Editing Variomatic

{{short description|Continuously variable transmission by Dutch carmaker DAF}}
{{Transmission types}}
{{Redirect|V-matic|the valve timing system|Valvematic}}
[[Image:Pivgetriebe.png|thumb|right|Belt and pulleys of a Van Doorne transmission|alt=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.]]
[[File:DAF Hinterachsantrieb.jpg|thumb|right|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 (mechanics)|differential]].]]

'''Variomatic''' is the [[continuously variable transmission]] (CVT) of the [[Netherlands|Dutch]] car manufacturer [[DAF Trucks|DAF]], originally developed by [[Hub van Doorne]].<ref>[http://www.autonews.com/article/20090202/ANE03/901319983/1193 "Transmissions drove Hub van Doorne's innovative spirit"], February 2009, autonews.com</ref> It is a stepless, fully-[[automatic transmission]], consisting of a V-shaped drive-belt, and two [[pulley]]s, 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.

==History==
Patented by [[Fouillaron]] in 1898. “To solve a thorny weaving problem, the engineer developed a variator system that prevented the thread from cutting when starting the looms”.{{cn|date=February 2025}}

In 1904, the  [[Fouillaron type G tonneau]] road vehicle was equipped with a wooden Tonneau body and a De Dion 6 HP single-cylinder engine; the car did not exceed 25 km/h. This vehicle has a very original gear transmission system with extendable pulleys.{{cn|date=February 2025}} This invention, which he further developed and adapted to machine tools, was later acquired by the Dutch car manufacturer [[DAF_NV|DAF]], and developed into the [[Variomatic]] transmission, since continued by a separate company called DVT.

The Variomatic was the first commercially successful CVT (as opposed to shifting between separate gears), first marketed on the [[DAF 600]]. In theory, this always produces the optimum [[torque]]. The Variomatic was introduced by DAF in 1958, also putting an automatic gearbox in the Netherlands for the first time.

==Efficiency==
Because 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).{{citation needed|date=May 2020}}{{clarify|reason=How good or bad?|date=August 2024}}

==Reversing==
Because 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. 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. Thus, these very cheap and simple cars were the 'formula one' in this competition.

==VDT==
[[Manual transmission]] remains dominant in Europe. 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. VDT continued the development of the CVT and introduced a push-belt system in the [[Ford Fiesta]] and [[Fiat Uno]].

==Operation==

===Gear ratio===
The final drive has two [[pulley]]s with moveable conical drums. The distance between the drums is controlled by the engine vacuum in the inlet [[Inlet manifold|manifold]] and engine [[revolutions per minute|RPM]], through centrifugal weights inside the drums. Between the two pulleys runs a drive belt. As a result of the change in the distance of the conical drums in both pulleys, the diameters and so also the [[Gear train|reduction ratio]] changes continuously.<ref>[https://books.google.com/books?id=wyoDAAAAMBAJ&dq=popular+science+1930&pg=PA140 "Belt Drive Shifts Dutch Economy Car."] ''Popular Mechanics'', December 1959, pp. 140-142.</ref>

