Wylam Dilly
Wylam Dilly is the sister engine to Puffing Billy and one of the two oldest surviving steam locomotives in the world. Built at Wylam Colliery in approximately 1815 to William Hedley's design (with Jonathan Forster and Timothy Hackworth), Wylam Dilly was effectively identical to Puffing Billy, both engines using the same general arrangement and working the Wylam Waggonway from Wylam Colliery to the staiths at Lemington-on-Tyne.
The design used twin vertical cylinders driving the wheels through cross-beams in the "grasshopper" arrangement and a cylindrical boiler at approximately 50 psi. The name "Dilly" was a Tyneside colliery slang term for a wagon or train of wagons. The engine was modified through its service life in parallel with Puffing Billy: 0-6-0 from approximately 1815 to spread weight on the wooden tramway, then back to 0-4-0 around 1830 after the line was relaid with stronger iron rails.
Wylam Dilly worked the Wylam Waggonway from 1815 to 1862, nearly 50 years' continuous service, the same period that took British railway technology from the Trevithick era through to the early Victorian railway boom. The engine was retired in 1862 alongside Puffing Billy.
Wylam Dilly is currently on permanent static display at the National Museum of Scotland, Edinburgh, preserved since 1862. The engine is in its later 0-4-0 form (the post-1830 configuration) and shows the wear of its 50-year working life. Together with Puffing Billy at the Science Museum, London, Wylam Dilly is one of the two oldest surviving steam locomotives in the world.
Design and development
Following the success of Puffing Billy in 1813–1814 at Wylam Colliery, William Hedley and his team built a second engine to the same design to expand the colliery's steam-haulage capacity. The second engine, soon known as "Wylam Dilly", was completed in approximately 1815, the exact date is not certain because of the fragmentary colliery records of the period.
The design was effectively identical to Puffing Billy. Two vertical cylinders driving the wheels through cross-beams and gears, a cylindrical boiler at approximately 50 psi, and the same general arrangement. The Wylam Waggonway had been relaid with cast-iron edge rails for Puffing Billy's introduction; Wylam Dilly worked alongside Puffing Billy on the same line.
Service and withdrawals
Wylam Dilly worked the Wylam Waggonway alongside Puffing Billy from 1815 onwards. The two engines were a successful pairing, between them they handled the colliery's coal traffic from 1815 through to 1862, when both were retired after nearly 50 years' service.
Wylam Dilly was modified through its service life in parallel with Puffing Billy: 0-6-0 from approximately 1815 to spread weight on the wooden tramway, then back to 0-4-0 around 1830 after the line was relaid with stronger iron rails. The engine's ability to give nearly 50 years of continuous colliery service, the same period that took British railway technology from the Trevithick era through to the early Victorian railway boom, was an extraordinary achievement.
Wylam Colliery retired the engine in 1862 alongside Puffing Billy. The Stephenson family's patriotic interest in the engine led to its preservation in Scotland rather than alongside Puffing Billy at the South Kensington Museum.
Identification features
Externally similar to Puffing Billy, substantial cylindrical boiler with twin vertical cylinders mounted on either side, driving the wheels through cross-beams (the "grasshopper" arrangement) and gears. The two engines are easily mistaken for each other in photographs. The name "Dilly" was a Tyneside colliery slang term for a wagon or train of wagons.