[pianotech] Action Ratios Recap

[Nick Gravagne]

Dear JD,

First let me say that I have read and benefitted from many of your fine
posts as well as the technical articles found at your web site
http://pianomaker.co.uk/technical/. You are clearly an intelligent and
most dedicated practitioner. We have all learned something from you, and
hope to continue to do so.

Now I have noticed that you don't mince words:

A recent sampling from your pen:

"... Pfeiffer's approximations as the scribblings of an amateur."

"... woolly approximations..."

"... Pfeiffer's laborious pseudo-proof..."

And my favorite:

"The class handout... misleadingly entitled 'Action Geometry: Truth and
Consequences', has no truth in it at all and the consequence will be
that any reliance on it will lead to wrong results."

Your ironic use of the words "truth" and "consequences" conveys an
almost Shakespearean ambiance.

To wit: "Methinks, Horatio, when truth be false, the consequence worse!
Whence ratio, Horatio, to me 'tis but lever; to others still I am found
but too clever."

Perhaps the reason that "nobody has even commented on" your Jan 10th
post is because, as I see it, it is not complete, except for the
rationale and mathematics of capstan rise to that of key dip. This,
then, is followed by a broad and generalized argument in favor of
trigonometry as the only path to success; not to mention a mind-numbing
use of numbers carried out to eleven decimal places. 

Your palpable criticism of Pfeiffer's work and, presumably, any modern
technician's work who borrows from him has, I am guessing, not gone
unnoticed.

You are entitled, don't get me wrong. I have not ignored your post, but
there is much to consider. Your argument that the most exacting ratio of
key dip to hammer rise, as these relate to x and y positions of
components gliding along arcs, is, of course, completely valid. What
remains to be seen is what we gain from such exactitude.

I have long thought that we yet lack a consistent and unified approach
to the subject. I recently evaluated a Young Chang action by physically
measuring the lever arms using three different methods, resulting in
three different ARs of 5.9, 5.7 and 4.6. The AR that mostly agrees to
the actual measurement (a bit tricky to do) of dip and subsequent hammer
rise is the 5.7 AR.  

The Levers and Ratios approach as used by much of the technical
community, and as has been covered by me and many others on this list,
has been roundly rejected by you. I am intrigued that you do so. I know
that well-known names, whether pianos or technicians, do not impress you
as your only motive is to get to "the truth" and let all trumpet blasts
be damned.

Very well, then, let's get to the truth.

I will follow up soon with some ideas on how we might handle this issue
with a degree of organization, clarity, consistency and professionalism.
Handled as such, we all might learn something.

BTW, the subject heading "Action Ratios ..." may have run its course.

Respectfully,


Nick Gravagne, RPT
Piano Technicians Guild
Member Society Manufacturing Engineers
Voice Mail 928-476-4143