This is one can of worms which, if we could digest them, would be a great discovery. Consider the geometry of the bridge, and how humidity change might cause the cap to swell or the bridge to move relative to the plate. Would a small shift of the bridge to one side effect the left string more than the right, since the strings are not perpendicular to the line of the bridge pins? The outer strings create a long trapezoid, thus a shift of position would increase the tension on one and decrease it on the other. Or would humidity change cause the center of the bridge to rise at a different rate than the edge? Ed S. ----- Original Message ----- From: Jeff Tanner To: caut at ptg.org Sent: Thursday, February 19, 2009 12:02 PM Subject: Re: [CAUT] Detuning phenomenon; was: How long to stabilize?? At USC, it was most noticeable on Baldwins. The pianos would remain right at pitch but the unisons would go out in no time in this same pattern. Since the Baldwins have Accu-Just hitch pins that aren't spaced in any predictable pattern that would support it, I sort of reasoned that threw the whole string length explanation out the window and made the phenomenon completely unexplainable. Besides, what doesn't make sense is that one side pulls sharp while the other goes flat. It would seem to be more reasonable that the change in pitch would be varying degrees of deviation in the same direction. Jeff Tanner ----- Original Message ----- From: Andrew Anderson To: College and University Technicians Sent: Thursday, February 19, 2009 11:12 AM Subject: Re: [CAUT] How long to stabilize?? Speaking from an observational point of view without carefully measuring; it seems that the opposite swing of the outside unison strings might be related to unequal string lengths between tuning and hitch pins. Seems to me that this is one of the stated reasons for single string unisons a-la Bosendorfer et al. Having a little experience with Bosendorfer, I am not certain that this holds up under scrutiny, comparatively. The opposite would then be true of uprights as well and I do note the swing in them, some more then others. Maybe someone has already investigated this and can lay these questions to rest... ? Andrew Anderson On Feb 19, 2009, at 9:43 AM, Ed Sutton wrote: In years past this has been much discussed on CAUT, and never clearly explained. Ed S. ----- Original Message ----- From: Christopher Purdy To: caut at ptg.org Sent: Thursday, February 19, 2009 10:35 AM Subject: Re: [CAUT] How long to stabilize?? I've seen this a lot but could never explain it. I thought I was going nuts. Glad to hear I'm not the only one in the nut house. Chris On Feb 19, 2009, at 10:24 AM, Fred Sturm wrote: Often one will be sharp of pitch while the other will be low, and the middle between. Christopher D. Purdy R.P.T. Registered Piano Technician School of Music, Ohio University Rm. 311, Robt. Glidden Hall Athens, OH 45701 Office (740) 593-1656 Cell (740) 590-3842 fax (740) 593-1429 http://www.ohiou.edu/music -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut_ptg.org/attachments/20090219/1b0ef749/attachment-0001.html>
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