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## [TowerTalk] WINDLOAD Considerations

 To: [TowerTalk] WINDLOAD Considerations "AD5VJ Bob" Sun, 10 Dec 2006 02:38:07 -0600
 ```I am planning a tower installation: After looking in the ARRL Antenna Handbook, I googled "wind load formula" and "antenna wind load formula" and came across many types of formulas for many uses (sailboats, antennas, Towers, buildings, ect) and about 9 different standards, some government some corporate. As I was looking over this information trying to determine if the HamIV rotor would handle the new antenna (since it is an older antenna I don't have WINDLOAD numbers on it), a question came to mind and I am trying to find out if it is a consideration. I found that manufacturers for Ham Radio equipment use: ANSI/TIA STANDARD 222 - STRUCTURAL STANDARD FOR ANTENNA SUPPORTING STRUCTURES AND ANTENNAS: http://www.bechteltelecoms.com/docs/bttj_v4n1/Article5.pdf http://www.arraysolutions.com/Products/windloads.htm But they all seem to assume a constant (worse case) wind speed and direction at a given moment of impact at a standard height (30feet). It all seems to simplify to calculated surface area of the object that the wind is imposed on and the speed of the wind. I found one formula that is successfully used by Hams to determine WINDLOAD. http://k7nv.com/notebook/topics/windload.html It tells me to multiply the dia of the ant element by the length then add the products of all of the elements and that gives me the element to get the total element WINDLOAD. Another one was: Written by a Ham who is published and is considered to be an authority: David B. Leeson, W6QHS (now W6NL), "Physical Design of Yagi Antennas". http://www.realhamradio.com/Download.htm The question is: As the rotating antenna(s) move dont the pressures of the wind with relation to the antennas change as they rotate, making the result of the WINDLOAD formulas change in value in a real world scenario. Also the tower and/or mast is not perfectly still as the wind moves it (waddles, wipes, vibrates, ect) and the rotor turns it. I would think that change in inertia must add to the forces on the structure, and so does the change in the speed of the wind. How does (if it does) the change in force due to the change in wind direction and speed with relationship to these objects as they both move about affect WINDLOAD on the supporting structure itself? Or do we just throw in an % error factor, because no one knows. 73 fer nw es gud DX, QSL VIA: BUR, LotW, e-QSL Bob AD5VJ(AAR6VM) Old calls: WY5L/KH3-KE5CTY-N5IET http://www.ad5vj.com/ Member: CTDXCC, NTCC, STXDXCC FISTS: # 12637, SKCC# 2369 10X# 37210, FP#-1141 SMIRK#-5177, RARS #-149 _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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