Since there seems to be a lot of interest in tower design tradeoffs, I =
would be willing to email my EXCEL file to anyone who is interested. =
The spreadsheet is small (20K in size). I have used it for both Rohn 25 =
and Rohn 45, but it is configured for Rohn 45 at the moment. =20
You must have EXCEL on your computer to use it, double click on the =
symbol and it will be loaded and you can see all the calculations. =
Although I can attach a hard copy, it would not have the formulas and =
would show only the single point design. If you want the single point =
design please say so in your reply.
The anchor forces should be correct, but the actual anchor design is =
dependent on the soil and requires a soil analysis to determine the =
actual size of the anchors required. My soil is ROCK, so it has a great =
deal of holding power. =20
The analysis does not take into consideration the possible failure in =
bending of a tower (or torsion). If in doubt, use more sets of guy =
wires (and torque bars). This is fairly simple to add, but is not =
presently considered. The guying system also uses four anchors rather =
than three, which is considerably stronger since the worst case does not =
have to be derated by 13.4% due to the worst case wind loading of three =
anchors occurring 30 degrees from the anchor. For those that are =
interested in doing their own calculations, this will give you a =
starting place, but it is a complex issue to design a safe tower =
installation. That is why most cities require drawings signed off by a =
Professional Engineer before they will issue a permit to install a =
tower. I do not assume any liability for use of this program!
Wendell Wyly W5FL w5fl@flash.net
>DO IT RIGHT ... OR DON'T DO IT AT ALL !=20
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