---------------------- multipart/alternative attachment Ron and all ?- Distracted by life for a few days, the response I had begun threatens to=20 relinquish relevance, if it had any to start. The topic has attracted some= =20 other views within the last few days, but I think there are details here=20 that merit addressing. There are those who consider the practice of=20 tapping strings a useful, if temporary tool at their disposal, though no=20 significant insights into why. A combination of the video that Ed Sutton=20 is pressing for along with a harmonic analysis seems technologically=20 feasible ($$??). At this point, I strongly suspect that no one else is plowing through these= =20 opuses, so you (Ron) should feel no obligation to continue, unless you feel= =20 I am severely misrepresenting your views. At the end (literally) I find=20 myself in agreement with what you would like to see. At 01:56 AM 4/4/2004 -0600, Ron Nossman wrote: DSkolnik >>I can readily see where the string would find it difficult to move=20 >>upward against both the friction and the vector force, but could imagine= =20 >>it displacing downward, against less friction and in the direction of=20 >>vector force. >RNossman >Which is why the string follows the bridge top back down the pin in dry=20 >cycles. There is, as David love said, a chance that pin damage already=20 >incurred by this wear to interfere with both the upward and downward=20 >motion of the string. DSkolnik With all due respect, David Love's comments represent a theoretical=20 conjecture, just as do my comments and at least one or two of your own. On= =20 the one had, the string moves up and down the pin with the climate cycles,= =20 yet you dismiss the idea that the string could do the same, in a downward=20 movement, in response to vibrating energy. You're stating, I think, that=20 the friction, or mechanical capture by the pin's abraded and notched=20 surface would prevent any significant sliding movement at the pin. On the=20 one hand, I would say, OK, let's assume that, so we could examine the=20 ramifications. On the other hand, it seems that at some amount of=20 unsupported length behind the front bridge pin, the mechanical resistance=20 to some sliding movement would be overcome. In that case, the question=20 would then be, how much length and how much sliding. At some point too, it would make sense to discuss the more precise nature=20 of the pin damage we speak of, what causes it, what it really looks like,=20 and how it might affect both tone and string motion. DS >>Nevertheless, it should be possible to estimate the additional load of a= =20 >>pitch rise of, say 440 to 445. >RN >Yes, it is. This comes up on the list every few months. An arbitrarily=20 >chosen scaling file shows, at 435, 36168lbs total tension, and 682lbs=20 >total down bearing (calculated from bearing angles and tensions). The same= =20 >piano at 440 shows 37004lbs total tension, and 697lbs total down bearing. Thank you DS >>I should be able to do it, but can't, yet. It just seems that whatever=20 >>rise could be attributed to board height increase would be pure load, not= =20 >>the pinching of the string by an expanding bridge top against angled pins. >RN >Even with negative front bearing? Have you ever measured zero or negative= =20 >overall bearing in a piano that has gone sharp with a humidity increase? I= =20 >have, and that doesn't fit your scenario. What scenario? In a piano with positive bearing, whatever increase in=20 board height that occurs would add some additional load to the bridge=20 (assuming pitch is not lowered immediately) without engaging the crushing=20 dynamic of bridge surface pushing against strings locked against=20 pins. You're right that it seems counter-intuitive to see a climate=20 related pitch rise with negative net downbearing. Certainly it is not=20 contradictory where you are dealing only with negative front downbearing. RN > Besides, it's not the rise that's the issue. It's the change in bridge= =20 > surface relative to the pin. Fifteen pounds of extra bearing divided up=20 > among 230 or so strings isn't going to put a heck of a lot more pressure= =20 > on the bridge cap under each individual string compared to the 20+ pounds= =20 > the bridge top takes at each pin pushing the string up the pin. As Ed Sutton suggested yesterday, referring to the string grooves in the=20 bridge, "I believe the compressed wood is more stable than new wood." That= =20 wood doesn't keep compressing, does it? Does the At some point, it seems= =20 that some equilibrium is reached between the recurring crush cycle and the wood fibre damage. A while ago you supplied=20 the information that the side grain compression limit of mock maple was=20 1470psi. Does this figure, in fact, change, once the surface layers are=20 damaged? DS >>Likewise, you or someone else in possession of a brain might be able to=20 >>calculate that portion of the pitch increase that could be attributed to= =20 >>a .030" increase in bridge height. >RN >Yes I can, at least to reasonably illustrative rather than precisely=20 >predict. It requires specifying the starting pitch, speaking length, wire= =20 >diameter(s), back scale length, overall bearing angle, and overall string= =20 >length from tuning pin to hitch. I think that's everything except friction. Do you mean that if I supply this data, you will tell me the answer? DS >>By