Hispanopedia WikiEM gauge (named after the track gauge of a nominal Eighteen Millimetres[1]) is a variant of 4 mm to a foot (1:76) scale used in model railways.
EM was developed because OO gauge, favoured by manufacturers of British prototype models, utilised track that was too narrow. OO was developed in the UK in the 1930s as a response to manufacturers finding they were unable to fit the motors of the time into British prototype small boilered locomotives when scaled at the globally popular HO scale's 3.5 mm to a foot (1:87). As the scale was increased to 4 mm to the foot to make the locomotives larger, the track gauge was left at 16.5 mm (0.65 in), and hence is too narrow (by a scale 178 mm or 7 in) to correctly depict the prototype's track gauge of 4 ft 8+1⁄2 in (1,435 mm).
EM gauge was founded in the 1950s, originally with 18 mm (0.709 in) gauge track and rolling stock wheelsets based upon the crude and massively out-of-scale products of the contemporary OO model manufacturers.
18 mm gauge was still undersize by almost a millimetre. With the limitations of modelling at this time, particularly the width of tyres, the largest gauge that could fit within the outline of a scale model would be 18.5 mm, no larger.[2] This was mostly an issue for steam locomotives, where the popular technique at the time of making connecting and coupling rods from rail required an excessive spacing between wheel faces and the cylinders.[2]
Attempts to make finer tyre and flange standards were thwarted initially by the overscale rail sections available commercially, it being impractical for an individual modeller to make smaller rails – although some did attempt to, by cutting down commercial rail. Smaller flange and tyre dimensions were also unsuccessful, as the narrow tyres tended to detach from the wheel centres.[2] More critically, small flanges required comparably smaller rail, trackwork gaps and point frogs in order to work reliably.
Con el tiempo, los estándares de los juegos de ruedas se volvieron más precisos, lo que permitió que EM evolucionara a una vía de 18,2 mm ( 0,717 pulgadas ) de ancho (durante un tiempo llamada vía EEM hasta que se adoptó como estándar principal). Algunos modelistas aún no estaban satisfechos con esto, ya que seguía siendo 1,9 pulgadas (48,26 mm) demasiado estrecha, y desarrollaron los estándares P4 ( 18,83 mm o 0,741 pulgadas de ancho).
La mayoría de los modelistas de EM habrán comenzado con la escala OO y, tras adquirir las habilidades necesarias, habrán pasado a EM. Los modelistas de EM suelen cambiar las ruedas de sus vagones y construir las vías a mano, aunque también hay vías prefabricadas disponibles en proveedores especializados. Existen además numerosos kits a escala de 4 mm que pueden utilizarse con todas las escalas de 4 mm, y, dado el nivel de habilidad requerido, la construcción de kits avanzados y la creación de maquetas desde cero también son prácticas comunes.
Las normas EM las establece la EM Gauge Society, que define las dimensiones del calibre y de las ruedas para garantizar la compatibilidad entre los diferentes diseños.
Véase también
Referencias
Enlaces externos
- Sociedad de medidores electromagnéticos
- Escala de 4 mm