===Differential===
{{Listen
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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 (mechanics)|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 the successes of the DAFs in [[rallying]]. There were several disadvantages that accompanied the lack of a true differential gear. 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. This led to rapid [[tire wear]] and placed stress on other transmission components. Snapped drive shafts were common. Low-speed handling in icy conditions was interesting as the system tended to drive the car forward against the influence of the steered wheels. Later cars, the 46, 66, and Volvo variants were fitted with a differentially geared axle. A version with a differential was developed by [[WilliamsF1|Williams]] in the 1993 [[Williams FW15C]] CVT [[Formula One]] car,<ref name="forix">{{cite web|url=http://8w.forix.com/altpower/williamscvt.jpg|title=Image: williamscvt.jpg, (600 × 386 px)|publisher=8w.forix.com|access-date=2015-09-02}}</ref><ref>{{cite web
  |url=http://www.ritzsite.demon.nl/DAF/DAF_cars_p17.htm
  |title=DAF passenger cars 
   |publisher=Ritzsite.demon.nl |access-date=2009-10-03
}}</ref><ref>{{cite web |author=Per Hansen |url=https://www.youtube.com/watch?v=6A9V2O5D8mc |title=Formula One with Automatic transmission |publisher=YouTube |date=2007-04-24 |access-date=2009-10-03}}</ref> but it was banned before being raced. In testing there were problems with the heat production.<ref>{{cite web
  |author=Keith Collantine
  |url=http://www.f1fanatic.co.uk/2007/05/03/banned-continuously-variable-transmission-cvt/
  |title=Banned! Continuously Variable Transmission (CVT) &#124; F1 Fanatic - The Formula 1 Blog 
  |publisher=F1 Fanatic
  |date=2007-05-03
  |access-date=2009-10-03
}}</ref>

==Motorscooters==
The Variomatic is also used in today's [[motorscooter]]s. It has been a standard part of all common scooters since 1985, and several companies such as [[Malossi]], [[Polini]], Doppler, and Stage6 are offering tuning clutches and variomatic for most common 50, 70 and 125 cc scooters.

==Steel link belts==
The modern CVT works according to the same principle of split pulleys allowing infinitely variable gear ratios. Rather than the pulled rubber drive belts as originally used by DAF, the modern transmission is made more durable by the use of steel link belts that are pushed by their pulleys. This improvement was pioneered by Fiat, Ford, and Van Doorne in the Netherlands from the late 1970s.<ref name="popsci">[http://www.popsci.com/archive-viewer?id=DgEAAAAAMBAJ&pg=57&query=gearless%20transmission "Gearless transmission - steel pulleys make it automatic"] ''Popular Science'', July 1976, pp. 57.{{Dead url|date=November 2024}}</ref> The gearbox is also under electronic control.

One version that incorporates the switch from rubber to steel belts was called the Transmatic.<ref name=popsci/>

==Availability==
DAF's Van Doorne's Transmissie is still operating (as of November 2015) in [[Tilburg]], Netherlands. It changed affiliations from the DAF group to Bosch in 1995.<ref>{{cite web
|url=http://www.plm.automation.siemens.com/en_us/about_us/success/case_study.cfm?Component=74570&ComponentTemplate=1481
  |title=Case Study: Keeping pace with the popularity of continuously variable transmission 
  |publisher=Siemens.com
  |date=2012
  |access-date=2015-11-03
}}</ref>

The CVT is available from brands such as [[Audi]], [[Honda]], [[Mini (marque)|BMW Mini]], and [[Subaru]].<ref>{{Cite web |date=2020-05-10 |title=Van Doorne Transmission Archives |url=https://oldmotors.net/tag/van-doorne-transmission/ |access-date=2023-12-09 |website=Old Motors |language=en-US}}</ref> [[Tata Motors]] from [[India]] intended to use a Variomatic transmission in its $2500 [[Tata Nano|Nano]].<ref>{{cite web
  |url=http://www.autoexpo.in/news_s1_2311.asp
  |title=Tata Motors seeks patent protection for Rs 1-lakh car 
  |publisher=Autoexpo.in
  |date=2007-11-23
  |access-date=2009-10-03
}}</ref><!--relevance - actual use?-->{{citation needed|date=August 2017}} The [[Nissan Primera]] is offered with this transmission.

==References==
{{Reflist}}

==External links==
* [https://www.uniquecarsandparts.com.au/how_it_works_variomatic_transmission How it Works: The Variomatic Transmission] <!-- https://web.archive.org/web/20170810103955/https://www.uniquecarsandparts.com.au/how_it_works_variomatic_transmission -->

[[Category:DAF]]
[[Category:Continuously variable transmissions]]
[[Category:Automotive transmission technologies]]
[[Category:Automatic transmission tradenames]]
[[Category:Dutch inventions]]