Pont-y-Cafnau
Encyclopedia
The Pont-y-Cafnau sometimes written Pont y Cafnau or Pontycafnau, is a 14.2 metres (46.6 ft) long iron
truss
bridge over the River Taff
in Merthyr Tydfil
, Wales
. The bridge was designed by Watkin George and built in 1793 for his employer, the Cyfarthfa Ironworks
, to support both a tramway and an aqueduct
to carry limestone and water into the works. A Grade II* listed building and Scheduled Ancient Monument
, the Pont-y-Cafnau is the world's earliest surviving iron railway bridge.
by the early 19th century. In 1771, the works obtained the right to quarry limestone
from the Gurnos
Quarry for use in the works' blast furnaces, and a tramway was built between 1792 and 1793 to carry the limestone from the quarry into the plant. Pont-y-Cafnau is situated shortly downstream of the confluence of the Taff Fawr and the Taff Fechan to form the Taff. A weir
had previously been built upstream of the plant on each river, and leat
s were built to convey water into the works. The leat from the Taff Fawr was conveyed in a cast iron elevated aqueduct
which ran along the north bank and crossed the Taff Fechan before crossing the Taff at Pont-y-Cafnau and entering the works to power a 50 foot cast iron water wheel known as Aeolus. The leat from Taff Fechan was at ground level and again crossed the Taff at Pont-y-Cafnau. This supplied water to the Cyfarthfa brick works. The three levels of Pont-y-Cafnau thus carried the elevated Taff Fawr leat, the tramway and Taff Fechan leat across the Taff River. The bridge was built between January and June 1793, replacing a previous wooden structure, and is the world's oldest known iron railway bridge. The elevated trough carrying the Taff Fawr leat was removed by 1850, having been replaced by a leat along the south bank of that river.
A-frame
trusses supporting a rectangular 2-foot by 6-foot-2-inch cast iron trough. This lower trough carried the Taff Fechan leat and acts as a girder
supporting the plates acting as the railway sleepers
, into which the rail chairs are integrally cast. Wooden uprights were attached to the iron risers that passed through the apex of each of the A-frames and these supported the upper trough carrying the Taff Fawr leat. Reflecting its designer's roots in carpentry, the members composing the trusses are joined by dovetail
and mortise and tenon
joints commonly used in wooden structures.
.
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
truss
Truss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...
bridge over the River Taff
River Taff
The River Taff is a large river in Wales. It rises as two rivers in the Brecon Beacons — the Taf Fechan and the Taf Fawr — before joining to form the Taff north of Merthyr Tydfil...
in Merthyr Tydfil
Merthyr Tydfil
Merthyr Tydfil is a town in Wales, with a population of about 30,000. Although once the largest town in Wales, it is now ranked as the 15th largest urban area in Wales. It also gives its name to a county borough, which has a population of around 55,000. It is located in the historic county of...
, Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. The bridge was designed by Watkin George and built in 1793 for his employer, the Cyfarthfa Ironworks
Cyfarthfa Ironworks
The Cyfarthfa Ironworks was a major 18th century and 19th century ironworks located in Cyfarthfa, on the north-western edge of Merthyr Tydfil, in South Wales.-The beginning:...
, to support both a tramway and an aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....
to carry limestone and water into the works. A Grade II* listed building and Scheduled Ancient Monument
Scheduled Ancient Monument
In the United Kingdom, a scheduled monument is a 'nationally important' archaeological site or historic building, given protection against unauthorized change. The various pieces of legislation used for legally protecting heritage assets from damage and destruction are grouped under the term...
, the Pont-y-Cafnau is the world's earliest surviving iron railway bridge.
History
The Cyfarthfa Ironworks were founded in 1765 and grew to the world's largest ironworksIronworks
An ironworks or iron works is a building or site where iron is smelted and where heavy iron and/or steel products are made. The term is both singular and plural, i.e...
by the early 19th century. In 1771, the works obtained the right to quarry limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
from the Gurnos
Gurnos
Gurnos is a community of Merthyr Tydfil in Wales, United Kingdom. It consists principally of the Gurnos Estate, a large housing estate established by Merthyr Tydfil Council in the early 1950s and expanded over many years...
Quarry for use in the works' blast furnaces, and a tramway was built between 1792 and 1793 to carry the limestone from the quarry into the plant. Pont-y-Cafnau is situated shortly downstream of the confluence of the Taff Fawr and the Taff Fechan to form the Taff. A weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...
had previously been built upstream of the plant on each river, and leat
Leat
A leat is the name, common in the south and west of England and in Wales, for an artificial watercourse or aqueduct dug into the ground, especially one supplying water to a watermill or its mill pond...
s were built to convey water into the works. The leat from the Taff Fawr was conveyed in a cast iron elevated aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....
which ran along the north bank and crossed the Taff Fechan before crossing the Taff at Pont-y-Cafnau and entering the works to power a 50 foot cast iron water wheel known as Aeolus. The leat from Taff Fechan was at ground level and again crossed the Taff at Pont-y-Cafnau. This supplied water to the Cyfarthfa brick works. The three levels of Pont-y-Cafnau thus carried the elevated Taff Fawr leat, the tramway and Taff Fechan leat across the Taff River. The bridge was built between January and June 1793, replacing a previous wooden structure, and is the world's oldest known iron railway bridge. The elevated trough carrying the Taff Fawr leat was removed by 1850, having been replaced by a leat along the south bank of that river.
Design
The present bridge was designed by Watkin George. George had been trained as a carpenter, but in 1792 became the chief engineer of the ironworks and a partner in the business. The bridge is composed of two cast ironCast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
A-frame
King post
A king post is a central vertical supporting post used in architectural, bridge, or aircraft design applications.-Architecture:...
trusses supporting a rectangular 2-foot by 6-foot-2-inch cast iron trough. This lower trough carried the Taff Fechan leat and acts as a girder
Girder
A girder is a support beam used in construction. Girders often have an I-beam cross section for strength, but may also have a box shape, Z shape or other forms. Girder is the term used to denote the main horizontal support of a structure which supports smaller beams...
supporting the plates acting as the railway sleepers
Railroad tie
A railroad tie/railway tie , or railway sleeper is a rectangular item used to support the rails in railroad tracks...
, into which the rail chairs are integrally cast. Wooden uprights were attached to the iron risers that passed through the apex of each of the A-frames and these supported the upper trough carrying the Taff Fawr leat. Reflecting its designer's roots in carpentry, the members composing the trusses are joined by dovetail
Dovetail
Dovetail may refer to:* The dovetail joint used in woodworking* The dovetail or "riffle" method of shuffling playing cards* German equatorial mount, or dovetail plate, used to fix a telescope to its mount...
and mortise and tenon
Mortise and tenon
The mortise and tenon joint has been used for thousands of years by woodworkers around the world to join pieces of wood, mainly when the adjoining pieces connect at an angle of 90°. In its basic form it is both simple and strong. Although there are many joint variations, the basic mortise and tenon...
joints commonly used in wooden structures.
Heritage
On August 22, 1975, the bridge was listed as a Grade II* listed building (reference number 11408). It is also listed as a Scheduled Ancient Monument (reference number GM424). It has been refurbished by the local authority and is used as a footbridgeFootbridge
A footbridge or pedestrian bridge is a bridge designed for pedestrians and in some cases cyclists, animal traffic and horse riders, rather than vehicular traffic. Footbridges complement the landscape and can be used decoratively to visually link two distinct areas or to signal a transaction...
.