Flat spot

Flat spot

A flat spot is a fault in railroad wheel shape

Causes

A flat spot occurrs when a rail vehicle's wheelset is dragged along the rail after it has come to a standstill. Flat spots are usually caused by faulty brakes or wheelset bearings.

Consequences

If the flat spot is very small, the rail vehicle will be able to continue being used. The fault is removed later in the wheelset truing process. However, because of the heat suffered while being dragged along the rail and the impacts suffered afterward, these wheels are more likely to break due to changes in the alloy structure.

If the flat spot is very large (as in the picture), strands of molten metal may have got stuck on one side of the flat spot, making it impossible to turn the wheel due to insufficient clearing between the rolling surface and the brake pads. In this case, the wheelset must be replaced immediately.


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