Action Geometry

[PianoGuru@aol.com]

In a message dated 95-06-21 14:16:00 EDT, Steve Brady writes in response to
Serge Harel:

>> When the key is half way down you suppose to have a line
>> between the hammer flange centre pin, the capstan-wippen >>contact point
and the wippen flange centre pin.
>
>     I think what Serge meant here is that there should be a >straight line
between the *bottom of the key at the balance point*, >the capstan-wippen
contact point, and the wippen flange center >pin.

I believe we are confusing two imaginary lines here.   The line that Serge is
referring to is a straightline from the hammer center to the whip center,
intersecting the point of contact of the jack to the knuckle (not the capstan
to the whip).  The straight line referred to by Steve is correctly stated.
 Of course both of these lines are assuming that the key is halfway depressed
 Both of these straight line rules are valid and relate to the same principle
of geometry. In each case,  friction is reduced at the contact point in
question, not that these concepts are universally observed.

Frank Emerson