Making “The Rocket” Fly — Marc Seguin

The Rocket — winner of the Rainhill Trials

Marc Seguin, a French inventor and industrialist, made the breakthrough leading to the development of the first practical steam locomotive. Credit for the invention of railways goes to English engineers who worked during the first decades of the 19th century. The Rainhill Trials was a defining event in the history of railways. The father and son team of George and Robert Stephenson won the competition with their steam locomotive, named “The Rocket,” but they relied on an innovative new boiler design patented by Marc Seguin in the previous year.

The Rainhill Trials was held to demonstrate the feasibility of the steam-powered locomotive. The technology of the steam engine had been in use for over 100 years at the time of the competition, but it was used almost entirely as a source of power for machines fixed in place, such as in mines and factories. Adapting this technology for transportation, in boats or wheeled vehicles, required shrinking the machinery by about a factor of 10 without too much reduction in the already modest power output of these engines.

A typical Boulton and Watt steam engine manufactured at the end of the 18th century weighed 20 tons and was the size of a three-story building, but it delivered only about 20 horsepower. Early attempts to adapt this technology to power a locomotive produced machines that were either too heavy, woefully underpowered, or both.

Marc Seguin had first-hand experience with these challenges. In the 1820s, Seguin built two steamboats for transportation along Rhone River. However, the new steam boilers designed for this purpose proved incapable of providing the power needed to navigate against the river’s current. Frustrated with the limitations of the available technology, Seguin began investigating ways to increase the rate that a boiler can convert fuel to steam — a measure of its power output — while also decreasing its size and weight.

Seguin achieved this with a design that pumped the hot gases from combustion through a set of tubes immersed in the water within the boiler vessel. This was not an entirely new idea. Other boiler designs similarly had used tubes to increase the area active in transferring heat to the water from the burning fuel. But, Seguin realized that for this approach to succeed there must also be a mechanism to increase air flow through the combustion chamber to compensate for the restriction on flow introduced by venting the flue gases through a set of relatively small tubes.

Seguin obtained a patent in France for his new tubular boiler in December 1827 after conducting a successful series of experiments on a prototype boiler in the fall. In the summer of 1828, Seguin received two steam locomotives built in the Stephenson’s workshops for a railway Seguin was building near Lyon. He immediately set out to modify the new locomotives by replacing the boilers that the Stephensons had supplied with boilers using Seguin’s new tubular design, a change that saved three quarters of the weight while maintaining the same rate of steam production.

At the same time, George and Robert Stephenson began the design and construction of the locomotive they intended to enter into the Rainhill Trials the following year. Undoubtedly, the Stephensons knew about Seguin’s new tubular boiler, if only from the documentation provided by his French patent. Using a modified version of Seguin’s design, The Rocket achieved a top speed of 32 mph in front of an astonished crowd of onlookers, a feat that was compared with the flight of a swallow. It takes nothing away from the accomplishments of George and Robert Stephenson to acknowledge that it was Marc Seguin’s tubular boiler that made The Rocket fly.

Marc Seguin is one of the 72 engineers and scientists named on the Eiffel Tower.

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William Nuttle

William Nuttle

Navigating a changing environment — hydrologist, engineer, advocate for renewable energy, currently writing about the personal side of technological progress