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Rocket, Stephenson's locomotive
Science Museum, South Kensington, London, UK
<em>Rocket</em>, Stephenson's locomotive
associated engineer
Robert Stephenson
George Stephenson
Henry Booth
date  1829
UK era  Georgian  |  category  Steam Engine or Locomotive  |  reference  TQ265792
ICE reference number  HEW 944
photo  courtesy Graces Guide to British Industrial History
In 1829, the Liverpool & Manchester Railway (L&MR) ran a competition to establish the best form of motive power for the line. The Rainhill Trials confirmed steam locomotion as the right choice and Rocket, the Stephensons’ entry, as the most reliable engine, winning the £500 prize. Rocket subsequently worked the L&MR, along with a number of similar Stephenson locomotives. The engine was modified in the 19th century, before becoming a permanent exhibit at what is now the Science Museum, London.
The L&MR is a landmark in the history of the railways — the first inter-city passenger line. Steam locomotive pioneer George Stephenson (1781-1848) was its engineer. Most railways at the time were powered by a combination of horse power and rope haulage driven by stationary steam engines. So the Rainhill Trials attracted much interest.
However, the reliability of early engines was an issue, and moving them around the country was a challenge. Of the many competition entrants, only five teams managed to get their locomotives to the level stretch of track at Rainhill in Merseyside for the trials. And only four were fit to take part at the start of the contest — Cycloped, Novelty, Rocket and Sans Pareil — which was conducted over several days during the period 6th to 14th October 1829.
Rocket was entered by George Stephenson, his son Robert Stephenson (1803-59) and L&MR company treasurer Henry Booth (1788-1869). She was built at the Robert Stephenson & Co. works, Forth Street, Newcastle upon Tyne, and track tested on the Killingworth Colliery Railway.
Though George Stephenson is often credited with the design of Rocket, it’s likely he was too busy with the challenges of constructing the L&MR, plus many other railway projects, to have had more than partial input. Robert Stephenson had the technical expertise to design a cutting edge locomotive, as well as having the mechanical engineering capabilities of the Stephenson factory to draw on.
Originally known as the ‘Premium Locomotive’, Rocket is constructed of cast and wrought iron, brass, copper and oak timbers. Her design is in many ways an improved version of the Stephensons' Lancashire Witch, which was constructed for the L&MR in 1828, but leased initially to the Bolton & Leigh Railway, also engineered by George Stephenson.
Rocket was the first locomotive to have a single pair of driving wheels, saving on weight and cost. The 1.435m diameter driving wheels were at the front, and made of timber with iron rims. The rear wheels were of cast iron, 762mm in diameter. The wheel base was 2.184m.
Two cylinders, each of 203mm diameter and 432mm stroke, at the rear end of the boiler were inclined at an angle of 35 degrees so that the piston rods drove onto the leading axle and turned the front wheels. The cylinders were mounted on iron plates bolted to the boiler.
Her boiler had a cylindrical wrought iron shell, 1.02m in diameter and 1.83m long, with flat end plates. The barrel was made from four plates, with a circumferential lap joint and longitudinal butt joints. However, it was the inside of the boiler that would make such a difference to her performance and set the standard for other locomotives to follow.
One of the main challenges in the design of locomotive engines of the day was sustaining sufficient head of steam to enable continuous operation. To comply with the Railway Act, locomotives had to "consume their own smoke", which meant being fuelled by coke rather than coal. Coke burns less readily and requires greater heat and air flow for combustion. And heating a greater surface area produces more steam.
Booth had reported to the L&MR directors in 1927 that he had found a way to resolve the issues. His discovery was the multi-tube boiler, a device invented separately by at least three others, including French engineer Marc Seguin (1786-1875). On 30th April 1827, George Stephenson was instructed to "make any experiments necessary to decide the real merits of the scheme, it being understood that an expenditure of £100 would be sufficient for the purpose".
At Booth’s suggestion, Lancashire Witch was to have had a three-tube boiler, later changed to two tubes for ease of construction. For Rocket, the design was refined to provide a much larger heating area. Her boiler shell contained 25 copper 'fire tubes’ of 76mm diameter, secured by ferules through the end plates. In operation, coke was fed into a firebox at the rear of the boiler where combustion took place, driving hot gases through the tubes and into the smokebox on the front of the boiler, heating the water in the boiler in the process.
The separate firebox was another innovation. Its volume and larger grate resulted in better fuel combustion than simpler designs where the furnace was located at one end of the boiler flue, such as on Sans Pareil, designed by Timothy Hackworth (1786-1850). Rocket’s firebox design further increased heating by having a double copper-plate water jacket to the top and sides. The heating surface totalled 15.2 sq m — 12.8 sq m from the boiler, 1.8 sq m from the firebox and 0.6 sq m from the grate.
