Theory The slider crank mechanism is one of the most basic forms of closed loop mechanisms, it is modification of the basic four bar chain. It has a single degree of freedom and is often used to convert rotary motion into linear motion by varying link lengths. It is, usually, found in reciprocating steam engine mechanism.

The theory of the slider-crank mechanism is based on the principles of kinematics, which is the study of motion without considering the forces that cause it. In a slider-crank mechanism, the motion of the crank and connecting rod is described by kinematic equations that relate the two components’ position, velocity, and acceleration.

With an in-line crank slider, the motion of the crank and follower links is symmetric about the sliding axis. This means that the crank angle required to execute a forward stroke is equivalent to the angle required to perform a reverse stroke. For this reason, the in-line slider-crank mechanism produces balanced motion.

The slider, for example, can be a piston in a cylinder or a linear drive element in a machine. Thus the primary input is either a force applied to the slider or a torque applied to the crank arm. This is an in-line configuration where the linear axis of slider motion intersects the axis of rotation of the crank arm.