Cornwall Railway viaducts
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The Cornwall Railway viaducts were mostly built on stone piers but with spans of timber fans. This design was chosen by Isambard Kingdom Brunel in order to reduce the cost of their construction, but at the expense of high maintenance costs.
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[edit] History
The Cornwall Railway linked Plymouth with Falmouth. The section from Plymouth to Truro was opened on 4 May 1859, and the remainder to Falmouth on 24 August 1863. This was after Brunel's death and so was built under the supervision of R P Brereton.
The route crossed 45 rivers and deep valleys. Of these 42 were crossed by timber viaducts of various types. The remainder were the River Tamar at Saltash crossed on the Royal Albert Bridge, the River Fowey at Lostwithiel crossed by a low three-span viaduct (two spans being timber, the central one iron), and the river and canal at Par crossed on a five-arch low stone viaduct.
Replacement of the viaducts started in 1875 but led to a dispute between the Cornwall Railway and the Great Western Railway which leased the line. The lease precluded the conversion of the broad gauge line to standard gauge, and the Cornwall Railway refused to pay for the widening of the viaducts during rebuilding to accommodate a double line of standard gauge tracks (it had been built as a single-track line).
Following the amalgamation of the two companies on 1 July 1889 all the remaining viaducts were replaced, those between Saltash and St Germans being replaced by a deviation line, the remainder being either rebuilt in situ or having a replacement viaduct built immediately alongside. Because of this, many of Brunel's original piers still remain today.
[edit] Constructional features
Five distinct types of viaduct were built to suit local conditions at each site. P J Margary, a later Cornwall Railway engineer, classified them as classes A to E.
Class A: The majority of viaducts were constructed on stone piers that rose to about 34 feet below track level. From the tops of these radiated three fans of timber struts to support the beams beneath the track; one fan on each side and the third beneath the centre of the track. The struts radiated at around 55, 75, 105 and 125 degrees from horizontal (resulting in a \\// form), although there were some slight variations. This gave piers spaced at about 65 feet centres.
Class B: A stronger support was given to St Pinnock, Largin, and Ponsanooth viaducts by replacing the central set of fan struts with a pair. These joined the outer fans at the top of the pier and met each other at the top, giving a W form when viewed across the width of the piers.
Class C: The soft ground of the tidal valleys at Weston Mill, Forder, Wivelscombe, and Nottar required a lighter structure. This was achieved by dispensing with the stone piers and replacing them with vertical timber trestles built on top of timber piles driven into the mud. There were no fans supporting the track, instead timber trusses were built directly on top of the timber trestles.
Class D: Coombe (by Saltash) and Moorswater viaducts had only two fans on each pier - one on each side - but the bottoms of these were joined by laminated timber beams betwe
Class E: The shallowest valleys at Grove, Draw Wood, and Probus were crossed by simple trestles of three parallel fans with two struts each in a V shape.
[edit] Viaducts from Plymouth to St Germans
[edit] Stonehouse Pool
The only double track viaduct on the line, it was a Class A viaduct but with five fans of struts on each of the dwarf piers.
57 feet high, 321 feet long on 5 dwarf piers ; rebuilt with iron girders on brick piers in 1908. The girders have since been removed and a steel work of art has been erected in its place.
It was built on a curve in Plymouth between Five Fields Lane (now North Road West) and Stuart Road. The southern end marked the boundary between the Cornwall Railway and the joint station shared with the South Devon Railway. The land below the viaduct was the head of a tidal creek but is now drained and forms a park.
[edit] Keyham
A Class A viaduct north of Devonport tunnel.
90 feet high, 432 feet long on 6 piers; rebuilt using steel girders in 1900 which were again replaced in 1937.
[edit] Weston Mill
A Class C viaduct across Weston Mill Lake, a wide tidal inlet.
46 feet high, 1,200 feet long on 29 trestles; replaced by a steel structure in 1903.
