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The manual transmission
Ever since the first automobiles, the manual gearbox has been to the car what the derailleur is to the bicycle. Role, operation, design, calculation of the ratios and all the types of manual transmissions are studied here. Publication date : December 2003. Author : François Dovat
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Continuously Variable Transmissions (CVTs)
The reciprocating internal combustion engines which substituted the steam engines brought a problem for road (and railway) traction: they do not develop any torque at rest. Ever since, a constant obsession of engineers and inventors has been to conceive a system of mechanical drive able to progressively and continuous vary the transmission ratio, in order to allow the engine to spin always at the most favorable revs. Countless systems have been imagined and even tested, but the "natural selection" has let survive very few of them. Publication date : November 2004. Author : François Dovat
Pictures : LuK, ZF, Turbo-Trac, GIF, Nissan, Torotrak, Ford, GM, Napier. Access by securized micro-payment system or Credit Card Document access. | |
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Double clutch transmissions
(DSG/VW-Audi, PSG/LuK, PDK/Porsche /Kégresse and others) With a conventional mechanical transmission gear shifts require an interruption of the connection between engine and gearbox which not only harms the comfort and the performances of the vehicle, but also represents a loss of kinetic energy. A shift under load, without disruption of the torque transmission is thus desirable. This is commonly performed by automatic transmissions composed of a hydrodynamic torque converter associated to planetary gear trains. But these automatic transmissions are complex, expensive and their efficiency remains lower than that of manual mechanical gearboxes. The simple and effective twin clutch concept invented by a brilliant French engineer before WW II has at last been developed and its mass production launched by VW and Audi. The competitors certainly do not intend to be left behind… Publication date : December 2003. Author : François Dovat
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The Torotrak IVT
The biggest number is almost nothing compared to the infinite and it would be better to take great care about the use of this term. If we speak about "Continuously Variable Transmission" (CVT) for a transmission which shifts ratios uninterruptedly within a range closed at both ends, we can therefore save the use of the expression "Infinitely Variable Transmission" (IVT) for a system providing an infinite variation range. Today, the Torotrak IVT easily handles the 475 Nm of the Ford 5.4 liters V8, providing a fuel economy improvement of some 20 % against the standard automatic transmission, as well as a better drivability. When shall we be able to buy a car with such an ideal transmission, which the author was one of the first journalists to test drive? Publication date : November 2003. Author : François Dovat
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