Variomatic

Variomatic is the continuously variable transmission developed for the Dutch automobile manufacturer DAF. Rather than selecting among a fixed set of gears, the system changes its ratio continuously through two pairs of conical pulley halves connected by V-shaped belts. Moving the pulley cones closer together or farther apart changes the effective diameter at which the belt runs, allowing the transmission to adapt the ratio progressively to vehicle speed, engine speed, load, and road conditions. The system was developed from earlier variable-speed transmission ideas and is associated with engineer Christoffel Sellenraad at DAF. DAF introduced it commercially in 1958 with the DAF 600, making the car one of the earliest successful production applications of a fully automatic continuously variable transmission. It also represented an important milestone in Dutch motoring because it brought automatic transmission technology into the Dutch passenger-car market at a time when manual gearboxes remained dominant across Europe. A major attraction of Variomatic was its mechanical simplicity from the driver's perspective. The driver did not select individual forward gears; the pulleys and belts continuously established an appropriate ratio. The arrangement could keep the engine operating near an efficient speed and delivered smooth acceleration without perceptible gear changes. Its limitations included belt wear, relatively modest efficiency compared with later designs, mechanical stresses, and sensitivity to operating conditions. Early DAF systems also used separate belt paths for the rear wheels rather than a conventional differential arrangement. This could provide useful traction on slippery surfaces, but it also contributed to tire wear, driveshaft stress, and unusual low-speed behavior. Later DAF and Volvo-derived vehicles adopted differentially geared axles. The transmission became particularly well known through DAF cars used in rallying and through the unusual ability of Variomatic-equipped vehicles to travel backward at speeds comparable to their forward speed. Since the mechanism had a continuously variable forward range and a separate reverse mode rather than a conventional reverse gear, DAF vehicles were famously separated from other cars in historical Dutch backward-driving competitions. After Volvo acquired DAF in 1974, the relevant transmission patents and development activities moved into Van Doorne Transmissie, commonly associated with the abbreviation VDT. The business was acquired by Bosch in 1995. Development subsequently moved toward more durable push-belt continuously variable transmissions, including systems supplied for vehicles such as the Ford Fiesta and Fiat Uno. The principle behind Variomatic also became widespread in scooters, where continuously variable belt-and-pulley transmissions have been standard on many common models since the 1980s. Variomatic therefore occupies an important place in automotive engineering history. It was not merely a DAF model feature but an early commercially successful expression of the CVT concept. Modern CVTs use electronic controls and stronger steel link belts rather than the original rubber belts, but they retain the central idea of changing the working diameters of paired pulleys to obtain a continuously variable ratio.

The engineering lineage of Variomatic reaches back to earlier variable-speed transmission concepts. A variable pulley arrangement was patented by Milton Reeves in 1889, while a related system associated with Fouillaron was patented in 1898. Fouillaron later applied an extendable-pulley transmission to a 1904 Type G vehicle powered by a De Dion 6-horsepower single-cylinder engine. These early mechanisms demonstrated the feasibility of varying the effective diameter of a pulley, although they were not equivalent to the mature automotive Variomatic system. Dutch manufacturer DAF acquired and further developed the underlying concept for passenger cars. Engineer Christoffel Sellenraad is associated with the development of the DAF system, which used two pairs of movable conical pulley faces and V-belts. The pulley spacing changed in response to engine vacuum, engine speed, and centrifugal mechanisms. As the cones moved, the belts shifted inward or outward, continuously changing the transmission ratio while maintaining appropriate belt tension. DAF launched Variomatic in 1958 in the DAF 600. The car established the system as one of the first commercially successful continuously variable transmissions and introduced a fully automatic gearbox to the Dutch passenger-car market. The arrangement offered smooth, stepless acceleration and could allow the engine to operate near an economical speed. Its mechanical efficiency was limited by the technology and materials of the period, but its drivability and novelty gave DAF a distinctive position. Early DAF cars used a separate belt-and-pulley drive arrangement for each rear wheel. This could act in a limited-slip-like manner because a slipping wheel did not necessarily prevent the other wheel from transmitting torque. The design contributed to DAF's traction performance and rallying reputation, but the absence of a conventional differential also created disadvantages. The system could be slow to accommodate wheel-speed differences, contributed to tire wear and transmission stress, and was associated with broken driveshafts. Later DAF models, including the 46 and 66, and Volvo variants adopted axles with conventional differential gearing. The transmission's reverse behavior became one of its best-known characteristics. Because the system did not use a conventional reverse gear, a DAF equipped with Variomatic could travel backward at a speed comparable to its forward speed. This led to a separate class for DAF cars in the former Dutch annual backward-driving world championship, where ordinary cars could not compete on equal terms. When Volvo acquired DAF in 1974, Variomatic patents and related development operations were transferred to Van Doorne Transmissie, or VDT. The company continued to develop continuously variable transmission technology and later moved from the original pulled rubber belts toward steel push belts. The resulting technology was supplied for applications including the Ford Fiesta and Fiat Uno. Bosch acquired VDT in 1995, continuing the industrial development of CVT systems. The basic Variomatic principle also became highly influential outside passenger cars. Belt-and-pulley CVTs became standard equipment on many motor scooters, especially from the 1980s onward, and specialist companies developed replacement and tuning components for scooter applications. Modern automotive CVTs from several manufacturers use electronic controls and steel link belts, making them more durable and controllable than the original DAF arrangement while preserving its central variable-pulley architecture. Variomatic is consequently best understood as both a historic DAF transmission brand and a formative production implementation of the modern CVT idea.

