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Bentley Speed Six

Bentley Speed Six

By Jack Nerad

Bentley Speed Six

Somewhere in Motor Racing Heaven W.O. Bentley must be smiling, because, after more than half a century, the company that bears his name (and his bother's) has been liberated from Rolls-Royce.  Of course, neither famed British marque is independent.  BMW owns Rolls-Royce, while Volkswagen is the caretaker of the Bentley brand, but there is no doubt that W.O. would prefer that circumstance to the previous administration in which Bentleys were little more than Rolls-Royces without the famed radiator shell.

W.O. (he hated his first name Walter) and Henry Royce battled for supremacy in the British luxury car market for more than a decade, and by an odd coincidence, both began their careers as railway apprentices. It is said that Bentley didn't care much at all for automobiles as a youth, and instead he pursued his dream of building big locomotives.  Only his hobby of motorcycle racing turned him from his passion for railroad engineering and moved him toward enthusiasm for internal combustion engines.

Bentley rode a Rex at Brooklands in 1909, and then climbed astride an American-built Indian as his racing exploits broadened. Finally, in 1910 he got the car bug, buying a Riley V-twin that year, and in the Teens he purchased two Sizaire-Naudins.

Quickly he let his railway apprenticeship fade, and for a time he worked as a mechanic at the National Motor Cab Company, and then he joined his brother, H.M., as a principal in a DFP automobile dealership in London.

Unlike most salespeople, he took a genuine interest in the mechanical aspects of the automobiles he was selling, and soon he was modifying them to produce better performance. One of his neatest tricks was to substitute lighter aluminum-copper alloy pistons for the DFP's standard-issue pistons. Later he reconfigured the car's camshaft for racing versions of the car as well.

The success with DFP was short-lived, however, because World War I intervened. In uniform, Bentley redesigned the French Clerget rotary aircraft engine, equipping it with (not surprisingly) aluminum pistons, and the re-done engine delivered significantly better performance. In his honor, the new engines he labored on were designated BR1 and BR2 (for "Bentley Rotary") and Bentley was promoted to lieutenant.

When the war was over and he and the service parted company, Bentley rejoined his brother in the car dealership. But after the success of his mechanical exploits while in the military, he yearned to do more than peddle cars; he wanted to build them.

In the summer of 1919 he formed a company called Bentley Motors Ltd to do just that. Teaming with Frank Burgess, a former Humber competition driver who had become well-known for drawing up the dual overhead cam engine that competed ably in the pre-war Tourist Trophy races, Bentley conceived a motor car that was quite advanced for the day.

Understandably, the chassis design owed much to Humber, but the engine was significantly different and the heart of the new car. Though the engine had but one camshaft (driven via a shaft from the crank), it did offer four valves per cylinder, quite a novelty in 1919. It used two plugs per cylinder, a more common practice at the time, and its crankcase was cast of light alloy rather than being a steel stamping for weight savings and rigidity. Block and head of the engine were cast in a piece, and the engine had an exceptionally long stroke of 5.8-inches and a 3.1-inch bore. (This odd combination of bore and stroke was no doubt influenced by British tax laws which calculated taxable horsepower by extrapolating from the engine's bore, ignoring the stroke altogether.)

Bentley broke with tradition by calling his creation a "3-Litre." At that time it was common practice for British auto manufacturers to label their cars with their horsepower (the Rolls-Royce Silver Ghost was the officially called the 40/50, for example), but the calculated horsepower for the Bentley was just 15.9, which would have been marketing suicide and was inaccurate on top of it. Actual horsepower from the sophisticated engine was more than double that figure.

Aside from the engine, the Bentley 3-Litre was conventional in design. Substantial girders joined by four cross members served as the frame. Semi-elliptical springs were used at all four corners, and the original wheelbase was 117.5-inches.

The 3-Litre used a four-speed gearbox operating through a rather un-modern cone-type clutch. The right-hand mounted gearbox lever was most often affixed exterior of the bodywork in what was obviously a right-hand-drive vehicle. Until 1924, two-wheel brakes were used, and then the Bentley works added drums to the front wheels as well.

The sad fact that dogged Bentley Motors Ltd throughout its life was its weak financial situation. The company was started on less than $50,000, and it approached automobile manufacture with a cottage industry style. The catch-as-catch-can nature of his manufacturing operation didn't stop Bentley from going racing, however. In 1922 his three-car team won the team prize at the well-respected Tourist Trophy race on the Isle of Man, with individual cars finishing second, fourth and fifth. This smashing success against the best from England and the Continent immediately grabbed Bentley Motors some much-needed recognition.

