Hi Ric, You wrote: > The leads output more force then it > takes to accelerate them in all cases because they are (as seen by the finger) > on a second class lever Ah, but with very forceful playing, the keystick accelerates very quickly, and the downward force exerted by gravitational acceleration on the key leads pales by comparison to the upwards force of the keystick/leading against the finger (in direct opposition to the downward force that is accelerating it). The greater the inertia, the greater this force. Case in point: place a 1 kg mass on each side of the balance rail. Adjust BW to something very reasonable. Now pound the key and try to produce your loudest fff. If you're a really strong pianist with really heavy arms and beefy fingers, you might be able to produce an mp. Why the difficulty? It's because the "oppositional force" of the key inertia is far greater than the small amount of assistance the key leading might give you (with regard to touch weighting). How do key leads and wip springs change in downward force at different levels of play? They don't. Gravitational force on the keyleads is constant. Spring force is also constant (for a given position in the stroke). The only difference is that springs can move very rapidly, owing to their very low inertia, and lead weights can't. So with rapid key acceleration, the leads fight back, while the springs don't. As I've suggested to you before, there's another experiment that provides a better feel for the real-world consequences of key inertia: Bundle up 3 or 4 nickels (15 or 20 g mass) in some tape and suspend the tape by a string between the thumb and third finger. Now "trill" the nickels like two piano keys. This isn't a lot of mass, and yet the force necessary to accelerate it would be a significant component of total force on the key. I accept that the hammer accounts for most of the total inertia, but there's still considerable inertia in the keystick. Hammer inertia is fine, as the hammer's kinetic energy is delivered into the string. Keystick inertia is not fine, as the keystick's kinetic energy is only delivered into the front rail. IMO, the only function of keystick inertia is to make the piano feel "familiar" to pianists who are trained on pianos with lots of keystick inertia. However, I doubt it results in a better instrument, and I would expect that the instrument will ultimately evolve to a lower keystick inertia and a heavier hammer. As you suggest, it would be interesting to tease out the relative contributions of these different components! Peace, Sarah
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