Railway 200: the steam locomotive

This year, the railway community celebrates the 200th anniversary of what is said to be the birth of the modern railway. On 27 September 1825, George Stephenson’s ‘Locomotion No. 1’ set off on its inaugural journey from Shildon to Stockton to open the 26-mile Stockton and Darlington Railway (S&DR). This was the first practical public railway to carry both freight and passengers.

Yet both railways and steam-powered locomotives existed long before the S&DR’s opening. Between 1801 and 1825, 16 railways authorised by acts of Parliament were built. In 1801, the eight-mile Surrey Iron railway between Wandsworth and Croydon became the first horse-drawn public railway for independent goods hauliers. The Swansea and Oystermouth railway operated horse drawn carriages in 1807 to become the first fare-paying passenger railway.

Some of these early railways did try the use of steam locomotives. In 1812, a steam powered rack railway locomotive operated on Middleton Railway. A steam locomotive also operated on the Kilmarnock and Troon Railway (K&TR) in 1817. However, its weight caused frequent broken rails. A local entrepreneur operated a passenger service with empty coal wagons to carry passengers from Kilmarnock to the coast at Troon. To do so he paid the railway a toll based on tonnage of passengers carried.

Prior to the railways, canals were the only way to carry goods in bulk. The first canal opened in 1757. By 1840, there were over 4,000 miles of canals on which horses could haul 50-ton loads compared with just over half a ton over an unmade road. At slow speeds canals offered less resistance to motion than railways on which a horse could only haul eight tons. However, canals could not compete with the speed and capacity of even the early steam-hauled railways which offered a huge increase in connectivity and turbo-charged the industrial revolution.

Thus, the steam locomotive can be said to be one of the world’s most transformational inventions. As part of Rail Engineer’s contribution to Railway 200, this article describes the development of the early steam locomotives. Yet, as the K&TR’s broken rails showed, railways are a system. Hence future Railway 200 articles will describe the development of the track and other aspects of the early railway.

Static steam engines

The credit for the first steam engine to produce thrust from a piston in a cylinder goes to French physicist, Denis Papin. Between 1690 and 1707 he built various steam engines but did not develop them commercially. In 1698, military engineer Thomas Savery patented a pistonless steam pump that used the vacuum created when steam condensed in a vessel to raise water under atmospheric pressure. This meant that the pump could be no more than 30 feet above the water level. 

The first practical steam-driven pump was produced by an Exeter ironmonger, Thomas Newcomen, and thought to have been first used in 1712 at a coal mine in Dudley. Newcomen engines were also installed at the Byker colliery in Northumberland around 1718. These engines used steam with a pressure of less than one pound per square inch (psi) which could do no useful work.

They had a piston coupled to a pump rod via a rocking beam. The weight of the pump rods pulled down the beam and so lifted the piston allowing steam into the cylinder. At the top of the piston stroke, cold water was injected into the cylinder to condense the steam and create a vacuum that forced the piston down under atmospheric pressure and lift the pump rods.

The Newcomen engine had an efficiency of less than 1% as the cylinder had to be reheated after it had been cooled. Yet, these machines, which typically produced 10 horsepower, were the only way to drain deep mines. Furthermore, the supply of coal was not a problem at coal mines.

In 1769, James Watt patented condensing steam in a separate condenser to avoid reheating the cylinder. He filed a further patent in 1784 to give a steam engine rotary motion using a planet gear at the end of a connecting rod to drive a sun gear on a rotating shaft. Prior to that, reciprocating steam engines could only power pumps. However, to drive machinery their speed had to be controlled. For this, in 1788, Watt patented the conical pendulum steam governor.

Watt then doubled the cylinder’s power output by making it double acting. This required effective seals for piston rods moving through cylinder covers and a parallel motion for piston rods to move in straight lines. These arrangements were patented respectively in 1781 and 1782.

