Pianotech

Expand all | Collapse all

A Weber Semi-Concert Grand Piano Analysis

  • 1.  A Weber Semi-Concert Grand Piano Analysis

    Posted 04-07-2016 22:10

    I have a 1904 Weber 7’4” Grand piano in the process of restoration in my shop. Below is a look at the string and rib scale relationship.

    This piano had a cracked soundboard that was flat, a short sustain, however, the tone had a nice fullness to it, which showed lots of potential.

    The string scale was basically 10 notes for one gauge and the tension curve showed that in between gauges would benefit for smoother transitions. I went with a 6 /4 pattern which worked well. Altering the scale only added another 40lbs to the downbearing.

    This piano had been rebuilt before, and the bass string scale was aweful and uneven. The lowest bass string had a 4.3 tension to length ratio 286lbs/66in.  Since the lowest tenor string was 160lbs, I scaled the bass section like this-  8 Unichords 286 – 322,8  bichords 244-276, 6 trichords 203- 230. This way each was in the 39- 50 breaking percent range.

    So next, I examined the rib scale to see if it could support the downbearing.

    The rib scale was beautifully engineered and precise. Only a little improvement could be found. Ribs 8 and 13 were the hard working ribs and needed to be a little larger to bring down the stress level to match the others. The rib profile was at 76% originally, and with a little adjustment, I was able to get it down to 73%. This will give the piano tone a little more depth. I accomplished this by raising the average stress from 1,977 to 2,007 lbf (still within acceptable range)and changing the rib profile to a little wider and not as tall.

    Here’s the specs:

    Force …………948Lbs

    Resistance….. .10.72 Sq.In.

    Board Sq.Ft  ....15

    Rib Count ……15

    Rib Profile……73%

    Rib Stress…….2,007 lbf

    Now with the assurance that the string scale is supported by the rib scale, the rebuild is off on a solid foundation.

    I particularly like this Weber design as it is well engineered, inexpensive compared to known brands, but on equal footing in my opinion

    .

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG
    ------------------------------


  • 2.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-09-2016 19:40

    Mr. Chernobieff,

    It looks to be a fine project for sure.  The numbers you include seem to come from a very specific protocol.  Would you mind explaining them to those of us who don't know how they were arrived at ? Thanks in advance.

    ------------------------------
    Karl Roeder
    Pompano Beach FL



  • 3.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-10-2016 12:54

    Hi Karl,

    Thank you for the inquiry.

     First the bass string scaling method is heavily inspired by the 3-part articles “Some Thoughts on the Design of Bass Strings” by Richard M. Brown   August 1988

    The rest is a practical system I came up with to analyze a soundboard that will pinpoint the problems it has (if any), improve its resonance, and make sure it can properly support the downbearing.  I came up with six elements- Force, Resistance, Board Square Feet, Rib Count, Rib Profile, Rib Stress.  After comparing several boards to one another a clear picture begins to form. Most boards are not engineered properly! Because of that the tone suffers. For example boards that “sound” stiff have ribs that are too large with a high Rib Profile. I’m finding boards in the 93-98% range. Boards with a low tone and plenty of resonance have a rib profile in the 70% range. A Steinway O that came in had a rib profile of 83%, with leaves much room for improvement. I have a piano in my shop with a 68% profile and it has a fantastic deep boom sound. It is a large upright with a 12 sq. ft. board that really sounded much “bigger”. And I found that it really just came down to good engineering.

    The six elements are not independent from each other, but interrelate. So if one element is changed, it has an effect on the others. As an example, a common ailment is having one rib short. This creates a situation in which all the ribs are larger than they should be, and at the same time, they are over stressed and under-engineered. Let me tell you that it is an amazing feat of engineering for that designer (Jacob Gross) to get such a low rib profile of 68%, all while maintaining the other elements in the proper proportion.

    My system evolved by asking myself two questions that kept coming up.

    Why copy soundboards with tonal problems and obvious design flaws and bad engineering?

    How did some boards achieve such a low tone resonance, and most do not?

    Now with the ability to answer those questions and make the necessary adjustments, allows me to rebuild a clients piano to exceed their expectations.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 4.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-10-2016 13:03
    I am with Karl on this one.? Your reasoning sounds good and well thought out.? However, some of us don't understand what you mean when you say, " For example boards that ?sound? stiff have ribs that are too large with a high Rib Profile. I?m finding boards in the 93-98% range. Boards with a low tone and plenty of resonance have a rib profile in the 70% range."? And how you determine that.??? Clark


    0100015401180421-4695ad99-58d6-407d-b384-42bd10da47d4-000000@email.amazonses.com" type="cite">







  • 5.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-10-2016 13:15

    I apologize.  When I just hit reply, it seems to insert all those pesky Question marks.  I don't know whay, but being an ex-teacher,  it bothered me enough to come on the website and reply that way.  Sorry.   Clark

    ------------------------------
    Clark A. Sprague, RPT
    Bowling Green, OH
    www.clarkspianoservice.com



  • 6.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-10-2016 13:19

    Hi Clark,

    By sound I am referring to the the Tap test that is used when the strings and plate are removed. The Rib Profile element is the "sum of the Height to Width ratio" of the ribs. As a crude example, if all the ribs were 1/2" tall and 1" wide that would be 50% Rib Profile.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 7.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-10-2016 13:32
    Thank you, Chris. I get it. How do you determine that a board sounds
    "stiff"? Clark
    --
    Clark A. Sprague, RPT csprague4@woh.rr.com www.clarkspianoservice.com




  • 8.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-10-2016 13:56

    I guess that's learned through experience. Comparing one to another. Most common are the high pitched boards with their engineering problems.
    I'll be posting examples of soundboards with problems to correspond to the chapter presentations.






  • 9.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-15-2016 11:33

    I think you should teach this at national next year.

    Sheffey Gregory, RPT






  • 10.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-15-2016 11:53

    Sheffey,

    Speaking as an executive of Westpac Regional Conference it is understood that any person teaching classes must have some credentials of professional peer review. I would think this would  apply to the national conferences.

    Roger Gable

    ------------------------------
    Roger Gable
    Gable Piano
    Everett WA
    425-252-5000



  • 11.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 12:08

    Hello Sheffer I am submitting the paperwork.

    Roger, I find your statement offensive, insulting, and unbecoming of a professional. Not something that inspires other people to become members.






  • 12.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 12:29

    Curious as to why you find it so. Your name is one of many in this wonderful invisible world that we call the Internet. Like my name is to you, I'm sure. :)

    If I'm going to a national piano technician convention, I would expect to find teachers who are qualified and have been vetted. There are people who do not really know their subject matter. And there are people who know but cannot teach well. I am not saying either applies to you, BTW.

    Teaching at chapter levels, then at regional, then at national seems to make perfect sense to me. Hopefully by then anyone not qualified has been weeded out by then. 

    ------------------------------
    John Formsma, RPT
    New Albany MS



  • 13.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 12:50

    Hi John,
    You are right and I am currently going through the steps that I have been encouraged to do by some very nice people here.

    Roger and I have a history, and that was nothing but an example of a bully pulpit.

    I am getting wonderful emails from techs around the country so I will continue contributing.






  • 14.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 13:07
    I agree. I also think that anyone hoping to be taken seriously would
    provide some real information, rather than vague hints without
    dimensions or formulae. Even a general outline of method. For instance,
    we not only don't have rib lengths, but we don't have any but
    circumstantial evidence as to whether he's making compression crowned,
    or rib crowned boards. With no mention of crown radii, I presume
    compression crowning. But he hasn't said anything useful to indicate
    either way.

    Also, I think it's very sad that we have come to needing to enumerate
    what we aren't saying when we try to say something because someone is so
    sure to interpret anything we say as personally offensive. We spend more
    time dancing around something than just saying it.

    Ron N




  • 15.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 14:14

    Hi Ron,

    With all due respect to you, i have been very precise, and not dancing around the topic. This is basic engineering. Engineering 101.  In fact, I would not dare go onto an engineering forum with this simple stuff. But since soundboards are engineered,  and my specialty, in my opiniion worthy of discussion with other piano experts willing to learn.

    I realize you may be having trouble with the engineering principles. I assure you, i have not invented anything new here. i simply have put in the hard work (research) and have eliminated the unnessecary terms from one trade and made it presentable to another trade. 

    For example;  I have already posted twice, the formula for stress. It is Moment divided by Section.  Bending Moment divided by the Section Modulus.  Google those. By the way, you use those two principles every time you tune a piano. Or to be a little more precise Moment of Torgue and Section Modulus. As a rough guess, you are probably using 5-10 lbs of force and exerting 200lbf of torgue.

    Hope that's a little more clear. I will go into a little more about Moment, Section, and Stress on my next post.

    P.S. I have not discussed compression or downbearing because of non relevance. I've been discussing principles, not constants and methods.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 16.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 14:35

    Here is an exercise/challenge if someone out there wants to try it.

    Given the Height, Width,Stress load, Force, and soundboard thickness of the rib below, solve algebraically for the length.

    I'll confirm it if you are right.

    Heighth- .43

    Width- .82

    Stress- 1.854 lbf

    Force in Center- 60lbs

    soundboard thickness- .30

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 17.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-15-2016 15:18

    Mr Chernobieff: Great post! Could not find formula quick on Google (Eng.101) but am inspired. 2 ?s for now please. 15sq ft seems too small for board size on a 7 ft piano. How is this figured? Can panels routinely be reused replacing only ribs?

    ------------------------------
    Paul Klaus



  • 18.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 15:33

    Thank You Paul.

    Is that small? Thats 2,160 sq, inches and it looks big when I stand next to it. LOL 

    Regarding reusing a panel. Good question, I have never done it. The problem is getting it out of the piano without half destroying it. With some of that beautiful Adirondack Spruce that used, it sure would be nice.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 19.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-15-2016 15:43

     Maybe turn piano upside down and put wet cloth around rim overnight. Have not tried.Thank you.Thought sq.ft. measurement only included part of the panel.

    ------------------------------
    Paul Klaus



  • 20.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-15-2016 16:03

    Hey Paul,

    Calculating soundboard area can be complex using math formulas trying to figure out odd shapes. So i ended up coming up with a crude way that works for me. After popping out the board, i get 1/4 masking tape and physically map out each square foot. It makes it so easy that you can figure out the square foot from a photo.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 21.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-17-2016 20:46

    the length

    Chris Chernobieff,  2 days ago

    =27"

    ------------------------------
    Paul Klaus



  • 22.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-17-2016 22:32

    The length of what is 27"? There are 15 ribs. This conversation is non productive.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 23.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-16-2016 09:34
    Please refrain from personal and testy remarks on this forum.  The knowledge and understanding of what is being discussed and the application of that knowledge runs from total comprehension to complete mystification.  Remember that.  Do not assume your comments are automatically understood and when questions are asked, please present an answer in a polite manner.  What may seem elementary to you may stretch the understanding of others - who just may want to learn.  We may need to hear some engineering 101 before we can grasp the significance of the discussion.  

    Bill Davis, RPT, SERVP
    2315 Rocky Mountain Rd NE
    Marietta GA 30066-2113
    HP: 770-485-6430
    CP: 770-778-6881
    bill@pianoplace.net
    www.pianoplace.net






  • 24.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-16-2016 12:14
    George,
    Personally, I'd rather see real science and engineering than social
    nicety that isn't instructive. He still hasn't answered my questions
    about the construction of his boards. He either doesn't understand the
    question, or is evading. I think he just doesn't understand.

    Chris,
    You are apparently making high panel compression boards, since rib
    (beam) support alone won't work with the rib dimension and load figures
    you posted. I asked what you were using for rib crown radius and you
    replied that downbearing didn't matter. I assume that means you didn't
    understand what crowned ribs are. With the figures you posted, even a
    rib of 5 meter radius machined crown would be pushed flat by the load
    you indicated unless it was supported by considerable panel compression.
    A rib that is wider than it is tall is characteristic of a compression
    crowned soundboard, rather than a rib crowned or rib crowned and
    supported board. Since you haven't specified this basic information, I
    assume you are making compression crowned soundboards with straight
    ribs. Is that correct? At what panel MC are you ribbing your boards, and
    with what sort of press?
    Ron N




  • 25.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-16-2016 13:31

    testy remarks on this forum

    George W. R. Davis,  3 hours ago

    George; I count 1 possible testy remark by one and at least 6 elsewhere. Refers where? Rhetorical question better suited for PTG-L.or ignored as usual.

    ------------------------------
    Paul Klaus



  • 26.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-17-2016 15:10

    Chris:

    Most people I know are calculating rib scales based on beam formulas which require length,width height and load in addition to the modulus. I would also find it helpful to know if you're using fixed ends or simple ends.  I use fixed ends but some don't.  Center loading is the typical format even though the upper end of the piano deviates quite a bit from that.  

    There will be variations based on the fact the board designers use somewhat different criteria in their decision making and sometimes include things like how much crowning of the ribs is done and to some extent the EMC of the panel at glue up, though it should be noted that the range other than NY Steinway is pretty small, probably 5-6% EMC.  All panels under normal conditions have some compression. Some, as in the case of NY Steinway traditional methods, have more. The actual amount of compression, of course, will vary with the ambient humidity and the panel's ability to withstand compression loads. Load distribution between the ribs does vary from designer to designer.  The panel does add some stiffness but since it the panel contribution is cross grain it doesn't deliver the same stiffness as you would see if you were to increase the rib height by the same amount along the grain.  But it does add some stiffness.  At the same time the rib scalloping will reduce the effective strength of the beam at the edge since most designers use beam formulas with a constant cross sections.  Some will treat those two things (scalloping and the added stiffness of the panel) as offsetting and therefore use the constant beam cross section as the basis for their design..

    It would be simple enough if you (Chris) were to provide complete rib dimensions and the species modulus to determine under a narrow range of parameters how your design compares with others'.  I assume you posted this as a basis for discussion.  Rather than shroud the data in mystery why don't you just post it.  For me that means L, W, H and species at least. I'm not really interested in being quizzed. If you are crowning the ribs more than, say 16-18 M radius that might matter.  Also if you are crowning the ribs are you accounting for the reduced volume as the rib tapers away from the center height?  If so, how?  For me it doesn't really matter whether you are relying on pure compression crowning or building some in in terms of my ability to analyze the rib scale on its own merits.  If it's under engineered then it will be easy to see and conclude that you may need more supporting compression.  Likewise If it's over engineered.

