[Top] [All Lists]

Re: [TowerTalk] tower specs/not wind loads

To: <>
Subject: Re: [TowerTalk] tower specs/not wind loads
From: "Robert Chudek" <>
Reply-to: Robert Chudek <>
Date: Tue, 24 Jan 2006 12:46:47 -0600
List-post: <>
I will confirm what Gene is saying about the BX towers who's cross members are 
riveted, not welded. In my youthful radio career, I put up 104 ft of HDBX 
tower. It was 4-way guyed at several levels. I installed a 6 foot torque bar at 
the top guy point to help reduce the twisting movement in the wind. Periodic 
inspection revealed rivets that had popped on this tower. As these were 
discovered I would install 1/4-20 bolts in their place. This tower survived 4 
or 5 seasons with a 6-element 15m homebrew yagi on top. Oh, the boom was 2" OD 
irrigation tubing and was 40' long. (Did I mention I did this installation in 
my youthful radio career?)

As an aside, our local radio community was fortunate to have a ham operator 
(WA0MGY - sk) who was our source for inexpensive undisturbed earth anchors. 
These were really slick... you auger an 8" hole at the proper angle about 8 
feet deep, drop the anchor into the hole, use a special tool to expand the head 
of the anchor into undisturbed earth, and backfill the hole. Later when I 
removed the tower, I simply unscrewed the above ground head of the anchor and 
pulled the rod out. You would never know there had been an anchor in that 
location. I wanted to install elevated guy posts but was (fortunately) elmered 
away from this type of installation.

Trylon towers are also riveted and I have found rivets that have popped on 
these towers as well.

I conclude these mechanical failures are a consequence of torsion forces 
created by the long booms on the antennas we use today.

73 de Bob - K0RC

* * * * * * * * * * * * 
Message: 1
Date: Tue, 24 Jan 2006 14:27:12 +0000
Subject: Re: [TowerTalk] tower specs/not wind loads


     You're correct - the BX-series of antennas has a torque limit on them.  
This is because they are assembled with rivets, not welds, between the cross 
pieces and between the cross pieces and the legs.  The rule of thumb with these 
towers is that a ten-foot long boom would impart just about the maximum safe 
wind-induced torque on the tower.  A longer boom might twist the thing apart.

     Caveat Amateur.

73 de
Gene Smar  AD3F

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>