page_title: Fairlie locomotive
section_title: Single Fairlie locomotive
hierarchical_section_title: Fairlie locomotive / Single Fairlie locomotive
caption_attribution_description: Mason Bogie steam locomotive "Wm. Mason". Builder's photo from 1874.
context_page_description: A Fairlie is a type of articulated steam locomotive that has the driving wheels on bogies. The locomotive may be double-ended or single ended. Fairlies are most associated with the Ffestiniog Railway in Wales.
  While the Fairlie locomotives are used only on heritage railways, the vast majority of diesel and electric locomotives in the world today follow a form not very different from the Fairlie — two power trucks with all axles driven, and many also follow the Fairlie's double-ended concept, capable of being driven equally well in both directions.
context_section_description: A variation of the Fairlie that enjoyed some popularity, especially in the United States, was the single Fairlie, essentially half a double Fairlie, with one boiler, a cab at one end, and a single articulated power bogie combined with an unpowered bogie under the cab, maintaining the ability to negotiate sharp turns. This design abandoned the bidirectional nature of the double Fairlie but gained back the ability to have a large bunker and water tank behind the cab, and the possibility of using a trailing tender if necessary. The single conventional boiler made maintenance cheaper and did away with the crew's separation.
  The design was especially popular with William Mason, Fairlie's licensee in the United States, who built 146 or so Mason Bogie locomotives, which were a variant on this design. In the UK, a single Fairlie 0-4-4 T was used by the Swindon, Marlborough and Andover Railway and three 0-6-4 Ts by the North Wales Narrow Gauge Railways.  As well as their iconic double Fairlies, the Ffestiniog railway also has a 0-4-4 T single Fairlie loco, the power bogie of which is essentially the same as those used by their double Fairlies.
  In both the UK and the USA, single Fairlies were the first locomotives in each country to use the European Walschaerts valve gear. The Stephenson link gear, which was usual at the time, used multiple eccentrics between the frames but the Walschaerts gear was mounted outboard of the frames and connecting rods. This was advantageous because the Fairlie system required this space between the frames for the bogie pivot.
caption: Mason Bogie steam locomotive "Wm. Mason". Builder's photo from 1874
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