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The soundboard pushing the rim out question

  • 1.  The soundboard pushing the rim out question

    Posted 02-09-2019 22:39
    I've been pondering this question for awhile now. First, i'm on one side of the debate, then i'm on the other side.  Intuitively, it makes sense that the soundboard (with a crown) pushes out on the rim when it's under load. Then Nossaman comes in and says that his experiments showed that the soundboard actually rotates inward at the rim.  Which also can be demonstrated. Hence the back and forth.
    Regardless on which side of the debate you're on, here's an interesting video showing the rim moving and affecting crown.

    Mason & Hamlin Resonator
    YouTube remove preview
    Mason & Hamlin Resonator
    Mason & Hamlin Centripetal Tension Resonator as found in an early Model A.
    View this on YouTube >


    ------------------------------
    Troubles are Bubbles, and they just float away.
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Knoxville, TN
    865-986-7720
    ------------------------------


  • 2.  RE: The soundboard pushing the rim out question

    Member
    Posted 02-09-2019 23:51
    Those are two different scenarios:  Nossaman was talking about the panel changes as a result of down bearing, given a stable perimeter dimension. Craig Hair was talking about the effect of reducing the rim perimeter dimension, not the effect of downbearing on the panel.

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



  • 3.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-10-2019 10:42
    Ron Nossamn's point (one of many) was that increasing the downbearing makes the ends of the soundboard want to lift off the inside of the rim while bearing down on the outside of the rim. To illustrate that effect I put in Pianos Inside Out a photo of a piece of orange peel that's increasingly loaded in the middle. It looks like a dancer standing with feel far part and then lifting the heels (and remaining on toes).

    ------------------------------
    Mario Igrec, RPT
    http://www.pianosinsideout.com
    ------------------------------



  • 4.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-10-2019 13:27
    Many years ago Chris Robinson made a statement in one of his classes to the effect of: "If the rim expands .001" the soundboard will lose its crown...do the math".  I did not "believe" him at the time, feeling that he was exaggerating, but I was not going to argue the matter either since I had no opposing data to draw on.

    Some time later, I presented the matter to a client who was also a math professor. I explained the issue and gave dimensions, etc and asked: "How do we go about figuring this out mathematically?"  Well, he got real excited and said: "Ahhh, practical application of math...I love it!" and then proceeded to start drawing right triangles (and other stuff) and explaining what he was doing (though it was largely over my head).  But, when solved for "x", the answer was in fact: .001" - .002" rim expansion to lose about 1/8" - 3/16" crown over approx 36" span.

    So mathematically this works out to be true. HOWEVER, since then I have been exposed to the thinking that this IN FACT does not happen...that the rim can expand and the soundboard will not lose its crown because of that. RN being (I think) a big proponent of this thinking.

    So...what are the facts?

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 5.  RE: The soundboard pushing the rim out question

    Member
    Posted 02-10-2019 16:11
    what's RN?

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



  • 6.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-10-2019 16:44
    Ron N. 






  • 7.  RE: The soundboard pushing the rim out question

    Member
    Posted 02-10-2019 18:16
    ahh..thx.

    Re the expansion question, if it did expand, as shown in Craig Hair's demonstration, expansion would not be uniform, because of the shapes involved. One part would expand, but that expansion would reduce other areas in a push-me-pull-you scenario. Its too easy in all of this visualizing of what might be happening, to reduce a serpentine, looped structure from three interactive dimensions to a simple linear two dimensional 1+1 model. Why...because its much simple and easier to think linearly and in two dimensions. But I think there are, unfortunately, way more variables involved, which of course makes it harder to think about.

    One thing I do know, from observing my boards as I test load and measure them with indicators, is that the effect the perimeter glue joint has on overall and local stiffness of the structure is huge. Its huge, and I missed it for a long time. Missed it, because I visually simplified the system to conform to the limitations of what I could imagine was happening.

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



  • 8.  RE: The soundboard pushing the rim out question

    Posted 02-11-2019 00:21
    Jim Said,
    "One thing I do know, from observing my boards as I test load and measure them with indicators, is that the effect the perimeter glue joint has on overall and local stiffness of the structure is huge. Its huge, and I missed it for a long time. Missed it, because I visually simplified the system to conform to the limitations of what I could imagine was happening."

    A good little demo of this is to use a paint stick. Hold one end in your hand and flick it. You'll get nothing. Clamp one end in a vice, flick it, and it behaves totally different.
    -chris

    ------------------------------
    Troubles are Bubbles, and they just float away.
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Knoxville, TN
    865-986-7720
    ------------------------------



  • 9.  RE: The soundboard pushing the rim out question

    Posted 02-11-2019 13:08
    JIM Said,
    " Nossaman was talking about the panel changes as a result of down bearing, given a stable perimeter dimension."

