Such a long post I usually never read for I thought it was billbrpt! So, what's the answer to Don's observation about the right string being sharp on both grands and upright tri-chords? I still say it's the angle of the plate. On the other hand, vote for me! I'll find the answer!!! John L. Oakville >>The sharpness of the tri-chord's right string at this time of year has to be >>on account of the shorter distance from bridge to plate. If there's a tail >>end duplex and the right string is sharper than the left, I think I'll go >>into politics. >> >>John Lillico, RPT > > >Everything in a piano moves all the time, so anything you could name will >be contributory in some direction in some infinitesimal manner. The bulk of >this stuff happens because the string friction at the bridge is so much >higher than at the aliquots, V bar, and counterbearing bar. The bridge is >the dividing point. With any bridge height change relative to the plate, >the total string length behind the bridge (rear bridge pin to hitch) is >shorter, and changes in tension more than the total string length (front >bridge pin to tuning pin) in front of the bridge. In a unison, the shortest >of the three lengths behind the bridge changes most among those lengths >behind the bridge, and the same happens among the lengths in front. When >the tension differences in a single string are far enough apart on either >side of the bridge, the friction across the bridge will be overcome >somewhat and enough string will render through to get those tension >differences close enough that the bridge friction will again hold them. The >shorter the back scale, the more the front tension will change with a given >bridge height displacement. Also, with identical back scale lengths within >a unison, the string with the shorter total front length will change >tension in that front length more than the string with the longer front >length. It's quite possible, depending on where in the humidity cycle the >piano was last tuned, how nearly equalized the tensions were between front >and back scales when the tuning was done (which you can't know), where in >the cycle it is now, and where in the cycle(s) it has BEEN since it was >last tuned, for the unison to be in tune, right string flat of center flat >of left, right string sharp of center sharp of left, or anywhere from here >to there. > >There is absolutely no way to make any sort of reasonable assessment of >what's happening in any specific instance with nothing more to go on than >pitch, temperature and humidity records. Just as well vote for the guy with >the coolest looking suit - as long as you're going into politics. Another >little tip from your Uncle Wookie. > >Or maybe it IS the casters or fallboard knobs. I'll leave it to Jim B to >soak us up some knobs and report back later. > >Ron N
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