Modelling Britain's railways

(Last December 15th, 2012)

1. Scale and Gauge. 2. Drawings. 3. Terminology. 4. Gauges across the world. 5. Track compatability.

The terms scale and gauge.

In the whole vocabulary of model railways there are no two more misunderstood and often wrongly used words than "scale" and "gauge".

"Scale" relates to the ratio in size between model and prototype, expressed as some form of direct comparison. It can be expressed as a fraction (e.g. 1/76th), a ratio (e.g. 1:76) or as a statement (e.g. 4mm equals 1ft). Regardless how it is expressed, its purpose is to convey an exact dimensional relationship.

"Gauge" relates to the distance between the running rails on the track itself. There are many different gauges to be found on the world's railways but they all fall into one of three categories: broad gauge (e.g. the 7ft gauge of the early GWR); standard gauge (e.g. the current 4ft 8 1/2ins gauge of British railways); and narrow gauge (e.g. the 1ft 11 1/2ins of the Ffestiniog Railway).

Taken separately, while not exactly simple, the two terms are at least unambiguous. It is when translating it into model terms that scale and gauge sometimes become intermixed or confusing. This is largely due to a couple of things: the habit of mixing imperial and metric units with a few ratios for good measure; and the different compromises that are often made through rounding up or down otherwise awkward measurements.

The following table will help clarify the situation as well as demonstrating why the confusion arises from time to time. It shows the commonly used types of models followed by the track gauge that is normally used for models of that type when depicting standard gauge track. Following this are the two commonly used methods of describing the scale and, in brackets, the prototype track gauge that it translates into. The majority of the examples of the scale/gauge combinations shown in this table are those commonly encountered by those modeling British railways. There are also examples for those modelling European and US railways, while the overall idea will interest any modeller.

Scales and Gauges
Type Track Gauge Ratio Gauge Scale Gauge
Z 6.5mm 220:1 (4'8 1/3") 1.4mm/ft (4'7 3/4")
N (Eur) 9.0mm 160:1 (4'8 3/4") 1.9mm/ft (4'7 1/2")
N (US) 9.0mm 160:1 (4'8 3/4") 1.9mm/ft (4'7 1/2")
2mm 9.42mm 152.4:1 (4'8 1/8") 2mm/ft (4'8 1/2")
OOO 9.5mm 152:1 (4'9") 2mm/ft (4'9")
N (UK) 9.0mm 148:1 (4'4 1/2") 2.06mm/ft (4'4")
TT (Eur) 12.0mm 120:1 (4'8 3/4") 2.54mm/ft (4'8 7/10")
TT (US) 12.0mm 120:1 (4'8 3/4") 2.54mm/ft (4'8 7/10")
TT (UK) 12.0mm 101:1 (3'11 3/4") 3mm/ft (4'0")
HO 16.5mm 87:1 (4'8 1/2") 3.5mm/ft (4'8 1/2")
OO (US) 19.0mm 76:1 (4'9") 4mm/ft (4'9")
P4 18.83mm 76:1 (4'8 2/5") 4mm/ft (4'8 1/2")
EM*18.2mm 76:1 (4'6 1/2") 4mm/ft (4'6 3/5")
OO (UK) 16.5mm 76:1 (4'1 1/2") 4mm/ft (4'1 1/2")
S 0.875" 64:1 (4'8") 3/16"/ft (4'8")
O (US) 1.25" 48:1 (5'0") 1/4"/ft (5'0")
O (UK) 32.0mm 43:1 (4'6 1/5") 7mm/ft (4'7")
S7 33.0mm 43:1 (4'8") 7mm/ft (4'8 1/2")
1 45.0mm 32:1 (4'8 3/4") 10mm/ft (4'6")

*Note: The track gauge for EM was originally 18mm. However, the current standard is considered to be 18.2mm.

Several observations: first, the track gauge rarely comes out the same when using the two conversion methods, which is a demonstration of the previously mentioned compromises. Second, regardless of the conversion method, the track gauge rarely comes out to exactly 4ft8 1/2ins, though in most cases the results are very close indeed and the difference is not noticeable with the naked eye.

