Textbook of Engineering Drawing, Second Edition

--------------------_GeometricaIContructions 4.25

Parabolic Curve

The parabolic curve fmds its application for reflecting surfaces oflight, Arch forms, cable forms in
suspension bridges, wall brickets of uniform strength, etc.

The paraboloid reflector may be used as a solar heater. When it is properly adjusted, the sun
rays emanating from infinite distance, concentrate at the focus and thus produce more heat. The
wall bracket of parabolic shape exhibits equal bending strength at all sections (Fig.4.37)

p

Fig. 4.37 Wall bracket ofunifonn strength

Hyperbola

A rectangular hyperboler is a graphical reprentation of Boyes law, PV=Constant. This curve also

finds its application in the design of water channels.

Problem : Draw an ellipse with mojor axis 120 mm and minor axis 80 mm. Determine the

eccentricity and the distance between the directrices.

Construction (Fig. 4.38)

120

161

Fig. 4.38