Minimum railway curve radius
Wikipedia on Answers.com:
Top
Minimum railway curve radius
 |
This article may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (September 2008) |
The minimum railway curve radius, the shortest design radius, has an important bearing on constructions costs and operating costs and, in combination with superelevation (difference in elevation of the two rails) in the case of train tracks, determines the maximum safe speed of a curve. Superelevation is not a factor on tramway tracks. Minimum radius of curve is one parameter in the design of railway vehicles[1] as well as trams.[2]
|
Contents
|
History
The first proper railway was the Liverpool and Manchester Railway which opened in 1830. Like the trams that had preceded it over a hundred years, the L&M had gentle curves and gradients. Amongst other reasons for the gentle curves were the lack of strength of the track, which might have overturned if the curves were too sharp causing derailments. There was no signalling at this time, so drivers had to be able to see ahead to avoid collisions with previous trains. The gentler the curves, the longer the visibility.
In the early days, there was no information to help determine how sharp and steep lines could be, but over time curves did get sharper and gradients steeper.
Minimum radius
Minimum curve radii for railroads are governed by the speed operated and by the mechanical ability of the rolling stock to adjust to the curvature. In North America, equipment for unlimited interchange between railroad companys are built to accommodate 350-foot radius (16 degrees 26 minutes) or sharper, but normally 410-foot radius (14 degrees) is used as a minimum, as some freight cars are handled by special agreement between railroads that cannot take the sharper curvature. For handling of long freight trains, a minimum 717-foot radius (8 degrees) is preferred.
The sharpest curves tend to be on the narrowest of narrow gauge railways, where almost everything is proportionately smaller.[3][4]
| Gauge | Radius | Location | Notes |
|---|---|---|---|
| 1,435 mm (4 ft 8 1⁄2 in) | 7,000 m (22,966 ft) | China | Typical China's high-speed railway network (350 km/h) |
| 1,435 mm (4 ft 8 1⁄2 in) | 5,500 m (18,045 ft) | China | Typical China's high-speed railway network (250 km/h~300 km/h) |
| 1,435 mm (4 ft 8 1⁄2 in) | 4,000 m (13,123 ft) | China | Typical high-speed railways (300 km/h) |
| 1,435 mm (4 ft 8 1⁄2 in) | 3,500 m (11,483 ft) | China | Typical China's high-speed railway network (200~250 km/h) |
| 1,435 mm (4 ft 8 1⁄2 in) | 2,000 m (6,562 ft) | China | Typical high-speed railways (200 km/h) |
| 1,067 mm (3 ft 6 in) | 250 m (820 ft) | DRCongo Matadi-Kinshasa Railway | Deviated 1,067 mm (3 ft 6 in) line. |
| 1,435 mm (4 ft 8 1⁄2 in) | 240 m (787 ft) | Border Loop | 5,000 long tons (5,100 t; 5,600 short tons) - 1,500 m (4,921 ft) |
| 1,435 mm (4 ft 8 1⁄2 in) | 200 m (656 ft) | Wollstonecraft high level platform | |
| 1,435 mm (4 ft 8 1⁄2 in) | 200 m (656 ft) | Homebush triangle | 5,000 long tons (5,100 t; 5,600 short tons) - 1,500 m (4,921 ft) |
| 1,435 mm (4 ft 8 1⁄2 in) | 190 m (623 ft) | Turkey | Turkey[4] |
| 1,435 mm (4 ft 8 1⁄2 in) | 160 m (525 ft) | NSW, Zig Zag | 40 km/h |
| 1,435 mm (4 ft 8 1⁄2 in) | 100 m (328 ft) | NSW, Batlow, New South Wales | Weight limit: 500 long tons (510 t; 560 short tons) and 300 m (984 ft) - restricted to NSW Z19 class 0-6-0 steam locomotives |
| 1,067 mm (3 ft 6 in) | 95 m (311.68 ft) | Newmarket, New Zealand | Extra heavy concrete sleepers [5] |
| 1,435 mm (4 ft 8 1⁄2 in) | 85 m (279 ft) | Windberg Railway (de:Windbergbahn) | (between Freital-Birkigt and Dresden-Gittersee) - restrictions to wheelbase |
| 1,435 mm (4 ft 8 1⁄2 in) | 61 m (200 ft) | London Underground Central line | (between White City and Shepherd's Bush) |
| 1,067 mm (3 ft 6 in) | 60 m (197 ft) | Queensland Railways | |
| 762 mm (2 ft 6 in) | 50 m (164 ft) | Matadi-Kinshasa Railway | original 762 mm (2 ft 6 in) line. |
| 600 mm (1 ft 11 5⁄8 in) | 50 m (164 ft) | Welsh Highland Railway | |
