3 ft gauge rail modelling

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For other uses of OO3, see 003 (disambiguation).

3' Gauge rail modelling is a specialisation in rail transport modelling. Specifically it relates to the modelling of narrow gauge prototypes of 3 ft (914 mm) gauge. This gauge was the most common narrow gauge in the United States and in Ireland. Apart from some other lines in North, Central and South America, 3 ft gauge was uncommon elsewhere. Therefore most 3' gauge modellers model either United States or Irish prototypes.

United States[edit]

HOn3 - Malpaso County RR by Will Booth

3 ft (914 mm) gauge railroads were widespread in the United States in the period 1880-90. While most of these railroads were converted to standard gauge by the start of the 20th Century, a number of lines survived till the Second World War and later, and became popular subjects for modelling.

Probably the most popular prototype is the Denver and Rio Grande Western Railroad, followed by other Colorado railroads such as the Rio Grande Southern and Colorado and Southern. Other railroads from California and the eastern states are also popular.

Scale and gauge combinations used in modelling include:

  • Nn3 - Using N scale (1:160 ratio) with Z (6.5 mm/​0.256 in) gauge track.
  • HOn3 - Using HO scale (1:87 ratio) with 10.5 mm (0.413 in) gauge track. Historically the most popular of the scale/gauge combinations.
  • Sn3 - Using S scale (1:64 ratio) with 14.3 mm (0.563 in) gauge track. Limited commercial support.
  • On3 - Using O scale (1:48 ratio) with 19.05 mm (0.75 in) gauge track. Probably the second most popular scale.
  • F scale - using 1:20.3 ratio with 45 mm (1.772 in) gauge track. This scale uses the same gauge as, and is derived from the popular G scale. It is the largest popular scale/gauge combination, and is suitable for use in the garden.

Perhaps not surprisingly, most narrow gauge modellers in the United States model US 3 ft gauge prototypes. However these prototypes are also popular modelling subjects outside the United States as well.

Ireland, the Isle of Man, and Britain[edit]

An OOn3 model of Donegal on the County Donegal Railway as around 1950. Layout by Alan Gee.

3 ft (914 mm) gauge was the narrow gauge used in Ireland, and the gauge of almost all the railways on the Isle of Man. It was also used on a handful of railways in Britain. However modelling these 3 ft gauge railways is very much a minority pursuit, especially when compared with other prototypes such as the Welsh 2 ft (610 mm) narrow gauge. Scales and gauges used include:

Scale (per foot) Scale ratio Name Gauge
2mm scale 1:148 Nn3 6.5 mm (0.256 in) Z scale
3mm scale 1:101 TTn3 9 mm (0.354 in) N scale
4mm scale 1:76 OOn3 12 mm (0.472 in) TT scale
5.5mm scale 1:55 5.5mm 16.5 mm (0.65 in) OO gauge
7mm scale 1:43.5 O21 21 mm (0.827 in)
15mm 1:20.3 G scale 45 mm (1.772 in)

None of these scale/gauge combinations has much commercial support, and therefore modellers are required to construct most of their models from scratch.

See also[edit]

External links[edit]