Finally, apparently identical types of models are not in fact identical. For example, models in N may run on the same track in the UK, Europe and North America and may be understood to be at a scale of 2mm/ft yet the ratio in the UK, which is used by the manufacturers, differs from that of Europe and North America. A second example is HO models and OO models which also both run on the same track but which are modelled to different ratios and correpondingly different scales. It helps explain why a UK model in OO and a North American model in HO have about the same loading gauge when in reality they are quite different with the North American loading gauge being considerable bigger. This is also why UK models in OO look as if they are running on narrow gauge track which they are if you look at the calculation; a scale 7ins narrow! It is this narrow gauge look of OO that led to the development of, EM and P4, which are modelled to the same ratio and scale as OO but run on track which is closer to the correctly scaled down version.

Most of the foregoing focussed on standard gauge. For completeness, reference must be made to narrow gauge and broad gauge. Typically when one models a non-standard gauge prototype railway, one can indicate it by appending a suffix to the types described in the table. However, this too is not universal and there are at least two types of such suffixes.

In the UK and in North America, the suffix is made up of a lower case "n" followed by the prototype gauge expressed in feet. Thus, an Sn3 model railway models a prototype railway with rails 3 feet apart at a 1/64 scale.

In Europe, prototype gauges are placed in 4 categories: normal gauges (1.25 to 1.70 metre); metric gauges (0.85 to 1.25 metre); narrow gauges (0.65 to 0.85 metre), and industrial gauges (0.40 to 0.65 metre). Each non-normal category has its own suffix: "m" for metric; "e" for narrow; and "i" for industrial. Thus, H0m means a model of a prototype railway with a gauge between 0.85 and 1.25 meter at a 1/87 scale.

Now, if you were confused before, try modeling Large Scale. Unlike the relative sanity of other common scales, G Scale or Large Scale is not a scale at all, but a range of different scales where the models all run on the same track (45mm gauge, the gauge for #1 also called confusingly Gauge 1) and the scales of the models are adjusted to fit. Strictly speaking using 45mm as the gauge, a 3ft narrow gauge model should be 1:20.3 scale; meter gauge models 1:22.5 and standard gauge 1:32 (but some are scaled at 1:29 instead). 1:24 scale models should represent 42ins or 3ft 6ins narrow gauge prototypes, but this scale is often used for 36ins prototypes simply because scaling at 1/2ins to the foot is easy. Unfortunately, the majority of models available are at other scales than these: LGB is primarily 1:22.5 (due to their European meter gauge heritage); Aristo is 1:29 (due to a fudge to make models of standard gauge prototypes look better when placed next to 1:22.5 scale models); and most Bachmann cars are between 1:24 and 1:22.5. And if that's not enough confusion, there are two other "garden railway" gauges: Gauge 3 (1 1/2ins or 64mm) and Gauge 0 (1 1/4ins or 32mm). Finally, if you had a tinplate railroad as a child, it may have been referred to as O27 gauge. Those trains run on track that doesn't scale out to the real thing compared to the size of the train models, many of which were shortened versions of scale. There is nothing wrong with building a layout using this equipment if you still have it, it's still a model railroad, just not a "scale" model railroad.

And you thought only computers were perverse!


Following the suggestion that a useful addition to the BRMNA web site would be an index of sources of drawings for those modelling British railways, four members were kind enough to provide the results of some indexing that they had been undertaking on their own behalf. Interestingly, the various categories suggested (locomotives, passenger stock, goods stock, trackplans, buildings and miscellaneous) closely matched the approach that they had taken. Moreover, the overlap was minimal. Following the creation of the initial version of the BRMNA index these same members plus others have provided additional material. Why not take a look? Even better, why not provide some addtional material?

In addition the following sites may be of interest:

The Great Western Archive contains a selection of Swindon Coach Drawings and provides links for GWR locomotives and GWR Goods Wagons.

The Railway Station web site is a vast database which lists every published photo of UK stations and is the work of one man!

The UK Railway Station Track Plans site is also worth a visit.


