Hmmm... Just trying to get a handle on just what stresses are being applied in what directions. Seems a bit more complicated then at first it may seem... but let me try and reword. Lay the panel flat after it was dried out and then blocked the tangential ends (perpedicular to grain). When it takes on humidity it is compressesed radially .. against the tangential face (edge). Yes ?? But we dont actually block the tangential edges... we glue ribs onto one of the radial faces (the underside of the panel) and thus restrict this same (radial) expansion... so we get a somewhat predictable crown instead of random buckling (I suppose). So far so good ?? So... the panel starts to crown then... and in addition to simple radial compression of the panel, there is some form of bending stress introduced. Then putting downbearing into the picture... you are pushing straight down on the upper radial face of the panel...doesnt that introduce some loading along grain the of the panel ? I dont mean the transverse direction as the panel isnt bent this way...(or not much anyways). I mean... you are pushing downwards at some spot close to the middle of this big panel... on its radial face.... I guess what I am wondering is .. isnt there some shear stress along the grain of the panel introduced by pressing directly down on panel ? Perhaps a bit off the wall...:)... but I just want to make sure of things as I go along. Cheers RicB John Hartman wrote: > Richard Brekne wrote: > > > While I got your ear, perhaps you might straighten me out on whats being > > loaded how... I suppose the ribs restrictions loads the panel radially... > > against the tangental face ??....even tho this is being done by restricting > > the outward expansion of the radial face. But then downbearing... Ok that also > > affects the stress between the ribs and underside of the panel, but isnt there > > some tangential loading going on here as well ?... or is that just confusion > > and all the loading is in the same direction ? > > > > Sorry Richard you lost me. Care to rewrite this to make it easier for me? > > John Hartman RPT > > John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] > Rebuilding Steinway and Mason & Hamlin > Grand Pianos Since 1979 > > Piano Technicians Journal > Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015] > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html http://www.hf.uib.no/grieg/personer/cv_RB.html
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