pianotech-digest V1997 #1919 (long)

[JIMRPT@AOL.COM]

In a message dated 8/24/1999 4:01:03 AM, richardb@c2i.net writes:

<< If you replace the pivot with a wider, rounder surfoace,then
the flexing of the string is dispersed in several directions, thus increasing
friction and thereby wear. >>

Richard;
 I am not Ed nor am I a University web site but............. :-)
  Whatever result widening/rounding a surface of any given material would 
give, increasing wear (i.e. quicker, deeper grooves) is not one of them.  To 
decrease wear on any given point all one needs to do is spread the load which 
in effect is what "rounding" a termination does. Given a harder material and 
a softer material, both subject to grooving, and giving both materials a face 
 with a V shape of the same crossectional size the softer material will will 
develop grooves faster than the harder, all other things being equal.
  If you change the shape to U shape for the softer material and keep a V 
shape for the harder material the 'groove rate' would approach equality, and 
depending on cross sectional sizes the softer material may groove much more 
slowly than the harder, all other things being equal. Conversely  If you use 
the V shape for the softer material, and the U shape for the harder, the 
softer material will develop grooves much faster than the harder, again all 
other things being equal.
  While there may be more 'friction' on a 'moving' entity across a wider face 
than a narrow face this added friction does not relate directly to more wear 
on the surface that remains stationary, i.e Capo bar except as a coefficient 
(?) of hardness would dictate.  

  Now as I understand Ed's contention he says that increasing the hardness 
and increasing the cross sectional size will cause grooving much faster....If 
my understanding of what he says is correct then I must respectfully disagree 
with him.  Load spreading is a well known principle and not a theory. Load 
spreading is what allows a 50 ton tank, with 'tracked' propulsion, to 
traverse sandy terrain without sinking in too deeply...whereas the same 50 
ton tank with four or six 'wheels' would sink in much further and perhaps not 
be able to traverse the same terrain as its tracked cousin.  The difference 
here is 'load spreading', or 'footprint' and it is mostly linear the same as 
a wires termination at the capo...the same principle applies..........i.e. 
more footprint less grooving/less footprint more grooving...ya can't have it 
both ways Cuz :-)

  Now Ed says that a harder plate with a rounder capo will cause deeper 
grooves?
KInda flies in the face of my limited wet storages' processing capacity :-) 
but......I am amenable to being convinced otherwise.
Jim Bryant (FL)
P.S. Besides I thought the general consensus of thought here was that the 
V-pro plate seemed "softer" than the sand cast plate. <:(