hrmf. now I'm baffled. I don't get it or understand how these guys are demonstrating this. I (think) I understand something moving faster than the wind dead downwind in that the prop would be powered from the wheels and once moving in the opposite direction from the wind, will push wind against the wind providing the propulsion needed...but in a static air situation, I just can't figure out how the cart is constantly pushing forward faster than the treadmill is powering it.