Some cone CVT models use two rollers.[23][24] In 1903, William Evans and Paul Knauf used for just a patent over a constantly variable transmission using two parallel conical rollers pointing in opposite directions and linked by belts that would be slid along the cones to change the transmission ratio.   https://gearboxcvt15689.blogsuperapp.com/33223453/the-smart-trick-of-gearbox-cvt-that-no-one-is-discussing