[pianotech] Soundboard Analysis

[Encore Pianos]

Hi William:

 

You are correct that boards don’t crown evenly, and this is particularly
true of older boards which can often have that sine curve we have come to
know and love.  And these distortions can be great or small depending on the
board and its condition.  Yes, I have moved the gauge along the length of
the rib and do get different readings.  So if I am planning on taking more
than one reading, I make a little dot mark on the panel where I want to take
my measure again, and place the foot there the next time. 

 

I am comfortable with that limitation, because I believe that it still
allows me to take the readings that I need with enough consistency to
achieve meaningful accuracy as conditions change – such as loading and
unloading boards.  

 

By the way, Jude has made the gauge of varying lengths.  One of the
difficulties of a longer gauge is positioning it to get it in place because
it is rigid.  

 

That’s why I have been sawing off and removing all the beams.  Makes things
a hell of a lot easier.  J

 

Will

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of William Monroe
Sent: Wednesday, June 22, 2011 9:56 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Soundboard Analysis

 

Hi Will,

 

One issue I have with the Crownulator is that boards do not necessarily
(necessarily don't?) crown in a nice even radius.  Rather, they tend to be
variably crowned.  I doubt that's news to you, so I'm posing this more as a
question of whether or not you are comfortable with that limitation, and
with working around it using Jude's gauge.  I'm sure you've probably taken
readings at various placements along a particular rib  - what does that tell
you?

 

Thanks for the insight.

 

William R. Monroe

 

  

On Wed, Jun 22, 2011 at 7:17 PM, Encore Pianos <encorepianos at metrocast.net>
wrote:

Hi David:

 

I’m going to throw in my 1 ½ cents here for what it’s worth to you and
others.  I do some things a little different than you do.

 

Let me start by saying that I think there are better ways to measure crown
than the method you describe.  I used to measure by way of the string method
more or less as you do.  It’s slow, awkward, and probably not terribly
precise.  

 

About a year ago, I bought a Crownulator from Jude Reveley.  It is made up
of a 1 ‘ long steel bar accurately flattened on one side.  In its center is
a hole through which passes the moveable foot of a dial gauge.  You lay the
bar square on the panel next to the rib.  As long as there is positive
bearing, the dial gauge foot will move a distance that will be measured on
the dial.  It’s a mirror image reading, so if the gauge is reading .080 (of
a full circle of .100), this means that you have .020 of crown over that 1’
span.  There is a formula by which you can drop the numbers in and calculate
the crown for the rib.

 

I use it when putting in new boards too.  After the board is glued in and
otherwise ready to go for stringing, I take a crown reading on as many ribs
as I can get at and record those measurements.  When setting bearing, drive
the board down and take crown readings til I get my target of 50%
deflection.  Record those measures.  Then string and tune the piano, measure
crown again and see how well I guessed in the process

 

I think you would find the Crownulator significantly more accurate, quicker,
and far easier to use.  

SNIP

Will Truitt

 

 

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