Mallet locomotive

Diagram of Mallet articulation (red line) system

A 2-10-10-2 Mallet locomotive in Winslow, Arizona, in 1913–14

A Mallet locomotive is a type of compound articulated steam locomotive, invented by the Swiss engineer Anatole Mallet (1837–1919).

The front of the locomotive is articulated on a bogie. The compound steam system fed steam at boiler pressure to high-pressure cylinders driving the rear set of driving wheels (rigidly connected to the boiler). The exhaust steam from these cylinders was fed into a low-pressure receiver and was then sent to low-pressure cylinders that powered the driving wheels on the swiveling bogie towards the front of locomotive.