Inertia, was "Grand Touch"

[Ron Nossaman]

> About 2 years ago this question was discussed at great inconclusive length on CAUT.
> 
> Probably the most important question was "can the pianist feel a difference?"
> 
> No one doubted that weight location could make a difference in the moment of inertia of the key. But the key is a small part of the system.  Other parts, especially the hammer head, contribute their moments of inertia as well.
> 
> The question becomes "What percentage of the total of what the pianist feels can be changed by changing the moment of inertia of the key, and what percentage is controlled by the rest of the system? Is it enough to matter?"
> 
> Take a look at Stanwood's lever drawing.
> 
> Note the 10 gram hammer at the end of the lever that is 5 times longer than the key front. What is the moment of inertia represented by that part of the system?
> 
> Now look at the frontweight, 20 grams, at the front of the "0ne unit long" key.
> 
> Change that to 40 grams at the "one half unit" location.
> 
> That makes a big difference in the moment of inertia of the front end of the system taken alone, but how much change does it make in the entire system?  Is this enough to change the performance response of the piano a perceptible amount?
> 
> Ed Sutton

Thanks Ed. I've brought this up repeatedly, but it seems to 
fade into quickly receding echoes immediately. The lead is 
there in the key for one reason - to balance the hammer 
weight, at an approximately 5:1 ratio courtesy of the leverage 
train. The inertia effect at the hammer is considerably 
greater than that at the key, regardless of mass distribution 
in the key. So how much dynamic difference does it really and 
truly make in the inertial response of the system, rather than 
in the isolated key, having the key leads smaller at a greater 
distance from the fulcrum, or larger at a lesser distance with 
the same static weigh off? Does anyone have any real information?