Ive seen terms like O-27, O-36, O-42 and O-72. What do these mean?
The numbers refer to the diameter of a circle of track. For example, a circle of O-72 track is 72 inches in diameter. Generally speaking, larger O-Scale trains require larger curves in order to look realistic. Additionally, some O-Scale trains are physically unable to run on smaller curves. For this reason, most O-Gauge trains will have a “minimum curve requirement” stated in their description which informs the buyer of the minimum curve which the item can successfully traverse. Because O-Scale trains often require a larger curve to run correctly, they require a more space to operate in. Smaller O-27 trains, as their name implies, do not require the larger curves that O-Scale trains do and can therefore operate in a much smaller area that their larger O-Scale counterparts.