    But that doesn't even attempt to answer the question if acting forces expand the rim or not.


    Here's a Ron Quote in answer to the question

    "From Buttressed Arch question for Ron
    Question 11 

    >IS there a force

    > pushing the rim out,

     Ron,

    No, there is not. There is some rotational force on the belly

    rail from string downbearing because it's cantilevered, but it

    has no affect on crown".

    Doesn't the  Craig Hair video show that a force does push out on the rim. If the rim is being changed and the ribs go up and down, doesn't that show a connection between the two?
    -chris







    ------------------------------
    Troubles are Bubbles, and they just float away.
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Knoxville, TN
    865-986-7720
    ------------------------------



  • 10.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-11-2019 20:36
    In the video, Craig cut some bars such that they were arched into a tight fit in the notches in the rim.
    A soundboard, compression or rib crowned, is arched by its internal structure before it is glued into the piano.
    Think more like a dinner plate which is inverted and glued by its rim.
    This image leads me to think that the purpose of the M & H spider is to stiffen the rim before the soundboard is glued in, not to somehow increase the crown or "tune" the soundboard.
    Having seen one or two M & H's with "shredded" soundboards, I wonder if this was caused by someone tightening the turnbuckles.

    ------------------------------
    Ed Sutton
    ed440@me.com
    (980) 254-7413
    ------------------------------



  • 11.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-11-2019 22:44
    I think the Tension Resonator is a bracing system named very cleverly.

    Traditionaly, M&H has used an inner/outer rim construction. The fully strung and at tension inner rim belly is glued to the outer rim. So one desires that the dimension of the inner rim stay constant with fluctuating humidity.

    Voila, restrain wood movement by holding everything from expanding with the centripetal forces collected by an unmovable element.

    I am afraid Mr. Hairs' video will encourage more people to add tension to the spider. It is very easy to crack the rim and belly rail apart from doing this. I have seen several M&H's where this has happened.

    My practice when installing a new soundboard is to make sure the spider is properly tight, by ear and fist bump, and don't change it again; then glue the new board in.

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



  • 12.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-12-2019 11:12
    To both Eds:
    Since the tension resonator was mentioned this brings up questions that I have about tightening one. I have been dealing with a vibration in a 25-year old Mason & Hamlin in which the resonator seems to be vibrating sympathetically with notes in the midrange. If I hold it while the note is played the noise stops. It is a very subtle mouse but there, nonetheless.

    My questions have to do with how careful I need to be about tightening the vibrating member. Can this be done with the piano under full tension? Should I go around to all three and add a little tension all the way around or just to the one that seems to be generating the noise?  How do I know if I've gone too far? I don't want to wait until the rim cracks to get my answer to that question!

    Thanks for any advice,
    ~ jeannie

    ------------------------------
    Jeannie Grassi, RPT
    Bainbridge Island, WA
    206-842-3721
    ------------------------------



  • 13.  RE: The soundboard pushing the rim out question

    Posted 02-12-2019 13:46
    Hi, Jeannie,

    Basically, I'm with both Eds on this.

    In terms of tightening one, I'm particularly with EdM. If one has the
    luxury of being able to work on the resonator when the tension is off,
    that's great! And, EdM's account describes what has worked well for me,
    as well.

    If one does not have that luxury, then one's choices are more limited.
    With both Eds, I've seen far too many rims and boards destroyed by folks
    who somehow think that the resonator was installed to "adjust"
    bearing/crown/&c. It isn't; as described, it's there to help keep
    things in balance.

    In terms of the specific instance you describe, your choices are
    obviously much more limited; and there isn't much to be done except to
    work to eliminate the buzz (Surprise! The presenting issue!)

    So, attempting to describe an approach which might work:

    - Yes, this can, within limits, be adjusted while the instrument is
    under tension.

    - While I suspect that you have already done so, I would check to see
    what, besides the resonator, might be loose. (Yes, I know...but, since
    you're already under the piano...)

