[TowerTalk] Trylon self supporting tower 80 ft fall report

[Charles Harpole]

I put up a used Trylon self supporting 80ft tower that I do not have the Model number of.  It was about 36 inches from leg to leg at the base and tapered to about 12 inches at the top, each section nesting inside the next larger one, forming one shipping package.  The cross members were angle iron galv. steel and the uprunning three legs were U channel, not tubular. It was loaded, or over loaded, with one each 20m 5 el, 15m 5el, and 10m 5el HyGain yagi in the HyGain Christmas Tree pattern with a very heavy (I could not lift it) 23ft chrom molly mast, six feet down inside the tower with two thrust bearings and the T2X rotor below.  All the bolts throughout were replaced with new galv correct sized bolts and it had no rust.  Mounted in a six by six solid concrete base. Four years after installation, I noticed two bowed cross members next to each other on horiz. at about the 40ft level and one bowed at about the 70ft level, all of which were replaced with similar steel angle iron, bolted as the original.   After seven and a half years, a very powerful straight line wind with near horiz rain for about five minutes caused the tower to fold over at about the 40 foot point, the lower sections standing ok, and only the one bent section destroyed.  All yagi sustained total loss of front half of each, with the ten getting more bending.  Rotor and mast were ok.  The break point showed about 30 degrees of twisting. Seventy feet away is a 70ft US Tower crank up free standing with a two el 40m quad and inside elements for 30 17 12, made by Cubex, T2X rotor.  This tower was cranked to full height and sustained no damage. My conclusion is that the Trylon was very loaded and that its weakness was to twisting forces, which it hinted at earlier and showed conclusively upon it folding over.  Because it failed, I also concluded that "it was high enough." Replaced it all this week with new tower and rebuilt yagis.  73,
Charles Harpole
k4vud at hotmail.com    PS... if you have never dis assembled a T2X rotor, be POSITIVE to read hams reports of how to do that prior to opening the bell.  Those in the know are now smiling.