    That being said I do think that for these types of construction there is a "sweet spot" that gives a balance between power and sustain. But as we've seen that can vary some and still produce a satisfactory result.  At some point, however, I believe you can personalize the designs to where they begin to sound strange. Downbearing settings are a separate, though related, discussion.   

    Let's just post the relevant data and see how our ideas compare.  There's room for differences.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 27.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-17-2016 15:58

    Hi David,

    Thank you for the good questions.

    First I have avoided talking about methods of construction because that is not the point. I believe in high compression boards, but not as a 'make up for' any bad engineering.  What I am doing and have done is come up with a simple way to compare soundboards from one make to another. Discover their mistakes if any and fix them with small improvements.  What conditions or methods those boards were made under doesn't matter. Just comparing the boards physical attributes.

    The Weber is the first I posted and i pointed out possible mistakes and how they can be corrected. As more boards get analysed I will have more useful data. I have observed so far that boards that are under engineered are flat  a 100 years later. The two that are over engineered still have full crown and sound great a 100 years later. So I think the engineering matters.

    I am soon to be popping a board out of a M&H BB. I will post the rib data side by side with the rib data of the Weber for your study.

    Center loading beam formula is the least useable. More useable and accurate is the One off center formula (I already posted an example), and the two force beam formula. 

    On the open vs fixed beam test to determine the proper MOE. Both are incorrect for soundboards, and will give you an incorrect deflection amount. Iv'e done both and rejected both. MOE for Spruce is roughly 1.9 Million on an open end. For fixed it is roughly 3.6 million. I actually applaud you for noticing and checking into that. As for soundboards the MOE is roughly 3 times that, and vary to size. 

    You asked me a lot of questions so I dont know if i got them all or not. Its much easier to convey the info in a class setting with actual soundboards to compare and look at, along with their data.

    Again I will post the rib data on two rib scales side by side mid may.

    Thank you David.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 28.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-17-2016 16:15

    And on the question of rib shape.

     From an engineering point of view (and simplicity),it made sense to use an unaltered rib profile as a basis. I assume that anything that is taken away from that, goes to what i call an "uncertain engineering" and has a further weakening effect.  So if the rib resistance upon design is "just" strong enough, then it had been severely weakened when planed by hand.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 29.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-17-2016 19:39

    Actually all I've asked is dimensions, materials (modulus), and load, several times now. I'll assume you don't want to give that information. But without it I can't participate in the discussion. 

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 30.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-15-2016 18:04

    John Formsma wrote:

    "If I'm going to a national piano technician convention, I would expect to find teachers who are qualified and have been vetted. There are people who do not really know their subject matter. And there are people who know but cannot teach well. I am not saying either applies to you, BTW.

    Teaching at chapter levels, then at regional, then at national seems to make perfect sense to me. Hopefully by then anyone not qualified has been weeded out by then."

    John, that sounds like a good way to go. However, I am not sure that what you have outlined is how instructors for the national convention are chosen, either now, or in the past. In fact, I am often frustrated at how so many in our organization do not seem to have a clear notion as to what constitutes a good teacher, particularly when we have so many great instructors among our members. (For example, if you look it up "teacher" in the dictionary--and your dictionary is any good--you should see a picture of LaRoy Edwards!) 

    ------------------------------
    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483



  • 31.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-16-2016 13:40

    Hi Ron,

    Thank you for your questions, I appreciate them. I admit I was taken somewhat aback by your aggressiveness and so I shortened my replies, and because of that, my response may have had a harsh tone. So I apologize for any mis-spoken words on my part.

    George I am sure meant well, as any good leader would.

    My system of analysis, (as would any system) has built-in assumptions. It would be impossible to calculate every nuance.  Nor would that be practical. I have kept it to 6 basic elements (Force, Resistance,Board sq ft, Rib Count, Rib profile, Rib Stress) that I feel are the most important for analysis. It also keeps it simple and makes analysis quick.

    For your concerns on compression, how would you quantify that? And input that strength value into a computer? How would that be helpful?

    I do measure the thicknesses of each board, and that becomes part of the Height of the ribs.

    Downbearing for analysis purposes, I feel is a constant and not an element. In my software, I keep an eye on 3 downbearing types. The actual downbearing, the Max downbearing, and the % between downbearing.   

    I also wanted to avoid methods of construction as there are most likely many “recipes” and systems to construct soundboards. And people get protective of their methods. I believe that I have created a valuable tool that is all inclusive not exclusive. Believe it or not, I respect all those methods. I just love soundboards all together.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 32.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-16-2016 14:17
    On 4/16/2016 12:39 PM, Chris Chernobieff via Piano Technicians Guild wrote:
    > Hi Ron,
    >
    > Thank you for your questions, I appreciate them. I admit I was taken
    > somewhat aback by your aggressiveness and so I shortened my replies, and
    > because of that, my response may have had a harsh tone. So I apologize
    > for any mis-spoken words on my part.

    Just the problem of lack of basic information. Aggressive? Because I ask
    specific questions and expect logical answers? If so, we could use a lot
    more aggressiveness in these discussions.


    > My system of analysis, (as would any system) has built-in assumptions.
    > It would be impossible to calculate every nuance. Nor would that be
    > practical. I have kept it to 6 basic elements (Force, Resistance,Board
    > sq ft, Rib Count, Rib profile, Rib Stress) that I feel are the most
    > important for analysis. It also keeps it simple and makes analysis quick.

    Yes I understand, bur calculating the gross weight of the rivets in a
    bridge doesn't give you the bridge's load capacity without a few more
    details.


    > For your concerns on compression, how would you quantify that? And input
    > that strength value into a computer? How would that be helpful?

    No, I asked at what panel moisture content you ribbed your boards. This
    is important to the method and the result of any soundboard type. It's
    also the only way we have to estimate the compression levels in the
    panel. The actual number depends on the density of the wood in the
    individual panel.


    > I do measure the thicknesses of each board, and that becomes part of the
    > Height of the ribs.

    Yes, you said, though a cross grain panel is far different from the
    similar thickness of additional rib depth. I understand what you have
    said you do. What I'm after is the lacking information.


    > Downbearing for analysis purposes, I feel is a constant and not an
    > element. In my software, I keep an eye on 3 downbearing types. The
    > actual downbearing, the Max downbearing, and the % between downbearing.

    Yet again, I made no request for downbearing, and am not concerned with
    it. I asked if you were using flat ribs or ribs with a machined in
    crown. Crown is not downbearing. Are you crowning your ribs?


    > I also wanted to avoid methods of construction as there are most likely
    > many ???recipes??? and systems to construct soundboards. I believe that I
    > have created a valuable tool that is all inclusive not exclusive.
    > Believe it or not, I respect all those methods. I just love soundboards
    > all together.

    MC at assembly is an absolutely necessary factor to any type of
    soundboard assembly. Do you dry your panel down when you glue the ribs
    on? Is the clamping caul flat, or dished? What you are doing is
    absolutely specific to these things, just as what I do is. You may well
    have a good way to design a compression crowned board, if there is such
    a thing. A compression crowned board, for instance, is dried to
    4%-4.5%MC, a flat rib glued on, and usually pressed into a curved caul.
    A rib crowned board is dried to about 5%, a crowned rib glued on, and
    pressed into a caul of a radius similar to that of the rib. A rib
    crowned and supported board is typically dried to about 6%MC, a crowned
    rib glued on, and pressed into a caul of a crown radius similar to that
    of the rib. The difference is that the CC board is entirely panel
    supported, with the flat ribs resisting the formation of crown. The RC
    board is partially panel supported, and a relatively light rib scale is
    acting as a structural support member, supporting rather than resisting
    crown. An RC&S board is almost entirely rib supported, as if the panel
    wasn't even there, though in fact, the panel does supply some small
    degree of support.

    Each of these types of construction require different rib scaling, so my
    questions aren't arbitrary or aggressive. I'm attempting to get basic
    information that is meaningful in some sort of context.
    Ron N




  • 33.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-16-2016 14:24

    If you really believe that a CC board is totally panel supportive, then don't put any ribs on the next one. I'd like to see that.






  • 34.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-16-2016 14:29
    I see you don't understand. I'll quit bothering you.
    Ron N




  • 35.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-16-2016 16:00

    Chris: Sorry. I do not get you on this (CC?) either. Thanks Ron for explaining difference with 6% and board support as that was another ? for me. Chris: Still mostly on taxes but will try your formula eventually. I also wonder how species of wood figures in calculations. Any old wood would do. Ha,ha Balsa/hickory ok? 

    ------------------------------
    Paul Klaus



  • 36.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-16-2016 16:21

    Hi Paul,

    CC was Rons abreviation for Compression Crown. He and i believe differently on compression theory and the strength of it to support downbearing. From an engineering perspective mass is mass. An arch an arch.  Sure there are fluctuations. For example, could a 2x4 of the same species and size be stronger than another?

    Sure.

    I think of compression like that as far as added strength is concerned.  I think one should make a soundboard in the way that they are compfortable with the results. Engineering has built in safety factors to compensate. 

    My system will simply show if a board is under engineered. I suppose you have to assume that the invisible compression force is performing when the mass is under performing.  But gravity and the downward force will eventually overcome an under engineered board. Will that take 5 years? 50 years? Do the advantages outweigh the disadvantages? 

    Different species would only matter in the deflection formula. Each species has its own MOE so make sure that you are using the correct one in the deflection formula.

    Good luck with the balsa wood soundboard! LOL

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 37.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-16-2016 20:53

    Chris: I know CC stands for compression crowned but one needs the ribs to form the crown by restraining one side of the panel as it re-hydrates from being dried to 4%. 

    ------------------------------
    Paul Klaus



  • 38.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-17-2016 22:59

    Sorry Paul the answer was 9. But not a bad try.

    David here is the data you wanted. I didn't include any MOE as that is program specific and would depend on what parameters you want to use. So my MOE would do you no good. The weber soundboard thickness is.31 throughout. And not sure the totals will do you any good as you have expressed the disapproval of my dispersion method. Enjoy the rest of the weekend fellas.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 39.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-18-2016 09:40

    OK. What species of wood for the ribs: sugar pine, white spruce, Sitka? And what is the total load? I thought I saw ~900lbs earlier in the discussion.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 40.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-18-2016 09:57

    I'm not certain of the exact species of the Weber board. Could be Red Spruce.  Load is 19.53 Tons = 39,058lbs. I came up with 901lbs downbearing.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 41.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-18-2016 16:31
      |   view attached

    So I've attached my analysis using just a couple of metrics that I employ.  I've analyzed this based on sugar pine ribs (which they probably are), Red Spruce would add some stiffness though the trend would be the same.  I've posted your rib scale (I've reversed the rib numbers since Rib #1 is usually the lowest bass rib, I think you had them reversed based on the lengths), followed by how I would approach this design were I making a set of ribs from scratch using sugar pine, which I usually don't use.  I've spread the design load as I typically would in a scale design.  Others may have a slightly different approach.  I've purposefully arranged it so some ribs are taller and some are wider to demonstrate that the MOI doesn't much pay attention how the rib achieves this particular output. The ratio itself doesn't really matter as a determinate value.  A wider rib will need to be less tall and a taller one less wide.  The height of the rib contributes more in terms of stiffness by a factor of 3, as you know.  I use fixed ends formulas not simple ends as I explained earlier.  Rib scale performance is based on a constant cross section.  The scalloping of the rib removes some strength and the addition of the panel, even with some panel thinning, adds some.  I do thin the panels.  The amount depends on the panel species.  If the ribs are more or less crowned than the 15M radius with or without compression one might choose to alter the design slightly.  I use a 18M radius with some compression (EMC = 5 - 5.5%, pretty typical) which results in something near a 15M radius with some compression.

    I prefer my rib scale over yours for this one.  The deflection characteristics and MOI are smoother and transition better.  Yours is weak in the bass end in particular.  I do use other metrics as well which I have not included but this gives a very basic view of how the board will perform. 

    David Love

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320

    Attachment(s)



  • 42.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-18-2016 20:47

    Hi David,

    Thank you for sharing, that was very educational to see how you would rescale the weber. Below are a side by side comparison of the original, my modification and your modification. One thing I can say is that your changes have no comparison to anything historical I have studied so far. I have tried to stay close to the original, with the intention of finding small improvements to their design if any. You totally changed it to something different with the rib profile at 102%. Your braver than me!

    Thank you again, hope to meet one day!

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 43.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-18-2016 21:32

    By 102% I assume you're talking about height to width relationships. I think if that is your basis of analysis then we don't have much in common. I don't think that has any real relevance to performance. It's just observational data, a correlation=causation type of approach. As in rhetoric, that is a flawed argument.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 44.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-18-2016 22:15

    Chris: Do I have this correct? If lighter is better then the 10.61 wins.

    ------------------------------
    Paul Klaus



  • 45.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-18-2016 23:03

    Not exactly. The 6 elements are interconnected. You change one, you compromise  the others. Mr. Albert Weber and I believe in a low rib profile. The Weber grand had a great reputation so I don't know on what basis you make such a radical change from a proven design. And none of the historical instruments I have studied are 102%.
    I think that number is good for a floor joist, not a sounding board.






  • 46.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-18-2016 23:59

    Chris; I believe your panel thickness counted toward rib depth. Is it silly to ask if wider ribs decrease board size overall since more of the panel is glued down and devoted to ribbing.

    ------------------------------
    Paul Klaus



  • 47.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 07:28

    I calculate rib and panel separately and add them together as a whole. so I can adjust either.  Interesting here is that I am seeing thin panels on large instruments, and thick panels on small pianos. You'd  think the smaller the piano the thinner the panel.






