Standard gauge

Rail gauge
Broad gauge
Standard gauge
Scotch gauge
Narrow gauge
Dual gauge
Break-of-gauge
Rail tracks
Tramway track
List of Rail Gauges

As railways developed and expanded one of the key issues to be decided was that of the rail gauge (the distance, or width, between the inner sides of the rails) that should be used. The eventual result was the adoption throughout a large part of the world of a standard gauge of 1,435 mm (4 ft 8½ in), allowing inter-connectivity and the inter-operability of trains. Currently 60% of the world's railway lines are built to this gauge. It is also named Stephenson gauge after George Stephenson.

In England some early lines in colliery areas in the north east of the country were built to a gauge of 4 ft 8 in; and in Scotland some early lines were 4 ft 6 in (1371 mm) (Scotch gauge). By 1846, in both countries, these lines were widened to standard gauge. Parts of the United States rail system, mainly in the northeast, adopted the same gauge because some early trains were purchased from Britain. However, until well into the second half of the 19th century Britain and the USA had several different track gauges. The American gauges slowly converged as the advantages of equipment interchange became more and more apparent; the destruction of much of the South's 5ft broad gauge system in the American Civil War hastened this trend.

Origin

The English railway pioneer George Stephenson spent much of his early engineering career working for the coal mines of County Durham. The Stockton and Darlington Railway (S&DR), the world's first steam-powered railway, was built primarily to transport coal from several mines near Shildon to the port at Stockton-on-Tees. The S&DR's track gauge of 4 ft 8 in was set to accommodate the existing gauge of hundreds of horse-drawn chaldron wagons that were already in use on the wagonways in the mines. Stephenson used the same gauge (with an extra half-inch of slack) for the Liverpool and Manchester Railway opened five years later. The success of this led to Stephenson (and his son Robert) being employed to engineer several other larger railway projects. This influence appears to be the main reason that this particular gauge became the standard, and its usage became more widespread than any other gauge.

Subsequently, engineers have shown that a narrow gauge is less than ideal: despite usually offering cheaper construction, a smaller gauge restricts speeds due to a reduced load stability. Broader gauges are theoretically more stable at speed and allow larger, wider, heavier loads. According to Isambard Kingdom Brunel's studies the optimum gauge for a rail system (and the one he originally used on his Great Western Railway) is 7ft.

In the United Kingdom, a Royal Commission in 1845 reported in favour of a standard gauge. In Great Britain, Stephenson's gauge was chosen as the standard gauge on the grounds that lines built to this gauge were eight times longer than that of the rival 7ft gauge, adopted principally by the Great Western Railway. The subsequent Gauge Act of 1846 ruled that new passenger-carrying railways in Great Britain should be built to a standard gauge of 4 ft 8½ in (1435 mm); and those in Ireland to a standard gauge 5ft 3in. It allowed the broad gauge companies in Great Britain to continue repair their tracks and to expanded their networks within the Limits of Deviation and the exceptions defined in the Act. After an intervening period of mixed-gauge operation (tracks were laid with three running-rails), the Great Western Railway finally converted its entire network to standard gauge in 1892.

A popular legend traces the origin of the 4 ft 8½ in (1435 mm) gauge even further back than the coalfields of northern England, pointing to the evidence of rutted roads marked by chariot wheels dating from the Roman Empire. This legend may have some truth, as there is a historical tendency to place the wheels of horse-drawn vehicles approximately 5ft apart, which probably derives simply from the width needed to fit a carthorse in between the shafts.

See also

• Rail gauge

Ideal gauge

There has been much controversy about what constitutes the "ideal gauge". From a design point of view, a train can travel faster around a given radius of track if the gauge is wider, as the centre of gravity of the train is therefore further displaced from the wheels, which in turn lowers the angle between the wheel's lower contact surface to the centre of gravity, and horizontal. Given that one can tailor either the track radius for train speed, or the train speed for track radius, gauge in some cases may not be as important as interoperability.

