Mallet (locomotive)

A Mallet locomotive is a type of articulated locomotive. A Mallet locomotive has a long boiler and double propulsion units - the rear unit is directly attached to the main body of the locomotive, while the front unit is mounted on a bogie coupled to the front of the boiler, the end of which overhangs on tight curves.

In Whyte notation Mallet locomotives are expressed using a 4-part notation.

The most famous Mallet locomotive is the Union Pacific Big Boy, which had a 4-8-8-4 wheel arrangement.