  • 48.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 00:21

    Unfortunately "belief" doesn't take you very far in this field.  The industry is replete with soundboards whose ribs are taller than they are wide both historical and current models. Yes, the elements *are* interconnected and if you change the height then you must change the width if you want performance to be on par. Since the height factor contributes more strength, then taller narrower ribs will have somewhat less volume and therefore less mass than wider shorter ribs. But in practical terms it's not enough to make a difference.  I can design you two panels, one with taller ribs and one with wider ribs that for the purposes I've outlined will perform similarly.  It's not a difficult exercise.  

    The issues with the numbers you posted are the consistency with the load response from rib to rib.  The MOI's are uneven, the load bearing properties are inconsistent and inadequate in some areas given the likely load distributions.  That's the issue.  If you are going to redesign a rib scale then it should make sense, this one doesn't, IMO.  It's not that far off but for a redesign it misses the mark, again IMO.  YMMV.

    Perhaps others with design experience will comment.  I don't profess that my design's are exactly like everyone else's.  I know some designers who participate on this list who do things as little differently.  But the basic design criteria is fairly consistent.  

    If you don't think ribs should ever be taller than they are wide take a look at Wayne Stuart's designs sometime.  You might be shocked.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 49.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 07:57

    David the stresses are different from rib to rib because each rib is a different length, accepts a  different load. The only way to make that even is change the shape of the piano, or artificially even out the load. 
    The stress differences may seem like a lot, but it's not. One at 2000lbs and another rib at 2500lbs would be similar to two tires on your car- one at 50lbs and the other at 49lbs. We'll within a safety margin. The stresses  are well within the 1/5 rule of MOR. 






  • 50.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 11:31

    The load is distributed by the bridge and panel to some extent. If you press down on rib #7, for example, #6 and #8 will deflect.  

    I find your MOR values at ribs 1-4 and 14 (that's my rib ordering) to be inadequate for normal bearing settings.  However, you could probably back off the bearing there and get things to within limits.  The adjacent ribs, on the other hand have enough capacity for normal bearing settings.  So it creates a conundrum.  The load bearing capacity of Rib #11 is probably much more than is needed and the transition from 11 - 14 is too precipitous. The creates a poor transition in the MOI values.  One section of the board will want to react relatively easily but an adjacent section will not. That's not the best design, I don't think.  

    Similarly the MOR values lack cohesiveness.  They don't need to be equal but they should fall within a range.  I find that you have a two ribs next to each other in a couple of places (I mentioned some), one of which has acceptable MOR values and the other does not.  While the adjacent ribs will help to support their weaker brother, each rib should carry its own weight, so to speak.  Makes for a happier family.

    It appears we have a different approach.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 51.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 17:06

    Mr. Love,

    As I mentioned in another related thread, my copy of "The Big Book of Soundboard Design" got lost in the mail. I am as usual quite impressed with the quality of your analysis and your ability to write clearly about it.  I am curious about the tools you employ in your design and analytic work.  Are you using a commercial software or are you doing your own calculations using various source materials? You have written authoritatively about the engineering properties of different species of wood and the compression strength of panels and I am keenly interested to learn where that kind of knowledge can be obtained.  College trigonometry was as far as I got in math and that was 35 years ago so I'm kind of hoping I don't have to attempt a degree in mechanical engineering to understand exactly what it is you smart guys are talking about.

    Mr. Chernobieff,

    I am curious if this recent series of threads is a prelude you making a rib and soundboard analysis software available for purchase.

    Fascinating topic. Best regards to all involved.

    ------------------------------
    Karl Roeder
    Pompano Beach FL



  • 52.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 17:57

    Hi Karl,
    I use excel.  Start with the rib dimension  article in the journal April 64 I believe. Beam formulas( there are 3) are in the 27 machinery handbook. A good example of how in depth one formula is, is in my other posts.






  • 53.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 17:31

    Start with the rib dimension  article in the journal April 64

    Chris Chernobieff,  23 hours ago

    Chris: How? could not find on PTG site so far.

    ------------------------------
    Paul Klaus



  • 54.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-20-2016 19:06

    Hey Paul,
    It's in the PTG Soundboard Installation reprint kit. I don't want to violate any copywright laws. I'm sure if you call the head office they would make a copy of that article for you.






  • 55.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 08:25

    Chris: Thanks. Thought old journals were available for member use but that I lacked skill to access.

    ------------------------------
    Paul Klaus



  • 56.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 09:05

    Interestingly, on our companion site the online store only seems to have two journal re-print collections available. One on keys and the other on dampers and trapwork. That's a shame as I have found the ones I have covering various types of belly work to be really helpful over the years.

    ------------------------------
    Karl Roeder
    Pompano Beach FL



  • 57.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 09:36

    Paul

    The PTG 1979-2010 DVD contains the catalog of reprints. There are 9 reprints available including Soundboard and Installation.

    For members, the cost of the DVD is $50.00

    Paul

    ------------------------------
    Paul Brown, RPT
    Vancouver, BC Canada
    Email: paulbrn@telus.net



  • 58.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 10:56

    Paul: Thanks but the desired article was from a 1964 journal or do you mean it is necessary to buy the 1979-94 DVD in order to access info on obtaining older reprints. Sorry I get it not.  

    ------------------------------
    Paul Klaus



  • 59.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-21-2016 11:04

    The reprint kit I have was published in 1995 that contains the older articles. Again call the office. In the past(before being a member), I had asked for a certain article. They were more than happy to oblige. Its worth getting the whole kit. As Karl mentioned the soundboard installation kit has much useful information.






  • 60.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 11:13

    Chris: Thanks. Been trying to learn computer skills. Hermit kind of new to I-net. Call works. Maybe I'll also find my chapters' newsletter if there is one.

    ------------------------------
    Paul Klaus



  • 61.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 11:23

    Paul,

    I'm looking at the article now from April, 1964 in the Reprints Section of the 1979-2010 DVD. It's all there.

    Paul

    ------------------------------
    Paul Brown, RPT
    Vancouver, BC Canada
    Email: paulbrn@telus.net



  • 62.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 11:31

    Paul

    You can do as Chris suggests and ask HO for that one reprint. However, if you have other reprints you want in the future, it would be far easier to purchase the DVD online for $50 and then you have all of the articles and reprints at your fingertips.

    I refer to the DVD all of the time.

    Paul

    ------------------------------
    Paul Brown, RPT
    Vancouver, BC Canada
    Email: paulbrn@telus.net



  • 63.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 15:46

    Paul B: Thank you so for suggestion but my beginner computer lacks reader. Impertinent for now anyways. Since 94 I have not even had/needed a proper workbench but at one time had small active shop w hoist. Just planning for retirement.ha ha

    ------------------------------
    Paul Klaus



  • 64.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-18-2016 10:02

    David: Total column adds to 900.7lbs. Many premises that seem questionable.

    ------------------------------
    Paul Klaus



  • 65.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 18:51
    Karl,
    Something very much needs to be understood here that isn't being
    addressed. Three significantly different types of soundboard
    construction are being discussed. Chris is talking about compression
    crowned (CC) boards with flat ribs, crown being supplied by the panel
    rehydrating after the ribs are glued on. This is the traditional
    construction technique that has brought us concave crowns, killer
    octaves, and trebles that "dink", with little to no sustain. The ribs in
    this type of construction are resisting crown as the panel must both
    bend the rib and support downbearing. CC boards depend entirely on the
    panel, which is never the same from one piano to the next, so the
    results are very erratic and unpredictable. The compression stress
    levels placed on the panel by this construction method exceed the
    physical limitations of the spruce used to make the panel, so the life
    of the panel is anyone's guess. Stress on the ribs in this construction
    is inconsequential. It's the panel that is destroyed by the method.
    Moisture content at assembly is typically 4%-4.5%.

    David is talking about rib crowned (RC) boards in which the ribs are
    crowned, and act as support beams, aiding in the support of crown and
    downbearing, and aided by moderate levels of panel compression to supply
    more stiffness than the ribs alone would. This is a far superior
    construction method than CC, as the rib support takes much of the
    compression stress from the panel, so it produces both a more
    predictable, and a longer lived assembly. Being support beams, the ribs
    will be not only crowned, but taller than they are wide, and stiffer
    than CC ribs. Because they ARE joists. It is a common construction
    method used in manufacturing today. Rib stress is low, but panel stress
    is still toward the upper limit of the material's tolerance, but much
    lower than in CC construction. This is a good construction method.
    Moisture content at assembly is typically 5%.

    I build rib crowned and supported (RC&S) boards, as do some other techs.
    This is what Del Fandrich did for Walter, and is doing at Young Chang
    currently (I hope). Ribs are crowned, and are load bearing structural
    members. They are stiffer than RC ribs because RC&S boards don't depend
    on panel compression at all to support crown and downbearing. They also
    tend to have higher crowns from shorter crown radii to allow more
    "spring" travel from the ribs as the panel offers less restriction to
    that spring travel. RC and RC&S assemblies are similar in stiffness, but
    the stiffness comes more from panel compression in RC boards and from
    rib stiffness in RC&S boards. Stress on the ribs is more than in RC
    assemblies, but still well within the long term comfort level of the
    material (spruce). Panel compression stress is very low, which is what
    this method is about. No parts of the assembly are anywhere near
    destructive stress levels, which makes this construction method as
    predictable and as nearly immortal as it's possible to build soundboards
    with spruce. Moisture content at assembly is 6%-6.5%. I use 6%.

    Soundboards with high panel compression levels are, in my experience,
    more tolerant of hard hammers, so if you like bright pianos, you want a
    RC board.

    Look up beam deflection formulas, using 1570000 as the MOE for spruce.
    Download http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf and
    look up any figures you might like on stress, strain, rupture,
    compression, long term accumulated damage, and any other thing you might
    consider appropriate, and learn, by species, what wood is and what it
    does when it's abused. This is a terrific resource that every single one
    of us should have.

    And good luck following all the non specific discussion. There is
    engineering, and there is numerology. This book will help you
    considerably in sorting out which is which. If you really are
    interested, this is really what it takes.
    Ron N




  • 66.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 20:58

    Its a shame that ron explains the three methods so eloquently, and yet feels compelled to ruin it with personal insults at the end. Numerology ron? Not engineering? Whatever ron.

    The MOE ron gives for Spruce is not even correct for an open beam, let alone a fixed one, and further let alone a soundboard. For open beam its 1.9Million not 1.57 million ron. Easy to prove on the benchtop too! My benchtop test shows some Spruce to be up to 2.1Million.  Fixed Beam around 3.6 Million or more. I check each new stock when it comes in.

    And his assessment of why soundboards fail is blamed on the wrong culprit if you ask me. Maybe some techs believe in compression voodoo but I dont. My opinion (Just my opinion ron) of why boards have failed is because of insufficient mass for the downbearing, and improper rim contour.

    My "numerology not engineering" chart simply shows if the mass is sufficient, not enough or too much. Which is valuable in comparing one maker to another. Made today or made in the past. Method dont matter for analysis, but the result of those methods do. The correct mass is the final answer, regardless of which method got you there. In my opinion.

    Chris- Piano Numerologist 

    LMAO

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 67.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 21:44

    Just in fairness, i wanted to look into the MOE values a little more. I checked several sources of Sitka Spruce MOE's. The MOE values are all over the place from 1.13 Million to 1.97 million. Thats a lot. Sugar Pine is 1.19 Million. 

    This source said 1.6Million Sitka Spruce

    These are all based on 12%MC and open end testing.

    I tested different species in my shop and my MOE's were always higher.  With the proof of correctness being able to accurately compute downbearing. To solve for MOE use the downbearing (algebraically switch) formula.

    MOE = Force *(Length^3) /48* Deflection* MOI

    MOI = H^3*W/12

    As said earlier MOE's really went up for fixed ends.

    Wood is interesting material.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 68.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 22:07
    > Its a shame that ron explains the three methods so eloquently, and
    > yet feels compelled to ruin it with personal insults at the end.
    > Numerology ron? Not engineering? Whatever ron.

    Why would you take that personally and be offended? A little studying up
    on basic engineering principles and the properties of wood by your
    readers should vindicate you, shouldn't it? You ought to welcome it. I'm
    surprised you didn't post the URL to the Forest Service publication
    yourself, in support of your engineering examples.


    > The MOE ron gives for Spruce is not even correct for an open beam,
    > let alone a fixed one, and further let alone a soundboard. For open
    > beam its 1.9Million not 1.57 million ron. Easy to prove on the
    > benchtop too! My benchtop test shows some Spruce to be up to
    > 2.1Million. Fixed Beam around 3.6 Million or more. I check each new
    > stock when it comes in.

    Moe isn't specific to the way a beam is mounted. It's specific to the
    material. Use whatever you feel is appropriate and accurate. My own
    deflection tests indicate that 1570000 is pretty close for Sitka. Again,
    your readers can vindicate you by doing tests of their own.


    > And his assessment of why soundboards fail is blamed on the wrong
    > culprit if you ask me. Maybe some techs believe in compression voodoo
    > but I dont. My opinion (Just my opinion ron) of why boards have
    > failed is because of insufficient mass for the downbearing, and
    > improper rim contour.

    Insufficient mass for the downbearing? That's certainly revolutionary.
    Odd that I don't recall rim contour being included in your engineering
    calculations. Where is that calculated in, and how do you correct it
    when you redesign a board? This just keeps getting better all the time.
    Meanwhile, they can look up cross grain compression limits of their
    panel wood of choice in that Forest Service publication and calculate
    for themselves what levels of compression a panel is under in a CC
    board. I'd be pleased if they did. This is supposed to be educational,
    after all. You might want to look in to it yourself.


    > My "numerology not engineering" chart simply shows if the mass is
    > sufficient, not enough or too much. Which is valuable in comparing
    > one maker to another. Made today or made in the past. Method dont
    > matter for analysis, but the result of those methods do. The correct
    > mass is the final answer, regardless of which method got you there.
    > In my opinion.

    Ah, that's where I got confused. Somehow, I couldn't manage to equate
    mass to the proportion of width to height. Somehow. I was still
    struggling with stress resulting from that same proportion of width to
    height, and how that worked. What happened to that? Did it become mass
    and downbearing somehow, and I missed it?
    Ron N




  • 69.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 22:38

    Ron,

    How come my 40 year old compression crowned, flat ribbed rebuilds still have the same singing trebles that had when I built them? There is no conclusive evidence to support your contention that compression crowned boards will self destruct and that the trebles are bad. Pianists and technicians rave about the treble tone quality my rebuilds have.

