Jeff Davis suggested yesterday that "a very firm blow in a grand can
make the hammer shank bend, or "whip", and that "it may be possible for
the hammer to accelerate after let-off, as it unbends."

A hammer shank, if bent, will have some energy stored.  It will release
that energy as it straightens out, but there is nothing for its force
to react against.  Therefore, the center of gravity of the hammer/shank
combination will still decelerate.

The center of gravity of an object can only move if it is acted on by
an outside force.  Therefore, after let-off, the center of gravity of
the hammer/shank combination will not be affected by the straightening
shaft, and will begin decelerating.  As the center of gravity of a
hammer/shank is very near (if not within) the hammer (due to the
hammer's larger mass), hammer acceleration is very likely unaffected by
a straightening shaft.

Apparently many of us have too much time on our hands.  Really now,
discussing hammer acceleration after let-off.  Aren't we really here to
enjoy the music?  (I plead guilty.  The technical discussion was too
enticing to pass up.)

Ray Fairfield