The Mallet Type Steam Locomotive

The Mallet Type (pronounced “Ma-lay”) was a unique steam locomotive design that is often mistakeningly (from a technical standpoint anyway) referred to most or all articulated steam locomotive types. The locomotive gets is name from the person who invented it, Anatole Mallet of Switzerland. The Mallet Type was essentially two engines housed under one frame and this, coupled with its six or more sets of axles, allowed it to produce awesome levels of adhesion and horsepower, which railroads, particularly in mountainous regions, found to be very beneficial over the standard heavy-hauler of the day, the Consolidation (a 2-8-0 design).

Essentially how the locomotive worked was that a rigidly mounted engine nearest the cab produced high-pressure steam that was then pumped to a forward engine which was “hinged” and free to swivel (thus an “articulated” frame) so the locomotive could much more easily negotiate curves and less-than perfectly maintained track. A very economical means of using steam the Mallet Type, coupled with both engines being roughly center mounted over each set of driving axles, was able to produce very high horsepower and adhesion with two sets of cylinders (and because of the low pressure steam in the front engine its cylinders were substantially larger than the rear cylinders).

Eventually, however, many of the “true” Mallets fell out of favor with railroads. While they were excellent at producing high horsepower and tractive effort (when production ended around 1,300 had been produced), the Mallet’s low gearing to accomplish such did not allow the locomotives to travel much faster than about 25 mph and thus, coupled with the coming of the diesel age, most were retired by the 1950s. Today, several Mallet Types of different wheel arrangements have been preserved and one is still in operation, a 2-6-6-2T design operating on the Black Hills Central Railroad based in Hills City, South Dakota. For more information about the Mallet Type please click here

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Also, consider the book American Steam Locomotives from author Brian Solomon. While this publication does not include quite as much technical data as Parker's book, How a Steam Locomotive Works, it is still a very good resource with lots of information and best of all, is loaded with photographs! If you're interested in perhaps purchasing either (or both) of these books please visit the links below which will take you to ordering information through Amazon.com, the trusted online shopping network.

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