[pianotech] Pitch Change

[David Ilvedson]

Did it hit the neighbor's house?

David Ilvedson, RPT
Pacifica, CA  94044

----- Original message ----------------------------------------
From: "George F Emerson" <pianoguru at cox.net>
To: pianotech at ptg.org
Received: 4/5/2010 7:01:55 AM
Subject: Re: [pianotech] Pitch Change


>Any pressure brought to bear on a tensioned string increases the tension, whether 
>it be the bridge rising, pressure bar screws tightened, or indirectly, by altering a 
>nose bolt setting.  The reverse of any of these, relieving pressure on the string, 
>would decrease the string's tension.  The effects of any of these conditions would 
>just as surely change the tension, as turning the tuning pin.  The error of RicB's 
>calculation is that it focuses on the deflection of the string and the downbearing on 
>the bridge, which is only a small vector component of the string's tension.  In his 
>conclusions, he says something about the string tension remaining the same, 
>theoretically.  That's the problem: the string tension does not remain the same, 
>theoretically or otherwise.  It is not clear to me how he arrived at a difference in 
>frequency of only 0.1 Hertz by adding 1mm of bridge rise, but it is clear to me that 
>this cannot possible be accurate.  I'm not sure how you might mathematically 
>calculate the change in tension from 1mm rise in the soundboard/bridge assembly, 
>but it is clearly wrong to assume that there is no change in tension.




>I had an Uncle who was never "quite right" after returning home from the War.  He 
>was a brilliant mathematician, and could produce reams of paper with flawless 
>calculations, concluding that a meteorite was destined to crash into his house at a 
>specific time and date.  Not to associate Ric with my crazy uncle, but the math can 
>be perfect; it just take a faulty assumption to make the conclusion total wrong.  (The 
>meteorite never struck my uncle's house).

> 

>Frank Emerson

>  ----- Original Message ----- 
>  From: Gerald Groot 
>  To: pianotech at ptg.org 
>  Sent: Monday, April 05, 2010 7:49 AM
>  Subject: Re: [pianotech] Pitch Change (was: Grey market pianos,seasoned pianos, 
>etc.)


>  Would lowering tension say, 1/8 turn on each pressure bar screw on verticals also 
>be considered doing a simliar test as you mentioned below for comparison?  Doing 
>this would produce a very substantial drop in pitch with a very slight change in the 
>height of the screw and pressure bar in relation to where it was originally at.   Or, 
>am I making a different type of comparison?  

>   

>  Jer

>   

>  From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf 
>Of David Love
>  Sent: Monday, April 05, 2010 12:56 AM
>  To: pianotech at ptg.org
>  Subject: Re: [pianotech] Pitch Change (was: Grey market pianos, seasoned pianos, 
>etc.)

>   

>  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