This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment I'm sure Ron N. and Del with have some excellent advice for you, but = here are a couple preliminary things to consider. You say that the rear top edge of the bridge averages 1/8" taller than = the front. Has the bridge come loose from the board? If the soundboard = plane (well, it's close to planar) and the string plane were roughly = parallel to begin with, the two bridge top edges should be pretty close = to the same height - whether the bridge is rolled or not. This sounds to = me like whoever planed the bridge cap down was leaning a bit to the left = (if they were standing on the curved side of the piano!), i.e. a = construction error. Front and rear downbearing are best measured with a component = downbearing gauge. Keep in mind though, that if the bridge cap was not = properly planed during construction, bad component downbearing may not = mean a rolled bridge. I have found that examination of the soundboard is also a good way to = characterize a rolled bridge. Do the taut string test on the bottom side = of the piano. You really need to be precise with this. Stretch that = string and carefully and look for soundboard crown. But look also for = inverse crown. You need to be pulling the string up and down repeatedly = to observe when and where the string is contacting the board. Have good = light casting a good shadow. Check many places. If the bridge was = originally constructed well and now it is rolled, presumably the = soundboard has also deformed. If the bridge has rolled forward, on the = front side of the bridge you will have a soundboard with either inverted = crown, a flat board, or less crown that the rear - and on the rear side = the board should have some nice crown, or at least more so than the = front. Terry Farrell =20 ----- Original Message -----=20 From: Thomas Sheehan=20 To: Pianotech=20 Sent: Wednesday, June 13, 2001 12:30 AM Subject: Rolled bridge: cause? diagnosis? treatment? Or maybe a = floating pinblock? Dear colleagues -=20 The piano is a 1972 S&S Hamburg B. It was restrung about 5 years ago, = and had the pinblock replaced (Falconwood, unfortunately), and also had = new hammers (S&S - Hamburg), shanks & flanges installed. The company = that did the work is an experienced rebuilding outfit. The piano came back "dead". Very limited sustain - less than 5 seconds = in octaves 6 and 7 (many notes). Extremely dead rear duplex - less than = 2 seconds in top two sections. Weak upper partial volume and sustain = throughout. Bass is tubby. False beats throughout; weird out-of-tune = partials in the bass. All these tonal phenomena occur whether the string = is struck by a hammer, or is plucked. After racking my brains about this piano (I service it about 2x per = year), I finally had the idea to measure the height of the bridge cap = above the soundboard, on both the speaking length side, and on the rear = duplex side. The rear duplex side is anywhere from 2/32" to 6/32" inch = _higher_ than the speaking length side.=20 The piano is extremely unstable. It is impossible to get absolutely = beatless unisons for more than 2 - 5 mf to ff hammer strokes. The = beating that does creep in is very slight, but noticeable to my nearly = 28 years of tuning experience ears (credited tuner by name on many = Grammy Award-winning recordings, as well as concert piano factory = trained by Yamaha, Steinway & Baldwin; occasional tuner at Carnegie Hall = and Lincoln Center).=20 Although I really dislike Falconwood blocks, this one is measuring an = average of 140 inch/lbs. Not too tight. 2/0 pins with about 3/8" = clearance between the bottom of the coil and the plate. I have squeezed = the wire gently around the hitch pins so that the strings are parallel = to each other. I have also used CLP at the capo, agraffe, understring = felt, and the apex of the rear duplex, and at the raised projection that = terminates the upper duplex in the top two sections.=20 No or maybe a little improvement in stability.=20 All plate perimeter screws are tight, as are webbing screws. Does this sound like a rolled bridge? How is a rolled bridge caused? = Is there an accurate way to diagnose a rolled bridge? Can it be fixed in = the field?=20 Thank you very much in advance for your comments and advice! See you in Reno!?!?!?!?!?!!!!! Sincerely, Tom Sheehan, RPT NYC Chapter ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/e1/76/72/cb/attachment.htm ---------------------- multipart/alternative attachment--
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