Bridge Seating / food for thought

[William R. Monroe]

To quote Ric Brekne:

"I think that we need to put the numbers and physics, such 
as they are, on the back burner and do some hardcore practical process 
of elimination testing.  Nothing like real life observation of as many 
conditions as we can think of to help shed light on a subject."

and,

"Not being able to imagine or explain how a thing can occur has no 
bearing whatsoever on the occurrence  itself.  If one can observe the 
phenomena, then it occurs despite any lack of an explanation as to why 
or how."

So, maybe a wobbly pin can cause false beating, eh Ric?

Regards,
William R. Monroe



----- Original Message ----- 
From: "Ric Brekne" <ricbrek at broadpark.no>
To: <pianotech at ptg.org>
Sent: Saturday, September 09, 2006 5:47 PM
Subject: Bridge Seating / food for thought


> Hi folks
> 
> I just thought I might throw some numbers around to look closer 
> math-wise at this idea that the wobbly pin can change the speaking 
> length enough to account for false beats.  Take the following wire.
> 
> 0.9 mm diameter and 150 mm speaking length at a starting tension of 
> 150.95  lbs This yields a frequency of  1218.93 Hz.
> 
> To get a  rougly 4 beat per second false beat this string needs to 
> change in length by  around 0.003 mm.   That would require the pin to 
> deflect  nearly 1 mm !!
> 
> It would take a 0.15 mm pin deflection to enable a 1 bps false beat.
> 
> Realistically a pin might be able to wobble say 0.02 mm. That would 
> yield only a 0.15 Hz change.  Not hearable really. On shorter strings 
> the change would be slightly (and I mean slightly) greater.  On longer 
> strings, less.
> 
> Seems to me that  it is obvious that  the pin can not wobble enough to 
> change the length and tension of the string enough to cause any false 
> beats at all. 
> 
> There are other problems with this whole idea of wobbly pins causing 
> false beats.. such as the frequency of the supposed wobble itself... why 
> the significant side bearing hasn't already pushed the pin as far 
> sideways as is possible.... etc etc.. but the above in itself should be 
> enough to discard the idea.
> 
> Cheers
> RicB