Gauge and Scale

Symington Hoo Railway is a narrow gauge line, but what is narrow gauge.

Gauge is the distance between the two rails of the railway track.

UK mainline railways operate on standard gauge which is 4 foot 8 1/2 inches

Railways running on tracks wider than 4 ft 8 1/2 inches are known as BROAD Gauge and on tracks with a gauge less than 4 ft 8 1/2 inches are known as NARROW gauge. Common Narrow gauges are 2ft (most common in UK), 2ft 3in and 2ft 6 in.

The Leighton Buzzard Narrow Gauge Railway runs on 2 foot gauge track

www.buzzrail.co.uk 

Scale

Building a model railway requires scaling down the prototypical elements of the real thing to a suitable size to fit in the space available to store and use the model.

As children we would be given toys to play with of different scales, so our toy motor bike was bigger than our double decker bus, the houses smaller than the toy people who we imagined lived in them.

So when we want to build a model everything has to be to scale, a common / standard unit of measurement needs to be used for everything.

Modelling of mainline standard railways in the UK is known as OO, for distances, length etc. measurements are taken as 4mm = 1 ft and OO gauge has a track gauge of 16.5 mm.

As seen above British main line railways operate on a gauge of 4 ft 8 1/2 inches (4.75 ft), commercial available OO track is gauged at 16.5 mm so we are not working to true gauge, WHY ?

Well in the UK we model at 4 mm = 1 ft, so 4.75 feet at 4 mm to the foot = 19 mm not 16.5 mm so there is some compromise when dealing with commercially produced track. In other countries (including the USA) model railways are modelled in HO scale which is 3.5 mm = 1 ft, so standard gauge of 4.75 feet = 16.625 mm (taken as 16.5 mm)

                            

For Hazel Markham I am not looking to build a standard gauge railway, I want a narrow gauge railway.

However for easy and availability I want to work with 4 mm to the foot scale, this means I can get and use OO gauge houses, people, animals, trees, structures, signalling and scenery all off the shelf.

But being narrow gauge I need the track gauge to be narrower than standard OO track.

The next readily available track a size down from OO is N gauge. 

N gauge track is produced at a gauge of 9mm.

So what prototypical gauge will that give me?

We know 4mm = 1 foot, 8mm = 2 feet etc

Therefore 9mm divided by 4 = 2.25 feet or 2 feet 3 inches, which we can see from above is a more than suitable gauge for as narrow gauge railway.

So a model railway scaled to 4mm (OO gauge) running on a track gauge of 9 mm is known as OO9 

The track I will be using is from Peco and is made for OO9 modelling, the sleepers are more to scale in size and spacing, than the closely spaced tiny N gauge sleepers.