Talk:Minimum railway curve radius

Minimum radii

Under "Factors affecting the minimum curve radius", it is stated that "normally 410-foot (125.0 m) radius is used as a minimum". I cannot find any source that says that. None of the listed sources say this. The 350 foot radius is the AAR recommendation, and there is a recommendation for 717 foot radius for freight trains. Can anyone find the 410-foot data anywhere? If not, I think we should remove it, since it has no sources. — Preceding unsigned comment added by 68.102.150.123 (talk) 23:21, 15 September 2014 (UTC)

Minimum radii for most existing railways may be found in Jane's World Railways. Peter Horn 15:44, 18 June 2009 (UTC)

Masses after curve radii

What is the significance of the masses given after the curve radii at Batlow, Homebush and Border Loop? As an interested non-rail expert, I can see the point of the speed restrictions given after some items in the list, but why masses?

Heavy trains cannot be pulled around sharp curves lest the wagons be pulled off the tracks. This a downside of cheap sharp curves. FYI, a couple of known examples are given. Jane's does not appear to be bothered with such niceties. Tabletop (talk) 05:50, 3 July 2010 (UTC)

I wondered if that was it, but initially I couldn't see why. If each wagon of a long train is twice as heavy, twice the longitudinal force is needed to accelerate the train at a given rate, which doubles the undesirable lateral force tending to overturn the wagon or at least make it ride up the inner rail - but then twice the force is needed to produce the same effect because the wagon is twice as heavy! Having investigated further, I think the problem arises because the centre of mass of a wagon rises as you load it (because the additional mass is all placed above the height of the coupler)... RedGreenInBlue (talk) 17:16, 13 August 2010 (UTC)

Also, if I understand the Wikipedia MOS, these masses should be in standard metric units, not US customary units. They are describing characteristics of railway infrastructure in a fully metric country (Australia), as part of an article that is not US-specific. Am I missing some quirk of Australian railway engineering practice? User:RedGreenInBlue (talk) 11:19, 4 August 2009 (UTC)

Long, short and metric tons for the purpose of this exercise amount to the same thing. Tabletop (talk) 05:50, 3 July 2010 (UTC)

Crikey, I hope most railway design uses tighter tolerances than this (the long ton is 12% larger than the short ton). But thanks for the reply RedGreenInBlue (talk) 17:16, 13 August 2010 (UTC)

Order

Unlike Jane's which orders its radii by country, this item orders its radii first by gauge and then by radii. Tabletop (talk) 06:05, 3 July 2010 (UTC)

Jointed v. Welded Rails

Would jointed track do poorly compared to welded track, which would be smoother? Joints would also have been very weak before there weree fishplates. Tabletop (talk) 10:48, 5 September 2010 (UTC)

A (nonwelded) rail joint in the midst of a curve would surely be a weak point, abused by wear and tear, and presenting a place for broken rails and derailment.

Also, in North America, steel rails are manufactured and distributed in quarter-mile lengths, and then welded together. There are probably engineering practices to avoid putting the (welded) joints in the midst of curves. [Some of the 1/4 mile sections might have to be shortened.]75.167.103.151 (talk) 04:08, 28 March 2020 (UTC)

Clarification needed

This article is not clear to me, and I think the problem is with the lead of the article. It does not define what a minimum railway curve radius is... Of course I'm not stupid, so I can guess what it means, but that shouldn't be necessary. A link to Track transition curve in the lead may be useful. It is also not stated in which respect it is a minimum. The legal minimum? The technical minimum?

Then the 'Minimum radius' section is in a strange format. This would probably be better presented in a table. Moreover, the numbers are not sourced. And not explained; I can guess that '1,435 mm (4 ft 8 1⁄2 in) 7,000 m (22,966 ft)' means that the curve radius is 7000 meter if the track gauge (this link would be helpful) is 1.435 m, but I should not have to guess this, it should be in the article. Further below, the 0-4-0 section does not even say which curve radius is used, so the information on the track gauge is completely useless... Or am I missing something? The formula for high-speed rail is nice, but the source is missing. And the context too: is it only valid for high-speed rail? --EdgeNavidad (Talk · Contribs) 17:21, 4 May 2011 (UTC)

The formula, in metric terms, would be valid to calculate the minimum radius for any speed so long as there is a cant and a cant deficiency. If there is no cant, then another formula would likely apply. Peter Horn User talk 23:46, 29 May 2011 (UTC)

This is strictly a design minimum, in other words the radius is in function of any one, or more than one, of the following factors.

1. Cost of construction.
2. Space available
3. Intended maximum speed.

• In the mountains
  • Mountain railways
• In an urban setting
  • Light rail
  • Street running around street corners in the case of tramway tracks, etc

Peter Horn User talk 23:46, 29 May 2011 (UTC)

Additional clarifications

Minimum railway curve radius#High-speed rail

$r={\frac {G\left({\frac {v}{3.6}}\right)^{2}}{g(ha+hb)}}$

where G is the rail gauge in millimetres??, v is speed (km/h), g is gravitational acceleration (9.8 m/s²), ha is cant, and hb is cant deficiency.

