Check this out

I found this yesterday while tuning.

Plate problem

Those look more like scratches from some tool used on the strings rather than fractures. There is no reason fractures would follow the line of the strings.

grey iron plates are a difficult part. They need to be cooked while cooling ( a second time) to lessen inner stresses due to the different speed of cooling between small and large portions.
Then if some stress is left the material can be brittle and react to a small stress. I have seen pianos bowed by the tension of the strings. Not sure all plates can stand a too light bracing.

look like cracks, to me, but may be only in the undercoat of the gold paint .

Again probably a Steinway I suppose

I have seen a lot of cracks in plates, but non which were straight as a ruler. It doesn't makes sense that they would be, given the structure of the material. Judging from the photos, to me it does not look like a plate problem.

Dan, I'd bet my bottom Dollar (if I had one, that is) that those are simple pencil lines on the plate finish. Methinks some kid had some fun running a pencil between the unisons. I'd take a new, soft, clean eraser to those lines and see what happens.

$0.02

While I was there I took a pencil with an eraser on the end and could not remove the marks. I was able to fit the point of a compass into the line on the left.

This is not a Steinway instrument and the manufacturer is not important. The piano is from 1996.

I am going back for a second look next week. Indeed I thought this was unusual, straight lines and all of the rest that has been mentioned.

Weird, for sure. My hunch would be that the piano will live out a normal useful life and die from worn out parts, though. Even if the cracks are structural, it is the ideal direction to have a crack. A crack perpendicular to the direction of stress would be critical.

It will be interesting to see what you come up with on further investigation. X-ray would of course be the ideal diagnostic. Lacking that, I would contemplate actually drilling a small hole in the line and seeing if there was any continuity below the surface.

It is unusual to see cracks lined up and centered within the strings like that and also so straight. In the past as a machinist I have used low viscoscity dye penatrant and developer that is made for finding tiny cracks in metal parts , so there really is no need for x-ray/ magna fluxing ect for this stuff. Sometimes castings get cooling cracks that are only on the surface and don't go too deep, but these typically show up in the areas that cooled the quickest, out near the edges and corners.

In the bottom photo, there seem to be three lines running parallel to the strings.

Before you started tuning, did you notice an unusual pattern to the out-of-tuneness? Especially near these flaws?

Did the piano hold tune well during tuning? Or, was it drifting inexplicably while you were working on it? Did the tuning seem stable after you finished tuning?

Edit: If the piano seems stable, these lines could just be artifacts from the casting process. Or, they could be the beginning of something not so good.

I assume the piano is still under warranty. You could mark these lines as well as photograph them. Then closely monitor them at each tuning for spreading, making sure to contact the manufacturer before the warranty period expires.

You could also try contacting the manufacturer directly to see if there have been any known problems with this particular piano.

I doubt the plate would tear in straight lines that appear to follow the line angle of the strings.

A couple of things to clear up. I have positioned the camera at a particular angle to show as many of the lines as possible in one shot. When looking at the piano straight on some of the lines are obstructed from view by the wire. So the camera makes it look like the lines are exactly between each unison which is not the case.

Secondly I have been tuning( or checking) this instrument every six months since 1996; that is why I am a bit surprised that I did not notice this previously. I tuned this one and then went to another room to tune another one of the same model, then came back to check something,I thought I missed on( hammer set condition) and noticed the lines then.

You know when you are tuning you look at the mutes and where they go and that is almost the exact point at which I insert them. This is why the concern, as I have never noticed this before.

No pattern of instability in the tuning noticed Joe, nothing like that at all. This has not affected the performance, stability or tuning pin torque or any other noticeable effect a twisting plate may or may not have. It is an interesting one to observe and I will continue monitor and see what develops.

I am going to take another camera with a larger lens and better macro setting to capture a couple of real close-up shots from about 4mm (1.6inches). Maybe early next week if I can get back there

Dan, it sounds like you have the situation well under control.

Another thing just occurred to me...
I wonder if the splitting is just the plate coatings and/or finish splitting. If so, this might still be a warranty issue.

Even though it may not directly interfere with the functioning of the piano as a musical instrument, this problem could affect its potential resale or trade-in value some day.

There's also the argument that this isn't supposed to happen to a plate, regardless of the actual cause.

I think the owner may likely have a legitimate warranty claim, if he cares to pursue it.

If a piano is 16 years old, does it still carry any warranty though?

Oops! My fault. Bad math. Yep, I'm embarrassed.

