Ron, Have you spoken to Del Fandrich about is notcher. Sounds like you are designing the same one he currently uses. Tom Servinsky ----- Original Message ----- From: "Overs Pianos" <sec@overspianos.com.au> To: <pianotech@ptg.org> Sent: Friday, September 07, 2001 10:17 PM Subject: Re: Bridge pin spacing (was Baldwin SD-10) > Phil, Ron N and all, > > > > . . . and how > > >manufacturers decided on that spacing. > > > >. . . there's more aggravation to be had on this subject. The > >farther apart the > >row spacing, the less precision required in lateral pin placement to > >achieve a target stagger angle. The closer the spacing, the greater the > >required precision. Meanwhile, if I was designing the bridge, I'd want the > >pins in far enough from the edges for good support, yet close enough to the > >edges to minimize the amount of wood I'd have to remove to cut the notches. > >No sense making life harder than it has to be. That means that as the > >bridge angle relative to the strings narrows, I'd increase the row spacing. > >It takes a little more time and thought in planning and layout, but > >anything that cuts down (sorry) notching labor is definitely my friend. I > >make nice clean notches, mind you, it's just that I don't much enjoy doing > >it. Maintaining the row spacing through the whole piano works fine too, but > >you spend more time hunkered over a chisel producing it. Someday, a power > >notcher. > > Indeed and what a useful labor saving device it will be. A power > notcher is at the CAD stage in our workshop as you speak. > > >Of course, if you are working with a re-capped bridge on a soundboard that > >isn't being replaced, you can't mess around too much with row spacing > >unless you want to rescale with the newly resulting speaking lengths. Not > >that it's a problem, but it bears consideration. If by the happiest > >circumstance, you're making your own bridges, you can correct the log > >progression deviations across the treble breaks, smooth the transition > >across the bass/tenor break, and generally build about anything the plate > >will let you get in the piano. That's when it gets fun. > > > >Ron N > > Good post Ron. In the lower bass we might prefer to keep the > front/rear spacing distance to a practical minimum for the bass > singles, to gain the longest possible back scale in shorter to medium > length scales. When using a spreadsheet to design the top elevation, > it is worth making the front/rear spacing gradually increase in the > tenor region as the bridge angle relative to the strings narrows, to > satisfy the objectives Ron N writes about. > > Another area of bridge layout which some manufacturers occasionally > ignore to their peril is the bridge pin spacing between adjacent > unisons. This spacing should allow for the provision of sufficient > bridge wood between pins to allow for adequate pin support. If the > spacing is insufficient, there is a risk of the cumulative side > bearing on each pin group causing cap failure. Some of the smaller > Grotrian designs of the sixties and seventies were particularly prone > to this 'disease'. Some years ago a client of mine purchased a > replacement bridge cap from the factory, in which the pin spacing was > so tight that there was just room for the wire between the pins - > what a disaster in waiting (no surprise then that the original bridge > of his 220 had failed). Surprisingly, the earlier Grotrians (1920s) > were better designed in this respect. Why was the design expertise > which clearly existed at the factory at an earlier time lost? Perhaps > contemporary designers should start out by learning all the old > tricks first. > > Ron O > -- > ______________________________ > > Website: http://www.overspianos.com.au > Email: mailto:ron@overspianos.com.au > ______________________________
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