Multibody Dynamics as a Historical Tool: Study of an 18th Century Piano Action of Andreas Stein
Baudouin Bokiau, Paul Fisette, Anne-Emmanuelle Ceulemans · Digital Access to Libraries · 2014
Ancient instruments can tell us much about the way composers of the past centuries wrote the music they played. Indeed, playing characteristics of historical instruments are often very different from those of the instruments we are used to. For example, in the case of the Viennese piano actions used by Mozart and his contemporaries, the so-called "escapement height" largely conditions the response of the instrument to the pianist's touch. The escapement-height is the distance between the hammer and the strings at a given moment of the key stroke. In this contribution, it is aimed to define how the Viennese action behaves when the escapement height or other parameters usually adjusted by piano technicians are changed. To do this, a multibody model containing the frame, the key, the hammer, the pawl and the string has been developed. This paper describes how the model has been created; a special focus is put on the detection of contact between bodies, which looks easy in the real action, but is in fact complex to model. The model is compared with high-speed imaging data and a parametric study of the escapement height is performed by adjusting the rest location of the pawl. The high sensitivity of this regulation is revealed as a shift of 1mm of the pawl seems to induce a displacement of the escapement height of 20mm. It is also shown that a strong but linear decrease of the maximal force between the hammer and the string appears when the escapement height increases. Further results concerning other regulations like the spring tension of the pawl and the friction between the hammer and the pawl will be discussed during the presentation.