Summary

I made the original train for my grandson. He pointed out that the wheels needed those connecting rod things! So I reworked the wheels a little bit so they could be added. You might need to ream the holes out a little bit it they are too tight, it depends on how well your printer is calibrated. When you assemble them remember that the rods on one side need to be 90 degrees out of phase in order to turn properly without binding.
I also made the wheels slightly smaller since they hit the body when I made the model.