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Interesting Downbearing Observation

  • 1.  Interesting Downbearing Observation

    Posted 02-12-2018 20:53
    Edited by Jim Ialeggio 02-12-2018 20:58
    S&S A1 turn of the century. I have developed a protocol which allows me to know and prove where the deflected board is going to end up, before I glue down the board or set the height of the bridge. So, while running the protocol, I looked at my spread sheet and see that there is an approx 1/8" jump in bridge height between note 38 and 39...say what?

    First thing was to doubt my calculations. I checked them and rechecked them, and they were spot on. Checked my loaded deflections, and they were spot on.  Say what...then I looked carefully at the plate.
    Then looked at the old cap...no step, just a gradual change in the height as it progressed through this area. Never made this kind of a sudden height change before...some minor ones, but not like this. 
    I still worried about it, after having cecked my proofs, but the protocol, deflection dimensions and calcs were right on. Strung and at pitch it gave smooth progression of DB as measured with a digital angle gauge.

    Without some accommodation here, there can not be any bearing in this area, to the tune of 1/8" shy on zero bearing...pretty major non-bearing condition, I think. I have been paying close attention to these "no win" areas, previous to this, especially note #21​-26 on concert grands,. The  shape of the counterbearing casting on C's and D's makes it pretty difficult, to get even close to reasonable DB, without giving close attention to "gotcha's" defined by the plate.

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    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
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  • 2.  RE: Interesting Downbearing Observation

    Posted 02-12-2018 21:16
    My solution is to grind and shim rests as needed to get the smooth and proper progression of increasing bridge heights from bass to treble that are the Steinway "norm".

    I just completed a 1960's NY D that had a 3-4mm difference between the bottom of the lowest metal duplex string rest and the felted rest on the low tenor. I fitted bridge pins to elevate and support the low end of the shimmed duplex rest and ground away on the shelf below to even the elevations. I also pinned the duplex plate rests to the plate to keep them from wandering.

    I have seen a few original Steinways with a step in the bridge level between string sections, but no more than 1mm or so.

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    Edward McMorrow
    Edmonds WA
    425-299-3431
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  • 3.  RE: Interesting Downbearing Observation

    Posted 02-12-2018 21:26
    I will pay attention to at pitch strung conditions in this area, and see if there is in fact anomalous plate defined lack of bearing here, or whether it was accommodated some other way.

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



  • 4.  RE: Interesting Downbearing Observation

    Posted 02-13-2018 01:03
    I've just delivered a Kawai GS-50 with weird DB setup. In that case I didn't replace board or bridges -- just the pinblock, so I had to work with what was there. There are substantial stretches of zero or negative bearing. I did my best and the pianist (head of the piano department at a university school of music home piano) is happy. This reinforces an opinion I have been coming to.  It may be completely erroneous but here it is:

    Because of empirical experience, I no longer believe that regular transitions of downbearing is necessary -- or even relevant, at least in some situations. Rather, I think the issue is soundboard loading. I think for any given soundboard there is an appropriate zone of total load. Downbearing serves to achieve that load.  As long as the board is loaded into that zone, things will work out.

    Soundboard deflection is correlative to loading -- but the issue is loading, not deflection. i.e., deflection can indicate amount of loading (or whether any loading occurs at all or not) but is not in and of itself the determinative factor to good SB function. Bearing is a "once-removed indicator of deflection and a twice-removed indicator of loading.

    In the case of the Kawai mentioned above, since it was an old board (well ~35 years or so -- at least middle-aged) it did not need as much loading as a new board would.  The plate was setup in a truly bizarre fashion and we did a good bit of plate grinding and substituting individual rests for the aliquot bars. (It wasn't an issue of soundboard collapse-- even if the board/bridge was higher it would have been erratic.)   What we did was apparently enough -- the piano sounds better than when we got it in and I'm quite sure better than when it was new from the factory.

