HO gauge
| HO | |
|---|---|
|
|
| Scale | 3.5 mm to 1 foot |
| Scale ratio | 1:87.1 |
| Standard(s) |
NEM (Europe), NMRA (U.S.) |
| Model gauge | 16.5 mm (0.65 in) |
| Prototype gauge | Standard gauge |
HO or H0 is a scale used in model railroading. It is the most popular scale of model railway in the world.
The precise definition of HO or H0 scale varies slightly by country. According to the National Model Railroad Association (NMRA) standard S-1.2, predominantly used in North America, in HO scale 3.5 mm (0.1378 in) represents 1 real foot (304.8 mm). This is a ratio of 1:87.0857142, which is usually rounded to 1:87.1. According to the MOROP standard NEM 010, which is predominantly used in Europe, H0 scale is exactly 1:87.
In HO and H0, rails are spaced 16.5 mm (0.64961 in) apart, which approximates the standard railroad gauge of 1,435 mm (4 ft 8 1⁄2 in).
The name HO is derived from the fact that its 1:87 scale is approximately half that of O scale which was the smallest of the series of older and larger 0, 1, 2 and 3 scales introduced by Märklin around 1900. In most English-speaking markets it is pronounced "aitch-oh" and written with the letters HO today, but in German it is pronounced "hah-null", and still written with the letter H and number 0.
After the First World War there were several attempts to introduce a model railway about half the size of 0 scale that would be more suitable for smaller home layouts and cheaper to manufacture. H0 was created to meet these aims. For this new scale, a track width of 16.5 mm was designed to represent prototypical standard gauge track, and a model scale of 1:87 was chosen. By as early as 1922 the firm Bing in Nuremberg, Germany, had been marketing a "tabletop railway" for several years. This came on a raised, quasi-ballasted track with a gauge of 16.5 mm, which was described at that time either as 00 or H0. The trains initially had a clockwork drive, but from 1924 were driven electrically. Accessory manufacturers, such as Kibri, marketed buildings in the corresponding scale.
At the 1935 Leipzig Spring Fair, an electric tabletop railway, Trix Express, was displayed to a gauge described as "half nought gauge", which was then abbreviated as gauge 00 ("nought-nought"). Märklin, another German firm, followed suit with its 00 gauge railway for the 1935 Leipzig Autumn Fair. The Märklin 00 gauge track that appeared more than ten years after Bing's tabletop railway had a very similar appearance to the previous Bing track. On the Märklin version, however, the rails were fixed to the tin 'ballast' as in the prototype, whilst the Bing tracks were simply stamped into the ballast, so that track and ballast were made of single sheet of metal.
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