humidity, teflon, hell, jon, whateve:(Was Tapping Strings)

[Delwin D Fandrich]

----- Original Message -----
From: <A440A@aol.com>
To: <caut@ptg.org>
Sent: April 08, 2002 6:11 AM
Subject: Re: humidity, teflon, hell, jon, whateve:(Was Tapping Strings)


> David writes:
> >Ed's example of the hole drilled in high
> >humidity being oblong at Christmas would not prove out, I suspect, in
that
> > the shape would be created by the difference in dimensional shrinkage of
> > the end grain verses across the grain.  The end grain change would be
less,
> > creating the out-of-round, however, the cross-grain shrinkage would
exert
> > enough pressure on the teflon bushing to cause the pinning to be
> >excessively tight, requiring easing.  The stuff that was loose in winter
> > would probably be caused by previous deformation of the teflon,
mis-easing,
> > or Satan.
>
> Greetings,
>    I don't think so.  I also have a customer whose piano is fine in the
> winter, yet every summer, there are numerous clicks in the action, plus,
the
> springs move the hammers a lot faster in summer. This seems to be the
result
> of the teflon being deformed by the summers humidity.  I believe that the
> cross grain expansion is sufficient to distort the teflon, (end grain
change
> is realistically nil) allowing this to happen. I have been told that
teflon
> has cold-flow properties, which I took to mean it would deform under
stress
> and then come back.


Actually, Ed, your experience pretty much confirms what David is saying. The
smaller hole around the Teflon bushing during the winter prevents the
clicking. The expanding wood during the summer (generally a period of higher
humidity) leaves room for the bushing to click in the larger hole.

At least was my experience--and I've not worked on one of these things for
many years but rather liked them when I did--that most of the clicking with
these things came from the bushing being loose in the hole of the flange
fork, not from loose centerpins. A tiny drop of glue around the bushing
would usually take care of the problem. This problem was greatly reduced
with the 'ribbed' bushings, especially the larger variety.

Teflon does, indeed, have cold-flow properties. But this means it will
deform under stress and not come back.

Del