    Well, that's my story and i'm stickin' to it ....
    ;-)

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    Keith Akins
    Akins Pianocraft
    Menominee MI
    715-775-0022
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  • 5.  RE: Interesting Downbearing Observation

    Posted 02-13-2018 14:04
    Keith,  you didn't mention what is perhaps the major "purpose" of DB...that being to avoid challenging the bridge pin terminations. Given their design, they are only marginally structurally adequate when new. Negative bearing, while the board itself, in some circumstances, may still be functional, takes the marginal nature of the bridge pin termination and challenges it further than it needs to be challenged.  Many, certainly not all, but many "soundboard" jobs, are actually bridge termination jobs. DB is probably more of a safety factor than a structural factor.

    In the example I gave, where, without either my fix or Ed's fix, that region would have been placed 1/8" south of zero bearing, would place serious stress on the pin terminations, and thus the apparent life of the either the system, or parts of the scale.   .

    Re DB and laoding, the board needs structure. How much is, I think dependent on the tonal aesthetic one prefers...and there are, multiple viiable tonal aesthetic of piano tone. DB and deflection are to my mind, mainly indications of the structure currently present in the board. I use them as indicators not as primary causal factors.






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



  • 6.  RE: Interesting Downbearing Observation

    Posted 02-13-2018 23:28
    Jim -
    With regret,  I feel like each one of your comments warrants some expansion.   Clearly, I lack any semblance of imagination:

    major "purpose" of DB...that being to avoid challenging the bridge pin terminations.

    Given their design, they are only marginally structurally adequate when new.

    Negative bearing ... takes the marginal nature of the bridge pin termination and challenges it further than it needs to be challenged. 

    Many "soundboard" jobs are actually bridge termination jobs.

    DB is probably more of a safety factor than a structural factor.


    In the example I gave, where, without either my fix or Ed's fix, that region would have been placed 1/8" south of zero bearing, would place serious stress on the pin terminations, and thus the apparent life of the either the system, or parts of the scale.   .

    Re DB and [loading], the board needs structure.

    DB and deflection are to my mind, mainly indications of the structure currently present in the board. I use them as indicators not as primary causal factors.


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    David Skolnik
    Hastings-on-Hudson NY
    914-231-7565
    ------------------------------



  • 7.  RE: Interesting Downbearing Observation

    Posted 02-14-2018 10:15
    <major "purpose" of DB...that being to avoid challenging the bridge pin terminations. 
    Given their design, they are only marginally structurally adequate when new. 
    Negative bearing ... takes the marginal nature of the bridge pin termination and challenges it further than it needs to be challenged.

    The traditional bridge pin setup, though it seems to avoid tonal issues which many bridge agraffes present, is simply a nail pounded into wood...fairly stone age technology. It works. However, though it works, its ability to work, in the long term, is limited by the condition of the wood  and the size of the wood hole it is driven in to. With moisture cycling, or over aggressive lateral termination offset angles, the changeable wood surrounding the pin, enlarges the pin hole and the termination degrades.  Some of the side bearing forces, I think, are mitigated by the string being supported by the surface of the cap. So instead, when there is DB, the pins, the wood laterally,and the wood vertically combine to keep the termination efficient. The pin remains the actual termination, with the wood laterally and vertically supporting the pin in its task. Zero to negative bearing, removes the vertical support offered by the surface of the cap, and forces the pins, and the size of the pin hole to do all the work.  Given how easy it is to enlarge a hole with a nail driven into it, and given how picky the termination requirements are, this creates a scenario where the long term survival of the termination is challenged.

    DB is probably more of a safety factor than a structural factor.

    This is, at least in my take, described above. DB, since the string is pressing down into the cap, takes some of the tendency of the string to work the pin laterally in RH changes, and reduces that tendency, thus offering the pin and pin hole, another vector of support. Zero to neg DB removes that added support vector. That's the safety factor.

    The structural factor assumes DB is necessary for tonal function of the soundboard structure. This model assumes the board must be pre-loaded by the DB in order to function. Paullelo and Stuart have challenged that assumption by eliminating the pins as a lossy termination, and removing all or most bearing.

