Editing OO gauge (section)

==Origin==
'''Double-0''' scale model railways were launched by [[Bing (company)|Bing]] in 1921 as "The Table Railway", running on {{RailGauge|16.5 mm}} track and scaled at 4&nbsp;mm-to-the-foot. In 1922, the first models of British prototypes appeared. Initially all locomotives were powered by clockwork, but the first electric power appeared in autumn 1923.
[[Image:OO Flying Scotsman.jpg|thumb|right|[[Hornby Railways]] [[Flying Scotsman locomotive|''Flying Scotsman'' locomotive]] on an OO gauge layout]]

OO describes models with a scale of 4&nbsp;mm = 1 foot (1:76) running on HO scale 1:87 (3.5&nbsp;mm = 1 foot) track (16.5&nbsp;mm/0.650 in).<ref>{{Cite web |title=Standards |url=https://doubleogauge.com/standards/ |access-date=2022-03-31 |website=The Double O Gauge Association |language=en-GB}}</ref> This combination came about as early clockwork mechanisms and electric motors were difficult to fit within HO scale models of British trains, which are smaller than their European and North American counterparts. A quick and cheap solution was to enlarge the scale of the model to 4&nbsp;mm-to-the-foot but keep the 3.5&nbsp;mm-to-the-foot gauge track. This also allowed more space to model the external valve gear. The resulting HO track gauge of 16.5&nbsp;mm represents 4 feet 1.5 inches at 4&nbsp;mm-to-the-foot scale; this is 7 inches under scale, or approximately 2.33&nbsp;mm too narrow.

In 1932, the Bing company collapsed, but the Table Railway continued to be manufactured by the new [[Trix (company)|Trix]] company. Trix decided to use the new HO standard, being half of French 0 gauge (1:43.5 scale).<!-- "European" 0 gauge is 1:45 scale! -->

In 1938, the [[Meccano Ltd|Meccano]] Company launched a new range of OO models under the trade name of [[Hornby Dublo]]. The combination of 4&nbsp;mm scale and 16.5&nbsp;mm gauge has remained the UK's most popular scale and gauge ever since.

In the United States, [[Lionel Corporation]] introduced a range of OO models in 1938. Soon other companies followed but it did not prove popular and remained on the market only until 1942, when Lionel train production was shut down due to wartime restrictions to the use of steel. OO gauge was quickly eclipsed by the better-proportioned HO scale. The Lionel range of OO used 19&nbsp;mm ({{frac|3|4}} inch) track gauge, equating to 57&nbsp;inches or 4&nbsp;ft 9&nbsp;in – very close to the 4&nbsp;ft 8{{frac|1|2}}&nbsp;in of standard gauge. There is a small following of American OO scale today.{{citation needed|date=May 2025}}