Steam locomotives

The first locomotive to haul a train of wagons on rails was designed by Cornish engineer Richard Trevithick and was demonstrated in 1804 on a plateway at Merthyr Tydfil, South Wales.[12] Although the locomotive successfully hauled the train, the rail design was not a success, partly because the locomotive's weight broke a number of the brittle cast-iron plates. Despite this setback, another area of South Wales pioneered rail operations when, in 1806, a horse-drawn railway was built between Swansea and Mumbles: the Swansea–Mumbles railway started carrying fare-paying passengers in 1807 – the first in the world to do so.[13]

In 1811 John Blenkinsop designed the first successful and practical railway locomotive.[14] He patented a system of moving coals by a rack railway worked by a steam locomotive (patent no. 3431), and a line was built connecting the Middleton Colliery to Leeds. The locomotive (The Salamanca) was built in 1812 by Matthew Murray of Fenton, Murray and Wood.[15] The Middleton Railway was the first railway to successfully use steam locomotives on a commercial basis. It was also the first railway in Great Britain to be built under an Act of Parliament.

Blenkinsop's engine had double-acting cylinders and, unlike the Trevithick pattern, no flywheel. Due to previous experience with broken rails, the locomotive was made very light in weight and this brought concerns about insufficient adhesion; so instead of driving the wheels directly, the cylinders drove a cogwheel through spur gears, the cogwheel providing traction by engaging with a rack cast into the side of the rail.