Although many would consider Rocket, built by engineers George and Robert Stephenson in 1829, to be the first steam locomotive, this is not actually true. There were locomotives being built up to 25 years before Rocket - examples include Puffing Billy, Locomotion, The Royal George and Sans Pareil. In fact the first person to build a steam powered railway locomotive was Richard Trevithick. Rocket actually was a reinvention of the often unreliable and uneconomical designs that had gone before, and it presented the founding principles upon which all modern steam engineering is based.
The main innovation within Rocket's design was the use of a multi-tubular boiler which increased the heat exchange surface and maximised the efficiency of the heat transfer between the exhaust gases and the water. Previous designs had consisted of little more than a single pipe surrounded by water. Rocket was also one of the first locomotives to incorporate a blast pipe. This device is a tube from the cylinders to the base of the chimney, allowing the steam to escape. The positioning of the pipe means the blast of exhaust that it emits pulls some air from the smoke box with it, thus creating a partial vacuum within the smoke box which in turn draws fumes and hot gases though the boiler from the firebox. Previous designs had had to rely on the draft from the chimney alone to draw fumes through the boiler.
The Rainhill Trials
In October 1829, the directors of the soon-to-be completed Liverpool and Manchester Railway held a competition to find an appropriate locomotive. The prize they offered was £500, roughly the equivalent of £70,000 today. This competition, later to become known as the Rainhill Trials, took place over several weeks. Ten engines were entered, though only five ended up competing, Stephenson's Rocket included.
The five engines that were entered were the Novelty, a design by Messers Braithwaite and Ericsson; Sans Pareil, designed by Timothy Hackworth of Darlington; Perseverance1, by a Mr Burstall of Edinburgh; Cycloped2, by a Mr Brandreth of Liverpool; and of course Rocket by Stephenson.
For a locomotive to be eligible to win it had to satisfy the following conditions:
Each engine entered should weigh less than six tons, and be capable of regularly hauling trains of a weight equal to three times that of the locomotive at a minimum speed of ten miles per hour over level track. It was also important that the pressure of the steam in the boiler should not exceed 50 pounds per square inch.
The engine and boiler should be supported on springs, and rest on six wheels, and the height from the ground to the top of the chimney should be less than 15 feet3.
The engine should 'effectually consume its own smoke', ie, not emit large volumes of smoke in a wasteful or polluting manner.
There should be two safety-valves, one of which should be completely out of the reach of the driver to avoid interference.
The three main competitors in the trials were Novelty, Sans Pareil and of course Rocket. The Novelty was much lighter and faster than the others, and got up to 28mph on the first day, but on the second day a boiler pipe was damaged by over-heating. To get at it the engineers had to partially dismantle the boiler, and when they rebuilt it the cement didn't have time to dry. On the next run it cracked, and the Novelty was so badly damaged it had to retire. After this the clear winner was Stephenson's Rocket, for after a modification during the tournament it was able to haul the enormous weight of 20 tons at over 20 mph! Rocket also demonstrated its ability to climb the nearby Whiston incline unaided, proving that static winding engines were unnecessary.
Because of this fantastic result Stephenson walked away with the prize, and Rocket was employed by the Liverpool and Manchester Railway Company4.
However, there is much controversy as to whether or not Stephenson himself invented the blast pipe. This controversy has been unearthed recently after the disclosure of a letter, dated 25 July, 1828, from Stephenson to fellow railway engineer Timothy Hackworth, the alleged real inventor of the blast pipe. Hackworth's locomotive The Royal George was built in 1827 and featured the blast pipe, but it was never particularly famous, unlike Rocket which became famous after winning the Rainhill Trials in 1829. The result of the Rainhill Trials credited the Stephenson with the invention of the blast pipe, a claim that he apparently never denied.
Further controversy was present at the time when it emerged that Sans Pareil had been performing well until it suffered a cracked cylinder pipe which, as it turns out, was cast by a company owned by Stephenson.
Despite this controversy, Stephenson's Rocket is still historically significant, so much so that it has been preserved and is on display in the Science Museum in London. In 1979, a replica Rocket was built by Locomotion Enterprises for the 150th anniversary celebrations, albeit with a slightly shorter smoke stack.