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For a constructor of musical instruments the raw material is very important. Thanks to the collaboration between physicists, metallurgists, engineers and the PANArt tuners, a new perspective can be presented. Cultural and musical concerns.
IN the middle of the 1970's the steelpan came to Switzerland to the town of Zürich and to the capital Berne. Tourists and business people brought the pan from London to Zürich, where they had been infected by the 'pan virus' at the Nottinghill carnival. They introduced the pan to the carnival of Zürich. In Berne on the other hand, young people, fascinated by a concert of a Trinidad Steelband began immediately to construct their own pans. Nowadays there are about 150 steelbands in Switzerland and steelband training is offered in about 50 schools. Many other people play the pan in conventional orchestras as soloists. The pan is also played in music therapy.
The huge demand for steelpans at the end of the 80's, and at the beginning of the 90's, forced the panmakers of Berne to deal [specifically] with the [problem of] raw material. The reason was the bad durability of the steelpan [in holding its tuning] and the need [to find] tuners who were able to repair the instruments at low costs. This paper explains the path which has led to the [development of] Pang; [steeldrum] instruments made of a new sheet metal, with good durability and a new sound.
For a constructor of musical instruments, the quality of the raw materials is the most important challenge. All panmakers know about the difficulties in judging the qualities of sheet-metal steel; and all of them realise also, that in the last decades, the steel used by them has become worse over the years, with regard to the construction of steelpan instruments. They are also aware that the construction of a musical instrument with a soul needs patience, intuition and an extensive knowledge.
2. What is Hardness?
European drum producers get their sheet-metal from all over the world. The sheet they use for the drum production is not defined. That means its composition and its structure is not exactly known. This sheet-metal is of the lowest quality. These attributes make it difficult for a panmaker, because he has to adapt to the changing conditions. In the last decades, due to better control of the production of sheet steel, the content of carbon has decreased from 0.15% to 0.06%. The result of the low carbon content is a low strength-hardening factor. The tuner had to sink the drum deeper and deeper to attain the required hardness.
For a Swiss panmaker it was difficult to get hold of old drums from England or the USA with that higher content of carbon. Many ways were tried to strengthen the material.
At the beginning we burned oil in the pans, hoping that carbon would penetrate into the surface. It did not work, so we tried the method of burning carbon, in the form of graphite, into the metal. Further, we thought that sand blasting could compress the surface; and from the farmers we copied their methods; of hammering the scythes on an anvil.
Sand blasting weakened the surface; and hammering on an anvil brought us too many technical problems.
The slow and conventional method of sinking, with many blows of the iron hammer, still brought about the best results. The technology of metal spraying failed: The chrome, nickel and bronze layers extremely damped the vibrations. All these techniques did not lead us far because the base was still the undefined steel.
In all these experiments, the hardness was of interest, but step by step we realised that hardness [alone] does not define enough the properties of the metal.
3. Yield Point and Tensile Strength
The initial help in this situation came from the engineers. We learnt to understand about yield points and tensile strength. We got from the University special German sheet-steel and we brought it into the drum factory.
Three types of sheet, developed for the automotive industry; with different yield points, tensile strengths and grain structures should be mentioned. They have led to good results for the construction of certain voices of the steelpan family. The automotive industry is faced with a similar problem. For forming they need a steel which allows a lot of elongation, but in the end, it has also to be buckling resistant and rigid.
Other sheet metal like copper, brass and stainless steel have not brought good results; because either they have a low E-modulus, or not enough potential elongation.
ZSTE sheet is microalloyed. It is a high strength steel with fine grains and a good deformability. The steel has a high damping factor. We used it mainly for the lower [voiced] instruments.
Bake Hardened steel is also a microalloyed steel. A heat treatment of 170° C for 20 minutes after deforming increases the buckling stiffness by about 10 %. This has a good effect on large shells - as we have in the steelpan basses.
Dual-phase sheet has a special structure. 20% martensite results in a high tensile strength. At the same time the metal has a good deformability. Thanks to the very good strength hardening, this sheet can be used for the higher voices of the steelpan family.
