Solved Numericals of Engineering Drawing – ED 22 Solved Questions

Q20: A cone of base diameter 50 mm and axis 60 mm is resting on its base on the H.P. A section plane perpendicular to V.P. and inclined at 45⁰ to H.P., bisects the axis of the cone. Draw the development of its lateral surface.

Solution:

Steps :

(i)  Here generators  o ‘2’, o ‘3’, o ‘4’, o ‘6’, o ‘7 ‘  and  o ‘8’  are not of the true length. Therefore, intersection points on these generators need to be projected on the generator o‘1’ which is of true length. Point b ‘, c ‘, d ‘ ……e ‘ are thus projected as b “, c “, d “….. on generator o ‘1’.

• The angle subtended by an arc at the center is given as, ^r_s  360⁰ .
• Where, s   slant height of cone = 65 mm  o ‘1’ , r  radius of base = 25 mm,_{Theta = 25/ 65}  X 360=  138.5⁰
  • Mark point O and draw an arc of circle of radius = o‘1’ with angle 5⁰ . Divide the arc 1o1 into 8 equal parts.
    • Mark point A on O1 such that OA o ‘ a ‘ and point B on O2 such that OB O ‘ b “. Similarly, mark point C , D , E , F , G and H on O 3, O 4, O 5, O 6, O7 and O8
  •  Draw smooth curve passing through points A, B, C, D….. etc.