Re: A new shift concept for the engineers....
it could also be done manually. if you had a stacked sprocket set-up and a functional, spring loaded chain tensioner, you could easily stop, pull the chain off one sprocket and switch it over, letting the tensioner spring forward and back.
it'd be good for going from street to trail or flatlands to canyons, or wherever a lower (or higher) gear was needed.
i was thinking of my old Honda CT-90, '67 i think, that had a sprocket on both sides of the rear rim. for trails you had to switch the wheel around.