Piano World Home Page Forums Our Most Popular Forums Piano Forum Steinway "steel" frames?

I understand that Steinway used a different kind of metal in their frames during the early 20th Century. This 1901 Steinway NY catalogue (http://antiquepianoshop.com/online-museum/steinway-sons/) makes repeated reference to "steel" frames. Here is a quote from p. 10:

"The resisting power of these instruments rests in a patented Double Cupola Steel Frame with Capo-d'Astro bar (cast in Steinway & Sons' Foundry, possessing double the resisting power of ordinary cast iron)."

Yet a previous thread seems to conclude that the frames were not properly steel but rather a different kind of iron. Can anyone explain further what metal was used and how it differs from the kind of iron used that is used in pianos today (gray iron, I believe)? Is there any difference in sound between the old frame material and the new?

Interestingly, Wiki says that one of the characteristics of gray iron is its excellent ability to damp energy: "The graphite also gives gray iron an excellent damping capacity because it absorbs the energy..." To add to it, "its impact and shock resistance is almost non-existent." I am just an end-user, but is that really the best available material for a piano frame?

The subject of metallurgy is a deep subject with lots of science and physics involved. Typically, iron is a part of most types of steel, depending on the density, tensile strength and hardness. High carbon steel is usually the hardest, and all the different alloys can make a difference in strength and cost.

This is somewhat OT, but another one of my hobbies is restoring old farm tractors and pick-up trucks. I read that Henry Ford had the absolute best steel foundries in the world in the early 20th century. The steel and cast iron parts on the old Ford cars trucks and farm tractors were tougher and harder than anything I’ve ever seen.

No wonder there are so many of the old Ford farm tractors still around, and still working in the field.

Rick

True, cast iron breaks up about like clay flowerpots. But impact and shock aren't part of the service life of most pianos, so it doesn't matter -- unless the movers drop one.

the plate is not on its own, to contains the tension of the wire, the complete assembly is the plate and the bracing under the piano (and the case eventually)

Iron accepts to warp a little, and it is the case on the thinner plates, that are "coloring" the tone somewhat.

But even very massive plates as Boesendorfer, are often warped at the tail a few cm not rare.

Thanks very much to everyone who has replied so far; these are good points, particularly how the metal frame is just part of a larger system, and the fact is that relatively few frames actually do crack (apologies to Glen Gould's old model D that proved to be an exception). And no doubt the fact that gray iron just does not compress makes up for a multitude of other faults.

Even still, one would think that *damping* 10x more efficiently than any other form of iron and 20x more efficiently than steel would be less than ideal for a structure you attach piano strings to. I realize that the speaking lengths are terminated prior to the point the string actually reaches the frame, but surely it would have some effect on sustain?

Anyhow, does anyone have more definitive word on why Steinway at some point claimed they were using "steel" frames? Were they? Or is this a terminological issue or even a marketing gimmick? And mainly, whatever it was, was the change to what they now use (gray iron) actually a change for the better or for the worse in terms of function?

The precise technical definition of "steel" used at the end of the 19th century is different than what technical writers would use today. Metallurgy has progressed much since the 19th century.

I have found that understanding the damping characteristics of the elements of piano construction is very useful. Hammers are a type of damper. The way the string terminations are configured can greatly effect the damping of longitudinal energy in the strings. The frame that damps some frequencies well will produce a piano with a warmer tone. One that can be played vigorously and not become ugly.

Remember, the piano is a percussion instrument, with the musical intent to evoke the widest range of dynamics and color. So by pounding on things to impart energy into the desired transverse modes, it is important to control the sound of the pounding.

Thanks, Ed, that is very helpful. I was beginning to suspect this was the case; re-reading a previous thread Del states that it was actually "wrought iron" in current terminology. The questions remain, why did Steinway change material from wrought iron to gray iron, and can one hear the difference? What year did they change, incidentally?

