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New Australian coal line: why narrow-gauge?

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New Australian coal line: why narrow-gauge?
Posted by timz on Saturday, October 16, 2021 6:21 PM

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?

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Posted by Backshop on Saturday, October 16, 2021 7:12 PM

42in is standard for Queensland. 8146km of 42" and only 117km of standard.

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Posted by PNWRMNM on Sunday, October 17, 2021 7:53 AM

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

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Posted by daveklepper on Sunday, October 17, 2021 10:51 AM

Clearances on South Africa's 42"-gauge system are larger than those on the UK's standard-gauge standard gauge system.

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Posted by Euclid on Sunday, October 17, 2021 1:04 PM

PNWRMNM

Just because standard gauge is so called, does not make it the 'right' gauge in an economic sense. 

Mac

 

That is a good point.  There is nothing magical about 56.5 inches.  It is only "standard" because the greatest consensus preferred it.  That was because once it began to emerge as a preference, no new builder wanted to be outside of that consensus.  If they were, they would not be able to interchange traffic without complications.  

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Posted by greyhounds on Sunday, October 17, 2021 1:40 PM
Brazil is predominately meter gauge.
 
It’s amazing what they do with that.  Heavy haul iron ore trains, etc.   On meter gauge.  They use North American size locomotives on eight axels instead of six.  Lots of DPU.  For the railroads in Brazil there’s no such word as “Can’t.”
 
They’ve got some 5’ 3” gauge too.  But it’s predominately meter gauge.  And they make that work.
 
"By many measures, the U.S. freight rail system is the safest, most efficient and cost effective in the world." - Federal Railroad Administration, October, 2009. I'm just your average, everyday, uncivilized howling "anti-government" critic of mass government expenditures for "High Speed Rail" in the US. And I'm gosh darn proud of that.
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Posted by Overmod on Sunday, October 17, 2021 6:18 PM

timz
So what's the advantage of narrow gauge, if you're planning to move solid trains of coal?

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...

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Posted by PNWRMNM on Sunday, October 17, 2021 9:17 PM

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.

Mac

 
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...

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Posted by blue streak 1 on Friday, October 22, 2021 1:28 PM

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 ?

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Posted by PNWRMNM on Friday, October 22, 2021 2:57 PM

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

 

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Posted by BaltACD on Friday, October 22, 2021 3:02 PM

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!

              

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Posted by Overmod on Friday, October 22, 2021 3:45 PM

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.

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Posted by BaltACD on Friday, October 22, 2021 4:11 PM

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.

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.

Never too old to have a happy childhood!

              

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Posted by Euclid on Friday, October 22, 2021 5:43 PM
Center bound ties form as ballast directly under the rails is compressed by the loading and rocking action of the car trucks.  Ballast can displace by flowing out at the shoulders at the ties ends.  This increases the load being carried by the more supportive center portion of the ties.  The center support encourages more rocking and oscillation of the cars, which further continues the damage. 
 
Here is a link describing the effect with concrete ties:
 
 
From the link:
 
“The 165 cyclic track loading causes the ties to oscillate and deform vertically; over time this pumping action 166 abrades the bottoms of the ties and pulverizes the supporting ballast. When the pulverized ballast is not 167 timely removed and replaced with new ballast, depression in the pulverized ballast under the ends of the 168 ties may develop, altering the ballast support to the center of the ties while allowing the ends to behave 169 like cantilever beams. This can cause large negative moments in the center and consequently “center 170 negative” or “center bound” cracks in the concrete ties (10). According to the UIUC survey, center bound 171 cracks rank fifth among the eight most critical concrete tie and fastener failure modes in the North 172 American railroads (5).”

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