---------------------- multipart/alternative attachment Hi Ron, Thanks for the reply. I should have remembered that you have been doing work in this area as well. I have the same question as Fred. Don > Subject: > Re: Capo bar revisited > Date: > Thu, 29 Jan 2004 08:29:45 +1100 > From: > Overs Pianos > To: > College and University Technicians > References: > 1 > > > > Hi Lance, > > Thanks for the update and sorry to hear it did not work out to your satisfaction. It is clear from previous discussions > that there is no guarantee all the cures mentioned will work. Regarding the capo, sometimes we get lucky, sometimes > not. I have been leaning towards the school of thought that suggests good tone can be achieved without the front > duplex section ringing at a higher harmonic of the speaking length. Yes, that would mean major rescaling for Steinway, > etc. (Not likely to happen :-) It seems to me that a lot of problems could be solved by this design. Pardon me if I'm > incorrect, I believe Del has proposed this on the lists and in the Journal. > > Don > > > Don, Lance and all, > > If you measure the front duplex lengths relative to the speaking lengths, of Steinway and Yamaha grand pianos in > particular, you will find that both have attempted to set the front duplex lengths to a harmonic length of the speaking > length, ie. a 1/2, 1/3, 1/4, 1/5 . . . 1/10, 1/11 etc. This practice is a sure-fire way to allow for the production of lots of > string noise. Furthermore, most manufacturers do not harden their capo and duplex bars to prevent the strings from > deforming the bar profiles - if indeed they bother to shape them properly in the first instance. Yamaha harden their capo > bars but leave the front duplex bars soft (we know this because we have reshaped several late Yamaha piano capo bars > and front duplex bar sets, and their capos are quite hard when removing metal with the die grinder tungsten burrs). Both > capo and front duplex bars are capable of producing noise. Steinway Hamburg claim to be hardening their capo bars with > a laser treatment, but an inspection of any modern Hamburg piano will reveal that their bars are being deformed very > nicely by the piano wire, regardless of their claimed hardening process. When we harden the bars of our pianos there is no > deformation of the bar from the string. Indeed, the strings can be aligned with ease throughout the service life of the > piano, since they don't cut grooves into the bars as they will when the bars are too soft. > > I know that Mr McMorrow is not in favour of hardening capo bars, and I should like to discuss this matter with him at > some time should the opportunity arise. But we have found that when hardening is combined with careful shaping of the > bearing surfaces and a deliberate detuning and shortening of the string segments, the result is highly satisfactory. > > One disadvantage of hardened bars is that the tuning pins fields must be aligned properly to the speaking lengths > segments, to allow the strings to run straight from the tuning pin through the various string segments. If the string > segments are not in line there will be a tendency for the strings to migrate along the duplex and capo bars as the piano is > tuned. Thankfully if the bars are hardened the alignment process is simple, but its annoying if the strings continue to > wander throughout the service life of the instrument. > > I have proven to my satisfaction that tuning the front duplexs to their respective speaking lengths is a recipe for disaster. > > I have conducted experiments whereby a moveable front duplex is set precisely to a harmonic of the speaking length and > it definitely causes those levels of string noise which many of us have come to detest. After moving the front duplex to > detune it from the speaking length the noise disappeared. However, if the chosen duplex length is around 40 mm it will be > noisy no mater where it is positioned. So the typical grand piano front duplex lengths chosen by many manufactures is a > contributing factor to the production of string noise. Notice that you rarely hear string noise from upright pianos, yet > there is often a short string segment between the V bar and the pressure bar which is undamped. The short, typically > around 20 mm, string segment of the upright piano tends not to produce string noise because it is too short to be active. > In the grand piano, with front duplex lengths which are often up to 40 mm or more in length, noise is almost guaranteed. > > Our approach to this problem in recent years has been to remove the original front duplex bars with an angle grinder, and > manufacture a new set of bars with a small radius rounded apex which is hardened to prevent deformation. After > measuring the speaking lengths of the string sections concerned we enter the information onto a spreadsheet which is > designed for the purpose, choosing the shortest possible de-tuned front duplex lengths for each note. We then move to the > plate which has been previously levelled (if necessary, with motor-vehicle body filler) to accept the new set of duplex bars, > to determine the height of the duplex bars in their new positions to establish the correct height for the bars (which will be > tapered in height along the length of each bar) to allow all strings to run to the capo at the desired string angle. We set the > string approach angle to no greater than 15 degrees or less than 12. A higher approach angle will tend to produce less > string noise, but any angle over 15 is likely to allow the small radius hardened capo and duplex bars to act like string > cutters, and will shorten the string service life. We have found 15 degrees to be the practical maximum angle which will > allow for a satisfactory service life with the bar radii that we use. Of course you could use a larger bar radius with a higher > string approach angle and that would be fine, but with the small radius bars we use 15 degrees is the maximum approach > angle. > > For those of you who haven't heard a piano with a deliberately de-tuned hardened small radius capo and front duplex > system, please link to the mp3 sound samples of our piano no. 3 online at; > > http://overspianos.com.au/samp.html > > The treble tonal clarity of this piano is not a fluke. All our pianos (including the rebuilt instruments) have the same > characteristics. It is satisfying to have found that it is possible to put the problem of string noise behind us, provided that > we are prepared to step beyond slavishly following that standard which was set over a 100 years ago. > > Ron O. > > -- > > OVERS PIANOS - SYDNEY > Grand Piano Manufacturers > _______________________ > > Web http://overspianos.com.au > mailto:info@overspianos.com.au > _______________________ > ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/caut.php/attachments/e7/45/a5/d6/attachment.htm ---------------------- multipart/alternative attachment--
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