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Railway Structures
Meldon Viaduct


 
Meldon Viaduct
Meldon Viaduct, photographed on 6th July 2008.

photograph by Gregory Beecroft

Meldon Viaduct is the outstanding survivor of the small number of metal trestle viaducts built in Britain. It is located west of Okehampton, on the London & South Western Railway's line to Tavistock and Plymouth. The viaduct crosses the valley of the West Okement River on the northern slope of Dartmoor, about 950 feet above sea level. The railway and viaduct were originally built for a single-track and were completed in 1874. The viaduct was widened to take a second track in 1879, so there are separate trestles for each side of the viaduct. The photographs show the 1874 structure to the right and the 1879 one to the left.

The viaduct has six spans of 90 feet and the deck is 144 feet above the river. The highest trestle is 120 feet tall. The railway crossed the viaduct on a 30 chains radius curve and a gradient of 1 in 77, rising to a summit a short distance to the west.

Meldon Viaduct.

photograph by Gregory Beecroft

Meldon Viaduct
 
Meldon Viaduct Meldon Viaduct.

photograph by Gregory Beecroft

Both the original structure and the widening comprise wrought iron trestles supporting a pair of wrought iron Warren truss girders set five feet apart. However, the 1879 viaduct was not a repeat of the 1874 one and there are numerous differences in detail between them. The 1879 trestles have more robust bracing; additional bracing was added to the 1874 trestles during the 1950s. The lower members of the 1879 trusses have flanges; those of the 1874 trusses do not. The viaduct had a timber deck, with longitudinal timbers to carry the rails.

The main line closed between Meldon and Bere Alston in 1968, but a headshunt from Meldon Quarry extended onto the viaduct thereafter. With the track removed, the viaduct was extensively renovated and repainted in 1996. A new timber deck was installed, allowing public access over the structure.

Much of the old paint on the viaduct was lead based. When the viaduct was repainted in 1996 the surface had to be prepared very carefully, without contaminating the river and surrounding area. All grit blasting of the ironwork took place inside sheeting, to contain the dust. Only a limited area could be sheeted at any one time, in order to avoid excessive wind-loading on the viaduct.

photograph by Gregory Beecroft

Meldon Viaduct
 
Meldon Viaduct A scaffold deck was erected to allow easy access to the trusses. The metalwork here has been prepared for painting.

photograph by Gregory Beecroft

 
The old deck was entirely removed, showing the layout of the beams on which it was supported. Grit blasting is under way in the enclosure at the end of the viaduct.

photograph by Gregory Beecroft

Meldon Viaduct
 
Meldon Viaduct When the new timber deck had been laid the viaduct looked a bit like a seaside pier that had become lost inland! Subsequently railings were erected to keep members of the public away from the edge of the viaduct and a non-slip surface was laid.

photograph by Gregory Beecroft

The viaduct is owned by the Meldon Viaduct Company, a non-profit making company limited by guarantee and with charitable status.

All photographs are copyright

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This page was last updated 9 February 2010

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