It seems a new railroad is going to carry Queensland coal to the Pacific on 42-inch gauge track. Why? Like everyone, I assumed people only built narrow-gauge railroads when they couldn't afford a legitimate railroad. Apparently that's not true. So what's the advantage of narrow gauge, if you're planning to move solid trains of coal?
42in is standard for Queensland. 8146km of 42" and only 117km of standard.
Timz,
You do not say how much of this route will use existing 42" gauge line. I suspect new line is built to match the old line the traffic will utilize.
The capacity issue is axle loading. I suspect 42" can match standard gauge on this point. If so, then car capacity would match standard gauge. Even if axle loadings do not match, is probably cheaper to buy more cars than to build duplicate standard gauge line.
The point is, once any gauge is in place the low cost solution when building an extension is to simply match the existing gauge.
Just because standard gauge is so called, does not make it the 'right' gauge in an economic sense.
Mac
Clearances on South Africa's 42"-gauge system are larger than those on the UK's standard-gauge standard gauge system.
PNWRMNM Just because standard gauge is so called, does not make it the 'right' gauge in an economic sense. Mac
timzSo what's the advantage of narrow gauge, if you're planning to move solid trains of coal?
Many people assume that narrow gauge and 'light railways' are the same thing. In the 1870's and 1880's, the peak years of interest in narrow gauge as opposed to standard gauge, even standard gauge could be built as a 'light railway' as were most narrow gauge lines.
Light railways were characterized by lax engineering standards in terms of grades, curves and axle loadings, which minimized first cost. The argument for narrow gauge was that the equipment could operate around tighter curves and narrower roadbed meant less earth moving than standard gauge. The operational points were generally true, but tighter curves limit speed regardless of gauge. The big savings in roadbed was not the slightly narrower fills and cuts, but the elimination of much excavation due to lower standard of grade associated with the narrow gauges.
What killed most narrow gauge lines in the US was the cost of transloading at break of gauge. Some American NG lines were abandoned, but many of them were standard gauged.
In the Queensland case the most common, that is defacto standard, gauge is 42". We know nothing of the mileage of existing route to be used vs new construction. Lets imagine 400 miles of new construction at $2,000,000 per mile plus use of 100 miles of existing route at $0. That is $800 milliion first cost for the line. If built all standard gauge have 500 miles of new construction at say $2,100,000 per mile, or over a billion dollars, and that assumes no expensive urban real estate. Cost of locomotives is dependent on ruling grades, not gauge. I suspect axle loads and thus car carrying capacity, should be very similar as between gauges. Even if say 10% difference, which frankly I doubt, the capex budget can buy a lot of cars with $200,000,000 of construction savings.
If there is no plan to use existing track as part of the route, then builder has freedom of choice as to gauge.
The issue of standardization of railway gauge is discussed from a historical development perspective in the book 'Tracks across Continents, Paths Through History' by Douglas J. Puffert. It is a case study of standardization, using railroads to illustrate the process.
timz So what's the advantage of narrow gauge, if you're planning to move solid trains of coal?
Overmod Probably much lower fixed and construction costs, for a commodity that might have a sharply limited economic and political life in the relatively near future...
Probably much lower fixed and construction costs, for a commodity that might have a sharply limited economic and political life in the relatively near future...
About axel loading. If the axel loading is the same for a narrow guage line how will the load transfer to the roadbed ? Assume heavy coal loads. With shorter sleepers ( cross ties ) the load on the ballast underneath will be higher per sq inch.
Would that require more ballast, longer sleepers, closer spacing of sleepers, or shorter intervals for surfacing or some other item ?
blue streak 1 If the axel loading is the same for a narrow guage line how will the load transfer to the roadbed ? Assume heavy coal loads. With shorter sleepers ( cross ties ) the load on the ballast underneath will be higher per sq inch.
If the axel loading is the same for a narrow guage line how will the load transfer to the roadbed ? Assume heavy coal loads. With shorter sleepers ( cross ties ) the load on the ballast underneath will be higher per sq inch.
Streak,
Your statement would be true IFF the load was spread uniformally along the long axis of the tie. It is not.
Ties are tamped on both sides of the rail for 8-12 inches on both sides of the base of the rail, which is typically 6 inches. That leaves the center two feet or so of a standard gauge tie not doing much to support the load, so shortening the mostly non load bearing part of the tie by a foot or so does nothing in terms of loading of the subgrade.
Mudchicken could give a more detailed explanation.
PNWRMNM blue streak 1 If the axel loading is the same for a narrow guage line how will the load transfer to the roadbed ? Assume heavy coal loads. With shorter sleepers ( cross ties ) the load on the ballast underneath will be higher per sq inch. Streak, Your statement would be true IFF the load was spread uniformally along the long axis of the tie. It is not. Ties are tamped on both sides of the rail for 8-12 inches on both sides of the base of the rail, which is typically 6 inches. That leaves the center two feet or so of a standard gauge tie not doing much to support the load, so shortening the mostly non load bearing part of the tie by a foot or so does nothing in terms of loading of the subgrade. Mudchicken could give a more detailed explanation. Mac
All the tampers I have seen working, tamp both inside and outside the gauge.
Never too old to have a happy childhood!
BaltACDAll the tampers I have seen working, tamp both inside and outside the gauge.
Look up 'centerbound' if you need to, but I think you already appreciate it; MC or diningcar will tell you why it's such a dirty word.
Overmod BaltACD All the tampers I have seen working, tamp both inside and outside the gauge. They do, but as he said, within a fixed distance from the rail. Look up 'centerbound' if you need to, but I think you already appreciate it; MC or diningcar will tell you why it's such a dirty word.
BaltACD All the tampers I have seen working, tamp both inside and outside the gauge.
They do, but as he said, within a fixed distance from the rail.
The individual tamping 'forks' that are nearest the rail are angled such that the area directly under the rail gets fully tamped. All areas of the tie are fully and properly tamped.
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