remember that loop-da-loop ramp?

I may have talked about this in an old post.. turns out to keep centrifical force constant, a loop is not circular, but rather an ellipse:
http://gizmodo.com/why-roller-coaster-loops-are-never-circular-1549063718

This is mostly done for the purpose of reducing g's on the human body.  I figure if you're talking about a pinball with constant velocity (IE: same force holding it against the ramp as it goes around), this is also ideal.  If the force changes, that could be what makes it >pop< out of the track.

SO!  Now that 3d printed pinball parts are popping out of my machine, it's time to revisit that concept in PLA.  So let's look at the loop ramp I started before:

From the side, it's a perfect circle:

We want an ellipse.  But how to model that?  Solidworks can model screws of all kinds, but they are based on a round shape.  I found one complicated tutorial of how to create something, but then  I found an easy out.  Take my existing shape, and use the scale command but only in the Y-axis:

Going to print it tonight since it's a 4.5 hour job even on fast speed.  I'm going to try to print as a single piece without support.  In theory because of it's shape it should be self supporting.