Made this child's train set for my two year old. It's all scrap cherry. The wheels are 1.25" in diameter while the bases are 1.5" wide.
The wheels are nailed into pre-drilled holes.
The hitches are sort of a half lap joint with the top half holding a dowel.
Dude, have you seen how children play with toys? I was absolutely brutal with my wooden train. Shouldered corners might have helped it. I, too, love this train.