[pianotech] Pitch Change (was: Grey market pianos, seasoned pianos, etc.)

[Terry Farrell]

THAR WE GO POSITIVE, SCIENTIFIC, REPEATABLE FACT/TRUTH, case closed,  
let's move on.   :-(

Terry Farrell

PS: WTF?

On Apr 3, 2010, at 7:33 PM, Gerald Groot wrote:

> I did read that William, thank you.  After reading more of it as  
> well, it appears to me that there is much more speculation than  
> positive proof either way from either Ric or John.
>
> I visited with Dr. Yat Lam Hong all afternoon today.  He is a man  
> FULL of information and is most willing to share it.  How he manages  
> to retain it all is beyond me.  I wish I had that kind of memory.   
> For those of you that do not know Yat Lam, he is an extremely  
> knowledgeable RPT.
>
> I asked Yat Lam Hong his philosophy on what he thought was the main  
> cause of why pianos go out of tune so drastically from seasonal  
> changes and his immediate reply was "humidity."  He went on to say  
> that "humidity causes swelling and contraction of the sounding board  
> sending pitch up and down.."  A pure and simple answer.   I asked  
> him about the rim being a factor.  "Possibly some, but no, not  
> much."  Adding:  "It would be a very small factor as would the  
> sounding board near the rim because it is glued down there.  The  
> bass section changes tuning and pitch also but not nearly as much as  
> the tenor section.  One reason is because it is closer to the edge  
> of the piano.  Whereas the tenor section of the pianos bridge runs  
> down the middle of the sounding board where it swells and contracts  
> the most."
>
> We both agreed that there some other factors that do come into  
> play.  Some of them have been mentioned here such as heat or  
> lighting.  We both think however, that the major contributing factor  
> is the sounding board swelling and contracting.  So, I stand firmly  
> by what I was taught.  We had other things to do so we dropped it at  
> that.
>
> Jer
>
>
> From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org]  
> On Behalf Of William Monroe
> Sent: Saturday, April 03, 2010 1:59 PM
> To: pianotech at ptg.org
> Subject: Re: [pianotech] Pitch Change (was: Grey market pianos,  
> seasoned pianos, etc.)
>
> Hi Gerald, List,
>
> Having sifted through the archives.........  ;-]
>
> OK, so my memory did serve.  Here's an excerpt from Ric Brekne's  
> posting of the math that shows resultant pitch changes due to rise &  
> fall of a soundboard.  This shows minimal effect on pitch due to  
> soundboard deflection.  Here's a link to the archives as well with  
> the thread, " Soundboard Deflection and Pitch Change / was  
> Downbearing."
>
> https://www.moypiano.com/ptg/pianotech.php/2006-August/thread.html#194422
>
> William R. Monroe
>
>
>
>
>
>
>
>
>
> Ric wrote:
>
>
>
> .............Let me illustrate..given the following, and by all  
> means check my
>
> figurings... (for the moment disregard the width of the bridge and  
> deal
>
> in simple triangle trig)
>
>
>
>
>
>
>
> - an undeflected string tension of 160 lbs.
>
> - string diameter of 0,8 mm.
>
> - front length of 50 mm.
>
> - back length of 25 mm.
>
>
>
> This yields a front length frequency of roughly 4248.88 Hz.  f =  
> SQRT((T
>
>
>
> * 398 *10^6)/(L^2d^2))
>
>
>
>
>
> If you then deflect this string 1 mm upwards you get a string  
> deflection
>
> angle of a whopping 3.46 ¤,  a downwards force of 9.59 lbs, and a
>
> frequency of 4248.98 hz. Thats only a change of 0.106 hz.... at note  
> 88
>
>
>
>
>
> or there abouts.  Even a 2 mm deflection would'nt increase the  
> frequency
>
> of the string more then 0.42 hz and that would at the same time  
> cause a
>
> string deflection angle of 6.87 ¤ !! and a downbearing force of just
>
>
>
>
>
> over 19 lbs... for just one string ! You'd be quickly over 3000 lbs of
>
> total downbearing force on the soundboard...
>
>
>
> If these figures are correct... then clearly soundboard deflection can
>
> nearly be ignored when it comes to pitch changes.
>
>
> On Sat, Apr 3, 2010 at 9:55 AM, Ron Nossaman <rnossaman at cox.net>  
> wrote:
> Gerald Groot wrote:
> I have read what has already been written in this thread,  
> currently.  Ron,
> I'm not going to sift through the archives.  The dissusion has been  
> and
> still is being presented now.  I'm merely adding to it as you are  
> giving my
> current thoughts on the matter again, as you are.
> Have YOU had the time to do all of these measurements yourself?  If  
> so, I
> don't know how you managed to find it let alone have the patience  
> for it.  I
> haven't nor do I have the desire to do so.  Taking measurements is  
> not the
> only proof available.  When does logic and common sense ever come  
> into play
> here?
>
> It comes into play immediately when you find how much a soundboard  
> has to move to produce the required tension changes. Yes, I've taken  
> a whole lot of time trying to learn how things actually work, rather  
> than assuming that what I was taught was correct. It used to be  
> common sense that horse hairs in the rain barrel turned into worms.  
> I take the time because I'm interested in learning something real.
>
> Ron N
>
>

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