the way, is it possible to relate the 4% and 12%MC that you referred= =20 >>to earlier to relative humidity? >RN >Do you have a copy of the excel spreadsheet I offered a while back? No, I'm afraid I don't. Are you still offering it? DS >>I don't know...it just seems like you're saying something different. Can= =20 >>you explain? >RN >You want me to explain something you think seems to be something I don't=20 >see? Uh... no, I don't think I can. You choose to ridicule me here. You left out the quotes I felt were=20 inconsistent. I'll repeat them: >In response to me you wrote: > >>I do care about the string contact with the front of the bridge, but I do= =20 >>not agree that tapping the pin will achieve that end. That's the whole=20 >>point of all this. If the string isn't contacting the notch edge, it's=20 >>for a reason that tapping neither string, nor pin will cure. > >In response to Wim, you said: > >>Wimblees: >>>There has been a lot of discussion about tapping the pin to create=20 >>>better tone, less distortion, etc. But what are we doing? Is the better= =20 >>>termination caused because by tapping we are driving the pin deeper into= =20 >>>the wood at the bottom of the hole, thus creating a more stable pin, >>Ron N: >>Partly, but I think mostly dragging the string down with the pin to the=20 >>notch edge. > >and >>WimB >>>So what is the real reason for tapping? More wood, or less pin? >>RonN >>Or seating the string by proxy? You are telling me that you do not believe that tapping either the pin or=20 the string will cure the lack of notch edge contact, but, in response to=20 Wim, you at least imply that that is exactly what is being done. You may=20 not be able to explain it, but you shouldn't place the responsibility for=20 the confusion on me. DS >>Why DO you care about the string contact with the front edge of the= bridge? >RN >Because when it doesn't, it eventually leads to tone production problems=20 >and false beats when the pin gets loose in the bridge. It's a practical=20 >consideration rather than a theoretical one. OK. So you feel that there is some increased likelihood of developing=20 loose bridge pins when strings are elevated from the bridge surface at the= =20 pin. You imply either that the looseness would not develop, were the=20 strings to remain firmly seated, or that loose pins would not be a problem= =20 with seated strings. What are the tone production problems, apart from=20 false beats, that are eventually lead to? For clarity (for any other readers) I'm reinserting the portion of the=20 following exchange that you deleted: RN >>>>Front bearing is the angle between the string segment on the bridge top= =20 >>>>and the speaking length segment. >>>DS >>>My contention is that, since the string segment on the bridge displays=20 >>>considerable curvature, it is misleading to think of angles or to assume= =20 >>>that the imaginary straight line between front and rear bridge pin is=20 >>>meaningful in defining the angle actually formed by the two string=20 >>>segments as they converge at the front pin. RN >>>I disagree. Poor front termination, with the accompanying tonal problems= =20 >>>and false beats, becomes most problematical when the overall front=20 >>>bearing angle (that between the bridge top and speaking length) is very= =20 >>>shallow. A strong positive front bearing angle DOES put the horizontal=20 >>>string termination on the notch edge and none of this stuff even comes=20 >>>up. It's only when that angle becomes shallow enough that the crushed=20 >>>notch edge no longer contacts the string. We've gone over the basic=20 >>>points a number of times reducing them to ever finer isolated details.=20 >>>In the piano, they all exist and interact at once, each in relation to=20 >>>other(s). >>DS >>Here's perhaps where we are still farther apart, and the fact that we've= =20 >>gone over basic points in ever finer detail should be viewed as purely=20 >>positive achievement, in my opinion, not a source of exasperation. >RN >Did I say I was exasperated? The interrelationship is my point, and all=20 >these details have to tie back into the whole to make sense. You did not say you were exasperated, but I heard such in the italicized=20 comment above (my italics - ds). Your response, beginning with "I=20 disagree..." did not address my own previous comment, regarding my view of= =20 the profile of the bridge-string segments I commonly encounter. Of course= =20 it all works together, but insisting on viewing it all together when you=20 are trying to understand the individual contributions makes no sense. DS >>I use a Lowell gauge, but as a determinant for front bearing, I measure=20 >>the smallest possible segment behind the pin to compare with the sounding= =20 >>string segment. As it relates to termination, that's the only relevant= part. >RN >I disagree. WHY? DS >>I also slide the gauge to the rear pin to observe the amount of=20 >>curvature along that segment. It can range from .009" to .050", with the= =20 >>.030" range not being unusual. >RN >What's that in degrees? If you're using the rise per inch from the=20 >graduations on the Lowell gage, that's 0.003" per 10' of angle, isn't it?