Action Geometry Features
Above key is an actual illustration from the Action Geometry Program.
Overview
The piano technician makes six measurements on an existing grand piano --- two on the key, two on the whippen, and two on the hammer shank. These measurements, whether taken in millimeters or English units, are plugged into the program boxes after which calculation buttons are clicked. Immediately, data is supplied such as key ratio, whippen ratio, shank ratio, distance leverage and force leverage. In addition, a calculated hammer weight is given based on a specified downweight, e.g., 50 grams. The impact on dip and blow distances are also calculated in a special screen called "What If ... "
Basically, the program will tell you that a specified downweight at the end of the key will balance a hammer of such weight as calculated by the program. If the calculated hammer weight is, say, 6.5 grams, then the action has a poor force leverage. Making "what if .." changes to the various lever arms (moving the knuckle, for example) will yield new data for the technician to consider.
View a page from the Action Geometry Help File. Note -- when the File Download box appears you may choose to download the file to your system and unzip it, or open and view the file from a temporary internet server location. Either way the file requires unzipping.
Program Features
1) Intro and Overview
1) levers, 2) friction, 3) equalize mass/friction
2) Terms and Definitions (and the Simple Method of measure)
Learn about the three methods of measuring action
lever arms. This section alone
is guaranteed to clear up much typical confusion.
Terms and relationships are defined here.
Colorful drawings add interest and understanding to text.
3) Action Drawings (and the Conjugate Arms Method of measure)
The Conjugate Relationship or Law of Convergence.
Action spread.
Colorful action drawings.
4) Action Drawings (and the Theoretical Arms Method of measure)
This method of measure is not concerned with the
conjugate relationship of any of the components, and simply
measures off the relative Effort Arms (Ea) and Resistance Arms
(Ra) according to the drawing.
5) The Main Form
It is here where actual measured action values are
entered and saved with a file name. Begin by entering the Key
values, the Whippen values, and the Shank values. These
dimensions are taken directly from the piano action. As a visual
aid, related pictures will appear at the bottom of the screen as
you click in the various entry boxes.
6) The "What If" Form
This form is a powerful worksheet in which changes
can be made to various key action parameters. Note that there are
two colors in the Key, Whip and Shank (Ea) and (Ra) boxes -- blue
and red. Blue denotes that changes to these parameters can be
made by the technician, while red denotes that changes made are
ill advised, or require a new keyboard, or are virtually
impossible (moving the jack center pin location, for example).
Program calculates Impact on Aftertouch, Changing
Knuckle Location, and much more
7) Impact on Dip, Hammer Blow RE Aftertouch
Increasing the force leverage decreases the distance
leverage. Thus, the dip and/or the hammer blow distance will
require modification in order to achieve correct aftertouch.
Typically, the dip will have to be increased, or the blow
distance reduced, or a "split-the-difference"
combination employed whereby the dip is increased a bit, while
the blow is reduced a bit. The What If form calculates all
of this.
8) The Dip Worksheet
A simple but effective little worksheet, the Dip
Worksheet yields some interesting data. Like the Hammer
Weight worksheet, the Dip form requires an open action data
file in order to plug in some starting data fields. The dip
worksheet very nicely demonstrates the relative nature of the
distance leverage-to-dip relationship, as well as the interplay
of blow distance and let-off.
9) The Hammer Weight Form
This small worksheet quickly tells you how changes
in the weight of the hammer head affect the downweight for a
given force leverage. Simply enter the hammer weight in the box
and click the Calc Downweight button. The worksheet opens with
pre-loaded values taken from any open file.
10) The Comparisons Form
Action data files can be set up side by side in
order to quickly compare parameters. After opening the
Comparisons form, go to File List | Open Lists and
a list box will open displaying all your saved files. Double
click selected files to display in the columns. Certain critical
leverage and other data are highlighted in blue for quick
viewing.
11) Analyzing a Working Action
Print out this page for use as a checklist in
anaylizing actions.
