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[TowerTalk] guy rod angle

 To: [TowerTalk] guy rod angle w7ni@easystreet.com (Stan or Patricia Griffiths) Thu, 06 Sep 2001 01:21:57 -0700
 ```I took another look at my Rohn Catalog and I now see where they do list the rod angle. Funny, I never noticed that before . . . Still, they don't tell you how they caluculated it . . . I learn something new every day . . . even after 48 years of ham radio. Stan w7ni@easystreet.com Michael Rauh wrote: > Jerry, Stan, Dave, Tom, > > I agree with Jerry and Stan - the angle is probably not critical. Rohn > presents the angle to 0.1 degree in their guyed tower drawings. This seems > impossibly precise to me - there is probably way more sag or bow in the guy > anchor than that. > > I also suspect that Dave is correct when he suggests taking the vector sum > of the loads on the guys when the tower is at its rated wind load to find > the guy rod angle. > > In thinking about this problem I realized I don't know how to calculate the > individual loads on each guy wire. I use a rigid body model for the tower > that will give the total load on the guys, but won't tell me how the guys > share the load, at least as far as I can see. To figure out the load on > each individual guy, I think I will need to consider how the tower deflects > under load. > > Consider a tower with two sets of guys and an antenna on top. I could start > by assuming the tower is fixed at the top and the base. I calculate the > wind load and how the tower will deflect under that load. Draw a curve, > deflection vs. load. Then assume the lower guy is attached at mid-point, > draw a curve of elongation vs. load. The load on the second guy is where > the curves meet. The reminder of the load on the tower, including the > antenna load, is absorbed by the top guy. > > But wait! The top guy elongates under load too, relieving the load on the > bottom guy. So I will have to set up a system of simultaneous equations in > order to get the loads on each guy. I will need equations for the > elongation of the top guy, the bottom guy, the deflection (bowing) and the > pivoting of the tower. If the tower has a pivot base that is all I need, > but if the base is cast in concrete I might need an equation to account for > the force needed to tilt the tower as the guys elongate. > > Does that sound right? Do you know of any references where this kind of > problem has been worked out? I know Kurt Andress has found guy loads using > a finite element program. I need to understand the principles involved > before I resort to a program! > > I think it would be very cool to know how to find the loads on the > individual guy wires in a tower system. > > Best Regards, > > Mike Rauh, NV7X > > Reply to mikerauh@ic.org > > _________________________________________________________________ > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems, Trylon Titan towers, coax, hardline and more. Also check out our self supporting towers up to 96 feet for under \$1500!! http://www.anwireless.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
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