One other attempt should be mentioned. Swiss bell makers work with a sheet metal having a high amount of carbon (0.25%). We welded this material onto a skirt. The sheet was  [placed/annealed] in an oven for 9 hours. In spite of this treatment, we could not sink the head more than 10 cm. The sound of the notes was very good, but there was too much recoupling with other notes. When we tried to bend that sheet  at the skirt by machine, it broke.
Chemical spectrum analysis of drum-sheets of different origins showed us clearly that there was no hope to get sheet with sufficient carbon in order to shock or work harden. To get sheet metal with the convenient composition one would have to [place a minimum] order of ten tons - absolutely not possible for a small factory.
A chance comment by a blacksmith gave us a hint to yet another hardening process, about which we were previously unaware. He told a story of ancient Spanish and Saracene smiths, who shocked their war-arms in horse urine to harden them. We visited factories specialised in hardening. There we tested several nitriding processes such as carbon-nitriding, tenifer and gas-nitriding. The carbon-nitriding didn't work because the temperature of the process was too high (1000°C) and deformed the pan body. The Tenifer, a hardening process in a salt-bath, led to the generation of Blackpans. The whole resonance body stays for 30 to 90 minutes in the bath, where carbon and nitrogen diffuses into the surface. Coming out of the bath, the pans are black. The durability was very good, the sound was new, but the costs were too high. The gas-nitriding in an oven at a temperature of 580°C was the best solution. The parameters can be well defined, and the costs are low. This technology led to the Peoples Pan.
This [new] generation [of pan instruments] found a large interest in steelbands, and so too in the schools. Thanks to the deepdrawn steel we used for these pans; the sinking, shaping and the grooving could be done faster and with less power.
The pre-cut drums are taken to the hardening factory. Afterwards the pans are tuned and polished. We used drums with different diameters (640, 600, 572, 560 mm) to get a collapsible system for better transport. The gas-nitrided instruments are stable and the new type sound is accepted by the steelbands.
The problem of the instability partly solved, the technology of machine formed hemispheres now became a central part of our research.
The stretch-forming of the head of the drum was done in the beginning with heavy iron hammers. The knowledge of the mechanism of strain-hardening could be learnt from any metalworker. We observed that each sheet has its own hardening exponent. Some steel became quickly work hardened, other steel stayed soft. The strain-hardening with thousands of hammer blows to get more compressive stress in the surface could not be [a practical solution] for an European panmaker; living on a continent where the working costs are very high. The idea to let the sinking be done by machine was not new. We had heard of such projects to press the pan from Trinidad and England.
We started the project with spinning 60 drum-heads. The irregular structure and strain-hardening was not favourable for shaping the shells. The sheet broke and the tuners were frustrated.
The next step was to project the steel over a wooden form. We used a common deep-drawn steel and we fixed a skirt to the hemisphere. With this technology we did not have the problems of irregular strain-hardening, but [instead], problems with the changes of thickness. In the centre the metal was thicker; and decreased to the outer part. In this series we also tested a copper sheet of 1.2mm thickness. The cold-hardening was not sufficent, and the ratios for harmonic tuning could not be achieved. We realised that resistance force, the E-modulus, is also a very important quality factor.
6. Hydro-forming and Deep-drawing
Hydro-forming is a young technology and could be used to form the whole structure of a steelpan. The main problem is the cost. The tool is so expensive [requiring] that thousands of pans have to be made [in order] to get acceptable prices for the market.
There was one technology left, and for a small enterprise realistic, that of deep-drawing. This technology is very old. PANArt decided to invest in a tool in the form of a hemisphere. The sheet is drawn over the tool, then gas-nitrided, and then fixed to a skirt of stainless steel. For a complex form like this hemisphere, the metal-former needs creativity and feeling. The man behind the machine is an important partner on the way to a new instrument. The metal former and the panmaker have to understand each other because one can loose a lot of money with wrong decisions. The complexity of the pan [tests] the tuners [abilities to his limits]. [For better success], he needs an intense dialogue with physicists, metallurgists and engineers.
