South Devon Banks
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The South Devon Banks are a series of steep inclines on the ex-GWR railway line linking Exeter and Plymouth in Devon, England. These two cities are separated by the rocky uplands of Dartmoor forcing the early railway surveyors to propose that the line skirt the difficult terrain of the comparatively sparsely populated moorland. Isambard Kingdom Brunel, in surveying the South Devon Railway, opted to push a line along a coastal strip between the Exe and Teign valleys, and then to climb the southern outliers of Dartmoor making for the head of the Plym estuary. From Newton Abbot, the line climbs Dainton Bank, and from Totnes it climbs Rattery Bank, reaches a peak at Wrangaton summit, and then descends Hemerdon Bank to reach Plymouth. These three are collectively known as the South Devon Banks.
Dainton Bank
The third steepest main line bank on the British mainland, with 2 miles varying between 1 in 36 and 1 in 57. Leaving Newton Abbot station, the line is near level until Aller Junction, where the line to Torbay diverges to the left. The climb proper begins at Stoneycombe, where there was a signal box and quarry siding, and continues through Dainton tunnel to Dainton signal box, a distance of 2 miles and 17 chains (3.56 km).
Rattery Bank
The seventh steepest main line bank on the British mainland, with a constant 4+1⁄4 miles (6.8 km) initially between 1 in 45 and 1 in 70 before easing to 1 in 90 and then increasing to 1 in 65. Leaving Totnes station, the line immediately climbs past the site of Tigley signal box and on to the site of Rattery signal box, a distance on 4 miles and 50 chains (7.44 km).
Hemerdon Bank
The fourth steepest main line bank on the British mainland, with a constant 1 in 42 for 2+1⁄2 miles. The climb begins at Plympton and climbs all the way to Hemerdon signal box, a distance of 2 miles and 50 chains (4.22 km).
Effects on operations
From an early date, trains were constrained in weight, and therefore in length, by the need to climb the steep gradients of South Devon. Express trains were further constrained by the need to achieve fast times between Exeter and Plymouth. In
The inaugural Cornish Riviera Limited built on the royal specials of the previous two years by running through to Plymouth with a City class engine; the train being limited to 6 coaches. However, greater demand for seats meant that by 1911, despite the introduction of the 4-6-0 Saint class, a pilot engine was required. In this process a pilot engine, usually placed behind the train engine per standard GWR practice and therefore requiring an awkward shunting manoeuvre, would be added at Newton Abbot on down trains, and both engines haul the train through to Plymouth where it was usual to change engines before entering Cornwall. In the up direction, the change of engines at Plymouth would see two engines take over the train, the inside engine being removed during the stop at Newton Abbot. From their introduction, the King class had a monopoly on the fastest workings through Devon, but it was still usual to add a pilot for heavy loads; Castle, Hall and Grange classes were common, and even a double-headed King could be encountered.
The advent of the
With the advent of the
In more recent times, HSTs have been permitted to run through unassisted on one operational power car only, however normal practice is to omit the Totnes stop in order to achieve a run at the incline (Rattery Bank in the westbound direction or Dainton Bank in the eastbound direction). Much of the reason for this change in policy is the relative non-availability of standby diesel locomotives on the modern railway, where minimal freight traffic operates in the south west of England.
Test track
Many tests and comparisons carried out by the GWR and BR(WR) have involved traversing the South Devon Banks. During the locomotive exchanges of 1948, Paddington to Plymouth turns were worked by
In June 1950, Brown-Boveri designed Gas Turbine No. 18000 carried out a series of test runs with a dynamometer car, starting from Plymouth and climbing Hemerdon bank. During these tests, the locomotive failed to restart a 350-long-ton (360 t) train from a standing start on the bank itself, and achieved a speed of 10 mph (16 km/h) on cresting the bank with a 400-long-ton (410 t) load, having been travelling at 50 mph (80 km/h) past Plympton before starting the climb. The Metropolitan Vickers Gas Turbine No. 18100 also carried out a series of test runs in 1951 including climbing all of the South Devon Banks. Performance up Dainton and Rattery was deemed satisfactory, but four subsequent test runs were carried out ascending Hemerdon bank. One was aborted, but in the other three 18100 hauled 14, 17 and 18 coaches respectively, the latter exceeding 600 long tons (610 t) and achieving a minimum of 15 mph (24 km/h) on the bank when recorded as passing
References
- Body, Ian (1978). Modern Rail Facts and Information. Bristol: Avon-Anglia Publications. ISBN 0-905466-18-7.
- Maggs, Colin (1985). Rail Centres: Exeter. Nottingham: Booklaw Publications. ISBN 1-901945-15-4.
- Nock, O S (1979). The Limited. London: George Allen & Unwin. ISBN 0-04-385072-3.
- Oakley, Michael (4 January 1981). Diesel Enthusiast's Pocket Guide 8: Wessex and West Country. Newton Abbot: D Bradford Barton. ISBN 0-85153-409-0.
- Robertson, Kevin (1989). The Great Western Railway Gas Turbines 'A myth exposed'. Stroud: Sutton Publishing. ISBN 0-86299-541-8.
- Webster, Neil (1982). Loco Hauled Travel 1982. Sheffield: Platform 5. ISBN 0-906579-22-8.