Narrow gauge dreams   Leave a comment

So, often when I’m gone for awhile, I’m thinking about one of my subjects of interest obsessively.  Of late it’s been nuclear reactors, intermodal freight and Star Wars.  It is far easier for me to write about one part of  the intermodal freight thoughts than an the others, so here goes.

I like to pretend that I could take over Russia in the early 1800’s, and what I would do for a transportation network.

I’d begin by switching to the metric system, and then adopting a sort of Decauville system, 80 years early.   Decauville had several standardized engines and track systems which worked like a giant model railway, with pre-made sections of track that were made to portable by one or two men on foot.  It was a fantastic idea.  All the trench railways of WWI were Decauville or Decauville compatible.

My first idea was start with the smallest narrow gauge that has ever been profitable, the 400mm, and then advance in 50% increases, like this.

0.4 m, 0.6 m, 0.9 m, 1.35 m, 2.025m, but decided to simply squish the 900-1350mm section in the middle into one, 1m gauge, and simplify the 2025mm down to a nice, simple 2000 mm (It’s only 2.5% difference after all.)  That gives a nice, simple 4 part progression of of.

400, 600, 1000, 2000 mm.    Why all 4?

The 400mm gauge is TINY.  This is why the militaries did not consider it for colonial or military narrow gauges.  Why bother at all?  2 reasons: First, tiny means light, and portability is often an advantage worth the compromise.  They could be reliably and safely pushed around by a single person, something larger ones could not. Remember that the days of these things were before trucks, before conveyer belts, and before tractors.  These toy-like trains were the 4×4 trucks of their day, and thousands were used by contractors.  As you dug a hole, the dirt went in the train. As the digging moved, it was no problem to pick up the light track and redirect the trains.  The second, sometimes inches matter.  A purposed railway through a terrible pass in Burma was suggested to be 400mm because the extra handbreadth of 500mm or more was simply undoable in the terrain.

(Let’s skip the 600mm for the moment)

The 1 m is the world standard for narrow gauge. 750mm up to 1067 (Cape gauge) covers virtually every major narrow gauge on earth.  Oddly, at these narrow rail gauges, the loading gauges are surprising similar, which was one of my reasons to go with the 1 m standard.  If you need a normal run of the mill railroad, with mixed freight and passenger service, through rough terrain, 1 m gauge (or the nearly identical 3 foot gauge) is used worldwide.

2 m is larger than any normal gauge in use, but not as much as you might think.  India and a few other places have thousands of kilometers of 5’6″  gauge (1676mm) rail.  The reason for jumping the extra 324mm up to 2 m is for sake of containerization, intermodal transport and standardization.  The 1 m loading gauge is about 2.25m.  2 m gauge allows you load 2.25m wide cargo 2 across, for a loading gauge of 4.5 m.  They could be double stacked as well which allows for terrific capacity, yet clearly not unreasonable since it is only an improvement over what is currently available.  The 400mm would have a proportionally higher loading gauge, and could take a standardized pallet of 1.125 m (very close to the standard US pallet, which is the most profitable type in existence.)

But what of the 600mm?

It could only take the pallets at single width, just like the 400.  It couldn’t take containers at a 2.25 width like the 1m.  Why then?  The 600mm (virtually identical in service to the 2 foot gauge) has been described as “the biggest little”.   In many places which had both 3 foot and 2 foot equipment, it was the 2 foot gauge that lasted the longest.  This was the gauge all the militaries chose for their military and colonial railroads.  Thousands of kilometers of 2 foot gauge rail criss-cross Australian sugar  plantations.  The promise of narrow gauge was go further for less, and it seems that the 600mm is the best gauge at meeting the promise of narrow gauge.  The 40% larger 1 m gauge frequently costs nearly as much as full gauge, and is only justifiable in very rough terrain.  The 50% smaller 400mm is often just too small to be worth the effort.   400mm has been the choose of odd circumstance and portability. 1 m the chose of common service in uncommon terrain, but the 600mm is the ideal compromise gauge.  Further, while containerization and pallets are nice…they are not the only thing railroads to.  Railways often carry both bulk freight and passengers.  The 1524 mm  loading gauge of  the 600 mm gauge allows bigger cars and comfier seating.  If you truly need minimal, scraping by but barely rail service, 600mm is the way to go.  Also, there are special railways.

