INVERSIONS OF SLIDER CRANK MECHANISM
Different mechanisms are obtained when we fixed different links of a Kinematic chain and the phenomenon is known as inversion of mechanism. A slider crank mechanism has the following inversions.
First Inversion
This inversion is obtained when link 1 is fixed (as shown in fig ) and links 2 and 4 are made the crank and the slider respectively.
Application: This mechanism is commonly used in I.C. engines, steam engines and reciprocating compressor mechanism.
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| reciprocating engine |
Second Inversion
By fixing link 2 of a slider mechanism gives second inversion. Rotary engine mechanism or gnome engine is the application of second inversion. It is a rotary cylinder V – type internal combustion engine used as an aero engine. The rotary engine has generally seven cylinders in one plane. The crank (link 2) is fixed and all the connecting rods from the pistons are connected to this link. In this mechanism when the pistons reciprocate in the cylinders, the whole assembly of cylinders, pistons and connecting rods rotate about the axis O, where the entire mechanical power developed, is obtained in the form of rotation of the crank shaft.
Application: Rotary engine mechanism or gnome engine
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| rotary engine |
Third Inversion
By fixing the link 3(connecting rod) of the slider crank mechanism we can obtain third inversion (as shown in fig.). It is used in hoisting engine mechanism and also in toys. In hoisting purposes, its main advantages lie in its compactness of construction as it allows simple method of supplying steam to the cylinder.
Application: It is used in hoisting engine mechanism and also in toys
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| oscillating cylinder engine |
Fourth Inversion
By fixing the link 4 of the slider crank mechanism we can obtain the fourth inversion of slider crank. Fixing the slider means that the slider should be fixed in position and also should be fixed in respect to rotation. In this case, the cylinder will have to be slotted to give passage to piston pin of connecting rod as the cylinder slides over the piston. Due to this difficulty, the shapes of the cylinder and piston are exchanged as shown in figure below.
Application: hand pump
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| pendulum pump |