My friend sent me the video link, which displayed the coach derailed is easily rerailing through a rock simply.

https://youtube.com/shorts/IQCZTQLH7b4?si=64OpujDkP4mXCMy2

I was inspired by the video and decided to experiment this circumstance.

I cut down a piece of eraser as the rock and put it into the rail, then made the coach run over the "rock". Initially, I failed to get the effect like video.

I try to cut different angles of eraser for the experiment and eventually, I did it ! Very interesting, you may try to experience this.

My comment is only the applied angle of rock can achieve it.

Following is the movie I made.