Rail transport modelling

Railway modelling or model railroading is a hobby in which rail transport systems are modelled at a reduced scale.
The scale models include locomotives, rolling stock, streetcars, tracks, signalling and cranes; landscapes include countryside, roads, bridges, buildings, vehicles, harbours, urban landscape, model figures and lights, with features such as rivers, hills, tunnels and canyons.
The earliest model railways were the carpet railways in the 1840s. The first documented model railway was the Railway of the Prince Imperial, built in 1859 by Emperor Napoleon III for his then three-year-old son, also Napoleon, in the grounds of the Château de Saint-Cloud in Paris. It was powered by clockwork and ran in a figure-of-eight. Electric trains appeared around the start of the 20th century, but these were crude likenesses. Model trains today are more realistic, in addition to being much more technologically advanced. Today, modellers create model railway layouts, often recreating real locations and periods throughout history.
The world's oldest working model railway is a model designed to train signalmen on the Lancashire and Yorkshire Railway. It is located in the National Railway Museum, in York, England, and dates back to 1912; it remained in use until 1995. The model was built as a training exercise by apprentices of the company's Horwich Works and supplied with rolling stock by Bassett-Lowke.

General description

Involvement ranges from possession of a train set to spending hours and large sums of money on a large and exacting model of a railroad and the scenery through which it passes, called a "layout". Hobbyists, called "railway modellers" or "model railroaders", may maintain models large enough to ride.
Modellers may collect model trains, building a landscape for the trains to pass through. They may also operate their own railroad in miniature. For some modellers, the goal of building a layout is to eventually run it as if it were a real railroad or as the real railroad did. If modellers choose to model a prototype, they may reproduce track-by-track reproductions of the real railroad in miniature, often using prototype track diagrams and historic maps.
Layouts vary from a circle or oval of track to realistic reproductions of real places modelled to scale. Probably the largest model landscape in the UK is in the Pendon Museum in Oxfordshire, UK, where an EM gauge model of the Vale of White Horse in the 1930s is under construction. The museum also houses one of the earliest scenic models – the Madder Valley layout built by John Ahern. This was built in the late 1930s to late 1950s and brought in realistic modelling, receiving coverage on both sides of the Atlantic in the magazines Model Railway News and Model Railroader. Bekonscot in Buckinghamshire is the oldest model village and includes a model railway, dating from the 1930s. The world's largest model railroad in H0 scale is the Miniatur Wunderland in Hamburg, Germany. The largest live steam layout, with of track is Train Mountain in Chiloquin, Oregon, U.S.
Operations form an important aspect of rail transport modelling with many layouts being dedicated to emulating the operational aspects of a working railway. These layouts can become extremely complex with multiple routes, movement patterns and timetabled operation. The British outline model railway of Banbury Connections in New South Wales, Australia, is one of the world's most complicated model railways.
Model railroad clubs exist where enthusiasts meet. Clubs often display models for the public. One specialist branch concentrates on larger scales and gauges, commonly using track gauges from. Models in these scales are usually hand-built and powered by live steam, or diesel-hydraulic, and the engines are often powerful enough to haul dozens of human passengers.
The Tech Model Railroad Club at MIT in the 1950s pioneered automatic control of track-switching by using telephone relays.
The oldest society is 'The Model Railway Club', near Kings Cross, London, UK. As well as building model railways, it has 5,000 books and periodicals. Similarly, 'The Historical Model Railway Society' at Butterley, near Ripley, Derbyshire specialises in historical matters and has archives available to members and non-members.

Scales and gauges

The words scale and gauge seem at first interchangeable but their meanings are different. Scale is the model's measurement as a proportion to the original, while gauge is the measurement between the rails.
The size of engines depends on the scale and can vary from tall for the largest rideable live steam scales such as 1:4, down to matchbox size for the smallest: Z-scale or T scale. A typical HO engine is tall, and long. The most popular scales are: G scale, Gauge 1, O scale, S scale, HO scale, TT scale, and N scale. HO and OO are the most popular. Popular narrow-gauge scales include Sn3, HOn3 and Nn3, which are the same in scale as S, HO and N except with a narrower spacing between the tracks.
The largest common scale is 1:8, with 1:4 sometimes used for park rides. G scale is most popular for backyard modelling. It is easier to fit a G scale model into a garden and keep scenery proportional to the trains. Gauge 1 and Gauge 3 are also popular for gardens. O, S, HO, and N scale are more often used indoors.