Ah, English, the universal language - or is it? Churchill said of the Americans and the British "two great nations separated by the use of a common language" though the quote is also attributed to Shaw and Wilde. So, of course, just as boot and bonnet are articles of clothing in North America, not car parts, and a lift is what short people put in their shoes to seem taller, there are different terms to describe the same thing between the UK and North America railroads, er railways (see below). In addition there are terms that have no counterpart in North America. To reduce the confusion, and perhaps increase your vocabulary, here are some terms complied by a Canadian-born, British modeller:

British termNorth American termNotes
bogiestrucksnot to be confused with the British term below
brake vancaboosenow obsolete with End of Train devices
buffersno real equivalentsome end-of-track stops have a buffer, mostly in stations
buffer beamcow catcher or pilotNot a strict translation as early North American locomotives had cow catchers for that purpose, while British railways are required to fence their right of way, ergo no strays and the loco only needed something to hold the buffers and coupler.
carriagecoach or passenger carA carriage here would be a pram there!
driverengineernot to be confused with a P. Eng.
earthgroundelectrical, not dirt in the garden
goods vanbox car
guardconductorperson not electrical
horse or cattle vancattle car
lorrytrucka road vehicle
mainscircuitsfor household current
mineral wagongondolausually steel sided
plank wagonwood sided gondola
PlastikcardStyreneBoth are trademarked names.
pointsturnoutThe prototype calls them switches but modelers use turnout to distinguish them from electrical switches.
private owner wagonprivately owned car
PVAwhite glue
railwayrailroad (US)the company - Canadian usage follows the British
railroadrailway (US)the physical plant/track etc. - Canadian usage follows the British
railway modellingmodel railroading
sheddepot/roundhouseas in engine shed.
shuntingswitchingshunting is also used mostly for small moves.
signal boxsignal tower or interlocking tower
sleeperstiesthe bits that support the rails
sleeperssleeperssleeping cars
trainspotter (anorak)railfan (railway nut)
tramstreetcarsome properties called them trams, e.g. Halifax, N.S.
trucksfreight carsTrucks in N. America are the UK's lorries or the UK's bogies
wagonsgondolas/open top RR freight carsA wagon in N.America is a child's toy or a pioneer's mode of horse-pulled transport.
Undergroundsubway as in urban tranist system.

There are more comprehensive sources of terminology web pages gleaned from our experience:

British railway and model railway Vocabulary

Wikipedia Glossary of UK railway terminology

To reduce the confusion and increase your vocabulary check this one.

Gauges across the world.

As noted in the section on the relationship between gauge and scale, gauge is the distance between the running rails of the track. There are many different examples of gauges not only across the world but also within some countries as the following examples shows:

