Topic: General
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They have a center.
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They have 2 axis's, the Major and Minor and they are of different lengths.
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If both axis's are equal it's called a circle.
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They have two points located on the Major Axis called "Focus Points". If both focus points occupy the same "point" then it's a circle.
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Half of either of these axis's is referred to as "Semi".
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They can be bound by a rectangle who's sides are equal to the Major and Minor axis's of the ellipse.
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Which can be used to locate the foci on the Major Axis.
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One equal to the Semi-Minor Axis.
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Which defines the radius of the cylinder that the plane intersects to form the ellipse.
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An Ellipse is commonly defined as the locus of points P such that the sum of the distances from P to two fixed points F1, F2 (called foci) are constant. That is, distance[P,F1] + distance[P,F2] == 2 a, where a is a positive constant.
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Try not to let the previous one trouble you to much ;-)
Now when it comes to making a trammel you put some of these principles to work. There are basically two type of trammels you can make:
- One with the "scribe" at the end followed by the two axis lengths.
- Or one with the "scribe" in between the two axis lengths.
- Trammel in action.
- The real work is making a setup that you can use with either a router of saw to cut the ellipse out.
- How to Plot a Large Ellipse
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