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## Guy wire help

 To: Guy wire help w5fl@flash.net (Wendell - W5FL) Wed, 19 Feb 1997 11:45:52 -0600
 ```Paul,=20 I just finished installing my 64 foot Rohn 45 Foldover Tower and got my = 2 element quad setting at 66.5 feet one hour after the ARRL cw contest = was over! Poor Timing. If you have EXCEL v 4.0 or later, I will send = you a spreadsheet that calculates the loads for a Rohn Foldover Tower. = I made it when I put up my tower. I designed mine for 110 mph winds and = the loads in the guylines are quite high - about the same as a 120 foot = tower with conventional guying at 80% of the height. The main thing you really need to watch is that your anchors are really = good and deep - and I would NOT use the screw in anchors that Rohn = furnishes! The uplift forces are nearly 2400 # and the guy tension is = over 1700 pounds which is about all I would want to put on 3/16 ehs = (about 3000 pounds ultimate strength - not working load) but should be = ok for 1/4 ehs (6600 pounds ultimate load). I used 1/4 ehs and it is = pretty stiff if you follow their directions and serve the ends after the = 3 cable clamps. I did it, but had to wear gloves (Rohn's tool might = work better.) You will find that four way guying is really good, but only about 14% = stronger than 3 way. That is why the economics favor 3 way guying, but = it won't work for the foldover tower. Any stresses that work for 3 way = guying will have an additional safety factor of 14% for 4 way guying. I have included the point design that I used for my tower. Maybe it = will show you the magnitude of forces on the tower: however, keep in = mind that it is for a Rohn 45. I hope enough of it gets through the = mailer to be readable. Good Luck, Wendell Wyly W5FL w5fl@flash.net Rohn 45 Tilt Tower Calculations =09 =09 7/16 members 45G 22.09779 Height (H) 64 (Feet) =09 Bottom guy angle 49.24002 PSF (p) 50 #/sq-ft =09 Top guy angle 68.04445 Ant (A) 17.2 sq ft =09 5/16 members 25G 18.65643 Guy R (rad) 25 =09 Rohn 25 crossection=3D 2.540256 Guys (gy) 2 =09 Rohn 45 crossection=3D 2.796355 =09 20 psf at top of tower=3D 568 pounds or 28.4 sq ft Anchor Dist = 35.35534 =09 30 psf at top of tower+ 516 pounds or 17.2 sq ft =09 =09 Tower Load 13.98178 x height =09 Feedline Load (1 7/8 and 1 1/2 per leg) 3.819444 x height =09 Antenna Load 860 =09 Note: 30 psf =3D 86.6 mph windloading =09 F1 (This is resultant of all guy forces) 698.6392 40 psf =3D = 100 mph windloading =09 Tension top guys 1713.818 50 psf =3D 111.8 mph windloading = =09 Tension bottom guys 1308.676 =09 Anchor uplift force 2347.428 =09 Base Down Force 9389.71 (Allowable vertical load on the bottom section = is 18,960#) =09 =09 Note: Items in Bold can are variables and can be changed. =09 Note: This program primarily calculates guy wire forces, anchor uplift = forces, and tower compression forces. =09 It is set up for two sets of guys, but will calculate more sets. You = will have to modify the tension and guy angle outputs. =09 Note: This tower set in 30 in diameter hole 3 1/2 foot deep. Guy = anchors are set in 16 in dia hole 5 1/2 ft deep. =09 Concrete is 3000psi 5 sack mix with 1 inch rock - not Sacrete or = Peagravel. Guys are 1/4 inch EHS. =09 =09 This information provided for educational purposes only. It runs on = EXCEL and you can look at the formulaes =09 used in the calculations and decide for yourself if the factors of = safety fit your application. Do not under any =09 circumstances use a safety factor less than two. No liability of any = kind is assumed by the author. =09 Use a Professional Engineer when you have arrived at a point design as = this design does NOT consider torsion =09 of the antenna or a failure in bending of the tower if you don't assume = the correct number of sets of guys. =09 =09 This analysis is for a fold over tower and requires four anchors. You = can convert to 3 anchors, but the forces will =09 be higher because the worst case occurrs when the wind force is 30 = degrees from a guy wire for 3 guys where the =09 worst case for four guys occurrs in line with a single guy. If there is = sufficient interest, I will also produce this =09 spread sheet for 3 guy anchors. =09 =09 =09 * I removed a Rohn FK2548 tiltover tower from my old QTH and plan to=20 * install it at my new location as a FK2568. The code here is for a=20 * tower to withstand 100 mph. Rohn has sent me info for the 25G that is = * for 110 mph. The FK25XX uses 4 way guying not 3 way. * Here is the question: Can I / should I use 1/4 guys for the tower to=20 * help with the 100 mph windload or use the 3/16 that came with the=20 * tower? I have to order some new guy cable because the tower will=20 * taller. =20 -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: K7LXC@contesting.com Sponsored by Akorn Access, Inc & N4VJ / K4AAA ```
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