| 1,000 mm (3 ft 3 3⁄8 in) | 45 m (148 ft) | Bernina Railway | |
| 600 mm (1 ft 11 5⁄8 in) | 40 m (131 ft) | Welsh Highland Railway | on original line at Beddgelert |
| 762 mm (2 ft 6 in) | 40 m (131 ft) | Victorian Narrow Gauge | 16 km/h/10 mph on curves ; (32 km/h/20 mph on straight ) |
| 762 mm (2 ft 6 in) | 37.47 m (122.9 ft) | Kalka-Shimla Railway | or 48 degrees |
| 1,435 mm (4 ft 8 1⁄2 in) | 27.43 m (90 ft) | Chicago 'L' | |
| 1,435 mm (4 ft 8 1⁄2 in) | 25 m (82 ft) | Sydney steam tram | Hauling 3 trailers |
| 610 mm (2 ft) | 21.2 m (70 ft) | Darjeeling Himalayan Railway | |
| 610 mm (2 ft) | 18.25 m (59.9 ft) | Matheran Hill Railway | 1 in 20 (5%); 8 km/h/5 mph on curve; 20 km/h/12 mph on straight |
| 1,067 mm (3 ft 6 in) | 10.67 m (35 ft) | Taunton Tramway | |
| 610 mm (2 ft) | 4.9 m (16 ft) | Chicago Tunnel Company | 6.1 m (20 ft) in grand unions. |
Steam locomotives
As the need for more powerful (steam) locomotives grew, the need for more driving wheels on a longer, fixed wheelbase grew too. But long wheel bases are unfriendly to sharp curves. Various type of articulated locomotives Mallet, Garratt, Shay were devised to avoid having to operate multiple locomotives with multiple crews.
More recent diesel and electric locomotives do not have a wheelbase problem and can easily be operated in multiple with a single crew.
Transition curves
Main article: Track transition curve
A curve should not become a straight all at once, but should gradually increase in radius over a transition length of say 40 m - 80 m. Even worse than curves with no transition are reverse curves with no intervening straight.
The super-elevation (aka cant) must also be transitioned.
K class garratt
The TGR K Class was
- 610 mm (2 ft) gauge
- 99 ft (30 m) radius curves
Example Garratt
- 1,000 mm (3 ft 3 3⁄8 in) gauge
- 25 kg/m (50.40 lb/yd) rails
- main line radius - 175 metres (574 ft)
- siding radius - 84 metres (276 ft) [6]
0-4-0
- GER Class 209
- 1,435 mm (4 ft 8 1⁄2 in)
Couplings
Not all couplers can handle very sharp curves. This is particularly true of the European buffer and chain couplers. The buffers get in the way.
Problem curves
- The Australian Standard Garratt had flangeless leading driving wheels which tended to cause derailments on sharp curves.
- Sharp curves on the Port Augusta to Hawker line of the South Australian Railways caused derailment problems when bigger and heavier SAR X class locomotives were introduced, requiring deviations to ease the curves.[7]
- 5-chain (101 m; 330 ft) curves on the Oberon railway line, New South Wales, limited steam locomotives to the 19 class.
High-speed rail
For high-speed rail much gentler curves are needed. A formula to calculate the minimum curve radius is:
where G is the rail gauge, v is speed (km/h), g is gravitational acceleration (9.8 m/s²), ha is cant, and hb is cant deficiency.
This table shows examples of curve radii. The values used when building high-speed railways varies, and depends on how much wear and safety desired.
| Curve radius | ≤ 120 km/h | ≤ 200 km/h | ≤ 250 km/h | ≤ 300 km/h | ≤ 350 km/h |
|---|---|---|---|---|---|
| Cant 160 mm, cant deficiency 100 mm, no tilting trains |
625 m | 1800 m | 2800 m | 4000 m | 5400 m |
| Cant 160 mm, cant deficiency 200 mm, with tilting trains |
450 m | 1300 m | 2000 m | no tilting trains planned for these speeds | |
See also
|
References
- ^ Guide to Railcars, showing the minimum radii that each freight car is able to negotiate
- ^ Canadian Light Rail Vehicle able to negotiate a 36 ft (10.973 m) radius curve
- ^ http://www.wis.co.uk/andy/16mm/minimumcurveradius.html
- ^ a b Jane's World Railways 1995-1996 p728
- ^ Railway Gazette International March, 2012, page 23
- ^ http://www.garrattmaker.com/history.html
- ^ Australian Railway History September 2008, p291.
|
||||||||||||||
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Post a question - any question - to the WikiAnswers community:
Copyrights:
Wikipedia on Answers.com
This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Minimum railway curve radius.
Read more