Guy, If two-plies have similar bending stress characteristics, what happens as the number of plies increases? Do more plies give greater resistance to bending stress? What about break strength? Forgive me if I failed to get this from previous posts. I assure you it was not for lack of trying... :-]. Regards, William R. Monroe ----- Original Message ----- From: "Nichols" <nicho@zianet.com> To: "Pianotech List" <pianotech@ptg.org> Sent: Friday, February 17, 2006 11:33 AM Subject: Re: laminated ribs > > Terry, > In both beams, solid and laminated, the beam is a "system". When you > add up the parts of the whole, bending stress and breaking strength vary at > different values. The difference in variance changes dramatically with the > overall difference between systems. A two-ply lamination will have very > similar bending stress characteristics, but the breaking strength will be > more different. As the number of plies increases, the variance changes, of > course, but not as much. A dozen variables make it difficult to call it > logarithmic, but it's basically a case of diminishing returns for bending > compared to improved breaking values. If I recall correctly. It's > been...... decades. > > Guy > > > > At 10:41 AM 2/17/2006 -0500, you wrote: > >>>>I'm with you on ease of crowning, accuracy and more uniform statistical > >>>>average MOE from batch to batch. But why would a laminated beam have a > >>>>higher average MOE than a similar solid beam? > >>>> > >>>>Terry Farrell > >>> > >>> > >>>I'm not sure, but they seem to. I tested this once and recall finding > >>>that to be the case, but it's been a while so I might be mistaken. > >>>Memory leaks, and such. Maybe it's time to do it again. > >>> > >>>Ron N > >> > >> > >>No Ron you're not mistaken. Laminated beams have a higher MOE. > > > >Let's see where this goes. > > > >>Relative to a solid beam, the internal stresses which occur naturally in > >>the growing tree are largely dissipated when the individual layers are > >>joined back to form a whole. > > > >Yes, I see that and agree. > > > >>One only has to watch sawn strips warping all over the place as they come > >>off the saw to realise what must be going on inside the full piece prior > >>to resawing. > > > >Amazing, isn't it? And a bit scary! But sure, I see that all the time. > > > >>Think a tug-of-war analogy. With five strong people of nearly of equal > >>strength, at either end of a rope, it will only take a small addition > >>plus or minus to topple the balance in one direction. If those five > >>strong people were all working together holding a bar firm, for example, > >>it would take much more than a small force to move the bar. > > > >True. > > > >>Similarly, the various sectors of wood in a solid beam are not acting to > >>support a given load. > > > >I'm not sure I understand that. > > > >>Some will be trying to move with the load while other sectors will be > >>supporting it. > > > >Yes, agreed. Some vectors may be supporting the load more than a neutral > >piece, while others will offer less than neutral support. So wouldn't that > >mean a net stress vector of zero? Just like with the laminated beam, if > >the solid beam is not bending on it's own (unloaded), the net strain is > >zero, and hence the net stress is zero. If a load is applied, seems to me > >the two types of equally dimensioned beams would have a similar ability to > >support, i.e. similar MOE. > > > >>If a similarly dimensioned laminated beam was used to resist a load a > >>much higher proportion of the beam will be working to support the load. > >>Hence the higher MOE in the laminated beam. Hope that makes sense. > > > >No, it doesn't. But that may just be me. Seems to me that if beams of the > >two types with no load will have a net strain of zero and thus should be > >able to support similar loads. I understand your point of the greater > >internal stresses in the solid beam, but if they cancel out (which them > >must if the solid beam is straight), there is no net stress and it will > >behave similar to the laminated beam. I suspect the solid beam might reach > >failure at a lighter load than the laminated beam, but I don't see why the > >strain in relation to stress would differ. > > > >Care to try prying through my thick skull again? Or maybe I just need to > >take a few beams and apply some loads. I'll try to do that this weekend. > > > >Terry Farrell > > > >>Ron O. > >>OVERS PIANOS - SYDNEY > >> Grand Piano Manufacturers > > > > > >_______________________________________________ > >Pianotech list info: https://www.moypiano.com/resources/#archives > > > > _______________________________________________ > Pianotech list info: https://www.moypiano.com/resources/#archives > >
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