Another bearing question - call for expertize

[Stéphane Collin]

Hi John.


Q1: Did you take any measurement of the curvature of the soundboard
before you removed the strings?

I'm ashamed to admitt that I still don't have an accurate way of measuring 
this .  The carpet thread under the soundboard, next to every rib, I simply 
don't understand how you do this.  I myself can't access to every rib 
because of the wooden frame.  On the few ribs I can partially reach, I span 
the thread, but then can not read how many millimeters the thread is from 
the board.  So I try to figure out with a straight edge I put on top of the 
case, and measuring the distance of the soundboard from the straight edge. 
Here again, I can't figure out how this can be accurate, and how you can 
make difference between board curvature and board thickness differences.  So 
I uptill now rely on the string deflection as measured with a Lowell bubble 
gauge.  All I can say is that the board went up alot when unstringing 
trebble and bass, so the medium notes went more than 50 cents sharp.

Maybe you can enlighten poor me on a good procedure to make these important 
measurements.


Q2: Among your experiments to improve the sound, did you include any
tapping down of the strings at the bridge?

I must say I didn't.  Like you said, intuition plays a large role in 
diagnose of any problem.  My intuition told me there was no string to bridge 
contact problem, as there was unusually few false beats in this piano.


Q3: Have you removed the metal frame yet and if so, did you get any
unpleasant surprises?

Not yet.  Do you mean the tension you often find in Bechstein frames ?  I 
indeed found out that there was some tension in the frame in many Bechstein 
pianos I restored.  Why should this be an unpleasant surprize ?


I find it's almost impossible to judge these situations without the
physical presence of the whole piano and the intuitive messages it
gives.  One possibility that occurs to me -- and I could easily be
quite wrong -- is that there was too much load on the bass bridge,
but then on this piano I guess there are only 17 or 19 notes on this
bridge, though at very high tension.


Right you are, of course.  This is also my first thought of it.  But I 
thought twice and considered that even if the overall downbearing force was 
less, the individual downbearing of the strings in the middle section was 
more, as the board went up when unstringing the trebble and the bass.

What you think ?  Anyway, always a true pleasure to read you.

Best regards

Stéphane Collin