[CAUT] Humidity, Bridge caps, pitch drift

[Andrew Anderson]

Stringcovers do help a lot but even then there can be significant  
shift, just not nearly as significant as without.

Andrew Anderson

On Jun 29, 2009, at 9:36 PM, Ed Sutton wrote:

> I wish that someone would make a direct measurement of the supposed  
> rise of the soundboard, and of the supposed bridge roll.
> I also wish there was a way to stabilize the soundboard so we could  
> find out if humidity causes a swelling of the bridge cap sufficient  
> to explain the pitch change. Or perhaps build a piano with a  
> plexglas soundboard and wooden bridge, and another with a wood  
> soundboard and a solid plastic bridge.
>
> For example, I am dealing with a piano with a full, enclosed climate  
> control system underneath, and it continues to have fast responses  
> to ambient humidity changes.  I'm wishing I could install tiny  
> heater bars all along the bridges to see what happens.
>
> And I realize that anything we prove about one piano may have no  
> relation to another piano.
>
> Ed S.
> ----- Original Message -----
> From: Shelley
> To: Ed Sutton , caut at ptg.org
> Sent: Monday, June 29, 2009 10:11 PM
> Subject: Re: [CAUT] Humidity, Bridge caps, pitch drift
>
> Hi Ed,
>
> When I worked in Seattle with Darrell Fandrich, if I recall  
> correctly, he opined that there is some amount of bridge roll due to  
> the rise of the soundboard, some models being more likely to have  
> the effect that you’ve described.  I see it all of the time here in  
> the summer especially on less expensive pianos.  But, somewhat of a  
> difference in the left strings even in the best pianos if they are  
> in the rather wet conditions naturally occurring in the summers.
>
> One can picture in our minds eye that the soundboard has no where  
> else to go, being held solid on all of its outer diameter, so it  
> will variably rise, and the plate struts seem to have more flex.  
> (yes/no?)  Either Darrell or Del would give the best explanation, I  
> believe.
>
> See you in Grand Rapids!
>
> Shelley
>
>
>
>
> On 6/26/09 7:43 PM, "Ed  Sutton" <ed440 at mindspring.com> wrote:
>
> Here's the pattern I saw on a 5'2' grand piano:
>
> On the long bridge, in each section, the leftward bridge notches  
> terminate the speaking length in the middle of the bridge. As the  
> scale ascends, the notches progress toward the front of the bridge.  
> Crossing the gap at the plate strut, the notches start again at the  
> middle of the bridge, and step forward again to the front edge. At  
> the next strut, the same thing happens.
>
> The piano was humidity struck. At the leftward end of each section,  
> where the strings terminate at the center of the bridge, pitch was  
> 10-15 cents sharp. As the scale progressed toward the front of the  
> bridge, the pitch drift became less, and was almost at pitch as the  
> notches came close to the front edge.
>
> This pattern was repeated in each section.
>
> Why?
>
> Ed S
>
>
>
>

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