Spiral (railway)

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For the engineering term applying to railway track geometry, see Track transition curve.
Tehachapi Loop, on the Union Pacific Railroad, California, U.S.A., from the air.

A spiral (sometimes called a spiral loop or just loop) is a technique employed by railways to ascend steep hills.

A railway spiral rises on a steady curve until it has completed a loop, passing over itself as it gains height, allowing the railway to gain vertical elevation in a relatively short horizontal distance. It is an alternative to a zig-zag, and avoids the need for the trains to stop and reverse direction while ascending. If the train is of sufficient length, it is possible to view the train looping onto itself.

A spiral loop should not be confused with the transition spiral or spiral easement used to provide a transition from a tangent into a horizontal circular curve. Spiral easement is used to avoid abrupt changes in the sideward acceleration experienced by a railroad vehicle and the passengers in the vehicle approaching the horizontal circular curve and to prevent abrupt forces and discomfort. These curves are also used in highway engineering.

A similar feature to railway spirals in road design is the pigtail bridge.

Calculations

On a railway climbing at a gradient of 1 in 40 (2.5%, or 25 m per km) a 360-degree spiral at 350 m radius will add 2200 m to the forward journey and 55 m to the vertical climb. Unless the topography has a suitably shaped hill, the spiral is likely to include a tunnel, increasing construction costs and creating problems if steam locomotives are employed. If a convenient side valley is available, then a horseshoe curve may be possible.

The spiral needs to climb about 6 m in order to bridge itself. With steam locomotives and to a lesser extent with diesel locomotives, the gradient in any long tunnel(s) should be less than the ruling grade to avoid problems with fumes and dampness causing the driving wheels to slip.

List of spirals

This list is incomplete; you can help by expanding it.

Argentina

Australia

  • Bethungra Spiral two very short tunnels, uphill track in spiral at 1 in 66 gradient, downhill track plain at 1 in 40 gradient
  • Cougal Spiral one short and one long tunnel, single track

Austria

Bolivia

  • Spiral south of Zudáñez on closed railway line starting at Taburoco

Bulgaria

Canada

Chile

  • Trans-Andine Railway connecting Chile and Argentina

[3]

People's Republic of China

  • Yangjiawan – Qinling Tunnel
  • On the Chengdu-Kunming Railway, there is a spiral north of Heijing Town

Croatia

France

Germany

India

Loop (Agony Point) on the DHR, India

Iran

  • Numerous spirals through very mountainous regions, mostly entirely in tunnel and single track, e.g. the Three Golden Lines.

Ireland

  • The St. James's Gate Brewery, Dublin, Ireland had an internal 1 ft 10 in (559 mm) gauge railway with a loop in a tunnel to gain height between buildings[7]

Italy

Japan

Okoba spiral and Zig zag in Hisatsu Line, Japan

Kenya

  • Kenya-Uganda four spirals on the Kenya to Uganda line.

Mazeras Spiral near Mombasa, at: -3.995257° 39.546742° (map)
Spiral near Makutano station, at: -0.043457° 35.641461°
Spiral near Equator station, at: -0.007183° 35.551033°

South Korea

Geumdae 2nd Tunnel in Jungang Line, South Korea
  • Geumdae 2nd Tunnel – between Geumgyo station and Chiak station on Jungang Line – one loop, single track. New double track tunnel is under construction to replace loop tunnel.
  • Daegang Tunnel – between Danseong station and Jungnyeong station on the Jungang Line – one loop, single track.
  • Hambaek 1st Tunnel – between Hambaek station and Jodong station on the Hambaek Line – one loop, single track.
  • Solan Tunnel – between East Baeksan station and Dogye station on the Yeongdong Line – one loop, single track but double track is installed on the middle of the tunnel; for both trains crossing each other. It will be opened in 2009.

