Question

The base diameter of a conical helix is 80 mm. The angle between the base and slanting side is 60 degrees. Pitch of helix is 6 mm. What is the height of helix and number of revolutions?

(a) 69.2 mm, 12

(b) 39.2 mm, 6

(c) 30 mm, 7

(d) 80 mm, 12

I got this question in an online quiz.

This is a very interesting question from Helix upon a Cone topic in section Curves used in Engineering Practice of Engineering Drawing

Answer 1

The correct answer is (a) 69.2 mm, 12

For explanation: Base radius = 40 mm.  Angle given is 60 degrees. Tan (angle) = height/ base, tan (60) = height/ 40, height = 40 x tan (60) = 69.2 mm, so at height of 69.2 mm the helix end. Number of revolutions = height/ pitch = 69.2 mm/ 6 mm = 11.5 approximately 12.