Phil, So.. you are taking the position that upward pressure by the bridge surface simply increases sidebearing and there by more friction, and that the increased upward pressure by the bridge on the string is more then countered by that increased friction ? If that were the case, then my little brass plate experiement below would fail. And it doesnt. Yes I have done it, along with a few other experiements about things that are not supposed to be happening according to the numbers perspective. I'm a practical oriented person. Instead of simply looking at what I think should be happening, I try and find ways of seeing what actually is happening. You can get the same condition of pins off the bridge cap with a brass surface. I personally believe the focus of this discussion is all wrong. Instead of trying to prove a pre-thought-out idea by use of what must neccessarilly be an incomplete model, why not simply construct a whole set of experiements to find out exactly what happens under varioius controlled situations first ? Then go about trying to explain. So far it's painfully obvious no one really knows for sure why exactly strings can find themselves away from the bridge surface in the various situations they do. And, despite this lack of knowing... we are witness to numbers being used to attempt to <<prove>> that one and only one basic reason exists for this, and that represents essentially a destroyed bridge cap. On the side... I ran into a brand new (2 years old) S&S D a few days ago and noticed what appeared to be severely buried bridge pins. Today I got a chance to take off a few strings and check it out... holy tomatoes... Somebody has virtually mashed the strings down into this bridge. It looks like someone virtually decided to wedge the strings into the angle between the pin and cap. Mostly front.. but back as well. String mark traces the entire surface of the bridge, and in the middle its width is at least half the diamter of the strings. At the front edge I'd take a rough guess that the thing was one third the strings diameter in depth. This was some darned agreesive string seating.... no way this comes from the factory like this, and no way 2 years of climate has done this. Someone got really carried away. Piano has all kinds of flimmering string noises.... a real shame... 1.2 million kroner these things cost here.... Cheers RicB Phil responds to RicB >/One other thought... since you are interested in the numbers />/perspective. Amoung the factors exerting a significant force />/upwards is that 1500 psi the bridge cap can take, which I assume />/increases with each tiny micron of compression in the wood. With />/that at a maximum, the net force needed to break whatever friction />/levels at the pins is quite a bit lower yes ...? / Well no, actually, if some of the numbers that I threw around are correct. That was the reason for questioning in the first place whether we really need the 'traditional' levels of side bearing and bridge pin angle for a properly built piano, or if they're only there to be 'safe' for pianos without adequate downbearing. >/ Strings vibrating, soundboard vibrating, pins themselves />/vibrating, all pretty violently seen from perspective of that exact />/termination point. />/For doubters... find an old beater and shave off about 2 mm of />/bridge cap, and replace with same thickness brass... carefully />/fitting around the front bridge pins to yeild the same termination />/profile as a new wooden cap. Re-string the spot and subject it to />/some concentrated use conditions for a half a year... bang on the />/string...vary the humidity over time.... etc etc. />/ />/Cheers />/RicB / And if we do that what will we see? Have you done this? Phil Ford
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