Textbook of Engineering Drawing, Second Edition

6.18 Textbook of Enginnering Drawing-------------------

3. Draw a projector through o.


4. With centre bl. and radius equal to the length of side draw an arc intersecting the above
   projector at 01 •
   S. Join 01 , ai, (cl) and ol,bl forming the front view.
   (il) Construction (Fig.6.25b)


5. Draw the top view of the tetrahedron, keeping one side of the base parallel to and 10mm
   belowxy.


6. Obtain the front view of the base alblcl on to xy by projection.


7. Draw a projector through o.


8. Rotate ob about 0 to obi prallel to xy.
   S. Through b'. draw a projector to meet xy at b'..


9. With centre b'.and radius equal to the length of side, draw an arc meeting the projector
   through 0 at 01 •


10. Join ol-al, ol-bl, Ol-c', forming the front view.

o·

x--.::-r:::--t----~_

x -Tt7---'-I-:7--~~--y

~ ~,

c

a a

(a) (b)

Fig 6.25

Problem: Draw the projections of a pentagonal pyramid of side of base 30mm and axis

50mm long when its axis is perpendicular to V:P and an edge of its base is perpendicular to

H.P

Construction (Fig. 6.26)

1. Draw the front view of the pyramind which is a pentagon, keeping one of its sides
   perpendicular to xy.


2. Obtain the top view by projection keeping the axis length equal to SOmm