I see that Petrof has built a piano with a full-on steel frame:
https://www.youtube.com/watch?v=94a4mz6goic
What do you think of the sustain? Now, as to what steel does to the tone in other ways, that is another question. I wonder if you would say that the failure of the steel frame to damp at various frequencies results in a less musical tone.

What makes you think this Petrof has a "steel" frame? On the Petrof website under technical specifications, it specifically says: Cast iron plate, wet sand casting. In fact, it says the same thing on all their grand pianos.

http://www.petrof.com/klavir-p-237-monsoon.html

Not quite all, ando. If you click on "unique models", you will see "P 237 Monsoon Steel Piano" with the following write up: "Grand Piano P 237 Monsoon with steel frame was built based on the research and development activities of The PETROF Company in cooperation with Universities, science institutions and special metal workshop. The core idea was the replacement of the cast iron frame (the plate). An idea to produce a steel frame from solid steel, cutting, drilling, milling and laser or plasma cutting came about during the discussion of possible solution. This type of production is the first of its kind in the world."

Under the technical specifications, there is this: "The steel frame is heavier than a cast iron frame; however, its design allows for a much larger open area of the soundboard. The steel frame is far more stable than its cast iron predecessor. Frame stability has a great influence on the quality and stability of tuning and regulation of the piano action. This grand piano has a very good sound, and very high stability in the action and its tuning of stability."
http://www.petrof.com/klavir-p-237-monsoon-s-ocelovym-ramem.html

However, I think you are right about the P 237 in the video; the link that led me there misled me into thinking it was the steel frame rather than the conventional frame version.

Erchoukyrie,
Thanks for the video of the Smetana on a Petrof. The pianist is excellent.

I don't care for the Petrof sound that much though. Thin and crashy bright. Treble doesn't project that well but who can really tell from a recording anyway. Nowadays all recordings create a digital piano of a sort.

I have been told that Baldwin used welded mild steel to make a piano frame just after WW2. Several boutique builders have used them including David Rubinstein and Chris Chernobieff.

One potential problem with mild steel frames is that mild steel is easily bent. Cast iron will flex and then fail by cracking. It can't be plastically deformed, it will flex and then break. Mild steel can be flexed, bent and then finally break with a great amount of difficulty.

Most string frame designs result in the load paths from the string tension placing the struts under some amount of elliptical loading. The struts are trying to bow up. My concern with mild steel is that over time these struts get permanently bent thus deforming the instrument.

Some cast piano frames are cast with processes that result in the metal being harder than others. In my experience the harder frames make for a less desirable tone. Some makers will heat treat the V-bar portion of the capo bar. This leads to a shrill, false beating treble that will break strings easily.

Steinway NY has done this from time to time. I have seen heat treated V-bars on Steinways starting in the early 1960's and continuing to at least as recent as 2005 or so. The heat treated ones always have a bad treble.

That was and education, Ed, thanks very much. The history of piano technology seems to be littered with unintended consequences--fix one problem, create another.

I think I found the answer to one of my remaining questions: it seems that wrought iron is no longer produced because it costs double what mild steel costs. Mild steel is unsuitable for the reasons you mentioned (not to mention the tendency to rust). So gray iron it is...

You'd have to bend them beyond their elastic limit to get a permanent change, which isn't easy to do. Most woods and plastics will take a permanent set that way, but metals don't.

Greetings,

You have to consider the mechanism of creep deformation, which can occur below the elastic limit. I don't know that is happening in the case under discussion (stress levels, temperature, specific metal), but generally speaking, it happens in metals.

Best wishes-

Thanks for that, Erchoukyrie, I didn't see the "unique models" section. A few years ago I saw these Petrofs in the the flesh so I knew their normal pianos were standard cast iron frames. The problem is that Petrof has such limited distribution these days, there is virtually no chance that you could hear a steel-framed version next to a cast-iron framed version next to each other to compare who they sound. It sounds like a large investment in something they can't actually sell to anyone.

I think instead of talking about "steel frames" of one sort or another, it is perhaps more fruitful to understand how cast iron frames are made in today's industry.

