Spreadsheet info / Jason Kanter

[Stéphane Collin]

Hi Frank.

I would be interested in knowing which inharmonicity formula you use for 
your work (for plain and for wound strings).  Among my readings on this 
topic (Roberts, Sanderson, Benade, Fletcher) there appear to be some 
differences, some motivated by discrepencies between theory and real world.
Also, in my attempts to represent an inharmonicity graph (in order to 
evaluate it's smoothness), I found it difficult to find a display scale 
(linear ? logarithmic ?) that was precise enough to reveal problems and at 
the same time vague enough to not reveal only the inaccuratie of the string 
length measurement (which in the high trebble can be proportionnally 
catastrophic).
If I may also ask if you have found a global inharmonicity level to be more 
desirable than another ?  I mean, left alone the smoothness of the curve(s) 
and the coping of the breaks, one piano has globally more inharmonicity than 
the other, and which seems better ?  And is there a formula that globally 
represents this global inharmonicity figure ?

Thanks so much for taking time.

Best regards.

Stéphane Collin.




----- Original Message ----- 
From: "Frank Emerson" <pianoguru at earthlink.net>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Monday, December 18, 2006 8:05 AM
Subject: RE: Spreadsheet info / Jason Kanter


>I have used Excel for many years to do much of my scale calculation;
> however, I alternate between my CAD software (SolidWorks) and Excel in
> working out the final details of the scale design.  Some of the work in
> Excel becomes a "design table" which interactively defines dimensions in
> SolidWorks, and some of the work in SolidWorks determines some basic
> parameters for the Excel spreadsheet.  If you are serious about scale
> design, it is my opinion that you must get into CAD software as well as
> spreadsheet software, and SolidWorks is the best IMO.  My spreadsheet is 
> an
> ever-evolving thing.  Each time I begin a new project, I tweak the
> spreadsheet to factor in things that I have learned from the previous
> project.
>
> One thing I failed to mention in my earlier post is that I avoid allowing 
> a
> section break to coincide with a wire gage change.  This only exacerbates
> the bridge dog-leg problem.  I would move the section break, before I 
> would
> allow the wire gage change to occur at the break.  In a
> rebuilding-rescaling situation, one cannot change the section break, but
> you can avoid wire gage changes at the break, even if it compromises the
> tension smoothness curve.
>
> You are correct, I do calculate the lengths first, then the diameters, to
> satisfy "target tension" parameters.  At this level, I calculate these
> values for the unison.  I would prefer this to be the same for all strings
> within the unison, but the requirements of the manufacturer may limit my
> "preferences."
>
> Someone posted a comment about equal-tension scale design.  I believe that
> I was the first to design such a scale.  The Baldwin 248 upright is an
> equal-tension scale, as well as the Wurlitzer grand, G550.  You can look
> down the treble bridge and see the wire gage changes, which coincide with
> irregularities in the string length increments.  I am still fond of this
> design concept, although my current projects do not include this
> recalculation of string lengths.
>
> Regarding inharmonicity, my spreadsheet calculates the inharmonicity of 
> the
> first six partials, and the longitudinal mode partial.  I used these
> calculations to mathematically "tune" the piano before it is built, the
> same as I would have tuned it after building it.   My intent was to save
> the "stretch factor" in a computer chip installed in the piano, which 
> could
> be accessed by any ETD.  The manufacturers I have worked for have not been
> interested in pursuing this, so it has fallen by the wayside.
>
> Regarding the Z factor, my spreadsheet calculates this, and it is plotted
> in a graph.  It is taken into consideration only to the extent that
> irregularities are evidenced in the graph.
>
> Frank Emerson
> pianoguru at earthlink.net
>