Sketching Ellipse Question

[nofalloff]

Is there an easy way of defining an ellipse in sketcher by dimensioning its circumference and either Rx or Ry value?

 

[mihaicretu]

In Sketcher click on the arrow near the circle button. The button will expand, and the last option there is the ellipse button. The default dimensioning is Rx & Ry. And you get a brand new ellipse.

 

[nofalloff]

In Sketcher click on the arrow near the circle button. The button will expand, and the last option there is the ellipse button. The default dimensioning is Rx & Ry. And you get a brand new ellipse.

Thanks but I know how to sketch an ellipse. What I need is to sketch one with a specific circumference. I need to then make that value a locked dimension so that I can vary either the Rx or Ry dimension to suit.

 

[fiebigc]

You should try and constrain the major and minor axis in the relations menu. The circumference of an ellipse can be estimated by
C = 2

sqrt((a²+b²)/2)
</pre>
If you replace "a" and "b" with the dimension reference of your ellipse and keep "C" a constant you should be able to constrain your ellipse.

I looked it up and it turns out there is not easy equation for an ellipse, it actually requires some calculus to determine. The equation I gave you is an approximation. I would recommend doing you own research for an equation your most comfortable with.

Edited by: fiebigc

 

[anwyl]

Sketch the ellipse. Then, while in sketcher, select the ellipse and choose Edit/Convert To/Perimeter. Select either Rx or Ry to be driven by the perimeter dimension.

 

[nofalloff]

Sketch the ellipse. Then, while in sketcher, select the ellipse and choose Edit/Convert To/Perimeter. Select either Rx or Ry to be driven by the perimeter dimension.

Bingo!
thanks

Fiebigc: I started down the rout you suggested but it was becoming a bit too complicated and a PIA. thanks for your help though.

 

[design-engine]

I use four conics instead. Much more control.