The Scotch yoke mechanism converts rotational motion to reciprocating motion, or vice versa, using a sliding yoke with a slot that engages a pin on the rotating part. It is more efficient than a crankshaft at producing rotational motion as it spends more time at the high point of rotation and has fewer parts. The mechanism finds applications in control valves, hacksaws, reciprocating pumps, and toys where reciprocating motion is required.

1. 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

2. • 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

3. Scotch Yoke Mechanism Working Animation

4. • 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).
•
• 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.
•
• Position C:-As the disc rotates further both the connecting rods (#1)
& (#2) get to their extreme upper post position.
•
• Position D:-After position C the connecting rods (#1) & (#2) starts to
move downward as the disc further rotates.
•
• 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.

5. • 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

6. 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

7. Application images
Mini Mechanical saw
Application images

8. TOYS
ENGINE

9. 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

10. High wearing rate due to mechanical contact.
Less application in real life
Guide ways are necessary for proper
reciprocating motion of arms.
Disadvantages