Algodoo

You should probably use more frequency for your scenes. Physics are very crudely calculated in Algodoo when you use 60 Hz, adding for example stretchable axles and objects that penetrate into each other (let's not even talk about water), but low frequencies allow for more objects without lag - if you use very few geometries on your scenes, like, less than 100, then you should consider cranking the frequency bar up to 1200 Hz as it won't affect performance(Gear at the upper left corner -> Simulation -> Simulation frequency). Also use very high density on objects thet need accurate collisions, if you want you can make the test: stack two objects, add a thruster that pushes the upmost object down and see how much force the system can withstand without doing weird things; then increase the density up to 50 or 100 and try again

Nice scene. Algobox is ruined now sadly

Well, since "The Linkage" made a comment, I will too. You are off to a good start. Unfortunately, marble racers may drown your scene. It might make sense to put this in the "Technical" group. If you desire better gears then use Spur Gear Generator II.

well done!
10.