Yardarm103669107@AOL.COM wrote: > In a message dated 3/27/2001 1:40:18 PM Central Standard Time, > Richard.Brekne@grieg.uib.no writes: > > << My own experience tells me that short, detuned front duplexes, > combined with a less then knall hard sharp and thin capo (0,5mm flat topped) > works best both as a precise termination, and for clear sound with minimal > leakage through the termination. I notice no string buzz after many years use > when this has been done carefully, and I have measured lower inharmonicity > (if > this is desirable for some reason) for this termination vs fat and round. > Seems > to work best on low tension scales but I have nothing to support that with. > >> > > In reality, though, the string begins to cut the surface of the capo as soon > as any considerable tension is put on the string. Through simple surface > compression to a point of stasis (generally about 1.2mm) and through wear > (tuning, which creates a somewhat more rounded shape), starting with a > somewhat thinner more rounded shape, or a fatter more rounded shape, or a > thin flat or a fat flat shape, the actuality of the worked material is that > it reaches a point of stable length pretty quickly. Not hundred percent sure I follow you here... Seems like the main thrust of what you are saying is that no matter what you start with the string will wear the capo to about a 1,2mm wide surface area contacting the string. If so, all I can say is that this is not in my experience. I can point to a couple hundred examples of a Jacob Knudsen (uprights) pianos made from the early 60's to the mid 70's where the "V" bar is very very sharp, certainly less then 0.5 mm wide... probably closer to 0.3mm.. suprisingly thin. Its flat topped and the sides angle off at a very mild angle.. I could guess around 20 degrees from the normal (total angle of 35 - 40 degrees). The strings deflect to the pressure bar at just over 10 degrees. Now these are 40 + years old and there is so little incidence of grooving its ridiculous. I have 7 of these at the University and they are tuned 4 times yearly and have been since new. The V bars are really clean I can tell you. I guess I will have to contrive to take some pictures of these and post them. One other thing, when I say flat top... I mean that very flat.. the edges are just smoothed off (not really rounded). > Preferable to go with thinner more rounded in my mind to avoid wire fatigue at the corners of a > flat edge. We may or may not be saying the same thing here.. depends on how rounded you are talking about. > Also, in "annealing" (generally air hardening), the outer surfaces > of the casting cool more rapidly and become more brittle than the inner > material. There is a thin surface then on the capo which will cut more easily > than the middle and should be cleaned away on the capo to get to the harder > surface. I have always been told to avoid taking away this thin surface, so I have tried to do so. I have never hardened any capo or V bar, but rather shaped as described and detuned front duplexes. Pianos I have followed through the years exhibet no problems with string noises relating to the capo / duplex, and have minimal if any significant grooving. In any case what grooving there is hasnt caused any string noises. > Does this gibe with your experience/knowledge? Knowledge is such a troublesome word...grin.. For all I know J.C. coulda come from Mars. That being said my experience is as I have described it. The most sensible argumentations I have heard on the subject (to my mind have) have come from Ed McMorrow, Ron Overs, and a fellow named Kevin Gouldman. Kevin takes a more neutral position as I understand it, saying it all depends on what you are trying to accomplish. In anycase, with mild deflection, short distance between the termination and the counterbearing, and this thin and not harder then neccessary termination,,, the termination holds up very well indeed..... in my experience that is...grin. > PR-J -- Richard Brekne RPT, N.P.T.F. Bergen, Norway mailto:Richard.Brekne@grieg.uib.no
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