    - Without seeing the instrument, while I would check all of the
    members, I would start with the one which appears to be causing the
    problem. Remembering that the strut is actually a turnbuckle (and,
    you'll have to loosen the threaded nuts anyway), check to see if the
    nuts are already loose. If not, loosen them a bit; and carefully check
    to see if there is any change in the tone/pitch/volume of the buzz.
    This might provide guidance as to how much tightening might be
    necessary. If there's not change, go ahead and carefully tighten the
    turnbuckle while constantly checking for changes in pitch/tone/volume of
    the buzz. Any change will serve to help indicate if you're going in the
    "right" direction. Once the buzz appears to stop, give a slight
    additional tightening to the turnbuckle (remembering all those split
    rims/&c)...double check the (hopefully lack of) sound. Then, tighten
    the retaining nuts (remembering that you're not cinching down head-bolts
    on a Caterpillar 3208 diesel engine). Double-check your work...again...

    - Once you're done with the above, you're not really done. Go back
    through all the members of the tension resonator again. Check for any
    kind of new/different noise; and repeat the above as may be necessary.
    While it isn't always necessary to change anything else; it is necessary
    to carefully check the work.

    Two additional important points:

    - Knowing that you know this already, it's important to keep in mind
    that, as with "adjusting" the "bell" on an S&S, screwing around with the
    tension resonator on an M&H (or Mason & Risch, if you happen to see any
    of those) is fraught with the potential for disaster...if not today,
    then, perhaps at some point in the future; and,

    - Unlike many aspects of piano work, this really isn't rocket science
    insofar as it can realistically be reductively analyzed to death.
    Rather, this kind of thing is something with which one works (sometimes
    for years) before becoming proficient at it in any real sense. That is,
    this is one place in which it helps to have done a fair amount of belly
    work (or, for that matter, have done more than a few thousand tunings).

    Or, put another way, while it makes (some) sense to be terminally OCD
    about certain aspects of this work, for certain (perhaps many) others,
    one has to learn when to let go of relying on mere numbers; and deal
    with the art they attempt to represent. From that standpoint, we're not
    talking about an "either/or" situation. What we are talking about is
    (yet another) "both/and".

    Hope that this is somewhat helpful. If not, use the delete button.

    Kind regards.

