Dutch Train NS Trein 1 to 500 Free 3D print model

This is a train from the NS in the Netherlands. I made a solid STL from a SketchUp file from the Warehouse:

https://sketchup.google.com/3dwarehouse/details?mid=ffef9751ec79f8bca097e7ac87bcdb34&prevstart=0

I tried to fix as much as possible and scaled it down to 1:500 but there are hollow spaces around the wheels. Because of that there are some really thin walls so I don't know if this printable yet, maybe someone can fix this.