Van Doorne transmission

Variomatic is the continuously variable transmission (CVT) of the Dutch car manufacturer DAF, originally developed by Hub van Doorne: It is a stepless, fully automatic transmission consisting of a "V" shaped drive belt and two pulleys, each of two cones, whose effective diameter can be changed so that the "V" belt runs nearer the spindle or nearer the rim, depending on the separation of the cones. These are synchronized so that the belt always remains at the same optimal tension.

It was the first commercially successful CVT (as opposed to shifting between separate gears). In theory, this always produces the optimum torque. The Variomatic was introduced by DAF in 1958, also putting an automatic gear box in the Netherlands for the first time. The variomatic was introduced on the DAF 600.

Due the fact the engine runs most of the time in its best fuel economic speed, the fuel consumption of this car was at accepted level, although the fuel efficiency of any mechanical CVT is about 70 (then) to 75% today (Bosch).

Because the system does not have separate gears, but one (continuously shifting) gear and a separate 'reverse mode' (as opposed to a reverse gear), the gear works in reverse as well, giving it the interesting side effect that one can drive backwards as fast as forwards. As a result, in the former Dutch annual backward driving world championship, the DAFs had to be put in a separate competition because no other car could keep up. Thus, these very cheap and simple cars were the 'formula one' in this competition.

Manual transmission remains dominant in Europe. When DAF was taken over by Volvo, the Variomatic patents were transferred to a company called VDT (Van Doorne Transmissie), later taken over by Bosch. VDT continued development of the CVT and introduced a pushbelt system in the Ford Fiesta and Fiat Uno. Audi reintroduced an improved version of the variomatic in 2000 under the name multitronic. This system uses a metal belt and lacks a limit to the number of gears available, switching between them without noticeable shocks. These metal drive belts are the most important part of CVT. There are three factories producing these belts, the Bosch factories in Tilburg (the Netherlands), Ho Chi Minh City (Vietnam), and San Luis Potosí (Mexico). It is used in over 40 car models, these days even including expensive brands like Mercedes-Benz.

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Wikipedia