Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, six powered and coupled driving wheels on three axles and no trailing wheels. This arrangement is commonly called a Mogul. Overview In the United States and Europe, the wheel arrangement was principally used on tender locomotives. This type of locomotive was widely built in the United States from the early 1860s to the 1920s. Although examples were built as early as 1852–53 by two Philadelphia manufacturers, Baldwin Locomotive Works and Norris Locomotive Works, these first examples had their leading axles mounted directly and rigidly on the frame of the locomotive rather than on a separate truck or bogie. On these early 2-6-0 locomotives, the leading axle was merely used to distribute the weight of the locomotive over a larger number of wheels. It was therefore essentially an 0-8-0 with an unpowered leading axle and the leading wheels did not serve the same purpose as, for example, the leading trucks of the American or Ten-Wheeler types which, at the time, had been in use for at least a decade. The first American 2-6-0 with a rigidly mounted leading axle was the Pawnee, built for heavy freight service on the Philadelphia & Reading Rail Road. In total, about thirty locomotives of this type were built for various American railroads. While they were generally successful in slow, heavy freight service, the railroads that used these first 2-6-0 locomotives didn't see any great advantages in them over the or designs of the time. The railroads noted their increased pulling power, but also found that their rather rigid suspension made them more prone to derailments than the locomotives of the day. Many railroad mechanics attributed these derailments to having too little weight on the leading truck. The first true 2-6-0s were built in the early 1860s, the first few being built in 1860 for the Louisville & Nashville Railroad. The new design required the utilisation of a single-axle swivelling truck. Such a truck was first patented in the United Kingdom by Levi Bissell in May 1857. In 1864, William S. Hudson, then the superintendent of Rogers Locomotive & Machine Works, patented an equalized leading truck that was able to move independently of the driving axles. This equalized suspension worked much better over the uneven tracks of the day. The