Touchweight Key Ratio Question

[Richard Brekne]

Bill Ballard wrote:
> 
> 
> 
> It's similar to RicB's question about where the driven lever arm of
> the hammershank should be located: down the shank's center line,
> elevated to such a degree as to pass through the hammer heard's
> center of gravity, or at the hammer's strike point. The payload is
> the hammer's strike point, that's where linear measurements should be
> taken.
> 

The only problem here Bill, is that it doesn't work out right. I have
done this time and time again and every time I do it the results are the
same. Alan Vincent's formula coincides with Stanwood's very closely, and
the method you refer to does not, and in fact causes an obvious
difference between the resulting bass and treble ratio number that does
not correspond to a real difference in ratio otherwise. This lack of a
real difference can be confirmed by both the Stanwood measurement, and
an actual measurement of the distance the hammer moves for any given key
movement.

This leads me to deem that Vincent's method is the correct one. The
ratio is not about payloads. Its about how much movement happens at one
end of the system for a given amount of movement at the other, or how
much weight, or how much speed. 

I think, the problem with the method you point out is that the hammer
isn't lifting anything, at least until it hits the string. Therefore the
ratio taken thus corresponds to no real lever. By contrast... the hammer
is the thing being lifted, and the lever lifting it is the shank with
the knuckle at the fulcrum.

In any case, the method Vincent gives yields the same results that
Stanwood's formula gives. Any differences between the two have to do
with inaccuracies in the measuring process.


-- 
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html