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## Re: [TowerTalk] Tram rope

 To: eric@k3na.org, wc1m@msn.com, Towertalk Re: [TowerTalk] Tram rope Jim Lux Tue, 19 Dec 2006 07:10:40 -0800
 ```At 09:32 PM 12/18/2006, Eric Scace K3NA wrote: >Yes, I saw a tram line part and the results were not pretty. The person >operating the winch narrowly escaped injury by the antenna and by the >parted line. This occurred early in my ham antenna career as was a real >wake-up call to the forethought required for safe installation. > >A tram line's forces act against the dead weight and wind load of the >antenna being installed. Because the tram lines come off at an angle, >those forces are much larger. (Draw out a force diagram using high >school physics.) Assume a tram line leaves the pulley holding up the >antenna at a 45 degree angle up and toward the tower, and on the other >side continues on at a 30 degree angle below horizontal in the opposite >direction toward the ground. For a 100 lb antenna, the force on the >line to the tower is 738 lbs and on the line to the ground is 602 lb. I'm having a bit of trouble visualizing the forces here. Is the antenna supported by pulley hanging from the tram line (a'la a gondola lift at a ski area), so you're talking about the forces on the support line. Or are you skidding the antenna up a guy wire, and the tram line is just the hauling line pulling it up at the angle of the guy? Either way, I have a hard time getting 45 degrees to turn into 7.38 or 1/7.38. Can you point me to a diagram? >That is the static case. Loads will vary when one attempts to start the >antenna moving from that point. > >-- Eric K3NA _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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