Penydarren
Penydarren was Richard Trevithick's 1804 high-pressure steam locomotive, the world's first working steam railway locomotive. Built at the Penydarren Ironworks at Merthyr Tydfil for Samuel Homfray, the engine demonstrated for the first time that steam-hauled rail transport was practical and inaugurated the railway age.
The design used a single horizontal cylinder driving a single crankshaft through connecting rods, with a substantial flywheel to carry the engine through the dead centres. Steam was generated in a single-flue cylindrical boiler at the then-controversial high pressure of approximately 40 psi, Trevithick's "strong steam" approach. The whole engine was approximately 26 ft long and weighed about 5 tons.
On 21 February 1804 the engine famously hauled 10 tons of iron, five wagons, and 70 men nearly 10 miles from Penydarren down the Merthyr Tramroad to Abercynon, winning Homfray a 500-guinea wager with rival ironmaster Anthony Hill, and demonstrating that a steam locomotive could haul a useful load over rails. The run took approximately 3 hours 35 minutes, an average of around 5 mph including stops to refill the water tank.
The engine repeatedly broke the cast-iron tramroad plates under its 5-ton weight and was withdrawn from rail service after only three runs. The Merthyr Tramroad had been built for horse haulage with relatively light cast-iron L-section plates that simply could not withstand the engine's weight. Penydarren was converted to a stationary engine and used at the ironworks for several years before being scrapped around 1810. The principal lesson, that contemporary cast-iron rails were too weak for steam locomotive weights, drove the rapid improvement in rail construction over the following two decades and shaped all subsequent locomotive development.
No original component survives. A working replica was constructed in 1981 for the bicentennial of Trevithick's birth and is currently a static exhibit at the National Waterfront Museum at Swansea, occasionally steamed for public demonstrations.
Design and development
By 1803 Richard Trevithick had been developing high-pressure steam engines in Cornwall for several years, most notably the 1801 "Puffing Devil" road carriage that demonstrated steam road locomotion at Camborne. Trevithick had moved to South Wales in 1803 to work for Samuel Homfray's Penydarren Ironworks at Merthyr Tydfil, and Homfray became enthusiastic about Trevithick's ideas for a railway locomotive.
The Penydarren engine was Trevithick's answer. The design used a single horizontal cylinder driving a single crankshaft through connecting rods, with a flywheel to carry the engine through the dead centres. Steam was generated in a single-flue cylindrical boiler with internal firebox, the same general arrangement as Trevithick's contemporary stationary engines, scaled and oriented for rail use. The boiler operated at the then-controversial high pressure of approximately 40 psi.
The engine was built at the Penydarren Ironworks during late 1803 and completed in February 1804, partly to help Homfray win a 500-guinea wager with rival ironmaster Anthony Hill. Hill bet that no engine could haul 10 tons of iron from Penydarren to Abercynon over the Merthyr Tramroad. On 21 February 1804 Trevithick's engine made the run successfully, hauling 10 tons of iron, five wagons, and approximately 70 spectators who had climbed aboard, completing the 9.75-mile run in approximately 3 hours 35 minutes (an average of about 5 mph). Homfray won his wager.
Service and withdrawals
The engine made approximately three full runs over the Merthyr Tramroad before its weight repeatedly broke the cast-iron tramroad plates. The Merthyr Tramroad had been built for horse haulage with relatively light cast-iron L-section plates, the engine's 5-ton weight (significantly more than any horse-drawn load) was simply too much for the existing infrastructure. The cost of repairing the broken rails outweighed the savings from steam haulage, and the engine was removed from the tramroad after only a few weeks.
The engine itself was not abandoned, it was converted to a stationary engine and used at the ironworks for various purposes for several more years, eventually being scrapped in around 1810. The Merthyr Tramroad continued in horse haulage for several decades. Trevithick himself moved on to other projects, the 1805 Whinfield engine at Wylam, and the 1808 "Catch Me Who Can" London demonstration.
Despite its short service life, Penydarren's significance was profound. The engine demonstrated for the first time that a steam locomotive could haul a useful load over rails, establishing the principle that all subsequent railway development would build upon. The principal lesson, that contemporary cast-iron rails were too weak for steam locomotive weights, drove the rapid improvement in rail construction over the following two decades.
Identification features
Outwardly the engine bore little resemblance to later steam locomotives. The single horizontal cylinder, the substantial flywheel (approximately 8 feet in diameter, necessary to carry the engine through the dead centres of the single crank), the tall vertical chimney, and the open footplate were the principal external features. The whole engine was approximately 26 ft long including the tender; the two pairs of wheels were unflanged (running on the flanged rails of the L-shaped tramroad plates). The engine's weight was approximately 5 tons, substantial for the cast-iron rails of the period, which were the principal limitation.
Numbers and names
None (single prototype)
Notable locomotives
- Original Penydarren locomotive, first steam railway journey (21 February 1804)
Allocations and regions
- Penydarren Ironworks, Merthyr Tydfil (1804)