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Crankshafts developed wide applications even before methods to design them got evolved. Initially, they were assumed to be made up of beam segments. Since, the length to width ratios of the segments are of the order of one, these methods were not effective. Therefore, till recently they were designed based mostly on in-house experience and by using empirical formulae. Of late, with the advent of powerful computers, analysis based on finite element method has come into use for crankshaft design. In this work, we generate, from fundamentals, a systematic procedure to design crankshafts for finite life. Our method uses the advantages of both the classical method and the finite element technique. For the initial and the approximate results, we use the classical method. A software developed, TVAL, based on this method, quickly gives the natural frequencies, critical modes, displacements and stresses. For more accurate results, we model the crankshaft using solid finite elements.

A philosophy is proposed that there might exist a definite correlation between the engine parameter variations and the Fourier coefficients of different harmonics of the corresponding pressure diagrams and their derivatives. It is thus possible to establish the law of variation of Fourier coefficients with respect to a particular parameter. From these correlations, it is possible to predict a cycle, taking into consideration all the important parameters-injection timing, load, speed, flow processes, etc. Harmonic analyses developed in our laboratory are based on the principles of analog computation, to get results instantaneously, while the engine is running on the test bed.