The Railton Special, later rebuilt as the Railton Mobil Special, is a one-off motor vehicle

Motor vehicle

A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

 built for John Cobb

John Cobb (motorist)

John Rhodes Cobb was a British racing motorist. He made money as a director of fur brokers Anning, Chadwick and Kiver and could afford to specialise in large capacity motor-racing...

's successful attempts at the land speed record

Land speed record

The land speed record is the highest speed achieved by a wheeled vehicle on land. There is no single body for validation and regulation; in practice the Category C flying start regulations are used, officiated by regional or national organizations under the auspices of the Fédération...

.

It was powered by two supercharged W12-block

W12 engine

A W12 engine is a twelve cylinder piston internal combustion engine in a W configuration. W12 engines are manufactured in two distinct configurations. One configuration uses four rows of three cylinders merged into two 'cylinder banks' , coupled to a common crankshaft - as in Volkswagen Group W12...

 Napier Lion

Napier Lion

The Napier Lion was a 12-cylinder broad arrow configuration aircraft engine built by Napier & Son starting in 1917, and ending in the 1930s. A number of advanced features made it the most powerful engine of its day, and kept it in production long after contemporary designs had stopped production...

 VIID (WD) aircraft engines. These engines were the gift of Betty 'Joe' Carstairs

Betty Carstairs

Betty Carstairs was a wealthy British power boat racer known for her speed and her eccentric lifestyle.-Biography:She was born in 1900 as Marion Barbara Carstairs in Mayfair, London, England, the daughter of Frances Evelyn Bostwick, second child of Jabez Bostwick and his wife Helen, and Captain...

, who had previously used them in her powerboat Estelle V. Multiple engines was not a new technique, having already been used by the triple-engined White Triplex

White Triplex

The White Triplex was a land speed record car built for J. H. White and driven by Ray Keech. It was powered by three 27-litre Liberty aero-engines, for a total of 36 cylinders, 81 litre displacement and a claimed 1500 bhp.A wealthy American, J. H...

 and the Railton Special's contemporary rival, Captain Eyston's twin-engined Thunderbolt

Thunderbolt (car)

Thunderbold is a British Land Speed Record holder of the 1930s, driven by Captain George E.T. Eyston- Records held :Between 1937 and 1939, the competition for the Land Speed Record was between two Englishmen: Captain Eyston and John Cobb. Thunderbolt's first record was set at on 19 November 1937...

. With the huge powers thus available, the limitation was in finding a transmission and tyres that could cope. Reid Railton found a simple and ingenious solution to this by simply splitting the drive from each engine to a separate axle, giving four wheel drive.

On 15 September 1938, the Railton Special took the land speed record

Land speed record

The land speed record is the highest speed achieved by a wheeled vehicle on land. There is no single body for validation and regulation; in practice the Category C flying start regulations are used, officiated by regional or national organizations under the auspices of the Fédération...

 from Thunderbolt

Thunderbolt (car)

Thunderbold is a British Land Speed Record holder of the 1930s, driven by Captain George E.T. Eyston- Records held :Between 1937 and 1939, the competition for the Land Speed Record was between two Englishmen: Captain Eyston and John Cobb. Thunderbolt's first record was set at on 19 November 1937...

 at 353.3 mi/h, also being the first to break the 350 mi/h barrier. Eyston re-took the record within 24 hours (357.50 mph / 575.34 km/h), holding it again until Cobb took it a year later on 23 August 1939 at a speed of 369.7 mi/h.

After the Second World War further development and sponsorship by Mobil Oil led to re-naming as the 'Railton Mobil Special'. It was the first ground vehicle to break 400 mi/h in a measured test. On September 16, 1947 John Cobb averaged 394.19 mi/h over the measured mile in both directions to take the world land speed record.

It weighed over 3 tonnes and was 28 in 8 in (8.74 m) long, 8 ft (2.4 m) wide and 4 in 3 in (1.3 m) high. The front wheels were 5 in 6 in (1.68 m) apart and the rear 3 in 6 in (1.07 m). The National Physical Laboratory's wind tunnel

Wind tunnel

A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...

 was used for testing models of the body. It was designed by Reid Railton and is currently on display at the Thinktank

Thinktank, Birmingham

Thinktank is a science museum in Birmingham, England. Opened in 2001, it succeeded and has several exhibits from the City's Museum of Science and Industry. It is part of the Millennium Point complex.-Building:...

 museum in Birmingham

Birmingham

Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...

, England.