The basic difference is quite obviously V-Pro versus grey-sand-casting.
Anybody interested in this subject can do a search of their own.

Fact is that most or all high end pianos seem to prefer grey-sand-castings.
Steinway does and so do a good number of others including Estonia.

Few if any would ever talk just about "steel"...
[outside tank makers perhaps..]

Norbert

The one place steel does get used is in one-off special pianos. The experimental extremely long pianos are typically steel, things like, IIRC 17 ft or 25 ft.

Just prior to the Baldwin-United bankruptcy in 1983 the company was making plans to convert some part of their vertical piano production to welded steel string frames. The fabrication plant was to be built alongside the existing Trumann, Arkansas plant. Flat steel would come in by rail, be offloaded, cut using (then) state-of-the-art NC cutting technologies, welded and finished and sent via conveyor directly to the vertical production line.

From what I was told the company had already built several hundred prototype pianos using steel string frames and the feedback from technicians and end-users alike was positive.

During my time with the company all prototype pianos were built using welded steel string frames. It is a lot less costly to have the maintenance shop chop out steel panels and struts and weld a frame together for a one-off prototype than it is to fabricate a casting patter that may have to be significantly changed for production.

The performance of a piano using a steel frame is some different than its otherwise identical counterpart using a gray iron casting. (I highlight the word “identical” because a production instrument is never identical to its prototype.)

As has been mentioned by others, the damping rate is considerably different. It is commonly noted that gray iron has an “excellent” damping factor. But the word “excellent” is a conditional one; if vibration damping is a desired trait then gray iron is, indeed, a good choice of metals. If, however, you’d like to keep energy in something like a vibrating string then the desirability of a high damping rate becomes somewhat more nuanced. Without exception the pianos I have worked with using steel string frames have exhibited slower decay rates (i.e., longer sustain) than their subsequent production counterparts using cast gray iron string frames.

Strength is not an issue. When I last checked O.S. Kelly was casting 30K iron. That is a square cast beam 1” x 1” (or 25.4 x 25.4 mm) to the side will break under a tensile load of 30,000 lbs/in2. It will have a somewhat higher compression strength. But neither its tensile strength nor its compression strength will be anywhere close to that of what we commonly call “mild” steel. Every piano I’ve worked with having a steel string frame has had excellent tuning stability. I can’t speak to how they would have performed over the long term since prototypes are generally destroyed after they have served their purpose. From a strength standpoint string frames are so over designed—check the bending characteristics of a 1.5” x 0.5” steel bar—I can’t see this ever becoming a problem.

It is often claimed that a piano using a steel string frame will have problems with spurious “ringing.” I.e., struts or panels audibly vibrating. I’ve never found this to be a problem. Panels generally have strategically placed nosebolts and I’ve never found the struts to be a problem. If such problems were to show up they are easily damped.

I doubt we’ll ever see welded steel frames used in production grands. The string elevations make their construction a little tricky. Vertical string frames, however, are ideal for such construction; flat, single-plane construction with simple strut configurations. Using today’s technologies everything could be cut using CNC controlled plasma or waterjet cutters. The individual components could be designed to go together like an interlocking puzzle. Robotic welders would make short work of welding the things together. The result would be absolute precision which would ease subsequent assembly processes. I don’t know if it has been done since the Baldwin-United days but I’d like to see a serious cost analysis comparing the two technologies.

ddf

I wonder whether the piano in this topic may have been made with a fabricated steel frame. It seems to be an experimental piano, one of a kind.

Is not there a builder in USA that makes pianos with welded steel frames ?

I did see a few videos, but the name escapes me.

The tone seemed to be particular , that I did think it was due to the steel, but this may be psychological.

The plate is coloring the tone, most probably mostly during the hammer impact . I bet that the V cast molded plates are responsible for that lighter and warm tone of some asian pianos.

Probably. Howard Graves came up with some rather different ideas. His patent files are always interesting.

ddf