Ron N and list, > > Furthermore, if the >>string offset is kept to 10 degrees, string deformation should not be >>a problem, especially since the string rarely moves at the bridge pin > >once a tuning is stabilized. > >Ron O, > >I let this one get past me, but it looks like something that fits in the >current meanderings, so I dragged it back out. > >My current thinking is that strings never really stop rendering across the >bridge. Any humidity swing will move the string up and down the pin and if >the string is moving vertically on one of it's major friction surfaces, >since the friction at the bridge top is negligible compared to the friction >at the pin, it should move horizontally (render) if a threshold tension >difference exists between segments on either side of the bridge. This >should be happening more or less constantly. > >Ron N I totally agree Ron, and my experience of tuning rear duplex segments bears this out. When positioning rear duplex blocks prior to stringing, small errors will be inevitable. The process of getting duplex blocks set to the correct position (length) always follows a definite pattern. The rear duplex segments must be tuned prior to tuning the speaking length. This is achieved by rubbing the duplex length to lower it or rubbing the speaking length to raise it. If the duplex block is slightly out of position then the duplex segment tension, when in tune, will be slightly higher or lower than that of the speaking length tension. For example, let's assume that a duplex block is a fraction of a millimeter long. When tuning this duplex segment we will need to rub the speaking length to raise the pitch of the duplex length (which originally will be flat since the duplex length is too long). Unfortunately, we will have to rub the speaking length until the duplex tension is raised to a higher tension than that of the speaking length when it is in tune. Therefore, the out-of-position block will have caused us to set unequal tensions either side of the bridge to get both duplex and speaking length segments in tune. During the period between a subsequent tuning, the string will gradually render across the bridge to cause the speaking length to go sharp while the duplex segment goes flat. On the other hand, if the duplex block was short the reverse would occur. Therefore, the between-tuning rendering over the bridge will indicate if the duplex blocks are correctly positioned. I move the blocks until equal tension (and tuning stability) is achieved. This generally takes about six months following a re-string if the piano is regularly tuned in commercial service. Ron O -- Overs Pianos Sydney Australia ________________________ Web site: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au ________________________
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