    In the example I gave, where, without either my fix or Ed's fix, that region would have been placed 1/8" south of zero bearing, would place serious stress on the pin terminations, and thus the apparent life of the either the system, or parts of the scale.   .

    Not only would this scenario remove the vertical support of the cap from the pin termination, at neg DB, especially gross negative DB, the strings would be actively pulling up and side-wise, on the pin.

    Re DB and [loading], the board needs structure.

    A board without structure will flap in the breeze. How much structure is another question, and somewhat dependent on aesthetic tonal choices. Inadequate internal structure to the board,.results in conditions where individual notes can be, with serious voicing time, made to sound reasonable. However, when the structure is inadequate, the board cannot differentiate more than one note at a time. The more-than-one-note texture becomes muddy, explosive and incapable of amplitude variation. DB is, as far as I can tell in my work, not part of the structure of the board. I can't go to the mat on this one, as it is simply relaying my observations up to this point. However, in my work, I am thinking these days, about DB as a termination requirement, and not as a structural one. I have thus backed it off to the point where I find termination suffers...that is, at this writing(subject to revision, constantly) 1deg@88, reducing to 0.3 bottom of the long bridge, and as close to just slightly positive on the bass bridge as possible.

    Beyond its termination function, I'm currently finding higher bearing to be choking the board more than anything else useful.   As to Keith's point about smooth graduations of DB being not that important, he could be right about that. From my perspective, the only way for me to know whether that is correct of not, is to be capable of creating a piano where I can control the as-built DB curve. This is easier said than done...quite challenging, to control the DB curve in this way, but without actually doing it, and then not doing it, one really can't tell whether even graduation of DB is an important factor or not. I'm in the trying to observe the condition accurately phase..and its a hard phase to pull of practically speaking.



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



  • 8.  RE: Interesting Downbearing Observation

    Posted 02-15-2018 01:08

    Jim,
      Certainly didn't mean to imply or suggest that I think 1/8" negative bearing is a good thing that one would want to achieve. I would certainly want to get it at least to zero. I'm not advocating negative bearing as such. However, I am having experiences with pianos that lead me to question long-accepted orthodoxies regarding soundboard construction and setup.

    Your comment about stressing the bridge pins is certainly a valid concern. Since I am now using the Wapin bridge configuration in every procedure I do on a piano that involves stringing (and some that don't) I realize that bridge pin stress under negative bearing is much less of a concern because of the trapping pin installed behind the front bridge pin that terminates the speaking length of the string although the real reason for the Wapin procedure is for the tonal performance boost that it give.  I also see that the Phoenix bridge agraffes accomplish a similar effect which permits zero or negative bearing. 


    I agree that it is difficult to "experiment" because of structural limitations and costs -- plus, usually we are working on customers' pianos. I have had some opportunity to experiment with bearing on Baldwin pianos with the vertical hitch pins. (One particular SD-10 as well as some smaller models). In those instances I found best results from reducing rather than increasing bearing -- although I never went into negative territory in those cases.

    I think this is an exciting time in the development of the piano and I believe much of the advancement in knowledge and technique is from rebuilders such as yourself who have the vision (and guts) to go beyond just copying what was there. 



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    Keith Akins
    Akins Pianocraft
    Menominee MI
    715-775-0022
    ------------------------------



  • 9.  RE: Interesting Downbearing Observation

    Posted 02-15-2018 07:05
    Edited by Tim Coates 02-15-2018 07:10
    The Wapin Company, LLP does not approve or endorse Mr. Akins comments or methods concerning the Wapin piano bridge when zero or negative downbearing is involved.