Gauges across the world
Country Track Gauge Track Gauge
(Imperial) (Metric)
Algeria1ft 11.6in0.600m
Algeria3ft 5.25in1.050m
Algeria3ft 3.75in1.000m
Algeria4ft 8.5in1.435m
Algeria4ft 9.2in1.45m
Angola3ft 6in1.067m
Argentina2ft 5.5in0.750m
Argentina3ft 3.75in1.000m
Argentina4ft 8.5in1.435m
Argentina5ft 6in1.676m
Australia3ft 6in1.067m
Australia4ft 8.5in1.435m
Australia5ft 3in1.600m
Belgium4ft 8.5in1.435m
Bolivia3ft 3.75in1.000m
Bulgaria1ft 11.6in0.600m
Bulgaria2ft 6in0.762m
Burma3ft 3.75in1.000m
Brazil3ft 3.75in1.000m
Brazil5ft 3in1.600m
Cambodia3ft 3.75in1.000m
Canada4ft 8.5in1.435m
Ceylon2ft 6in0.762m
Ceylon5ft 6in1.676m
Chile1ft 11.6in0.600m
Chile2ft 6in0.762m
Chile3ft 6in1.067m
Chile3ft 3.75in1.000m
Chile4ft 8.5in1.435m
Chile5ft 6in1.676m
China4ft 8.5in1.435m
Colombia3ft 0in0.914m
Colombia3ft 3.75in1.000m
Congo3ft 6in1.067m
Costa Rica3ft 6in1.067m
Cuba4ft 8.5in1.435m
East Africa3ft 3.75in1.000m
Ecuador2ft 5.5in0.750m
Ecuador3ft 3.75in1.000m
Ecuador3ft 6in1.067m
El Salvador3ft 0in0.914m
Ethiopia3ft 1.4in0.950m
Ethiopia3ft 3.75in1.000m
Finland4ft 8.5in1.435m
Finland5ft 0in1.524m
France4ft 8.8in1.44m
Germany4ft 8.5in1.435m
Ghana3ft 6in1.067m
Greece3ft 3.75in1.000m
Guatemala3ft 0in0.914m
Haiti3ft 6in1.067m
Holland4ft 8.5in1.435m
Honduras3ft 6in1.067m
India2ft 0in0.610m
India2ft 6in0.762m
India3ft 3.75in1.000m
India5ft 6in1.676m
Indonesia1ft 11.6in0.600m
Indonesia3ft 6in1.067m
Italy3ft 1.4in0.950m
Italy4ft 8.5in1.435m
Iran4ft 8.5in1.435m
Iraq3ft 3.75in1.000m
Iraq4ft 8.5in1.435m
Ireland3ft 0in0.914m
Ireland5ft 3in1.600m
Jamaica4ft 8.5in1.435m
Japan3ft 6in1.067m
Japan4ft 8.5in1.435m
Jordan3ft 5.25in1.050m
Korea4ft 8.5in1.435m
Lebanon4ft 8.5in1.435m
Malawi3ft 6in1.067m
Malaysia3ft 3.75in1.000m
Mauritius4ft 8.5in1.435m
Mexico3ft 0in0.914m
Mexico4ft 8.5in1.435m
Morocco4ft 8.5in1.435m
Mozambique3ft 6in1.067m
Newfoundland3ft 6in1.067m
New Zealand3ft 6in1.067m
Nicaragua3ft 6in1.067m
Nigeria2ft 6in0.762m
Pakistan2ft 6in0.762m
Pakistan3ft 3.75in1.000m
Pakistan5ft 6in1.676m
Panama3ft 0in0.914m
Panama5ft 0in1.524m
Paraguay3ft 3.75in1.000m
Paraguay4ft 8.5in1.435m
Peru3ft 0in0.914m
Peru4ft 8.5in1.435m
Philippines3ft 6in1.067m
Portugal3ft 3.75in1.000m
Portugal4ft 8.5in1.435m
Rhodesia3ft 6in1.067m
Saudi Arabia4ft 8.5in1.435m
Sierra Leone2ft 6in0.762m
South Africa2ft 0in0.610m
South Africa3ft 6in1.067m
Spain3ft 0in0.914m
Spain3ft 3.75in1.000m
Spain5ft 6in1.676m
Sudan3ft 6in1.067m
Surinam3ft 3.75in1.000m
Sweden2ft 11in0.891m
Sweden3ft 6in1.067m
Switzerland3ft 3.75in1.000m
Switzerland4ft 8.5in1.435m
Syria3ft 5.25in1.050m
Syria4ft 8.5in1.435m
Taiwan2ft 6in0.762m
Taiwan3ft 6in1.067m
Thailand3ft 3.75in1.000m
Trinidad4ft 8.5in1.435m
Tunisia4ft 8.8in1.44m
Turkey2ft 5.5in0.750m
Turkey4ft 8.5in1.435m
UAR2ft 5.5in0.750m
UAR3ft 3.75in1.000m
UAR4ft 8.5in1.435m
United Kingdom2ft 0in0.610m
United Kingdom2ft 6in0.762m
United Kingdom3ft 0in0.914m
United Kingdom4ft 8.5in1.435m
USA4ft 8.5in1.435m
USSR5ft 0in1.524m
Venezuela2ft 0in0.610m
Vietnam3ft 3.75in1.000m
West Africa3ft 3.75in1.000m
West Africa3ft 6in1.067m
Western Australia3ft 6in1.067m
Yugoslavia2ft 6in0.762m
Yugoslavia3ft 3.75in1.000m
Zambia3ft 6in1.067m

Track Compatability.

A question that comes up time and time again realtes to track compatability between models from different manufacturers and also from the same manufacturer over time. In theory, since OO models and HO models share the same track gauge, it should be possible to run any OO equipment on any OO or HO track. However, in practice this is not necessarily true because of the different flange depth, flange width and back-to-back wheel measurements stock used by the various OO locomotive and rolling stock manufacturers and the different track height and switch dimensions used by the various manufacturers of OO and HO track.

