Direct Downwind Faster Than The Wind #5 (DDWFTTW)

Any luck having Mythbusters verify your cart yet? Looking foreword to it.

I don't know what VMG is but 49er's SK4's Foiling moths and several other high performace sail boats can exceed wind speed down wind. this does not conflict with any laws of physics because they are moved by differnces in air pressure not wind speed.

There are ways to achieve down wind faster than the wind. Some sail boats achieve it because of their hull design in conjunction with the aerodynamics of the sails. Downwind the combination of air pressure pushing from behind and appearent wind over the airfoil created by the sails can combine to more than compensate for drag and thus the boat is somewhat faster than the wind speed( don't confuse with pressure )

The tread mill is your "power source" spinning the drive wheels fast enough to spin the fan at a high enough rate to move the vehicle foward and up a slight incline. If it was engineered a little better it would go faster but your propeller is very inefficient, it looks like the one that comes with a rubberband powered airplane. there is no great scientific break through here and you have not explained how the vehicle can travel down wind faster than the wind.

Because the propeller is pushing against still air not a 10mph wind, it only needs to provide enough thrust to support its weight and the wheel resistance. A large light slow moving propeller is the most efficient way of doing this.

It is actually better to lower the gear ratio slightly, then compensate by upping the speed of the treadmill. This will reduce the frictional force generated by the wheels as they spin the propeller.
Try upping the gear ratio too much and there will be so much friction that the vehicle will be unable to advance fast enough to move the fan.
It will be shoved violently off the treadmill.

noob
If the world is ran by your poor logic, then airplanes won't even take off anymore (because O NO!! THERE IS AIR FRICTION).
However, our world is not ran by you, so airplanes uses the same fuel to take off towards east or west. (I am saying this because the earth spins. lol duh)