OO9

OO9
Gryndene Halt, a station on the fictitious Evaleight Light Railway, by the Sussex Downs 009 group
Scale	4 mm to 1 ft
Scale ratio	1:76
Model gauge	9 mm (0.354 in)
Prototype gauge	Narrow gauge, approx 2 ft 3 in (686 mm)

OO9 is a model railway scale and gauge combination of 4 mm scale and 9 mm (0.354 in) gauge tracks, which models a prototype track gauge of 2 ft 3 in (686 mm). It is a common choice in the United Kingdom for the modelling of narrow gauge railways whose prototype gauges lie approximately between 2 ft (610 mm) and 2 ft 6 in (762 mm). The 9 mm (0.354 in) track gauge is used by N gauge model railways, a common commercial scale, which means that a selection of wheels and mechanisms is readily available.

2 ft (610 mm) gauge railways were common in Britain, but 2 ft 6 in (762 mm) and particularly 2 ft 3 in (686 mm) were quite rare. This leads to difficulty in achieving correct scale when the gauge is widened, particularly with outside framed engines.

There is currently minimal commercially available ready to run support for OO9, although a number of manufacturers have started to announce ranges of products, and small manufacturers have made limited runs of models from time to time. The modeller is therefore generally dependent on kit manufacturers, of which there are many, adapting models made for OO, or scratch building. Many OO9 modellers also use H0e equipment. In November 2012, Peco announced the launch, during 2013, of a range of ready to run 009 coaches and wagons, based on prototypes of the Lynton and Barnstaple Railway. Although no locomotive models were announced, in the March 2013 edition of Railway Modeller Magazine, Danish manufacturer Heljan announced an 009 locomotive based on the Lynton and Barnstaple Railway Manning Wardle 2-6-2Ts. In July 2014, Bachmann announced a range of ready to run 009 products, starting with a Baldwin Class 10-12-D locomotive and a number of wagons, primarily used by the British War Department during World War I.