Capo bar file

[Michael Wathen 556-9565]

Give me more information.  Are you refering to Ken Slater of the Cleveland
chapter?  What's the address of the company that markets this file and how much
does it cost.

By smaller radius of the capo bar do you mean a sharper curvature?  My own
quasi-scientific research leads me to believe that a not so sharp curvature is
more beneficial than one that is sharp.  Why?

First: The strength on a surface is dependent upon the mass density just below
the surface.  For example,  craftsman woodworkers are well aware that a sharp
chisel will remain sharp longer if the bevel of the chisel is not to acute.  In
the case of the capo bar it seems that you could expect more string definition
or better termination with a sharper curvature just like you could expect the
chisel to have a sharper end with a more acute bevel but this good string
definition deteriorates rapidly to a level below that of a moderate curvature.
Razor blades do not remain sharp very long.

Second, a larger surface area for the string to contact on the capo bar
ultimately aids in the duration of the tone, the reason: static friction.  It
has been shown that a string vibrates not only in the direction of the hammer
blow but in fact the direction perpendicular to the hammer blow can viewed as an
energy reserve that captures a good portion of the energy from the initial blow
and gradually gives it back to initial blow direction which in turn gives it
over to the bridge-board (Weinreich, JASA 1977 I believe).  In terms of a grand
with a capo bar this means that the termination of the string needs to be not
only the obvious up direction but just as importantly it needs to have a side
termination at the capo bar.  This can only be accomplished with a strong enough
static friction force that can keep the string from moving sideways.  It is my
conjecture that the Zinging sounds that are so often anoying in this section of
the piano most likely occur because static friction becomes kenetic friction;
energy is lost by sideways movement of the string at the capo bar.  By the
same reasoning one should probably not use any type of lubricant on the capo
bar.

I also remember some discussion maybe ten years ago about hardening the capo bar
through heat treatment.  I believe that Mcmarrow and Grossman were its principal
enthusiast.  I quess the believe was that a harder surface would resist the
tendancy of the strings to cut into the capo.  That seems good enough but is it
desirable?

Michael Wathen