[CAUT] Re: Restringing Treble

[Richard Brekne]

Sounds good to me... except that the bass doesnt seem to react the same 
way at all. Take off all the bass strings and we dont see much of a 
change in the other registers. Now I know there must be a good reason 
for this... but it might be nice for the present congregation to hear it 
one more time.

Cheers, and Happy New Year Jim.

RicB

James Ellis wrote:

>I won't repeat the previous posts, because I don't believe it's necessaty.
>Ron Nossaman is mostly correct.  The drastic change in pitch of one section
>when the tension is off an adjacent section has more to do with the plate
>than it does the soundboard.  But it's not so much "compression" of the
>plate as it is "deflection".  It's the fact that the plate wants to bow up
>when it's under tension.  Release the tension of one section, and the plate
>straightens out a little.  Put the tension back, and the plate bows up
>again.  That's what the nose bolts and the "horn" are for - to minimize the
>upwatd bowing.  It may not be obvious to the eye, but if you will put a
>rigid beam across the piano, and some dial indicators measuring both plate
>and board deflection at different places as you change overall tension, you
>will see what's happening.  I have done that, and the dial indicators tell
>the story.
>
>It's both plate and board, but as Ron says, I believe in this case, it has
>more to do with the plate than it does with the board.
>
>Another point missed here.  If you look at one string only, and see changes
>in neighboring strings, a part of that change will be coming from
>compression in the bridge itself - i.e., forces on bridge pins being
>reflected to neighboring bridge pins.  If you look at the bridge on a
>microscopic scale, you will see that it is not a rigid body at all.  On the
>cell-to-cell scale, it is somewhat springy too.
>
>Conclusion:  Because of the obvious plate deflection, you can't assume
>anything about the board.  When you change the tension, everything moves
>just a little bit, but not in the same direction.
>
>Sincerely, Jim Ellis
>
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