hammer velocity

[Richard Moody]

----- Original Message -----
From: Classic Touch Ent <classictouchent@comcast.net>
To: Pianotech <pianotech@ptg.org>
Sent: Friday, April 25, 2003 12:40 PM
Subject: Re: Key Leads and Inertia


 BUT/AND isn't the only factor that affects loud/soft
or tone quality (once the piano is prepared) the VELOCITY OF THE
HAMMER
when it strikes the string? --- Best, Rich Olmsted


YES!  The hammer as it strikes the string is actually slowing
down in theory.    A major consideration of the design of the
piano action is that the hammer must leave the  impelling device,
(jack) and continue to travel for a tiny distance free and clear,
 strike the string, rebound, and then come back in contact with
the action mechanism which must now "catch" the hammer.
    The only aspect of the travel of the hammer the pianist can
control is its velocity.  There might be an argument about this in
physics because of the difference between velocity and
acceleration. As the pianist pushes on the key, the hammer is
accelerated toward the string. After  some point (called let off),
the  hammer is no longer in any control of the pianist.  If
Newton's law (Force = mass times acceleration) stands, when let
off happens the hammer is no longer being propelled by a "force".
No force, no acceleration. In the physicists reality the hammer is
actually slowing down.  But for our purposes the hammer does hit
the  string with a certain velocity, and this velocity we believe
is determined by fast the pianist depresses the key minus any
friction in the hammer flange center. ]
    Now there are some things outside the realm of physics that
are better left to intuition and old fashioned empiricism.
(knowledge
gained by experience)   For example hammer shaft flex.   You can
see that the hammer is accelerated by the knuckle and from the
position of the knuckle you can easily imagine the hammer shank
flexing on a sharp blow.   Now this flex could add to or detract
from the
deceleration.   If the shank is still flexing when the hammer
strikes,  that is further slowing down.  On the other hand if the
flex then springs back right before the hammer hits the string,
the hammer then could actually
be accelerating.
---rm


"If I have made any valuable discoveries, it has been owing more
               to patient attention than to any other talent."
      Sir Isaac Newton (1642-1727); English mathematician,
physicist.