The longer and faster the train, the more profitable.  Long fast trains need shallow changes of elevation (not much more than 2%) and gentle curves.  In rough terrain this can be horribly expensive, which is why long, fast trains through mountains are so often 1 m gauge. (Narrower gauge means smaller tunnels, and tighter curves).  With short enough trains and specialized engines (all axles powered) inclines of up to around 10% are possible, but for around 11-24% inclines, you need cog railways (essentially you put a pinion on your drive axle and rack between the rails.  For 25%-50% you need a different kind of cog railway, with the rack making a T in the center, teeth pointing out, and the cogs turning horizontally, 90 deg off from vertical. (For anything over 50% your technology becomes much less a train and much more of an elevator on rails. It’s called a funicular.)  I think that the 600mm gauge should be the specified gauge for cog ways, since such specialized railways are rarely common carriers and often twist through rough terrain. (Yet you want to do it with the largest common, making the 400mm to small.)

So my plan (if I could start fresh circa 1800) would go like this:


Standardized containers of 2.25 x 2.25 x 9 m  (About 7 x 7 x 29 1/2 feet)

Pallets of 1.125 m square for the containers.

Five key features matter when laying out railways: gauge, loading gauge (for tunnels and right of way size), grade, curvature (the radius of turns), and axle load (tons per axle.)

The 2 m gauge would have three standards.  Heavy, Standard, and Light.  Heavy and Standard would have identical loading gauge, but would be different regarding grade, curvature, and axle load.  The heavy would be specified to have shallow grades, long radius turns and high axle loads.  Standard would be just be rougher and slower, but sill made for the same 4.5 m X 4.5 m cargo size.  Light would the steepest (perhaps around 10%) and curviest with the lightest possible axle load, and the 2.25 m loading gauge of the 1 m line.

The 1 m gauge would have 2 standards: Standard and Light. (There is no heavy, because if it needs to be heavy for 1 m gauge, it should be laid as 2 m gauge).  The goal for 1 m Standard would be to meet or excede the right of way standards for 2 m Light standards whenever possible, with the acceptance that some tighter curves are acceptable hear and there, but with shallower maximum grade.  (In both the Light 2 m and the Standard 1 m, tunnels are avoided when ever feasible, with the plan being to put in Standard 2 m tunnels when traffic warrants conversion from either Light 2 m or Standard 1 m). Light would be the steepest, curviest, and lowest axle load possible.

The reason for these over lapping standards is that very lightly built full gauge is usually preferable to narrow gauge.  Narrow gauge is made without the room to grow that full gauge has and costs more per ton to operate.  Thus, it should only be used when truly necessary.  Despite the loading gauge problems of small bore tunnels and the axle load problems of light bridges, the fullest single network (even if some is composed of low grade parts) is better than two separate networks.  If nothing else, the ability to move things without break of gauge (even through a highly restricted loading gauge) is superior.  The reason is that light full gauge equipment has 100% interchangeability thought the network, where as narrow gauge can only be used on narrow gauge.

The 400 mm Standard would be very simple, as it it would be standardized components rather than standard practice, more like laying pipe than laying street.  Being it is designed to set on, rather than in the land it operates in.  The preferred loading gauge standard would be to accomodate the standard pallet, but pallet handling is only one facet of the 400mm railroad’s applications, and should not be a hang up.

The 600mm would have 2 standards.  The Short Term and Long Term.  Short Term would be a scaled up modular “toy train” system like the 400 mm, and subject to the same ad hoc basis. Long Term would be more like a miniature version of the Standard 1 m.



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