Lateral Stiffness and Vibration in Engine Structures

Abstract

Abstract The forces tending to produce horizontal vibration in engine frames may be obtained from the bearing-load diagrams. For an eight-cylinder nine-bearing engine, the dominant forces occur at the center main bearing and bearings Nos. 3 and 7. The first major horizontal critical speed is the eighth order, which will come into resonance when the engine speed is one eighth the natural horizontal frequency of frame. In view of the difficulty of predicting the horizontal frequency of the complicated frame structure, a simplified empirical method of comparing stiffness of frames is given.