Increasing a steam engine’s power-to-weight ratio in this way made a steam powered vehicle feasible. However, Watt seems to have had no interest in this and was concerned about the practicability and safety of high-pressure steam. His business partnership with Matthew Boulton to produce static engines was a great success and, as shown below, in the early 1800s, there was no market for steam powered vehicles.

Richard Trevithick

The development of steam-powered vehicles was pioneered by Cornish mining engineer Richard Trevithick (1771 to 1833). However, he wasn’t the first to do so. For example, French military engineer Nicolas Cugnot produced an unsuccessful cumbersome large steam carriage in 1769 to haul cannons. Trevithick’s road vehicles, which used high-pressure steam, did achieve a measure of success. He also produced the first working railway steam locomotive.

By the late 1790s, boilers could safely contain steam at pressures of around 60 pounds per square inch (psi). Such ‘strong steam’ required cylinders of a much smaller diameter than the Watt engines which  operated at typically 2 psi. Furthermore, as they do not rely on atmospheric pressure, high-pressure engines can exhaust into the atmosphere without the need for a condenser.  The resultant space and weight savings made possible the use of high-pressure steam engines for road and rail traction.

The boiler pressure of Trevithick’s first road vehicle, the Puffing Devil, was 60 psi. This had a single cylinder which exhausted into the chimney to cause a draught to draw the fire and heat the boiler feed water. In 1801, Puffing Devil successfully carried six passengers up an incline in Camborne, though the poor road surfaces of the time were problematic. 

In 1803, Trevithick built another a steam road carriage which he drove between Holborn and Paddington. This was lighter than Puffing Devil and had larger wheels to accommodate the poor road surfaces. However, it was abandoned as it was more expensive to operate than a horse drawn carriage.

Trevithick then produced a locomotive for the Pen-y-Darren Ironworks at Merthyr Tydfil.  This operated at 40 psi and had a cylinder diameter of 4.75 inches.  It relied on wheel / rail adhesion to haul the train though its four wheels were coupled by cogwheels. In 1804, this hauled 10 tons of iron in five wagons for 10 miles from the ironworks to the Abercynom canal wharf to become the world’s first recorded locomotive-hauled train. However, its weight significantly damaged the railway and so it was consigned to a static role.

His next locomotive, ‘Catch me who can’, weighed eight tons and ran on a circular track at an exhibition near Euston in 1808 at speeds of up to 15mph until the exhibition closed after a few weeks due to rails breaking under the locomotive. This was the first locomotive to haul fare-paying passengers.

While Trevithick demonstrated the potential for steam railway traction and achieved some notable world firsts, he did not profit from this and was made bankrupt in 1809. There was no market for his engines which were too heavy for the rail track of the time. 

Middleton railway

The 1757 Middleton Railway Act was the first Act authorising the construction of a railway. This was a two-mile wagonway between the Middleton coal mines and the River Aire’s coal wharves in Leeds. With the Napoleonic wars dramatically increasing the prices of horses and their feed, it was decided to use steam locomotives.

At the time it was felt that an engine light enough not to break the track would not have sufficient adhesion to haul a heavy load. Hence the locomotive’s driving wheel had a pinion gear that meshed with a toothed rail. This was designed by Matthew Murray of Leeds and was based on Trevithick’s ‘Catch me who can’ but had two cylinders and six wheels with pinions on their centre wheels.

This five-ton locomotive was named Salamanca and successfully hauled its first train of eight wagons weighing a total of 26 tons on 24 June 1812. This was the world’s first rack railway and the world’s first commercially viable steam railway as Salamanca and three other engines replaced 50 horses. However, two of these locomotives suffered boiler explosions in 1818 and 1834.

Wylam Colliery developments

The Middleton rack railway was symptomatic of a concern that the adhesion between wheels and rails was not sufficient to haul a heavy train. To solve this imagined problem various solutions were proposed including chain haulage and a locomotive with mechanical legs.

