Crank–Rocker Four-Bar Mechanism | Rotational Motion to Oscillating Motion & Coupler Curve

This educational animation demonstrates the operation of a four-bar crank–rocker mechanism and shows how continuous rotational motion can be transformed into controlled oscillating motion. The crank, shown in red, rotates continuously through a full circle. This motion is transmitted through the coupler link, shown in black, to the rocker, shown in green. Unlike the crank, the rocker oscillates back and forth through a limited angular range. The blue circle represents the circular path of the crank. The black points represent the fixed and moving joints of the mechanism. The animation also traces two important motion paths. The blue dashed line shows the trajectory of the end of the rocker, illustrating its oscillating motion. The purple dashed line shows the trajectory of the midpoint of the coupler link. As the mechanism moves, the coupler midpoint generates a characteristic closed path known as a coupler curve. Coupler curves are an important concept in mechanism design and kinematic analysis because they can produce useful and complex motion paths. Four-bar mechanisms are widely used in mechanical engineering and can be found in many machines and systems, including linkages for machinery, printing equipment, and other motion-control applications. This simulation provides a visual introduction to four-bar linkage kinematics, showing how a simple mechanical arrangement can transform continuous rotation into oscillating motion while simultaneously generating a complex coupler curve. Key Concepts Four-bar linkage Crank–rocker mechanism Rotational motion Oscillating motion Coupler link Coupler curve Joint and link motion Kinematic analysis Mechanism simulation Mechanical engineering Hashtags #FourBarLinkage #CrankRocker #MechanicalEngineering #Mechanism #Kinematics #EngineeringAnimation