Every train car I can remember has its axles arranged like the photo. Two are put very close together in one chassey, and two more the same way at the other end.
But why do that? If you want 4 axles, isn't it better to spread them out evenly like I drew? Or if you just want axles at the ends, why not just have 2 total instead of 4 unevenly spaced ones?
So why are there unevenly spaced axles? If you want only 2 pivot points, why not just have 2 axles total (which would be spread evenly if they are equal distances from the ends of the car)? If you want 4 axles (presumably for load bearing), why not spread the axles evenly?
I could not find this answer via googling. It might help if I knew the exact terminology of that chassey holding two axles.