[pianotech] String riding up on bridge pins, was Whistlin' Wixey

[George F Emerson]

Well, Ron, I've mulled it over all day, and I have concluded that you are 
right and I am wrong ....probably.

Frank E wrote:
>> Suppose we built a model with a bridge below the zero-bearing line.  Do
>> you suppose that we could force the string up on the bridge pins to
>> reflect a reasonable front and back bearing, relying on the surface
>> tension between the string and pin to hold it at that position?  I
>> suspect you could.

Ron N replied:
> I suspect so too, if you're careful. Now, what happens when
> the impulse pulse of the hammer strike hits the termination?
> I'd bet the string will go back down to a negative bearing
> position.

Negative bearing?  Why not zero-bearing?  In fact, that is what convinced me 
that you were probably right.... the presumption that a string under tension 
will do its best to find zero bearing, within the constrains of the system, 
and that any vibration of the string would only encourage it to do so.

The problem is that this line of thinking is based on a presumption.  Your 
photo only proven that this particular piano has negative front bearing, 
that the string would likely seek and find a point closer to zero-bearing, 
and that the friction with the bridge pin would help to keep it there.  In 
another sense, the problem is that we have unquantified (or poorly 
quantified) competing forces of static friction, dynamic string vibration, 
substantially greater side bearing than down bearing .... a recipe for 
potentially surprising results.

I must qualify my surrender with "probably," because I have often been force 
to give up my presumptions in the light of myth-busting studies, 
experiments, and slo-mo photography.  Much as I would like to pursue this 
further, I still have bigger fish to fry.

> And no, you can't prove a negative - or anything at all to
> anyone who already knows different. But I try.

Relax, Ron.  You win!

Frank