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    Tim Coates
    Sioux Falls SD
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  • 10.  RE: Interesting Downbearing Observation

    Posted 02-15-2018 15:31
    Tim -
    I would invariably get into trouble with RonN whenever I referenced Wapin in any discussion about downbearing.   I still find it frustrating that I can find no clear explanation as to how Wapin works.  The website is not accessible, and there's this from the abstract of the 2014 book by David M. Koenig Spectral Analysis of Musical Sounds with Emphasis on the Piano

    There are many different claims as to why this arrangement improves the sound of a piano, though they appear to be more subjective and speculative than objective.

    I don't know if I would take issue with any of the things that Keith Akins said, with regard to negative bearing, but, after all this time, rather than simply refusing to endorse   what he says, why couldn't you provide some clarity?

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    David Skolnik
    Hastings-on-Hudson NY
    914-231-7565
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  • 11.  RE: Interesting Downbearing Observation

    Posted 02-15-2018 19:29
    David,

    Wapin Company, LLP has never stated or suggested the Wapin Bridge can be a good alternative to replacing a sound board that has zero or negative downbeariing.  If you would like an explanation of how the bridge works I suggest you contact Michael Wathen.  He is no longer a member of PTG or any PTG forums.

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    Tim Coates
    Sioux Falls SD
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  • 12.  RE: Interesting Downbearing Observation

    Posted 02-15-2018 20:53
    Thank-you, Tim for this clarification. I also want to be clear in what I intended to convey...

    1) I am not advocating Wapin as a solution to negative bearing situations.  I am reporting on my experiences and since I use Wapin almost every time I touch the belly of a piano, it was a habitual thing to refer to the use of Wapin. However ...

    2) Wapin, as such, is completely incidental to what I was trying to point out. It merely happens that the  protocol does call for a trapping pin behind the front bridge pin and that can serve as one example of a reinforced bridge pin setup that could resist some of the challenges presented to the pins in a negative bearing situation -- even though that has nothing to do with the intention or function of Wapin design.

    3) As a matter entirely separate from any discussion about bearing, I am a convinced user of the Wapin protocol through more than a dozen installations. Results have varied from ball-knocked-out-of-the-park-homerun to merely a double or triple. As a result, I simply don't do belly work without implementing Wapin.

    4) I mentioned another example of something that serves to provide reinforcement to string termination setup in a negative downbearing situation and that is the Phoenix bridge. Again, I was not commenting on the tonal benefits of Phoenix (although to my ear it does seem to have a similar result as Wapin). But the point in my mentioning Phoenix was neither to advocate its use nor to detract from its value but simply to observe that is another approach that may stand up to extra stress of negative bearing.

    My apologies to everyone for any confusion I may have caused about the value of these patented products/procedures and any hint that they may endorse their use in unorthodox approaches or experiments in soundboard work in a sort of "off label prescription" as it were. I take Tim's comment to heart and will be more circumspect in the future.

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    Keith Akins
    Akins Pianocraft
    Menominee MI
    715-775-0022
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  • 13.  RE: Interesting Downbearing Observation

    Posted 02-14-2018 06:00

    In a manned rocket, details to the nth degree are important,
    because the result could be death.
    In a piano, there are many points of diminishing returns,
    before music runs out of breath.
    -chris
    #caveman




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    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
    ------------------------------



  • 14.  RE: Interesting Downbearing Observation

    Posted 02-13-2018 14:14
    Jim -
    An topic easily tangentialized, so I'll do my best not to.  At some point, the protocol itself would be interesting, though I think you've described it previously. My thoughts are general:
    - an implied assumption of an idealized target, given your board structure
    - a perceived relationship between downbearing and tonal response
    - do you distinguish between positive net and the presence of positive front (and rear) bearing
    - are you able to achieve all three?  Do you think it matters?

    Now I'll check my archives to see where you've already answered these.
    Thanks -

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    David Skolnik
    Hastings-on-Hudson NY
    914-231-7565
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  • 15.  RE: Interesting Downbearing Observation

    Posted 02-13-2018 14:30
    Damn. I hate when that happens.  I'll read what you wrote. then I'll apologize.

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    David Skolnik
    Hastings-on-Hudson NY
    914-231-7565
    ------------------------------