[CAUT] Wire Stretch

[Bob Hohf]

Why would you ever want to set the same downbearing force per unison when
the unisons are so unevenly distributed along the length of the bridges?
The top two sections of a typical concert grand contain 43% of the strings
on 20% of the total bridge length.  A smaller piano may have 46% of the
strings on 29% of the bridge.  Setting a uniform downbearing per string will
set up a tone-stifling imbalance in the downbearing force along the bridges.
For 20+ years I have been setting downbearing on the principle of uniform
force per unit of bridge length.  This produces much less force per string
in the high treble and much more in the tenor.  I don't measure angles.  In
Parts 5 & 6 of "Recapping Bridges" in the 1999 Journal, I present a
discussion of downbearing as force, not dimension, and describe a method of
setting a more uniform load distribution.  I'm sorry it's too involved to go
into detail here.  I know of one other rebuilder besides me who does
something along these lines.

 

Bob Hohf

 

 

 

  _____  

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of RicB
Sent: Saturday, April 28, 2007 3:04 AM
To: caut at ptg.org
Subject: [CAUT] Wire Stretch

 

Yes they do what Bob ?  Graduate downbearing angles so as to get exactly the
same amount of downbearing force on each unison ?

RicB

>Course the problem with this notion is that equal tension by no means 
(in fact dictates the opposite) of equal amounts of downbearing pressure 
across the scale unless one compensates by graduating the downbearing 
angle appropriatly...which I dont think anyone does.<



Yes, they do.  Check out your July and August 1999 Journals

Bob Hohf

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