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Scale and Gauge











Any conversation about model railways will use the words 'scale' and 'gauge'. These terms are fundamental to our hobby, but their use can sometimes be slightly confusing.

Let's start with scale. An easy definition is it describes the relative size of a representation of an object (whether as a model or a drawing) to the object itself. This can be shown as either a ratio or a fraction. For instance, full-size is 1:1 or 1/1, half-size is 1:2 or 1/2 and quarter-size is 1:4 or 1/4.

In the context of railways, gauge is the distance between the two rails of the track. Most full-size railways in the world are 4 feet 8 1/2 inches gauge. This dates back to the pioneering work of George Stephenson and is usually called 'Standard Gauge'. Some railways are wider than this, Spain, Russia and Ireland are examples of countries with broader gauge railways. Some railways are narrower than Standard Gauge, normally ranging from just under 2 feet gauge to 3 feet 6 inches gauge. These are called Narrow Gauge railways and were popular in certain circumstances because they tended to be much cheaper to build than Standard Gauge railways.

Thus far all is fairly straightforward. But, the world of model railways brings its own interesting dimension to the discussion.  This is because the term 'gauge' also applies to the distance between the rails of the track on a model railway. Imagine a person building a 1:4 scale model of a Standard Gauge railway. They would use a track gauge of just over 1 foot 2 inches. Another person decides to build a 1:2 scale model of a 2 feet 4 inch gauge Narrow Gauge railway.  They would use a track gauge of 1 foot 2 inches. Two model railways using pretty much the same track gauge, but built to very different scales! This combination of scale and gauge is all part of the fun of model railways and, sometimes, the simple terms 'scale' and 'gauge' can have a wider meaning.

From the early days of model railways in the Nineteenth Century, Standard Gauge railways were the normal choice for models and a shorthand developed, which used only the term 'gauge'. Scale was implied because it was intended the model represented a Standard Gauge railway. The common gauges were:

Gauge 3 - 2 1/2 inch gauge;

Gauge 2 - 2 inch gauge;

Gauge 1 - 1 3/4 inch gauge and

Gauge 0 - 1 1/4 inch gauge.

Incidentally, please note Gauge 0 was, and still is, normally pronounced as 'Gauge O', the letter 'O' being used instead of 'naught' or 'zero'.

Over the years there has been a tendency to use metric near equivalents for these gauges instead of inches.

During the early-to-mid Twentieth Century there was a desire to make smaller-sized models and Gauge 'H0', for 'Half-0', appeared in the 1920s. Gauge 'H0' uses 16.5mm gauge track. This gave a problem in Great Britain because the trains here tend to be smaller (a legacy of the country's early development of railways) and a solution was found - retain the 16.5mm gauge track but build the models to a larger scale. Gauge 'H0' is 1:87 scale and Gauge '00', for 'Double-0', uses the larger 1:76 scale. These are normally said as 'HO Gauge' and 'Double O Gauge' - once again the letter 'O' being pronounced rather than the correct 'naught' or 'zero'.

After the Second World War, just as 'H0' and '00' were establishing themselves as the dominant model railway gauges; '00' for Great Britain and Ireland, and 'H0' for the rest of the world, there was a desire for further miniaturisation.

'TT', for 'Table-Top' gauge, arrived using a 12mm gauge track. For the same reasons as 'H0' and '00', Great Britain used a scale of 1:100 and the rest of the world used the smaller and more accurate scale of 1:120.

Finally, for our present purposes, a smaller gauge of 9mm appeared. This was, at first called '000' Gauge in Great Britain and 'N' Gauge elsewhere. The designation 'N' was chosen by the German Arnold company, which was a pioneer manufacturer of 'N' gauge products, because the word for the figure '9' commences with the letter 'N' in most European languages. After a few years, 'N' Gauge became the accepted term in Great Britain as well. The scales used for 'N' settled down at 1:148 for Great Britain and 1:160 for most of the rest of the world.

Most of the model railways featured on this website are British 'N' gauge - 1:148 scale trains running on 9mm gauge track.

Interestingly or unfortunately, according to one's point of view, British model railway enthusiasts have developed a tendency to often refer to scale in a different way. And we make a bit of a muddle of it because we mix Imperial and metric measurements! '00' Gauge, mentioned earlier, is often described as 4mm to the foot or 4mm/foot. 'N' Gauge is often called 2mm/foot. As British 'N' Gauge uses a very slightly larger scale, it is actually 2.062mm/foot. But the majority of British modellers are content to call it 2mm/foot!

z 20211118 Two B12 front view.JPG
z 20211118 Two B12s for Website.JPG

This picture shows three very similar standard gauge goods wagons, modelled to different scales.  The NE one is British ‘N’ Gauge, the GW wagon is ‘00’ Gauge and the LMS one is Gauge ‘0’.  This gives a general idea of the effect of a chosen scale on the size of a model.

This picture and the one at the top of the page show two steam locomotives of the same type.  The big one is ‘00’ Gauge, running on 16.5mm gauge track, and small one is British N’ gauge, running on 9 mm gauge track.  ‘N’ Gauge is almost exactly half of ‘00’ as regards linear dimensions.  This means it requires only a quarter of the area of ‘00’ Gauge.  This is important when considering building a layout in the house.  A ‘N’ Gauge layout which requires six square feet will occupy 24 square feet in ‘00’ Gauge.  

z 20211121 Wagons for website_edited.jpg
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