What's all this I hear about Inertia ?

[Fenton Murray]

David,
I don't think your being lit up here, just enlightened, if you want to 
listen. I went through a lot of the same head scratching as you. I don't 
have a background in physic, but I did my best to study what was happening 
in the key. Checking out books from the library and applying a lot of what I 
learned as a pilot regarding weight and balance. I was convinced that the 
small amount of key travel would not be significant and therefore another 
lead or 2 wouldn't hurt if it got my balance weight where I wanted it. I did 
a lot of experimenting with pianos that had heavy hammers, some with assist 
springs that I removed. No matter how nice a static measurement I achieved, 
I could always feel when there was too much lead in the key. These were 
pianos that I re-weighted 2 or 3 times, playing and feeling them each time. 
Not the efficient way to make money, but the only way I seem to be able to 
learn.
If you have heavy hammers, or a high action ratio, or even worse both, you 
will start to end up with too much lead in the key unless you are using 
assist springs. These actions are not going to 'feel' right even though they 
may have great numbers. I don't know any way too measure this easily with 
weights at the key board, but I have become pretty good at feeling it 
through all the great mistakes I've made.
Respectfully,
Fenton
----- Original Message ----- 
From: "David B. Stang" <stangdave at columbus.rr.com>
To: <pianotech at ptg.org>
Sent: Monday, September 29, 2008 4:07 PM
Subject: Re: What's all this I hear about Inertia ?


> After being almost instantaneously treated to some scolding,
> sarcasm, condescention, and arrogance because of my previous
> post, I will try again.
>
> I was wrong about saying that an overall heavier key would feel the
> same as another one with identical downweight. Here's a thought
> experiment to show why: Even in a weightless environment, it takes
> more force to accelerate something with more mass.  So, it takes
> more finger force to accelerate more mass.  duh. sorry!
>
> And if I was not clear enough in my use of the term "dynamic range"
> I was just trying to say that since a faster keystrike results in a louder
> sound on a piano, then the less able the finger is to accelerate the key,
> the less loud the sound will be.
>
> But I will reiterate my original point. Mass is the same as inertia. And
> mass is proportional to weight. So on earth, two things with the same
> weight have the same inertia. That's the point I had been kind of hung
> up with.
>
> Rotational movement is another kettle-o-fish altogether, and has
> nothing to do with the point I (admittedly ineptly) was trying to make.
>
>
> David B. Stang
> Still green and trying to figure things out
> Columbus Ohio
>
>
>
>