A branch to the naval dockyard was opened at the south end of the viaduct on 20 June 1867. It is situated between the later stations at Keyham and St Budeaux.
[edit] Coombe by Saltash
A Class D viaduct immediately west of Saltash.
86 feet high, 603 feet long on 9 trestles; replaced by a stone viaduct on 19 October 1894.
Because it crossed a deep, muddy tidal inlet, Brunel constructed this viaduct on timber piles and used timber trestles instead of stone piers. These were made from four groups of four timber baulks, each group raking inwards towards the top of the trestle.
[edit] Forder
A Class C viaduct across the tidal Forder Lake.
67 feet high, 606 feet long on 16 trestles; demolished after the line was diverted to a more inland alignment on 19 May 1908.
[edit] Wivelscombe
A Class C viaduct across the tidal Wivelscombe Lake.
25 feet high, 198 feet long on 4 trestles consisting solely of two uprights each plus a cross brace. Demolished after the line was diverted to a more inland alignment on 19 May 1908.
[edit] Grove
A Class E viaduct 1 mile east of St Germans.
29 feet high, 114 feet long on two dwarf piers. The fans consisted of two raking struts on either side of the track, tied beneath the track by cross braces, and a central pair of struts which were joined at the top as an inverted V; from the side this gave a \|/ fan. It was demolished after the line was diverted to a more inland alignment on 19 May 1908.
A fatal accident occurred here just two days after the opening of the railway. On 6 May 1859 the engine of the 7.25 p.m. train from Plymouth was approaching St Germans when it left the rails, hit the parapet of the viaduct and fell into the mud below, landing upside down. Two of the coaches also ended up in the creek. The driver, fireman, and one guard were killed. A second guard, Richard Paddon, was given a reward of five pounds for his part in keeping the remainder of the train on the viaduct and helping to rescue the survivors.
[edit] Nottar
A Class C viaduct across the River Lynher 3/4 east of St Germans.
67 feet high, 921 feet long on 27 trestles; demolished after the line was diverted to a more inland alignment on 19 May 1908.
[edit] St Germans
A timber viaduct across the River Tiddy just east of St Germans railway station.
106 feet high, 945 feet long on 16 trestles. Piles were driven into the mud and trestles built on top from four groups of four timber baulks, each group raking inwards towards the top of the trestle. On top of this was a timber truss carrying the track. It was demolished after the line was diverted to a new alignment on 19 May 1908.
[edit] Viaducts from St Germans to Liskeard
[edit] Tresulgan
A Class A viaduct 3/4 mile east of Menheniot.
93 feet high, 525 feet long on 8 piers; replaced by a new stone viaduct on March 26, 1899.
[edit] Coldrennick
A Class A viaduct immediately east of Menheniot railway station.
138 feet high, 795 feet long on 16 piers. The piers were raised in brick and new iron girders replaced the timber on 23 January 1898. During the rebuilding work a serious accident caused the deaths of a dozen workmen. The piers were strengthened in 1933 by encasing them in stone.
[edit] Trevido
A Class A viaduct one mile west of Menheniot.
101 feet high, 486 feet long on 7 piers; replaced by a new stone viaduct on 14 September 1898.
[edit] Cartuther
A Class A viaduct 3/4 mile east of Liskeard.
89 feet high, 411 feet long on 6 piers; replaced by a new stone viaduct on 8 January 1882.
[edit] Bolitho
A Class A viaduct 1/4 mile east of Liskeard.
113 feet high, 546 feet long on 8 piers; rebuilt as a stone viaduct in 1882.
[edit] Liskeard
A Class A viaduct immediately east of Liskeard railway station.
150 feet high, 720 feet long on 11 piers; rebuilt by raising the brick piers and replacing the timber with iron girders in 1894. These girders were renewed in steel in 1929.
This is one of the two tallest viaducts in Cornwall. Since 25 February 1901 the Looe branch has passed beneath this viaduct.
[edit] Viaducts from Liskeard to Bodmin Road
[edit] Moorswater
A Class D viaduct a short distance west of Liskeard.