    I have seen boards that were bellied at higher MC than compression crowned boards, and some of these developed cracks quite quickly when subjected to a few weeks of 35% RH. These same boards showed no evidence of compression ridges before cracking.




  • 70.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 22:45

    Maybe the better question is why did you have to replace the board in the first place?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 71.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 23:10
    > How come my 40 year old compression crowned, flat ribbed rebuilds
    > still have the same singing trebles that had when I built them?

    Likely because of the climate you are in. In benign climates, they can
    last for a long time and work quite well.


    > There
    > is no conclusive evidence to support your contention that compression
    > crowned boards will self destruct and that the trebles are bad.
    > Pianists and technicians rave about the treble tone quality my
    > rebuilds have.

    I'm happy for you. In the plains states, the midwest, and the northeast,
    CC boards don't fare nearly that well. Or maybe it's just your magic touch.


    > I have seen boards that were bellied at higher MC than compression
    > crowned boards, and some of these developed cracks quite quickly when
    > subjected to a few weeks of 35% RH. These same boards showed no
    > evidence of compression ridges before cracking.

    Here, I've seen new pianos come off the trucks from the factory with
    flat boards, extreme killer octaves, and dead trebles. Steinways, and
    Baldwins particularly. I know, Baldwins are rib crowned with a 72'
    radius, which makes them not far from CC boards.

    Any general observation any of us might make is subject to the exception
    that someone will be guaranteed to trot out. Anyone in areas of the
    country subject to extremes of climate, such as I listed, who has paid
    attention to soundboard function and general health will tell you the
    same thing. West coasters tend to be of the opinion that soundboards
    don't die at all, since their climate is generally kind to CC boards.
    This comes up every single time soundboards are discussed. Time after
    time after time after time as if it's brand new. It's not. If I lived in
    a benign climate, I wouldn't see the problem either.
    Ron N




  • 72.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 23:34

    Ron, How come the two new boards I mentioned that cracked, cracked here in the Pacific North West?

    I have taken compression crowned pianos that some technicians pronounced "dead" and corrected bad bridge caps, bad capo bar shape, bad plate drilling, and inadequately tone regulated actions and turned them into "singers". Plenty of pianos move to the west coast after being ruined in the midwest and/or east coast so I have seen and replaced plenty of dead boards. 

    Ron, you rail at posters here for anecdotal reporting but almost all of your reporting is equally anecdotal. The voices I respect are those of technicians who have shown examples of their work to be exemplary musical instruments. There is no conclusive evidence to support all of the  complaints you level at compression crowned boards.




  • 73.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 01:55

    Living in a benign climate I concur with Ron on this.  I see and take apart a lot of pianos that have lived on the west coast their entire lives that are often (and even then not always) in pretty good shape with boards that are still functioning fairly well.  Even then there is some inevitable degradation after a certain point.  On the other hand, pianos that I can track to having spent most of their lives in harsher climates, mid west, east coast, are rarely, if ever, in good shape even after a relatively short time unless they've been seriously humidity controlled.  It should be noted that soundboard degradation is often not that noticeable in certain ranges.  I've had people say to me "but the bass is great".  Well, it often is but you can make a good bass out of washtub.  The tenor and treble are where the rubber meets the road.  

    I would guess that the benign Pacific Northwest climate has a lot to do with the continued good performance of those boards. I'm sure the quality of the workmanship was also a factor.   

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 74.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-19-2016 22:32
    Centre load on beam with two fixed supports    δ = FL3 ∕ 192EIWith the load at the centre, the deflection at distance a from the fixedsupport (where a is less than or equal to L ∕ 2) is:    δ = Fa2(3L – 4a) ∕ 48EI
    Centre load on beam with two simple supportsδ = FL3 ∕ 48EI

    If you compare the fixed versus simple ends formulas you'll notice that the value of Young's Modulus, E, does not change, it's a constant value.  It's true that there are variations even within a species but ultimately, for these calculations, there is only one value.  I think you have a basic misunderstanding here.  

    The MOE and other characteristics from reliable sources that I have found (and there are several) indicate:

    Red spruces falls somewhat below Sitka and there are different species of "White" spruce.  But this gives you an idea.

    I would not use mass as a basis for determining deflection characteristics (just as I wouldn't use the height to width ratio). In fact, the specific gravity, as you can see, can be misleading in terms of the stiffness.  Sugar Pine has a higher specific gravity (density) than Engelman Spruce yet Engelman spruce has a higher MOE.  You can also see that the FSPL (fiber stress at proportional limit) value does not move necessarily in the same direction as the MOE or SG.  Hoadley's book "Understanding Wood" is a very good resource. There are also several government resources available.   

    Ron's points are well taken and different designers will target different formulas based on their specific goals and methods.  Each of those methods will, in my experience, produce somewhat different results.  It's not really a problem, until it is.  That is, until it deviates from expectations to such a degree that one doesn't like the aesthetic outcome or the assembly fails--usually there is a tonal failure that accompanies that.  That can, and does, sometimes happen and we see historical examples of that all the time.  Of course the purpose of quantifying these things in a meaningful way is to avoid that, and we can.  Where the line is drawn between modest success and something really nice can be difficult to determine exactly but the more you do the better you get at predicting outcomes. I use a method that consistently produces what I like and I understand pretty well how to vary the design in order to make changes.  I presume others do to.  The rib scale can, in my view, be too light or too heavy.  For my own preferences there is a fairly small window and also a way in which the ribs should work together and distribute the work of bearing the load between them.  That gives unity and balance to the assembly.  It's important.

    Generally speaking CC boards tend to have lighter rib scales, RC&S boards as Ron describes them, tend to have heavier rib scales but there are variations within each designation and sometimes the lines get blurry.  RC boards tend to fall somewhere between the two but each designer must choose how to put together all the criteria and related features such as panel thickness, EMC, perimeter thinning (diaphragmizing), grain orientation, rib scalloping, rib radii, load distributions, etc., to get the sound and performance that they want.  It takes some trial (and error) to find the sound that associates with a specific design.  It's a mistake, in my opinion,  to jump to conclusions about cause and effect without considering all the criteria.  Some things matter and some don't.  Mass matters but not as an indicator of load bearing properties and I would not substitute mass for stiffness.  The two things perform different functions in a soundboard.  What we want is light but not too light, stiff but not too stiff, and for different reasons.  

    In answer to Karl's question.  I use my own excel spreadsheet which, honestly, took years to develop to where it is now.  I had help along the way from various people (mostly engineers) to clarify the engineering issues and to help to tease out some of the variables.  I'm not bashful about  asking lots of questions.  I am not an engineer by formal training and many of my engineering friends will tell you that I know enough to get in trouble but not quite enough to get out of it ;-).  As time goes on, however, I find that I've learned enough to avoid most of the trouble in the first place. All the information I gathered and used to develop the spreadsheet is in the public domain and accessible to anyone who wants to take the time.  Of course there is nothing better than the experience of building something in conjunction with detailed analysis and design work.  As Del Fandrich once said to me (a paraphrase), at some point you have to shoot the designer and build the damn thing.  You find out a lot that way and hopefully you don't make the same mistake more than once or twice.  It gets expensive.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 75.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 23:00

    David,

    You wrote,

    "If you compare the fixed versus simple ends formulas you'll notice that the value of Young's Modulus, E, does not change, it's a constant value.  It's true that there are variations even within a species but ultimately, for these calculations, there is only one value.  I think you have a basic misunderstanding here."  

    This is one of the things i don't think is true. 

    Do a bench test yourself.  

    Use the standard formula below.

    MOE = Force *(Length^3) /48* Deflection* MOI

    MOI = H^3*W/12

    Get a small board ( I used something like .75" x .75" x 24") add some weight and record the deflection. Keep adding weight record the deflection. You don't have to go to the MOR just the proportional limit.  To find the PL, chart it on excel, and when the curve suddenly changes you've reached the PL. 

    You'll see that the MOE is variable. And you'll discover that your deflection values are way off.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 76.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 01:30

    The differences between the two formulas take care of the changes in deflection when the ends are fixed versus not.  The E in the formula the same number.  This is getting pointless.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 77.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 10:08

    My deflection values are based on the ribs alone and don't take into account non linearity. They don't mean to represent exactly what happens to the entire assembly. They determine the relationship between the ribs and anticipate the completed structure and the changes that will occur when everything is assembled. I use these numbers for calculating the rib scale not for describing the actual completed soundboard.

    The assembly actually becomes stiffer when you glue on the panel and then glue the panel into the rim as a domed structure. It then behaves as a non linear spring which is what you describe. It doesn't really have anything to do with the changing of Young's modulus of the species. That's not what's happening even if you want to see at it that way. You'll have to look further into non linear spring behavior.

    My deflection values on the spreadshee I gave are about 80% of the total crown values. In actual performance the assemblies deflect about 60%.  But deflection is an absolute value. The percentage will depend on the amount of crown. If I calculated the scale with those radii at a 50% deflection the resulting structure would be too stiff (for my preference).  A downbearing discussion is probably necessary to completely understand this but I'm done for now.

    Yes it's complicated.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 78.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-19-2016 23:32

    < at some point you have to shoot the designer and build the damn thing. 

    My own process is evolving more along the "build the damn thing" lines these days.

    Though I use a spread I've designed (several times), since I built my calibrated go-bar setup a couple of years ago (thanks to Jude Revely for the go-bar idea), I'm evolving to a much more empirically proofed design process. Empirically proofed, means, I test my as-built board, full perimeter rim clamped for the test, senza the plate. The board is proofed both before and after the bridge is glued on, with full loads applied as they will be applied, at actual load locations...not trended.

    Taking these proofed load tests, I read the performance of the entire complex structure as evidenced by dial indicator deflections at all rib/bridge intersections, and adjust by hand/or electric plane, to a deflection level I determine or that I am experimenting with. I target a smooth deflection curve through the board, and shape the bridge to avoid mucking that smooth deflection curve up, asking the bridge to do as little trending as physically possible. As a general rule, I start too- stiff, and work the structure down by steps. 

    The proofing process is all quite eye opening, and informative. It also cuts out a huge percentage of the poker game...I abhor poker, especially when the ante is $40-50K.

    There are so many structural assumptions that we must make, without any feed back until its too late. Instead of piling assumption upon assumption, as I had been doing, I set out to utilize  feedback loops, much like a tuner employs feedback loops to set a temperament or whatever as he/she progresses through the tuning...ie, let the piano tell you how to design its board.

    Part of this re-think, from exclusive spread sheet work, to empirically proven and adjusted work,  is driven by spending a fair amount of time observing, with the loading equipment just how much the bridge, depending on the ribbing or panel beneath it, utterly distorts the string load distribution. Its really quite something. Along these lines, the load scenario posted on Chris's board, as posted by David, does not conform to any load distribution I have ever seen in my test load work. 

    I had the same problem with my own "guesses" at how the load was actually distributed. Depending on how I guessed that load, all the other statistical info would produce numbers which I found much less informative than I wished. It follows that the as-built behavior only, maybe, kind'a reflected what I had hoped to design.

    Anyway, re someone's comment about the shear number of assumptions the posted analyses made, I quite agree with the slipperiness of the many assumptions we must make in designing our crude spread sheets. For my own preferences, I am evolving my process in a way that makes a huge amount of sense to the way by brain sees and processes the evidence I have observed in my own shop.  Other brains clearly are comfortable designing exclusively from their own evolved spread sheets, but proofing the designs, before its too late, makes a huge amount of sense for my own work and preferences.     

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 79.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 01:44

    I don't think it's that much of a poker game.  My distribution is a "design load" and it works for what I do with predictable and repeatable results.  There are many things that can influence the actual load distribution not the least of which is accuracy cutting the bridge and setting downbearing.  There is some leeway in the actual execution and you can always tweak the bearing after the fact based on what you hear, which many builders do, including me.  I don't find it necessary to try and model each assembly's response by setting up a quasi loading situation.  I don't really think it tells you much.  .  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 80.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-20-2016 11:04

     <My distribution is a "design load" and it works for what I do with predictable and repeatable results.

    This quote is something anyone reading this discussion who is trying to wrap their mind around belly design should understand. Also, we who are using and creating our own belly design spreadsheets should try to be explicit about it as well. That is, a "design load" or any design assumption is a statistical and mental construct. This is what we create with our spreadsheets...statistical constructs.

    As statistical constructs, the sheets are not to be taken as one-to-one formulas. Rather, according to the designer's experience of their own quantified observations, and crucially, the designer's ability to interpret those observations, we look at multiple, imperfect, statistical trends drawn from simplified, incomplete models of a complex system. Looking at these multiple trends visually on a spreadsheet allows the brain to do its own relatively quantified data sort and statistical analysis. We "interpret" the trends our sheets have drawn, and determine what we think will work in this particular belly, or what has worked in previous bellies.

    Those looking to design a belly, and who are looking to purchase software to allow them to design a belly, will always get some answer from a belly designer that goes something like this:  "The sheets are only useful if you have done the personal legwork to understand the interactive nature of the complex system.  Or…the sheets are only as good as your ability to interpret the incomplete data. 1+1 =2 in arithmetic. However, in a complex scenario like this, there are so many variables and so many imperfect  assumptions, exactly what you get when you add 1+1 depends on many factors. The ability to ferret out what 1+1 equals in a particular belly is dependent on the brain work one has done to arrive at one's current but inescapably incomplete "design assumptions".

    Taken in this light, my specific comment regarding "design loads" not representing what I have observed in my shop, should not be taken as an absolute claim to unassailable knowledge of the forces at play. I mean it to say, my take on the loads is consistent with my observations and interpretations of those observations. David’s take, represents his observations and interpretations of his data. One is not right or wrong…the real point is that each designer takes their own data, and assembles it by trail-and-error, in a way that helps achieve their own predictable outcomes in their own work.

