There is a thread on the piano forum where several Estonia owners have similar problems with their instruments. What starts out being diagnosed as a ringing plate strut turns out to be errant vibrations (longitudinal waves).

The thread is a bit long, due to the undying chorus of the "I want to chime it too" crowd. But if you cut through the "Oh, I feel so bad for you and your lovely piano" and the "the company sure is doing you right.." refrains, there are some valuable lessons for us technicians.

If reading four pages is simply too much for you (I can understand) then at least cut to the chase and read page four.


Estonia scaling problem thread

Problem could also be solved with a different brand of string besides Roslau. Sometimes they just are unfortunate and use a bad batch of wire at the factory. Longitudinal waves are more common with wrapped strings than plain wire.

Why arnt new pianos using this stainless steel string throughout? Does it cost a lot more?

Yes, it's more expensive, but that never stopped anyone in the music industry, if it had an advantage (take a look at high-end guitar strings some time).

The main reason is tensile strength. Piano wire is basically spring steel, which has an extremely high tensile strength (300 ksi+). You just can't get there with stainless.

The object of the high tensile strength is higher tension with smaller diameter. If you figure an average piano string of about .030" and holding about 150 lbs tension, then the stress on its cross section is

A = pi * d^2 / 4 = 3.14 * .03^2 / 4 = .000707 sq. in.

stress = F/A = 150# / .000707 sq in = 212 ksi

which is approaching the yield point of the material already. So obviously the tensile properties are being taken to their maximum advantage.

Another factor is its Young's modulus, which is a measure of its elasticity. All carbon steels have about the same modulus (30 Mpsi). Stainless is lower (about 28 Mpsi). It's only about 7% lower, but that could be enough to make a difference. A lower modulus of elasticity means it takes less force to deform it, so stainless is a little more flexible. I'm not sure what that does to the tone.

Don A. Gilmore
Mechanical Engineer
Kansas City

Regarding the pianos in the Estonia thread: I don't think pianos should be sent halfway around the world back to their factory because of a scaling or tone issue, without someone at least trying a different string material. Simply compare the cost and logistics, the "risk" and benefits. Besides, what are they going to do in the factory to fix the problem? Start moving bridges? Hardly.

The question here really is: how do we as technicians deal with obvious scaling problems?

Trying to needle hammers will, at best, mask the "Badness" a little bit. This is an effort to mitigate symptoms, but leaves the problem untouched. The result is mostly unsatisfactory for the piano owner and the technician. I am sure we have all been there.

Enter a wire with different physical properties. Pure Sound has a slightly different density and a lower modus of elasticity, as Don points out. This makes it better suited for lower tension string sections than regular piano wire in many cases.

Many, I would argue most pianos have far too little tension on the low tenor strings. The low % of breaking point drops off in that area and this causes high inharmonicity and poor tone. I was tuning a Yamaha U3, their top of the line upright and I found that the low tenor (plain wire strings) sounded tubby and was almost impossible to tune. Checking with a few different scaling software programs, I was amazed to find that the % breaking strength in that area was under 30%! Many pianos are similar. Restringing these low tension areas with Pure Sound will raise the % of breaking strength, reduce inharmonicity, improve tuning stability, reduce the voicing issues at the tenor/bass break, and improve tone markedly. Note: I am not advocating a shotgun approach here. Each case needs to be assessed individually.

The point of this thread is that many scaling problems on modern pianos can be solved with Pure Sound wire. There are those who proclaim that restringing will not affect any change, and that changing speaking lengths and/or recalculating the strings to include more wound strings in the low tenor is the only way to improve things.

This is obviously not the case at all. Restringing with a different wire is a cheap, non-invasive, 100% reversible measure that we piano technicians should look at more often. It should be one more weapon in our arsenal, so to speak.

I read back a while ago about a patent description of a string winding process that uses a different feed angle of the wrapping to create a uniform adjustable space between the coils. This allowed a wound string to be calculated and manufactured in the upper tenor with more optimum scaling since it could provide for size ranges between wrapping diameters or go below the minimum size limitations of the winding. I always wondered what happened to this process or was it to destructive on a hammer surface acting as a saw.

i posted this in the other thread but thought it applies to this thread also:

Just an update, my L190 is in the process of getting new Pure tone strings and the report is that it sounds very good, even better than the Roslaua (sp) strings. Piano is due back to me in about 10 days. I was told they noticed kinks in the strings upon removal and they think the strings might have been damaged from a leveling machine at the factory? Does this make sense? But regardless of the reason it will be nice to have it fixed.

Mark...

Jurgen,

Would it be possible to use Pure Sound wire as core wire for a bass string? Do you know of anyone (James Arledge comes to mind) who has tried it?

Because of the nature of the wire, there are a few "tricks" which need to be observed when using Pure Sound for bass strings.

At present, I don't think James Arledge is making bass string with Pure Sound cores. Bass strings using Pure Sound are made by several European suppliers, including Heller, who make exceptional strings.

I understand that sometimes these strings are used in the very lowest bass section in modern instruments, to raise the %BP and reduce inharmonicity.

Gregor at HellerBass is making bass strings with Pure Sound wire core for the French instruments that are being restored in France. This has been going on for some time. From what I am told it is working out quite well.
I purchased a set of bass strings for my Blüthner from HellerBass. Best set of bass strings I have ever received from any company that makes them.

You are lucky to have Estonia respecting warranty to this extent. Yamaha did not take same approach for my S4. I nevertheless am in the process of ordering Puresound ones too. I ordered 35, 37 and 38, the really offending keys.
Thank you for reporting back.

antonis