sanderson Bass strings/scale

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: November 29, 2001 6:54 AM
  Subject: sanderson Bass strings/scale



    Having too much tension in a bass scale will choke the sustain in =
any piano. Having too much tension in the bass or  treble cannot only =
change the tone color but choke it as well.=20
    When I spoke at length with his shop foreman he said that the wire =
size on noter 88 had gone from a no.13 to a 14 size wire. That's a huge =
jump in tension. The 2 top trebles apparently received this same whole =
size increase and was the most choked in both pianos.=20
    I explained to them , as Del and Rons have stated many times, that a =
rib scale is designed for a particular string scale. Yes, it is possible =
to make string scale changes on an existing board. Many of us have done =
it but, if the tension changes are too great the tone and sustain will =
be altered in a negative way ,ask me how I know.  Scaling is a wonderful =
tool  but some times it's better not to mess with success and the stwy O =
doesn't , I.M.H.O.,need drastic changes in the stringing  scale.   =20
While it is true that the stringing scale and the soundboard/rib scale =
should 'match,' within the parameters of an existing piano like the =
Model O, the stringing scale requirements aren't going to change all =
that much between a compression-crowned soundboard and a rib-crowned =
soundboard. At least not if you're sticking to the original rib =
dispersion. In terms of overall tension you're going to be limited more =
by the structural characteristics of the plate. At least you should be. =
Depending on the characteristics of the specific piano, the Model O will =
have about 5,700 to 5,900 kgf (approx. 12,500 to 13,000 lbs) of string =
tension through the tenor section. Now, this ranges from a low of about =
52.2 kgf (approx. 115 lbs) to a high of about 77.2 kgf (approx. 170 lbs) =
and it can certainly stand to be evened out. But, when you're all =
finished with your nice new scale, you shouldn't be all that far from =
the overall stress level the plate had on it originally. You can =
generally get by with increasing things a bit through the top two =
sections since most plates are considerably over-designed (on purpose) =
up there but It's best to be some cautious through the bass and tenor.=20

I know nothing of Sanderson's scaling priorities, but I have looked at =
one or two Steinway scales over the years. As you point out, there is no =
single Model O scale. It varies with the piano. In general, however, the =
Model O has a relatively low tension scale. This is especially true in =
the top section. It is a scale that can, indeed, stand some improvement. =
In my computer I have Model O scales with C-88 as short as 45 mm and as =
long as 50 mm. In my opinion, all of these are too short; hence, the =
tensions will be lower than I would like.

However, putting fat strings on an excessively short scale is not the =
solution. I have tried scaling these starting with #13 1/2 wire at C-88, =
but wasn't really satisfied with the results, especially on those pianos =
with shorter speaking lengths. No, it's not just the tension and it's =
certainly not the inharmonicity. This wire is simply too stiff for the =
lengths of these short strings. The pretty, straight line in the graph =
does not necessarily translate into musicality.=20

There are two possible solutions for these scales that do work. The =
first, and easiest, is to simply remount the bridge back slightly, =
giving a C-88 speaking length of 52 mm. This will also increase the =
length of the rest of the tenor strings but, of course, this is also =
desirable through the top two sections. (That whole top section is =
really quite short.) The additional length won't have much effect =
through the tenor section. In some pianos this may require a bit of =
grinding on the plate hitchpin panel up toward the top longitudinal =
strut.=20

The second, and more difficult, is to make a new treble bridge, setting =
C-88 to 52 mm and laying out the rest to a log pattern through the top =
two sections. (Since it is not possible to end up with a true =
logarithmic scale in most of these pianos, I call this a SemiLog[tm], or =
S/Log[tm], scale.) This will lengthen all of the strings through these =
sections and will greatly improve the tonal performance through the =
killer octave region as well as through the upper treble section. Even =
with a softer hammer both sustain and power will be improved. This will =
definitely require some grinding on the plate, though not enough to =
effect its strength in any way.=20

Obviously, in both cases it will be necessary to either relocate or =
replace the back aliquot bearing bars. I don't consider this to be a =
problem, others might. I am happy enough with the improvement in =
performance to not worry about the loss of a questionable feature.=20


    I have been routinely rotating the top of the bridge back when =
installing a new board to accommodate a speaking length of 2". This =
small change makes a modest increase in tension using the original scale =
and improves power and projection in the top octave or so.=20
As per option 1, above. This certainly helps, but I found that the real =
problem was the first octave in that top section. Hence the switch to a =
new S/Log bridge.


    All that to say that changing  to higher scale tension in this case =
had a compounding negative consequence because of the excessive tension =
of the new Sanderson scale.=20
As I said above, I don't know anything about Sanderson's scaling =
philosophy, but I suspect there is more to this than higher scale =
tensions. Folks dabbling in piano rescaling often tend to focus on one =
or two parameters and sometimes overlook the big picture. For many years =
I refused to give classes on 'rescaling' because the principles were so =
often mis-used. In this case, even though the numbers in the spreadsheet =
looked good, length/diameter ratio is going to pretty low.



  Anyway a cut to the chase. The client restrung both "o"s with mapes =
Bass strings and original scales. The sustain , power and sonority  =
returned . From what I understand the client had a  discussion with Dave =
S. who was Quote rude and unprofessional. He did however agree to refund =
his money for strings. But wow the loss of time and labor cost. My =
client said that this was obviously Not the first time that Mr. S. has =
received these complaints=20
  Is this anybody else's experience?=20


Scaling by remote control can be a tricky thing. While I do some =
rescaling work and redesign work for other rebuilders, I really do =
prefer to know the person I'm working with. While most of my experiences =
have been good, there is always the odd exception. It is very easy to =
mis-judge technical capabilities and expectations.=20

The scale I'd recommend for an O with an original soundboard and bridge =
is not the same one I'd recommend for an O with a new board and a =
relocated bridge.=20

Del

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