Reversing gear set

This intriguing mechanism features a constantly rotating input (orange gears) driving an output gear (small white gear) which rotates first in one direction and then in the reverse direction. This is shown (not very well) in this video: http://youtu.be/_0XB8Rn9RqA
Shown much more clearly in this animation: https://youtu.be/jA5n5GlCb5U
which was created in Blender 2.76 using the Physics engine. If you look closely at the animation you will see that the trailing tooth of the central gear, and that of the ring gear have been reduced in height. Unless this is down the physics animation won't work BUT the animation is using a planet gear of 31mm diameter. I've uploaded a planet with an O/D of 29mm which is a bit sloppy in its engagement with the other gears but probably won't require modification of the trailing teeth.
The design was inspired by this video: https://www.youtube.com/watch?v=3aobPgGzB-U&list=PLB0IDKx1j2rxVpbfnvui1v5lDLPlaB2gx&spfreload=1

Designed in MOI. Printed in D