Thanks to Ron and others who responded to my musing: >There are two design considerations which justify splaying trichord >string groups. One is the provision of adequate support wood in the >bridge cap, as Conrad mentioned, In my application there are agraffes on the soundboard end. These eliminate the need to splay trichords to improve bridge pinning, but complicate the anti-jangling splaying layout into the tenor. On the latter point.... >and the other is providing sufficient clearance between the unison >strings to prevent them jangling under heavy playing. This is what I was thinking to be the rationale behind the practice, but I'm not entirely convinced in the causality...... >In the tenor, there is definitely a risk of the unison strings >jangling under heavy playing if the string-to-string clearance is >insufficient. I know of two examples of grands around six foot which >have low-tenor string spacing at the bridge of 10 mm (centre to >centre of the outside unisons). Both of these pianos have >hockey-stick-tenor scales which make the risk of jangling even more >likely as the tension falls towards the break. Playing a note around >B27 heavily will cause the unisons to jangle. A local example of one >of these pianos which is quite new, is undergoing torture at the >hands of an up-and-coming young lady who looks destined to have a >performance career in front of her. My Steinway S splays no more than 10mm in the bass and doesn't jangle. And over-strung modern pianos do seem to vary quite a bit in the amount of splaying. Of course into the tenor there is all that real estate sitting there to splay in, which isn't available on a straight-strung. I've seen biggie ca.1900 straight-strung grands with no splaying at all. With 13mm trichord centre-to-centre spacing the maximum splaying possible at the bridge gives 9mm across the outside strings in a trichord (if all wires are evenly spaced at the bridge). I've not come across one of these straight-strung beasties that jangles, so I wonder if splay-less string spacing is really the culprit if jangling is going on. The largest excursion of the string occurs during impact, which is before the onset of the note, and subsequently excursion is quite a bit smaller. It's possible that jangling may be caused by impedance problems at the string-bridge end, causing wierd phase changes and clashing elliptical paths of the individual trichord strings. If a suitable jangling splay-challenged patient were available in Rochester this could be examined with high-speed imaging. Before re-pinning the piano you mentioned, Ron, you could experiment with some pitchlocs and see if the jangling disappears....these change the phase behaviour of individual strings. If the jangling is eliminated it might be that increasing splaying may be a bandaid solution that happens to fix the problem. Can't help thinking about those biggie straight-strungs that have no splaying at all. My design being straight-strung it raises the issue. >Unison splaying is also common in the bass bichord-string section >for the same clearance reasons as in the tenor (remind of this at >Rochester Stephen, and I'll point out a couple of observable trends >in the bridge pin line as a result). Looking forward to meeting you in Rochester Ron. Stephen
This PTG archive page provided courtesy of Moy Piano Service, LLC