Algodoo

Good CVT, but the gearing breaks after some time. You can't fixate something to an object that changes its size, the position of the fixate will drift with time. To fix that there's a very simple method, just hinge the input CVT gear (the one that is fixated to the dark circle) and the output fixed size gear (the one that is fixated to the CVT output) to the chassis, and use a stretched axle (hingeConstant 1e-30, brake +inf) to connect the two circles that you want "fixated". You have to use low hingeConstant or it'll start flapping around at less than 100 rad/s

It's just tech demo of using kinetic energy instead of electric or fuel. Simple to use, it has high efficency and potentially can give unlimited powe... limited by gearbox strength power