In 1812, William Hedley, a Wylam coal mine manager, undertook various experiments with carriages on the colliery’s cast iron plate rails to confirm that the friction between wheels and rails was sufficient to haul a heavy train. He also considered that locomotives would be less likely to slip if their driving wheels were connected.

With the assistance of his blacksmith, Timothy Hackwork, in 1814 Hedley build the locomotive Puffing Billy. This had two vertical cylinders driving a single crankshaft between the frames from which gears drove and coupled the two driving axles by underframe gearwheels. However, these eight-ton locomotives were too heavy for cast iron plate rails and so were modified to have four axles. Puffing Billy is the world’s oldest surviving locomotive and is on display at the Science Museum.

George Stephenson

In the early 1810s, George Stephenson was the engine wright at Killingworth collieries, where he had invented a miner’s safety lamp. While there, he followed steam locomotive developments with interest. One of Murray’s Middleton locomotives had worked on Tyneside, and he was aware of the use of locomotives at his birthplace in Wylam.

After the Killingworth Colliery owners had agreed to his suggestion to use steam traction, in 1814 he built his first locomotive modelled on Murray’s locomotive. As Killington colliery had edge rails, this was the first successful flanged-wheel locomotive which could pull 30 tons up an incline of 1 in 450 at 4mph. In 1815, Stephenson patented an improved locomotive that used the steam exhaust to draw the fire.

While at Killingworth, Stephenson produced around 15 locomotives. While most of these for use at Killingworth or the Hetton colliery railway, they included the KT&R’s locomotive and one for a Swansea colliery. 

He also considered the problem of heavy locomotives causing rail breaks. At the time, cast iron plate rails were the norm although, as at Killingworth, iron edge rails were being introduced. To improve the resilience of fish-bellied edge rails Stephenson developed and patented a half lap joint.

To reduce the impact load on the rails, he unsuccessfully experimented with a steam spring that supported the locomotive frame by steam pressure acting on pistons.

In 1820, the owners of the new Hetton Colliery engaged Stephenson to build an eight-mile railway from the colliery to the River Wear’s coal wharves in Sunderland. This was the first railway designed for mechanical haulage but used a combination of locomotives and five cable hauled inclines. From Hetton, the line climbed 200ft in three miles and then descended 500ft to the River Wear for five miles. This railway opened on 18 November 1822.

It was built using fish-bellied edge rails with Stephenson’s patented joints. More significantly, its gauge was Stephenson’s 4ft 8 ½ inch which was also that of the Killingworth wagonway and would eventually, thanks to Stephenson’s influence, become the standard gauge of railways throughout the world.

Robert Stephenson and Company

In 1821, Stephenson was appointed to plan the Stockton and Darlington Railway (SD&R) and tasked with building it in 1822. Edward Pease, its principal promoter shared Stephenson’s conviction that locomotives were the future and so they formed a partnership to manufacture them.

As a result, the world’s first locomotive manufacturing company, Robert Stephenson and Company (RS&Co) was founded in 1823 with a workshop at Forth Street, Newcastle. George’s son, Robert was made the managing partner. Initially, the company had orders for five static engines and two steamboat engines. In September 1824, it received an order for two S&DR locomotives.

The first of these was the 6.5-ton Locomotion No 1 which, on 27 September 1825, hauled The SD&R’s inaugural train which had an estimated load of 79 tons. By 1826, RS&Co had produced three more S&DR locomotives: Hope, Black Diamond, and Diligence. Yet, other than their blast pipe and coupled wheels, these locomotives were similar to the locomotives produced by Trevithick and Murray. They also only had single flue boilers which wasted a lot of heat.

Thus, while George actively promoted the steam locomotive, several fundamental improvements were yet to be made. It was to be his son, Robert who would introduce further significant innovations. Rather than its locomotives, S&DR became a practical operational railway as its novel malleable wrought iron rails could withstand the weight of the line’s locomotives.

