Slider - Crank Mechanism

Slider - Crank Mechanism : Let us consider a 4R- planar mechanism ▢ O₂ABO₄ wherein one of the kinematic pairs at B, that is, revolute pair at B goes to infinity along a vertical direction. Consequently, that kinematic pair at B is converted to a prismatic pair and what one get is a 3R - 1P mechanism. In 3R-1P mechanism, there are 3 revolute pairs at O₂, A and B and the kinematic pair between link - 4 and link 1 is prismatic pair.In the Slider - Crank Mechanism ◺O₂AB, 

Fixed Link O₂B = Frame 

Driving Link / Input Link B= Sliding element 

Motion Transfer Link AB = Coupler OR Connecting Rod

Driven link / Output Link O₂A = Crank  

Coupler AB is attached to a sliding element B that is Input Link and nature of its Input Motion that is available is in the form of Continuous to- and fro- rectilinear OR sliding motion. Slider B undergoes pure translatory motion.

Coupler AB transforms sliding motion to crank O₂A. Coupler Link AB itself undergoes both translation and rotation simultaneously.

Crank O₂A is rotatably mounted on the frame O₂B at an instantaneous angular position of 𝝷₂ with respect to the x - axis of an absolute reference system fixed to link - 1 at B and can perform complete revolutions.

Crank O₂A is Output Link and its desired Output Motion is that of Continuous Rotation. Crank O₂A undergoes pure rotary motion with output angular velocity (𝞈₂).

O₂ is "crank pivot" and the centerline of the slide way within part of Frame at B passes through it.

Example: Ordinary Internal Combustion Engine Mechanism