OO9

OO9 is a model railway scale/gauge combination of 4 mm scale and 9 mm gauge tracks, which would be accurately to scale for a prototype (real life) 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 (600 mm) and 2ft 6 in (760 mm). A 9 mm 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.

Using N gauge 9 mm track to model narrow gauge prototypes is also popular in HO scale model railways. In Europe, this is known as HOe while in the United States this is called HOn30 or HOn2½. As the latter indicates, 9 mm in HO scale is 783 mm in the prototype, closer to 30 in or 2.5 ft.

<stub>

External links

• OO9 society