It is certainly true that the manufacturers of ready-to-run British trains in 00 scale have used a bewildering assortment of wheel and track dimensions approximating H0 gauge, particularly prior to about 1970. If one were to produce a complete cross-reference of all the brands, with compatibility ratings, it would be a wonderful effort but I am afraid it might be a bit beyond most of us individually. However, as long ago as (I think) 1971 it was possible to say that all the major 00 RTR manufacturers bar one were using one of the two H0 gauge standards for their products. So for equipment made in the last 30 years or so, the sets of dimensions have been simplified to 3 choices: NMRA H0, NEM H0, and Hornby. Of course this ignores the specialist firms producing wheels and track in the "true" 00 gauges between 18mm (original EM) and 19mm (rare US 00), but this discussion is really not intended for people working to those finer standards.

What follows is a collection of observations based on many brands of locos and rolling stock and a few brands of track.

Locos and stock by Airfix (GMR), Palitoy Mainline, Replica, Dapol and Bachmann (U.K.) have NMRA standard (S-4) H0 wheels. (Some early wheels from Airfix and Mainline are undergauged but can be adjusted. Avoid stock having plastic wheels cast in one piece with the axle).

Locos and stock by Lima, Trix and Joueff (and British H0 rarities by Fleischmann and Marklin) have NEM standard H0 wheels, which are similar in many respects to NMRA wheels but have much deeper flanges.

NMRA wheels will operate on NMRA standard track, code 75 and up. NEM wheels will operate on NMRA standard track, code 100 only, and on NEM standard track (I assume!). NMRA standard (S-3) track includes all the popular H0 brands sold in North America for "domestic" model trains, including Atlas, AHM (Casadio) and Shinohara. The Shinohara turnouts have their clearances on the tight side of the standard and require that wheels be adjusted exactly to the standard back-to-back distance of 14.4mm, as Bachmann wheels are. Peco Streamline code 100 almost conforms to NMRA S-3 but its clearances are slack, thus the flangeway gaps around frogs are theoretically a bit too wide. However, there are several layouts where standard H0-gauge equipment runs without trouble on Peco Streamline, so perhaps the theory (of tread widths and flangeways) can be overlooked in this case.

And now Hornby. Hornby wheels and track, and even more so the ancestral Triang and Rovex, have alas never conformed to a standard. This is especially unfortunate because it has led to a perception among N.A. dealers and hobbyists that British 00 trains will not run on H0 track, and require special "British 00 track", which as we have just seen is generally not true. It cannot have been good for British exports, surely. Be that as it may, Hornby locos and stock can safely be used with Hornby track, or probably Peco Setrack which appears to be made to the same dimensions. Some recent Hornby locos can be operated on Peco Streamline, but it is really not a reliable combination. Peco plastic wheels were closer to Hornby dimensions than to the standard: they were used in kit-built stock.

Of the major departed brands, Hornby-Dublo 3-rail was naturally a thing unto itself, the gauge being 5/8 inch rather than 16.5 mm., and Hornby-Dublo 2-rail was similar. Wrenn, who continued part of the Hornby-Dublo range, used wheels of the NEM standard type.

The foregoing simplifies things in terms of standards and much of the detail has been glossed over because of lack of data. Will Lima stock (NEM) run on Fleischmann track (NEM)? Should do, but ......

A good beginning for the modeller would be to choose one of the 3 main groups for a "standard" and to acquire only stock which belongs in that group, changing the wheels on anything which is deemed "non-standard" as a result of the choice. For example, Bachmann/NMRA or Hornby/Setrack. BRMNA member-suppliers may be able to advise on the supply of replacement British wheels, e.g. Romford drivers. Peco Streamline track is quite generally available and may provide the widest degree of compatibility with the two H0 Standard groups.

More recently, Hornby have upgraded their production standards significantly, and their rolling stock is now provided with wheels which conform to NMRA S-4. Currently (2004) the producers of ready-to-run OO scale models in British outline are Bachmann, Dapol, Heljan and Hornby, and they all use NMRA standard wheels so that recently-produced models will run on standard track, both code 100 and code 75.

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