    Also, luckily for all of us, the bandwidth of functionality is much larger than we might have expected

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 81.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-20-2016 11:25

    I want to follow in Karl's footsteps and thank everyone for their contribution to this post. One thing this post has revealed, is that soundboard people are VERY  passionate about their craft. And thats a good thing!

    Until next time fellas.

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 82.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 12:31

    A well designed spreadsheet, however, is still a good predictor of what the outcome will be.  I"m not often surprised by what I get and if I were I would rethink the use of the current spreadsheet.  There are also a host of design features being used that I don't really have a handle on exactly how they should impact these types of calculations and outcomes other than based on what I've heard and how I translate sound to elements in the design:  things like radial rib arrays, heavier rib scales with less downbearing, very tight radii on the order of 5 - 9 M, even more radical soundboard shaping, things I don't really do at this point.

    It also might be worth considering that the current 300-year-old paradigm for soundboard making has pretty much exhausted itself. I had the opportunity recently for an up close and personal, detailed introduction to a Stuart and Sons piano by Wayne Stuart. The rib structure, and panel design, is something really quite different and I have to say the results are very impressive.  They also have many other new design features, especially with respect to the bridge, which I won't go into here.  You can see some things on his website.

    It's worth considering that what we're doing and the way we're approaching it has, perhaps, exhausted the practical limits of what we can achieve.  A new look with both new materials and new design approaches is inevitable, it seems to me.  When that happens we'll probably look back and wonder why we kept banging our heads against the same wall.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 83.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-20-2016 14:34
    > A well designed spreadsheet, however, is still a good predictor of
    > what the outcome will be.

    If it isn't, it's not much of a design tool.


    > things like radial rib
    > arrays,

    This came from Conklin. His research at Baldwin indicated it minimized
    spurious resonances. According to me, you get free stiffness in the
    treble as the angle of the rib to the panel decreases.


    > heavier rib scales with less downbearing,

    I don't see any point of that either. I don't know of anyone doing that
    either. Do you?


    > very tight radii on
    > the order of 5 - 9 M,

    I use 4-9M typically. Horrifying, I know, but I don't have to make the
    ribs stiff as tree trunks to support bearing load either, because I have
    the deflection travel to accommodate it with a reasonably sized rib. I
    also have a crown that's high enough that it's not possible for the
    string bearing to force the soundboard flat. The rib strength prevents
    that anyway, but the crown height makes it geometrically impossible.


    > even more radical soundboard shaping, things I
    > don't really do at this point.

    What radical soundboard shaping is that?


    > I
    > had the opportunity recently for an up close and personal, detailed
    > introduction to a Stuart and Sons piano by Wayne Stuart. The rib
    > structure, and panel design, is something really quite different and
    > I have to say the results are very impressive.

    I have too, and they do have an interesting sound. Did you play it
    aggressively? It's not nearly as interesting at anything over moderate
    attack levels.


    > It's worth considering that what we're doing and the way we're
    > approaching it has, perhaps, exhausted the practical limits of what
    > we can achieve.

    I don't think so, by a long shot. The biggest hurdle is the automatic
    condemnation from the established technical community of anything that
    is different from what they were taught and what they personally do. If
    we were individually driven by education in the sciences involved and
    the information accumulated and used in a rational and verifiable
    manner, we would be light years ahead of where we currently are, and
    wouldn't be having these conversations repeatedly to no affect. It's the
    entrenched egos preventing us from doing anything better.


    > A new look with both new materials and new design
    > approaches is inevitable, it seems to me.

    New design approaches are exactly what some of us are doing. This
    doesn't necessarily mean new or exotic materials, but it does require a
    critical look at our accepted beliefs, assumptions, and what we were
    taught by that much quoted but universally anonymous highly regarded
    tech. The silver bullet myth is deep in the psyche of humans. We want a
    simple substitution of an exotic material for a mundane old familiar
    material to work magic, rather than do the substantial work of trying to
    put together a useful education around the science involved and try to
    learn how the thing works in the first place. This will never change.


    > When that happens we'll
    > probably look back and wonder why we kept banging our heads against
    > the same wall.

    No we won't. Not until the holders of the current mythology die out.
    They'll hang on like a tick on a dog to their last breath. The next
    group will have different mythology, but they won't take the time and
    trouble to question anything and try to scrape together some education
    to try to understand it any more than most of us won't.
    Ron N




  • 84.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 11:47

    All I was saying was that my spreadsheet works with the other features in the designs that I do and if those features were to change so might the way in which the rib scale is calculated.  Of course any change in the number of ribs or the length of the ribs will change their dimensions.  That's a given.  I'm talking about the criteria that is used to determine how much the rib scale should contribute to the support when other features might change just what the ribs need to contribute.  For example:

    I understand the reasoning for the radial rib pattern and where it comes from.  However, it also places the ribs closer together on one side (bent side) and farther apart on the other.  How does that affect the stiffness of the assembly or how does one side of the assembly being stiffer than the other affect the tonal response or, more to the point, how would it affect my rib scale design.  Can't say.

    I think you're being a bit defensive on the rib radii.  I wasn't being critical of that decision to go 4-9M  But making the rib with a tighter radius probably makes the assembly stiffer and I don't have a handle how that would change my rib design exactly.  From my own experience and experiments I think it would though.  Additionally, how does making the ribs from a laminate impact the performance.  Again, I don't know the answer to that.  I'd have to look into it further.

    Cutoff bars that are placed to remove enough area from the bass corner and the area behind the bridge to essentially place the bridge in the middle (for the most part) of the panel while maintaining a standard 8 mm panel thickness create a stiffer panel and one with less overall mass.  When you combine that with no panel thinning at the perimeter (which at last reporting you didn't do) then you have again something that reacts differently--it will effectively be stiffer again.  How that would impact my rib design considerations I can't say exactly except that it would likely push it in yet a lighter direction.

    Some people I've spoken to who are making these designs and having them come out stiffer than expected are backing off on the downbearing.  I don't know if that's the right thing to do or not.  Some of the problems that we have heard reported on this list (nasally sounding low tenor comes to mind) are a function of too much stiffness, in my opinion.  Too stiff or not stiff enough? Well if I had to err on one side I would certainly choose too stiff than not stiff enough but it's not without consequences.  

    When all is said and done with those features I outlined above you will likely have an assembly with less mass and  generally stiffer and has all the performance characteristics that go with that.  My own personal experience demonstrates that employing all of these features certainly "works", the sound is good,though the result is different (and no, not all designs that don't use these features have killer octave problems or short term soundboard failure issues), but I can't say that I prefer it and I guess that's the bottom line.  

    So my point is that my spreadsheet and the way I use it takes into consideration the features that accompany it.  If you change those features you may well have to reconsider the criteria that you use to calculate the rib scale.  That's all, I wouldn't read anything more into that statement than there is, unless you want to, of course.  You may have the last word.  I expect you will.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 85.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-21-2016 12:41
    > All I was saying was that my spreadsheet works with the other
    > features in the designs that I do and if those features were to
    > change so might the way in which the rib scale is calculated. Of
    > course any change in the number of ribs or the length of the ribs
    > will change their dimensions. That's a given. I'm talking about the
    > criteria that is used to determine how much the rib scale should
    > contribute to the support when other features might change just what
    > the ribs need to contribute. For example:
    >
    > I understand the reasoning for the radial rib pattern and where it
    > comes from. However, it also places the ribs closer together on one
    > side (bent side) and farther apart on the other. How does that
    > affect the stiffness of the assembly or how does one side of the
    > assembly being stiffer than the other affect the tonal response or,
    > more to the point, how would it affect my rib scale design. Can't
    > say.

    That's right, you can't say. You can't say if it matters or if it
    doesn't. When you or anyone else can tell by listening if the piano has
    a radial rib layout, it will then be a concern. Until then, it's
    something you don't do because you don't know if it matters tonally. I
    don't either, but I accept Conklin's research as to resonance control,
    and if I can't detect a tonal penalty any more than anyone else can,
    I'll take the benefit offered without hinting at mysterious possible
    consequences that are undetectable. What's the point of doing that? Why
    can't we offer practical and beneficial alternatives rather than vague
    hints of doom for deviating from your approach. This is exactly why I
    advocate that people read up on the science and do their own thinking
    instead of following others' advice without explanation. This is why I
    also offer reasons behind why I do things, whenever I can, to give them
    some place to start.


    > I think you're being a bit defensive on the rib radii.

    No, I saw yet another vague caution about radical construction, and
    offered my reasons for doing what I do. Again, reasons. When someone can
    recite rib radii from the sound produced from the piano, I'll believe
    that it's critical. Until then, I'll do what works for me for the
    reasons I've given, and others now know my reasons too, so they can
    decide for themselves what is right and proper.


    > I wasn't
    > being critical of that decision to go 4-9M But making the rib with a
    > tighter radius probably makes the assembly stiffer and I don't have a
    > handle how that would change my rib design exactly.

    No, it doesn't make the assembly stiffer. And no, in spite of your
    continual hammering at it, my soundboards aren't "overly" stiff. As I
    have pointed out (reasons) my rib scales are heavier than yours because
    I keep the panel compression much lower than you do in your boards.
    Speaking of which, Ron Overs makes the stiffest soundboard assembly I've
    ever seen, and a pretty damned fine sounding piano. So I don't see the
    point of your repeated warnings about overly stiff soundboards except
    possibly hinting that everyone else does it wrong except you. Have you
    heard one of Ron Overs' pianos? Have you heard one of mine? I haven't
    heard one of yours, so I can't say how you're doing, but Ron O is doing
    just fine.


    > From my own
    > experience and experiments I think it would though. Additionally,
    > how does making the ribs from a laminate impact the performance.

    It certainly makes the MOE more uniformly predictable. More vague hints
    of doom? Again, when you can tell if a piano has laminated ribs by
    listening to it, that will answer the question.


    > Again, I don't know the answer to that. I'd have to look into it
    > further.

    Further?


    > Cutoff bars that are placed to remove enough area from the bass
    > corner and the area behind the bridge to essentially place the bridge
    > in the middle (for the most part) of the panel while maintaining a
    > standard 8 mm panel thickness create a stiffer panel and one with
    > less overall mass.

    Overall assembly stiffness is controlled mostly by the rib scale.
    Shorter ribs mean you can make them less stiff and they will still do
    the same job as a longer stiffer rib. You should know that. I consider
    less overall mass in the assembly a good thing. Mass distribution is
    something to look at though. Less mass in the bass, and more in the
    treble works quite well.


    > When you combine that with no panel thinning at
    > the perimeter (which at last reporting you didn't do) then you have
    > again something that reacts differently--it will effectively be
    > stiffer again. How that would impact my rib design considerations I
    > can't say exactly except that it would likely push it in yet a
    > lighter direction.

    I don't typically thin 8mm panels. Why is that so offensive to you when
    you haven't heard my results?


    > Some people I've spoken to who are making these designs and having
    > them come out stiffer than expected are backing off on the
    > downbearing.

    I'm not. Trot these people out and let's talk to them to find out what
    they are really doing. Some people are making really nasty sounding RC
    boards too. If they would discuss it honestly, we could probably learn why.


    > I don't know if that's the right thing to do or not.
    > Some of the problems that we have heard reported on this list
    > (nasally sounding low tenor comes to mind) are a function of too much
    > stiffness, in my opinion.

    The 19% break% in the low tenor scaling has nothing to do with it, I
    guess. How did panel stiffness become your universal fault for all piano
    tonal problems? This never did make sense, and it's getting way out in
    left field here.


    > So my point is that my spreadsheet and the way I use it takes into
    > consideration the features that accompany it. If you change those
    > features you may well have to reconsider the criteria that you use to
    > calculate the rib scale.

    That's how I took it. I certainly know of no spreadsheet that designs
    scales, strings or ribs, at the push of a button, but it does need to
    give you meaningful output.


    > That's all, I wouldn't read anything more
    > into that statement than there is, unless you want to, of course.
    > You may have the last word. I expect you will.

    I have no use for the last word, but I do try to make sense.
    Ron N




  • 86.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 18:33

    Wow.  Persecution complex.  There is help.  

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 87.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-21-2016 19:12
    Would you rather I didn't give reasons for what I do? Would you rather I
    hadn't spent all that private time with you explaining things and trying
    to help you get started with this stuff as Del did with me? I don't
    regret doing it, but I sure don't understand how you came to this in the
    process. Keep a stiff upper lip, but not too stiff.
    Ron N




  • 88.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 23:03

    I don't know what you are talking about. I made no criticisms of anything of yours. Yes you and Del did introduce me to many of these redesign concepts and for that I am appreciative. I've abandoned most of them if the truth be told because for my tonal sensibilities I didn't  find an improvement. It was just different, which I have no quarrel with if that's what you like. We all make our choices. There are also some others that I owe much to for my continuing education in this subject.  The tone of this conversation, however, prevents me from dragging them into this out of courtesy. And there's a heck of a lot of my own work too and a willingness to accept when something didn't work even if it meant doing it over.  That requires something I don't see here too often. The ability to stop believing your own bullshit.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 89.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 14:24
    Must just be a coincidence then.

    It hasn't made any difference so far, but I'll point out once again that
    my bullshit came about by a lot of hours and years trying various
    approaches and testing a lot of things like you did. My sensibilities
    must just be different.
    Ron N




  • 90.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 17:26

    "My sensibilities must just be different."

    And it would be best if we agreed to disagree on that rather than get into the snark and accept that different designs will yield different results.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 91.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 17:53
    It's true. My sensibilities are obviously different from yours, or these
    exchanges would never take place.
    Ron N




  • 92.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 18:09

    I think the exchanges have more to do with style.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 93.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 18:21
    I prefer content, when it's available and accepted. That's a doomed
    debate too.
    Ron N




  • 94.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 18:45

    Nossaman, ad hominem, ad nauseum, ad naseum... 

    Thank you, Ron, for telling us every day how terrible we are.  

    Will Truitt

    ------------------------------
    William Truitt
    Bridgewater NH
    603-744-2277



  • 95.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 19:52

    I do wish these discussions could be less toxic.  Who knows, might be me. Time to check out for awhile. 

