Variable gauge

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.
For through-operation, a train must be equipped with special bogies holding variable gauge wheelsets containing a variable gauge axle (VGA). The gauge is altered by driving the train through a gauge changer or gauge changing facility. In effect, the track widens or narrows.
As the train passes through the gauge changer, the wheels are unlocked, moved closer together, or further apart, and are then re-locked. Installed variable gauge systems exist within the internal network of Spain, and are installed on international links between Spain/France (Spanish train), Sweden/Finland (Swedish train), Poland/Lithuania (Polish train) and Poland/Ukraine (Polish train).
A system for changing gauge, without need for stopping is widespread for passenger traffic in Spain, used in services run on a mix of dedicated high-speed lines (using Standard gauge) and older lines (using Iberian-gauge). Similar systems for freight traffic are still rather incipient, as the higher axle weight increases the technological challenge. Although several alternatives exist, including transferring freight, replacing individual wheels and axles, truck exchange, transporter flatcars or the simple transshipment of freight or passengers, they are impractical, thus a cheap and fast system for changing gauge would be beneficial for cross-border freight traffic.
Alternative names include Gauge Adjustable Wheelsets (GAW), Automatic Track Gauge Changeover System (ATGCS/TGCS), Rolling Stock Re-Gauging System (RSRS), Rail Gauge Adjustment System (RGAS), Shifting wheelset, Variable Gauge Rolling Truck, track gauge change and track change wheelset.
Overview.
Variable gauge axles help solve the problem of a break-of-gauge without having to resort to dual gauge tracks or transshipment. Systems allow the adjustment between two gauges. No gauge changer designs supporting more than two gauges are used.
Systems.
There are several variable gauge axle systems:
Compatibility.
The variable gauge systems are not themselves all compatible. Only the SUW 2000 and Rafil Type V systems are interoperable.
In 2009, at Roda de Barà near Tarragona, a Unichanger capable of handling four different VGA systems was under development.
International traffic.
VGA is particularly important with international railway traffic because gauge changes tend to occur more often at international borders.
Speed.
The maximum speed of the trains equipped with the different technologies varies. Only CAF and Talgo produce high-speed VGA, allowing speeds up to 250 km/h.
Gauge changer.
A gauge changer is a device which forces the gauge adjustment in the wheels. Designs consist of a pair of running rails that gradually vary in width between the two gauges, combined with other rails and levers to unlock, move, support and re-lock the adjustable axles.
In the Spanish Talgo-RD system, a constant spray of water is used to lubricate the metal surfaces, to reduce heat and wear. A Talgo-RD gauge changer is 20 metres long and 6 metres wide.
Operation.
Variable gauge multiple units, or a train including a variable gauge locomotive (e.g. Talgo 250) and rolling stock, may drive straight across a gauge changer. Normally the locomotive will not be able to change gauge, meaning that it must move out of the way whilst the remainder of the train itself passes through. On the opposite side, a new locomotive of the other gauge will couple to the train.
A train (or an individual car) can be pushed halfway across the gauge-changer, uncoupled, and then (once far enough across) coupled to the new locomotive and pulled the rest of the way. A long length of wire-rope with hooks on the end means that the process can be asynchronous, with the rope used to bridge across the length of the gauge changer (to temporarily couple the arriving cars and receiving locomotive, although without braking control from the locomotive to the train vehicles).
On long-distance trains in Spain and night trains crossing from Spain into France, the arriving locomotive stops just short of the gauge changer, uncouples and moves into a short siding out of the way. Gravity then moves the train through the gauge changer at a controlled low speed. The new locomotive is coupled onto the front only after the full train has finished passing through the changer.
Countries.
Australia.
In 1933, as many as 140 inventions were offered to Australia railways to overcome the breaks of gauge between the different states. None was accepted. About 20 of these devices were adjustable wheels/axles of some kind or another, which may be analogous to the modern VGA. VGA systems were mostly intended for Broad Gauge and Standard Gauge lines.
