I used to failure analysis on failed anchor shafts. In general, the failure
was the weld failing at the helix. However, occasionally, failure would be
associated with the installation torque. The welding was difficult, with
the weld beam following a helix, and also following the square configuration
of the shaft.....
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of k0dan
Sent: Monday, January 16, 2006 2:24 PM
To: Don Moman; towertalk@contesting.com
Subject: Re: [TowerTalk] Screw Anchor Question
> I have been told, or read somewhere, that the test to destruction failure
> point of screw anchors is that the weld holding the helix to shaft will
fail
> before they pull out or break the shaft.
> 73 Don
> VE6JY
Don:
This could well be true; in my one (and hopefully only) case of screw anchor
failure, the rod (if I remember right this was a 4+ foot rod, with a 4" or
6" auger on the end? Can't remember exactly) pulled apart approximately in
the middle, not where the helix/auger were welded.
The rod had deteriorated to a fairly thin diameter (new was maybe 3/4" to 1"
(again I don;t remember exactly), but what came out of the ground was as
thin as a pencil.
I think what happened was, with the extra loads of a wind storm (50MPH), the
rod material was so thin, it pulled like taffy. What came out of the ground
literally looked like it had stretched before it snapped.
These were the days before digital cameras, so I don't have photos in
digital format, but I do have hard copy prints somewhere, if anyone on the
list wants to see what can happen to these materials over time. The proud
tower, antennas, feedlines, and MUCH work can be trashed very quickly!
73
Dan
K0DAN
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