The improved heating capacity produced more steam with less fuel. As Nicholas Wood (1795-1865) noted in A Practical Treatise on Rail-Roads, "the Rocket requiring only 11.7 lbs [of coke] to convert a cubic foot of water into steam, while the Sans Pareil required 28.8 lbs" — two and a half times as much.
Steam in Rocket’s boiler entered a dome on top of the boiler and was admitted to the cylinders via two pipes leading from a regulating cock above the firebox. Her boiler pressure was limited to 344.7kN per sq m (50psi) above atmospheric pressure by two safety valves.
Exhaust steam from the cylinders was vented via two pipes with 38mm diameter brass nozzles, into the chimney, which stood some 4.5m above the rails and was supported by stays from the boiler plates. This turned the chimney into a blast pipe by creating a partial vacuum inside the base of the chimney, sucking air through the furnace grate and boiler flues and feeding the fire with more oxygen, intensifying the locomotive’s efficiency.
Rocket’s engine was framed between her wheels with 102mm by 25mm wrought iron bars, with four supporting brackets for the boiler and cast iron axle guards. Weight was transmitted to the axles by plate springs.
She weighed 3.3 tonnes empty and 4.32 tonnes in working order with water in the boiler. Her timber tender had four wheels of 914mm diameter and a wheel base of 1.22m. It weighed 3.25 tonnes when loaded with fuel and a full water barrel, making a total of 10.87 tonnes for the locomotive and tender.
The general arrangement of direct connection between cylinder and wheel, in conjunction with a multi-tube boiler and a blast pipe, became known as the 'Stephenson form' of locomotive.
Rocket won the Rainhill Trials with consistent reliability and high speeds on level runs and uphill She was purchased by the company for use on the L&MR. The prize money probably recouped the cost of construction, but more valuable than that was the contract awarded to Robert Stephenson & Co. for the supply of similar locomotives. Hackworth's Sans Pareil was also purchased by the L&MR.
On 19th October 1829, Rocket made a further series of runs over a level 2.4km course at Rainhill to determine the best in-service loading. She pulled loads of 37.85, 42.42 and 47 tonnes (including the weight of the engine and tender), showing a slight increase in speed with weight (momentum). Her average performance at 37.85 tonnes gross, equivalent to 20.32 tonnes of freight, was a speed of 20.9kph (13mph).
The L&MR’s directors adopted goods loads of 20.32 tonnes everywhere on the line, except at the inclines where locomotives hauled 12.19 tonnes of freight uphill at 16.1kph (10mph).
On 1st January 1830, Rocket traversed the L&MR’s newly completed Chat Moss Crossing with a carriage of passengers.
The L&MR opened on 17th September 1830. By that time, Rocket’s cylinders had been lowered to an angle of 8 degrees, providing a smoother ride that was less punishing to the rails.
She was in service until 1844, first at the L&MR and then on the Brampton Railway (an extension of the 18th century Midgeholme line of Lord Carlisle). In 1862, she was donated to the Patent Office Museum in London, the forerunner of the Science Museum.
Contractor: Robert Stephenson & Co, Newcastle
Research: ECPK
"The Rainhill Trials" by Christopher McGowan, Little, Brown, London, 2004
"George and Robert Stephenson: The Railway Revolution" by L.T.C. Rolt, Penguin Books Ltd, London, 1984
"Rocket 150, 150th Anniversary of the Liverpool & Manchester Railway 1830-1980, Official Handbook", British Rail, London, 1980
"George Stephenson: The Engineer & His Letters" by W.O. Skeat, The Institution of Mechanical Engineers, London, 1973
"A Practical Treatise on Rail-Roads, and Interior Communication in General. Containing numerous experiments on the powers of the improved locomotive engines: and tables of the comparative cost of conveyance on canals, railways, and turnpike roads" by Nicholas Wood, 3rd edn, Longman, Orme, Brown, Green, & Longmans, London, 1838
"Report to the Directors of the Liverpool and Manchester Railway, on the Comparative Merits of Locomotive and Fixed Engines, as a Moving Power" by James Walker (March 1829), "Observations on the Comparative Merits of Locomotive and Fixed Engines, as Applied to Railways" by Robert Stephenson and Joseph Locke (February 1830), and "An Account of the Liverpool and Manchester Railway" by Henry Booth (December 1830), bound together in an American edition, Carey & Lea, Philadelphia, 1831
reference sources   CEH NorthSmiles3

Rocket, Stephenson's locomotive