1. CLASSIFICATION OF INVERSION INVERSION OF FOUR BAR CHAIN MECHANISM
KINEMATICS OF MACHINE
TOPICS:
INVERSION
CLASSIFICATION OF INVERSION
INVERSION OF FOUR BAR CHAIN MECHANISM

2. TOPICS: WHAT IS INVERSION? CLASSIFICATION OF INVERSION FOUR BAR CHAIN
FOUR BAR CHAIN’S INVERSION

3. MECHANISM
When a kinematic chain with one of its link is fixed, is called a mechanism.
Example: type writer, clock work, etc.
A mechanism is a skeleton diagram of a machine to transmit the definite motions between various links.

4. INVERSION
When different links of a kinematic chain are used as a frame, relative motion of links are not altered, however, the absolute motion of such a mechanism is drastically changed.
The process of choosing different links of a chain for frame is called “ kinematic inversion”.
Therefore, if a mechanism has “n” number of links, we can obtain “n” number of inversions.
The behaviour and appearance of such mechanism is different. Each mechanism thus obtained is called an “inversion of kinematic chain”

5. CLASSIFICATION OF INVERSION
Inversion of four bar chain
Inversion of slider crank kinematic chain
Inversion of double slider crank kinematic chain

6. FOUR BAR CHAIN
A four-bar linkage, also called a four-bar, is the simplest movable closed chain linkage.
It consists of four bodies, called bars or links, connected in a loop by four joints.
In a four bar mechanism the link on which input motion is applied is known as driver.The output motion link is follower and the middle link connecting these two links is coupler link. The fourth links grounded. A four bar mechanism has 1 degree of freedom .
Generally, the joints are configured so the links move in parallel planes, and the assembly is called a planar four-bar linkage.

8. Inversions of four bar kinematic chain
The four bar chain mechanism consists of four turning pairs.
The four different mechanisms are obtained by fixing one link at a time.
Kinematically, all four inversions of kinematic chain are identical.
However there mobility can be varied by suitably changing the proportions of lengths of various links.

10. Types: Coupled wheel of locomotive(Double crank)
Beam engine(Crank and lever mechanism)
Watt’s engine indicator(Double lever mechanism)
Watts mechanism

11. Coupled wheel of locomotive(Double Crank)
If the links 2 and 4 are made of equal length in four bar chain, we get double crank quadric chain which is used to transmit the motion from one wheel to another of a locomotive.
Link 1 is fixed to maintain fixed centre distance between the wheels and link 3 represents coupling rod which connects two rods and is parallel to fixed link.
The mechanism is used to transmit the rotary motion of a wheel which acts as driver to another wheel mounted.

14. Beam engine(Crank and lever mechanism)
The function of this mechanism is to convert rotary motion of crank into oscillatory motion of lever and finally into reciprocating motion of piston.
Here, crank AB rotates about fixed centre A, lever CDE rotates about centre D and at end of lever E, additional linkages i.e. piston rod and piston is connected, which reciprocates the cylinder.

16. Watt's engine indicator(Double lever mechanism)
Link 1 is fixed, link 2 is ABC and link 3 is CDP, both act as levers.
Link BE and link ED form link 4 since no relative motion between them.
The point E is connected to piston of indicator cylinder i.e. displacement is proportional to pressure of the gas.

19. WATTS MECHANISM
This mechanism is used to trace a straight line roughly.
It has four links of which one of the link is fixed.
The rest two can oscillate about the centres.
The point p1 is such that p1B/p1C = DC/AB.
Then for small oscillation of DC and AB the point P1 will trace a straight line roughly.

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