CONTINUOUSLY VARIABLE TRANSMISSION
While many people view the Continuously Variable Transmission (CVT) as a fairly recent development, its history is almost as long as that of the motorcar. In North America, H. C. Spaulding patented an infinitely variable gearbox in 1897, which utilised a drive belt and a pair of conical pulleys. By manipulating a series of levers, the driver could alter the gearing, by varying the belt’s position infinitely between the larger, or smaller, diameter portions on the pulley. The system found favour in industrial machinery and, while some sources acknowledge the intention for a motorcar application, no examples are known to have been made.
Meanwhile, in France, Gustave Fouillaron used a pair of variable pulleys to power the vehicle that bore his name in 1901. Yet, the system still had to be operated by hand, making it not a true ‘automatic’. In addition, the restricted range of materials available was not conducive to long belt life. Consequently, other automatic transmissions were developed, especially those that utilised epicyclical gear trains, with which many motorists today are familiar.
Small is beautiful
By the 1950s, epicyclical geared hydraulic automatic transmissions were heavy and expensive. Additionally, their limited number of gear ratios and power-sapping internals made them unsuitable for low-powered economy vehicles. Dr Hubert. J. van Doorne rescued the belt drive transmission concept from obscurity and, within four years, made it not just fully automatic but also dependable. The unconventional transmission utilised a pair of pulleys, split into two halves that slide towards, or apart. A rubber reinforced toothed belt was mounted between each pulley, which ran up and down the tapered internal surfaces. DAF’s Variomatic won the company many loyal customers but they could not save the company from being taken over by Volvo during the 1970s. The safety-obsessed Swedes refined the Dutch system and renamed it ‘CVT’.
Changes included removing the entirely logical gear lever forward position to move forward and rearward to go backwards and replacing
