Richard Brekne wrote: > > Much has been made of the idea that more mass requires more effort to > move, yet at the same time it is ignored that once that mass is moving > it takes less effort to keep it moving. In reality these are flip sides > of the same coin and to some degree whats good about the one side is bad > about the other. Well not exactly. Acceleration (change in speed) not velocity (constant speed)is what you need to look at in the action. Acceleration is the change of velocity and it always requires force. While it's true that in strict physics it takes no force to maintain velocity (as long as there is no opposing force like friction or the pull of gravity) this is not much of a factor in regard to the pianos action. In order to play a note the key is accelerated from 0 velocity to some greater velocity during a short period of time. There is really no time for the player to benefit from any momentum (mass time speed) that may happen in the action. While playing the action bits and pieces are accelerating or decelerating. I can't think of any time when a part is moving with constant speed except when the note is not being played at all. Of coarse there is the escapement. But even a hammer flying free from the rest of the action feels restraint. It is being held back by friction and the pull of gravity. It is decelerating. This is why the let off is kept close to the string - the less of it the better. Any momentum the hammer has as it impacts the string was bought and paid for by the force applied to the key. > In answer to your querry, it is my guess that the reasoning for the > acellerated action has more to do with key motion after the finger gets > it moving, and after it rebounds of the keyfront cushion, as this is > where more inertia is more an aid then a hinder. No. More inertia does not help the key to rebound. When you play a note the key is accelerated till it stops (decelerates) on the front cushion. It must accelerate again to come back up. Reducing the inertia (the resistance to acceleration) helps with both accelerating the key while playing and the acceleration of the key coming back up. It makes the action easier to play and faster as well. 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]
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