It's not perfect, but if you pull the plate down and the bearing changes you've effectively raised the level of the bridge relative to the termination points at the plate. Any change in the tension at all changes the stresses on the plate. It's more an experiment to show that small changes in the plate height which can be translated as soundboard/bridge rise and fall will make fairly substantial changes in the pitch. I don't remember Ric B's analysis but what was he talking about in terms of pitch change? To me a change of 10 cents is substantial and it doesn't seem to take much more than a fractional change at the nose bolts to produce that. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ryan Sowers Sent: Sunday, April 04, 2010 9:25 PM To: pianotech at ptg.org Subject: Re: [pianotech] Pitch Change (was: Grey market pianos, seasoned pianos, etc.) But doesn't changing the nose bolts also change the stresses on the plate? Any pitch change could be caused more by that then by the string height relative to the bridges. On Sun, Apr 4, 2010 at 12:25 PM, David Love <davidlovepianos at comcast.net> wrote: It's not hard to do a simple test of bridge height change and accompanying change in pitch using the nose bolts of a given piano that has them. By lowering the plate a measured amount you can effectively calculate a change in the in the bridge height (using bearing measurements as well) and then measure the change in pitch. It's not a perfect test but it can give some idea. While I can't comment on Ric B's calculations not having done them I can say that even modest changes to the nose bolts create quite a difference in pitch when compared to the normal seasonal change we experience. I'm not convinced that the soundboard/bridge rise and fall isn't a significant part of the pitch change even if it is not the entire story. Certainly compression soundboards change enough during seasonal swings as to impact the tone, that they should impact the pitch would not be unexpected. For purposes of client communications and simplicity I think it's not an unreasonable offering. David Love www.davidlovepianos.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100404/cce31a4e/attachment.htm>
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