The “Puffing Billy” and her two sisters can be described as the first adhesion locomotives that were in commercial service for several years. Richard Trevithick's “Pen-y-Darren” was the first working steam engine, but after a short trial it was converted back into a stationary steam engine. Although John Blenkinsop had the idea of transporting coal on rails with a rack system as early as 1812, this system did not catch on at the time due to the high additional costs for the rails. William Hedley, the owner of Wylam Colliery, therefore experimented with a vehicle that was powered by a hand lever and could move without cog wheels. As this was a success, he designed a locomotive with Timothy Hackworth.

This vehicle stood on two axles, between which was a crankshaft, which was driven by two vertical cylinders via long levers. The crankshaft transmitted power to the axles via gears. Since the first rails had a U-shaped profile with a gauge of five feet, the wheels could be designed without wheel flanges. The cylinders were connected to the boiler's hot water to prevent the steam from condensing. This made maintenance much easier than on other early steam locomotives where the cylinders were inside the boiler. The early boiler did not yet have tubes, but a single, U-shaped flue. Because of this arrangement, the chimney was next to the fire door and the fireman stood at this end of the locomotive, where the tender was also attached. The engine driver stood at the other end and operated the engine from there, which made operation in both directions possible without any problems.

Schematic drawing

Railway and Locomotive Engineering, January 1903

The three engines now hauled 50-ton coal trains the five-mile route to the port of Lemington, which took them about an hour. They remained in service for several decades and have been rebuilt several times in the meantime. The first, somewhat bizarre conversion concerned the “Puffing Billy”, which was used to drive a steamship for a while and was later dismantled again for use on rails. For a time the locos had four powered axles with smaller wheels and a single-axle tender. From 1830 the trains ran on rails with a modern profile and the locomotives were fitted with flanged wheels. The “Puffing Billy” was loaned to the Museum of Patents in London in 1962 and a few years later ended up in the Science Museum in the same city, where it still stands today. The “Wylam Dilly” was sold to the Royal Museum in Edinburgh in 1868 and can still be found there today. Only the whereabouts of the “Lady Mary” are unknown. A functional replica was built in Bavaria in 1906 and another in England in 2006.