Currently on display for all to see at the Royal Museum in Edinburgh, the Wylam Dilly is one of the world’s oldest surviving steam locomotives. Built in 1815 by British engineer William Hedley, it was designed to transport coal up and down the Wylam waggonway, a precursor to the traditional railway.
Weighing nearly eight tons, the Dilly needed eight wheels in its original form to spread its load on the primitive castiron waggonway plates, which on four proved too much (it was later converted back to four as rails improved). It was powered by a central boiler with a single exhaust chimney, that at full capacity allowed the locomotive to hit a top speed of just 8km/h (5mph).
The Wylam Dilly is notable due to its early addition of features. Hedley added piston rods extending upwards to pivoting beams – connected via rods – to the engine’s crankshaft. This allowed the Dilly’s gears to both drive and couple its wheels, granting better traction.
After five years of service the Wylam Dilly was mounted on the keel of a steam paddlewheeler, ferrying civilians across the River Tyne, England.
Answered by HIW.