About this 3D model

My rendition of yet another very old, and very simple, children's toy. Sure there is the possibility of potential, kinetic and mass inertia energy involved (try it with just the axle), and as such there most certainly must be some sort of physics lesson that can be derived from somewhere in this thing, but most important, the grandkids love it, which of course is why I made it. Video of prototype is here: https://www.youtube.com/watch?v=5gkM4ybjZo4. Designed using Sketchup Make 2015, and printed in PLA on a Makerbot Replicator 2 using Makerware 2.3.3.42 "Standard" Settings (.2mm layer height, 2 shells, 10% infill).