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  Bentley 4.5 Litre 'Blower' Birkin Monoposto

  Article Image gallery (21) Specifications  
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Country of origin:Great Britain
Produced from:1929 - 1931
Numbers built:one-off
Designed by:Reid Railton
Author:Wouter Melissen
Last updated:June 25, 2012
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Click here to download printer friendly versionIt is a cruel twist of fate that the most famous Bentley built under W.O. Bentley's reign was the one he did not approve of and by far the least successful. The Naturally Aspirated four and six cylinder engined Bentleys dominated endurance racing, yet it is the supercharged 'Blower' Bentley that is best known today. W.O. Bentley's thoughts on the car were quite straightforward: "To supercharge a Bentley engine was to pervert its design and corrupt its performance." History proved him quite right as the Blower Bentley never won a major race. So why was the supercharged Bentley built in the first place?

The Blower Bentley was the brainchild of 'Bentley Boy' Henry 'Tim' Birkin, who was always looking for more power and speed. W.O.'s solution was to simply increase the size of the engine to improve performance, but that was not sufficient for Birkin. He convinced racing enthusiast the Hon Dorothy Paget to bankroll this conversion with his great charm. Birkin also received the blessing for fellow Bentley Boy, multiple Le Mans winner, diamant magnate and part owner of Bentley Woolf Barnato. Early in 1929 a small shop was set up in Welwyn by Birkin and production of the first supercharged Bentleys commenced.

Birkin got the ball rolling by commissioning Amherst Villiers to build him a Supercharger to bolt onto a completed 4.5 Litre Bentley. This followed the design of all Bentleys of the day that really only differed by the type of engine fitted and even these were built along the same lines. All of them had a single overhead camshaft with a beautiful four-valve per cylinder head. Birkin might have picked the smaller four cylinder engine, so he would not fall in the same class as the Works Bentleys, which used 6.6 Litre 'six'. The 'blower' was bolted to the crankshaft and was prominently visible on the nose of the car. Birkin's conversion certainly made a difference as the power was up from 100 bhp to a healthy 175 bhp, which was still down on the 200 bhp of the Speed Six used by the factory team.

The first Blowers were ready in the summer of 1929 and were entered by the Hon. Dorothy Paget in various races. It quickly became clear that the finely tuned internals of the Bentley engine were no match for the force of the Superchargers and the engines blew more often than not. When they did hold together, the Blower Bentleys were quite competitive with a number of second place finishes as the best result. Despite the mechanical problems, Barnato allowed Birkin to enter a team in the 1930 24 Hours of Le Mans. Their effort, not surprisingly, ended early with two 'blown' engines. The Le Mans entry came back to bite Bentley as they now had to build the agreed fifty examples needed for homologation.

At the end of the season, the Hon. Dorothy Paget withdrew her support for Birkin's team. She did hold on to the original prototype, which by then did not look anything like a standard Bentley. In 1929 the original four-seater 'Le Mans Tourer' body got severely damaged. Instead of rebuilding it, Birkin decided to have a special body fitted to race the car at the legendary Brooklands track. He called in the help of expert Reid Railton, who designed a purposeful off-set single seater body, which was mounted on the standard Bentley chassis. The engine was removed and carefully modified to be able to sustain the added stress of the Supercharger. Courtesy of purpose built pistons and a fully balanced crankshaft, power was up to 240 bhp.

Painted a striking blue and with the front brakes removed, the 'Birkin Monoposto' lined up for the opening race of the 1930 Brooklands season. That first weekend the 'Blower Bentley' recorded its first ever victory in a short race against a colourful mix of local and French racing cars. The next target for Birkin was the outer-lap record, which was held by Kaye Don in a supercharged V12 engined Sunbeam. At the Easter weekend Birkin broke the record by lapping at 135.33 mph. Don duly reclaimed the record later in the season. Birkin continued to race the Monoposto at Brooklands with some success before he had it further modified for the 1932 season. The engine was slightly enlarged and larger carburettors were fitted. It was sufficient to set a new record at 137.58 mph.

The Birkin Monoposto was retired from racing not much later and sadly Birkin himself followed suit. In 1933 he burned his arm on the hot exhaust of a Maserati Grand Prix car. He contracted blood-poisoning and died in hospital a few days later. The Hon. Dorothy Paget held on to the now red Monoposto for several years before selling it in 1939. After the War, the unique body was removed and replaced with a more conventional two-seater coachwork and extensively raced. Fortunately the Monoposto was preserved and eventually refitted on the car. One of the big problems was the surprisingly tight cockpit and some minor modifications were made in order for the owner to fit.

Eventually the first 'Blower' was acquired by great watchmaker and noted collector George Daniels. He continued to race and demonstrate the Monoposto for many more years. The unique machine will now be offered from his estate by Bonhams in their 2012 Goodwood Festival of Speed sale on June 29th. The estimate is available upon request and we expect this Bentley to become one of the most expensive cars to cross the block in 2012.

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  Article Image gallery (21) Specifications