On30 gauge

On30 (also called On2¹⁄₂, O16.5 and Oe) gauge is the modelling of narrow gauge railways in O scale on HO (16.5 mm/​0.65 in) gauge track in 1:48 scale ratio by American model railroaders, in 1:43.5 scale ratio by British and French model railroaders and 1:45 by Continental European model railroaders (excluding France).

Definitions

On30

On30 uses the American O scale of 1/4" to the foot, (ratio 1:48) to operate trains on HO gauge (16.5 mm/​0.65 in) track. The 30 indicates the scale/gauge combination is used to model 2 ft 6 in (762 mm) narrow gauge prototypes, although it is often used to model 2 ft (610 mm) and 3 ft (914 mm) gauge prototypes as well. This scale/gauge combination is sometimes referred to as On2¹⁄₂.

O16.5

O16.5 in the United Kingdom is a model railway scale/gauge combination of 7 mm to the foot. This is the same scale as British O scale (1:43.5 ratio) running on 16.5 mm (0.65 in) gauge track, which is used by HO/OO gauge model railways. It thus represents the prototype gauge of just over 2 ft 6 in (762 mm), although also widely used to model 2 ft (610 mm), 2 ft 3 in (686 mm) and 2 ft 4 in (711 mm) gauge UK prototypes.