I found the s-curve by Transmit1 and want to make them more speedy.
The end of the curves are designed a little bit stiff, so they fit a little bit strong into the plates.
But so the Curve don't tip over when the ball goes through.
Here you can see the curve in slow action, the speed could be increased.
See also my cuves with slope here on Thingiverse.
I noticed that the S-Curve need a wide area, and it is not possible to bild a
distance plate next to the curve.
So I made a second version wich can go through 2 distance plates.
The picture shows how the marble can go through 2 plates.
In the video you can find how it works.