trichord string splaying

[Overs Pianos]

Stephen,

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, and the other is providing 
sufficient clearance between the unison strings to prevent them 
jangling under heavy playing.

In the high treble there is little likelihood of strings jangling, 
but the adequate-wood-space consideration dictates (or it should) 
that the pin groups are spaced. If one was using a bridge agraffe 
this spacing consideration wouldn't be necessary.

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.

I was called in by the company representative, here in Sydney, to 
trouble-shoot the 'noises' this instrument was making under heavy 
playing. When I return from Rochester, this piano is coming into the 
workshop for a recap in the lower tenor. We'll be spacing the unison 
groups at 12 mm in the low bass (I have been using this spacing for 
my own bridge layouts for many years).

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). The agraffe bichord spacing is 
usually kept at around 5.5 mm so that the unison spacing at the 
hammer head is not too wide. The splaying at the bass bridge should 
be widened where possible to equally-space the unisons at their 
mid-speaking length point. We lay out the bichords in this way, and I 
notice that Fazioli does it too, along with many others from the 
European 'design school'.

There are instances where the traditional way has merit. Splaying 
unisons is one such example.

Best regards,
Ron O.


>What is the "official" rationale for splaying the strings within a 
>trichord at the bridge? or is it one of those little bits of piano 
>folklore that keeps propagating because it's assumed to be 
>"necessary because we've always done it"? It's done even on 
>straight-strung stringbands, as much as to the point of having all 
>strings the same separation at the bridge, like you see on some 
>over-strung pianos.
>
>What dire consequence might result from keeping strings parallel 
>within a trichord? And have these consequences actually been 
>confirmed experimentally or by supposition?
>
>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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OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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