2-2-2

Under the Whyte notation for the classification of steam locomotives, 2-2-2 represents the wheel arrangement of two leading wheels on one axle, two powered driving wheels on one axle, and two trailing wheels on one axle. The wheel arrangement both provided more stability and enabled a larger firebox than the earlier 0-2-2 and 2-2-0 types. This configuration was introduced in 1834 on Robert Stephenson's 'Patentee locomotive' but it was later popularly named Jenny Lind, after the Jenny Lind locomotive which in turn was named after the popular singer. They were also sometimes described as Singles, although this name could be used to describe any kind of locomotive with a single pair of driving wheels.

Other equivalent classifications are:

The 2-2-2 configuration appears to have been developed by Robert Stephenson and Company in 1834, as an enlargement of their 2-2-0 Planet configuration, offering more stability and a larger firebox. The new type became known as Stephenson's Patentee locomotive.Adler, the first successful locomotive to operate in Germany, was a Patentee supplied by Robert Stephenson and company in component form in December, 1835 was one of the earliest examples. Other examples were exported to the Netherlands, Russia and Italy. By 1838 the 2-2-2 had become the standard passenger design by Robert Stephenson and Company.

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