What is a Mallet?

What is a Mallet Steam Locomotive?

By Roger Heid


Some folks are under the impression that a Mallet is a specific type engine with the wheel configuration 0-D+D-0 or 2×4/4, such as the model shown below.


Now let me try to explain what actually makes a steam engine a ‘Mallet’. The whole story started way back in 1857, when Levi Bissell, an American inventor, patented the ‘Bissell Axle’ or truck, often referred to as a ‘Pony Truck’. Essentially, this was a single axle bogie that could move vertically and laterally (sideways). Eventually, this led to the multi-axle Bissell truck, further refined by a Swiss engineer by the name of Anatole Mallet (1837-1919). He was from the French speaking part of Switzerland, therefore his name is pronounced ‘Mallay’.

According to his design, the drive wheels were subdivided into two separate groups, whereby the rear group was mounted rigid, the front group was pivoted to the loco frame right above the first axle.

In 1874, Anatole Mallet patented his system. In 1876, first ‘Mallet’ steam engine was built for use by the Biarritz and Bayonne Railroad. Others followed, mostly built by JA Maffei. Many of them were built for use on narrow gauge track systems, as well. A typical old style Swiss Mallet is pictured below.


You can clearly see now, that the number of axles employed is not the actual criterion to make a steam engine a ‘Mallet’. It is also irrelevant whether the loco is a T-type (coal box attached to the rear of the engine) or if it is dragging a separate tender car behind itself. It is the sheer principle explained above that makes a steam loco a ‘Mallet’.

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In the United States, Mallet engines did not come into existence until 1903. The first one was built for the Baltimore & Ohio Railroad. In the picture below you see it was a 0-6-6-0, and it pulled a separate tender. At first, it was ill received, but it proved itself during actual service. This resulted in a rash of other Mallet type engines to be built in the US, mostly by Baldwin. This also includes the Union Pacific Big Boy. In the UK some existing engines were converted, but they were never used by any railway. In Germany, the Gt 2×4/4 was developed for the Royal Bavarian Railroad. It was used extensively. Later on, it was re-designated as the Model BR 96, pictured below.


In my own collection, I have the Maerklin Bavarian Gt 2×4/4. It is pictured on top of this article. I just love it. In my opinion, it is one of the finest models Maerklin ever produced. From Trix, a 2-rail DC version, the Bavarian Gt 2×4/4, is available.

Of course, a lot more could be written regarding the development and history of Mallet Steam Engines, but that is not the purpose of this blog.

If you have any questions, please post them in the Forum, not in the comment section of the Blog System. Thank you.


Happy Railroading, y’all.

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