John wrote: "As to the upright...bear in mind that this is vertically strung with the soundboard deals running horizontally and the bars vertically. As is normal, an isoceles triangle top left is made dumb and solid. The surface of this triangle is level with the under side of the soundboard but is bevelled along the hypotenuse and this bevel terminates in a bearing. Over this bearing the soundboard is cantilevered and edged with a substantial maple bar. Through this bar pass five large screws. By adjusting these screws the edge of the board is drawn down towards the bevel and the crown is thereby levered up." My limited cranium is trying to picture the above. Is the bottom line here that the normally 1 or 2 degreed edge of the soundboard can be adjusted - cocked a bit so as to force more crown into the board? Sounds amazing! "His remedy he told me (after forbidding me to laugh) had been to knock wedges in at the rim to force up the crown." Oh, boy. Might that wreak a bit of havoc on the rim-to-soundboard glue joint? Gotta be careful here though, if the board started out with negative crown you might just end up with an interesting salad bowl! Personally I think the better approach (no, no, I have never tried this) would be to get a very large hose clamp - the screw adjustable kind - maybe get one with a real large screw - and put it around the outside of the case at a level at or just below the soundboard - OK, put a little spacer in at the concave curved part of the case - and then just tighten as needed! Never a need to replace the soundboard to get desired crown! Terry Farrell ----- Original Message ----- From: "John Delacour" <JD@Pianomaker.co.uk> To: <pianotech@ptg.org> Sent: Tuesday, September 25, 2001 7:04 AM Subject: Brinsmead soundboards etc. > At 06:33 24/09/01 -0400, Farrell wrote: > > >Well, if no one else is going to ask, I will. Please describe > >mechanism/design that permits the adjustable-crown soundboard. Is this the > >"Sostenente" soundboard? If not, please describe that. Thanks. > > I'll describe the sostenente soundboard when I've had a chance to get to London to look at this and various other interesting patents. I have some inkling of how the effect is achieved just from looking at the design of the boards but I want to find out how Brinsmead claimed to achieve it -- such things as the thicknessing and crowning of the board, the way the deals are jointed etc. cannot be found out by just looking, any more than you could tell by looking how Del planes his bars. > > As to the upright...bear in mind that this is vertically strung with the soundboard deals running horizontally and the bars vertically. As is normal, an isoceles triangle top left is made dumb and solid. The surface of this triangle is level with the under side of the soundboard but is bevelled along the hypotenuse and this bevel terminates in a bearing. Over this bearing the soundboard is cantilevered and edged with a substantial maple bar. Through this bar pass five large screws. By adjusting these screws the edge of the board is drawn down towards the bevel and the crown is thereby levered up. > > As I have said, after 100 years I have not found it necessary to make this adjustment, but it is interesting if only as a curiosity. By coincidence I was talking to a colleague the other day who has made three 'grand' pianos to what seems like a pretty odd design and he told me how one of these, after three years had deteriorated and lost its crown (not surprisingly, I thought!). His remedy he told me (after forbidding me to laugh) had been to knock wedges in at the rim to force up the crown. He claimed the improvement was astounding.... > > JD > > > > > > > > >
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