The New Touchweight Metrology

[stanwood]

To you all:

I decided to unveil my full touchweight formula in the
second period of my touchweight analysis lab at
Albuquerque.  Feel free to spread the word.

I'm very grateful for the enrichment this list
conversation has given me.  I want you all to see it first.

Sent to pianotech E-mail list  7/16/95

The New Touchweight Metrology

by David C. Stanwood


The New Touch Weight Metrology is a new system of units
and measures which defines, in simple terms, the amount of
weight, leverage, and friction that each action component
contributes to the touch of the key.  It expands upon the
upweight and downweight measures of the old touchweight
metrology.


                  SHORT FORM EQUATION:


Where, at the touchweight measuring point of the key:

Upward static force  =  Downward static force

Is described as:

(StrikeWtxStrikeRatio)+(RepWtxKeyRatio) = FrontWt+BW



Where:

StrikeWt(Strike weight) = The radius weight of the hammer
and shank, pivoted at the hammer flange, taken at Strike
Line Radius.

Strike Ratio = The ratio of the Strike Weight to its
corresponding upward force at the front of the key.

RepWt(Repetition weight) = The radius weight of the
repetition, pivoted at the repetition flange, taken at the
capstan contact point.

Key Ratio = The ratio of downwards force at the capstan to
the corresponding upward force at the front of the key.

Front Weight = The radius weight of the keystick, pivoted
on the balance rail, taken at the front of the key.

BW = balance weight as (UpWt+DownWt)/2


Note: The Short Form notation may be expanded to fully
describe all frictional components, as well as the weight
and friction components of the damper action.

Dynamic Touch Analysis

Dynamic touch is the actual amount of force required to
maintain key movement when playing the piano.  It takes on
the order of 50 grams of force to move the key when
measuring downweight.  However, the amount of force needed
to move the key during pianissimo playing is on the order
of hundreds of grams and in fortissimo paying, it's on the
order of thousands of grams.

The precise amount of force required to move the keys at
playing speed requires expensive techniques and
procedures.

The beauty of the New Touch Weight Metrology is that it
allows for simple and practical measurement of weight and
leverage factors that are proportional to dynamic touch
weight, thereby allowing for assessment and control of
dynamic touch without prohibitively expensive and complex
techniques.

Studies show that pianos with similar strike weight,
strike ratio, front weight, and balance weight
characteristics will have similar playing
characteristics.

The New Touch Weight Metrology opens the door to valid
categorization and standardization of piano actions.

David C. Stanwood

All copyrights reserved July 1995

This posting may not be reproduced in any form without the
permission of David C. Stanwood

If you wish to forward this posting to another party by
E-mail, forwardings may be sent to stanwood@tiac.net who
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party to whom you wish to forward to.


P.S. -  I won't have time for much conversation until after Albuquerque.

Signing off