No fair doing web searches for info on this one.
You have a vehicle that has a propeller facing directly upwind driven by the rear tires of a vehicle that is moving directly downwind. The propeller is driven by chain drive via a sprocket on the axle connecting the rear tires and a sprocket that is connected to the axis of the propeller. The setup is that as the tires roll forward and downwind, the propeller is driven to generate thrust upwind.
Assuming the overall efficiency (chain drive, rolling resistance, aerodynamic drag, ...) is high enough, could such a vehicle continously move downwind faster than the wind?