The chances of these being actual cracks in the casting are about 1 in zip. That is not how gray iron cracks. Ever. Given the structure of gray iron it is simply not possible; there is always going to be a slightly jagged line. Unless, of course, the frame is made of something other than gray iron and that is highly unlikely.

You may be seeing cracks in the finish or—more likely—scratch lines put there either during manufacture or—also more likely—sometime subsequently by someone who has been in there is a tool (or toy) of some sort.

ddf

(PS 4 mm = 0.1575". 4 cm (or 40 mm) = 1.575". I hate converting!)

hello. are not Yamaha frames made of another type if iron than grey iron ?

I understand the mix is different when the plate is made like aluminium parts.

we call that "aluminium iron" : even if that does not have much sence , as I dont believe aluminium and iron can mix , the process used gave the name to the material.

greetings

They are still made of gray iron. It has long been claimed that the iron used for vacuum casting. And it is quite possible that some foundries do use a slightly different mix for vacuum casting than is used for “green-sand” casting. But it’s not going to be much different. Other foundries use the same iron—it’s poured from the same kettle—for both processes. Even if the alloys vary in subtle ways they are both still classified as gray iron.

There is an alloy known a aluminum iron but it is a highly specialized material used for some pretty high-tech products and processes. I doubt it has ever shown up in cast piano frames.

Iron and aluminum powders are mixed together to make some powdered-metal products but these are usually quite small; nothing at all like the size and complexity of a piano frame.

After WW II wound down the U.S. aluminum producer, Reynolds, tried very hard to interest piano makers in casting frames out of aluminum. Several piano makers did make pianos using aluminum frames for a time but stability problems and tone problems ultimately brought this to an end and they all reverted to gray iron.

ddf

What I have read is that the metal is differnent in the end, and is sounding more strong , which is easy to verify on a Yamaha grand vs a Steinway for instance.

so more signature of the plate tone in the final mix.

I did no knew that aluminium and iron could be mixed.

Just had an article on plate design and making, but not all details in mind at the moment. But the material difference is enlighted by the factories that still use grey iron with the sand casting process.

Actually iron is not one of the 7 different alloying materials deliberately used for aluminum in its different series. The existence of brittle platelet β-Fe-rich phases lowers the mechanical properties of aluminum alloys. Iron is regarded as a contaminant of aluminum for this reason and removed/reduced by a process of intermediate phase filtration.

The pianos with aluminum plates used 5XXX or 6XXX series aluminum which uses magnesium as the primary alloy element (6XXX also includes silicon and is heat treatable). These are the same series of aluminum used in some train, truck, ship building and structural elements because they have the highest strength of the aluminum alloy groups. Purer aluminum would crumple up under the strain of a piano. I think the lowest iron content for available "aluminum iron" alloy is 20% but as Del mentioned its used in specialized application in military/space industries. I believe that aluminum iron alloy has some peculiarities in regards to eletrical resistance and thermal expansion, neither which is suitable for the pianos structural needs.

Yes, I have read that as well. Usually written by someone who doesn’t’ really know all that much about iron casting.

Yamaha grands and Steinway grands have a number of differences in both design and materials. How do you pick out exactly which differences in tone performance are attributable to variations in the metallurgy of the cast frames? As well, we should remember that the larger Yamaha frames—from roughly 200 cm and up—are all sand-cast, not vacuum cast.

The only way to really determine what tone variations can be directly attributed to one type of frame or another—i.e., sand-cast vs. vacuum cast—is to compare the identical model piano fitted with both types of frames. I’ve now been involved in two of these trials. After extensively listening to and testing several samples each of pianos fitted with each type of frame casting the conclusions were that any differences attributable to the casting methods were so subtle that they could neither be heard nor measured.

Admittedly this may not hold true for all manufacturers and all foundries but it was enough to convince me that most of what is being written about subject is both ill-informed and inaccurate and is usually done to promote one piano brand over another. In other words, it is marketing hyperbole.