The new rawform serves to make some of our Pang instruments. It is comparable with a canvas a painter uses. The panmaker can create his own sounds. Many shapes are hidden in the material, which can be transformed by tempering, thinning and stretching. The deep-drawing technology leads to an uniform thickness, which requires a new tuning process; and leads to the question of the complex geometry of harmonically tuned shells.
7. Shapes and Sound
The new material, formed into a hemisphere by the metal-former and his machine, has brought a new sound. To hammer the note-shells out of the hemisphere, created a navel in the centre [of the note]; this navel is under heavy compression. Being used to tune flat notes, we wanted to eliminate it, but we realised that the navel had a surprising buckling resistance. Never before had we such a strong architecture!
After tempering [the hemispherical form] for 4 minutes at 400°C, the shells were annealed; and produced a long-sounding note. We confirmed, with sinuous excitation, that the navel spread the partials. The new material demanded new edge conditions [the boundaries of the note]; and [we discovered that traditional] grooving was no [longer] necessary.
For five years the PANArt tuners have worked on the same material and the shape has been refined. Tuners from the USA, Canada, Germany, France, Switzerland and Trinidad have tested the rawform, and some have built nice pans. Even the unique sound of a steelpan can be found in the material! The tuner has now more possibilities in approaching the different needs of the musicians.
For the musicians in Switzerland, France and Germany, PANArt could achieve the sound they needed. For over 10 years, women have asked for a warmer sound and more harmonic correctness. 70% of the Swiss pannists are women. They use our instruments to play together with classical European instruments or in steelpan orchestras. The schools initially refused to accept the too brilliant sound [and unreliable stability of the original steeldrum instruments], and asked for more stable instruments which would be more compatible with their other instruments. Measurements have shown that Pang instruments played mezzoforte, reach a level of about 80db; played fortissimo, to about 110db. Some Swiss pannists have ear trouble, mainly tinitus. The loudness is one of the most discussed problems in steelbands and we have to take that seriously. There was also an interest [from organisations concerned with social and medical] therapy: They ask for balanced instruments with different sounds.
The new technology brought a new geometry, the dome geometry.
The edge conditions in the modern steelpan, simply supported in a complex way, appear in the Pang almost on a plane. This fact allows [us] to take the clamped shell out of the belly and to put it into another resonancebody.
We were able to create new instruments and we are proud to present to you these Pang instruments.
When the steelpan came to Switzerland, twenty-five years ago, many people were attracted by its sound. With enthusiasm they began to play and founded steelbands. The European tuners and panmakers were confronted with an enormous demand for steelpans. The tuners realised the need of metallurgical and acoustical research; and founded with tuners, panmakers and steelbands, the joint stock company PANArt. A dialogue between scientists, musicians and tuners became possible.
The results of this interaction has been [the development of] new instruments, which shows [strong] influences of the European culture. The demands for harmonic, warm and stable sounds, comes above all, from the female players and through the schools. This demand led to the research of new materials to reinforce the fundamental.
A Swiss banker, who was involved in development of the Trinidadian bank system, [received in] 1970 a pan as a gift. This steelpan was from the Invaders panyard, and we realised that this pan had a strong fundamental and a warm sound. The fact that the Invaders pan [is] based on a strong material, showed us clearly where to begin with the research.
The authors thank Dr. Eng. K. Wogram and Dr. Eng. I. Bork, PTB Braunschweig D; Prof. I. Reissner and Dr. S. Messmer, ETH Zürich CH; Dr. Eng. J. Bossy, EMPA Thun CH; Dr. B. Engl, Hoesch Steel Dortmund D; Prof. U. Hansen, Indiana State University USA; Prof. T. Rossing, Northern Illinois University USA; Dr. R.Van Lighten and Dr. H. Bloemhof, Rieter Automotive Management Winterthur CH; E. Bartenbach, Cowbell maker Oberbalm CH.
1. T. Rossing and N. Fletcher, The Physics of Musical Instruments, Springer-Verlag, New York 1991
2. D. Hall, Musikalische Akustik, Schott Musik International, Mainz D 1997
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