Hi Folks... found this while dinking around in the archives. Enjoy RicB Baldwin Termination Bars, H. Conklin Michael Wathen 556-9565 Michael.Wathen@UC.Edu Thu, 01 Dec 1994 11:46:00 -0500 (EST) Previous message: Climate-control temperature FX Next message: Climate-control temperature FX Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] -------------------------------------------------------------------------------- Here is the a Post for our group that was submitted to me by Harold Conklin. Harold designed the SD-10 and The SF-10, some other grands, and the model 6000 Concert Vertical. He contributed to many improvements that were incorporated into the entire Baldwin Piano line. He was the inventor of "Synchro-Tone" (tuned longitudinal mode) strings, the "acujust" vertical hitch pin, and other piano-related inventions for which more than 15 U.S. and foreign patents were issued. Many of these inventions still are used in production pianos. He left Baldwin in 1986 and has no present connection with the company. As a sort of disclaimer, he adds, that what he says may not necessarily agree with their present technical positions. His words follow. If a piano designer attempts to tune the fundamental frequencies of the treble counterbearing string lengths (the string lengths between the capo bar and the ridge on top of the tuning pin panel) to frequencies of partials of the speaking lengths of the string, the result will likely be unpleasant noises ("zingers"). The "unpleasant noises" come from beats between the excited resonant frequencies of the short counterbearing string lengths and the frequencies of those speaking length partials that are near in frequency to the counterbearing length frequencies. In casting piano plates it is impossible to control the counterbearing lengths closely enough to end up with the counterbearing lengths tuned zero beat to partials of the speaking lengths. Therefore, in order to avoid "extraneous" noises due to beats, it is desirable to dimension the counterbearing lengths so that their fundamental frequencies will lie between two speaking length partials and will be separated from the nearest one preferably by at least a few hundred Hz. It is possible to do this with plates of conventional design by careful positioning of the counterbearing ridges on the casting pattern, and use of careful casting techniques. To provide a long-wearing termination that does not change its shape and to control closely the counterbearing lengths so as to avoid the above problems, later model SD-10/SF-10 instruments used an individual termination bar for each treble note. By carefully selecting termination bar dimensions it was possible to achieve good results by using only two different types of termination bar (Type I and Type II). The only functional difference between the two was in the length of the counterbearing portion. Only two Type II bars were used, the other 33 bars being type I. These individual termination bars were precision steel castings that were hardened (harder than piano wire) for long wear without changing shape. Steel has lower internal losses than cast iron and gives improved tonal duration. After hardening, the bars were plated with electroless nickel, used as a "solid lubricant" to produce a surface on which piano strings can move with the right amount of friction to provide stable tuning, but not too much friction, which might cause excessive string wear and difficult tuning. Before the initial stringing operation the bearing surfaces of each bar were to be covered with a light coating of petroleum jelly (Vaseline). this treatment should be repeated before any subsequent re-stringing of these instruments. It should never be attempted to file or re-shape the precisely cast string-bearing surfaces of these parts because the electroless nickel plating would be damaged. The "duplexed" portions of the strings (between the bridge and the hitch pins) operate under quite different conditions than the "counterbearing" portions discussed above because the coupling within the string between the duplex length and the speaking length is much less direct due to the use of a pair of deflection points (two bridge pins) to terminate the speaking lengths, instead of just one (the capo bar). Consequently, no undesirable effects result from tuning the "duplexed" portions near to the frequencies of speaking length partials. In fact, an enhancement occurs which increases the apparent duration of the upper treble tones. However, when the lengths between bridge and hitch pins become longer than about four or five inches, the duration of their own vibrations can become undesirably long, and may require a damping means such as muting tape. -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html http://www.hf.uib.no/grieg/personer/cv_RB.html
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