Scotch Yoke Mechanism – Animation , Advantages and Application

What is Scotch Yoke Mechanism ? 

Basic of Scotch Yoke Mechanism

It is  one of reciprocating motion mechanism, it should be convert an rotary motion into sliding of linear motion. When the Piston or reciprocating part to directly coupled together for the sliding of yoke  including a slot. That engages a pin at reciprocating part. When the internal combustion engine to convert rotary motion into linear motion by means of crankshaft rotation.Where the Piston and connecting rod should be connected together.  The Scotch Yoke Mechanism to be consider for more efficient because of the rotational motion to spent more time at high point of it rotate than Piston part.

Read More : Inversions Of Single slider Crack mechanism-Rotary, Pendulum, Quick return Mechanism

Concept of mechanism
The Scotch yoke is a reciprocating motion mechanism, converting the linear motion of a slider into rotational motion or vice-versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part. The shape of the motion of the piston is a pure sine wave over time given a constant rotational speed.

scotch yoke mechanism
scotch yoke mechanism

This mechanism is used for converting rotary motion into a reciprocating motion. The inversion is obtained by fixing either the link 1 or link 3. In Fig, link 1 is fixed. In this mechanism, when the link 2 (which corresponds to crank) rotates about B as centre, the link 4 (which corresponds to a frame) reciprocates. The fixed link 1 guides the frame.

Working principle of Scotch Yoke Mechanism

It is a simple mechanism, the rotary motion of pin convert into linear motion. First, the power supplied to be connected in DC motor, when the shaft to start in rotation moment, now the crank rotate the pin slider inside of yoke part and also move in forward direction. When the Crank will be rotate in clockwise direction and yoke will be getting displacement moment at forward. The maximum displacement of yoke depends upon the length of Crank.

The crank is completed the clockwise Revolution at the same time the Yoke sliding completely moved in forward. When this position take more time to start return stork. After spent time, the crank will be rotate in continuously it to be come back in initial position of rotation. So the Yoke move in backward direction and come back for initial position. Therefore the crank has full Revolution to be completed,At the same time the Yoke will be complete the forward and backward movement of Sliding. By means of the full revolution of Crank, the Yoke will be sliding through equal of double length of Crank. The Yoke displacement can be controlled by varying of crank length.

Animation Of Scotch yoke Mechanism : 

Application Of Scotch Yoke Mechanism are :


Scotch yoke Operated Flapping wing Mechanism Ornithopter | Mechanical Video

Development of Multi Purpose Machine With Scotch Yoke Mechanism


Double acting Hack saw Machine Operated By Scotch Yoke Mechanism

Advantages Of Scotch yoke Mechanism :

  • Easy construction of assembly and operation.
  • Used to perform of cutting, sliding and etc.
  •  It is a directly convert method of rotary into Linear.
  • High torque to be made with small size of cylinder.
  •  It spent high time in top dead center, so improve engine efficiency.

Disadvantages of Scotch Yoke Mechanism

  • The high wear produced due to sliding friction and high contact pressure.
  •  List percentage of time spent in bottom center position, to reduce the below time in two stroke engine.
  •  The Piston motion is a pure sine wave will occur overtime give a constant rotation speed.
  •  It requires proper guide way for reciprocating motion of arm.
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