Hi Bryan!
I just examined the broken guy wire and it appears that the wire was not
adequately snugged around the "fist" in the anchor (the closest Crosby
clip was 12 inches from the anchor!).
There is evidence of mechanical wear on the broken guy wire (shiny
galvanize on either side of the break, loss of galvanize, loss of
steel and some rust only on the strands in direct contact with the
anchor). The break occurred on the part of the cable that took the
heaviest load (midway around the "fist," directly opposite the
direction of pull on the guy wire).
Over a ten year period the guy must have gradually worn from moving
in the anchor "fist"! After two or three strands wore partly thru, the
remaining strands simply snapped!
Thanx for encouraging me to look more closely at the damaged guy wire!
Fortunately most of my guy cables are not fastened in this way (most use
preformed grips and heavy duty thimbles). I'll very soon replace all of
my remaining guy wires that have been installed this way for the last ten
years!
In hind sight, its apparent that the closest Crosby clip must be close
enough to the anchor to prevent the cable from moving in the anchor
during high winds! The 12 inches to the first Crosby Clip left the cable
free to move in the anchor. I've never seen a spec for the distance to
the first Crosby Clip, but -- obviously -- 12 inches was much too not
close enough!
I feel fortunate that this 135 foot tower is still standing. Today we had
gusts well over 50 MPH, and surely the tower would not be standing today
if hadn't been lucky enough to discover the broken guy yesterday!
Thanx again for your help.
73
Frank
W3LPL
donovanf@sgate.com
On Mon, 31 Mar 1997, Bryan Sparrowhawk wrote:
> Frank,
>
> **was the 'fist' a tighter radius than the other guy terminations on you
> installation? What's the minimum bend radius for 1/4" EHS .. the fist could
> be too tight a radius.
> **did it break at the tightest radius point in the bend?
> **signs of electrolytic corrosion? (probably not)
> **fatigue failure caused by continual deflection of the wire? (a big loose
> loop behind the clamps?)
> ** defect in the wire at that point? (galv. missing there?)
> ** lightning? (melted/pocked strand ends?)
>
> **did all the strands break at exactly the same point?
> ** were some of the broken ends rusty and others not? (a sign of a slow
> progressive failure.. one strand at a time)
>
> It's likely to fail again if you just hook it back up without finding the
> cause.
>
> de KD7LS
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