Since David Roberts' book, The Calculating Technician, was published some years ago, I have programmed his formulae into a spreadsheet and plugged in the appropriate data from each piano I rebuild. The data from the various functions he developed (Loudness Factor, Hammer/String Contact Time, Inharmonicity of the 4th Partial, Tension and Percentage of Breaking Tension) creates some impressive graphs of each function, but I haven't yet learned how to manipulate this data to optimize the scale on a given piano. I understand that others use Dr. Sanderson's formulae for scale analysis and some feel that they are more accurate, at least as far as calculation of tension and breaking percentage go. Although I have been told that the scaling software that is currently available is suitable (at least for those of you with Windows based PCs), I would like to take the discussion of Do-It-Yourself scale analysis to the next level. Would those of you who have modelled their own spreadsheets with either Roberts' or Sanderson's formulae care to comment on your procedures? Which functions take precedence? Smooth tension curve? Smooth inharmonicity curve? How do you actually manipulate the data? Do you identify problem areas on the graphs and just empirically change wire diameters to see if there is any improvement? There is a fascinating article in the June 1988 Journal on 'Rescaling the 1905 Steinway Upright' which involves replacing the lowest 2 tenor trichord plain wire unisons with copper-wound bichord unisons. The article mentions the Sanderson formulae and gives the reasons for recaling but doesn't actually get into the procedure. Suggestions? Experiences? Best regards, Stan Kroeker Registered Piano Technician Kroeker & Sons Piano Experts 59 Quiring Winnipeg, Manitoba Canada R2G 1Y5 Ph. 204-669-5881
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