Predictive-Cum-Experimental Analysis of Torsional / Bending and Crankcase Vibrations and Design of Optimum Tuned Damper

Design of crankshaft of multi-cylinder engine is becoming a vital area due to increasing concern for noise and vibrations from a power train. The complex nature of periodic excitation torque and dynamic properties of an elastic multi-mass system subjected to these excitations becomes one of the major sources of induced vibrations. These vibrations are broadly categorized into torsional bending and structural vibrations.

This paper describes the predictive analysis of torsional vibrations along with experimental validation for 3 and 6 cylinder engines. The effect of dynamic magnification with and without damping is studied. A tuned rubber damper is designed to limit the excessive amplitudes that occur during resonance.

Analytical work is carried out to find out the natural frequencies and modes shapes for the study of bending vibrations of a 4 cylinder engine crankshaft.

Finally the effect of crankshaft torsional vibrations with and without damper on crankcase structural vibrations is experimentally studied. This is done by simultaneously acquiring rotary oscillations of crankshaft and horizontal acceleration levels of a crankcase. The FFT is carried out on both the data. The results are presented in the form of Cambell and Z-mod diagrams.