1983 Volume 18 Issue 12 Pages 982-988
Various experimental equations (designated as experimental equations hereinafter) have hitherto been applied on torsional stiffness calculations of crank shaft in the form of equivalent length. However, all of these experimental equations had been obtained more than 50 years ago. Recent engines become substantially different from engines of those days in respect of weight, speed and so on, and characteristics of crank shaft are also conspicuously changed. Accordingly, experimental equations produce large errors and have little universality for diversification of crank shaft shapes. Therefore, the equivalent length is now obtained from actually operated engine data or estimations from an engine having similar characteristics, thus an experimental equation being used with its correction factors properly determined by an engineer in charge.
In this study, first, torsional stiffness of crank shaft was dynamically measured by the use of a vibrator, and good coincidence between the measured results and values calculated back from measured results of torsional vibration in an actual engine, was made clear. Then, torsional stiffnesses were measured with the shape of the crank shaft changed variously, and simultaneously torsional stiffnesses were obtained by the FEM, thus calculation accuracies of more than and inclusive 96% being obtained with respect to actually measured results for all shapes of crank shafts.