There are many examples of high speed and high mass applications on narrow gauges throughout the world, suggesting that gauge is less important than the original supporters of either broad gauge or narrower gauges held it to be:

• The heaviest trains in the world run on standard gauge track in Australia, North America and Mauritania. Gauge is not the limiting factor in running heavier trains.
• The fastest conventional trains in the world also run on standard gauge in Japan and Europe, where speeds over 300 km/h are attained. (Gauge is irrelevant for levitating maglev trains.)
• Very heavy trains run on the narrow gauge of 3 ft 6 in (1067 mm) in Queensland (Australia) and South Africa, on track as strong as heavy standard gauge track. A narrow gauge does not seem to materially affect the weight of trains that can be run.
• Fairly fast trains (160 km/h) can run on narrow gauge track, as can be seen in Japan and Queensland.
• It is possible to build a light standard gauge line about as cheaply as a narrow gauge line.
• It is possible to build a narrow gauge line to as heavy-duty a standard as a standard gauge line.
• Loading gauge, structure gauge, axle load, compatibility of couplings, continuous brake, electrification systems, railway signal systems, radio systems and rules and regulations are also important.

With the benefit of hindsight, little was gained by building railway systems too narrow (down to about 3 ft (900 mm)) or too broad (up to about 7 ft (2100 mm)) gauges, and this was at the cost of limited interoperability. For an example of the difficulties of interoperability see the Ramsey Car Transfer Apparatus and the Variable gauge axles used to transfer cars between different gauges of track.

Only in gauges of less than 3 ft (914 mm) can a railway be built significantly more cheaply than is possible with standard gauge, and only then in mountainous terrain, or where a low capacity line is required, or with industrial railways where through running is not required.

It can be argued therefore, that the original uniform gauge adopted by Stephenson in 1830 can serve most of the tasks performed by gauges from 3 to 7 ft (900 to 2100 mm), albeit with a mini gauge of about 2 ft (600 mm) for cane tramways, underground mine, mountain, construction, temporary and military railways, plus children's railways.

Piggyback operation

For interoperability, if possible, the mini-gauge trams should be able to piggyback on top of standard gauge flat wagons, to reach workshops and other narrow gauge lines to which they are not otherwise connected. Piggyback operation by the trainload occurred as a temporary measure between Port Augusta and Marree during gauge conversion works in the 1950s, to bypass steep gradients in the Flinders Ranges. Piggyback operation was a permanent feature of the Padarn Railway in North Wales.

It is also possible for standard gauge vehicles to operate over narrow gauge tracks using adaptor vehicles; the Rollbocke transporter wagon arrangements in Germany, Austria and the Czech Republic are examples.

Break of gauge

When a railway line of one gauge meets another railway line of a different gauge, there is a break of gauge. A break of gauge adds cost and inconvenience to traffic that must pass from one system to another.

An example of this is on the Transmanchurian Railway, where Russia and Mongolia use broad gauge while China uses the standard gauge. At the border, each carriage has to be lifted in turn to have its bogies changed. The whole operation, combined with passport and customs control, can take several hours.

Other examples include any crossing into or out of the former Soviet Union: Ukraine/Slovakia border on the Bratislava-L'viv train, and from the Romania/Moldova border on the Chisinau-Bucharest train.

This can be avoided however by implementing a system similar to that used in Australia, where lines between states using different gauges are built as dual gauge. Thus the lines have 3 rails, one set of two forming a standard gauge line, with the third rail either inside or outside the standard set forming rails at either narrow or broad gauge. As a result, trains built to either gauge can use the line.

Standard gauge in Model railways

In American model railroading, standard gauge was originally an effort by Lionel Corporation to corner the U.S. market in the early years of the 20th century. Lionel standardized its offerings on three-rail track with a gauge of 2 1/8 in (54 mm) between the outer rails, making it incompatible with Gauge 1 offerings from European manufacturers. Lionel then registered a trademark on Standard Gauge. Other American companies followed Lionel's lead, standardizing on Lionel's new standard but calling it Wide gauge in order to avoid infringing on Lionel's trademark.

Standard gauge fell out of favour in the 1930s because of its high cost, and Lionel discontinued its Standard gauge offerings in 1940.

Although scale modeling was not of primary concern, standard gauge's scale is generally accepted at 1:26.59, making it somewhat smaller than G scale.

More recently, standard gauge has come to mean scale modelling in which the track is accurately scaled to real-world standard gauge. This is opposed to narrow gauge modeling, which models real-world narrow gauge, or off-scale modeling, where track is not true to scale, such as in O gauge.

References

• Pomeranz, Kenneth and Steven Topik (1999). The World That Trade Created: Society, Culture, and World Economy, 1400 to the Present. M.E. Sharpe, Inc., Armonk, NY. ISBN 0-7656-0250-4. 

External links

• Snopes History of standard gauge dating from Roman times (Snopes labels this as false).
• Jane's World Railways (hard copy)