Inversions of a Slider Crank Mechanism

A slider crank mechanism is a type of mechanism used in internal combustion engines, pumps, and compressors. It consists of a slider, a crank, a connecting rod, and a fixed frame. The slider moves back and forth along a straight line, while the crank rotates around a fixed axis. The connecting rod connects the slider and the crank, and its length determines the motion of the slider.

An inversion of a mechanism is a different arrangement of its links, such that it produces a different output motion. The slider crank mechanism has four possible inversions, each of which has a different application and functionality.

Inversion 1: Crank Sliding

In this inversion, the slider is fixed, and the crank rotates around a fixed axis. The connecting rod moves back and forth, producing a circular motion of the crank. This inversion is used in internal combustion engines, where the crankshaft rotates, and the piston moves back and forth in a straight line.

Inversion 2: Slider Crank

In this inversion, the crank is fixed, and the slider moves back and forth along a straight line. The connecting rod rotates around a fixed axis, producing a circular motion of the slider. This inversion is used in pumps and compressors, where the piston moves back and forth in a straight line, and the crankshaft rotates.

Inversion 3: Double Slider

In this inversion, both the slider and the crank move back and forth along straight lines. The connecting rod rotates around two fixed axes, producing a complex motion of the links. This inversion is used in some types of presses and stamping machines.

Inversion 4: Crank Rocker

In this inversion, the slider and the crank move back and forth along straight lines, but in opposite directions. The connecting rod rotates around a fixed axis, producing a rocking motion of the links. This inversion is used in some types of oscillating pumps and compressors.

Number of Inversions

The slider crank mechanism has four inversions, as explained above. However, the number of inversions that produce a useful output motion is three. The first inversion (crank sliding) produces a rotary motion of the crankshaft, which is useful in engines. The second inversion (slider crank) produces a reciprocating motion of the piston, which is useful in pumps and compressors. The fourth inversion (crank rocker) produces a rocking motion of the links, which is useful in some applications. The third inversion (double slider) produces a complex motion that is not useful in most applications. Therefore, the number of useful inversions of the slider crank mechanism is three.

Conclusion

The slider crank mechanism is a versatile mechanism that has four possible inversions. However, only three of them produce a useful output motion, which is a rotary motion, a reciprocating motion, and a rocking motion. The number of useful inversions is three, and the correct answer to the question is option C (4).