Humidity Change and Unisons

[Don]

Hi Ron,

So your *take* is that the bridge is rolling to some extent? And that the
uneven tail lengths cause the smearing of the unisons?

At 07:00 AM 08/21/2000 -0500, you wrote:
>>Hi  Ron,
>>
>>So it *is* the red felt in the casters after all? LOL
>>
>>Seriously I would love to see the sort of research you suggest. But lets
>>agree that the plate moves with humidity change. And further that most
>>pitch correction is plate related more than sound board related. 
>
>Hi Don,
>No, let's not. The movement of the soundboard and bridge relative to the
>plate is the major culprit. As far as I know, cast iron doesn't measurably
>change dimension with humidity swings, only temperature. Wood does. I'm
>going with the observable. Incidentally, that wasn't a research proposal.
>It's a logic exercise.
>
>
>
>>One *hint* again is that damppchaser bars under the soundboard do *less*
>>than bars at the belly and tail. To me that indicates that drift is plate
>>related more than soundboard related. 
>
>I haven't tried it, but if that's the case, to me that would indicate that
>different bar placement locations produce different air convection and
>dispersal patterns underneath - some more efficient than others. I don't
>get a connection with the plate at all there. Perhaps it's just a case of
>"warm tail, happy piano". Maybe it's time to re-design my business card.
><G> I kind of like it.
>
>
>
>>The smearing of the unisons is also very real and can be measured. Simple
>>sound board movement I don't believe could be responsible for this type of
>>drift.
>
>I didn't say it wasn't real. I just attempted an explanation as to how it
>got to where you found it. The soundboard movement is relatively simple,
>it's all the friction and tension interactions along the string length that
>get complicated, and the only data we have there is pitch measurement in
>the speaking lengths.
>
>
>
>>Then too, apparently (I have not noted this but will accept that others
>>have measured it carefully) pianos with aliquotes or *double scaling*
>>appear to be more stable. If this is true then the hitch pin / string angel
>>is where atleast some of the unison smear is happening. 
>>
>>These are just hints nothing more.
>
>This may very well be real too, but I doubt it's the aliquots that make the
>difference. I'd think it's the longer total backscale length. 
>
>Most of the mysteries we see can be explained by what we already know.
>Determining what we already know seems to be the hard part.
>
>Ron N
>
>
Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.

Tuner for the Saskatchewan Centre of the Arts

drose@dlcwest.com
http://donrose.htmlplanet.com/

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REGINA, SK
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