(9.8 m/s² or 32.15 ft/s²)
What would the formula be if 'G' is given in 'inches', the speed 'v' in 'mph' and the gravitational acceleration as '32.15 ft/s²' etc? Peter Horn User talk 23:13, 29 May 2011 (UTC) Peter Horn User talk 14:22, 30 May 2011 (UTC)

The formula should probably be converted to basic units, i.e. $r={\frac {Gv^{2}}{g(ha+hb)}}$. No one in their right mind would do math with a speed in km/h ... it also begs the question why the track gauge $G$ is in millimetres in the original expression?!213.112.159.147 (talk) —Preceding undated comment added 21:44, 16 January 2012 (UTC).

When the formula is shown rearranged for r=, the right-most fraction has inexplicably (and erroneously) been inverted. — Preceding unsigned comment added by LibraSunNOLA (talk • contribs) 13:59, 21 October 2013 (UTC)

Wollstonecraft high level platform

Who wrote "Wollstonecraft High Level Platform". This terminology is not used in Australia to the best of my knowledge. Furthermore, it is ambiguous. In the USA they distinguish between "high level" and "low level" platforms, by the actual high of the platform relative to the rails, which determines whether passengers need to climb stairs to get into the rail passenger vehicle. Whereas in UK terminology, "high level platform" would mean the platforms at the higher level of a station which has tracks at more than one level. So I am changing it.Eregli bob (talk) 11:13, 16 September 2012 (UTC)

Centrifugal force is not countered by cant

The article says "As a heavy train goes round a bend at speed, the reactive centrifugal force the train exerts on the rails is sufficient to move the actual track, which is only held in place by ballast. To counter this, a cant (superelevation) is used". This doesn't make sense. Canting the rails will not affect the reactive centrifugal force. Occultations (talk) 10:28, 23 December 2014 (UTC)

I agree this section is confusing, The purpose of the cant is more to reduce the sideways forces on passengers and cargo, rather than to stabilize the tracks, which must be anchored firmly to resist these forces. Reify-tech (talk) 16:22, 23 December 2014 (UTC)

The cant does not reduce the reactive centrifugal force, but it changes the plane of the track such that the resultant force (the combination of gravitational and centrifugal forces) can be exerted directly downward the track evenly to both inside and outside rail. Without the cant, the same amount of resultant force will be exerted toward the outside rail more than the inside rail. The unbalanced force exerted to the outside rail causes the outside rail to wear out faster or to be damaged (http://www.highspeed-rail.org/Documents/PRIIA%20305%20DocSpec%20and%20other%20NGEC%20Documents/305%20PRIIA%20Tilt%20presentation.pdf). Z22 (talk) 03:35, 29 September 2015 (UTC)

This is most certainly true from the point-of-view of physics and engineering.75.167.103.151 (talk) 03:59, 28 March 2020 (UTC)

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"Sleepers"

The word "sleeper" in railroading is unknown in North America.
In the United States and Canada, we call them "railroad ties".
I only found out about "sleeper" when reading about railroading in Australia.
Looking at it quantitatively, the United States has more miles of railroads than any other country. (Southern) Canada just adds to the total, and in the two countries, the technology and terminology for railroads and their equipment are identical (except in French).
This is all quite logical, because trains cross the border in both directions every day. There are even regular trains that cross from Canada (Quebec) to the U.S. (Maine), and back into Canada again (New Brunswick). Likewise, for trains that cross from Canada (Ontario), to the U.S. (Minnesota), and back into Canada again (Manitoba).
In transportation, telecommunications, and electric power, the U.S. and Canada are very tightly tied together.75.167.103.151 (talk) 03:54, 28 March 2020 (UTC)

It looks like the only usage of "sleepers" in the article is once in the table. It looks like it is a situation where it's called "sleeper" in British English and "tie" or "railroad tie" in US English.North8000 (talk) 12:13, 28 March 2020 (UTC)

The article uses British railroading terminology in a number of subtle ways — it refers to "railways" rather than "railroads", "bogies" rather than "trucks", and (as you noticed) "sleepers" rather than "ties". I've now marked the article as using British English. I don't really buy your argument that this topic is strongly tied to North American practice — or, at least, not enough to change the dialect. The US is larger than Britain, so we're going to win most pissing contests, which makes those contest (relatively) irrelevant; I don't see how "number of track miles built" is an exception. Bernanke's Crossbow (talk) 20:51, 7 May 2022 (UTC)

History behind…

The use of rubber tires on rolling stock circa 1943 2601:280:4201:4F70:315E:8170:AE4A:62AB (talk) 18:43, 25 December 2022 (UTC)