The history of the double clutch

Whether it’s called DSG, DCT or Powershift, and whether it uses wet or dry discs, the dual clutch transmission at full throttle has taken its place in the market over the past decade. For the origins of the DCT we have to go to France of the interwar period. In the early 1930s, engineer Adolphe Kégresse left his employer Citroën to establish himself as an independent engineer. His first project is the AutoServe transmission, a two-clutch gearbox. One clutch operates the even gears, the other the odd.

Citroën Traction Avant

In a nod to his old employer, the system is tested in a Traction Avant and patented in July 1939. Because the system is more expensive than the conventional machine and the Second World War is on the verge of breaking out, the project foundered prematurely. But the egg has been laid. At the same time, Professor Rudolph Franke at Darmstadt University of Applied Sciences is working on a similar system and applies for a patent in March 1940. Nothing else happens here either.

From analog to digital

It was not until forty years later that the idea was dusted off in England. At the brake and clutch manufacturer AP a project started in 1980 under the leadership of Harry Webster (previously at Triumph the spiritual father of the TR2 to the TR5 and the Spitfire). Webster and his people build several prototypes, including in a Ford Fiesta. Driven by analog circuits it doesn’t exactly become a compact solution, the project leads to nothing. Although nothing … the principle is again in the spotlight and is being picked up in various places.

Porsche 956

Porsche 956

Also at Porsche. Not directly for street use, but for racing, and not unimportantly: digital. In December 1983, works driver Vern Schupan qualified for the first time in a Porsche 956 equipped with a PDK transmission (Porsche Doppel-Kupplung), on a 12th starting position. The system does not yet work flawlessly, which is reason for the team to drive with a conventional gearbox again during the race. In 1984 the 956 with PDK runs thousands of test kilometers on the test track in Weissach, only to be used in a race for the first time in September that year with Jacky Ickx at the wheel. However, Jacky will retire after just one lap with clutch problems.

Porsche does not give up and 1985 will be a test year, not only with its own sports cars, to tackle it thoroughly, the Audi rally team is also involved in the story. As a shake down for the RAC Rally in England, Walter Röhrl managed to win the Semperit rally (a national event) in Austria in November with a PDK-equipped Sport Quattro E2 in Austria. However, two weeks later – when it comes to the world championship – Röhrl drops out. Audi continues in 1986 with the familiar six-speed gearbox. However, 1985 provides so much information for Porsche that in April 1986 Hans-Joachim Stuck and Derek Bell immediately won the opening race of that season at Monza with a Porsche 962 C PDK, a trick that was repeated several times in 1986 and 1987. However, Le Mans – the holy grail of sports car racing – will never be won with a PDK car and after 1987 the curtain seems to be falling for the dual clutch gearbox.

Indeed, it seems. At the end of the 1990s, transmission manufacturer Borg Warner picked up the idea and made it suitable for mass production in compact cars thanks to modern computer technology. The first customer for what Borg Warner calls the DualTronic is Volkswagen, which presents it in 2003 as DSG (Direktschaltgetriebe, Direct Shift Gearbox) in the Golf R32. The rest is history.

This article originally appeared in AutoWeek Classics issue 7 of 2014.

Source: AutoWeek by

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