Variomatic
Variomatic is the stepless, fully automatic transmission of the passenger car manufacturer DAF.
The final drive has two pulleys with moveable conical drums. The distance between the drums is controlled by the engine vacuum in the inlet manifold and engine RPM, through centrifugal weights inside the drums. Between the two pulleys runs a drive belt. As a result of change in the distance of the conical drums in both pulleys, the diameters and so also the reduction ratio changes continuously.
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. This results in unusually good traction characteristics, which were also a reason for successes of the DAFs in rallies.
Today the Continuously Variable Transmission (CVT) works according to the same principle. Rather than rubber drive belts, the modern transmission is made much more durable by the use of steel link belts. The CVT is available in cars such as Audi, Honda and the Mini Cooper.
