What does the moi feel like?

[Richard Brekne]

> Ed Sutton wrote:
> 
> Dear Physicists of the List-
> 
> Please comment on this thought:
> 
> When I press the piano key, the resistance to movement I feel consists
> of three elements
> 1) Friction
> 2) The pull of gravity on the hammer and wippen, partly
> counterbalanced by the pull of gravity on the keyfront.
> 3) The combined MOI's of the various moving parts.
> 
> Therefore, if I can
> 1) reduce the friction to zero, and
> 2) use a wippen assist spring to produce a balance weight of zero, the
> only resistance left would be
> 3) the combined MOI's of the key, wippen and hammer.

Well... to begin with if your BW was indeed zero, then your keystick
would tend to center in the middle of the stroke... especially if you
got friction down to nothing. But I think I understand where you are
going... so lets say the action is in equilibrium at 5 degrees backwards
tilt of the keystick... balanced at the rest postion as it were.


> 
> What I would feel then, in various key strokes, would be whatever it
> is we are talking about.


What you would feel is dependant largely on what velocity you accelerate
the key to, and how fast you accelerate it to that velocity. At max
velocity with fastest possible acceleration you will feel say 98% MOI.
At the other extreme it will be weight and the effect of gravity on the
balance and counterbalancing. And at all stops inbetween some degree of
both.... graduateing from the one to the other dependant on how hard you
play.

> 
> Could I make or buy a gauge to measure this?

Nope... at least not for practical purposes. Nor do we need one. We just
need a very good overall picture in our minds of how important each
moment is relative to how pianist play. And that will give us only a
general guideline from which to help us base decisions for any action
and pianist.

This is one of the reasons that Stanwood works as good as it does
really. That system ASSUMES that both MOI and WEIGHT are very
significant factors for most levels of touch. So both are significantly
(very much so really compared to older weigh off styles of setting up
and action) addressed as a matter of course in executing a Stanwood PTD
balancing.

But again,,, Stanwood does not address action compliance, nor the effect
of increased mass on friction and wear and tear, nor does it DIRECTLY
address MOI levels, those being simply evened as a <<by-product>> of his
static balancing.

> 
> Does this line of thought seem useful in understanding the situation?
> 
> For example, has anyone felt a key such as I describe?
> 
> Ed Sutton

Cheers
RicB