The Variomatic is also used in today's motorscooters. In testing there were problems with the heat production. A version with a differential was developed by Williams in the 1993 Williams FW15C CVT Formula One car, but it was banned before being raced. Later cars, the 46, 66, and Volvo variants were fitted with a differentially geared axle. Low-speed handling in icy conditions was interesting as the system tended to drive the car forward against the influence of the steered wheels. This led to rapid tire wear and placed stress on other transmission components. Although each belt could settle (independent of the other) into its optimum position, thus allowing for wheel speed variation, the system was slow to operate and depended on the pulleys being turned. There were several disadvantages that accompanied the lack of a true differential gear. This results in unusually good traction characteristics, which were also a reason for the successes of the DAFs in rallies. With the DAF 600 - 55, each rear wheel was propelled individually by a pair of conical drums and drive belt with the effect of a limited-slip differential: if a drive wheel on slippery road revs up, the other wheel can still transfer the full torque. Problems playing this file? See media help. As a result of the change in the distance of the conical drums in both pulleys, the diameters and so also the reduction ratio changes continuously. Between the two pulleys runs a drive belt. The distance between the drums is controlled by the engine vacuum in the inlet manifold and engine RPM, through centrifugal weights inside the drums. The final drive has two pulleys with moveable conical drums. VDT continued the development of the CVT and introduced a push-belt system in the Ford Fiesta and Fiat Uno. When DAF was acquired by Volvo in 1974, the Variomatic patents were transferred to a company called VDT (Van Doorne Transmissie), later acquired by Bosch in 1995. Manual transmission remains dominant in Europe. Thus, these very cheap and simple cars were the 'formula one' in this competition. 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. Reversing īecause the system does not have separate gears, but one (continuously shifting) gear and a separate 'reverse mode' (as opposed to reverse gear), the transmission works in reverse as well, giving it the side effect that one can drive backwards as fast as forwards. The Variomatic was introduced on the DAF 600.īecause most of the time the engine runs at its most economical speed, the fuel consumption of this car was acceptable, although the fuel efficiency of any mechanical CVT is about 70% (then) to 75% now (Bosch) (now). The Variomatic was introduced by DAF in 1958, also putting an automatic gearbox in the Netherlands for the first time. In theory, this always produces the optimum torque. The Variomatic was the first commercially successful CVT (as opposed to shifting between separate gears). These are synchronized so that the belt always remains at the same optimal tension. 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. Variomatic is the continuously variable transmission (CVT) of the Dutch car manufacturer DAF, originally developed by Hub van Doorne. The rear wheels are driven by separate belts, eliminating the need for a differential. The larger green drums on the left contain the vacuum mechanism that controls the variable pulleys. Belt and pulleys of a Van Doorne transmission Variomatic transmission and rear axle. For the valve timing system, see Valvematic.
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