Key Inertia

[Sarah Fox]

Hi Ric,

> > Twice the hammer mass,
> > while preserving the same jack force and stroke, would mean 2^.5 the
> > velocity, true, but when the hammer hits the string, the same amount of
> > kinetic energy is transferred to the string.
> >
>
> Ok Sarah... same kinetic energy.... but you demonstrated quite clearly
below the
> effect this (same energy for differeing mass* velocitycan have on what
happenes
> to the velocity of whats being hit.
>
> So what now ?

Soooo....  You're right.  I was trying to simplify, and this argument
assumes no impedance differences between the hammer and string.  However,
when you introduce considerations of mechanical impedance (which what I did
with the bowling ball/marble argument -- and which is the point you're
raising now), there are indeed differences in efficiency from
adding/removing mass to/from the hammer.  I discussed this in another
posting, specifically with regard to impedance matching between the hammer
and string.  I really don't have any feel for how big an effect this would
be.

------------------

Somewhat off the subject, but still related, Mark wrote:

>>So, how to explain Ric's example that the favorite action of his
>>students has a SWR of 6.2 and is 'heavy in a good way'.  How high is
>>too high?

> I wish I knew!  Queried Ric on other parameters of this instrument, but
nothing really jumped out.  High SWR, top med SW, low friction (as in worn
out), unassisted BW=55g, he didn't way what the assisted BW was though
(Ric??).

> Obviously I can only speculate, but a modest BW, say 38g with some inertia
behind it gives you a nice sense of "throwing" a weight when playing.  And
with low friction, you give it a push and it keeps going.  There is also a
good sense of control - it takes a bigger change in force to change the
speed of the hammer.  Some pianos you feel like you're pushing the hammer
rather than throwing it.

Yeah, that's it!  That's my Wissner!  That's the "good" sort of "heavy" I
was trying to describe!  I wish I could try out your worn out piano there in
Norway to see if it's my worn-out Wissner's long-lost twin.  :-)

I submit to all of the friction proponents on this list that pianists don't
*necessarily* like friction!  ;-)

Peace,
Sarah