Keys and MOI

[James Ellis]

Hey Fellows,

I'm getting confused as to who said what, but I'll say this, and I think it
will be very close to what Richard said in his latest post.  I might change
the emphasis a little bit.

If you start with evenly graduated hammer-head weights, and you are
consistent with the shanks you use, then you will automatically have evenly
graduated strike weights.  If you are then consistent with the other action
parts and geometry you use, and you weigh off the keys for even balance
weights, and you are consistent in the way you weigh off the keys, then you
will automatically have evenly graduated moments of inertia in the action.
The main factors determining what that will be are, 1) the hammer head
mass, 2) the action geometry.  The masses of the other parts of a common
piano action have less effect on the total MOI.

If you want to feel what the MOI of the action feels like, that's easy to
do.  Simply do some rapid repeats down on key #1, and then do the same
thing on key #88.  If your balance weitght is consistent, and nothing is
sluggish, the big difference you feel will be the difference in the MOI.
It's just that simple.

Jim Ellis