Here is a great video that address angled wheels on trains that makes it pretty clear how it works in the real world and for our toys.
Here's yet another video that demonstrates the principle using a hoses for the rails, and plastic bottles and plastic cups to simulate the wheels and axles.
There also is another video somewhere, but I can't find it, where a guy does similar experiments with a heavy cylinder rolling on a curved toy train track and off course it doesn't handle the curves at all. Then he does the same experiment where he uses a cylinder that is tapper on both sides and it perfectly navigates around the tight curve track because it can self adjust itself around the curve.
If I find that one, I'll post it here.
