Aha! was flat facts

[Alan]

Well, as King Agrippa said: "Almost, thou persuadest me ... "

And, yes, it was just my suppostition. But something has to explain the
source of change in old pianos that have had all the time necessary for the
soundboard to collapse, strings to stretch, etc., as much as they possibly
could. But still fall flatter if left alone for long stretches.

Somebody with a physics background might be able to define the static and
dynamic forces involved here, say 125 to 175 lbs. of tension on a rope
(sting) attached to a pulley (pin) with a counter-torque friction of 35-200
in. lbs., etc.

Happy Easter/Passover/Whatever/Birthday/Nothing (pick one) to all!

Alan R. Barnard
Salem, MO


-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf
Of Ron Nossaman
Sent: Sunday, March 27, 2005 2:16 PM
To: Pianotech
Subject: Re: Aha! was flat facts


> And herein lies the interesting crux of my whole question from the
> beginning: We have guesses, suppositions, and opinions but, 
> apparently, really don't know why pianos get flatter and flatter and 
> flatter over time. Seems like this question is so basic that 
> experiments would have been done long ago and we'd have a definitive 
> answer. And maybe, who knows, some ideas for building more stable 
> pianos.

There have been experiments, including making pins so tight in 
waterproof pinblocks that you could barely turn the pin in with 
three hands. Guess what. The super tight waterproof block pianos 
still dropped in pitch over the long run. In my experience, tuning 
stability gets better with decent scaling, rib supported boards, and 
laminated bridge caps. Hence my answer.

> I still go with turning pins, though. There is a natural, sustained 
> tension on the pin from the string that would love to turn the thing 
> counter-clockwise. Earth tremors, children thudding across the floor, 
> sonic booms, moving the piano, and hovering ufo's would all put 
> vibration into the system, however briefly, and the pin could jiggle 
> just a a third of a skinny hair each time. But over the years ...

Is that a guess, a supposition, or an opinion? Just asking, since 
the same rules ought to apply to us all.
Ron N
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