Dynamic Balancing of 60-Deg V6 Engines With Shared Crankpins Using Asymmetric Alternating Counterweights

Abstract V6 engine architectures inherently suffer from geometric asymmetry and dynamic imbalance, particularly in 60-deg configurations with shared crankpins. Conventional solutions rely on split-pin crankshafts or auxiliary balance shafts, which increase mass, cost, and mechanical complexity. This paper investigates an alternative balancing strategy based on a flat-plane 0–180–0 crankshaft configuration combined with intentionally unequal reciprocating masses. An analytical formulation of the inertial force balance is developed to demonstrate how a tailored asymmetric mass distribution enables cancelation of first-order reciprocating forces and rocking moments, while significantly reducing second-order inertial effects. The analytical results are complemented by numerical investigations. Finite element analysis (FEA) is performed on a representative three-cylinder crankshaft model to evaluate stress distribution under low- and high-speed operating conditions, with von Mises stresses and fatigue safety margins assessed. In addition, a torsional vibration analysis based on an equivalent lumped-parameter model is conducted to evaluate the crankshaft dynamic response under harmonic excitation across the engine speed range. The combined results provide quantitative insight into the mechanical, dynamic, and noise, vibration, and harshness (NVH) behavior of a shared-crankpin 60-deg V6 engine employing unequal reciprocating masses. The proposed configuration achieves acceptable structural integrity and torsional vibration levels while preserving mechanical simplicity. However, due to the inherent uneven firing sequence of the 0–180–0 configuration, some NVH limitations persist, particularly in terms of torque pulsations and low-speed roughness.