What can create flat spots on train wheels?

Flat spots on train wheels typically occur when the hand brakes are applied while the train is in motion or when the train comes to a sudden stop. When the hand brakes are engaged, they can cause the wheels to lock up, preventing them from rotating freely. This friction between the wheel and rail can lead to a flat spot, where a portion of the wheel's surface becomes flattened instead of maintaining its rounded shape.

This issue is particularly prevalent in cases where the brakes are over-applied or improperly used, leading to uneven wear on the wheels. When such flat spots develop, they can create a noticeable thumping noise while the train is in motion and can require wheel maintenance or replacement to ensure safe and smooth operation.

In contrast, excessive speed, improper loading, and certain weather conditions do not directly cause flat spots on wheels in the same immediate manner as improper application of hand brakes. While those factors can affect train performance and safety, the specific action of applying hand brakes incorrectly is the most direct cause of flat spots.