Rollers

The elegance of the CVT is in this ability to maintain the rpm independent of vehicle speed… When the rpms go above the shift-speed then the increased centrifugal force pushes the variator rollers out farther, squeezing the front sheaves together more, thus slightly lowering the ratio of CVT (higher gear), and therefore dragging the engine speed back down.

Think of what happens when you shift a manual trans quad from 1st to 2nd – the rpms drop. The converse also applies, when the load increases (like going up a hill) and the rpms drop, the clutching automatically compensates by easing the front sheaves back apart, increasing the ratio (lower gear), until the shift-speed is achieved again. In practice, this happens so quickly, and on such a minute scale, that these adjustments are completely unnoticeable.

Moral of the story is this: the variator roller weight is the primary means to adjust shift-speed. A higher weight will have the effect of squeezing harder at a given rpm, therefore decreasing the ratio (increasing the “gear”) and decreasing rpm. Likewise, a lower weight will increase the ratio as well as shift-speed.



By: George Szappanos

Source: ATV at Off-Road.com

Hi-rev engines use lighter rollers.

Hi-torque engines use heavier rollers.