Hi Phil A couple things might be good to keep in mind whilst all these more abstract numbers scenarios are being tossed around. Bridge pin angle is something that has been experiemented with by manufacturers through the years. The present standards are more a result of experience with what actually works then a reliance on what in theory should work. And of primary concern has been holding a strong contact to the bridge in the face of even the strongest levels of play. One only needs to look at the Capo bar and the classic Steinway forward duplex arrangement to see how much action is really going on at termination points. The constant battle to keep <<noise>> from front terminations under control shows clearly the need for some kind of a clamp condition for the very mild angle the strings are offset at the bridge. The front edge of the bridge is going to get crushed because of a whole varity of factors. The fact that the string is being yanked up and down violently non the least. I've noticed very clear evidence that strings that are played more then others will display deeper grooves over time. I've also noted conclusive evidence that strings will dig significantly into the bridge cap without the presence of bridge pins, more then some might think. 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 ...? 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 Phil Ford writes Thinking some more about bridge notch crushing. Aside from making the cap from some impenetrable substance, one way to reduce bearing stress at the notch edge would be to reduce resistance to the upward movement of the string. This could be done by reducing side bearing angle and bridge pin angle. If there was no side offset at all and the pin was straight up and down then it could easily slide as the bridge moved and the downbearing would be enough to keep it seated on the bridge at all times. Of course, it wouldn't sound too good. I wonder what lower limits would be? Has anyone experimented with this. I would think that establishing minimum sidebearing angle would be something that some piano company has worked on. Is anyone aware of any numbers? Bridge pin angle is something that seems less obvious as an item of investigation, but perhaps work has been done on that too. Anyone know of anything? Phil Ford
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