147 feet high, 954 feet long on 14 piers; replaced by a new stone viaduct with cast iron parapets on 25 February 1881.
In 1855 two of the piers then under construction collapsed. Brunel inspected them and rebuilt them the following year to his original design.
This is the largest of the conventional viaducts and is generally held to be the most attractive. The line that runs below this viaduct is the Liskeard and Looe Railway. To the south can be seen Coombe railway station while to the north is the remains of Moorswater yard, still used by cement trains. Beyond this the Liskeard and Caradon Railway used to rise up onto the hills to serve various granite quarries.
[edit] Westwood
A Class A viaduct 1 mile west of Doublebois railway station, the first of eight viaducts in the picturesque Glynn Valley.
88 feet high, 372 feet long on 5 piers; replaced by a new stone viaduct on 14 December 1879.
The quarry to the south of the railway provided stone for rebuilding many of the viaducts in Cornwall. On the other side of the line the River Loveny flows in from the north to form the River Fowey.
[edit] St Pinnock
A Class B viaduct in the Glynn Valley.
151 feet high, 633 feet long on 9 piers; rebuilt by raising the piers and replacing the timber with iron girders in 1882.
This is the tallest viaduct on the railway. The line was singled over this viaduct on 24 May 1964 to reduce the load on the structure. Beneath the viaduct is the Trago Mills out-of-town shopping complex.
[edit] Largin
A Class B viaduct in the Glynn Valley.
130 feet high, 567 feet long on 8 piers; rebuilt by raising the piers and replacing the timber with iron girders on 16 January 1886.
The line was singled over this viaduct on 24 May 1964 to reduce the load on the structure.
[edit] West Largin
A Class A viaduct in the Glynn Valley.
75 feet high, 315 feet long on 5 piers; replaced by a new stone viaduct on 26 September 1875.
[edit] Draw Wood
A Class E viaduct in the Glynn Valley.
42 feet high, 681 feet long on 17 dwarf piers; replaced by an embankment and stone retaining wall in 1875.
[edit] Derrycombe
A Class A viaduct. 77 feet high, 369 feet long on 5 piers; replaced by a new stone viaduct on May 8, 1881.
[edit] Clinnick
A Class A viaduct in the Glynn Valley.
74 feet high, 330 feet long on 5 piers; replaced by a new stone viaduct with an iron parapet on 16 March 1879.
[edit] Penadlake
A Class E viaduct about 13/4 miles east of Bodmin Road railway station, this is the last viaduct crossed in the descent of the Glynn Valley.
42 feet high, 426 feet long on 10 dwarf piers; replaced by a new stone viaduct on 7 October 1877.
[edit] Viaducts from Lostwithiel to Truro
[edit] Milltown
A Class A viaduct one mile west of Lostwithiel.
75 feet high, 501 feet long on 7 piers; replaced by a new stone viaduct in 1894.
[edit] St Austell
A Class A viaduct across the Trenance valley 1/2 mile west of St Austell railway station.
115 feet high, 720 feet long on 10 piers; replaced by a new stone viaduct in 1899.
There was a siding located west of the viaduct. In the early years trains from St Austell had to push wagons over the tall, curving viaduct to shunt this siding. The Great Western Railway's instructions stated that: "Trucks may be pushed from St. Austell to the Siding, but when this is done the speed of the Train between the two places must not exceed 8 miles an hour, and the head Guard must ride on the leading vehicle, unless it be a bonnet end one, in which case he must ride in the first low sided vehicle from it, to keep a good look out, and be prepared to give a signal to the Driver either by Day or Night, as may be required."
[edit] Gover
A Class A viaduct 11/4 miles west of St Austell.
95 feet high, 690 feet long on 10 piers; replaced by a new stone viaduct in 1898.
[edit] Coombe St Stephens
A Class A viaduct two miles east of Grampound Road.
