Inertia, was "Grand Touch"

[Cy Shuster]

Measuring FW alone won't tell you the dynamic inertia.  50g downweight could 
be achieved with 50g at the end of a massless key (standard physicist 
issue), or 1000g right in front of the balance pin, but they'd sure feel 
different to the pianist.

The front side of the key has the weight between your hands and the fulcrum, 
like a wheelbarrow.  You could put a cement block up by the wheel in the 
barrow, and measure the downforce on the handles.  Take out the block, put a 
much lighter weight right on the handles, the downforce is the same, but 
moving the handles up and down a foot or so you'd feel a lot more inertia 
than with the cement block in front (am I right on this, you physicists?).

For reference, Stanwood's "See-Saw Science" (a PDF):
http://www.stanwoodpiano.com/seesaw.pdf

--Cy--
shusterpiano.com



----- Original Message ----- 
From: "William R. Monroe" <pianotech at a440piano.net>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Wednesday, July 12, 2006 4:41 PM
Subject: Re: Inertia, was "Grand Touch"


> Hi Cy,
>
> Haven't read Stephen's paper yet.  Will tonight, then, more questions, I'm
> sure.  However, just my intuitive take with your example.
>
> Consider the other option, and how they compare.  I do not dispute that
> installing weights at the end of the car (key) increase inertia.  I only
> question whether inertia would be different in the case of hanging a small
> weight at the end of the car (key) vs. installing slightly more mass near
> the pivot point.  Since the pianist feels/activates the key somewhere near
> the end of the stick (for arguments sake), it would seem that the FW of 
> the
> key would be the point at which we take a mass reading to compute inertia 
> in
> a played key, since some of that mass (regardless of placement) is 
> supported
> at the balance rail.
>
> Just my musings.  God I love this kind of stuff!  Awful fun to learn from
> you all.
>
> William R. Monroe