Slider crank and crank rocker mechanisms

Slider crank chain: This is a kinematic chain having four links. It has one sliding pair and three turning pairs. Link 2 has rotary motion and is called crank. Link 3 has got combined rotary and reciprocating motion and is called connecting rod. Link 4 has reciprocating motion and is called slider. Link 1 is frame (fixed). This mechanism is used to convert rotary motion to reciprocating and vice versa.

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Inversions of slider crank chain: Inversions of slider crank mechanism is obtained by fixing links 2, 3 and 4.Rotary engine – I inversion of slider crank mechanism. (crank fixed)

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Whitworth quick return motion mechanism–I inversion of slider crank mechanism.

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Crank and slotted lever quick return motion mechanism – II inversion of slider crank mechanism (connecting rod fixed).

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Oscillating cylinder engine–II inversion of slider cranks mechanism (connecting rod fixed).

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Double slider crank chain: It is a kinematic chain consisting of two turning pairs and two sliding pairs.

Scotch –Yoke mechanism. Turning pairs – 1&2, 2&3; Sliding pairs – 3&4, 4&1.

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Inversions of double slider crank mechanism:

Elliptical trammel. This is a device which is used for generating an elliptical profile.

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In fig.4, if AC = p and BC = q, then, x = q.cosθ and y = p.sinθ.

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. This is the equation of an ellipse. The path traced by point C is an ellipse, with major axis and minor axis equal to 2p and 2q respectively.

Oldham coupling. This is an inversion of double slider crank mechanism, which is used to connect two parallel shafts, whose axes are offset by a small amount.

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Displacement: All particles of a body move in parallel planes and travel by same distance is known, linear displacement and is denoted by ‘x’.

A body rotating about a fired point in such a way that all particular move in circular path angular displacement and is denoted by ‘θ’.

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