CONCEPT

It is based on Kinematics Of Machine.

Quick return Mechanism.

Four Bar Mechanism.

Before starting the Project we need to understand theconcepts of ‘Kinematics’ and ‘Dynamics’.

Kinematics of mechanisms is concerned with the motion ofthe parts without considering how the influencing factors(force and mass) affect the motion. Therefore, kinematicsdeals with the fundamental concepts.

Kinetics deals with action of forces on bodies.

Dynamics is the combination of kinematics and kinetics.

Dynamics of mechanisms concerns the forces that act onthe parts -- both balanced and unbalanced forces, takinginto account the masses and accelerations of the parts aswell as the external forces.

TERMINOLOGY

There are four basic terms in KOM.

•Links

•Pair

•Joints

•Degree of Freedom

Kinematic Link

• Each part of a machine, which moves relative to some

other part, is known as a kinematic link (or simply link) or

element.

Types of Link

Rigid link.

A rigid link is one which does not undergo any deformation while transmitting motion.Strictly speaking, rigid links do not exist. However, as the deformation of a connectingrod, crank etc. of a reciprocating steam engine is not appreciable, they can beconsidered as rigid links.

Flexible link.

A flexible link is one which is partly deformed in a manner not to affect the transmissionof motion. For example, belts, ropes, chains and wires are flexible links and transmittensile forces only.

Fluid link.

A fluid link is one which is formed by having a fluid in a receptacle and the motion istransmitted through the fluid by pressure or compression only, as in the case of hydraulicpresses, jacks and brakes.

Kinematic Pair

The two links or elements of a machine, when in contact with each other, aresaid to form a pair. If the relative motion between them is completely orsuccessfully constrained (i.e. in a definite direction), the pair is known askinematic pair.

Types of Kinematic Pair

Lower pair

◦ When the two elements of a pair have a surface contact when relative motion takes place and the surface of one element slides over the surface of the other, the pair formed is known as lower pair. It will be seen that sliding pairs, turning pairs and screw pairs form lower pairs.

Higher pair

◦ When the two elements of a pair have a line or point contact when relative motion takes place and the motion between the two elements is partly turning and partly sliding, then the pair is known as higher pair.

DEGREE OF FREEDOM

It is the number of inputs (number of independent coordinates) required to describe the configuration or position of all the links of the mechanism, with respect to the fixed link at any given instant.

Grubler’s equation:

n= DOF

l= No. of links

j= No. of lower pair

h= No. of Higher pair

QUICK RETURN MECHANISM

A quick return mechanism such as the one seen below is usedwhere there is a need to convert rotary motion into reciprocatingmotion. As the disc rotates the black slide moves forwards andbackwards. Many machines have this type of mechanism and inthe school workshop the best example is the shaping machine.

PROJECT DESCRIPTION

Aluminum material is used as its body.

Six legs.

Six links.

2 DC geared motor.

2 Crank.

Wooden Block.

9-12V battery.

Nuts and bolts

PROJECT PROTOTYPE

MID LEG

MECHANISM

FINAL PROTOTYPE