[TowerTalk] Yagis and Rivets

[Stan or Patricia Griffiths]

Dave D'Epagnier wrote:

> Hello,
> I'm just about to finally put back up my C3-S. It's been up for about a
> year and a half and worked well all that time - no problems. I thought I'd
> maybe redo the joints with some silicone vacuum grease and kind of spruce
> it up a bit before it was put back into commision. One thing noticed on my
> half disassembled antenna though is that ALL OF THE RIVETS ARE LOOSE!
> Sorry, don't mean to shout  but  this is surprising. It looks to like every
> one of those once very sturdy rivets are loose. I can wiggle every element
> section with respect to its mate and have to wonder how good the rf
> connection is between them. And I thought rivets were the best and would
> never be a problem.They were installed correctly. I'm wondering if aluminum
> rivets are simply wimpy. Maybe steel rivets would hold much stronger and
> longer, and even though they may cause local corrosion, the overall
> connection might last longer with steel. Has anyone else experienced this?
> How did you deal with it?
>
> --Dave
> K0QE
>
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Somehow, this does not surprise me.  I have never used rivits and it is because
I don't trust them, even with all the good press they have had here.  The
problem, as I see it, is that aluminum, unlike steel, is a rather soft metal
that, when bent or compressed, takes a set in the new position, and tends to
relieve the pressure needed to maitain a good tight connection.  Metalurgists
have a term for this property of metal (ductility, maybe?) . . . I don't know
since I am not a meturgist.  You don't see many fasteners made of aluminum . .
.  not many aluminum bolts and nuts . . . not many aluminum lock washers . . .
and not many aluminum hose clamps . . . I think there is a good reason.  There
ARE exceptions to this because there are aluminum alloys that ARE springy and
act a lot like steel in that regard.  I have no idea what alloy aluminum rivits
are made of . . .   Just a few of my  rambling thoughts on this subject.  I
would like to read more from the REAL experts on this subject.

Stan  w7ni@teleport.com





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