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O scale

O scale (or O gauge) is a scale commonly used in model railroading. Originally introduced by German toy manufacturer Märklin around 1900, by the 1930s O scale was the most common model railroad scale in the United States and remained so until the early 1960s.

O gauge had its heyday when model railroads were considered toys, with more emphasis placed on cost, durability, and the ability to be easily handled and operated by pre-adult hands than on detail and realism.

The original name for O gauge was 0 gauge or Gauge 0, because it was smaller than Gauge 1. At the time, it was believed to be impossible to make a toy train any smaller. Manufacturers such as Ives, American Flyer, and Lionel Corporation used O gauge for their budget line, marketing Wide gauge (also known as standard gauge) as their premium trains. The Great Depression wiped out demand for expensive wide gauge trains, and by 1932, O gauge was the standard, almost by default.

Because of the emphasis on toys, the scale of pre-World War II O gauge trains varied. Designers cared more about durability and making the cars look good, rather than accurate. Pre-war locomotives and cars tend to be smaller than post-war equipment.

In the United States in the 1950s, Lionel and Louis Marx and Company sold millions of O gauge toy trains, some of which are now considered collector's items. Both companies struggled in the 1960s, and by the end of the decade, HO scale had overtaken it in popularity.

Since the early 1990s, O scale manufacturers have begun placing more emphasis on realism, and the scale has experienced a resurgence in popularity, although it remains less popular than HO or N scale.

Table of contents
1 O in the United States
2 British and European O gauge
3 O in the Soviet Union

O in the United States

In the United States, O scale is defined as 1:48 (0.25 inches to the foot, "quarter scale"). This is also a common dollhouse and model car scale, which gives more options for scenery. While 1:48 is a very convenient scale for modeling using the Imperial system (a quarter-inch equals one scale foot), the discrepancy between O scale in the United States and in Europe is attributed to Lionel misreading the original Märklin specifications.

Much equipment in O scale, especially toy trains and the track, are not accurately scaled; a US variant called O27 runs on the same track but (in order to negotiate sharper curves) the locomotives and railroad cars are reduced in length, being approximately 1:64. O gauge track is not true to scale; besides being the incorrect width and possessing a third rail, its height is more than one scale foot. For this reason, O gauge track is sometimes called 'high rail'. This standard survived mostly because of the popularity of Lionel toy trains and the desire for compatibility with Lionel equipment.

However, besides the original three-rail Lionel standard using alternating current, another newer standard exists. Two-rail O scale uses the two running rails as conductors for direct current electricity. While normally the use of scale or gauge is equivalent, O gauge tends to more often mean semi-scale three-rail toy trains, while O scale carries the connotation of two-rail equipment, because of its greater "scale" accuracy, though standard two-rail trains still have an inaccurate gauge, track and wheel profiles.

Dissatisfaction with these standards led to a more accurate standard for wheels and track, called Proto:48. This duplicates to exact scale the AAR track and wheel standards.

Although Lionel is the most enduring brand of O scale trains, a variety of manufacturers made trains in this scale, and as of late 2003, no fewer than six companies market O scale locomotives and/or cars.

Possibly because of the large size of American railroad systems, accurate scale modelling in standard gauge O scale is rare in the US, though narrow gauge modelling in exact-scale On3 (1:48 scale modelling of 3 foot gauge prototypes) or On2 (2 foot gauge prototypes) is much more common.

British and European O gauge

In Britain, O gauge equipment is produced at a scale of 1:43, which is 7mm to the foot (using the common British practice of modelling in metric prototypes originally produced using Imperial measurements). It's often called 7mm scale for this reason.

Although toy trains were historically produced to this scale, few to none are still produced even for the collector market (unlike the United States). Modelling in O gauge in fact almost died out in Britain but enjoyed a resurgence in the 1990s as modellers developed a new appreciation for the level of accurate detailing possible in this scale. Few ready to run models are produced in this scale; most are available only as kits for assembly by the modeller or a professional model-builder. O gauge is considered an expensive scale to model in, although the necessarily smaller scope of a larger-scaled layout mitigates this to some extent.

A similar situation exists in Europe, although the market revolves less around kits and more around expensive handbuilt metal models for the deep-pocketed collector.

A finescale version of British 7mm O gauge exists, called ScaleSeven (S7).

O in the Soviet Union

Between 1951 and 1969, a limited number of O gauge train sets were manufactured in the Soviet Union. Utilizing the same track and voltage as their U.S. counterparts, the colorful locomotives and cars superficially resembled pre-World War II designs from Marx and Lionel, albeit with some modernization, and the couplers resembled those of post-War American Flyer.

Much like their American counterparts, Soviet O gauge trains were toys, rather than scale models.