H0n30

HOn30
Chivers Finelines Forney 2-4-4, built by Peter Bartlett
Scale	3.5 mm to 1 foot
Scale ratio	1:87
Model gauge	9 mm (0.354 in)
Prototype gauge	2 ft (610 mm) (narrow gauge)

H0e
Egger-Bahn Steam Tram
Scale	3.5 mm to 1 foot
Scale ratio	1:87
Model gauge	9 mm (0.354 in)
Prototype gauge	760 mm (2 ft 5 15⁄16 in) (Narrow gauge)

HOn30 (also called HOn2½, HO9 and H0e) gauge is the modelling of narrow-gauge railways in HO on N (9 mm/​0.354 in) gauge track in 1:87 scale ratio.

The term HOn30 (and sometimes HOn2½) is generally used when modelling American prototypes while H0e is used for European prototypes. In the Britain the term OO9 is sometimes used. All these terms refer to models of narrow-gauge railways built to the world's most popular model railway scale of HO (1:87) but using a track gauge of 9 mm (0.354 in)—the gauge used for N scale models of standard-gauge railways. OO9 refers to OO scale, 1:76.2, models on 9mm gauge track. Although the track gauge is 9mm, sometimes N scale track per se is not used because the ties or sleepers are out of scale and too close together. HOn30 track is available.

HOn30 is often used to model the 2 ft (610 mm) gauge railroads in the US state of Maine. The first HOn30 / HOn2½ RTR brand introduced in the US was the AHM MinitrainS, initially manufactured by Egger-Bahn and later by Roco and Mehanoteknika Izola, also known as Mehano.

Perhaps the most fascinating part of HOn30 is that RTR models are still scarce. One exception is The MinitrainS line that has recently been upgraded.

H0e is a gauge defined by Normen Europäischer Modelleisenbahnen (NEM). According to that standard, H0e represents narrow gauges between 650–850 mm (25.59–33.46 in), though it's often used to represent 600 mm (1 ft 11 ⁵⁄₈ in) gauge railways as well. In strict scale H0e represents a theoretical gauge of 783 mm (2 ft 6 ¹³⁄₁₆ in), which does not exist as a prototype. But this is very close to the gauge of the 750 mm (2 ft 5 ¹⁄₂ in) gauge railways most widely used in Germany, 760 mm (2 ft 5 ¹⁵⁄₁₆ in) gauge railways Bosnian gauge most widely used in the former Austro-Hungarian empire, 800 mm (2 ft 7 ¹⁄₂ in) gauge rack railways in Switzerland as well as to the 2 ft 6 in (762 mm) gauge used in parts of the British Empire.