I’m quite willing to be proven wrong on this but I’ll want the results of direct side-by-side testing done in such a way that it reduces any personal bias on the part of the listeners/testers to a minimum.

ddf

Del, I haven't done any sound comparisons between pianos using different casting processes but I would think its unnoticable myself. It is not a true vacume process anyways that is used and it is best described as vacume assisted. Some space age materials are cast in an actual vacume to eliminate oxidation and other degrading elements from the mix along with chemical reactions involving oxygen...the vacume assist method simply gets a more uniform/controlled flow in the mold with less turbulance and occlusions and produces better dimensional stability in the end result. The material is drawn from under the surface of the bath so there isn't as much slag either. Many companies in fact have turned to vacume assisted pours because it is easier to automate, cheaper in the end, and the form is brought to the furnace rather than the other way around and this helps greatly in controlling the temperature variations. With the process somewhat mysterious to most, I don't doubt for a moment that all types of hype and marketing angles can be spun off of it.

In the beginning the companies that did not use vacuum-cast frames claimed that the vacuum-casting process was inherently inferior. Inferior metals had to be used and the rapid cooling of the castings caused internal stresses that would lead to cracks and fractures.

As more an more of these same manufacturers began using vacuum-cast frames the whole story changed. Now it is the vacuum-cast frames that are superior. They use better metals and the finished castings are more stable, etc.

It is no wonder that most consumers and many technicians are confused.

What I can say with certainty is that when I walk through the YC/Weber foundry iron is poured from the same ladle into the vacuum-assisted (good phrase, that) mold and into green-sand mold. And they cool at about the same rate (consistent with the size of the frame being cast).

ddf

Well if the larger Yamaha grands are sand casted ther may be a reason , and it should be easy to bang on both plates and listen to their tone.

The article I have was written by someone who actually have piano plates cast. Then I am also in touch with the asdociation of iron art founders, that provided some answers to my basic questions.

I will get back with more food, but something with the plate tone is noticed in old pianos, where the plate is harder and tones higher..

A good special ear is certainly a necessity to judge about those things. As this is at large something cultural , I dont know if those kind of subtle difference is yet noticed by our Chinese makers particularely if it is on vertical pianos the difference may be minimal.

Then very certainly anyone can use a spectrum analyser if he knows what to look for. If I understand well factories as Petrof use computerized modeling to check the resonant frequencies of the plates , and then they use xhat is called " grey iron " to make them.

indeed I appreciate the precision I find when repairing a Yamaha grand. no strings height variations gor instance, but tonewise I will be easily sold on that idea that the more sonorous plate is acting in the tone.


excuse the typos please. the joy of mob phones...

The grey cast plates aldo can be designed to participate to tone. More or less. (hence probably more or less massive, more or less under tension and reacting more or less to the impact ) The article state that there are 2 schools in that regard, linked with the ability left to the case and brace to react to the tone and filter it.

Thanks for that clarification, it seems the vacume process is even less extensive then I thought. I presume it probably serves its primary purpose in getting the flow of the iron out to extremeties or smaller detailed areas in a better manner than a straight pour does. Maybe gives them a bit of design freedom also.

I had heard somewhere that all the N.A. pianos in the first half of the last century primarily had their plates cast in one place also, regardless of the brand name. They had their gimicks then too. Remember the dozen or so uprights that had the words "Genuine Bell Metal" cast into the plates?

Only thing I'm aware of is that some VF plates have had annoying sympathetic resonance problems. I would be inclined to attribute that more to engineering/design failure than something inherent to the process . . .

The vaccum process is said to be more precise so there is a gain in productivity, The structure of the iron is more homogenous.

Nevertheless, it is used for the less expensive models, as the quality of the iron in the end is less good.

A plastic film is employed to create the shape of the caul (I dont know if it is then mixed with the iron)

The sand process is providing more moisture in the mold to the iron, and the structure of the metal have thinner grains (micro crystalline structure)

but less homogenous.

Again what seem to be in cause is the better damping of tone with grey iron obtained with the traditional casting.

That said, some plates are designed to be in vibration and to transduce tone, they are heard in the final tone. they are installed on dowels and the belly have to be massive then.

More massive plates go along with lighter belly, then the case is more filtering the tone and the plate is supposed to be neutral (Boesendorfer for instance)


Just a quick resume of my reading..

I ran into something similar today. This is a grand I've serviced for years but never noticed this. It's just past the last tuning pins at the treble end.

First, let me say that I’m not a metallurgist. Nor am I a casting or foundry expert. What I’ve learned about iron casting has come from spending a lot of time in foundries over the past few decades, asking a lot of questions of the people actually doing the casting and studying much of the available literature on the subject.

It’s also come from designing a few frames (plates), having them cast and building the pianos. And then sometimes redesigning the frames, having new castings made and building more pianos. It can be a brutal school and what you learn doesn’t always conform to what all that nice piano marketing stuff would have us believe. Or all those nice theoretical books, for that.

