Faster Than The Wind

Dennis sent me this link about a week ago. It's kind of intriguing.



These guys are trying to outrun the wind, that is, they are going in the same direction as the wind, only faster. There is a wind vane and a anemometer mounted on top of the chase car. Notice that the vane is pointing toward the back when they start out, but that after they get up to speed it is pointing the opposite way: towards the front indicating that they are going into the wind. The wind hasn't changed direction, only their velocity has.

The cart has no engine, it is powered solely by the wind. The wheels are connected to the propeller through gears.

I read some of the stories, but nowhere did I find a clear explanation of how it works. I've been stewing about it, and I've come up with an explanation of sorts. It may not be the best, but it's all I've got so far, so I thought I would throw it out there and see if it floats.

First of all, you need to realize that the propeller is not working as a turbine. If it were then the wind would turn the propeller and the propeller would turn the wheels. That would work only as long as the wind was blowing faster than the cart, and that is not what they are trying to do. If you look at the way the propeller blades are pitched and the way the prop is turning when it first starts out you will see that the propeller is turning the wrong way for it to act like a turbine.

So the propeller is turning into the air as the cart moves forward. Pushing the cart forward in still air would take very little effort. The cart is light, the wheels have low rolling resistance, kind of like high pressure bicycle tires, and the propeller is basically freewheeling through the air. It is screwing through the air in the same direction and at roughly the same rate as the cart is moving over the ground. A guy could probably push it along at 5 or 10 MPH without too much difficulty. How long he could keep it up would depend on how fit he was, but that's really beside the point.

If the propeller was not turning, i.e. it was locked in place, it would take considerably more effort to push the cart along because you would be trying to push this propeller through the air.

With the wind blowing, it is going to be pushing on those propeller blades as if they weren't turning, but because the blades are turning as though they were in still air, but now we have wind pushing them, so now we are moving 5 or 10 MPH faster than the wind.

With no wind, there is virtually no force on the propeller blades, no matter what speed you are going. With the wind blowing, we've got the force of wind pushing on those propeller blades, and that is what is going to make it go. The only thing holding this thing back is friction, friction from the wheels, the bearings, and even the air. It is going faster than the air.