[pianotech] pitch change

[Ryan Sowers]

The jack idea is a good one Joe! I look forward to hearing the results of
this. Just don't pop out the soundboard!

The other thing to consider is the pitch change in uprights when you push up
on the keybed with your knees. You can sometimes get a pretty dramatic
change in the octaves by doing this (especially on small pianos). My
thinking is that since the keybed is attached to the plate that flexing the
keybed causes the plate to also flex and change the octave widths. Some day
I hope this leads to the holy grail of piano features: The Piano Whammy Bar!

This phenomenon again makes me think that plate flex is possibly the
greatest factor in seasonal tuning change - not because the plate itself is
reacting to humidity (of course) but because expansion of the beams,
soundboard, belly rail, keybed, etc is causing stresses on the plate to
change.



On Mon, Apr 5, 2010 at 4:24 PM, Joseph Garrett <joegarrett at earthlink.net>wrote:

>  It seems to me, that if you have a grand in the shop, put a jack under
> the soundboard and just jack it up 1mm at a time and measure the pitch
> change. That would, at least, be a starting point of consideration, I should
> think.
>  Change the humidity in your shop 10% see how much the soundboard will
> move. A piano will react very quickly to an increase in humidity, but will
> purge that humidity very slowly. (an article in Scientific American, 1970's
> proved all of this phenomenon). Those two quick experiments should tell us
> wether or not the soundboard swelling will change the pitch markedly. Of
> course, that is only one faction in the whole equation of pitch changing,
> due to atmospheric conditions, but it's a start. I'm really suprised that
> studies were not done and documented by some manufacturers. With all the
> Soundboard experiments that were, supposedly done, by Baldwin, there must be
> some documentaion laying around somewhere.??????
> Joe
>
>
> Joe Garrett, R.P.T. (Oregon)
> Captain, Tool Police
> Squares R I
>
>
>
>


-- 
Ryan Sowers, RPT
Puget Sound Chapter
Olympia, WA
www.pianova.net
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