laminated ribs

[Delwin D Fandrich]

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From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of
Erwinspiano@aol.com
Sent: February 18, 2006 11:31 AM
To: pianotech@ptg.org
Subject: Re: laminated ribs



In a message dated 2/18/2006 9:26:00 A.M. Pacific Standard Time,
rnossaman@cox.net writes:


  Dale wrote
>   Ok Now I,lm confused.  If were only trying to support only 400 to 600 
> lbs. of down bearing force as Del inferred recently or whatever one 
> calculates this to be,  then what's all the fuss about.  

My loading of new boards these days is typically half again 
over 600 lbs.


  Ron, so you are saying a 900 lb bearing load is probably an in the ball park
average plus or minus for various sizes of pianos  & string scale tensions.
  Then  my comment a couple weeks ago about bearing being 1000 lbs  or more
depending on who you ask wasn't that far off this figure even though Del
disagreed with that as  being "excessive." 
 
 

 
Consider a basic scale of moderately high tension. Say 40,000 lbs. overall. With
this string tension 1,000 lbs of string downforce equals 2.5% of scale tension.
That is quite a lot considering that most companies are claiming string
downforce more on the order of 0.5% to 1.5% of string tension (which would be
200 to 600 lbs). I thought I was setting my initial string downforce pretty high
at around 1.0 to 1.5%. I don't like thinking about what I'd be doing to a board
loading it up to 2.5%. I can't imagine it being happy enough at that level to
want to stay there.
 
Del

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