Scale	Ratio
T	1:450
ZZ	1:300
Z	1:220
N	1:160
2mm	1:152
TT	1:120
3mm	1:101
HO	1:87
OO	1:76.2
S	1:64
O	1:48
1	1:32
G	1:22.5

File:Model Train Track Parts.jpg|thumb|Track parts for sale at a toy store in Hutchinson, Kansas
At first, model railways were not to scale. Aided by trade associations such as the National Model Railroad Association and Normen Europäischer Modellbahnen, manufacturers and hobbyists soon arrived at de facto standards for interchangeability, such as gauge, but trains were only a rough approximation to the real thing. Official scales for the gauges were drawn up but not at first rigidly followed and not necessarily correctly proportioned for the gauge chosen. 0 gauge trains, for instance, operate on track too widely spaced in the United States as the scale is accepted as 1:48 whereas in Britain 0 gauge uses a ratio of 43.5:1 or 7 mm/1 foot and the gauge is near to correct. British OO standards operate on track significantly too narrow. The 4 mm/1 foot scale on a gauge corresponds to a track gauge of, . gauge corresponds to standard gauge in H0 3.5 mm/1 foot or 1:87.1. This arose due to British locomotives and rolling stock being smaller than those found elsewhere, leading to an increase in scale to enable H0 scale mechanisms to be used. Most commercial scales have standards that include wheel flanges that are too deep, wheel treads that are too wide, and rail tracks that are too large. In H0 scale, the rail heights are codes 100, 87, 83, 70, 55, 53, and 40 -- the height in thousandths of an inch from base to railhead.
Later, modellers became dissatisfied with inaccuracies and developed standards in which everything is correctly scaled. These are used by modellers but have not spread to mass-production because the inaccuracies and overscale properties of the commercial scales ensure reliable operation and allow for shortcuts necessary for cost control. The finescale standards include the UK's P4, and the even finer S4, which uses track dimensions scaled from the prototype. This 4 mm:1 ft modelling uses wheels or less wide running on track with a gauge of. Check-rail and wing-rail clearances are similarly accurate.
A compromise of P4 and OO is "EM" which uses a gauge of with more generous tolerances than P4 for check clearances. It gives a better appearance than OO though pointwork is not as close to reality as P4. It suits many where time and improved appearance are important. There is a small following of finescale OO which uses the same 16.5mm gauge as OO, but with the finer scale wheels and smaller clearances as used with EM- it is essentially 'EM-minus-1.7mm.'

Modules

Many groups build modules, which are sections of layouts, and can be joined together to form a larger layout, for meetings or for special occasions. For each kind of module system, there is an interface standard, so that modules made by different participants may be connected, even if they have never been connected before. Many of these module types are listed in the Layout standards organizations section of this article.

Couplers and connectors

In addition to different scales, there are also different types of couplers for connecting cars, which are not compatible with each other.
In HO, the Americans standardized on horn-hook, or X2F couplers. Horn hook couplers have largely given way to a design known as a working knuckle coupler which was popularized by the Kadee Quality Products Co., and which has subsequently been emulated by a number of other manufactures in recent years. Working knuckle couplers are a closer approximation to the "automatic" couplers used on the prototype there and elsewhere. Also in HO, the European manufacturers have standardized, but on a coupler mount, not a coupler: many varieties of coupler can be plugged in of the NEM coupler box. None of the popular couplers has any resemblance to the prototype three-link chains generally used on the continent.
For British modellers, whose most popular scale is OO, the normal coupler is a tension-lock coupler, which, again has no pretence of replicating the usual prototype three-link chain couplers. Bachmann and more recently Hornby have begun to offer models fitted with NEM coupler pockets. This theoretically enables modellers of British railways to substitute any other NEM362 coupler, though many Bachmann models place the coupler pocket at the wrong height. A fairly common alternative is to use representations of chain couplings as found on the prototype, though these require large radius curves to be used to avoid derailments.
Other scales have similar ranges of non-compatible couplers available. In all scales couplers can be exchanged, with varying degrees of difficulty.