I’m amazed that Mark has persisted in his argument for so long. Honestly, it’s astounding. He still can’t seem to admit that the video I wrote about yesterday demonstrates that downwind, faster-than-wind, wind-driven travel is possible. Let’s take another tack and systematically address the objections (Update: I’m updating this post as more objections come up) (Update2: In case you’re coming to this page directly from this site: Mark has now seen the light and admits that downwind-faster-than-wind is possible).
Once again, for reference, here’s the video demonstrating that the cart works:
Now let’s consider the objections:
1. The treadmill isn’t an authentic test. Mark and others say that the treadmill is adding energy to the equation, thus, this isn’t a perpetual motion machine.
They are right! It’s not a perpetual motion machine. Wind or some energy source is required! The treadmill is simply simulating the wind. The problem does not call for perpetual motion, just wind-aided travel that proceeds faster than the wind.
The treadmill gives us an easy way to see if the cart is moving faster or slower relative to the wind. Imagine an aircraft carrier moving 10MPH across a windless, flat sea. You’re on the deck. Your experience is a 10MPH wind. There is no difference between this and a treadmill — the treadmill just allows us to extend the length of the aircraft carrier indefinitely, and easily monitor the progress of our cart. Since the cart moves in the opposite direction from the treadmill, it goes faster than our simulated “wind.”
2. Since the wind is moving slower than the cart, there’s no way for the wind to push the cart forward
This conveniently ignores the mechanism of the cart and simply declares that the device is impossible. I’ve now explained how the device works several times, and no one has explained how my explanation doesn’t make sense, other than to make declarations like this. I think this is the simplest explanation:
Assume the prop is a simple one made of flaps angled at 45 degrees. As long as the rotational velocity is greater than the relative wind speed, the wind will be “pushing” against the prop.
So assume a 10 MPH wind. The force of the wind can move the cart 10 MPH without the assistance of the prop. Now assume at this speed the wheels can drive the prop at an average rotational velocity of 5 MPH. There is an effective additional wind force on the prop of 2.5 MPH. This makes the cart go 2.5 MPH faster. We’re now going 12.5 MPH, in a 10 MPH wind!
Obviously it will take things a while to equilibrate, and the final velocity computation is complicated, but the net result is a car moving downwind faster than the wind.
I gave a slightly more complicated version of this in a comment on Mark’s blog, but an illustration might make things clearer:
The wind isn’t pushing against the cart that’s moving faster than the wind. It’s pushing against the prop, which has a relative motion that means there’s still something to push against.
3. But the wind isn’t moving relative to the cart
See 2 above. The wind doesn’t have to move relative to the cart, just relative to the propeller.
4. The treadmill isn’t moving right-to-left. It’s a trick
No, the treadmill is moving right to left. Look at video, around 4:30. You can clearly see the stripes moving right to left. Any apparent motion of the wheels in the “wrong” direction is the wagon wheel effect. Watch the wheels closely as they start up and slow down to be sure.
5. The cart can’t get going on its own. It only works because it’s put on a running treadmill
This is debunked in the original video, where they take the cart outside and it starts on its own. Look at the video again, starting at 6:20.
6. BUT IT’S IMPOSSIBLE TO SAIL DOWNWIND FASTER THAN THE WIND!
No it’s not. Consider this example, which is explained by the cart’s creator here. I’ll summarize for you:
Sailboats can and do travel faster than the wind if they tack (zig-zag back and forth). Their downwind vector is faster than the wind. A fast sailboat can beat a hot-air-balloon in a steady wind. This is established fact — ice boats travel downwind in this way more than twice as fast as the wind. Attach two boats together with a telescoping rod and sit in the middle and you’re moving due downwind, faster than the wind.
7. You can’t draw energy from wind if the wind isn’t moving relative to you.
Yes, you can. See 2, 3, and 6 above. The trick is to have something else move relative to the wind for you and then harness that power — either the propeller or the two boats or some other ingenious device.
8. If this device worked as advertised, then it would also work in no wind at all, which is obviously impossible.
No, it wouldn’t. As explained in 2, 3, 6, and 7 above, it requires the wind to operate. The force to move the vehicle comes from the wind (or the motion of the treadmill, which simulates the wind). When they set the cart down in a still room, it doesn’t move. When they lift it off the treadmill, it slows to a stop.
The reason it goes faster than the wind is because the propeller captures more of the wind energy than is necessary to move the cart at a speed equal to the wind. The larger the prop, the more wind energy is captured (just as larger sails allow a boat to go faster). The trick is to move the propeller so that this extra energy can actually be used, as explained in 2 above.
9. Ice boats can’t really go faster than the wind.
Yes, they can. Here’s a document (PDF) that gives quite a bit of data demonstrating that fact. Ice boats routinely travel 70 MPH in 15-MPH winds. They can go more than twice as fast as the wind when tacking downwind. They can most definitely beat a hot air balloon to its destination due downwind.
10. If the wind isn’t driving the prop, then the prop isn’t driving the wheels.
That’s right. The wind is driving the wheels, and the wheels are driving the prop. Remember, there’s lots more energy in the wind than what is used to drive the car forward (assuming it had just an ordinary square sail). If you had an ordinary sail and were going due downwind, you wouldn’t be able to go faster than the wind. You could double, triple the size of the sail and it wouldn’t make a difference. But you’d have to use more braking power to slow the car with a larger sail. Now, imagine if you harvested that energy somehow. You could put on the brakes for five minutes and use that to generate energy (much like a Toyota Prius works). Then you could trim the sail to a smaller size and apply that energy by running a motor to drive the wheels. At this point, you’d be going faster the wind (but the sail would appear to be filling “backwards” from the relative headwind). This vehicle effectively does the same thing, but constantly and in a simpler fashion.
11. There is no way to make the transition from slower-than-wind to faster-than wind.
Yes, there is. The vehicle works the same way when it’s going slowly as it does when going fast. Look at the video at 6:20. It starts from a stop in the wind. The propeller rotates. The car accelerates. There is no transition. You could design a vehicle like this that would go at exactly wind speed. Just add enough friction to the works, and the car wouldn’t be able to go faster than the wind. This might only work at a single specified velocity. But you could design a vehicle with a wind detector on the front. It would automatically put on the brakes whenever the relative wind speed was zero.
In fact, the vehicle’s designers do exactly that when they run it on the treadmill and slow it with the spork to keep it from running off the end of the treadmill. The vehicle is going slower than “wind” when it goes backwards down the treadmill, and faster when it moves forwards up the treadmill. Each time it does this, it makes the “transition” from slower-than -wind to faster-than-wind.
12. If this is true, then why isn’t someone making a fortune off of this fantastic invention?
Because people don’t always want to go the same direction the wind is blowing. Also the wind is unreliable, and doesn’t always blow when we need it. That’s why powerboats and cars were invented. But maybe someone should consider attaching a generator to a windmill and selling that power to the electric company… I wonder if that’ll ever catch on.