[TowerTalk] Yagis and Rivets

[Andrew Williamson]

Hi all,

After all the talk of rivets in antennas and all the comments that they
will or will not fail, let's get back to the original topic.... rivets
in a Force12 antenna.

Some of the rivets DO fail, period.  I have only had experience of three
Force12 antennas that have been in the air for more than 18 months and
ALL THREE have had problems with the factory installed rivets that hold
the element mounting bracket to the boom.  The user installed rivets
that hold the elements together have had no problems, yet.

Let's take the three examples

1. A 100mph rated Magnum 340 installed at 100ft.  After less than two
years in the air (and admittedly 100+mph winds), all three elements were
loose on the boom.  Approximately half of the rivets that hold the
element bracket to the boom were missing.  I have photographs.  Also,
the factory installed rivets that were holding the boom sections
together were loose or missing.

2. A 120mph rated 5BA installed at about 50ft.  Again, after less than
two years in the air with winds never over 110mph (calibrated wind-gauge
nearby), the back element FELL OFF it.  All the rivets on that element
bracket had failed.  The antenna hasn't been taken off the tower yet, so
the condition of the other rivets is not known.

3. A C4SXL installed at about 50ft (I think that's the model, definitely
a C4xxx).  Less than two years in the air and at least one element is
coming loose on the boom.

As I said earlier, I've only ever seen three Force12 antennas that have
been in long term installations and all three have had the same problem.  

It's interesting to note that Force12 are now using bolts to mount the
element brackets to the boom in their higher rated antennas.  It makes
you wonder about the rivets!

Andrew Williamson GI0NWG / AC6WI
Homepage = http://www.gi0nwg.freeserve.co.uk/

One of the ZL9CI gang
http://www.qsl.net/zl9ci/

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