70 feet high, 738 feet long on 11 piers; replaced by a new stone viaduct on 11 July 1886.
[edit] Fal
A Class A viaduct 1½ miles east of Grampound Road.
90 feet high, 570 feet long on 8 piers; replaced by a new stone viaduct on 24 August 1884.
It is hard to believe that the tiny river beneath the viaduct is indeed the same mighty River Fal that reaches the sea at Falmouth.
[edit] Probus
A Class E viaduct 2 miles west of Grampound Road.
43 feet high, 435 feet long on 11 dwarf piers; replaced by an embankment in 1871.
Probus and Ladock Halt was opened a quarter of a mile west of the viaduct site on 1 February 1908.
[edit] Tregarne
A Class A viaduct 31/2 miles west of Grampound Road. 83 feet high, 606 feet long on 9 piers; replaced by a new stone viaduct on 1 September 1901.
[edit] Tregeagle
A Class A viaduct 6 miles west of Grampound Road and 1/2 mile east of Polperro Tunnel.
69 feet high, 315 feet long on 4 piers; replaced by a new stone viaduct on 2 February 1902.
[edit] Truro
A Class A viaduct 1 mile east of Truro railway station.
92 feet high, 1,329 feet long on 20 piers; replaced by a new stone viaduct on 14 February 1904.
This is the longest conventional viaduct on the line. It gives travellers a bird'-eye view of the city and cathedral below, and the Truro River, a tributary to the River Fal, in the distance.
[edit] Carvedras
A Class A viaduct 1/4 mile east of Truro railway station.
86 feet high, 969 feet long on 15 piers; replaced by a new stone viaduct on 17 August 1902.
[edit] Viaducts from Truro to Falmouth
[edit] Penwithers
A Class A viaduct 1/4 mile west of the junction between the Cornwall Railway to Falmouth and the West Cornwall Railway to Penzance.
90 feet high, 813 feet long on 12 piers; rebuilt as an embankment in 1926.
[edit] Ringwell
A Class A viaduct 1 mile north of Perranwell.
70 feet high, 366 feet long on 5 piers; rebuilt as an embankment in 1933.
[edit] Carnon
A Class A viaduct 1/2 mile north of Perranwell railway station.
96 feet high, 756 feet long on 11 piers; replaced by a new stone viaduct on 13 August 1933.
The soft nature of valley floor meant that some piers had to have a foundation built for them by sinking a temporary caisson and removing the mud within it.
This viaduct crossed Restronguet Creek and the Redruth and Chasewater Railway near its Devoran terminus. This disused railway line now forms part of the Mineral Tramways Trail.
[edit] Perran
A Class A viaduct 1 mile south of Perranwell railway station.
56 feet high, 339 feet long on 5 piers; replaced by a new stone viaduct on 24 April 1927.
[edit] Ponsanooth
A Class B viaduct across the River Kennall 2 miles north of Penryn railway station.
139 feet high, 645 feet long on 9 piers; replaced by a new stone viaduct on 7 September 1930.
This is the tallest viaduct west of Truro.
[edit] Pascoe
A Class A viaduct 13/4 miles north of Penryn railway station.
70 feet high, 390 feet long on 6 piers; replaced by an embankment in 1923.
[edit] Penryn
A Class A viaduct 1/4 mile north of Penryn railway station.
63 feet high, 342 feet long on 5 piers; replaced by an embankment in 1923.
[edit] Collegewood
A Class A viaduct 1/4 mile south of Penryn railway station.
100 feet high, 954 feet long on 14 piers; replaced by a new stone viaduct on 22 July 1934.
This was the longest viaduct west of Truro and the last timber viaduct to be replaced in Cornwall.
[edit] See also
List of railway viaducts in the United Kingdom
[edit] Further reading
- The records of the Cornwall Railway can be consulted at The National Archives in Kew.
- Brunel's Cornish Viaducts, John Binding, Atlantic Transport Publishing/Historical Model Railway Society, 1993. ISBN 0-906899-56-7
