Speaking of mass loading (and maybe a bit of stiffness too), I recently rebuilt a 1917 M for a customer who did not want to change the board. It was marginal but holding together. Somewhat percussive sounding in the treble with 8-9 seconds of sustain at A6. Since the plate seemed to dip in the capo section and along with it the bridge height and the bearing, I decided to increase the bridge height through the capo section by 3 mm from 27 to 30 mm. It created a bit of a step underneath the strut at the capo/agraffe break but recapping the entire piano wasn't an option. It required shimming the aliquots up to adjust the bearing and I did remove all bridge pins, recut and renotch and reshape the capo bar (standard treatment) and increased the bridge pin size from #6 to #7 in the capo section. Now that the piano is strung I'm pleasantly surprised at the improvement. (BTW, I did not do an epoxy treatment on the board). The sustain in the lower capo section increased to about 12 seconds at A6. There doesn't seem to be any problem with the transition between the agraffe section and the capo section. I did rescale the piano by overall and change the speaking lengths in the capo section where I did the new cap. Anyway, I'm wondering if others have done similar things with similar outcomes or found that bridges below a certain height simply don't have enough mass without some help. Further, with a certain minimum bridge height does mass loading become unnecessary? I've often wondered if the early Steinways with bridges under 30 mm in the treble (and sometimes well under) don't compromise those areas by virtue of inadequate height and therefore both mass and stiffness to begin with. Moreover, is there what one would consider an ideal bridge height? BTW Ronsen Bacon hammers with plenty of power (after a more refined filing in the treble) and warmth! No lacquer, no plastic! David Love davidlovepianos at comcast.net www.davidlovepianos.com
This PTG archive page provided courtesy of Moy Piano Service, LLC