Key Leads and Inertia

[Keith Roberts]

If the key lead is half way between the balance rail and the front, the
front will have to accelerate at twice the speed to  accelerate the lead
faster than the acceleration of gravity 9.8 meters/sec/sec. Half the
distance is covered in the same time. Conversely, the acceleration of the
front of the key is increased by placing a point of mass on a second class
lever and moving it toward the fulcrum. Imagine the pendulum or metronome,
the speed or frequency increases as the mass moves toward the pivot point.
The distance traveled doesn't change.
Keith Roberts
----- Original Message -----
[link redacted at request of site owner - Jul 25, 2015]
To: <pmc333@earthlink.net>; "Pianotech" <pianotech@ptg.org>
Sent: Friday, April 25, 2003 6:29 AM
Subject: Re: Key Leads and Inertia


> Paul McCloud wrote:
> > John:
> > I fail to see what this has to do with real-world dynamics.
> > Since the lead is integral with the keystick, not suspended by a thread,
> > the inertia is going to be the same no matter how much acceleration is
> > generated by the pianist's finger.  What am I missing?
> > Paul McCloud
> > San Diego
>
> Paul,
>
> I am just trying to visualize how a lead in a key
> would react to the acceleration of the key during
> play. A lead in a key assists the depression of
> the key at lower dynamic levels of play, ppp and
> pp. It does this because it has a negative
> acceleration - gravity - pulling on it.  Only
> after the lead is accelerated past the point of
> falling will its inertia be felt as a resistance
> to depressing the key.
>
> This means that if you install a lead in the key
> in order to lower the static down weight you
> assist the player if they are playing at a soft
> dynamic range (the action feels lighter). When the
> player increases the level of dynamics beyond
> pianissimo the lead begins to hinder playing (the
> action feels heavier).
>
> John Hartman RPT
>
> John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
> Rebuilding Steinway and Mason & Hamlin
> Grand Pianos Since 1979
>
> Piano Technicians Journal
> Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]
>
>
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives
>