• 1995

  VDT acquired by Bosch

  [1]Variomaticen.wikipedia.org

  Bosch acquired Van Doorne Transmissie, the company that had continued development of the DAF-derived CVT technology.

• 1974

  Transfer to the Volvo era

  [1]Variomaticen.wikipedia.org

  Following Volvo's acquisition of DAF, Variomatic patents and associated transmission activities were transferred into Van Doorne Transmissie.

• 1958

  Commercial introduction on the DAF 600

  [1]Variomaticen.wikipedia.org

  DAF introduced Variomatic on the DAF 600, creating one of the first commercially successful production CVTs and bringing automatic transmission to the Dutch car market.

• 1904

  Fouillaron Type G application

  [1]Variomaticen.wikipedia.org

  A Fouillaron Type G vehicle used an extendable-pulley transmission, demonstrating an early automotive application of variable-ratio drive technology.

• 1898

  Fouillaron variable-transmission patent

  [1]Variomaticen.wikipedia.org

  A related variable-pulley system associated with Fouillaron was patented, providing another historical precursor to later continuously variable mechanisms.

• 1889

  Early variable-pulley patent

  [1]Variomaticen.wikipedia.org

  Milton Reeves patented an early variable-speed pulley transmission concept, contributing to the broader engineering background from which later CVTs developed.

An early, commercially successful automatic continuously variable transmission positioned around smooth stepless operation, mechanical simplicity, and the ability to keep an engine near an efficient operating speed.

• Automotive continuously variable transmission · 1958

  DAF 600 Variomatic

  The DAF 600 transmission was the first major production application of Variomatic. It used V-belts running between pairs of movable conical pulleys. By changing the spacing of the cones, the system continuously altered the working diameter of each pulley and therefore the final drive ratio. The driver received automatic, stepless acceleration rather than conventional gear changes. In its early form, the system used separate belt drives for the rear wheels, a layout that influenced traction behavior and distinguished it from later differential-based designs.

• Automotive continuously variable transmission

  DAF and Volvo Variomatic systems

  Variomatic systems were used across later DAF passenger cars and Volvo models derived from DAF programs. Later applications addressed some of the early system's handling and durability limitations by incorporating a conventional differential axle. The transmissions retained the smooth, continuously variable operating principle while adapting it to broader passenger-car use.

• Automotive transmission technology

  Van Doorne and Bosch push-belt CVT systems

  After the transmission activities moved to Van Doorne Transmissie and later Bosch, development progressed from the original rubber belts toward steel link push belts. Applications included the Ford Fiesta and Fiat Uno. These systems were technologically more durable and were generally controlled electronically, but they continued to use the variable-pulley principle established by Variomatic.

• Scooter transmission · 1985

  Scooter Variomatic-type CVT

  The same general belt-and-pulley approach became standard on many motor scooters from the 1980s onward. Scooter CVTs use variable pulleys and centrifugal control to provide automatic ratio changes without a manual gearbox. Specialist suppliers have offered replacement and tuning clutches, variators, and related components for common small-displacement scooter engines.

• 1995

  Bosch acquisition of Van Doorne TransmissieM&A

  Background

  Van Doorne Transmissie had continued developing DAF-derived continuously variable transmission technology.

  Action taken

  Bosch acquired Van Doorne Transmissie and its CVT development activities.

  Aftermath

  The technology entered Bosch's transmission portfolio and continued through more modern steel-belt CVT designs.

  Source

• 1974

  Transfer of transmission activities after Volvo's DAF acquisitionM&A

  Background

  Volvo acquired DAF, bringing the DAF passenger-car and transmission businesses into a new corporate structure.

  Action taken

  Variomatic patents and related development work were transferred to Van Doorne Transmissie.

  Aftermath

  The technology continued to be developed outside the original DAF organization and later evolved into push-belt CVT systems.

  Source

• 1958

  Launch of the Variomatic transmissionProduct launch

  Background

  DAF sought to offer an automatic transmission that avoided the complexity and interruption associated with fixed-ratio gear changes.

  Action taken

  The company introduced its belt-and-variable-pulley CVT on the DAF 600.

  Aftermath

  The launch made Variomatic one of the first commercially successful automotive CVTs and established DAF's distinctive transmission identity.

  Source

1. 1Variomaticen.wikipedia.org