---------------------- multipart/alternative attachment Ron Overs wrote: > Bill Bremmer wrote; > >> . . . I need some opinions on what to do about it. It is a > >> Young Chang Grand model G-185, only a few years old. It is >> meticulously > >> cared for but early in it's service, the pianist at this, >> shall we say, >> "spirit filled" church complained of bass strings breaking >> and shooting out > >> of the piano. > > Broken bass strings shoot out of the piano when the string > breaks at the agraffe and the hitch pin is angled back suitably > to steer the projectile-string out of the piano. Bosendorfer > Imperials are famous for this, breaking at note C4 (in the > Bos' this note is actually not the forth string on account of > the extra bass notes) which is strung at nearly 400 lb tension > with 1.35 diameter core wire. I've had two Cs go off and > frighten the hell out me. I actually tune these pianos with my > body off the line of the string to avoid wearing it. > >> I have tried all of the usual. I filed the hammers. > > This is not the problem > >> A monitor feeds back > >> sound to the pianist. > > This will help. > >> When I explained to the church directors that it is > >> the "vigorous" style of playing that sometimes causes strings >> to break, the > >> pianist resigned. . . . . . . . . > >> >> I am thinking that these wound strings must have particularly >> high tension. > >> Does anyone know if this is so? > > The tension is not the problem. The pianist may be part of it, > but not all. Very often, small grands are built with rediculous > string angles at the front bearing bar between the tuning pin > and agraffe (in the bass only). While these angles can be > tolerated in a home piano which might only be tuned biennially, > when such a piano is tuned every other week it will invariably > develop wire fatigue at the bearing bar and agraffe. > >> Over the years I have heard of other such > >> instances that were cured by replacing the wound strings with >> a set of >> lighter gauged, "happy" strings. It would seem to me that a >> lower tension >> would solve the problem but in reading the recent post about >> "replacement >> strings", I am confused. Some of these strings have been >> breaking at the >> bass bridge termination point rather than the agraffe. That >> seems very >> unusual to me. > > Wire breakage at the bridge would tend to indicate that the > wire is fatigued through playing also. Church pianists, like > the congregation, can get pretty overenthusiastic at times. The > feed back monitor can help here. > >> Should the manufacturer supply a new set of wound strings and >> if so, should > >> they be a set designed for lower tension? I presume that >> heavier gauged, > >> higher tension strings provide a bigger, bolder sound. > > A heavier wrap will produce a 'fatter', longer piano sound, > while a heavier core will raise the inharmonicty to produce a > more 'growly' tonal quality. The G185 bass is not a > particularly high tension scale (no piano with a 135 cm > speaking length can be). I would advise against rescaling. In > any event, it's not necessary. The problem lies elsewhere. > >> What effect would > >> lower tension have? Just as a theoretical question, would >> tuning the > >> instrument to a lower pitch, say 100 cents lower prevent this >> from happening > > Percentage of breaking strain !!! The use of a lower tension > bass will not only give the piano a 'gutless' high > inharmonicity bass, but it will lower the percentage of > breaking strain of the bass section (particularly if the same > core wire guage is retained), resulting in a slight reduction > in the tuning stability in response to temperature and humidity > variations. Mind you, there should be some percentage of > breaking strain variation when the string scale crosses from > trichord plain to bichord covers to facilitate tonal equality > at the cross (there should also be a reduction in speaking > length of between 10 - 15% at this point also - it is for this > reason that pianos which use bichord covers for last couple of > notes on the treble bridge, without any step reduction in > speaking length, are always a scaling disaster) > >> It is also interesting to note that to date, only wound >> strings have broken, > >> no plain wire. > > You will also be interested to observe that the extreme string > angles, caused by the too-high bearing bar, only occurs in the > bass. If you restring the bass and reduce the bearing bar > height to reduced the string angle deflection to 15 degrees or > less (I prefer around 12.5 degrees), the problem will go away. > Don't forget to replace the agraffes as well, the silly string > angles will have destroyed the agraffe string hole shape (just > cut one through the lower half of the holes with a hack saw and > investigate the upper bearing surface with a looking glass - > you will be astonished at the damage). We have done this > bearing bar fix many times to small Kawai and Yamaha grands in > commercial service - to good effect. Regards, Ron O -- > Overs Pianos > Sydney Australia > ________________________ > > Web site: http://www.overspianos.com.au > Email: mailto:ron@overspianos.com.au > ________________________ -- Richard Brekne RPT, N.P.T.F. Bergen, Norway mailto:Richard.Brekne@grieg.uib.no ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... 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