I have had cable failure on one of my LM 470 towers as well. Although the
cable was rusted, and many years old that failure was caused by another
component in the tower system. The real culprit was a failed bearing in one
of the cable pulleys. Under load, this pulley locked up and acted as a
brake and greatly increased the strain on the less then 100% cable. I
strongly recommend that you lower the tower, and with appropriate wood blocks
the load off of each sections cables and inspect the pulley bearings. You
will have to disconnect the "down" cable to do this.
Going forward and along with regular lubrication of the cables, be sure to
get some lubricant into the pulley bearings.
Date: Mon, 8 Jun 2009 05:19:51 -0400
From: JP Lyet <firstname.lastname@example.org>
Subject: [TowerTalk] Crank-up tower limit
To: "email@example.com" <firstname.lastname@example.org>
Content-Type: text/plain; charset=us-ascii; format=flowed;
Had a Tri-Ex LM-354-HDSP cable failure 2 years ago. Corrosion mostly,
but actual cause is not known. Otherwise flawless service for 10
years. In retrospect, suspect the antenna load may have been a
contributing factor as between the 6 band yagi, T2X rotor and mast,
the total load was ~200#, or 80% of max load rating for tower!
Tower was totalled and recently replaced with identical unit. Beam
refirbed to like new, but reluctant to use due to weight concerns.
Anyone else in the group pushing a crank-up tower to ~ 80% of dead
load limit on a regular basis? Any other pearls or advice ? Suspect
my beam would be better served on a fixed tower installation and new
tower with a lighter unit.
(that being the case, anyone interested in a M-67B-3 can contact me
off-line for specifics)
Paul /W3PL in Pa.
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