Stephen - At three days without posting, I know this thread seems to have gracefully gone it's way, but I'll try, nevertheless, to cobble together the various thoughts I had had. Your hypothetical piano questions address tunability, tuning stability, and the effect of bearing point friction upon the wave form and wave duration. What is it you are trying to accomplish? The Boston model that inspired this thread would seem to have some significant design issues in this area, but is the implication that the basic concept (pin block, tuning pin, etc.) is inadequate? Tunability would depend upon the level of refinement of the mechanical system that would control the tension. I don't have the information readily available that correlates tension with frequency, but such a system would have to be able to acheive, in a linear fashion, what we do with the combination of turning the pin, flexing the pin, test blows, etc. Tuning Stability - I don't remember if a recent (?) past thread ever determined exactly why strings go out of tune. Is the assumption that, by reducing friction at bearing points, the tension of the various lengths will be more equalized than what we generally achieve, and thus, less prone to change? What tension values (or range of values) would you insert into a formula that described the tension relationships between the various sections in a stably tuned string? How much variation in tension would be viable between the front section and vibrating section; between the latter and the back length? How do you measure that tension? Does the friction at the agraffe and bridge pin have any role in the definition and containment of vibrational energy or is that solely a function of deflection? Why do you say that the longer the non-speaking length, the better? Why, from what's been discussed, do you find "same total string lengths within trichord" to be advantageous? David Skolnik At 10:33 PM 10/9/2005 -0400, Stephen Birkett wrote: >Let's take another of my favourite hypothetical pianos and say friction >was close to zero at all bearing points by some magic (no gunk). It seems >to me that this would be desirable provided there is no inherent >instability in the front or back lengths, e.g. flagpoling, fiesty pins, >unpredictable friction between pin and pressure bar, and so on. Without >friction at the v-bar (and bridge), any instability in the non-speaking >portions of the string will bleed through to the speaking length. >Conversely you need some friction (aka pressure bar bearing angle) to >protect the speaking length from instability in the front length, however >it may originate. Add to my hypothetical piano with friction-free bearings >a perfectly solid front and back length. Can anyone see a problem with this? > >To deflect one possible argument against, namely that the strings would be >unstable during hammer impacts, I would respond that: (a) during the >impact the string is not vibrating as a standing wave anyway, so >instability of tension is irrelevant, (b) the conventional configuration >traps any change in tension in the speaking length, therefore the effect >from hammer impact is greater than it would be with my hypothetical piano, >since changes in tension from the piano will operate over the entire >string length, including the front and back lengths, so they have less >influence on the speaking portion. In fact, from (b), the longer the >non-speaking length portions the better, contrary to conventional wisdom. and >So do you (others) agree that it would be advantageous as proposed: >"friction free" bearings, solid stable front and back lengths, and same >total string lengths within a trichord?
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