Here is a view of the near end of the undercarriage. The red arrow points to the bell, there was one at each end and they were activated by a floor mounted pedal. The small round item seen just under the arrow is the clapper that rang the bell. The blue arrow is pointing to the pivot for the coupler, the arm is pointed down to the left and you can see a spring near the pivot, and the curved rail the coupler traveled on at the left of the photo. The green arrow is pointing to the pin that holds the car body on the trucks. The body just sat on the trucks with these pins seated on a hole on the top center of each truck. Since the trucks had to turn the pins are mounted in the center of the car. If you follow the arched frame holding the pin you will see a flat curved metal plate, this plate rode on a large solid roller bearings set in the trucks allowing the trucks to turn smoothly under the body. I have two of the roller bearings, they are about 6" long, four inches in diameter and weigh a ton!