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 96.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-20-2016 09:14

    Much gratitude for the many thoughtful responses. Thank you Mr. Nossaman, I've seen the same book referenced by Mr. Gravagne in other discussions and should have my copy forthwith. I still don't think I fully understand the difference between an RC board and an RCS board.  It seems to be that the RCS board tries to avoid any compressive stress at all where the RC board relies at least in part on crown augmentation through rehydration.  Thank you Mr. Love for that insight into your design process. I'm not a scientist but I do know quite a few of them and I guess I'll have to see if I can get one or two of them to help me get up to speed.  Thank you also to Mr.Chernobieff for pointing out that there is a range of available figures for MOE in a particular species of wood.  

    I build CC boards at sea level in a sub tropical climate. I've modified  my process to try and fit the target environment.  Trying to do what makes sense locally makes this sort of discussion all the more valuable as I search for ways to improve.

    ------------------------------
    Karl Roeder
    Pompano Beach FL



  • 97.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-20-2016 13:33
    > Much gratitude for the many thoughtful responses. Thank you Mr.
    > Nossaman, I've seen the same book referenced by Mr. Gravagne in other
    > discussions and should have my copy forthwith.

    Another good resource is Hoadley's Understanding Wood. Together, these
    are your big book of soundboard design. You need to start with the
    structural qualities of the material first to understand what determines
    the board's life and performance.


    > I still don't think I
    > fully understand the difference between an RC board and an RCS board.
    > It seems to be that the RCS board tries to avoid any compressive
    > stress at all where the RC board relies at least in part on crown
    > augmentation through rehydration.

    That's it. There will be some compression in an RC&S panel, naturally,
    but not at the destructive levels of CC construction. The books will
    explain that compressing wood over about 1% of it's dimension at
    equilibrium moisture (whatever that may be) will permanently damage it
    so it will never again reach that original dimension at that EMC.
    Hoadley gives you a shrinkage formula to roughly determine the
    appropriate numbers to anticipate this. You'll find that drying a panel
    from, say, 12%MC down to 4%-4.5% for ribbing makes the panel cross grain
    dimension significantly less than 99% of it's dimension at 12%MC. When
    it rehydrates with the ribs glued on, the panel is compressed beyond
    it's structural limit. Then the board is installed and hundreds of
    pounds of string bearing is loaded on it, crushing it further. Don't
    "believe" anything ANYONE tells you about it. Read the results of the
    people who did real tests in real labs over many years with real
    scientific method and accurate measuring means. Then decide for yourself
    what is what. That's what I did.


    > Thank you Mr. Love for that
    > insight into your design process. I'm not a scientist but I do know
    > quite a few of them and I guess I'll have to see if I can get one or
    > two of them to help me get up to speed. Thank you also to
    > Mr.Chernobieff for pointing out that there is a range of available
    > figures for MOE in a particular species of wood.

    There is, which is why I, personally, like RC&S construction. I laminate
    ribs to average the vagaries of the material so I get a more nearly
    uniform rib stock. Since I'm not relying on the panel for anything but
    moving air, weight is my primary concern there. All this minimizes the
    differences form one piece of wood to another, and makes the whole thing
    much more dependable and predictable. With rib support (RC and RC&S),
    you could tailor the stiffness of the board from bass to treble, rather
    than take what the panel compression gives you. You can reinforce the
    killer octave and treble with stiffer ribs and leave the bass flexible
    enough to actually hear some fundamental. Imagine that.

    >
    > I build CC boards at sea level in a sub tropical climate. I've
    > modified my process to try and fit the target environment. Trying
    > to do what makes sense locally makes this sort of discussion all the
    > more valuable as I search for ways to improve.

    Where you are, you likely aren't having trouble with CC boards. It's
    those of us who deal with boards in hostile environments that have had
    to look deeper into it.
    Ron N




  • 98.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 10:23

    I have played and heard several rebuilt pianos with all of the various "Innovations" listed in many of the above posts. The sound of all the examples I played was really bad!

    Why would any piano rebuilder with proper musical sense ever want to explore adopting what they experience as failure?

    Cures for a dead treble octave of a Steinway should not include making all of the piano dead so treble weakness no longer stands out.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 99.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 20:19

    Mr. McMorrow: Interesting! Lively guitars seem to be on the verge of self- destruction. You make a similar case for the necessary danger of CC boards for some/ all pianos.

    ------------------------------
    Paul Klaus



  • 100.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 22:18

    There is such a body of posting on this forum using beam modeling for ribs in soundboard construction, yet I have seen none of the advocates for this protocol calculate the effect of the beam stiffness of the bridge. In my experience this is such a glaring weakness to make the whole calculation exercise junk. 

    Plus none of the modeling includes what will happen to piano tone color across the dynamic range and decay range. These are the qualities that fine tone is comprised of so any modeling must include how to create the conditions for their existence.

    Those that assume the standard range of soundboard specifications one sees in Steinway or Mason & Hamlin pianos for example, contain some horrible engineering have much explaining to do by example. I have heard and played pianos that have the bellies redesigned and none so far have passed my musical tests. I will stop my criticism when I hear the proof.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 101.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-21-2016 23:10

    It would be an invaluable study to compare the factory boards with the so-called" improved" board innovations that degraded the sound quality you mention. Factories have a huge advantage in making a model in mass numbers, allowing refinements to be made and assessed.  I was a little shocked when David came back so quickly with a total redesign. Most of such ideas were tried and rejected a 100 yeas ago by many famous builders.
    I prefer to work with a design, try to understand their thinking process, and use today's technology as a tool.
    Just another tool in the toolbox, not an end in itself.

    On Apr 21, 2016 10:18 PM, "Edward McMorrow via Piano Technicians Guild" <Mail@connectedcommunity.org> wrote:
    There is such a body of posting on this forum using beam modeling for ribs in soundboard construction, yet I have seen none of the advocates for... -posted to the "Pianotech" community
    Please do not forward this message due to Auto Login.

    Pianotech

      Post New Message
    Re: A Weber Semi-Concert Grand Piano Analysis
    Reply to Group Reply to Sender
    Apr 21, 2016 10:18 PM
    Edward McMorrow

    There is such a body of posting on this forum using beam modeling for ribs in soundboard construction, yet I have seen none of the advocates for this protocol calculate the effect of the beam stiffness of the bridge. In my experience this is such a glaring weakness to make the whole calculation exercise junk. 

    Plus none of the modeling includes what will happen to piano tone color across the dynamic range and decay range. These are the qualities that fine tone is comprised of so any modeling must include how to create the conditions for their existence.

    Those that assume the standard range of soundboard specifications one sees in Steinway or Mason & Hamlin pianos for example, contain some horrible engineering have much explaining to do by example. I have heard and played pianos that have the bellies redesigned and none so far have passed my musical tests. I will stop my criticism when I hear the proof.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------
      Reply to Group Online   View Thread   Recommend   Forward  




     
    To change your subscriptions, go to My Subscriptions. To unsubscribe from this community discussion, go to Unsubscribe.



    Original Message------

    There is such a body of posting on this forum using beam modeling for ribs in soundboard construction, yet I have seen none of the advocates for this protocol calculate the effect of the beam stiffness of the bridge. In my experience this is such a glaring weakness to make the whole calculation exercise junk. 

    Plus none of the modeling includes what will happen to piano tone color across the dynamic range and decay range. These are the qualities that fine tone is comprised of so any modeling must include how to create the conditions for their existence.

    Those that assume the standard range of soundboard specifications one sees in Steinway or Mason & Hamlin pianos for example, contain some horrible engineering have much explaining to do by example. I have heard and played pianos that have the bellies redesigned and none so far have passed my musical tests. I will stop my criticism when I hear the proof.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------


  • 102.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 23:18

    I agree that there are a host of other considerations. But you still have to run numbers on the ribs and you will need some way of quantifying that.  Remember, you're replacing a soundboard presumably because it failed on some level. You can copy what was there but how do you know the factory got it right in the first place.  If you analyze similar models there are variations. Which one was the intended one?. There needs to be some method for analysis. The methods I'm using are not unique even if those using similar methods might come to a slightly different conclusion. And what I posted was hardly the complete analytic picture. I'm not going to give everything away ;-) But It's not a total crapshoot or a bunch of junk.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 103.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 23:31

    I will go further and describe the soundboard quality modeling criteria I think are most applicable.

    The purpose of a soundboard is to couple the wave energy of the strings to each other and the air. It must couple this energy in a way that is musically useful. 

    The soundboard has natural modes. Better sounding pianos have soundboards whose mode density is closer together in frequency than it is in poorer sounding pianos. Having a lower fundamental mode, and closer together modes seem to be present in what is judged to be a good piano soundboard compared to a less musically useful piano.

    The crowned soundboard is a sort of disabled dome. The edges are reduced in strength which would never be done to a domed roof for example. Using a two dimensional beam model to describe loading forces in a domed structure is absurd.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 104.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 23:38

    OK so then how do you choose the dimensions of your ribs?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 105.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-21-2016 23:42

    Assuming the original designer believed exactly the way you do. Doesn't studying a soundboards design teach us how they accomplished their goals?






  • 106.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-21-2016 23:44

    If you're replacing  the soundboard what did they accomplish?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 107.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 00:18

    Btw you also proposed changes to the original rib scale. That's where this all started. So you're being a bit hypocritical. For the record, what i suggested was not  a redesign it was a set of rib calculations. The "redesigns" being referred to are more about a host of added features. Every soundboard builder examines the rib scale if they are being thorough. They may decide not to make changes but they do so with purpose.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 108.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 00:28

    This was a duplicate posting for some reason which I've now deleted



  • 109.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 00:21

    My belly procedure attempts to duplicate what I understand to have been the general procedures used in the belly department of Steinway NY. 

    The principles are that down bearing must not exceed crown. My ribs are not arched any more than the slight vagaries of mill working produce and are oriented so that any natural curve is in the direction of crown. I usually duplicate the rib widths original to the board. When the ribs are glued on they are all too tall and of the same thickness. The final rib heights are reached by planning them down after gluing to the board. As you plane the ribs down the board crowns up more. As I get close to the original rib thickness I inspect how the arch is developing. In general you want a sort of "level" plane across the rib bottoms although it curves along the bridge some. I will tweak the final rib dimensions by a millimeter or so to smooth this level out a little. So the final rib heights may vary some from the original. I want a smooth arch. 

    The arching of the bridge at the gluing surface is of paramount import. Many bridges are not arched enough to properly match the natural arch of the rib/board combination so the board has similar crown across the bridge and along it.

    Then when I set bearing I do it so there is maximum down bearing in the middle of the long bridge and it tapers off towards the ends. I believe many pianos have too much down bearing in the top treble and lowest bass and this forces the whole board into a sort of "warped" arch which raises the fundamental mode of the board and decreases mode density. But I don't have any measurements to prove this beyond ear testing with drum and tap tones.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 110.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 00:41

    I see, so your method is based on achieving a certain amount of crown and along with that a relatively smooth transition in rib heights. 

    So depending on the compression strength of the panel (and I hope we agree that they do vary) your rib heights will vary accordingly?

    Doesn't that mean that a panel with less compression strength, i.e., less capacity to bend the ribs and, presumably, to hold crown, would have less rib support? In other words, with less panel compression you would have to reduce the rib heights more in order that the panel could bend them. Does that concern you?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 111.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 01:03

    Having soundboard panels that are as perfectly quarter sawn as possible I believe provides for adequate safety margin as regards panel compression variance. They sure seem to last longer when stressed if you examine failed boards.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 112.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 01:06

    Rib heights would probably be a little less in a less compressed panel. But remember down bearing is never exceeds crown.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 113.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 08:58

    Ed M

    My own fully loaded experiments with the bridge agree with this statement. 

    We tend to think of the bridge as if it is a beam like a joist, ie a beam which, because of its h x w dimensions is capable of supporting a load bearing span in a roughly linear fashion between two supports. However this linear deflection only descries the behavior of a beam which is mounted in-plane with its length. ie, the ends of the beam and all points in between, draw a straight line from end to end. In this scenario, rotation of the beam under load is minimized. The strength of the beam's section is supporting and flexing in relation to a simple vertical force, and direction of deflection is vertical and its behavior linear.

    The bridge is no such in-plane beam. Yes, it has h x w section like the above in-plane beam, but the length of the beam is so far out of axis, end-to-end, that the section never gets utilized, because the beam rotates around its supports under load. Actually, it can't even support its own weight, unless the ends are clamped. As a linear structure it is useless, unless the rotation forces are fully supported from below (the board/panel).

    As such, I have observed over and over, in both scaled and full scale models that the actual rotation of the bridge, depending on the structure below it, wants to rotates around 2 pivot points: 1 somewhere in the tenor depending on the piano's length, and the other very close to, if not directly under the high treble strut. In this condition, the entire high treble segment of the bridge, cantilevers up not down under load. Repeat...it deflects up under full bridge load. 

    I have, in a recent test, loaded said bridge fully (no plate or strings in the way), fully clamped except for the high treble front end shelf at the belly rail. As anyone who has installed a board might recognize, this high treble front end, needs to be clamped in order for it to brought down to the glue rim. Leaving this area un-clamped, it hangs up in mid air, off the glue rim. The bridge was then fully loaded. This means, in addition to loading the entire lower part of the belly, loading that high treble section with over 250lbs down force assuming 1.5 deg composite bearing. In this loaded condition, the high treble end of the board still was not pressed down to the glue rim, but rather was still hanging in mid-air. Then...and this part cracks me up...by hand...not using a clamp...but by hand...and I ain't any too strong...with light finger clamping force brought that edge of the board down to the glue rim. The applied 250 lbs of down force was not available to push that wimpy length of panel down to the rim.

    Most of the bearing force force in the high treble is transferred, through a point pivoting somewhere near the high treble strut, hyper loading that rib, and transferring force down into the 6th octave. If this is so, one might ask what purpose does this load serve?

    The bridge rotation continues its non-linear behavior in the 4-6th octaves, taking all the transferred loads and rotating into the 4th-6th octave. In an installed system, it may not actually rotate, but the rotational torques imposed on the bridge must be seriously present in relation to what I've just described.  The bridge either has to be fully supported from below to avoid this rotation/torque, or the load has to be reduced...reduced, especially in that high treble area, where its presence, in terms of linear bearing schedules is superflous, and counter indicated.

