The Bentley 6½ Litre and the high-performance Bentley Speed Six were

rolling chassis A rolling chassis is the chassis without bodywork of a motor vehicle ( car, truck, bus, or other vehicle), assembled with suspension and wheels. Heavy vehicles Separate chassis remain in use for almost all heavy vehicles ranging from pickup ...

in production from 1926 to 1930. The Speed Six, introduced in 1928, would become the most successful racing Bentley. Two Bentley Speed Sixes became known as the ''

Blue Train Bentley The Blue Train Races were a series of record-breaking attempts between automobiles and trains in the late 1920s and early 1930s. It saw a number of motorists and their own or sponsored automobiles race against the ''Le Train Bleu'', a train that ra ...

s'' after their owner

Woolf Barnato Joel Woolf BarnatoPronounced Barnatoo – from Barnett too (27 September 1895 – 27 July 1948) was a British financier and racing driver, one of the "Bentley Boys" of the 1920s. He achieved three consecutive wins out of three entries in the ...

's involvement in the

Blue Train Races The Blue Train Races were a series of record-breaking attempts between automobiles and trains in the late 1920s and early 1930s. It saw a number of motorists and their own or sponsored automobiles race against the '' Le Train Bleu'', a train that r ...

of 1930.

Background

By 1924 Bentley had been in business for five years. He decided to build a larger chassis than the 3 Litre, with a smoother, more powerful engine. The new chassis would be more suitable for the large, heavy limousine bodies that many of his customers were then putting on his

sports car A sports car is a car designed with an emphasis on dynamic performance, such as handling, acceleration, top speed, the thrill of driving and racing capability. Sports cars originated in Europe in the early 1900s and are currently produced by ...

chassis. The resulting car would be more refined and better suited for comfortable general motoring.

Prototype race

Bentley built a

development mule A development mule (test mule, or simply mule) in the automotive industry is a testbed vehicle equipped with prototype components requiring evaluation. They are often camouflaged to cover their designs. Application Mules are necessary because a ...

with a 4¼ L straight-six engine derived from the 3 Litre's four cylinder engine. To disguise the car's origin, it had a large, wedge-shaped radiator and was registered as a "Sun". The chassis was given a large very light weight Weymann-type tourer body built by

Freestone and Webb Freestone and Webb were English coachbuilders who made bodies for Rolls-Royce and Bentley motor cars but also built bodies on other chassis including Alfa Romeo, Packard, and Mercedes-Benz. The business was founded in 1923 by V.E. Freestone and ...

W. O. Bentley Walter Owen Bentley, MBE (16 September 1888 – 13 August 1971) was an English engineer who founded Bentley Motors Limited in London. He was a motorcycle and car racer as a young man. After making a name for himself as a designer of aircraft a ...

combined one of his road tests of the Sun with a trip to see the 1924 French Grand Prix in

Lyon Lyon,, ; Occitan language, Occitan: ''Lion'', hist. ''Lionés'' also spelled in English as Lyons, is the List of communes in France with over 20,000 inhabitants, third-largest city and Urban area (France), second-largest metropolitan area of F ...

. On his return trip to the ferry at

Dieppe Dieppe (; Norman: ''Dgieppe'') is a coastal commune in the Seine-Maritime department in the Normandy region of northern France. Dieppe is a seaport on the English Channel at the mouth of the river Arques. A regular ferry service runs to N ...

, W. O. encountered another disguised car at a

three-way junction A three-way junction (or three-way intersection) is a type of intersection (road), road intersection with three arms. A Y junction (or Y intersection) generally has three arms of equal size coming at an acute angle, acute or obtuse angle to each ...

. W. O. and the

Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...

test driver recognized each other and began racing each other along the '' routes nationales''. This street race continued until the Rolls-Royce driver's hat blew off and he had to stop to retrieve it. The Sun's tyres were heavily worn when W.O. got to the ferry at Dieppe.

6½ Litre

Realizing from the impromptu race that the Sun had no performance advantage over Rolls-Royce's latest development, W. O. increased the bore of his six-cylinder engine from to . With a stroke, the engine had a displacement of 6.6 L () Like the four-cylinder engine, Bentley's straight-6 included overhead camshaft, 4 valves per cylinder, and a single-piece engine block and cylinder head cast in iron, which eliminated the need for a

head gasket In an internal combustion engine, a head gasket provides the seal between the engine block and cylinder head(s). Its purpose is to seal the combustion gases within the cylinders and to avoid coolant or engine oil leaking into the cylinders. Leak ...

