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
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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