The Ratio

[Richard Brekne]

Hi folks

Was dinking around with an action today and was looking at different
combinations of this and that and noticed what seems to be a problem
with the way that Ron Overs figures the action ratio. The problem really
centers around how he measure the hammer ratio. He does that much like
the key ratio is measured (distancewise) by takeing a line from the
flange center to the top center of the knuckle , and from the flange
center to the top center of the hammer. Alan Vincent, and others give
flange center to hammer center line, and flange center to knuckle center
line (both straight lines down the shank).

First off... if you take Overs method, you end up with a different ratio
for the bass and treble due to the differing bore distances... but what
I ran into today was the following.

I was checking the ratio on a sweedish grand to analyse the thing and
the following measurements came through.

Key ratio is 0.5 no matter how you measure it.
Whippen ratio was 1.55, and the Stanwood quantity (WRW) was 19,4.
Hammer ratio taken the Overs way was 139 / 22 or 6.32
Hammer ratio taken the Vincet way was 128 / 17 or 7,53

A considerable difference to be sure. 

The resulting overall ratios then were

Overs 	0.5 * 1.55 * 6.32 = 4.9
Vincent	0.5 * 1.55 * 7.53 = 5.84
Stanwood formular yeilded   5.8	

Stanwood was figured 6 sample keys, and the average was taken.

So..... what am I missing here ? Something seems wrong with the Overs
formula or what ?

Cheers !

RicB

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