Not too long ago Topher started a thread asking: is it possible to construct a wind powered vehicle that goes directly downwind - faster than the wind - steady state? I claimed this could be done, and I posted vector diagrams showing exactly how. This earned me a number of responses similar to this one from Shroder: I see. So the treadmill is exerting a force on the cart which is trying to accelerate it backwards. The restraint prevents this, so the turning wheels transmit force to the prop which then tries to accelerate the cart forward. And, the force of the prop on the cart is greater than the force of the treadmill on the wheels, so it moves forward. So what you are describing is a force multiplier. A simple lever is a force multiplier but the output force cannot be used to drive the input! What you are really describing here is a perpetual motion machine and it is an elaborate hoax. I am surprised that this thread has been allowed to continue for as long as it has. And this one from Topher: Also, I have constructed a vector diagram and analyzed it as I have asked spork to do several times. Its pretty clear just by looking at the diagram itself that the thing will never have a downwind component faster than the wind. Note that I did post a vector analysis, and it appears earlier in that thread. Aparently the administrators agreed that such a vehicle could never be built - because that would in fact constitute perpetual motion. As such, they locked the thread. So.... a friend and I went out, spent hundreds of dollars, and quite a few hours, and built a vehicle that does exactly that. And here that vehicle is: https://www.youtube.com/watch?v=4pgDs50A-Yw I assume this thread will be closed shortly as well. But at least for now, here is the physical proof that the vehicle originally asked about can be built to operate as described.