I clearly don't know quite what I'm envisioning here, but as I read
the discussion about resoldering the tracker bar I was wondering if
the nipple was essentially a cylinder and thus whether it would be
ever worth considering placing it into the chuck of an electric drill,
placing it into its home on the tracker bar with perhaps a bit of
solder flux, and spinning it such that the heat of friction would
melt the solder.  The idea would be to localize the heated area to
surfaces of the parts being joined.

I suppose this fantasy is an artifact from when I was reading about
'spin welding,' a legitimate industrial process that works about the
same way.  The weld is completed by just letting the spindle of the
drill coast to a stop.  How this would affect a solder joint, which
wishes to be left alone while it is solidifying, I don't know.

I understand that this isn't the sort of experiment you'd wish to try
on someone's antique irreplaceable tracker bar, but I was just sitting
here wondering about it.

Mark Kinsler
Lancaster, Ohio, USA
http://www.mkinsler.com/