That said, I will repeat what I wrote earlier, the quality of the iron is most often the same in both process! Vacuum-cast frames are used by the manufacturers of production pianos for all the reasons that have already been discussed. Primarily, they are more precise and they can be less expensive. It is inaccurate and misleading to say they are only used for “less expensive” models. Manufacturers such as Kawai and Yamaha use them in their smaller pianos—regardless of price—because they are good frames.

Have you ever actually been in a foundry using the vacuum process? It’s a fascinating process. The pattern is placed in a “sandbox” and covered with a thin, plastic film so the sand never actually comes in contact with the pattern. A vacuum is drawn pulling the plastic film very tightly against the pattern. Loose, dry sand is dumped over the patter and the whole thing is sealed. (The sand is damp in the green-sand casting process; that is the meaning of the phrase “green” sand.) A cover comes down over the sandbox and a vacuum is drawn over the whole thing. The vacuum pulling against the plastic film holds the sand in place. That is the purpose of the vacuum. When the sandbox is raised it all comes up as a unit.

The pattern is flipped over and repeated for the bottom of the pattern. Then the two are joined and iron is poured into the cavity. Since the temperature of the iron is upwards of 1,200° C (≈ 2,200° F) the plastic film vaporizes as the molten iron enters the mold. The poured frame is then left to cool in the normal manner. The cooling is not forced or accelerated in any way.

The advantages are that finer sand can be used which means that the finished casting is smoother and more detailed. And, of course, even though the initial cost of the vacuum process line is frightfully high the final cost of the frames can be lower because it is a fairly automated process and, since it is an assembly line process, that cost can be spread over many frames.

Within limits the structure of the iron can be whatever you want it to be depending on the physical characteristics of the finished product; in this case a piano frame. The grain may or may not be finer. In the case of Young Chang/Weber foundry the iron is the same for both vacuum-cast frames and sand-cast frames.




There is a lot of supposition in there. A lot! Just because a frame is mounted on dowels doesn’t mean that it was “designed” to be in vibration and “transduce” tone. That would be a very inefficient system and the cost would be seen in a rapid rate of decay and an overall short sustain time. I’ve also heard factory representatives go on about this but they tend to get rather confused when asked about the purpose of all those nosebolts.

ddf

So, stick a sharp tool in there and peel away the cracked finish and let us know what you find. Odds are you won't find a crack in the iron.

ddf

THanks Del, I can only refer to my sources and I am not trying to convince you. Anyway that seems to be the 2 "schools" of plate design in Europe.

I used the word transducing for lack of better term. T6he plate have an imprint in tone or that one try to be lessened to the most.

By evidency aplate is sonorous if its braces are free, the Jazz musicians utilise that tone by playing with mallets on the braces, and what is heard in the case of Yamahas certainly can mix with the bass tone in an audible way (to show a simple example) put a finger on a brace when the basses are played and you can notice how much it is moving

Then resonance can be lowered, or mastered/regulated, so to avoid them to be too large at some level.

If you have seen that the same mix was used for the vacuum process and the sand cast process that just mean that it was the same iron quality. There are visibly differnt mixes to make that grey iron.

WHat is happening I dont know, but the cooling is said to be faster with the sand casting ^process, due to the humidity and that also modify the structure of the iron produced, this seem to me logical that 2 differnt process provide 2 different results in metallurgy.

Did you notice a second "cooking" at 50/800°c (932-1472 °Fc ?)

Ther seem to be a process based on vibration , that can be used to relive the internal strains of the freshly done plate (this process seem to be necessary more with the sand casted plates than the vaccumed ones)

Yes it may be fascinating to see. I will let you know what I find on the iron quality when exchanging with the French founder association.

Finding Iron or high grade steel today is a challenge. The France have a large tradition for that (Germany buy us steel to produce the high grade cars)

As a friend said me recently : the Asian producers are at the same time saving and killing the piano trade.

A young tuner today have rarely any idea of what was the piano tone in the 70, not so far (and not the best perdiod)

Forget about pre War, etc... what we hear most often is a simplificated version of piano tone...


All the best

You're most likely right, Del. For one thing, this piano is really, really stable year to year.

cracks may happen around the bolts also, mostly where the iron is thin if I understand well. rarely it cause a problem with stability.

This sound more clearly like a crack in grey iron (even if not deep) than the ones of the Dan's picture (which looks like a vaccum molded plate) .