Dave: >I read through the responses rather quickly, but I think most or all >of them addressed the issue of the contamination, and not the >inherent tuning instability you noticed. Hmmm. Took the words right out of my computer. I was just wondering the same and writing about it when your email came through..... There seem to be two separate issues in Andrew's original question. The one about migrating gunkie stuff has been discussed most in the followup posts, but the other one about low friction has only had a few comments. This is a Catch 22.5 maybe, at least with conventional piano design. You want to minimize friction to get stable unisons without busting your fingers pounding. But not too much or you risk instability..... Andrew: >When I say low-friction, I mean I can put my little hammer vertical >on a pin and walk a unison above and below tune without stressing my >pinky. 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. Stephen -- Dr Stephen Birkett Piano Design Lab Department of Systems Design Engineering University of Waterloo, Waterloo ON Canada N2L 3G1 tel: 519-888-4567 Ext. 3792 Lab room E3-3160 Ext. 7115 mailto: sbirkett[at]real.uwaterloo.ca http://real.uwaterloo.ca/~sbirkett
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