The Scotch yoke mechanism 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. In many internal combustion engines, linear motion is converted into rotational motion by

means of a crankshaft, a piston and a rod that connects them. The Scotch yoke is considered to be a more efficient means of producing the rotational motion as it spends

more time at the high point of its rotation than a piston and it has fewer parts.

Introduction

• Scotch Yoke mechanism is a simple type of mechanism which converts circular motion into reciprocating motion as discussed in construction part above. The power is supplied to theDc motor, shaft and crank attached to the shaft start rotating. As the crank rotates the pin slides inside the yoke and also moves the yoke forward. When the crank rotates through in clockwise direction the yoke will get a displacement in the forward direction. The maximum displacement will be equal to the length of the crank. When the crank completes the next of rotation the yoke comes back to its initial position. For the next of rotation ,yoke moves in the backward direction. When the crank completes a full rotation the yoke moves back to the initial position. For a complete rotation of crank the yoke moves through a length equal to double the length of the crank. The displacement of the yoke can be controlled by varying the length of the cranck.

Working principle

Scotch Yoke Mechanism Working Animation

• Position A:- Let us assume position a indicates beginning position of pin & position given in diagram be the initial position of connecting rod (#1) & (#2).

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• Position B:-As the disc rotates, slot reciprocates and the position of connecting rod changes, connecting rod (#1) moves upward and connecting rod (#2) also moves upward from its initial position.

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• Position C:-As the disc rotates further both the connecting rods (#1) & (#2) get to their extreme upper post position.

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• Position D:-After position C the connecting rods (#1) & (#2) starts to move downward as the disc further rotates.

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• AFTER ALL POSITION (A,B,C,D) THE DISC ,THE PIN & CONNECTING RODS (#1,#2) COMES TO ITS INITIAL POSITION AGAIN AFTER COMPLETION OF A COMPLETE CYCLE.

• DIAMETER:-12 INCHES

• SLOTTED BAR LENGTH:-12 INCHES

• SLOTTED BAR WIDTH:-3 INCHES

• LENGTH OF SLOT:-11 INCHES

• DIAMETER OF PIN:-1 INCHES

• DISTANCE OF PIN FROM THE CENTRE:-5

INCHES

Dimensional Analysis

This setup is most commonly used in control valve actuators in high-pressure oil and gas pipelines.

It is used in making double hack saw.It is used in reciprocating pumps to convert rotational motion into reciprocating motion required for piston movement.

It is used in beam engine pumps to convert rotational motion into reciprocating motion.

In making toys which have too & fro motion.

Applications

Application images

Mini Mechanical saw

Application images

TOYS

ENGINE

Direct conversion of rotary motion into reciprocating motion

Easy construction & operation

Can perform various operations such as cutting, slotting etc..

Process can be automated

Advantages

High wearing rate due to mechanical contact.

Less application in real life

Guide ways are necessary for proper reciprocating motion of arms.

Disadvantages