Flywheels are heavy rotating discs connected to the engine’s crankshaft, storing rotational energy to smooth power delivery and overcome combustion irregularities. Primarily used in internal combustion and some electric vehicle powertrains, they maintain engine speed between power strokes. Key features include a precision-machined surface for clutch engagement, ring gear for starter motor interaction, and balanced weighting to minimize vibration. Materials commonly include cast iron or steel, with dual-mass flywheels incorporating friction damping elements for NVH reduction. Some applications utilize flexplate designs in automatic transmissions, integrating torque converter attachment.