string height

[Stéphane Collin]

Hello Bob and all.

Not sure what I will say is pertinent or not, but isn't there that feature in Steinway pianos that the belly rail is somewhat curved, while the keybed is straight ?  I thought this was intended to help keeping the board curved also.  And at some moment, I came to believe (is this true ?) that this was the reason why the Steinway specs ask for tapering to 1 more millimeter key height in the middle of the keyboard than at the sides.  Indeed, if the hammer height is to be set as to keep the distance from hammer to string constant, the hammer line would be slightly curved also, following the board and belly rail curve.  And logically (while I suspect that the geometry would not exactly call for that) the key height would have to follow (well logically it is the whippen rail and the rest felt that also should follow).
While I'm a bit confused with all this, maybe experienced someone could comment on this ?

Yet in Bechstein pianos I have seen, the belly rail is not curved, and sometimes (not always) you can measure about the same string heigth variations as you describe, from section to section.  In this case, I interpreted this as the limit of accuracy they then reached in casting the iron frame.  Is it so ?  And this should be easy to correct by tweeking agraffee heigth, not ?
I'm even more confused now.

Best regards.

Stéphane Collin.
  ----- Original Message ----- 
  From: BobDavis88 at aol.com 
  To: pianotech at ptg.org 
  Sent: Friday, June 08, 2007 8:05 AM
  Subject: Re: string height


  In a message dated 6/7/2007 7:01:04 PM Pacific Daylight Time, Frank writes, in response to Alan's question about uneven string heights in Steinway and Yamaha:
    I cannot imagine the design intent being anything other that equal string heights at the respective strike points.  Are you sure you were measuring precisely at the strike point?  
  I don't know Yamahas that well, but every Steinway I have measured (hundreds) exhibits this. Typically, taking three measurements in the tenor, two in alto, two in treble, string heights on all models except the D would measure:
  192mm-193-192 | 192-191 | 190-189 
  or something like it. I've seen as high as 193-194-193 sloping to as low as 188. I'd suspect undesirable plate warp, especially since the plate webbing usually somewhat mirrors this; but what do I know - I'm sure it's a Feature. Saw the tops off the treble hammers.

  Bob D





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