model B wire gauges & string calculations

[Overs Pianos]

Hello All,

Thank you so much for the many replies to my request for the standard 
plain wire gauges of the early Steinway model B. I haven't rebuilt 
any early Bs, so I didn't have a scale on file. With the wire gauges 
filled in, here's a jpg below of the 85-note model B scaling graphs.






Steinway circ 1890 model B scaling graphs

Just in case the above jpg doesn't get through the Pianotech sever, I 
have uploaded a copy to;
http://members.optusnet.com.au/ronovers/1890B.scale.jpg

The scale is not surprisingly quite similar to the 'modern' B. 
There's a gaping tension hole from F21 to C#29, and for the lowest 
singles. No surprises why Ron Nossaman designed a nine note 
transition bridge from F21 to C#29 for the remanufactured model B he 
exhibited at the recent Rochester national PTG convention. I'll be 
doing the same for the 1890 piano if it gets to be rebuilt in our 
workshop (as an aside, several years ago we rebuilt a modern model B. 
Before removing the strings at teardown, I pulled note F21 up to B 
flat #26 - to 41% of breaking strain - just to have a listen. The 
tone was so much improved, and so too would have been the tuning 
stability, had the piano been originally designed with the break on B 
flat #26 at the original #F21's 145 cm speaking length). Look also at 
the Z (impedance) jump between note F21 and E20. This jump can be 
plainly heard in the piano as well. Just makes me wonder how folks 
who claim to be at the cutting edge, and who also claim to be making 
continual improvements, can sit on such scaling problems for over a 
century and pretend that there's not an issue. While it is excusable 
in a 1890 piano, it is now 2006 and our understanding has totally 
changed. Of course, the contemporary industry is plagued with 
similarly poor scales amongst a variety of manufacturers.

I'll include below a small-piano scale graph, taken from one of my 
own scales, for those of you who may be interested, since there has 
been quite a lot of scaling discussion on the Pianotech list 
recently. Without cutting the back-scale short, this scale can be 
squeezed into an upright of just over 130 cm (the "% breaking strain" 
graph is the uppermost one).




An Overs design, Short-piano scale graphs

Just in case the above jpg doesn't get through the Pianotech sever, I 
have uploaded a copy to;
http://members.optusnet.com.au/ronovers/upright.scale2.jpg

As some of you have mentioned on the list (David Love may have been 
one who mentioned it), you can't design with smooth curves on all 
three parameters simultaneously. We will therefore have to compromise 
on one or more parameters depending on our priorities. Over the past 
several years I have chosen to smooth inharmonicity and Z, while 
juggling the speaking length and wire gauges to minimise the 
deviation of percentage of breaking strain at the transitions between 
tri-chord and bi-chord strings, and bi-chord and singles. I regard a 
15% tension change between sections to be unacceptable. It is 
possible to get the deviation down to around 10% without compromising 
on inhamonicity and impedance. In the upright scale shown above, the 
tension falls to around 41% at the lowest treble note, #F33, with the 
first bichord covered note in the bass at around 51%. This will 
result in quite good tuning stability at the cross over. By 
comparison, the Steinway model D has a tension in the treble which 
falls to around 36% at F21 (the lowest treble note), with the first 
trichord covered bass note (E20) at around 51%. So the upright scale 
shown above has quite a bit less tension deviation than the 
industry-standard model D scale. Therefore, all other things being 
equal, one would expect the tuning stability of the above short-piano 
scale to be improved, when compared to that of the industry-standard 
model D. I look forward to the possibility that within 20 years a 
majority of pianos might use scales with deviations similar to the 
upright scale shown above, or better. With longer pianos it is 
possible to design a scale with even less tension deviation than the 
upright scale shown above.

Richard Brekne asked recently about the reliability of calculated 
inharmocity verses the real world measured figures. Yes there are 
differences. In the wound string section in particular, the deviation 
between calculated inharmonicity and real world figures get worse as 
the wrap diameter increases. However, the deviation when the windings 
are small is quite insignificant, so the cross over calculations will 
still be quite close. And this is where it matters most. I don't own 
a Cybertuner, but these devices can measure the real inharmonicity. 
As usual, in uncle Joe G's recent post, he was carrying on with all 
the usual commonsense that he has become known for. Well done uncle 
Joe.

I see Terry F is getting all geared up to do a transition bridge 
which includes moving the agraffe line - good idea Terry, but it is a 
lot of work. I've done a transition in a Yamaha G2 where I moved the 
hammer line to correct for the strike point problems created by the 
inclusion of a transition bridge - the result was good but it also is 
too much work, creating some action geometry issues which have to be 
worked around. When you check enough scales from existing 
manufacturers, including some who claim the high ground, for many the 
strike ratio is already quite varied across the break between bass 
and treble.

By the way Terry, I suspect that the dust extractor you've got might 
be a better unit than many of the other commercially available units. 
Bill's design uses an impeller with backward curved blades. Many of 
the commercially available units use impellers with straight blades. 
Both impellers will work fine while the filters are unblocked. But 
once the filters start to get restricted the backward curved impeller 
will keep pumping relatively well, while the straight bladed version 
will stall. Good design is usable for a lifetime. Trash is trash.

We need to believe that we can make a difference in our own lifetime, 
by not putting our collective heads in the sand. The current 
Pianotech list scaling-discussion would seem to be indicating that 
serious head-from-sand extrication is really happening. Bravo!

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron at overspianos.com.au
_______________________
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