Variomatic

Automotive transmissions
Manual
Automatic / Semi-automatic
"V-matic" redirects here. For the valve timing system, see Valvematic.
A pair of conical pulleys, with a flat belt running between them. The lower pulley is formed from two separate movable cones. In the current configuration, the cones have been moved apart so the belt "falls" into space between them. By moving the cones closer, the belt is forced to ride higher on the sides of the cones, changing the pulley ratio.
Belt and pulleys of a Van Doorne transmission
Variomatic transmission and rear axle. The larger green drums on the left contain the vacuum mechanism that controls the variable pulleys. The rear wheels are driven by separate belts, eliminating the need for a differential.

Variomatic is the continuously variable transmission (CVT) of the Dutch car manufacturer DAF, originally developed by Hub van Doorne.[1] 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.

  1. ^ "Transmissions drove Hub van Doorne's innovative spirit", February 2009, autonews.com