This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment good evening to all, I have been reading the comments on shear force with much interest.This = being the first time I have felt I can offer some thought on a subject I = hope that it helps.Basically it follows what most other people have been = saying. 1.Stress is the force per unit area on a body. e.g. the force applied to = a material 25m^2 is 100N, the material is under a stress of = 100N/25m^2=3D4Nm^2 2.Shearing forces try to slide particles or layers of a body over one = another.=20 The string exerts a force of 12kg+/- 5kg on the bridge pin which is = trying to shear the bridge pin in two.As the bridge pin has a high = resistance to shearing forces the pin exerts a compressive (relatively = speaking) force onto the bridge this is resisted by the material around = the pin.As the wood is able to resist a shearing force is felt at the = glue joint between the bridge and soundboard (assuming there is no = bridge cap) as this is extremely strong it resists the initial string = force.I am sure you have all seen what happens when the glue joint fails = between the bridge and sound board, usually the bridge has moved = position(depending on other variables)I feel the tensile force between = the bridge pin and CA glue is negligible.Imagine if there was only the = tensile strength of the glue holding the bridge pin and not the wood , = there would be no way the tensile strength of the CA glue could resist = a stress of 120N acting on an area .775mm^2. Also because the glue joint between the bridge and soundboard is so = strong (for the forces we are using) we could assume that the bridge = and soundboard are one. So now it could be said that the bridge pin is = exerting a shearing force on the bridge/soundboard.When bridges split it = because this is the weakest link in the chain, I seriously doubt a = bridge pin will ever shear and as long as the glue joint is strong the = bridge will never shear from the soundboard. The wood around the bridge = pin will give usually give way when the holes are usually drilled to = close together and/or the hole is drilled to close to the edge of the = bridge. I am doubtful as to how much strength the CA glue actually offers to the = resistance of string forces(long term) I would think reducing the string = force on the bridge pin would be a better move of recap/replace the = bridge.=20 I hope this has helped, apologies for writing some much. time for sleep, good night/morning Stuart Balsillie Piano Technician Victoria Australia sabalsillie.@bigpond.com ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/7c/07/ee/13/attachment.htm ---------------------- multipart/alternative attachment--
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