Ron O. This particular D (1946, CD in New York for 20+ years before coming to IC) would be a great experiment for a modification along your lines of thinking. Getting the money and finding a person willing and able will be another thing entirely. I can only hope! Thanks, Don > Hello Don and all, > > I have a clue as to ". . . why this happened". After considering > the structure of these belly rails, I would be very concerned about > connecting such a tension device. In my workshop, the solution to > this soundboard-perimeter-support-stiffness problem has been to > ditch the 'bell' and fit an extra back beam in the treble. > > Take a look at the following image of a Hamburg model D from the > 60's, in the process of being rebuilt. > > http://overspianos.com.au/stdctoff1.jpg > > Notice the belly rail where the back beam connects with the belly > rail. Now look at the members which are glued together to make up > this belly rail assembly. The total thickness of the full-depth- > section of this belly rail is a mere 30 mm wide. The pine piece > immediately behind the belly rail, with the large knot in it, is > the filler piece between the belly rail and the laminated piece > which actually connects with the soundboard. It amazes me why a > manufacturer, who goes to the trouble of building a rim with a > solid 85 mm overall thickness, would fit only a 30 mm thick belly > rail to a concert size instrument. It is totally under-engineered. > The addition of an extra back beam, coupled with the bent bass > corner cut-off really helps to stiffen these cases to appropriate > levels across the belly rail in the treble area. The dimensional > size of this belly rail also goes some way towards explaining why > this manufacturer chooses to glue the keybed to the belly rail. > > Another practice which I find baffling is why some manufacturers > choose to use weak-and-lossy pine for the connecting strip between > the belly rail and the soundboard perimeter support strip across > the belly rail. Quite a few manufacturers do this. It would seem to > be a wonderful way to cripple the structural integrity of the > soundboard's perimeter support. > > Here's a second image which shows the extra back beam and the bass > side cut-off, when viewed from the font of the piano. > > http://overspianos.com.au/stdctoff2.jpg > > Here's an image of our 225 grand piano's belly rail in the treble > area. > > http://members.optusnet.com.au/ronovers/oversno6.2.jpg > > The full depth members of this belly rail assembly is made from two > pieces of rock maple which are each 30 mm thick, making a total > belly rail thickness of 60 mm. The piece which connects the full > depth section of the belly rail to the soundboard-perimeter-support > piece is also made from rock maple. The back beams are also made > from rock maple, and there are two of them covering the treble > sections. The treble is where we need stiffness and structural > integrity, not at the bass/treble cross where the plate horn > collects. The 'tone-collector' myth is somewhat ironic, since the > practice of running most of the back beams to the cross between the > bass and treble makes this area stronger at the expense of the > treble sections, which are the ones which really need it. If design > people would pay more attention to structural requirements instead > of pandering to piano-making myth and folklore, we might get to > take contemporary piano design somewhere worthwhile while we're > above ground. Please note that these comments are general in > application, and not intended to be directed at a single manufacturer. > > Ron O. Don McKechnie Piano Technician Ithaca College dmckech at ithaca.edu 607-274-3908 -------------- next part -------------- An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/caut.php/attachments/20070517/9ba20d52/attachment.html
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