Sees with double spacing

A way with double (or multi) spacing is an element of Railway allowing the circulation of materials several spacings on the same platform. In the majority of the cases, the ways with double spacing consist of three identical rails (example of Japan, of the Railroad of Vivarais in France) whereas there are normally only two of them. The two external rails are used for the broadest spacing while of one of the two external rails and another rail, placed at interior, circulation allows the more restricted spacing. One of the files of rail is common to the both spacing and wears a little more quickly. This configuration of ways should not be confused with the Conductor rail, used for the power supply.

Configurations

So that a way with two spacing can be consituée of three files of rail, it is necessary that the difference between the spacing is sufficiently important in order to allow the fixing of the rails (coach screws, nails, bolts, according to the country and technology) which requires a certain space. A case encountered in South Africa mixes spacings of one meter and 1067 mm: the spacings are too close to allow a way three files. In these cases, one uses 4 overlapping files of rail. This situation also meets in France, on the Railroad of Bay of Somme, but for other reasons: this line often saw the circulation of material with normal way, to avoid having to buy engines with this spacing the company had recourse to its machines with metric gauge track provided with a central plug and a coach provided with dimensions of a plug " métrique" and other with dimensions of a conventional attachment and two plugs. The axis of the ways having to be the same one, the metric gauge track was placed in the center of the normal way.

While exploiting the overlap of the 4 files of rail, one can carry out a way with 3 spacings, case encountered for the ways of 1,435m; 1,067m and 1,0m.

CFBS preserves a portion of way to double spacing (metric and normal) on the line of Noyelles to Saint-Valéry-sur-Somme. This double spacing is carried out with 4 files of rails: the two interior rails are with the metric spacing and the two external rails are with the standard spacing. The material with spacing used on the network has a central plug whereas the material with normal spacing has two plugs. The attachment is the same one for the two spacings. There were coaches with double plugging (that is to say 3 plugs) to allow the use of a metric tractor for standard coaches and reciprocally.

Conversion of spacing

The ways with several spacings involve complications which show at which point the standardization spacing is an important thing. After the normal way started to be spread, a consensus made it possible to generalize it as much as possible. If a railway operator seeks to convert a spacing into another, it often helps to build a section with double spacing, as that was often done in the past.

If the spacing must be reduced, the cross-pieces can be preserved with some modifications. If the way must be widened, the cross-pieces used before can appear too short and at least some will have to be replaced by broader. A similar problem can be met about the rails, too light to support the new loads which a broader spacing allows. In fact such problems impose sometimes a way on two spacings. Another problem relates to the ways built after the years 1930: if the cross-pieces are not of wood, it is difficult to bore the clamp holes for the new spacing. Thus certain concrete cross-pieces are already planned for several spacings, if . During the convertion of the line of Melbourne to Adelaide in Australia of 5 ' 3" (broad way) to 4 ' 8 ½ (normal way), a double track in heavy rails was not possible, the shoes of rails being too broad. A special cross-piece " change of écartement" comprising a reversible sabotage for Pandrol fastener was used, which allowed the conversion of line into two weeks only.

In the suburbs of Adelaide, the cross-pieces out of wooden planned for the broad way were replaced by concrete cross-pieces planned for a possible change of spacing.

During the second world war, the projections (and moved back) of the Russian face involved ceaseless conversions of spacing.

Cost of an example

In 2005, the Railroads Pakistanais launched the convertion of 128km of the line of Mirpurkhas to Khokhrapar of the spacing of 1000 mm to that of 1676 Misters the cost was of Rs 1,800,000,000 (21,946 million euros), that is to say a little more than 171.000 euros per kilometer.

Methods of transition between spacings

Only representative methods will be quoted, but there are many kinds:

carrying Coach or carrying bogie trucks, which transport a material of a spacing on another. This system is especially used if the spacing of origin of the coach is broader. The quantities to be transported cannot be too important and speed is limited.
Exchange of the Bogie truck S, system which consists in raising the vehicle and to exchange its rolling members. It is the system used between France and Spain for the goods trucks.
Material with variable spacing, on which the spacing between the wheels can be increased or reduced. It is the case of Talgo France/Spain.
Transshipment, consisting in making pass the passengers (or the goods) of a train to another. This operation is inexpensive, but it takes time (for the goods) and is not very appreciated (for the passengers)
Utilization of Container S.

Double spacing, double food

Minis Subway with Gijon, in Spain at the same time with metric gauge and broad track and are electrified in (1500V continu/3000V continuous).

Reference

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