What track gauge and standards are used?
Triang adopted the international TT standard gauge of 12mm but a scale of 3mm/ft (1:101.6) rather than the smaller TT scale of 1:120; this was to accommodate the rather cramped clearances of British prototypes. Although 12mm gauge is undersized for 3mm/ft it is widely used for finescale layouts as well as those based on Triang. The Society publishes three alternative standards to be used with 12 mm gauge based on the type of wheels to be used. The standards are Coarse (Triang), Intermediate (originally based on wheels such as Sharman and Maygib), and Fine (compatible with the Society's own finescale wheels). In practice most modellers choosing 12mm gauge use Intermediate standards and now benefit from a new, comprehensive range of Intermediate standard wheels introduced by the Society; these are known as SQ wheels since the steam locomotive driving wheels fit on square-ended axles, similar to the Romford wheels of old, to aid quartering.
An alternative to 12mm gauge is the prototypically correct 14.2mm gauge, using Society Fine standards. This has long been used by a number of Society members, aided by the very wide selection of Finescale wheels produced by the Society. A recently developed service has been the conversion of round-holed locomotive driving wheels to square-holed, similar to the SQ wheels, to provide the same advantages of automatic quartering.
A gauge of 13.5mm has also been around for a long time, a sort of 3mm equivalent of the 4mm EM, and has a currently small number of users. It has advantages for certain prototypes where the clearances in 14.2mm gauge are a bit tight. Both Intermediate and Fine standards are available, and the corresponding wheels..
The gauges discussed above are, of course, related to the "standard" prototype gauge of 4' 8.5". However a number of other prototype gauges are also modelled. Thus 9mm is used to represent 3' gauge, 15.75mm to represent Irish 5' 3" gauge, 16.5mm to represent 5' 6" gauge and 21mm to represent Brunel's 7' gauge.