Coincident constraints to intersected object lost when editing parameters

[anonymousstudent]

In the model I'm attaching, the object (a tire modeled as a simple torus...)) intersects with a sketch to show its cross-section at a specific height. (That height is controlled by a parameter.)

In order to find a line tangent to the torus at that height, I approximated the shape of the cross-section with an ellipse (accurate enough for the general region of the tire and the range of intersecting heights I'm interested in).

However, when editing various parameters (including the height of the sketch plane that intersects the torus, the wheel and tire diameters, and the wheel's steering angle from the yz plane), the ellipse loses its coincident constraints to the profile of the torus.

How do I ensure that the ellipse stays "stuck" to the profile of the torus when changing the model parameters? Thanks!

[anonymousstudent]

Please refer to this attachment rather than the attachment to the original post (I forgot to reset one of the model parameters in that version)...

[davebYYPCU · Accepted solution]

Makes no difference to use either file, 

When changing that parameter, there are 3 projected points, that move in Sketch 6.

If the ellipse is coincident to those two relevant points it won't move when the parameters are changed because it is an ellipse.  Change to a spline it will work, as expected.

@jeff_strater, may be able to say why ellipses won't do the right thing.

[anonymousstudent]

Using a spline sounds good, thanks!

[rohit.bapat]

Hello @anonymousstudent 

Sorry to know that you are facing this problem. I have logged a ticket FUS-46107 to take a further look at this issue.

Thank you,

Best Regards

Rohit Bapat