> My recollections here are that the pins remain high when the bridge > shrinks back down. Dry weather is when I seem to find pins floating up > off the bottom needing to be tapped. Dry weather is indeed when false beats are the worst. What indication did you have that the pins were floating off the bottom and needed tapped, other than hearing a false beat and assuming the pins were floating? >Is it not plausible that increased > downbearing in humid seasons is what reduces the falseness? It might be contributory, but I don't think it's significant. > It seems the pin would have to wallow the hole at the bottom if it is > flagpoling at the top. That energy has to go somewhere. I see. There is very little side stress at the bottom of the hole. It's all at the top, where the hole oblongs and makes a nice gently curved funnel for the pin to spring and flagpole in. Look at the leverage ratios. The side stress on the pin is 0.015"-0.018" (thereabouts), and the point of support to that stress is ideally at the bridge cap surface, but moves farther down into the cap as the wood crushes. Even if the pin is presenting 0.050" of unsupported pin between the point of support and the string contact, the bottom of the pin is under less than 1/10 of that string bearing load. Remember the old advice that if you can't easily pull the pins with pliers, they're ok, and it's ready to string? Well, it's not. If there were flagpoling pin induced false beats before stringing, they'll be there with the new strings too unless the pins are at least CA'd, regardless of how tight the pin is at the bottom of the hole. > Without having a cross section to study, or a teeny weeny camera to go > in and inspect the hole, I'm imagining each end of the pin flagpoling > with the string vibration, somewhat like holding a pencil in the middle > and "flicking" it. Regardless of how many fingers or fists you hold it > tightly with, the pointed end vibrates when you flick the eraser end > unless the tip is anchored. But having the sharpened end anchored, the > movement of the eraser end is further restricted (and sound is > transmitted more solidly), regardless of how tightly it is held nearer > to the eraser. The top of the pin cannot move nearly as much if the > point is anchored at the bottom, regardless of how tight or loose it is > at the cap. Wrong mental image. More like a yardstick partially hanging over the table edge and clamped down by a pile of books. Flick the overhanging end, and it oscillates - faster or slower depending on the free length. That's what bridge pins do too. They flex with string movement if they aren't solidly anchored right at the top of the cap. The produced beat rate is dependent on the diameter of the pin, the distance between the string contact point and the point at which the pin is solidly supported in the bridge cap, how far back from the notch the effective vertical string support is, and the frequency of the string's speaking length. Beat rates are different for each string because the effective point of support down in the cap is slightly different, as is the crushed notch edge for that particular string. This type of false beat only happens in the higher frequency areas of the piano, with the smaller diameter pins. That's why you don't get loose pin beats in the lower half of the scale. It's only in the top half that the flagpoling frequency can be close enough to the string frequency to make the beat audible. > A simplified comparison for sure. But, such is my mind. > :u) It really is a simple phenomenon once we get past a few entrenched assumptions. Ron N
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