. In base form, with a single Smiths 5-jet carburettor, twin ignition magnetos, and a compression ratio of 4.4:1, the Bentley 6½ Litre delivered at 3500 RPM. Although based on the 3 Litre's engine, the 6½ engine incorporated many improvements. The 3 Litre's cone-type clutch was replaced by a dry-plate design that incorporated a clutch brake for fast gear changes, and the car had power-assisted four-wheel brakes with finned drums. The front brakes had 4 leading shoes per drum. By operating a patented compensating device, the driver could adjust all four brakes to correct for wear while the car was moving, which was particularly advantageous during races. A variety of

wheelbase In both road and rail vehicles, the wheelbase is the horizontal distance between the centers of the front and rear wheels. For road vehicles with more than two axles (e.g. some trucks), the wheelbase is the distance between the steering (front ...

s were provided ranging from , the most popular being 150 inches.

Speed Six

The Bentley Speed Six chassis was introduced in 1928 as a more sporting version of the Bentley 6½ Litre. With a single-port block, two SU carburettors, a high-performance camshaft, and a compression ratio of 5.3:1, the Speed Six's engine produced at 3500 rpm. The Speed Six chassis was available to customers with wheelbases of , , and , with the 138 inch wheelbase being most popular. The

Criminal Investigation Department The Criminal Investigation Department (CID) is the branch of a police force to which most plainclothes detectives belong in the United Kingdom and many Commonwealth nations. A force's CID is distinct from its Special Branch (though officers of b ...

of the

Western Australia Police The Western Australia Police Force, colloquially WAPOL, provides police services throughout the state of Western Australia, an area of 2.5 million square kilometres, the world's largest non-federated area of jurisdiction, with a population ...

operated two saloon-bodied examples as patrol cars. In March 1930, Barnato raced against the Blue Train in a Speed Six with H. J. Mulliner saloon coachwork, reaching his club in London before the train was due in the station at Calais. It had generally been believed that the car in the race was a Gurney Nutting Sportsman Coupé, but that coupé was delivered to Barnato in May 1930, more than a month after the race.

Factory racing cars

The racing version of the Speed Six had a wheelbase of and an engine with a compression ratio of 6.1:1 that produced at 3500 rpm. Successful in racing, these cars won the

24 Hours of Le Mans The 24 Hours of Le Mans (french: link=no, 24 Heures du Mans) is an endurance-focused sports car race held annually near the town of Le Mans, France. It is the world's oldest active endurance racing event. Unlike fixed-distance races whose ...

in 1929 and 1930 with

Bentley Boys The Bentley Boys were a group of wealthy British motorists who drove Bentley sports cars to victory in the 1920s and kept the marque's reputation for high performance alive. In 1925, as the marque foundered, Bentley Boy Woolf Barnato bought the ...

drivers "Tim" Birkin, Glen Kidston, and

, the chairman of Bentley Motors.

Production

* 6½ Litre: 362 * Speed Six: 182

Gallery

File:Blue Train Bentley 6½-litre saloon.jpg,

's Speed Six H. J. Mulliner saloon, in which he raced against the Blue Train File:1930 Bentley Speed Six Nutting Coupe (3828597253).jpg, 1930 Gurney Nutting Sportsman Coupé, often believed to be the car that raced the Blue Train was actually delivered two Barnato weeks after the race. Photo from 2009 Concours. File:1930 Bentley Speed Six Nutting Coupe (3828596647).jpg, Side view File:1928_Bentley_6½_Litre_Tourer_KD2111,_VandenPlas_lhs.jpg, Bentley 6½ Litre Tourer File:1929 Bentley "Speed Six" IMG 9625 - Flickr - nemor2.jpg, Bentley Speed Six drophead coupé File:Bentley Speed Six.JPG, Bentley Speed Six prepared for racing File:Bentley 6,5-Litre Tourer.jpg, Bentley 6½-Litre Tourer File:Bentley 6,5-Litre Speed Six Tourer 1930.jpg, Bentley 6½-Litre Speed Six Tourer 1930

Notes

References

;Print * * * * * * ;Online * * * {{Bentley Cricklewood timeline 1921 to 1931 6 Cars introduced in 1926 1930s cars 24 Hours of Le Mans race cars Le Mans winning cars