25 Responses

1. >> You would get better performance in the wind with a sail.

   That seems unlikely since you cannot go directly downwind faster than the wind with a sail.

   The fact that you don’t understand what wind is explains why you don’t care for the treadmill test.

2. Correction: It’s an extremely inefficient treadmill powered cart. You would get better performance in the wind with a sail.

3. If you set it on the ground in zero wind – it sits still. It’s a wind powered cart.

   >> Obviously the treadmill test is flawed.

   I assure you it’s not.

4. So what happens if you just put this vehicle on the ground in zero wind? That would be another scenario where all of the forces are the same and there is 0 apparent wind on the vehicle. Does it accelerate? My guess is no. Even if you gave it a little tap to start moving it would stop very quickly. Obviously the treadmill test is flawed.

5. It would be opposing wind pushing against wind, which would allow it to go faster than the pushing wind. In other words there is excessive trust in relation to, ratio to, the devices total weight/drag and it accelerates because of that excess.

6. If this is based on honest people sharing what they built, the answer is mechanical advantage. If, a gear attached to the rotor is made in a ratio to rotate 3 times to the 1 time rotation of the driving gear attached to the wheels that is only mechanical advantage. Explaining why it would start on a tail wind, if the device was light enough, even against the tail wind, once the propeller began to produce thrust, it would be opposing wind pushing against wind.

7. That is brilliant, thank you

8. You could use the principle on a bicycle, but it would be impractical for a lot of reasons (not the least of which is the safety issue). Also, the torque of the prop would be trying to push you over all the time. And without pivoting the whole prop mount, it would only work directly upwind or downwind.

9. Would this principle be useful for a wind-aided bicycle? Or would the propeller required be too big/heavy to be practical.

10. The top speed (either upwind or down) should only be limited by the efficiency of the power transmission between the propeller and the wheels.

11. The top speed (either upwind or down) should only be limited by the efficiency of the power transmission between the propeller and the wheels.

12. As I said, you can build your own cart and prove this wrong if you wish. The physics seems fine to me; the evidence seems clear enough; it’s been validated by an independent 3rd party; you have the ability to debunk the theory. Seems like pretty sound science to me.

13. Am i getting it right that you say that you can clearly see how fast the wind goes and compare it to the speed of the cart? I mean, I can’t. Neither can anybody by the way unless he has an anemometers built inside a head or something. You know it sounds like “Look there are invisible fish in the aquarium” and believe that…

14. Depends on what you’re trying to prove. I don’t need to know exact numbers to see if the cart’s moving 3x faster than windspeed, just like I don’t need instruments to tell a car is moving faster than a bike when it’s moving 3x faster. I only need those numbers if I’m trying to make a physics formula or something. I think it’s pretty clear that these guys (as well as others) have demonstrated DWFTTW, and you don’t need to know exactly how fast the wind or the cart was to see that.

15. As an engineer I feel totally myself to build a cart that would runs using windpower.

    As a realist I know that I’ll never find a 1 km of a straight isolated road, a wind source that blows constantly along the path on that road, of course I will not find 10 anemometers in my closet to put along the road. I won’t be able to test the speed of the cart so that it doesn’t hurt the results.

    There are lots of thing that defines the real experiment from the amateur propellers on the wheels.

16. They show you how to make your own cart. Feel free to do it yourself and prove them wrong….

17. I guess this shouldn’t be too surprising, given that no one has a theory called the conservation of speed. Now, if someone managed to show that the DDWFTTW don’t obey the conservation of energy, now that would be something!

    Good video though, thanks!

18. I would LOVE to see this on Mythbusters.

19. true, annoying.

20. I agree. That was not intentional. It was more a result of the free program we used – and our lack of video editing skills.  Sorry.

21. Poor choice on audio mixing. It’s very annoying to those of us who hear with only one ear.

22. This video has confused you.
    There is energy being added to the system in the video by the motor running the treadmill.
    When the same cart is outside on the road the energy is being added by the wind on the blades.
    The 2 scenarios are mathematically interchangeable.

23. The air in the room is still – relative to the room. Rather than move air over the surface (wind), we move the surface beneath the air (same relative motion – still “wind”).

24. Look for my build videos under “spork33”. They will walk you through a build with part numbers and everything.

25. We established a world record with “Blackbird” by going directly downwind at 2.8X wind speed. This winter we’ll be replacing the propeller with a turbine (which will look just about the same) so we can go directly upwind faster than the wind.