Isometric Projection of an Arc

ISOMETRIC PROJECTION OF AN ARC

An arc may be drawn in isometric view either in vertical (or) horizontal position. To draw arc in vertical position either left isometric (or) right isometric plane may be used and to draw the arc in horizontal position top isometric plane is used. Consider an arc of Radius R with subtended angle 90°, shown in Fig. 17.13(i) to be drawn in isometric view.

(a) Right Isometric

1. Draw a horizontal line of short length and locate the point B.

2. Draw the isometric axes BA and BC such that BA = b'a' and BC = b'c'.

3. Draw the isometric lines CO and AO to intersect at O.

4. Draw the tangents (ie., at 90°) to the lines BC and BA to intersect at O1.

5. With O1 as centre and O1C (or O1A) as radius, draw an arc passing through the points A and C.

Note that in isometric projection, Radius of arc and the angle subtended at centre are not the same of actual dimensions R and 90° respectively.

(b) Left Isometric

Follow the procedure as above but drawing the isometric axis AB at 30° to the left of the origin A.

(c) Top Isometric 

An arc shown in top view is drawn in top isometric as below.

1. Draw a horizontal line of short length and locate the view point B.

2. Draw the isometric axes BC and BA inclined at 30° each97 to the horizontal.

3. Construct the Rhombus BCOA.

4. Draw the tangents to the intersect at O1.

5. With O1 as centre and O1C (or O1A) as radius, draw an arc passing through the points C and A. 

Note that in top isometric also, Radius of arc and the angle subtended at centre are not the same of actual dimensions.