Rotating an ellipse 1

[treddie]

Howdie all.

Never had to consider this problem before until now. There is apparantly no way to rotate an ellipse in Sketcher except for 90 deg rotations, which is a huge limitation. Is there a way to draw an ellipse using some other method? The only problem I see with that is that there has to be an entity in Sketcher first for a relation to refer to. Since that entity would have to be an ellipse that can't be rotated I'm back to square one, again. I will check into using equations, in the mean time.

Thanks,
Treddie

 

[dgallup]

Rules for Creating an Ellipse
An ellipse has the following properties:

The center point of an ellipse behaves the same as the center of a circle, and can be referred to by dimensions and constraints.

The axes of an ellipse are parallel to the horizontal and vertical axes of the sketch. An ellipse cannot be slanted.

Ellipse is defined by two radii: x-radius and y-radius. The length of the horizontal axis from the center of the ellipse to the ellipse itself is called the x-radius in Sketcher. The vertical half-axis is called the y-Radius. These radii can be dimensioned and can be referred to by Equal Radius constraints.

The center of the ellipse and the ellipse itself will snap to constraints while the ellipse is being sketched. Some of the constraints that can be applied to an ellipse are Tangency, Point on Entity, and Equal Radii.

 

[dgallup]

You can make a rotated ellipse using 4 conic arcs. Draw a set of angled mutually perpendicular centerlines. Draw and dimension the first conic arc. Make the end points perpendicular to the centerlines and set rho to .414. Mirror the conic about both centerlines.

 

[treddie]

That did it. Thanks!
My problem was I was trying to make an ellipse from two half segments, but that would have driven (b) to infinity and (rho) would have been undefined.

Much thanks for steering me in the right direction.

treddie

 

[cadcamguy]

You can rotate a ellipse, the trick is you have to create your ellipse as a sec. first

then insert shared data after you draw a angled centerline in your sketch...yes sketch into a sketch

set your rotation on the insert the same as your cline and trajpar away with vss
elliptical corkscrews..sd4=trajpar*360*num_of_turns

change your shape as it goes for the ride..use the sd values of the ellipse

pretty shapes...sort of organic looking...totally useless to me but fun to look at

 

[cadcamguy]

http://media10.filewind.com/g.php?filepath=9111

 

[cadcamguy]

it's not the ellipse under circle...it's a spline with the values.
And while close they are a little different. If you overlay you can see the difference, pretty darn close