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[TowerTalk] Force 12: rivets, hardware

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Subject: [TowerTalk] Force 12: rivets, hardware
From: (Steve Maki)
Date: Thu, 20 Nov 1997 01:00:17 -0500
Joe E. Mesh wrote:

> The solution to this light wind harmonic vibration is element dampening
> with enclosed ropes?  I have seen this done many times in old Telrex
> installations I have disassembled.   Typically owners installed jute
> ropes inside the elements of the 20m antennas.   I have always wondered
> if this was actually valuable.   The ropes themselves are universally
> wet and heavy with water content.   They tend to move over the years and
> collect to one end of the element or the other thus greatly upsetting
> the mechanical static balance of the structure.   This has always
> concerned me.

I've been using small (1/4" or 3/8") poly rope in every element I install
for years; it definitely works to STOP flutter, the major cause of element
failure in otherwise sound mechanical designs. Telrex antennas were
particularly bad for some reason.

I secure the ropes at the element ends by either cutting them a couple of
inches long, folding over (outside the element tip) and taping; or cutting
to exact length, and drilling a small hole thru the element AND rope at the
end, and fastening with a sheet metal screw or piece of wire.

I've seen no evidence (extra sag) of abnormal weight caused by soaked ropes.

If care is taken to ensure no direct water ingress near the element center,
it doesn't seem likely that condensation could overcome normal drainage out
the ends.

Steve Maki K8LX

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