Construction of Helix

CONSTRUCTION OF HELIX

Data known : 

(i) Diameter of cylinder

(ii) Axis length

Example 11: Construct a helix of one revolution on a cylinder of diameter 60mm and height 90mm.

Procedure:

1) Draw reference axis XY, draw a circle of 60mm dia as top view and rectangle 60mm × 90mm above XY as front view of cylinder.

2) Divide the circle into any number of equal parts (say 12) and mark the divisions as 1, 2 etc., in anticlockwise direction (assume the cylinder rotates in clockwise direction). Draw 90 the vertical projectors through these points to the front view. Divide the front view also into same number of equal parts (say 12) horizontally and mark the divisions on the vertical edge of rectangle as 1', 2'.... etc. from bottom to top. (Assume lead (or) pitch = Axis length)

4) Mark the intersection point of projector drawn through 1 with horizontal line drawn through 1' as P1.

5) Similarly locate the other points P2, P3.... etc.

6) Join the points A, P1, P2, …, P11, P12 by a smooth curve which is the required helical curve.

Note:

1) Helical curve from P0 to P6 is drawn by a continuous curve where as the curve from P6 to P12 is drawn by a hidden curve since the points 1 to 6 are on the front side of observer and the points 7 to 12 are on the hidden side of the observer.

2) If the pitch (or lead) is not equal to axis length of cylinder, mark the given lead length on the front view and draw helix within this lead length (ie., divide lead length into equal parts) and proceed.