    Horace

    On 2/12/2019 8:11 AM, Jeannie Grassi via Piano Technicians Guild wrote:
    > Please do not forward this message due to Auto Login.
    >
    > To both Eds:
    > Since the tension resonator was mentioned this brings up questions that I have about tightening one. I have been dealing with a vibration in a 25-year old Mason & Hamlin in which the resonator seems to be vibrating sympathetically with notes in the midrange. If I hold it while the note is played the noise stops. It is a very subtle mouse but there, nonetheless.
    >
    > My questions have to do with how careful I need to be about tightening the vibrating member. Can this be done with the piano under full tension? Should I go around to all three and add a little tension all the way around or just to the one that seems to be generating the noise? ??How do I know if I've gone too far? I don't want to wait until the rim cracks to get my answer to that question!
    >
    > Thanks for any advice,
    > ~ jeannie
    >
    > ------------------------------
    > Jeannie Grassi, RPT
    > Bainbridge Island, WA
    > 206-842-3721
    > ------------------------------
    > -------------------------------------------
    > Original Message:
    > Sent: 02-11-2019 22:44
    > From: Edward McMorrow
    > Subject: The soundboard pushing the rim out question
    >
    > I think the Tension Resonator is a bracing system named very cleverly.
    >
    > Traditionaly, M&H has used an inner/outer rim construction. The fully strung and at tension inner rim belly is glued to the outer rim. So one desires that the dimension of the inner rim stay constant with fluctuating humidity.
    >
    > Voila, restrain wood movement by holding everything from expanding with the centripetal forces collected by an unmovable element.
    >
    > I am afraid Mr. Hairs' video will encourage more people to add tension to the spider. It is very easy to crack the rim and belly rail apart from doing this. I have seen several M&H's where this has happened.
    >
    > My practice when installing a new soundboard is to make sure the spider is properly tight, by ear and fist bump, and don't change it again; then glue the new board in.
    >
    > ------------------------------
    > Edward McMorrow
    > Edmonds WA
    > 425-299-3431
    > ------------------------------
    >
    > Original Message:
    > Sent: 02-11-2019 20:36
    > From: Ed Sutton
    > Subject: The soundboard pushing the rim out question
    >
    > In the video, Craig cut some bars such that they were arched into a tight fit in the notches in the rim.
    > A soundboard, compression or rib crowned, is arched by its internal structure before it is glued into the piano.
    > Think more like a dinner plate which is inverted and glued by its rim.
    > This image leads me to think that the purpose of the M & H spider is to stiffen the rim before the soundboard is glued in, not to somehow increase the crown or "tune" the soundboard.
    > Having seen one or two M & H's with "shredded" soundboards, I wonder if this was caused by someone tightening the turnbuckles.
    >
    > ------------------------------
    > Ed Sutton
    > ed440@me.com <ed440@me.com>
    > (980) 254-7413
    >
    > Original Message:
    > Sent: 02-11-2019 13:08
    > From: Chris Chernobieff
    > Subject: The soundboard pushing the rim out question
    >
    > JIM Said,
    > " Nossaman was talking about the panel changes as a result of down bearing, given a stable perimeter dimension."
    >
    > But that doesn't even attempt to answer the question if acting forces expand the rim or not.
    >
    >
    > Here's a Ron Quote in answer to the question
    >
    >
    >
    > "From Buttressed Arch question for Ron
    > Question 11
    >
    >
    >> IS there a force
    >
    >
    >> pushing the rim out,
    >
    >
    > ??Ron,
    >
    >
    > No, there is not. There is some rotational force on the belly
    >
    >
    > rail from string downbearing because it's cantilevered, but it
    >
    >
    > has no affect on crown".
    >
    > Doesn't the?? Craig Hair video show that a force does push out on the rim. If the rim is being changed and the ribs go up and down, doesn't that show a connection between the two?
    > -chris
    >
    >
    >
    >
    >
    >
    >
    >
    >
    > ------------------------------
    > Troubles are Bubbles, and they just float away.
    > chernobieffpiano.com
    > grandpianoman@protonmail.com <grandpianoman@protonmail.com>
    > Knoxville, TN
    > 865-986-7720
    >
    > Original Message:
    > Sent: 02-11-2019 00:21
    > From: Chris Chernobieff
    > Subject: The soundboard pushing the rim out question
    >
    > Jim Said,
    > "One thing I do know, from observing my boards as I test load and measure them with indicators, is that the effect the perimeter glue joint has on overall and local stiffness of the structure is huge. Its huge, and I missed it for a long time. Missed it, because I visually simplified the system to conform to the limitations of what I could??imagine was happening."
    >
    > A good little demo of this is to use a paint stick. Hold one end in your hand and flick it. You'll get nothing. Clamp one end in a vice, flick it, and it behaves totally different.
    > -chris
    >
    > ------------------------------
    > Troubles are Bubbles, and they just float away.
    > chernobieffpiano.com
    > grandpianoman@protonmail.com <grandpianoman@protonmail.com>
    > Knoxville, TN
    > 865-986-7720
    >
    > Original Message:
    > Sent: 02-10-2019 18:16
    > From: Jim Ialeggio
    > Subject: The soundboard pushing the rim out question
    >
    > ahh..thx.
    >
    > Re the expansion question, if it did expand, as shown in Craig Hair's demonstration, expansion would not be uniform, because of the shapes involved. One part would expand, but that expansion would reduce other areas in a push-me-pull-you scenario. Its too easy in all of this visualizing of what might be happening, to reduce a serpentine, looped structure from three interactive dimensions to a simple linear two dimensional 1+1 model. Why...because its much simple and easier to think linearly and in two dimensions. But I think there are, unfortunately, way more variables involved, which of course makes it harder to think about.
    >
    > One thing I do know, from observing my boards as I test load and measure them with indicators, is that the effect the perimeter glue joint has on overall and local stiffness of the structure is huge. Its huge, and I missed it for a long time. Missed it, because I visually simplified the system to conform to the limitations of what I could??imagine was happening.
    >
    > ------------------------------
    > Jim Ialeggio
    > grandpianosolutions.com
    > Shirley, MA
    > 978 425-9026
    >
    > Original Message:
    > Sent: 02-10-2019 16:43
    > From: Phil Bondi
    > Subject: The soundboard pushing the rim out question
    >
    > Ron N.
    >
    >
    >
    > Original Message------
    >
    > what's RN?
    >
    > ------------------------------
    > Jim Ialeggio
    > grandpianosolutions.com
    > Shirley, MA
    > 978 425-9026
    > ------------------------------
    >
    >
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  • 14.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-12-2019 14:53
    First, how about stuffing a rolled up sock between the resonating rod and a beam or even the soundboard?

    ------------------------------
    Ed Sutton
    ed440@me.com
    (980) 254-7413
    ------------------------------



  • 15.  RE: The soundboard pushing the rim out question

    Registered Piano Technician
    Posted 02-12-2019 17:06
    EdS,
    That's not the first time I've been told to "Put a sock in it!"
    But, seriously, I'll try that first! Thanks. 
    ~ jeannie 

    Jeannie Grassi, Registered Piano Technician
    Island Piano Service
    Bainbridge Island, WA
    206-842-3721