Slider - Crank Mechanism

Slider - Crank Mechanism ◺O₂BC











Slider - Crank Mechanism : Let us consider a 4R- planar mechanism ▢ O₂BCO₄ wherein one of the kinematic pairs at C, that is, revolute pair at C goes to infinity along a vertical direction. Consequently, that kinematic pair at C 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, B and C and the kinematic pair between link - 4 and link 1 is prismatic pair.

In the Slider - Crank Mechanism ◺O₂BC, 

Fixed Link O₂C = Frame 

Driving Link / Input Link C = Sliding element 

Motion Transfer Link BC = Coupler OR Connecting Rod

Driven link / Output Link O₂B = Crank  

Coupler BC is attached to a sliding element C 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 C undergoes pure translatory motion.

Coupler BC transforms sliding motion to crank O₂B. Coupler Link BC itself undergoes both translation and rotation simultaneously.

Crank O₂B is rotatably mounted on the frame O₂C at an instantaneous angular position of 𝝷₂ with respect to the x - axis of an absolute reference system fixed to link - 1 at C and can perform complete revolutions.

Crank O₂B is Output Link and its desired Output Motion is that of Continuous Rotation. Crank O₂B 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 C passes through it.

Example: Ordinary Internal Combustion Engine Mechanism 

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