load > On Thu, Feb 18, 2010 at 1:34 PM, Stan Stockton 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 > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```