Madagascar

Myanmar

Spiral in Thazi – Taunggyi line, Myanmar
  • Two spirals on the Burmah Mines Railway[9]
  • One spiral close to Schwenyaung on the Thazi-Schwenyuang line

New Zealand

Norway

Russia

Serbia

  • Šarganska osmica in Western Serbia, from Mokra Gora to Šargan Vitasi.

Slovakia

South Africa

Spain

  • Cargol Tunnel on the Ripoll - La Tour de Carol (France) line
  • El Lazo Tunnel on the Palencia - La Coruña line

Sri Lanka

  • Demodera

Switzerland

Brusio spiral viaduct on the RhB Berninabahn
Toua spiral tunnel on the RhB Albulabahn
  • Gotthardbahn has five spirals (and two turns), entirely in tunnel, double track, standard gauge
  • RhB Albulabahn has four spirals (in tunnels), single track, metre gauge
  • RhB Berninabahn has an open spiral mainly on the Brusio spiral viaduct (near Brusio), single track, metre gauge
  • Former Furka-Oberalp-Bahn, now Dampfbahn Furka-Bergstrecke heritage railway, has one spiral tunnel, single track, cog rail, metre gauge, catenary removed
  • Former Furka-Oberalp-Bahn, now Matterhorn-Gotthard-Bahn, between Grengiols and Lax, single track, metre gauge, cog rail, entirely in tunnel

Taiwan

Alishan Forest Railway

Uganda

See Kenya above.

United Kingdom

The bridge on the spiral loop at Dduallt on the Ffestiniog Railway, Wales.

United States

1903 view of Riflesight Notch loop, near Rollins Pass in Colorado
  • California, Williams Loop
  • California, Tehachapi Loop
  • California, Roaring Camp Loop – 3 ft (914 mm) gauge (abandoned after fire, trestles still partly standing, to be rebuilt)
  • Tennessee, Hiwassee Loop, in which the track wraps around a hill twice and crosses over itself on an 80-foot-tall (24 m) trestle.
  • Colorado, Georgetown Loop
  • Colorado, Riflesight Notch Loop on the Moffat Route, west of Rollins Pass (line abandoned, replaced by Moffat Tunnel, trestle still partly standing)
  • Colorado, Ophir Loop – Rio Grande Southern Railroad – 3 ft (914 mm) gauge (abandoned)
  • Dunderberg Spiral Railway (never completed)
  • Eureka, Utah – the "Golden Circle".

Spirals are not generally needed on tramways (street running or reserved track) or light rail lines because trams traditionally have all wheels powered, giving the ability to climb much steeper direct gradients than railways.

Roads

Roads sometimes use a spiral to gain height in a confined space, cf. pigtail bridge.

See also

References

  1. ↑ "FEATS IN RAILWAY ENGINEERING.". The Darling Downs Gazette and General Advertiser (Toowoomba, Qld. : 1858–1880) (Toowoomba, Qld.: National Library of Australia). 25 August 1868. p. 4. Retrieved 7 January 2013. 
  2. ↑ Trinity Loop
  3. ↑ "TRANS-ANDINE RAILWAY.". The West Australian (Perth, WA : 1879–1954) (Perth, WA: National Library of Australia). 30 November 1909. p. 5. Retrieved 23 March 2013. 
  4. ↑
  5. ↑ fr:Ligne transcévenole
  6. ↑ irfca.org
  7. ↑
  8. ↑ "THE SIMPLON TUNNEL.". The Capricornian (Rockhampton, Qld : 1875–1929) (Rockhampton, Qld: National Library of Australia). 15 October 1904. p. 21. Retrieved 19 March 2013. 
  9. ↑
  10. ↑ Can be clearly seen on Google Maps
  11. ↑ Childers, Erskine (1900). In the Ranks of the C. I. V. London: Smith, Elder. p. 86. OCLC 16633317. 

External links

Railway track layouts
Running lines
Rail sidings
Junctions
Stations
Hillclimbing
Track geometry
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