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- This article refers to the variator-style transmission. For the Moped Army branch, see The Variators.
A variator is an element of the Continuously Variable Transmission commonly used on mopeds and other small engine vehicles. Motobecane, Peugeot, Derbi, Vespa, Minarelli, and Honda mopeds all offered at least one model with a variomatic transmission.
Variomatic transmissions use centrifigual weights to decrease the engine's gear ratio as engine speed increases. This allows the variator to keep the engine within its optimal efficiency while gaining ground speed, or trading speed for hill climbing. Efficiency in this case can be fuel efficiency, decreasing fuel consumption and emissions output, or power efficiency, allowing the engine to produce its maximum power over a wide range of speeds.
Since the variator keeps the engine turning at constant RPMs over a wide range of vehicle speeds, turning the throttle grip will make the moped move faster but doesn't change the sound coming from the engine as much as a conventional two speed or one speed. This confuses some riders and leads to a mistaken impression of a lack of power.
Motobecane made their first and only variator-based transmission, the Mobymatic, in 1957, the year after the CVT was invented by Dutchman Huub Van Doorne, even before the first CVT car.
The Mobymatic consists of a variable dimension pulley driven by two to four weighted ball bearings, tied to a two function automatic clutch. The variator pulley turns a fixed-diameter pulley attached to a final drive chain.
The Mobymatic transmission came standard on Motobecane models up until their last production run in the early 2000s. The only difference between the early models and later editions was the abandonment of the woodruff key.
While not the best design in terms of tunability or clutch performance, it was an inexpensive workhorse that requires no maintenance over the life of the engine other than regularly supplied grease through its grease fitting every few hundred miles.
Vespa's variator came on all their deluxe model mopeds, the Bravo, Grande, Vespa Si, and even the high end version of their economy model, the Vespa Ciao Deluxe. This drive differs from the Mobymatic by separating the clutch and variator mechanisms, using dual variable pulleys and eschewing the final chain drive all together. The variator is driven off the engine crank with a roller weight actuated variable pulley. A belt stretches between the engine and the rear wheel, where the clutch and spring pulley are located. The spring pulley keeps the belt under tension with requiring the two pulleys to move in relation to one another, as the French pulleys do. The Vespa also houses a gearbox inside the rear wheel hub, where the variator output is geared down by the final drive ratio and then applied to the wheel.
The Vespa variator utilizes five roller weights. The lack of symmetry with this design means that the variator's performance cannot be changed by removing weights. however, some models came with six or eight weight variators.
Honda essentially copied the design for their variator, and arguably their entire PA50 moped, from the Vespa Bravo. They employ the same functionality with some technical differences.
There are 6 weight variators and 3 weight variators for Derbi (the 6 weight are compatible with the Honda Hobbit). There are also performance variators such as the TJT variator. To understand the functions of dual variators better and contra springs please read the following link http://www.apriliaforum.com/forums/showthread.php?t=8960
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Peugeot's variator system, used on most Peugeot moped models (most notably, not the 102SP) is much like that used by Motobecane, though the systems are not interchangeable. A centrifugal weight-driven variator with an integrated clutch is linked to a large fixed-diameter pulley attached to a final drive chain. Belt tension is kept constant by the entire engine rotating downward on its mounts as speed increases, with a spring returning it to its original position as it decreases.
basic variator function please read this or someone attach it to our wiki http://www.apriliaforum.com/forums/showthread.php?t=8960
See Variator Tuning