[pianotech] Soundboard deflection - Pitch raise

[William Truitt]

To David and Master Po (or is it Lord Vader?) :-) 

Jude Reveley has manufactured and made available a device for measuring
crown in piano soundboards, called the Crownulator.  I purchased one from
Jude, with the intent to quantify the amount of crown the newly bellied
board has after gluing into the rim, and then after stringing and tuning to
pitch.  All this to quantify the actual deflection of the board as it
compares to the calculated deflection.  

I haven't really used it yet, but it is a pretty simple device composed of a
foot long bar with the foot of a dial gauge coming out of the bottom. You
simply lay it on the soundboard near a rib and take a reading.  Put the
value into an Excel spreadsheet and calculate the crown radius. The
deflection is measured in thousandths. 

For the purposes here, one could simply take several readings on the board
before beginning the pitch raise, and do the same again on completion of the
tuning.

This still doesn't answer the question of the cause of the pitch change, but
at least could give you some idea of the movement of the board related to
pitch changes.

It would be equally interesting to use this device to take crown readings at
set points summer and winter and compare.

We have had the mother of all rainy summers this year.  The pianos are going
bonkers.  I have tuned some pianos in the last couple of weeks that were
almost 40 cents sharp on middle C, and the high treble as much as 85 cents
sharp.

It's such a rainy summer that my standing joke is, "All this rain and
humidity is making me suicidal.  I was going to slash my wrists, but I
couldn't get the knife drawer open!"

Will Truitt 

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Wednesday, August 05, 2009 3:33 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Soundboard deflection - Pitch raise

David Nereson wrote:

> Right.  I'm wondering if anybody really knows anything. Couldn't you put 
> a metal bar across the top of the rim of a grand, then a vertical bar 
> hanging down from it, with a dial indicator touching the soundboard such 
> that it would track any rises and falls of the board?  Then take 
> readings every week, also noting any pitch changes, and see what's going 
> on?  I'm surprised nobody's done this yet.  Or have they?  ("They can 
> put a man on the moon, but . . . . ")

So why is everyone ready to spend days arguing about it, but 
nobody is ready to spend an hour of their time over the next 
two years gathering evidence to explain it? I did the math and 
measured a lot of bearing angles through the years, and proved 
to myself that soundboards don't rise and fall nearly enough 
to produce what we hear. So take your own measurements, do the 
math yourself, and figure out your own story. Or just believe 
what you were taught without question, as most folks do.
Ron N