<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 5.50.4522.1800" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>I'm sure Ron N. and Del with have some excellent advice for you, = but here are a couple preliminary things to consider.</DIV> <DIV> </DIV> <DIV>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.</DIV> <DIV> </DIV> <DIV>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.</DIV> <DIV> </DIV> <DIV>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.</DIV> <DIV> </DIV> <DIV>Terry Farrell <SPAN = id=__#Ath#SignaturePos__></SPAN> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=TSheehan@nyc.rr.com = href="mailto:TSheehan@nyc.rr.com">Thomas Sheehan</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">Pianotech</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, June 13, 2001 = 12:30 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Rolled bridge: cause? = diagnosis? treatment? Or maybe a floating pinblock?</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Dear colleagues - </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>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.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>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.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>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. </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>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). </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>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. </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>No or maybe a little improvement in stability. = </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>All plate perimeter screws are tight, as are = webbing screws.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>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? </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Thank you very much in advance for your comments = and advice!</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>See you in Reno!?!?!?!?!?!!!!!</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Sincerely,</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Tom Sheehan, RPT</FONT></DIV> <DIV><FONT size=2>NYC = Chapter</FONT></DIV></BLOCKQUOTE></BODY></HTML>