I'm trying to make differential in Google SketchUp using this tutorial http://support.ponoko.com/entries/21249896-Gears-and-Joints-with-SketchUp-Sketchy-Physics for gears modeling. But I have problem: gears don't collide with any objects (and other gears). What's wrong? How to fix this? How to make a bevel gear placed at 90 degrees relative to each other and conical cylindrical gears joints?
P.S. Is there something like SketchUp and SketchyPhisics in Linux?