    The question I have is, what the devil is the point of downbearing?  If support is needed to accommodate  downbearing, the first question to ask is why is downbearing required. Then we need to know how much and how much where. Del has discussed in articles and classes that the board/string system is that of 2 springs in equilibrium, dynamically counterbalancing each other. This model may be applicable...probably applicable, but the necessary level of pre-load I think is assumed to be greatly than actually required to accomplish the equilibrium.  Forces required for that equilibrium state to function seem to be dependent on the stiffness of the panel/ribs structure, but this is complicated by non-linear bridge behavior.

    Maybe downbearing has more to do with termination than pre-loading a spring system...these points are way on the top of my list to play with as my boards get better and better. 

    At a convention a couple of years ago, I was chatting with Del. He asked me at the time what the point of downbearing was. At that time I wasn't ready to take the question on. I'm still not comfortable with a hypothetical answer, but paying close attention to the non-linear behavior of a linearly loaded bridge is part of my thought process in this regard to his simple but not so simple question.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 114.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 11:38

    Greta post Jim!

    I'll use Occam's razor to answer; "What is the purpose of down bearing".

    Done so down bearing never exceed crown places the soundboard string relationship such that the strings are least likely to start pulling the bridge up off the board and strings off the bridge top. A simple engineering safety margin.

    Most new boards react to down bearing pressure in a non linear way. They are easy to compress for the first 1 or 2mm and then it starts to put up much greater resistance to bearing pressure. Old boards that still work well seem to be at that point of higher stiffness immediately, but they also have less crown. So some permanent elastic deformation occurs in the first few years of life. Thus the standards for bearing seem to be more bearing than the initial condition would indicate is needed.

    But then again, maybe using less initial bearing would deform it less? Hard to know.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431



  • 115.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 11:50

    If the board is non-linear (which it is) then downbearing will change the impedance.  So it's not just a simple engineering safety margin or one of connectivity.  It changes how the board performs.  Also, how a spring reacts to inputs in energy will be different if the spring is not compressed, slightly compressed, or bottomed out, the amount of stored energy in the system and the direction of the forces.  All of these things contribute to how the board reacts and the tonal envelope and are impacted by varying the degree of downbearing.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 116.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 12:18

    David,

    Since you mentioned impedance. How do you measure that? And what changes resulted from your measurements?

    ------------------------------
    ChrisChernobieff
    Chernobieff Piano and Harpsichord Mfg.
    Lenoir City TN
    865-986-7720
    chrisppff@gmail.com
    www.facebook.com/ChernobieffPianoandHarpsichordMFG



  • 117.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 12:56

    David L < It changes how the board performs.  Also, how a spring reacts to inputs in energy will be different if the spring is not compressed, slightly compressed, or bottomed out, the amount of stored energy in the system and the direction of the forces.

    OK...lets concentrate up in the high treble temporarily. If, as I contend re my last post, that down bearing in the high treble ends up mostly not in the high treble, what is the impedance effect of high treble bearing, other than increasing the loading of a different part of the board?

    and  Ed

    On the safety margin side...high treble again, 1.5 deg @88 1.5 being a fair amount of bearing, has the top of the bridge higher than than  zero bearing by only a shy .7mm(.026in). That, at a relatively high bearing  situation, is not a lot of safety margin. Pull that composite angle back to .75 deg and the safety margin between zero bearing and design bearing is only .4mm( .016in)...not a hell of a lot of safety margin...let alone hard to hit in laying bearing without adjustable plate bolts or hitches.

    Thoughts?

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 118.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 15:37

    I recall the long piano chord at the end of one Beatles song. Impressed me. Real/studio trick? Ring time and the ratio thereof bass/treble is the main # to quantify/compare if I were into #s on this. Playing piano out of balance is like driving a misaligned vehicle with the steering wheel held askew. For what it is worth. Even boards with negative bearing can sound ok/great at least in some areas to me but they are prone to random rattle.(like my posts) This thread is inspiring for one who has knocked out some boards but not in. Thanks to all!

    ------------------------------
    Paul Klaus



  • 119.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 04-22-2016 17:58

    I'm not sure what you mean by the bearing ending up somewhere else.  If you measure the change in bearing in the lower capo section as you pull the tension in the high treble the lower part of the bridge is clearly moving some along with it. But why would you think that the impedance charateristics aren't changing in the upper bridge at the same time?  .  

    That being said I  can say that I don't set a lot of downbearing in the high treble because I don't think it's that necessary, at least as a method of raising impedance.  The assembly is pretty stiff up there no matter how you slice it.   

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320



  • 120.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 18:28

    <I'm not sure what you mean by the bearing ending up somewhere else

    at least as I have observed in my own tests, as loads are applied to the bridge from tenor up through the 4-6th octaves, the loads lever the unloaded (as yet) high treble up away from the soundboard, pivoting on the rib right under or near the high treble strut. So before loading that high treble, and impedance-wise before the board sees any positive load applied to it, the bridge first has to either pivot on the strut rib, or if restrained, as it is in reality, be placed under significant downward torque. In a highly loaded high treble scenario, the bridge is seriously flexed over that rib. The strut rib takes the load as the bridge is flexed over it or close to it.

    So in order to get from negative downward force applied the panel, the applied loads to the high treble first have to load rib strut, or struts into the 6th octave. Only a small portion of the load applied to the high treble section of the bridge ever makes it to the panel, in my opinion, as evidenced by the test I described earlier. The load instead ends up where you don't want it.

    Which is why I said loading the high treble applies loads, does not load the high treble predominantly. This means loads in the high treble don't effect impedance in the high treble.  

    <That being said I  can say that I don't set a lot of downbearing in the high treble because I don't think it's that necessary, at least as a method of raising impedance. 

    I agree. The argument I'm making above functionally is saying the same thing, I think. Back off the load up there, as it is not necessary, and if anything counter-productive to other, already challenged parts of the scale. Going back to my and Ed's suggestion that straight linear low to high application of loads when setting DB has questionable utility in this part of the high treble scale. 

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 121.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 15:20
      |   view attached
    > The bridge is no such in-plane beam. Yes, it has h x w section like
    > the above in-plane beam, but the length of the beam is so far out of
    > axis, end-to-end, that the section never gets utilized, because the
    > beam rotates around its supports under load. Actually, it can't even
    > support its own weight, unless the ends are clamped. As a linear
    > structure it is useless, unless the rotation forces are fully
    > supported from below (the board/panel).

    I have demonstrated that in classes for some time. I have also
    alternately sat a crowned bridge and a straight bottomed bridge on one
    of my ridiculously high crowned boards, clamped in a piano, and both
    followed the contour of the crown quite well. The only beam support the
    long bridge offers is in the lower third where it is fairly straight,
    and where it is least needed or desired. The bridge does exactly what
    bridges do everywhere, it distributes load. It must be stiff enough to
    do that, particularly in the treble, and it also adds mass, whether we
    consider it beneficial or not.


    > As such, I have observed over and over, in both scaled and full scale
    > models that the actual rotation of the bridge, depending on the
    > structure below it, wants to rotates around 2 pivot points: 1
    > somewhere in the tenor depending on the piano's length, and the other
    > very close to, if not directly under the high treble strut. In this
    > condition, the entire high treble segment of the bridge, cantilevers
    > up not down under load. Repeat...it deflects up under full bridge
    > load.

    Attached is a jpeg I put together back in the days of the old Pianotech
    list. A year or so after I did this, Phil Ford offered to do a FEA
    analysis for me to see if it was real, or imaginary. I have a set of
    graphic files I've used in classes since that shows my dumb ass back
    yard mechanic's approach was pretty close. You're right. In a
    conventional soundboard, the load is in front of the support, and is
    working from the first day of assembly to push the soundboard flat in
    the killer octave area - which just strangely happens to be at the
    extreme of the curve in the bridge's "beam". I put the treble end of the
    support at the extreme end of the bridge. It's sitting about 25mm from
    both the belly rail and the treble rim, and isn't going to deflect a
    lot, Until the rib breaks, it's sitting on a rock. I approached it like
    a curved floating dock with one end sitting on the bank. Floats at each
    rib point provided the appropriate lift, and weights derived from
    downbearing distribution of the string scale provided the weight
    distribution. The extreme curve point would not remain above water. It
    rotated and sank, just like a killer octave. How can a killer octave
    have both concave crown and negative bearing, as we see so often if we
    bother to look? Just like this.


    > Most of the bearing force force in the high treble is transferred,
    > through a point pivoting somewhere near the high treble strut, hyper
    > loading that rib, and transferring force down into the 6th octave. If
    > this is so, one might ask what purpose does this load serve?

    Yes, this is so. My logic and crude analysis suggested that, and Phil's
    FEA run showed that it is so.


    > The question I have is, what the devil is the point of downbearing?
    > If support is needed to accommodate downbearing, the first question
    > to ask is why is downbearing required. Then we need to know how much
    > and how much where. Del has discussed in articles and classes that
    > the board/string system is that of 2 springs in equilibrium,
    > dynamically counterbalancing each other. This model may be
    > applicable...probably applicable, but the necessary level of pre-load
    > I think is assumed to be greatly than actually required to accomplish
    > the equilibrium. Forces required for that equilibrium state to
    > function seem to be dependent on the stiffness of the panel/ribs
    > structure, but this is complicated by non-linear bridge behavior.

    People who have built soundboards with neither crown, nor downbearing
    have answered the questions.

    Ron N




  • 122.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 15:55

    I was posing a bearing the question in general but then followed up specifically regarding the high treble.  So rather than go for a binary, downbearing is good or bad, all or nothing, I wondered why, specifically in the high treble, where most of the bearing is transferred to the killer octave, physically displaced from the high treble, is heavily loading the high treble in particular a good idea. I would characterize 1.5 deg as heavy loading, or heavier loading than I'm starting to experiment with up there.

    This high treble part of the scale, in most pianos, even very fine rebuilds, is often less than stellar. So I think its reasonable, rather than discuss whether bearing is all good or all bad, to focus specifically on the high treble, at least for now. In effect, the high treble functions as if there is little or no bearing anyway, since the load dispersion ends up physically removed from the point of load, hyper loading of the killer octave anyway. It seems like a lose-lose situation..specifically in the high treble...load functionally not participating in high treble performance while squishing the life out of the 6th octave.

    Also, re my response, my original post was responding to Ed's mention of the linear application of downbearing which we often see, ie .3-.5 deg composite db linearly increasing to 1.5 in the high treble not making sense. Rather than a binary discussion of all or nothing, what applied loads maker sense given the tendency of the bridge to non-linearly muck up the linearly applied dispersion.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 123.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 16:07

    Jim, regarding your earlier description. Are you having the same killer octave issues when you have to clamp the bridge to fit the crown shape vs a bridge contour that mates the crown?






  • 124.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 18:36

    <regarding your earlier description. Are you having the same killer octave issues when you have to clamp the bridge to fit the crown shape vs a bridge contour that mates the crown?

    I was discussing forces and distribution of forces Chris...not posing a "how to fix" question. If one can understand how the forces are applied under load, that knowledge is a tool, and a fine tool to share. 

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026



  • 125.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 04-22-2016 17:02
    > This high treble part of the scale, in most pianos, even very fine
    > rebuilds, is often less than stellar. So I think its reasonable,
    > rather than discuss whether bearing is all good or all bad, to focus
    > specifically on the high treble, at least for now.

    I have no intention of ever discussing whether bearing is all good or
    all bad. It's pointless as a general question, pertaining only to one
    narrowly specific detailed instance at a time. If there is an ideal
    bearing schedule, it would have to accommodate all types of soundboard
    construction at once. Good luck on that one.


    > In effect, the
    > high treble functions as if there is little or no bearing anyway,
    > since the load dispersion ends up physically removed from the point
    > of load, hyper loading of the killer octave anyway.

    No, it isn't the load doesn't disappear from the treble. Part of each
    unison load transfers down scale by the leverage of a class 2 lever with
    the high end of the bridge as a fulcrum. The load at each unison stays
    at each unison, but instead of spreading equally out from each direction
    along the bridge as it does in the middle of a straight bridge, it
    concentrates down scale by leverage. So the killer octave has both the
    load placed on it by the string bearing, but additional load from the
    class two lever above it. Like a wheelbarrow. With 100 lbs in the
    bucket, you may measure 25lbs at the handle, but the load in the bucket
    didn't become less and move to the handle. It's leverage. Basic science.


    > It seems like a
    > lose-lose situation..specifically in the high treble...load
    > functionally not participating in high treble performance while
    > squishing the life out of the 6th octave.

    Which is exactly why my answer is to shorten the ribs in the KO some
    with the evil bass cutoff, and size them strong enough to support the
    load. I don't know of a practical way to change the geometry of the
    leverage, but I can accommodate the results with ribbing. This is where
    spring rate comes in. How much a rib deflects per lb (or parsecs per
    grain - whatever scale you like as long as you use it throughout). I use
    that with a beam deflection formula to decide how stiff is stiff. It's
    not the crown, or the percentage of crown left under load that
    determines stiffness and response. It's the spring rate, just as the
    rest of industry uses it to determine spring strength and working range.
    Again, really simple stuff. No mysteries necessary. It's simple
    mechanics. When someone shows me what ideal tone looks like on a
    blueprint, I'm ready see it.

    Ron N




  • 126.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-17-2017 17:51
    David L,
    Here is a redo of the Weber rib scale. With my new parameters of measurement and related factors now complete. I was curious what you think after running it through your spreadsheet.

