European CRAFT-Projekt (Co-operative Research Action for Technology)
The research project, which was supported by the European Union, was successfully completed late in the year 2000. It was undertaken by twelve organ-building companies from nine European countries in co-operation with the Technical College of East Freesia and the University of Edinburgh.
The wind system is a part of the pipe organ which crucially affects its sound. Significant variations in pressure or simply unsteadiness of the wind will inevitably lead to changes in the volume and pitch of the pipe work. In the course of the project the reasons for these fluctuations were to be investigated in order to solve such problems in the future.
The project aimed to develop innovative wind systems, either by improving the mechanical control mechanism or by developing an electronic control system, in order to ensure trouble-free operation of the organ. By means of a wind system specifically designed for demonstration purposes the project partners could verify the efficiency of the new control mechanisms. In addition, it was intended to develop a computer programme for designing traditional wind systems more reliably and quickly.
As the first step of the project, nine pipe organs in five countries were systematically investigated on site in order to find out the reasons for the pressure fluctuations in various wind systems. Owing to the difficulties in obtaining data from a machine as complex as a church organ, the mechanical and acoustic characteristics of the most important elements of the wind system (i.e. different types of bellows, roller valves, tone valves and blowers) were examined in the laboratories of the Fraunhofer IBP. The measurement data thus obtained formed the basis of all further steps/works of development.
Hitherto, no reliable data had been available concerning (for example) the wind consumption of large organs, or loss of pressure either in individual wind system elements nor in different organ pipes.
Based on the measurement data, design software has been developed which enables the organ-builders to calculate the maximum wind consumption of an organ as well as the dimensions of the bellows, the roller valve and the wind trunks. At the heart of the software is a physical model, which describes the fluid mechanical processes in the wind system and the interaction of the individual components (e.g. bellows and roller valve). In addition, the desired strength of the pressure fluctuations and decay time can be directly adjusted using the software, and the dimensions of the bellows and the roller valve calculated accordingly. A maximum value is given for the flow velocity in the wind trunks, which prevents excessive pressure drops and wind noise. The software should make it possible to avoid potential difficulties in new wind systems at the design stage. It should also make it easier to diagnose and minimize unwanted fluctuations of the wind pressure in existing organs.
In the course of the project three innovative pressure-regulating systems were invented:
Two novel mechanical regulators with outlet valves were developed. The valves are fastened either to the bellows or the wind chest; their task is to produce a continuous outflow which counteracts the pressure oscillations, and at the same time keeps the operating pressure of the organ as stable as possible. The third system was an electronically controlled outlet valve. It offers the same functions as the mechanical system but can be computer controlled so that the behaviour of the wind pressure behaviour is entirely dictated by the organ builder. These three systems were demonstrated in the laboratory at the Fraunhofer IBP and the theory has been shown to be valid. For their reliable use in practice, however, additional research will be necessary.
The project participants have already been applying some of the research results in their practical work. With the help of the software, certain shortcomings in traditional wind systems have been identified and eliminated. The novel pressure regulation systems and the innovative computer programme offer usefully ways of reducing the production costs of new organs. At the suggestion of some of the project partners, the very promising results will be developed further in a follow-up project and will be made available for general practical use.
This research initiative was supported by the European Community in the context of a CRAFT (Cooperative Research Action for Technology) project. The following companies participated in the project.