Rescaling

[Overs Pianos]

David, Del, Newton and list,

Del's post was right on the money.

Del wrote

>. . . . . At the other end of the bridge--and here you've mentioned 
>the Steinway B
>which is a good example of the problem--many pianos are designed with a
>tenor section that is simply too short. Take a look at the way this bridge
>hooks back at the low end of the tenor.

Exactly. Wherever the long bridge is hooked back towards the bass 
side of the case, the break has been placed too far down for the 
length of the piano. It is not possible to place a uniform scale 
where designers (or is it piano sales people?) insist on trying to 
make the seven foot piano look like the nine foot concert version. 
The nine foot version has a speaking length of 183 cm at F21 (most of 
the major manufacturers seem to agree on this - baaaaaah). The note 
with a speaking length (on the nine foot version) which most closely 
matches the longest tenor note on the seven foot version is A#26, at 
143.5 cm. It would therefore seem to be, at the very least, sensible 
to break the seven foot version at A#26 (with a speaking length of at 
least 143.5 cm) to ensure that the tuning stability was not inferior 
to that of the longer piano.

>The speaking length is
>'foreshortened in a manner that is appropriate' to quote one early writer.

As Samuel Wolfenden wrote in 1916, but modern designers should know 
better. Why does it take a hundred years for something better to turn 
up? Because the 'major' makers keep pushing the traditional line - 
deliberately stifling change for the better. The 'charge' to 'improve 
the breed' is most certainly not coming from the ranks of the 
established manufacturers. Furthermore, many of the commercial 'want 
to be'-s can do nothing more than assembling their poorly made 
instruments with a grab bag of brand name components (who cares about 
Abel hammers, Roslau wire, maple pinblocks and Kluge key boards, if 
the piano's put together like trash!!!). Name brand components does 
not ensure a quality product. It just fools the fools for a short 
while. In the end, wether the 'new kids on the block' sink or swim 
will be determined by their piano making skills, which is another 
whole issue. Sorry for that minor digression folks.

>With the original scaling, the tension on this string (F-21) is around 115
>to 120 pounds. B-27 just six notes up is strung at approximately 165 pounds.
>  . . . . A better practice is to drop the last few notes off that 
>bridge and install a third
>bridge using wrapped bi-chords. An even better solution would be to make a
>new plate and put about 26 or 27 notes in the bass section and avoid the
>problem entirely, but most customers consider that to be overkill on the
>average rebuild.

Exactly. As I am sure Del would agree, designing a better replacement 
piano would be the way to go. An F21 speaking length at 147 cm with 
21 gauge wire will never work well, regardless of who builds it.

>. . . . . It is to the credit of the
>plate designers that we rarely hear of problems with piano plates developing
>problems as a result of some of the scaling excesses that have gone on,
>still I think it behooves us to be careful.

For many of the pianos with scales sectors of lower tension, the 
plate is often much stronger than required (ie. for strength alone, I 
believe that over engineering the plate is actually desirable for 
tonal reasons - light flimsy plates never seem to accompany pianos 
with good sustaining qualities). I believe one of the factors which 
made the SD-10 into a potentially great piano (it was let down by 
sloppy workmanship) was the generous section sizes of the plate.

Fortunately, many plates have ample plate cross sectional areas to 
cope with altered scaling. But the problem of strike ratio rears its 
head if the speaking length changes are too radical. Recently, when 
we put a tenor bridge into a Yamaha G2 as a prototyping exercise, we 
altered the hammer line by over 10 mm (for the most shortened 
speaking length on the tenor bridge) to keep the strike ratio 
somewhere within the ball park. While it worked very well it looked a 
bit strange. Furthermore, it is not an ideal work around because it 
does slightly effect the action geometry. The better solution is to 
design a better piano with a better scale in the first place, as I'm 
sure Del would agree.

Regards,

Ron O.


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Website:  http://www.overspianos.com.au
Email:        mailto:ron@overspianos.com.au
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