Hammer weight

[Don_Mannino@yca.ccmail.compuserve.com]

     Regarding tonal energy and hammer mass, I would like to suggest
     another way of thinking about the balance of leverage, hammer weight
     and tone projection / power.

     It seems to me that the hammer's inertia is the deciding factor in
     transmitting power to the strings. Inertia involves a combination of
     the motion of the hammer (its speed, really), and the effective mass
     of the moving part (hammer / shank mass together with the radius of
     the arc traveled).

     Let me lay out a few premises, and I'd welcome you-all's comments.
     Let me start with a generic grand action as it came from it's
     manufacturer.  The only constants I want to keep for now are the
     length of the shank, i.e., from the shank center pin to the center
     line of the hammer, and the speed of the key's motion.

     1. If the mass of the hammer is lowered and the speed of the hammer
     remains the same, the energy imparted to the string will be lower.
     Because of the reduced mass the contact time will go down, and the
     tone will be brighter.  The total inertia of the hammer is lower.

     - Lower hammer mass
        Brighter tone
        Less powerful tone
        Touch weight will be reduced
        Friction will be reduced

     2. Going back to the original action again, leave the hammers the same
     but make the knuckles smaller (or you could move them closer to the
     center pin, but that's kind of hard to do!). Now the mass remains the
     same but the speed of the hammer will be increased (as long as the
     pianist can overcome the extra "touch weight"). The inertia of the
     hammer is increased.

     This may be a bit unrealistic - the pianist will not naturally
     overcome the increased resistance at the key from the faster leverage.
     We can fix that in #3 below.

     - Smaller Knuckle
        No change in brightness
        More powerful tone
        Touch weight will be increased
        Friction will be increased

     3. Combining the two above, if done correctly, should allow the tonal
     power to be equal.  If the knuckle is made smaller first, then the
     hammers can be lightened until they bring downweight at the key back
     to where it was before shrinking the knuckle.

     - Light hammer and smaller knuckle (or other change in leverage)
        Brighter tone (from reduced contact time, low hammer mass)
        Equal power (increased inertia from higher hammer speed cancels the
                lower mass of the hammer).
        No change in touch weight
        Equal or slightly reduced friction

     David, please correct me if your research shows that the impact of
     hammer speed on inertia does not adequately compensate for lower mass
     in the hammers.  My statements here are more empirically than
     scientifically devised.

     BTW, I have heard a Steinway D with _extremely_ light hammers being
     used in a concerto in a large concert hall, and there was no problem
     hearing the piano - the piano sound was more than ample. One piano
     does not make a scientific proof, though, so maybe this was a
     combination of an unusually good instrument and a capable pianist.  I
     had a chance to play the piano, and it had a huge tone.

     I have had similar experiences customizing new pianos with soft
     hammers right from the factory.  By lightening the hammers and
     speeding up the ratios the results were a much brighter tone, with a
     bigger, fuller sound with little or no hardening of the felt.

     Let me know what you think of this idea of balancing effective mass
     and velocity to get the inertia needed.

     Don_Mannino@yca.ccmail.compuserve.com