'arc approximated' ellipse sketch?

[brrian]

The designers at my companyz love ellipses. We use them in a lot of the parts we create. Some of those will be sheet metal or other bent parts. I understand that you can't flatten an ellipse (maybe if it's a lofted bend... let's ignore that for now).

I want to set up a sketch that uses arcs to approximate an ellipse. I have a sample I found somewhere that demonstrates this; however it was not set up to be editiable--changing dimensions turns it red.

Do any of you have a method of creating an ellipse (in a sketch) made up of arcs? I know there are a few ways to do it (Stevens method, Five-center arch) but I want something that I can adjust without it failing. I'll then save it in our library for the drafters to use.

Thanks, & let me know if you have any additional questions.

Brian

 

[Theophilus]

"Approximated" ellipses are not very elliptical, but a series of arcs. You might be able to link the dimensions between the arcs with a series of equations, such that moving one dimension will cause the others to remain tangent and reduce or enlarge (good luck).

What sort of designers are you talking about who use these things? If industrial designers, I don't think they'll like the approximated bulbous shapes of the arcs anyway (I don't).

You mentioned something about flattening an ellipse. I think you'll have more problems if the purpose is to flatten the arcs, since you have many more sketch elements that need to play nice together.


Jeff Mowry

http://www.industrialdesignhaus.com

Reality is no respecter of good intentions.