This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment ----- Original Message -----=20 From: Erwinspiano@AOL.COM=20 To: pianotech@ptg.org=20 Sent: July 12, 2002 12:29 PM Subject: Re: Bridge design In a message dated 7/12/2002 10:31:34 AM Pacific Daylight Time, = pianobuilders@olynet.com writes: Del Thanks=20 Pre-molded rib radius. That is slick. Makes sense. Any = observations to tonal differences? /superiority of Lam. ribs verses = crown cut ribs? I suspect not and any tonal enhancement difference is = in the design. Still on the learning curve. What about number of laminations? Have you found an optimum? My = thought is long deep ribs will require more thinner lams. or less = thicker lams. and shorter ribs the same thing depending on some decision = as to what's enough for adequate stiffness, consistency etc. Economically more lams. means more machining Dale Erwin 1) Tonal superiority. All things being equal I doubt there is any = though I've done any specific testing to prove this. I'm not sure how I = could. There are too many other variations job-to-job to be able to = isolate just the one factor. In other words, if there is a difference, = it's not dramatic. The laminated ribs are more consistent rib-to-rib = since the variations of wood characteristics are evened out. For the = same reason I believe crown stability to be better and longer lasting. 2) Number of laminations. I know the lay-up schedule we use = --it's different for each height of rib -- whether that is optimum or = not I don't know. It works and works well. It's not really a matter of 'adequate stiffness.' The stiffness of = the finished rib is going to be a function of the wood characteristic -- = its stiffness, or its MOE -- and the overall height and width = cross-section. It's more a matter of how much spring-back is allowable. = When bent laminates are made there is always some springback when the = laminated is taken from the press. This is true whether a glulam beam is = being made for your church roof or a grand rim is being taken from the = rim press. A rib with more, thinner laminations has less spring back = than does one fewer, thicker laminations. 3) I did not start developing and using laminated ribs as an = economy move, though they probably would be on a much larger scale of = manufacturing. They certainly make better use of excellent quality wood = that would otherwise go to waste. Nor do we continue using them for = economy reasons now. Indeed, they are some more expensive for us to make = on our very small scale of manufacturing -- whacking out a few solid = spruce ribs would be some cheaper. We continue using laminated ribs for = the various reasons mentioned in earlier posts. Del ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/19/f7/27/27/attachment.htm ---------------------- multipart/alternative attachment--
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