Keylead inertia and leverage

[Jon Page]

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At 05:10 PM 04/05/2001 -0700, you wrote:

>I must get in here!  I haven't been hampered by a formal education, but I
>have been exposed to alot of this technical stuff.
>
>Please excuse my lack of understanding of the finer points of inertia and my
>use of made up terminology.
>
>Let me hypothesize that an infinite weight applied to an infinitely small
>radius, would have no inertia in the rotational mode but have lotsa inertia
>in the horizontal mode.  Vertical mode would introduce gravity and confuse
>the issue.  ( we all know that there is no such thing as gravity.  The earth
>sucks.)
>
>Now, since more weight closer to the balance rail will still give the same
>dw/uw the inertia will be less due to the radius of the weight. Now, someone
>said that the smoothness of the uw/dw is affected.  Let me suggest that the
>friction is increased due to the dead weight of the increased weight closer
>to the balance rail pin.  Now the rotational movement of the key is
>restricted due to the additional weight, resulting in erratic dw/uw
>measurement.  Additional (dead weight) at the balance rail will compress the
>balance rail felt punching and add up/dw due to the added weight.
>
>Now, my question is:  Is that why the patent for the accelerated action
>includes the round surface of the balance rail to compensate for the
>increased weight of the lead in the keys nearer to the balance rail.
>I haven't read the patent so I might be out in left field.
>
>I believe someone said that S&S doesn't use this anymore.  Would that be
>because the price of lead went up or it wasn't such a good idea anyway or
>nobody appreciates or understands it?
>
>I don't have a clue.???????
>
>Carl Meyer

 From what I have observed, the balance rail bearing maintains the fulcrum 
close to the pin.
If you scrutinize the movement of the key on a flat punching, you may 
notice that
the key pivots from the back of the punching to the front; an increasing KR 
as the
key depresses.
Jon Page
As for the other stuff, re-read this:
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To: <pianotech@ptg.org>
Subject: Re: Keylead inertia and leverage (was Re: Ideal leading pattern:)
Ric,
This is one of those counterintuitive concepts:  how can more weight result
in less inertia?  The key (no pun intended) is in the leverage.  The closer
the weight is to the balance rail, the shorter the distance it moves during
a keystroke.  Less acceleration.  The closer the weight is to the balance
rail, the more leverage is available to the pianist to overcome the inertial
resistance.  These two leverage effects (less acceleration, more mechanical
advantage) combine to cause less resistance to be felt by the pianist.  If
you can struggle through the math of my earlier post, I think you'll see how
it all works out.
Mike

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