= =20 >So you're telling me you measure anything from 0.5=B0 to over 2.5=B0 of= curve=20 >over bridge tops? Then again, holding a straight piece of wire in the=20 >groove in a bridge top, tangent to the curve of the groove at the notch=20 >edge, it will likely show more angle than that. I wouldn't consider this=20 >to be a healthy bridge, but as you say, it's what we see the most of in=20 >the field. OK, now how could front bearing that never was over 2=B0 produce= =20 >a 2.5=B0 or greater indentation? I don't know what you are asking, or why. I don't work with degrees. The= =20 exact measurement is irrelevant. Are you questioning my methodology or my= =20 accuracy in the actual measuring process? The numbers I indicated=20 represent the differential measurements taken of the bridge-string segment= =20 with the gauge feet as close together as possible, first proximate to the=20 front pin, then to the rear. They indicate a curved profile rather than=20 the conceptualized straight line. There is no difference in the resulting= =20 bearing loading, but it does mean that, from a termination view, the=20 immediate string segment behind the front pin is that part that will=20 determine the presence of absence of positive front bearing. DS >>Second, I'm sorry to parse your usage, as you sometimes do mine, but you= =20 >>say no "significant sliding motion", which, of course, makes me wonder,=20 >>just how much "insignificant" sliding motion IS taking place? >RN >I have no way to measure it precisely. When you do, please let me know.=20 >With inadequate pin angle and/or inadequate offset angle, I know the=20 >string does indeed slither up and down the pin. It sounds like a dobro on= =20 >drugs, and is pretty hard to miss. And if I said NO motion, I would=20 >certainly be challenged to prove it. When I see and hear a piano with=20 >provably perfect string terminations, I'll have something by which to=20 >judge. Meanwhile, I'm attempting to get across what I consider to be=20 >reasonable, accurate and factual information pending something that makes= =20 >more sense to me. I appreciate your efforts and your vision. (No strokes intended). You=20 have challenge me innumerable times to be clear. That is all I'm asking of= =20 you. When, for example, you say that strings can indeed move on the pin if= =20 the various angles are not correctly executed, then, since we know that=20 many of the pianos we confront in the field ARE less than perfect, it would= =20 stand to reason that the movement of the string at the (tight) pin COULD=20 create some distortion that might be eliminated, temporarily by seating. DS >>Lastly, the analogy with the V bar is interesting but flawed. The offset= =20 >>angle of the string at the bridge pin is considerably less. >RN >How much angle difference constitutes "considerably"? At what point does=20 >"considerably" become significant? And I have certainly seen deflections=20 >across V bars that are similar to and even less than the horizontal offset= =20 >across some bridges I've also seen. I think the analogy is quite valid and= =20 >not that casually dismissed as flawed. Nothing about my communication with you is casual. I said: DS >The offset angle of the string at the bridge pin is considerably less. I measured my Steinway O (1913). The V bar angle was 18 degrees. The=20 bridge pin offset angle was 7 degrees. This seemed significant. DS >The direction of string excitation is perpendicular to the V bar but=20 >parallel to the bridge pin. (If the hammer impact was proximate to a=20 >vertical termination, wouldn't you expect some string displacement? Whether it ultimately has any effect, I nevertheless see this as a=20 significant enough difference in the modeling to have a potential impact. DS >>The direction of string excitation is perpendicular to the V bar but=20 >>parallel to the bridge pin. (If the hammer impact was proximate to a=20 >>vertical termination, wouldn't you expect some string displacement? >RN >Strings vibrate in all directions, not just in the vertical direction of=20 >initial excitation. You hear the tonal problems and false beats long after= =20 >the string has migrated from it's purely vertical excursion path. I'll have to experiment, but it's possible that the non-false beat=20 distortion we've been discussing is associated with the initial part of the= =20 tone, where the vertical mode is still predominant. DS >>If you believe that the tightness of the pin in the bridge is the prime=20 >>determinant of the presence or absence of false beats, why do you find=20 >>negative front bearing unacceptable? >RN >Loose pins with low front bearing. Because pins don't stay tight forever,= =20 >and I'd rather see the redundant support of both the notch edge and the=20 >pin at the same point with positive front bearing so there's enough=20 >friction between the string and the bridge top to keep even a loose pin=20 >from flag poling and making a beat. Wherever I can get one, I'd rather=20 >have a definite than a maybe. I've tuned a lot of pianos that sounded=20 >pretty good and acceptably clean in the humid summer months, but became=20 >un-tunable with false beats and other termination nasties in dry winter=20 >months. Pianos with tight pins and good crown and bearing don't tend to do= =20 >this. > >I said the string doesn't "have" to be touching the bridge at the pin, and= =20 >it doesn't to produce good tone, but it's more likely to produce good tone= =20 >for a longer period if it does. I agree. I agree. David Skolnik ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... 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