Quiz – 1

In a planar mechanism, all particles describe plane curves in space and all the curves lie in a single or parallel planes. The relative motions are constrained to a single plane. Hence, the planar mechanism is a 2 – D mechanism.

Hooke’s universal joint is an example of spherical mechanism as the relative motion of the particles is three dimensional, whereas the rest are examples of planar mechanisms (the relative motion is two dimensional.)

In a spherical mechanism, the locus of every point is a curve contained in a spherical surface. These spherical surfaces are concentric.

The relative motion can be random in a spatial mechanism. It is not necessary for the motion transformation to be coplanar or concentric. Spatial mechanism can move in any of the three dimensions.

Planar mechanisms are restricted in a single plane and spatial mechanisms have no such restriction. The relative motion between particles in a spatial mechanism is not in the same or parallel planes. Thus, planar mechanisms are 2 dimensional whereas spatial mechanisms are 3 dimensional.

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In this, due to the rotation of the crank about the fixed centre A, the lever oscillates about the point D. Point E of the lever CDE is connected to a piston rod which reciprocates due to the rotation of the crank i.e. this mechanism converts rotary motion into reciprocating motion.

The displacement of the link is proportional to the pressure of gas or steam which acts on the piston rod. Thus, by calculating the amount of displacement, the pressure of the gas or steam can be calculated. This mechanism was used in Watt’s engines.

Single disc, conical and centrifugal are types of clutches. Clutches are used for the transmission of power in shafts and machines which are started and stopped frequently. It is also used to deliver power to the machine which are partially or fully loaded.

Considering uniform pressure theory in a single plate clutch, T = nµWR where R = 2(r₁³+ r₂³) / 3(r₁² + r₂²)
Thus, here, R = 2(100³ – 70³) / 3(100² – 70²) = 85.88 mm.