Key Leads

[Gordon Wilson]

On Wed, 26 Jul 1995, Michael Wathen 556-9565 wrote:

> >>>>
> Once again I will raise the dreaded moment of inertia to answer this
> one. There is a difference. The static (touchweight) is based on the
> first moment of the key about the pivot and varies as the distance
> between lead mass and pivot. The dynamic (feel) of the key is based
> on the second moment (moment of inertia) and varies as the square of
> the distance between lead mass and pivot. Thus when you move the
> leads to the middle of the key and *slightly* increase to balance the
> touchweight you reduce the moment of inertia significantly
> (even though the leads are a bit heavier)...hence the key feels
> different.
>
> Another analogy...golfclubs are (or used to be) sold in sets which
> were statically matched (i.e. the first moments about the grip were
> the same)...called `swing weight', which is identical to D.Stanwood's
> strike weight! Recently some manufacturers started making sets that
> are dynamically mateched (i.e. the second moments are the same). You
> can't match both first and second moments, because one varies in
> proportion to distance whereas the second varies as the square of the
> distance.
>
> Stephen Birkett (Fortepianos)>>>
>
> Excellent analogy!
>
> I have removed leads and rewieghted.  After the leads are removed I use
> a Forstner bit to make the hole clean (they are usually tapered). Next
> I make appropriate size plugs to go in these holes.  Now I can rewieght
> without fear of my new holes that I will drill running into the old holes.
>
> Michael Wathen
> University of Bob
>
>
>
">>University of Bob<<" ??   (8-O)>