Don wrote: > Hi Richard, > > It ain't the plate moving due to the metal changing due to humidity..it is > the support structures for the plate--which are wood! > Grin... yes yes yes.... but then if the plate becomes loose from its support brackets, and it isnt strong enough to support the tension of the strings without moveing, then its most likely the piano will loose pitch. We already know that the soundboard will flatten somewhat in dry periods, and this has been measured by more then one. Its also been observed that as years go by the panel looses some of its ability to change crown with humidity changes, and as that becomes apparent the changes in pitch also become less pronounced. Further, given the fact that this happens rather uniformly on all pianos, and given the fact that plate castings vary quite a bit from piano to piano, it would seem that if the plate had any substantial role to play in this you would see a lot more differences from piano to piano in the way pitch change shows up. Instead we see results that are consitant with what we would expect from the panel "breathing" as it were. Like I said in my last post, its easy enough to create a simulator that would allow you to vary all such parameters.. You could even use an old junk grand and create each condition and measure the results. Force up the panel, measure... force down the panel, measure... loosen the plate bolts, measure.. You could even subject the rim area to a good deal of humidity while keeping the main body of the panel isolated and stable. I suspect that any such experiment would simply confirm that it is the Panel itself that is by far and away the major player here.. IMHO...grin -- Richard Brekne RPT, N.P.T.F. Bergen, Norway
This PTG archive page provided courtesy of Moy Piano Service, LLC