Gauge conversion - AbsoluteAstronomy.com

Rail transport

Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

, gauge conversion is the process of converting a railway from one rail gauge

Rail gauge

Track gauge or rail gauge is the distance between the inner sides of the heads of the two load bearing rails that make up a single railway line. Sixty percent of the world's railways use a standard gauge of . Wider gauges are called broad gauge; smaller gauges, narrow gauge. Break-of-gauge refers...

to another, through the alteration of the railway tracks. An alternative to gauge conversion is dual gauge

Dual gauge

A dual-gauge or mixed-gauge railway has railway track that allows trains of different gauges to use the same track. Generally, a dual-gauge railway consists of three rails, rather than the standard two rails. The two outer rails give the wider gauge, while one of the outer rails and the inner rail...

track, or gauge conversion of the rail vehicles themselves.

Ideally railways should all be built to the same gauge, since a wide range of gauges from narrow to broad are of similar value in carrying heavy loads at low cost, while small differences of gauge create tremendous break-of-gauge

Break-of-gauge

With railways, a break-of-gauge occurs where a line of one gauge meets a line of a different gauge. Trains and rolling stock cannot run through without some form of conversion between gauges, and freight and passengers must otherwise be transloaded...

costs and inconvenience.

Rail vehicles

Gauge conversion of coaches and wagons involves the replacement of the wheelsets

Wheelset (railroad)

A wheelset is the wheel-axle assembly of a railroad car. The frame assembly beneath each end of a car, railcar or locomotive that holds the wheelsets is called the bogie...

or entire bogie

Bogie

A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

s, such as happened when the gauge of the Great Western Railway

Great Western Railway

The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...

was abandoned in May 1892. Where vehicles regularly work to and fro across a permanent change of gauge, for example between the system in France and the in Spain, stations are equipped with special bogie exchange

Bogie exchange

Bogie exchange is a system for operating railway wagons on two or more gauges to overcome difference in the track gauge. To perform a bogie exchange, a car is converted from one gauge to another by removing the chassis containing the wheels and axles of the car, and installing a new chassis with...

equipment. Some vehicles nowadays are fitted with variable gauge axles

Variable gauge axles

A variable gauge system allows railway vehicles in a train to travel across a break of gauge caused by two railway networks with differing track gauges....

which do not require any exchange of the wheelsets, but still require special equipment. This temporary alteration to allow through working is generally referred to as "gauge change".

Steam locomotives are difficult to convert unless this is already allowed for in the design, such as in some East African Railways Garratt

Garratt

A Garratt is a type of steam locomotive that is articulated in three parts. Its boiler is mounted on the centre frame, and two steam engines are mounted on separate frames, one on each end of the boiler. Articulation permits larger locomotives to negotiate curves and lighter rails that might...

s, and in steam locomotives built for Victoria after 1930s. In the event, few have been so converted, but one such is Victorian Railways R class

Victorian Railways R class

The R class was an express passenger steam locomotive that ran on Australia's Victorian Railways from 1951 to 1974. A long overdue replacement for the 1907-era A2 class 4-6-0, their development and construction was repeatedly delayed due to financial constraints caused by the Great Depression and...

R766.

Sleeper types

Often gauge convertible sleepers are installed before the conversion of the rails themselves. Sleepers have to be long enough to take the wider of the gauges, and secondly, the sleepers must be able to take the fittings of both gauges. Gauge convertibility can also be a stepping stone to dual gauge

Dual gauge

. In cases where the differences between the gauges are small, such as / and /, dual gauge with a third rail is not practicable, in these cases four rail dual gauge is necessary.

Timber sleepers, provided that they are long enough, are always gauge convertible, since additional holes for the dogspikes can always be drilled later. If the new gauge is wider than the old, a shorter than normal sleeper can be tolerated to a degree.

Concrete sleepers cannot be converted as an afterthought, but must have the future fittings cast in place when manufactured.

Steel sleepers should have the extra fitting incorporated when manufactured, though it might be possible to drill or weld the fitted sleeper after installation with some difficulty.

Loading gauge

Narrow gauge railways often have a significantly smaller loading gauge

Loading gauge

A loading gauge defines the maximum height and width for railway vehicles and their loads to ensure safe passage through bridges, tunnels and other structures...

in both height and width. Conversion to a wider track gauge will often require enlargement of the loading gauge, by raising bridges and enlarging tunnels, if any.

The minimum radius curve of a narrow gauge railway is often less than a wider gauge, which may require deviations to ease such curves.

Track centres at stations with multiple tracks will also have to be widened. This would be less of a problem on the usually single track main lines of the narrow gauge railway.

Gauge orphan

During gauge conversion work such as between Seymour

Seymour, Victoria

Seymour is a township in the Shire of Mitchell in the state of Victoria, Australia and is located north of Melbourne. At the 2006 census, Seymour had a population of 6,063...

and Albury

Albury, New South Wales

Albury is a major regional city in New South Wales, Australia, located on the Hume Highway on the northern side of the Murray River. It is located wholly within the boundaries of the City of Albury Local Government Area...

, branch lines such as Benalla to Oaklands

Oaklands railway line, Victoria

The Oaklands railway line is a freight only railway line in north eastern Victoria, Australia. The line branches from the main North East railway at Benalla station until it connects with the New South Wales railway network at Oaklands, New South Wales....

and stations such as Violet Town become gauge orphans as they cannot easily be served by trains until extra costly work is done.

In this instance, the loading gauge of the broad gauge

Broad gauge

Broad-gauge railways use a track gauge greater than the standard gauge of .- List :For list see: List of broad gauges, by gauge and country- History :...

and standard gauge

Standard gauge

The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...

lines are essentially the same.

Rail vehicles

Sleeper types

Loading gauge

Gauge orphan

See also