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

[David Skolnik]

Ed -

I'll try this again, as I think we're talking past one another

At 09:11 AM 04/08/2002 -0400, you Ed wrote:
>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.

I did not mean to contradict this. Definitely, the 'cursed click' of teflon 
is the provence of summer.  The wood expands outward and relaxes the 
pressure on the teflon bushing, thus looser pinning, and, sometimes, looser 
bushings themselves (in the wood).  The opposite would occur in the 
winter.  If the action is adjusted to work well in the summer, the 
likelihood is that there will be a fair amount of tight pinning in the winter.

>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.
>Regards,
>Ed Foote

While teflon is not impervious to the effects of moisture, I don't think 
the classic teflon problems are related to that, however, with regard to 
deformation, my understanding is that teflon does not recover from 
deformation.  Almost time to ask someone who really knows something.  Almost.


David Skolnik