[pianotech] Soundboard Analysis

[Encore Pianos]

I think I paid about $60 or $80 for it a bit over a year ago.  Check with
Jude on his current pricing and availability

 

Will

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Joe Goss
Sent: Wednesday, June 22, 2011 9:03 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Soundboard Analysis

 

Hi Will,

Your message came through here on the old list.

I have not as yet changed to the new format.

Sort of refreshing to not have over 100 posts to read every day >g<

 What was the cost of the Reveley gauge?

I am dealing with a 1931 S&S 'B' That has a 5 second sustain on C4

Nice crown above the C5 but flat as a pancake in the tenor.

As measured with my string level, so not very precise.

Local Boise dealer thinks that it is a voicing issue.

New Hammers and wips (not S&S) so I am a little leery of their advice.

Wish we had a good second opinion near us.

 

 

 

Joe Goss BSMusEd MMusEd RPT
imatunr at srvinet.com
www.mothergoosetools.com

----- Original Message ----- 

From: Encore Pianos <mailto:encorepianos at metrocast.net>  

To: pianotech at ptg.org 

Sent: Wednesday, June 22, 2011 6:17 PM

Subject: Re: [pianotech] Soundboard Analysis

 

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.  

 

I am going to speculate that the reason the measured crown does not change
when there is a positive change in bearing is that the method of measuring
crown is insufficiently precise, it is too easy to deflect the string and
the gauge is too crude to reflect what may be happening.   By way of
contrast, the bar of the crownulator is rigid, and the dial is sensitive
enough to reflect small changes in your hand pressure on the tool and any
accidental roll you might introduce in your awkward state on the floor.  

 

I have a Wixey gauge and use that, but I have for 30 years or more used a
Fowler dial gauge that I bought from APSCO way back when.  I would take 13
downbearing readings  along the bridges, let the tension off the strings and
remove them except for my samples and measure again.  Plenty of boards out
there where the bearing did not change at all from loaded to unloaded, and
usually little or no crown down below.  More movement at the ends, although
the pattern of the readings would vary from piano to piano.  It doesn’t tell
you everything about downbearing, but if you use it consistently it can tell
you a lot quickly and precisely.  

I can combine that with my Wixey readings.

 

Shim to restore crown?  I doubt it does anything meaningful.  Has anyone who
advocates this as a rebuilding method taken precise before and after
measurements, and followed that up a few months later with more
measurements?  

 

Will Truitt

 

I hope this gets through.  Too many of my posts disappear into the ether in
this new but not improved system we have.

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Love
Sent: Wednesday, June 22, 2011 12:12 PM
To: pianotech at ptg.org
Subject: [pianotech] Soundboard Analysis

 

You might need html to view this.

 

Below is a chart that I use for soundboard analysis.  Measurements are taken
before and after taking the tension down.  Crown sections are measured
between the ribs using a string stretched as far as possible and a wedge
gauge (very low tech).  I try and correspond the measurement of the crown
with the downbearing measurements in terms of location.  An analysis of the
soundboard rib design can also be made using the rib dimensions—I haven’t
done that yet.  Downbearing measurements are Lowell gauge readings.  Note
that .0175 corresponds to about 1 degree.  

 

I won’t tell you what my conclusion was about this soundboard but you might
be able to guess.  (Steinway AIII)

 

Question to ponder:  Why would it be that although there is a positive
change in downbearing when the tension comes off there is no apparent change
in measured crown?  Also note (not included in the data below) that when
measuring the change in distance from the struts to the bridge in the upper
end of the piano (from about rib #6 to the top) the average change was about
1 mm (the board rose about 1 mm).  

 

BTW this board had received a lot of shimming perhaps with the idea of
restoring crown???  What do you think?

 

 

 

 

 

 

 

Rib#                       Crown                              DB w-ten/wo
Rib L    H        W  (mm)

Or section           w-ten/ wo-ten

 

1                              2/2
.006/.015                             600         17           28

 

2                              2/2
.006/.015                             790         20           27

 

3                              2/2
.009/.012                             940         20           27

 

4                              1.5/2.5
-.006/.003                            1040       20           27

 

5                              0/.5
-.003/.003                            1080       22           27

 

6                              0/0
-.009/.006                            1120       21           27

 

7                              0/0
.006/.018                             940         21           26

 

8                              0/0
.006/.021                             660         20           25

                                                                

9                              0/0
.006/.027                             560         20           18           

 

10                           0/0
.018/.042                             390         18           23

 

11                           0/0
.022/.045                             340         17           23

 

12                           0/0
.025/.050                             270         16           23

 

 

David Love

www.davidlovepianos.com

 

 

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