The great majority of CVTs use belts where friction is used to transfer torque. The main issues with this are the:
- *inherent* inefficiency
- relatively low limit of torque, and the possibility of slipping under heavy load
- inherent wear-out mechanism ( of which many Nissan owners should be very familiar with)
However, a Romanian mechanical engineer ( Edyson Pavilcu ) figured out a rather ingenious way to implement a CVT with *gears*!!! It is not yet in any production vehicle, be it two or four wheeled, it’s probably not going to be as sturdy as a comparably sized manual transmission, plus ICE engines are on a decline, but I think it will still make it, at least for bicycles. (there’s already a CVT for bicycles, but that’s *ball* based, not geared as per: https://www.cyclingabout.com/enviolo-cvt-hub-explained-internal-gear-bicycle-hub/ )
In any case, here are some info on the geared CVT or IVT ( Infinitely Variable Transmission! )
https://wonderfulengineering.com/the-worlds-first-geared-cvt-is-here/
https://unitbv.academia.edu/MrECVT
https://ratiozero.com/
This Is The World’s First Geared CVT and It Will Blow Your Mind - Ratio Zero Transmission