Analysis of piston-crank system balancing in V-VR engines

The advances made in materials science and modern material production and processing technologies support the design and serial production of structural solutions which could not have been applied in the past on account of their complexity or high cost. The piston-crank system of a combustion engine remained practically unchanged over decades, and the only structural modifications involved the use of new materials for improved fatigue strength or attempts to limit the mass of system components to minimize inertial forces. Since the invention of the piston engine, in-line engines have been the predominant type of engine configuration on the market. Larger engines are built sporadically, and most of them have a "V" arrangement of cylinders and pistons for easier mounting. Selected vehicles, in particular sports cars, are equipped with boxer-type piston-crank systems. Recent years have witnessed the advance of new engine configurations with VR or V-VR piston-crank systems which are often referred to as W engines due to a unique arrangement of the connecting rod. The V-VR crankshaft-piston configuration supports the design of engines characterized by high displacement and reduced size for easier assembly in the vehicle's engine compartment. Such solutions are often deployed in upper class cars. There is a general scarcity of information about V-VR piston-crank systems in literature, therefore, this study presents an overview of the above configuration and analyzes inertial forces impacting the discussed system.