Even so called "equal tension" scales are not really equal tension as there are variations within each gauge section. I would imagine there are a confluence of factors: case, soundboard, bridge, plate expansion and contraction, friction, scale tension/break point variability. Interestingly, even 100 years ago in the discussions of the major manufacturers of the day catalogued in "Piano Tone Building" edited by Del Fandrich, there is reference to string tension as a factor in tuning stability. Let me know when you figure it out though. As Bill Ballard is fond of quoting: "I gotta go to woik". David Love davidlovepianos at comcast.net www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of RicB Sent: Sunday, March 11, 2007 4:19 AM To: pianotech at ptg.org Subject: Seasonal pitch change: As I have shown, this lower tension thing... which is really lower % of breaking strength (which in itself turns out to be a rather dubious term in practice) doesnt really account for the large differences / uneveness in pitch change through out the scale. Tho no doubt it plays what can be called a significant roll. I'm working on a combination of a basic scaling spreadsheet and the deflection / tension changes spreadsheet along with this last bit about pin angles and strings climbing them (which I am glad to see finnally acknowledged) to show the isolated effect of such changes on real scales. I think one will see a suprising picture develop, and one that very much deviates from what we observe. Which means that other quite significant forces (for not to say dominant) are at work, which to some degree must counter act and to some degree work in concert these weve been discussing. I dont know of any data at all that supports the claim that scales designed with more equal tension through the piano will tend to go out of tune more evenly. Is this casual observation based or can you point me to some specific study ? Cheers RicB The lower the tension in a given string the greater the change in pitch for a given change in length. Since the lowest tension tends to be in the low tenor, that is where the largest change in pitch generally is. The bass section is usually the highest string tension and therefore changes the least. On many pianos the scale tensions also drop in the upper treble. Scales that are designed with more equal tension through the piano will tend to go out of tune more evenly. David Love davidlovepianos at comcast.net www.davidlovepianos.com
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