S&S D with high strings/low action stack

[Erwinspiano at aol.com]

Hey JD

 

>When boring hammers, should we favor strictly the string heigth  
>minus shank center heigth at the cost of no straight hammer heigth  
>at rest (reflecting the not straight strike line heigth at strings)  ?

JD wrote
Broadly speaking I agree with Dale Erwin, as far as he  goes, except 
that I aim to have each hammer strike the string at exactly a  right 
angle.  I don't follow the reasoning as regards  over-centring.
 
The logic you share should indicate an error in the  approach you suggest.  
Since the strings and key bed are not parallel to  each other a hammer mounted 
at right angle to the shank is going favor hitting  the back side of the 
hammer striking point. Also altering the bore distance by  making it longer changes 
the geometry of the entire action as the capstan &  every other reg screw 
need to be turned downward. 
    Some tech's even allow for the anticipated  wear of the hammer adding a 
mm or 2 to the bore length.  This is huge  design error in my opinion.  Having 
run across pianos with this  configuration I can tell you they do not play 
well.
  IMO a new set of hammers bored & hung in the correct  place to the string 
plane as I described will tolerate only one heavy filing  before the action is 
no longer in it's optimal geometric performance range &  over boring isn't a 
remedy for this,  a new set of hammers  is
 
 
 
 It 
might be argued that the shank bends under a heavy blow and  therefore 
tends to cause the hammer head to under-centre slightly, but given  
the rigidity and thickness of modern shanks, particularly the 
hornbeam  ones, I doubt if this is significant and would need to see a 
slow motion  movie to be convinced.  Nevertheless I think it would be 
a valid  research exercise for someone with the equipment, if it 
hasn't already been  done.
 
  Actually I believe the Kimball video shows the shank  bending

Let me re-emphasise the importance of taking into  account the slope 
of the strings, which is considerable, and most critical,  in the high 
treble -- but this slope needs to be measured throughout the  scale 
for every piano and factored into the bore angle.  If this is  
ignored, the hammers in the extreme treble will under-centre.
  Exactly where I'm coming  from


Aesthetics is a broad concept and applies to  function and design in 
all its aspects.  There is nothing intrinsically  beautiful about a 
straight line, as any  ancient Greek architect could  tell you.  Is a 
clothes-line or a telegraph wire intrinsically ugly?  :-)
  Now we agree on  that!!
  Dale

JD




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