---------------------- multipart/alternative attachment Roger Jolly wrote: > Hi Richard, > On the subject of V vs U with regards to termination > bars. Having watched plates being dressed in several piano factories, the > quick way of shaping these bars is with a file or small grinder hence the V > shape. > All too frequently the terminations closest to the plate webs are poorly > shaped, and is clearly in evidence by the amount of V bar noise we fine in > this area. > > In theory two perfect circles touching will give an infinite contact point, > ( just imagine they don't touch, grin.) > > I have asked two major manufacturers why they don't shoe shine the pressure > bars with emery paper to obtain a clean radius, the answer in both cases > was that it is not necessary. I'll take this to mean that the extra 1/2hr > of work cost money. In one plant the concert grands had the pressure points > polished to a nice round radius, hence contradiction their previous > statements. > The other plant, the concert grands had case hardened termination pieces > with perfectly formed radii. > When ever I restring, I'm always careful to get as clean a polished U shape > as possible, and tend to believe that there is less friction, and cleaner > and more consistent termination. > Grin.. thanks for the informative, to the point reply. Good to know we are talking about two different profiles here, a "V" versus a "U". Now we are getting somewhere. I understand that there are differing opinions about each. A couple points to keep clear between us before going further. Are we in agreement that a "U" more closely conforms to the Clamped termination point, and a "V" more closely conforms to a "pivot" termination point ? Are we in aggreement that the "V" profile has a nearly (and I mean very very nearly) flat top(approximating a \_/ shape), edges just barely brushed off, and that a "U" has very noticable rounding off the edges(approximating a circle) ? If so then there are some physics (contended) that need to be answered beyond what a static load dispersion explanation can account for. 1. the difference in inharmonicity 2. the difference in string stiffness 3. the difference in how the load (string at tension) behaves at the termination point. 4. the difference in type of wear leading to string buzz against the termination point. 5 of less concern I would think... the rate of wear resulting. and of course how significant this all is. Opinions are one thing, experience better, but subject to personal prejudice, hard facts are really what I am looking for. (grin,,, and not only here on this list) A couple points from Ed's book are interesting in this regard. If I may quote.. "Some makers install hard inserts as the termination surface on the capo or V-bar. Since they found that this led to premature string breakage, they later compensated by broadly rounding the termination surface of their hard metal inserts. Although this reduces string breakage, it causes the strings to buzz against the termination point when the piano is played loudly." and then: "The ideal capo bar contour is a definite "V" shape with the contact point of the wire held to a 0.5 mm width. The angle of the V shape should be such that the string on either side of the capo bar is at no time able to vibrate into the bar. Keep in mind it is not the grooves that buzz, it is the contour that lets the grooves buzz. also "Even if no buzzes are present (context... new piano newly shaped U contour), the sustaining quality of the tone will be inhibited right from the start if the string contact area is too broad, since the pivot effect of the termination is inhibited. This will cause the wire to fatigue prematurely, since it is forced to bend instead of flex at the forward termination point." One thing he makes a big point out of.. A hard termination surface forces the use of the "U" profile, due to the string breakage problem. If you deal with hard termination surfaces for the most part, then it is no small wonder you prefer the U profile. > > V is time saving, U cost money IMHO. Hmmm... as Ed describes his proceedure, the precise "V" at a uniform 0.5 mm width is pretty time consuming, at least by hand / shop tools. > > > Harold Conklin's case hardened steel termination pieces, have about 10 to12 > times radius vs 6 or 7 this I belive was done to control the amount of > power in the forward duplex, and the difference in sound absorption with > steel vs cast. The affect on the duplex makes sense, if we agree that the wider and rounder the termination point is, the more this inhibits the power of the forward duplex. This "power" can also be controlled by the tuning of the duplex scale. I have done this as per Eds' specifications several times and it never fails. A non harmonic duplex (ie tuned to a triple octave and a second above the fundemental, or a triple or double octave and a 6th) allows for plenty of duplex power, without robing energy from the fundemental. Still.. I would like to read Conklins material on this.. I dont think its part of the Askenfelt lectures is it ?. If not can you suggest a place to find any of his written material on this ? > > > More mud to cloud the waters. grin.. Mud again... whewww... LOL. > > > Roger > > Roger Jolly > Baldwin Yamaha Piano Centre > Saskatoon and Regina > Saskatchewan, Canada. > 306-665-0213 > Fax 652-0505 I wonder Roger, have you ever tried Ed's proceedure ?.. If not.. find a good quality grand sometime that you know has a soft termination surface and give it a try. Make sure and detune the deplex as he says as well. The surface has to be soft tho or it just wont work. If it is tho.. all the plusses of the pivot termination with regards to sustain, inharmonicity, and string stiffness really show their stuff. I have one I did 15 years ago. Still no buzz, still clear as a bell. Minimum of capo bar wear, just the nice very shallow small round channels you have to expect. Still, I am searching for answers, good ones so I thank you for your post, and would very much like to hear your comments on the quotes from Ed's book above. Richard Brekne I.C.P.T.G. N.P.T.F. Bergen Noway. ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/8f/d7/fb/cf/attachment.htm ---------------------- multipart/alternative attachment--
This PTG archive page provided courtesy of Moy Piano Service, LLC