Topic: Steel vrs. Iron harp
Just a question regarding modelling. I have seen makers who are using welded steel plates in lieu of cast iron. If Modartt wanted to model such an instrument would this material difference have to be accounted for?
Bill
- billd
- Member
- Offline
- jcfelice88keys
- Member
- Offline
Re: Steel vrs. Iron harp
billd wrote:
Just a question regarding modelling. I have seen makers who are using welded steel plates in lieu of cast iron. If Modartt wanted to model such an instrument would this material difference have to be accounted for?
Bill
As a metallurgical engineer with two advanced degrees in metallurgical and materials (plastics) engineering, I can tell you that cast iron and steel both originate from the same base element, namely, iron.
Cast iron has nominally 0.02% carbon dissolved in the iron in its solid state, with much of the balance of its 4% carbon content taken up as forms of carbon/graphite. Steel has 0.02% carbon dissolved in the iron in its solid state (at room temperature), with the balance of the extra up to .80% carbon taking the form of iron carbide.
My point is this: Iron -- is iron, regardless whether it is a base metal in steel or cast iron. The modulus of elasticity (how much it stretches in response to how much stress is imposed) is about the same. The difference is that cast iron is comparatively brittle, and will fracture if stressed in tension -- however, cast iron is great for being compressed. Steel can be very ductile, depending on carbon content and its thermal history.
Short answer to your question: The difference in sound would be negligible.
Cheers,
Joe
- Beto-Music
- Member
- Offline
Re: Steel vrs. Iron harp
http://www.atcgroup.com.au/CustomCastin...rging.aspx
Who knows what piano manufactures would had made if was possible to forge very large pieces of steel...
Maybe the modeled world could try something.
The sound can be alsmot the same, for pieces of the same size and shape, like JCFelice said.
But in a modern piano the cast iron harp need to be large, heavy, to hold the great stress of all strings of the piano, constantly making tension.
Supose the metal was stronger, like forged iron. Maybe they could use pieces of different shapes or with less tickness, and as result the sound would be somehow different.
Last edited by Beto-Music (19-02-2016 19:23)
- jcfelice88keys
- Member
- Offline
Re: Steel vrs. Iron harp
Beto-Music wrote:
http://www.atcgroup.com.au/CustomCastin...rging.aspx
Who knows what piano manufactures would had made if was possible to forge very large pieces of steel...
Maybe the modeled world could try something.The sound can be alsmot the same, for pieces of the same size and shape, like JCFelice said.
But in a modern piano the cast iron harp need to be large, heavy, to hold the great stress of all strings of the piano, constantly making tension.Supose the metal was stronger, like forged iron. Maybe they could use pieces of different shapes or with less tickness, and as result the sound would be somehow different.
While it is true that the piano wires (strings) are in tension (over 200 individual strings each at tensions between 200 and 300 pounds per string), the frame is held in compression. It matters not whether the material in compression is cast iron or forged steel. Castings are used because less raw material is required to make a steel casting, than to forge the same (end) shape from a large bar or plate, and then dispose of flashings from the forging.
Cheers,
Joe
EDIT:
P.S. I know what you are driving at: a smaller "volume" of steel frame might allow more of the soundboard to be heard. Actually, think of the steel frame as a "substrate" on which you hang the tensioned steel strings. In the finest pianos, the iron-based frame plays progressively less a role in the overall sound -- that being responsible by the piano's scaling design, placement of hammer contact along the strings' lengths, choice of materials for the soundboard, hammer material, hammer weight, hammer hardness, choice of action, wooden casework, etc.
End EDIT
Last edited by jcfelice88keys (19-02-2016 19:37)
- sandalholme
- Member
- Offline
Re: Steel vrs. Iron harp
Can't comment on large pieces of metal, but I had a David Rubio copy of the 1769 Taskin, originally strung with brass strings in the bass, steel strings for the rest of the compass. Later, the steel strings were replaced by iron strings - as they would have been originally. The difference in sound may have been subtle, but it was there: less "steely" (sorry), in other words a more complex, softer (not in volume) sound. Richer, I suspect, in the fundamental and lower harmonics, but I'm no expert in acoustics - it could be just the opposite. But of course, we can imagine such things because of our expectation that the sound will be different.
Neither steel nor iron strings broke, ever, whilst the highest brass string broke occasionally when tuning, just the once during a public performance.
- jcfelice88keys
- Member
- Offline
Re: Steel vrs. Iron harp
I believe the original question had to do with materials for piano frames/harps.
Choice of material for strings are an entirely different matter, regarding the timbre of a piano with brass or steel strings. The tension of a steel string can be approximately ten times higher that that of a purely iron string, because the tensile strength of piano wire is almost ten times higher than cold drawn iron wire.
Cheers,
Joe