pitch lowering

[RicB]

Hi Joe

I like the <<plate and rest of the structure>> bit.  But I dont really 
think soundboard deflection (at least strictly vertical) doesnt seem 
possible.  I did a spread sheet with calculations for change in string 
tension for changes in vertical deflection a while back.  Applying 
absolutly all changes in tension to the speaking length (which in 
reality gets somewhat dispersed over the entire length of the string) so 
as to give the string the entire benefit of the doubt as it were... you 
end up needing gargantuan changes in deflection to effect any real 
change in pitch.  No soundboard on earth would handle the resultant 
changes in downbearing pressure.

I checked this whole thing with guys like Alexander Galembo.. who 
actually helped me take into account the elongation of the string that 
needs to be considered when you are figuring changes in tension for 
changes in deflection.  While the model yields a rough picture.. the 
general picture it gives is true enough.  I have to conclude that 
soundboard vertical deflection simply doesnt get into the picture. 

You can test this out with a monochord, a strong but accurate scale, and 
an adustable deflection pilot screw connecting the scale and string. 

Cheers
RicB


    My own theory on pitch raising and lowering has to do with the
    soundboard
    catching up with the pitch change in the wire. I believe the soundboard
    takes at least hours to conform to the new tension (whether higher
    or lower)
    and regardless of how much in one sitting you change the pitch to
    stabilize
    it will still change more because of the inability of the soundboard to
    adopt to the new tension level that quickly. That is why on pitch
    raises
    (over 25c) I come back in 2 weeks after to retune..


    One should, also, take into consideration the de-compression of the
    plate and the rest of the structure. It is ALL connected, you know.<G>


    Joe Garrett, R.P.T.
    Captain of the Tool Police