Soundboard Deflection and Pitch Change / was Downbearing

[John Delacour]

At 8:23 am +0200 18/8/06, Ric Brekne wrote:

>Is this standard practice for most rebuilders ?

I doubt it very much, but look at the practice of a few good makers 
from the good old days; see whether the indentation is greater at the 
front or the back.

>  I would placing all the downwards force on one or the other edge of 
>the bridge would be asking for problems.. i.e. bridge rolling etc. 
>What is the benefit to doing it this way ?

The pressure is practically vertical and not "on the edge" of the 
bridge.  If you calculate the forces you will see how much likelihood 
there is of the bridge "rolling", even supposing that some 
wonder-tuner has perfectly equalized the tension on every string each 
side of the bridge.  The more the pressure is moved to the point 
where the speaking length terminates, the better the string is united 
with the bridge and the more likely to stay united under the effect 
of upward shocks.  The quality of the string's terminations at both 
bridges is extremely important.  To the left of the arrow the string 
receives no upward shocks.

JD

>At 8:36 pm +0200 16/8/06, Ric Brekne wrote:
>
>>How do you go about equalizing the downward force the string places
>>on the bridges front and back edges ? Or do you do this at all ?
>
>JD resoponds
>
>Why would you want to?  Ideally, in my view, the top of the bridge
>should be parallel, when the piano is up to pitch and well settled,
>with the length of string beyond the bridge so that the only angle in
>the string is where the speaking length begins, at the front pin.
>That is to say that the downward pressure at this point is the
>greatest.
>
>JD

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