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The trammel method | Up
Illustrator Draftsman 3 & 2 - Volume 2 Standard Practices and Theory | Next
Conjugate diameter method-Cont. |
Ellipse Construction, Continued
Concentric
In the concentric diameters method of ellipse construction, you use the major
diameters
method
and minor axes as diameters for concentric circles on a common horizontal
and vertical axis intersecting at right angles. By drawing a diagonal across
both circles and plotting subsequent points, you can construct an ellipse.
To construct an ellipse using the concentric diameters method, use this table:
Step
1
2
3
4
5
6
7
Action
Draw horizontal (AB) and vertical (CD) axes that intersect at right
angles (0).
Using the length of the major and minor axes as diameters, lay out
two concentric circles with 0 as a common center.
Draw a diagonal (XX) at any common angle through the
circumferences of both circles passing through 0. Every diagonal
drawn provides you with four points along the circumference of the
ellipse.
From points X, draw lines XS parallel to CD and perpendicular to
AB .
Where XX intersects the smaller circle, draw HE parallel to AB
and perpendicular to CD.
Draw as many diagonals you feel necessary to adequately define
the ellipse.
Lightly sketch the ellipse through the points. Darken the outline of
the ellipse using french curves.
Continued on next page
2-50
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