Types of Defects

Hot Bearing

Roller bearings fail when a bearing seizes. This leads to friction & heat that eventually can eventually cut right through the axle and lead to a derailment.



Photos

Hot Bearing
Ed Teague

Tread Build-Up

When a handbrake is left applied, material from the brake shoe can lead to tread build-up.



Photos

Tread Build-up
Foamductor (Reddit)