User:Tabletop/Dual gauge for Africa

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Standard gauge (4 ft 8½ in, 1435 mm) and 3 ft 6 in (1067 mm) gauge (as found in Africa) are sufficiently dissimilar to allow 3-rail dual gauge track.

Proposal for Africa - a four rail system to support triple gauge (4 ft 8½ in, (1435 mm), 3 ft 3.375 in, (1000 mm) in and 3 ft 6 in (1067 mm) gauge), thus allowing system unification in Africa, Europe and the Middle East.

The most common gauges in sub-Saharan Africa are

1000 mm (3 ft 3.375 in)
1067 mm (3 ft 6 in)
1435 mm (4 ft 8½ in)

Unfortunately, these gauges are mixed up almost at random, which creates breaks-of-gauge should the various systems ever meet. One problem is that 1000 mm and 1067 mm are so close (they differ by only 67 mm) that three rail dual gauge is not practicable.

A 4 rail dual gauge will work for combining 1000mm and 1067mm, and in the process it creates a third gauge, which is not necessarily of any use. If the 4 rail dual gauge is designed carefully, then the accidental third gauge can be 1435 mm, the world standard railway gauge. It is noted that Nigeria has ambitious plans to convert to 1435mm.

1000 mm and 1067 mm gauges are too close to allow 3-rail dual gauge

1000 mm and 1067 mm gauges can be commoned with 4 rail dual gauge - note the useless 1267mm gauge.

1000 mm and 1067 mm gauges can be commoned with 4 rail dual gauge with bonus 1435 mm gauge

1 Bonus
2 Disadvantages
3 Australia
4 See also
5 Sources

[edit] Bonus

Much of Africa's railway systems has lightweight rails, which limits the axle load of the trains. It is costly to replace the rails, since rails use very high quality steel, and are expensive.

If the 4-rail triple gauge arrangement is adopted, then weight of the rails is effectively doubled, albeit not in the same shape of rails of double the weight. Some increase in axle load would therefore be possible reusing the old rails.

[edit] Disadvantages

Any dual gauge track will inevitably require custom made track tamping machines, etc; fortunately the manufacturers of track machines are used to making made to measure machines.

In the long term, when the narrow gauge lines cease to be required, only standard gauge will remain. It will then be desirable to replace the 4 x 30kg rails with 2 x 60kg rails. Unfortunately, the width of the foot of the light and heavy rail are not identical, so care must be taken to ensure that the sleeper are designed for the long term heavy rails, but are adaptable with fillets for the short term light rails.

If these problems are too much, then the solution is to bite the bullet and convert to standard gauge straight away.

[edit] Australia

Australia has a gauge muddle as bad as the one in Africa, which is being fixed at great cost. Gauge convertible sleepers is one way of reducing future gauge converion costs.

Like the "just in case" dual gauge sleepers on the Adelaide broad gauge network, African railways might consider adopting the proposed 4-rail configuration for any new concrete or steel sleepers, "just in case" as well.