Robert Stephenson missed the S&DR’s opening as he had a three-year contract with the Columbian Mining Association. He did not return to Newcastle until 1827 when his immediate priority was reviving the fortunes of RS&Co by improving its locomotive designs.

In 1828, RS&Co supplied the Bolton and Leigh Railway with the Lancashire Witch. This had cylinders inclined at 45° which enabled its axles to be sprung, making it probably the first locomotive with steel springs. Another first was an expansion valve that used a plug valve to cut off steam admission halfway through the inlet valve stroke.

Rocket and beyond

When the Liverpool and Manchester Railway (LM&R) was planned, it felt that cable haulage might be necessary as it was not known whether locomotives could haul trains up its steep gradients. To resolve this issue, the Rainhill trials were planned to take place in October 1829. The requirement was for a 20-ton load as the L&MR was to carry passengers as well as freight. After the trials, Rocket was successfully tested on a 1 in 96 incline.

With the requirement to haul such a light load, success required a fast, light engine more efficient than any before it. The locomotive that RS&Co entered for the trial was the Rocket. Robert Stephenson is generally given credit for its design as George was in Liverpool at the time overseeing the L&MR’s construction. 

Rocket featured the innovations on the Lancashire Witch such as springs and wheels driven directly from inclined cylinders. To reduce weight, it only had two driven wheels. It also had a radically new type of boiler with 25 three-inch diameter tubes. These required tube-plates at each end of the boiler and provided considerably more heating area than a single flue.

This arrangement required a separate fire box which was formed of a double layer of copper plates, with water filling the space between them. These provided excellent conductivity and were shaped to provide a crown around the fire-grate to direct hot gases directly through the tubes and up the chimney below which the cylinder blast pipes drew the fire. This was maximised by experiments to optimise the blast pipe diameter. A rear back-plate had a door for the crew to feed coke to the grate. Coke was used as the LM&R’s Act required its locomotives to consume their own smoke.

As is well known, with such innovations, the 4.25-ton Rocket, hauling 13 tons at up to 28mph won the Rainhill trials to become, perhaps, the best-known steam locomotive. After Rocket, RS&Co continued to improve its designs to the extent that when the L&MR opened in 1830, a year after the trials, Rocket was an outdated locomotive. In November that year the RS&Co’s Planet locomotive ran the 30 miles between Liverpool and Manchester in an hour. This had cylinders below the boiler which drove the wheels through cranked axles.

Thus, in just three years, RS&Co had transformed the design of cumbersome colliery locomotives into main line engines that had almost all the features of future steam locomotives. In 1842, the company perfected one more innovation, the Stephenson link valve gear which enables crews to vary cylinder steam admission by operating a lever on the footplate.

By 1899, RS&Co had built 3,000 locomotives at its Newcastle plant and in that year opened its Darlington works. The company eventually became part of English Electric in 1944.

Pioneers

While it is right to celebrate the opening of the SD&R in 1825, it should be recognised that this was but one of the early railway milestones that laid the foundations of today’s railways. Before then, significant firsts were achieved by railways at Middleton, Wylam, and Hetton and, after the SD&R, the opening of the Liverpool and Manchester Railway gave the world its first main-line railway. Although the Stephensons did much to develop early steam engines, the role of early pioneers such as Watt, Trevithick and Murray should not be forgotten. Indeed, it is fair to say that Trevithick was the inventor of the steam locomotive.

It is also important to appreciate that, from the start, successful locomotive-powered railways could only operate as a system. The early locomotives were not much more powerful than the horses that they replaced and were only able to use their power due to the low rolling resistance of their wheels on early railway tracks. Furthermore, they could only operate reliably if the rails could withstand the locomotive’s weight. Hence the novel wrought iron railways of the SD&R could be said to be the key innovation that made this railway a success.

Thus, the evolution of the early railways is a story that is both fascinating and has lessons for today.

Image credit: David Shirres