Bridge as a 2nd class lever

[David Ilvedson]

When a string breaks, the loss of tension causes havoc in the area around the break.   Replace the string and you still have to retune several notes in each direction .  Is this sort of the same thing as you are writing about?

David Ilvedson, RPT
Pacifica, CA  94044


----- Original message ----------------------------------------
From: "Ric Brekne" <ricbrek at broadpark.no>
To: pianotech at ptg.org
Received: 8/8/2006 11:50:49 PM
Subject: Bridge as a 2nd class lever



>Hi Cy, I wasnt aware that Reyburns graphs touched directly on this 
>particular perspective, but perhaps it does.  It might be interesting to 
>see if his measurements show any correspondance to this bridge leverage 
>idea.

>As far as soundboard deflection having an measurable impact on pitch, I 
>would have rather assumed that was a given in itself. Only stands to 
>reason if the soundboard deflects one direction or the other even a 
>little, then its pressure on the string will change yeilding a change in 
>string tension.  The only question is how much deflection results in how 
>much pitch change.  But it does strike me that if a change in downwards 
>pressure anywhere on the bridge can/does effect change in downwards 
>pressure at or around the killer octave region... then one should be 
>able to directly measure this and that string tensions is a likely 
>approach.  One doesnt necessarily need a <<major factor>> type pitch 
>change... only one that is significant enough to observe by measurement. 

>Course there are probably other ways of directly measuring the effect of 
>changes in bearing on the bridge at other places on the bridge.  This 
>was just the first that came to mind.

>Cheers
>RicB



> > Dean Reyburn has extensive graphs of the interactions of tension on the
> > bridge, that he used to put the pitch raise feature into RCT.  I assume
> > Robert Scott has similar data.  It may be proprietary to them, of course.
> >  
> >
> >> I'd like a much closer gander at the printouts and the assumptions
> >> made. As far as I understand there has been no attempt (outside of
> >> mine today) to actually measure in any way whether the model holds
> >> true ??  If someone knows otherwise please send along whatever info
> >> you have.
> >>
> >> Thanks for any and all comments
> >> Cheers
> >> RicB


>All of which assumes that soundboard deflection is a major
>factor in pitch change, evidence to the contrary. If you can
>make that unsupported presumption work plausibly by either
>demonstration or by math and logic, then you have a potential
>case. Otherwise, you're just making random noise.
>Ron N