<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=iso-8859-1"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style></style></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1>Hi David: <o:p></o:p><o:p> </o:p>If you reread my post you will see that all the readings are taken with the board glued in and at the various stages of the process working up to and including stringing, tuning, and loading the board. I can throw the gauge on the panel when it is ribbed and out to be worked on, but I don’t think that is of as much value as the in piano readings.<o:p></o:p><o:p> </o:p>I do use it to analyze boards prior to teardown. Certainly when I am doing an estimate I take it with me and can take readings on every rib I can get to, along with bearing readings on the topside. And once the piano is in the shop, do all this as part of the teardown process, particularly if I am going to be using the old board again. <o:p></o:p><o:p> </o:p>You are correct that in some places the access will be more difficult or impossible, particularly in the high treble where things get much more crowded. The beams can be in the way in other places. Sometimes I shift the location to one side or the other to avoid the beam, but generally try to center it under the treble bridge. You may have better access with your string in the problem areas. Otherwise, it is no more difficult than laying on the floor, reaching up with gauge in hand and setting it next to the rib, and taking a reading with sufficient light. That takes only a few seconds to do. In those places it is easier and faster.<o:p></o:p><o:p> </o:p>As I said earlier, it will not measure negative crown, but neither does the string. A straight edge won’t give you a measure, but will tell you that it is negative.<o:p></o:p><o:p> </o:p>Will<o:p></o:p><o:p> </o:p><o:p> </o:p> <o:p></o:p><o:p> </o:p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of David Love Sent: Wednesday, June 22, 2011 9:24 PM To: pianotech@ptg.org Subject: Re: [pianotech] Soundboard Analysis<o:p></o:p></div></div><o:p> </o:p>Sounds like a nice gauge but I’m trying to envision using it effectively with the board still in the piano which is what this was and the analysis was to outline a method of assessing boards before they come out not after they’re out.  With a new board there are certainly more accurate ways to measure crown along a rib but with the board in the piano this doesn’t seem like it’s any easier, maybe harder given the access problems in some areas.<o:p></o:p><o:p> </o:p>What I was getting at with the reason for the lack of change in crown does have something to do with the difficulty in measuring with the string however.  This board clearly started out with negative crown through that area.  Hard to measure that with a string.  Even with some rise in the board as indicated by the bearing change and the change at the struts it was not enough to push the board into positive crown.  The board has oilcanned and is toast.  <o:p></o:p><o:p> </o:p>My question about restoring crown was rhetorical.  I agree that it is useless as a method for restoring crown, though it is often cited as the reason to do it.  Even though this board had been heavily shimmed there was certainly no evidence of crown and, in fact, in many areas the crown was negative.  <o:p></o:p><o:p> </o:p><div>David Love<o:p></o:p><a href="http://www.davidlovepianos.com">www.davidlovepianos.com</a><o:p></o:p></div><o:p> </o:p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Encore Pianos Sent: Wednesday, June 22, 2011 5:17 PM To: pianotech@ptg.org Subject: Re: [pianotech] Soundboard Analysis<o:p></o:p></div></div><o:p> </o:p>Hi David:<o:p></o:p><o:p> </o:p>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.<o:p></o:p><o:p> </o:p>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.  <o:p></o:p><o:p> </o:p>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.<o:p></o:p><o:p> </o:p>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<o:p></o:p><o:p> </o:p>I think you would find the Crownulator significantly more accurate, quicker, and far easier to use.  <o:p></o:p><o:p> </o:p>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.  <o:p></o:p><o:p> </o:p>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.  <o:p></o:p>I can combine that with my Wixey readings.<o:p></o:p><o:p> </o:p>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?  <o:p></o:p><o:p> </o:p>Will Truitt<o:p></o:p><o:p> </o:p>I hope this gets through.  Too many of my posts disappear into the ether in this new but not improved system we have.<o:p></o:p><o:p> </o:p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of David Love Sent: Wednesday, June 22, 2011 12:12 PM To: pianotech@ptg.org Subject: [pianotech] Soundboard Analysis<o:p></o:p></div></div><o:p> </o:p>You might need html to view this.<o:p></o:p><o:p> </o:p>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.  <o:p></o:p><o:p> </o:p>I won’t tell you what my conclusion was about this soundboard but you might be able to guess.  (Steinway AIII)<o:p></o:p><o:p> </o:p>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).  <o:p></o:p><o:p> </o:p>BTW this board had received a lot of shimming perhaps with the idea of restoring crown???  What do you think?<o:p></o:p><o:p> </o:p><o:p> </o:p><o:p> </o:p><o:p> </o:p><o:p> </o:p><o:p> </o:p><o:p> </o:p>Rib#                       Crown                              DB w-ten/wo            Rib L    H        W  (mm)<o:p></o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>Or section           w-ten/ wo-ten<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>1                              2/2                                         .006/.015                             600         17           28<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>2                              2/2                                         .006/.015                             790         20           27<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>3                              2/2                                         .009/.012                             940         20           27<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>4                              1.5/2.5                                  -.006/.003                            1040       20           27<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>5                              0/.5                                        -.003/.003                            1080       22           27<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>6                              0/0                                         -.009/.006                            1120       21           27<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>7                              0/0                                         .006/.018                             940         21           26<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>8                              0/0                                         .006/.021                             660         20           25<o:p></o:p></div>                                                                <o:p></o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>9                              0/0                                         .006/.027                             560         20           18           <o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>10                           0/0                                         .018/.042                             390         18           23<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>11                           0/0                                         .022/.045                             340         17           23<o:p></o:p></div><o:p> </o:p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in'>12                           0/0                                         .025/.050                             270         16           23<o:p></o:p></div><o:p> </o:p><o:p> </o:p>David Love<o:p></o:p><a href="http://www.davidlovepianos.com">www.davidlovepianos.com</a><o:p></o:p><o:p> </o:p><o:p> </o:p></div></body></html>