    Thanks
    -chris
    #caveman

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 127.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-18-2017 10:17
    Hi Chris,

    ever thought about calculating your soundboards with FE (finite elements) software? To my knowledge that is the current standard in the R&D departments of the big players today (Steinway, Yamaha, Fazioli et al). What i miss in your numbers is the length and shape of rib tapering (which has great influence on soundboard stiffness). Attached is a video i did some ten years ago of a soundboard analysis with a FE software (also taking into account of the shape of rib tapering):
    Piano Soundboard
    YouTube remove preview
    Piano Soundboard
    Animation of a virtual grand piano soundboard
    View this on YouTube >


    best regards,

    Bernhard

    ------------------------------
    Bernhard Stopper
    Klavierbaumeister
    Tuebingen
    ------------------------------



  • 128.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-18-2017 11:01
    Hi Bernhard,
    Thanks for commenting. The videos are awesome, but my philosophy is different regarding technology. I use the computer to insure that my rib scale structure exhibits evenness, after that, I rely on my ear and craftsmanship. I want to leave the Matrix so to speak. 
    I don't think stiffness is the goose that lays the golden eggs that everyone else seems to seek with laminated ribs of excessive mass and no structure. Every cheap piano I come across exhibits that quality of excessive stiffness. 
    You said that Steinway, Yamaha are using the software in R&D, but I have yet to see any changes in their rib structure. Still uneven, and proportioned incorrectly. Haven't had the opportunity to measure a Fazioli yet.

    After I have an even rib structure design, I then take each one to the bench and test their flexure for evenness.  I always thought it odd that the scalloping is arbitrarily done with no regard to the placement of where the load is. I preload a rib at the proper location and measure along its length for evenness. 

    After a board is installed I listen to it. I Make necessary adjustments to get a low tone and sustain out of it. My boards sound like timpani on a tap test. Others sound like table tops until the Iron frame is installed. Then they have a high pitch short sustain. 
    It would be interesting to have your software analyze one of my new boards. I bet you would see something different.
    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 129.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-18-2017 12:35
    Hi Chris,

    i guess you would not expect your soundboards to ping like timpani if you would not taper the ribs in the production process, so leaving those measures out of calculations (by spreadsheet or FE program) does not cover the whole picture.

    One of the said manufacturers for example measures each single rib material stiffness characteristics (by measuring the deflection of the rib under a load) and let these parameters go into the calculations and select different ribs accordingly. From measuring dimensions alone it is difficult to classify such a board as not optimal, if one does not know the rib material characteristics for that set.


    ------------------------------
    Bernhard Stopper
    Klavierbaumeister
    Tuebingen
    ------------------------------



  • 130.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-18-2017 20:32
    My own loading tests have really confirmed for me, Berhard's point about the design of the scallop...especially in my last several pre-glue-down board tests. I've always thought that there was a difference between stiffness as a function of rib section, and stiffness, or rather restriction imposed by the rim and the rim's particular shape in that piano. The two factors are hard to separate, as they both affect deflection, in a static test, but I'm working this question. I am, as we speak,  testing, messing with and adjusting boards with this parameter in mind.

    Chris...I'm curious about your fine-tuning the structure after the fact. I have come up with a protocol that allows me to test and fine tune before the board is glued in. So I have complete access for the necessary carpentry.  I have also adjusted the board after the fact in an as-built piano, but its very clumsy to adjust ribs upside down, or sideways with all the rim braces in the way...hard on the knuckles too. I'm curious how you go about doing the modifying carpentry on the rib structure in the as-built board.


    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 131.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-18-2017 22:50
    Jim.
    I may disappoint you a bit here.
    I don't mess with the ribs after installation.
    I get them as precise as I can according to a design make up. My ribs have to fit 12 criterias of measurement. I also run them through a testing procedure. I showed one such test of mine in a previous post entitled "the parabolic rib". My ribs apparently are different than everyone else's. They have a low profile, are rectangular, and are precision machined. I'm watchful with removing any sharp edges, as that creates internal "noise."  I also have a tone test, which is basically a great matching density test. I learned about that test from a baseball bat mfg.
    The scalloping is more important than i first thought, and I am very careful to make sure that if the load is offset then the scalloping on the long side gets adjusted for evenness to within one thousandth of an inch on each side. I don't think that was done in the past, judging from several boards i've studied from well known makers.

    After installation, I am more focused on what happens above, panel grading etc., you know the drill. I make sure there are no sharp corners on the bridges. Once you hear that noise a sharp edge makes you never forget it.

    The procedures i follow results from wanting a certain type of sound that I like. Depth, clarity, and projection. Deep basses that aren't muddy.
    Tone that sounds "normal at the keyboard" but roars like a lion on the other side of the room. 
    After all, i want to be heard back there.
    -chris



    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 132.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 12-19-2017 05:44
    Chris, could you elaborate more on the scalloping?  It is not clear to me exactly what you are talking about when you say, "if the load is offset then the scalloping on the long side gets adjusted for evenness to within one thousandth of an inch on each side."  Are we talking the length of the scallop, its thickness, its relationship to the scallop of the short side, or to it's neighbors?  Or something else?  

    Please elaborate in detail.  

    Also, more on the tonal effect of the sharp edges on the ribs and bridge. Thanks. 

    Will Truitt


    ------------------------------
    William Truitt
    Bridgewater NH
    603-744-2277
    ------------------------------



  • 133.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-19-2017 06:45
    I was referring to a flexure test I do.


    If the load is in the center. Both sides (same length) should flex evenly. When the load is off set, a short side and long side is created. The long side has to be trimmed to regain an even flex.

    Regarding the other question of describing a tonal effect in detail. "Removing a ping" is the best i can do. 
    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 134.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-19-2017 06:52
    Here's an interesting video on making drumsticks .

    It Illustrates many similar selection and grading processes when it comes to using wood. The bandsaw split test (internal tension) and tone pairing test i thought were fascinating.
    https://www.youtube.com/watch?v=6uOqB5hoiqE

    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 135.  RE: A Weber Semi-Concert Grand Piano Analysis

    Registered Piano Technician
    Posted 12-19-2017 08:18
    Thanks, Chris;

    Should I take this to mean that, rather than having ribstock in the fixture that has not yet been scalloped, you instead clamp the rib at the ends  at the length they would be in the piano, having already scalloped them in more or less the layout and thickness you desire.  Then you remove material from one side of the rib or the other, until your dial gauge readings are equal.  Further, you have placed the weight on top of the fixture along the length of the rib so as to reproduce the location of the bridge.  

    Am I correct?

    Will

    ------------------------------
    William Truitt
    Bridgewater NH
    603-744-2277
    ------------------------------



  • 136.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-19-2017 09:20
    Thanks for your reply Chris.

    Functionally, I don't see how its possible to empirically test a scalloped rib, as the scallop, if thinned at the rim junction, without support from the panel/rim interface will flex in an misleading fashion. I suppose a simple strip of crossgrain spruce glued to the top of the rib might try to mimick the varying curves of the rim intersection, but the effect of all of the real estate along the perimeter of the rim will change the flexture profile an unknown amount. 

    I agree with your empirical testing of the designed idea. In my own thinking, the composite is more than the sum of its parts. Ie, the panel adds complexity to the thinking and the measurement...and this is specifically why I came up with a way to test the entire composite structure. It by-passes differences of natural materials, by-passes the relatively unknown actual mc of that particular board at ribbing on that particular day in that particular season of the year, by-passes effects of the panel grain orientation-to-rib orientation, by-passes, effects of the shape of the rim glue intersection, bypasses the first attempt at scalloping and rib height, etc. The goal, to test the structure for some of the parameters you mention, seeing it though in its composite whole.

    Also, the education this provides as to what the composite structure is doing floors me in the amount of data each subsequent belly provides...really quite interesting.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 137.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-20-2017 12:28
    Jim,

    What you said here is technically true.

    "Functionally, I don't see how its possible to empirically test a scalloped rib, as the scallop, if thinned at the rim junction, without support from the panel/rim interface will flex in an misleading fashion. I suppose a simple strip of crossgrain spruce glued to the top of the rib might try to mimick the varying curves of the rim intersection, but the effect of all of the real estate along the perimeter of the rim will change the flexture profile an unknown amount".

    As you would probably guess, I have tried various set ups, Including with a panel glued onto a rib. Then altering the scallop to see the effects. The end result was basically the same  Minute differences of course, but not enough to make me think that checking a rib apart from the structure was invalid. 
    I look at it this way, I want the individual parts to be of high quality first, then work with them as a composite structure second.  
    We are probably just splitting hairs here.
    Plus Jim, I want to thank you for posting the picture of the "trolley/dial on a beam" tool. I made one and absolutely love it. Thanks

    Bernhard,
    I'm still pondering the "not the complete picture" thing. I can't get around the fact that pianos can be built without having a complete picture, as was done since the beginning. So I don't understand how having an extra tool that they in the past didn't have, to look and fine tune the details, is incomplete. Does that matter?
    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 138.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-23-2017 18:21
    Bernard said:
    From measuring dimensions alone it is difficult to classify such a board as not optimal, if one does not know the rib material characteristics for that set.

    Thought about this for awhile.............
    So what are rebuilders out there armed with just a micrometer (90%) doing to all those soundboards??
    Let that sink in.
    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 139.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-23-2017 19:09
    here's an interesting one...

    I'm in the process of doing a series of loaded deflection tests on a new S&S A board. Attached is a graph showing two subsequent tests. Both clamped and loaded identically. The only difference was the shape used to cut the scallop, scallops centering (mostly, reasonably close on some on the long bridge. 3rd deflection graph, scallops not centered as closely as the 4th deflection test. 3rd graph, scallops an abrupt radius coming off the full section, 4th graph a more gradual tapered cut. 

    Overall deflection very little change globally...its all in the smoothing of the rib to rib deflection
    I may remove a little rib height on 7 and 8...not sure

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 140.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-23-2017 21:46
    Jim,
    Yes interesting, I have been saying that the rib to rib relationship is very important for 2 years now. Since you've added 3 ribs to the A, I have nothing to compare to tho. 
    It would have been nicer, perhaps, to have individual pre- rib deflection charts, and then see how they behave after glued to the panel as a composite. That's my next step anyways which would verify my idea of the validity of individual testing first.  
    I am also going to be working on an A in a couple of months. I only have one scale so far in my database. Would you care to share the Height, Width and Length of the the original A you have? Thanks

    Curious on how you go about deciding on how many ribs to add.
    Do tell.
    -chris


    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 141.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-23-2017 22:03
    Here was an individual test that I thought was interesting.
    Picture 1) Even scallop, weight placed in center.
    Picture 2) Same rib, same scallop, same weight just placed off center. Notice the deflection curve is different.
    Picture 3) Same rib, same weight. But now I altered (lengthened) the scallop (on the long side) until there was a parabolic curve again. If i remember correctly the scallop ended up being about 2 inches longer on the long side in this particular case.





    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 142.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-23-2017 23:43
    Its an A1...there's a couple of different flavor A's   serial num 108786. Original ribs attached.  The numbers on the previous graph were deflection points along the bridge. Most were at rib locations, but 15 was at note 88... its not a rib...just a deflection point. ​​ 

    As far as the number of ribs, since a very successful job I did a couple of years ago, I have been refining a rather radical rib array, where ribs in the middle of the board are placed closer together and drastically reduced in width...15, 12,11,10mm. This lightens up the board significantly, as I have found that the closer spacing of the ribs increases the stiffness in a greater than arithmetic fashion. It also allows less mass to achieve the required stiffness. The last board was a full lb lighter than the original.

    The tonal profile I am shooting for is, as I have mentioned before, exceptional pitch clarity, and voice-like sustain...so what I am successfully playing with, are parameters that help me create and control that tonal palette.  However, cutting unfamiliar territory requires one have some way to quantify how the unfamiliar components behave in the structure, before the whole shebang gets glued in. I am in the process job by job, backing off rib heights in the whole system.  As far as how many each board gets, that's where seat of the pants comes in...I lay it out look at it, sleep on it and then go for it.  But then, I test the system and refine it until I know it will work the way I want it to.

        


    ​​

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 143.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-24-2017 12:05
    Jim,
    Thanks for the data. It was interesting to see the same scale with different details. Yours was the first Steinway I have seen that (imo) had the correct overall mass (Area 8.8 sq in. Volume per unit length .75 cubic in.)  Most that i have checked are below (Area 8.7 sq.in. Volume per unit length .73 cubic in).

     Your unique rib structure is sure thinking out of the box!   The real question you pose is whether added stiffness= increased sustain.  I am of the opinion that the opposite is true. I have demonstrated with my "Vibrating Rib" demo that more flexibility and increasing the mass increases the sustain. The reason/theory is because with the identical input of energy- in a stiff/light board the energy is used quickly, in a flexible/heavy board the energy takes longer to dissipate.  With my demo you can see it the change in behaviour by using different weights. If i'm wrong somehow, i'd sure like to know what i'm missing.

    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 144.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 12-24-2017 12:20
    BTW, This would be my scale for the SSA. FWIW  Volume per unit length .75 cu. in and smooth modulus curve. Volume in parallel proportion to length curve. 
    -chris


    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 145.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 02-13-2018 16:31
    The original rib scalloping layout was based on a consistent distance from the edge and imitating that on every rib. 4" in this case. Unfortunately, this makes each rib flex in an asymmetrical fashion. Since i want each rib to flex  parabolically, I layed out with tape, taking the distance of the shortest side of the rib and transferring it to the long side of the rib. The result was a little surprising. A teardrop shape formed. Interesting.

    -chris
    #caveman



    ​​

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 146.  RE: A Weber Semi-Concert Grand Piano Analysis

    Posted 10-09-2023 14:14
      |   view attached

    So I have been working on a new tool for my rib scaling software and just completed it a couple days a go. It allows me to measure the tonal power of a soundboard. I input several key data points of each board from my database  and then compare pianos. For reference i created what i call a SAD scale. A Steinway S, A, and a D for low medium and high output ( all in cubic inches). There were a few surprises. The Steinway won my survey beating out a Baldwin SD6. Mr. Loves re-scale of my Weber reduced its power by a little, only making a 6" smaller piano. To be fair, my re-scale could not improve and only mounted as a  a reconfiguration of mass. All of the rib crowned boards i found did in fact reduce the power output, often making the piano equivalent to being a smaller grand. Also the D beat my Mammoth VCG, but i was close.

    Maybe next time,

    -chris



    ------------------------------
    Chernobieff Piano Restorations
    All the elements are known, and yet no combination there of creates life. Yet we are here.
    865-986-7720 (text only please)
    ------------------------------