Bernt Damm wrote:

> Some other point to note here is that the energy transmitted from
> the hammer to the string is constant, flex or no flex of shank,
> because the moving mass does not change.  I therefore say that it
> will not influence the volume of sound at all if the shank bends
> a little or not.

Bernt,  The shank _does_ flex, at least on the upright piano.  Upright
hammers in the treble are glued on with a slight downward pitch.  In
other words, the hammer is not exactly 90 degrees from the shank.

The hammer striking point actually raises a little when the note
is played hard, due to the flexing of the shank.  I am not absolutely
sure why this is so, but if the procedure is not followed when
installing new hammers, you will have a very weak treble.  (Been there,
done that!)

Take it from a guy that has got the striking point off on an upright
more than once.

If you raise an action by 1/16, there will not be that much difference
except when the piano is played hard.  You will quickly see that the
treble tone goes away under these conditions.  That is due to the
flexing of the shank and the striking point of the hammers raising
slightly when played moderately hard.  Hope this helps.

Best Regards
Andy Taylor
Tempola Music Rolls
http://home.swbell.net/tempola/index.htm