Canada.
Variable gauge axles were used for a while on the Grand Trunk Railway in the 1860s in Canada to connect and standard gauge without transshipment. Five hundred vehicles were fitted with "adjustable gauge trucks" but following heavy day-in, day-out use the system proved unsatisfactory, particularly in cold and snowy weather. The system used telescoping axles with wide hubs that allowed the wheels to be squeezed or stretched apart through a gauge-changer, after holding pins had been manually released.
Railway operations over the Niagara Bridge were also complicated.
Finland/Sweden.
In 1999, a gauge-changer was installed at Tornio at the Finnish end of the dual-gauge section between Haparanda and Tornio, for use with variable gauge freight wagons. The Tornio gauge changer is a "Rafil" design from Germany; a similar "Talgo-RD" gauge changer at the Haparanda end used to exist, but was removed as it required de-icing in winter.
Train ferry traffic operated by SeaRail and arriving from Germany and Sweden by sea used bogie exchange facilities in the Port of Turku.
Georgia.
A new gauge changer has been put in place in Akhalkalaki for Baku-Tbilisi-Kars railway. Northwestern end has rails apart, southeastern end has rails apart. Both bogie exchange and variable gauge adapters are provided.
Japan.
The "Gauge Change Train" is a project started in Japan in the 1990s to investigate the feasibility of producing an electric multiple unit (EMU) train capable of operating both the Shinkansen high-speed network at 270–300 km/h and the original network at 130–140 km/h. See .
The first-generation train was tested from 1998 to 2006, including on the US High-speed Test Track in 2002. The second-generation train, intended to run at a maximum speed of , was test-run in various locations in Japan between 2006 and 2013. A third-generation train has been undergoing reliability trials since 2014 in preparation for potential introduction to service on the planned Kyushu Shinkansen extension to Nagasaki.
Poland.
Poland has SUW 2000 gauge changers installed on international lines to Lithuania and Ukraine used for daily night-trains and some freight transport.
Spain.
Spain is the largest user of variable gauge systems. This is because of the need to connect older mainlines built to Iberian gauge and extensive new high-speed railway lines and connections to France, using the standard gauge. Two gauge changes are installed on lines to France and at all entrances/exits leading between the high-speed network and older lines. There are also significant lengths of secondary lines but these are not connected to the main network.
In February 2004, RENFE placed orders for:
Switzerland.
Variable gauge axles are going to be implemented on the Montreux–Gstaad–Zweisimmen–Spiez–Interlaken line. Trains will automatically switch from to at Zweisimmen. A trial bogie has been built and tested. It has no axles which allow the bogie half frames holding the wheels on both sides to slide sideways to each other.
Ukraine.
As part of a joint bid for the 2012 European Football cup with Poland VGA trains would be introduced across their border.
United Kingdom.
John Fowler mentions in 1886 at attempt by the GWR to develop a "telescopical" axle.
Trams ran between Leeds () and Bradford ( gauge) following a successful trial in 1906 using Bradford tram car number 124. The system was later patented by – GB190601695 (A) of 1906. This system was improved again in patent GB190919655 (A) of 1909 by introducing a locking system acting on the wheel and axle rather than just the wheel rim. This provided a more effective grip where the wheel was free to move along the splined axle.
Comparison with truck exchange.
Time taken.
In VGA, the train is pulled through the "adjuster" at about 10 km/h (2.77 m/s) without any need to uncouple the wagons or disconnect (and test) the brake equipment.
Locomotives.
Steam locomotive are generally not gauge convertible on-the-fly. While diesel locomotives can be truck exchanged, this is not normally done owing to the complexity in the reconnection of cables and hoses. In Australia, some locomotives are transferred between gauges. The transfer might happen every few months, but not for an individual trip.
By 2004, variable gauge electric passenger locomotives were available from Talgo. It is not clear if variable gauge freight locomotives are available.