5.5mm scale

5.5mm
A scene from Francis Stapleton's 5.5mm layout, Ty Bach
Scale per foot:	5.5mm to 1ft
Scale ratio:	1:55
Gauge:	16.5 mm (0.650 in), 12 mm (0.472 in)
Prototype Gauge:	3 ft  (914 mm), 2 ft  (610 mm)-2 ft 3 in (686 mm)

5.5mm scale is used for modelling narrow gauge railways. 12 mm (0.472 in) gauge track is used to represent 2 ft  (610 mm) to 2 ft 3 in (686 mm) gauge prototypes. 16.5 mm (0.650 in) gauge track is used to represent 3 ft  (914 mm) gauge prototypes.

History

5.5mm scale narrow gauge model railways were developed by GEM in 1963, using 12 mm (0.472 in) gauge track, which was the smallest commercially available gauge at the time (TT gauge). GEM produced kits for locomotives and rolling stock from the Ffestiniog and Talyllyn railways. Following the development of N gauge, using 9 mm (0.354 in) gauge track, the popularity of 5.5mm scale declined as modellers adopted OO9 which could combine N gauge track and mechanisms with the widely supported 4mm scale.

However 5.5mm scale remained in use and, following an article on the Gwynant Valley Railway by Malcolm Savage in Railway Modeller, October 1984, the 5.5mm Association was formed. The tooling for the GEM kits was purchased by Malcolm Savage in 1996 and he is now producing and upgrading those kits. Worsley Works has also produced "scratch aids" for the scale.