Rib scaling question

[Erwinspiano@aol.com]

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Mike /Ron
   Mike, Thanks  for the kind comments of  appreciation.
  Mike this stiffness question is surely relevant to  us all. How stiff is 
too stiff?
  I've maintained that a too stiff system yields a  sustain that must be 
extricated by stiffer & stiffer hammers until it's not  retrievable. ie too much 
bearing on an otherwise well supported belly  chokes the sound
     I agree with Ron, usually a safe  thing to do, grin, and it's also true 
in this  case the  extra ribs are primarily for crown support & turning them 
perpendicular to  the bridge & obtuse to the grain angle of the sound board 
increases  stiffness without adding mass.  Del's/Rons have been saying  this for 
years now & I finally proved it to myself.
     The upper part of the treble board in  the last octave & half area is 
quite stiff simply because the  board spans an ever decreasing span between 
belly rail and curve side of  case. Combine this with a stiff bridge on top in the 
same vicinity ands  some short spruce ribs and this is going to drive the 
tone.  Of  course adequate down bearing assumned.  
    Sincerely
  Dale Erwin
 

>  Primarily for Dale Erwin, (who was generous enough to share his  thoughts
> and his photos with us all through the PTG Journal) but  anyone please feel
> free to chime in if you've got thoughts on  this...
> 
> Most rib scale modifications I've seen / heard about  involve additional
> ribs, closer together, and perpendicular to the  bridge, in the treble. 
> Reasons:  maintain crown, increase  impedence for longer sustain.  I'm
> wondering how critical it is  to get enough but not too much increased
> stiffness.  Have you  ever gone too far?  What were the resulting symptoms?
> 
>  thanks
> 
> Mike

The addition of treble ribs is  realistically more important to crown 
support in the killer octave than to  high treble stiffness. The 
symptom of too much stiffness in the high end  is that short sustain 
screaming treble we talked about a couple of weeks  ago. The cure is 
mass to get the fundamental resonant frequency  down.

Ron  N
_______________________________________________


 
 
Dale  Erwins Piano Restorations 
4721 Parker Rd.
Modesto, Ca  95357
209-577-8397 cell 209-985-0990
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