Abstract

Conventional engine balancing process truncates the piston acceleration to form harmonics form for the shaking force; then using dynamically equivalent two-particle mass system for the connecting rod, the shaking force is balanced by arranging the phase angles of the crank throws. During this process, the shaking torque balancing (about the crank shaft axis) is ignored. Shaking force due to truncated portion of piston acceleration is left unbalanced; and that some phase angle arrangements cannot balance the harmonics of the shaking force. This requires force harmonic balancers. Unbalanced inertial forces generate shaking moment about the transverse axis (normal to crankshaft axis) that remains unbalanced. Shaking moment due to force harmonics for some phase angles also remain unbalanced. They require moment harmonic balancers.

This article presents a complete balancing method by which shaking force in each slider-crank loop is completely balanced. This also means that shaking moment is also completely balanced, thus eliminating the need for both force-, and moment-harmonic balancers. Article uses linearly independent mass vector method to retain the total center of mass of each slider-crank loop stationary. Shaking torque (sum of the inertial torques about the axis parallel to the crankshaft axis) causes variation in the output torque generated. This variation may be considered when designing the flywheel. However, the shaking torque is also balanced (or minimized) retaining the total angular momentum of each loop constant by arranging the phase angles of the crank throws. Several multi-cylinder engines are completely balanced for shaking force, shaking moment and shaking torque in the application examples, including balanced designs of connecting rod and throw sides.

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