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Demodara Black Bridge and Loop railway engineering: 360-degree spiral elevation gain?

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K
Kenji Train•935 rep

How does the track alignment of the Demodara Loop permit broad-gauge trains to lose 100 feet of elevation by looping around a mountain spine and emerging beneath its own station?

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4 Answers from travellers

✓Accepted Answer

The Demodara Loop (completed in 1921 on the Badulla extension) is a masterwork of mountain railway civil engineering. To climb the steep terrain out of the Badulla valley without exceeding the maximum allowable broad-gauge grade (1 in 44), surveyors engineered a complete 360-degree spiral. The track winds around the exterior hillside, circles the circular hill summit where the station platform stands, passes through a cutting, crosses the Black Bridge (a curved steel-girder viaduct), and enters Tunnel No. 42, which burrows directly underneath the Demodara station platform itself.

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E
Eng Priyantha Bridges•1860 rep

Local folklore claims the colonial surveying engineer conceived the loop geometry after watching a local tea estate kangany re-tie his head turban in circular folds.

21
K
Kenji Train•935 rep

The tight curve radius (minimum 5 chains / 100 meters) demands continuous track-mounted mechanical grease lubricators to prevent flange screech and railhead wear.

17
R
Ranger Sisira Rock•1790 rep

Photographers stand on the high tea path overlooking the station to capture a train rounding the upper curve while its rear carriages emerge from the tunnel portal below.

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D
Dev Transit•895 rep

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