This article assumes that you are already familiar with model railroad scales and gauges.
Narrow Gauge RailroadsA "narrow gauge" is defined as any railroad with the rails of its tracks spaced closer together than 4ft. 8.5 inches (standard gauge). Around the world there have been many real-life narrow gauge railroads, using many different rail spacings.
In the early years of railroading in the United States it was common to find narrow gauge railroads that used track spaced at 3 feet (1 yard). Some narrow gauge railroads still exist in America today. These include the White Pass and Yukon Route and the Disneyland Railroad. In Great Britan, and other parts of the world, a common narrow gauge was 30 inches (2 feet 6 inches). Another popular gauge in Europe is "meter gauge", where the rails are spaced 1 meter apart.
Narrow Gauge ModelingTrue-to-scale narrow gauge modeling is a very specialized area of model railroading. Many manufacturers produce models of narrow gauge trains with wheelbases out-of-scale to run on standard gauge track. But there are modeling standards for both 30 inch and 3%nbsp;foot gauge trains.
Narrow gauge products are denoted by the small letter "n" following the scale designation, which is then followed by "30" for 30 inch gauge or "3" for 3 foot gauge. For example, On3 is 3 foot narrow gauge in O scale (1:48) and On30 is 30 inch narrow gauge in O scale.
F/Fn3 Scale - 1:20.3Gauge: 1.75” (45mm)
Sometimes referred to as F scale, Fn3 accurately models North American 3 foot gauge railroad trains using the same 45mm track used by G scale for modeling standard gauge. Like G scale, Fn3 is primarily an outdoor scale.
On3 Scale - 1:48Gauge: 0.75” (19.05mm)
On3 requires its own specially gauged track, which is often hand-made. Although On3 is more true-to-scale, than its On30 competitor it popularity has suffered since the introduction of On30. On30's wheelbase is slightly out-of-scale, but it enjoys broader appeal because it runs on readily available HO gauge track.
On30 Scale - 1:48thGauge: 0.649” (16.5mm)
This scale uses HO track for modeling narrow gauge railroad trains built in O scale.
HOm Scale: 1/87.1Gauge: 0.413” (12mm)
HOm uses TT scale track to model meter gauge trains and trams in HO scale. This variant of HO is popular for modeling Swiss meter gauge prototypes.
HOn3 Scale: 1/87.1Gauge: 0.413” (10.5mm)
Modeling American 3 foot gauge, HOn3 is the most popular variant of HO in the US; it might also be the most popular narrow gauge modeling scale. HOn3 requires its own specially made track, because its gauge isn't close enough to standard gauge in any of the smaller scales for track compatibility.
HOn30 / HOn2 1/2 /HOe - 1:87.1Gauge: 0.413” (9mm)
Models 30 inch gauge railroad trains on N scale track.
TTn3 Scale - 1/120thGauge: 0.353” (8.97mm)
TTn3 models TT scale narrow gauge trains on N scale track. Though standards have been set by the NMRA, both TTn3 and standard gauge TT scale remain a exotic scales in areas outside of Eastern Europe.
Nn3 Scale - 1/160thGauge: 0.257” (6.52mm)
Nn3 models narrow gauge N scale trains on Z scale track.