Hi Dale, You probably saw this already, but, just in case, Ron Nossaman touched on one example like you're talking about in a recent post talking about an upright with the break between C3 and C#3, that comes standard with all plain wires on the long bridge. Ron said (emphasis added): "For instance, that 38.75" C#-3 with plain wire trichord will be at about 24% of breaking tension (regardless of wire size, within reason). That's pretty low, and will be very reactive to tension changes resulting from humidity fluctuations, meaning it will go out of tune quicker and farther than unisons farther up-scale, or down scale in the high bass. Tension will be determined by the wire size used there. For instance, unison tension with #20 will be about 404 lbs, or about 369 lbs with #19. Going to a bichord unison, dropping two or three half sizes for the core, and figuring wrap to get back near the unison tension that was originally there will raise the break% to around 40%. That's going to be a more stabile unison with humidity changes, and sound better too. The trouble is, that puts you at the bottom of the list of available copper wrap sizes, requiring about a 0.007" wrap to keep the tension down around where it was with the plain strings. Arledge uses as small as 0.006" for copper wrap. That takes care of C#-3, if the impedance and inharmonicity connects reasonably with the high bass. Now you'll probably want to go 2-4 notes higher with wrapped bichords to blend the impedance and inharmonicity into the rest of the treble. What happens? You maybe need 0.006" wrap for D-3, and smaller than is available for the next one or three. There's the problem, and the reason this doesn't always work that well, and the reason for transition bridges. The speaking lengths are too long at that pitch for wrapped strings. " Maybe that'll help get your discussion going. ( : Regards, Trent -----Original Message----- From: Erwinspiano@aol.com [mailto:Erwinspiano@aol.com] Sent: Mon 11/22/2004 6:30 PM To: pianotech@ptg.org Cc: Subject: Re: Bi-Chords..... Hey Fast Joe True enough in general except that this bass string maker also does scaling for his own rebuilds. That doesn't say if the scaling program used is accurate or has a tension bias toward conservative tension numbers. Also this a S&S B being discussed & the warts are pretty common knowledge right? My guess is someone with experience on list could chime in about the tensions involving plain wire verses BI-chord wrapped or tri-wrapped string & how the various tensions blend into the plain scale. Sounds like an invitiation huh? Whos got a string length handy? Dale Dale said, I was told by my bass string maker that this spot on both pianos is too long for bichords" Dale, And, of course, these bass string makers are manufacturers, Scale Designers & Rebuilders? B.S. Unless they are in direct contact with each piano of question, they ought to keep that stuff to themselves, IMO! Of course, there are a few string makers that have fullfilled the criteria and can give good advice, but each piano is an entity unto itself, warts and all. The correction of warts is what most of us do. Sheesh! Joe Garrett, R.P.T. Captain, Tool Police Squares R I ****** IMPORTANT NOTICE ****** This e-mail, and any attachments hereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments hereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify me at (312) 207-1000 and permanently delete the original and any copy of any e-mail and any printout thereof.
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