I hope I am not asking a stupid question here. Why is equal tension more important than a smooth z factor? It seems intuitive to me that an even loudness factor would be more important on the hearing end than an equal tension. Thanks, Dean Dean May cell 812.239.3359 PianoRebuilders.com 812.235.5272 Terre Haute IN 47802 -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Frank Emerson Sent: Monday, December 18, 2006 2:05 AM To: Pianotech List 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
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