The coup on the Isle of Man was followed two years later by John Duff's victory in the 24-Hours of Le Mans, but despite racing successes, Bentley's sales trickled along -- 21 in 1921, 122 in 1922, 204 in 1923 and 402 in 1924.  Still Bentley's success in motor racing, including what might be the most fabled Le Mans victory of them all -- the win by the 4-Litre in 1927 after a crash had seemingly put it out of the race - gave the company panache far outstripping its sales numbers.  One has to remember in that era, cars very much like the Le Mans-winning racers could be bought straight off the showroom floor and driven day-to-day, so the marque's dominance was a huge marketing tool in moneyed circles.

This esteemed clientele prevailed upon Bentley to build a longer wheelbase version of the 3-Litre that would accommodate more elaborate bodywork. The result of their lobbying was a 130-inch wheelbase chassis, though that, too, was most often outfitted with a four-seater open touring body accented by cycle fenders.

Even as the 3-litre was enjoying success, W.O. Bentley was toying with the idea of building a more refined six-cylinder car, and he had a prototype built with a 4.5-liter in-line six-cylinder engine built in time for the Le Mans race in 1924.  But the car wasn't built to race in the event; it was built so that W.O. could drive it to and from the race course.  While in France, the story goes, Bentley was piloting this "one-off" when he encountered another prototype, the Rolls-Royce Phantom I.  The two engaged in some impromptu competition, and though the Bentley prototype held its own, W.O. became convinced that more displacement was needed to preserve his winning margin.

The result of those musings was the Bentley 6-Litre, a car with a powerplant of 6597 cc.  In spite of Bentley's affection for racing the new model wasn't meant to be a racer.   Instead, it was designed to provide the company's luxury-seeking clients with a platform for big, comfortable saloons (sedans) and town cars.  And from its introduction in 1925, through Bentley's continued success at Le Mans in 1927 and 1928, that's how things stood until 1929.

Then, with the stock market booming but a crash looming, W.O. Bentley decided to transform the rather staid 6-Litre "Standard Six" into the performance-oriented "Speed Six," and yet another legendary model.  Interestingly, the transformation was accomplished with little more than standard hot-rodding techniques.  The compression ratio was boosted and the Standard Six's Smiths carburetor was replaced by a pair of SUs.  Those simple modifications and the substitution of a "hotter" camshaft were all that were necessary to bump the engine from an easy-running 140 horsepower to a still largely under-stressed 180 hp.  In race trim, with an even more exotic camshaft, the engine was said to produce 200 horsepower.  But of equal importance, especially for Le Mans-style endurance racing, was the fact that the engine could run hour after hour at speed without over-taxing itself.

This combination proved so successful in the 1929 running of Le Mans that the Bentley Speed Sixes won in a cakewalk.  In fact, they were so far ahead of their closest rivals that W.O. Bentley insisted that they slow down.  He wasn't worried about their durability; he simply didn't want to demonstrate to his competitors - especially Mercedes-Benz - just how superior his cars were.

That bit of genius paid off the following year when the self-same Speed Six that had won in 1929 (piloted by Woolf Barnato and Henry "Tim" Birkin) took first place again (this time with Barnato and Glen Kidston sharing driving duties.)   Two factors keyed the victory.  First, the rival Mercedes-Benz team had used the 1929 Speed Six Le Mans times as their performance bogey, not realizing that the cars had slowed considerably once they were certain the game was won.  And, second, the Speed Sixes were so durable that all their drivers had to do was wait for the Mercedes-Benzes to break.

Unfortunately, the stock market debacle and ensuing worldwide Depression also forced Bentley to the breaking point.  W.O. Bentley's final stab at the luxury car market was his substantial 8-Litre. Essentially a bored-out version of the Speed Six, the 7982 cubic centimeter engine produced up to 225 horsepower, but even as the car was being introduced receivership was just days away.

After Rolls-Royce absorbed his company, Bentley moved on to Lagonda, where he designed several excellent engines, but never again was he able to capture the magic that was the legendary Speed Six.


Autoswalk.com has partnered with Studio One Networks to provide you with the history of the world's greatest cars. All of the pictures and information are copyright of Studio One Networks and Autoswalk.com, and are brought to you by Jack Nerad for Driving Today.

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