Lab Manual | Study of inversions of 4-Bar Mechanism, Single and Double Slider Crank mechanism

To study inversions of 4 Bar Mechanisms, Single & double slider crank mechanisms.

APPARATUS USED : – Models of 4 Bar Mechanisms, Single & double slider Crank mechanisms

THEORY: –

1. Definitions of 4 Bar Mechanisms, Single & Double slider crank mechanisms.

2. Classifications of 4 Bar Mechanisms, Single & Double slider crank mechanisms

3. Diagrams of 4 Bar Mechanisms, Single & Double slider crank mechanisms

4. Working & Construction of 4 Bar Mechanisms, Single & Double slider crank mechanisms.

5. Applications of of 4 Bar Mechanisms, Single & Double slider crank mechanisms

FOUR BAR MECHANISM :- A four bar link mechanism or linkage is the most fundamental of the plane kinematics linkages. It is a much preferred mechanical device for the mechanization and control of motion due to its simplicity and versatility. Basically it consists of four rigid links which are connected in the form of a quadrilateral by four pin joints. A link that makes complete revolutions is the crank, the link opposite to the fixed link is the coupler and the fourth link a lever or rocker if oscillates or an another crank, if rotate. By fixing the link :-

· Shortest Link Fixed

· Link opposite to Shortest Link fixed

INVERSIONS OF SINGLE SLIDER–CRANK CHAIN :-

Different mechanisms obtained by fixing different links of a kinematics chain are known as its inversions. A slider –crank chain has the following inversions :-

1. First inversion (i.e; Reciprocating engine and compressor) – this inversion is obtained when link 1 is fixed and links2 and 4 are made the crank and the slider respectively.

2. Second inversion (i.e., Whitworth quick return mechanism and Rotary engine) – fixing of link 2 of a slider – crank chain.

3. Third inversion (i.e., Oscillating cylinder engine and crank & slotted – lever mechanism)- By fixing link 3 of the slider crank mechanism.

4. Fourth inversion (Hand pump) – if link 4 of the slider crank mechanism is fixed, the fourth inversion is obtained.

DOUBLE-SLIDER CRANK-CHAIN:

A four-bar chain having two turning and two sliding pairs such that two pairs of the same kind are adjacent is known as a double-slider-crank chain. The following are its inversions: 1. First inversion (i.e., Elliptical trammel)

2. Second inversion (i.e., Scotch yoke)

3. Third inversion (i.e., Actual Oldham’s coupling)

OBSERVATION & CONCLUSION: –

(a) Comparison between 4 Bar, Single & Double slider cranks mechanisms.

(b) Type of Motion to be named.

APPLICATIONS :-

· In reciprocating engine.

· In reciprocating compressor.

· In Whitworth quick – return mechanism and Rotary engine.

· In Oscillating cylinder engine and crank & slotted-lever mechanism.

· In hand pump.

· In scotch yoke.

VIVA-QUESTIONS :-

1. What are the of inversions of four bar mechanism & give their applications also ?

2. What are the of Inversions of single slider crank mechanism & give their applications also ?

3. What are the of Inversions of Double slider crank mechanism & give their applications also ?

4. Define degree of freedom & give examples ?

5. Define Kutzbach & grubler’s criterian.