Discussion Real or Fake? The Physics of Wind Vehicles

Did you watch the video? If yes, then good. Do you agree or disagree with the information provided? Based on the demonstration of the wind vehicle, I'm inclined to believe that vehicles can go downwind faster than the wind pushing the vehicle. As long as the vehicle can use the energy provided from the wind to spin the wheels, the wheels will convert it's energy to spin the fan on top to push the car forward by pushing off of air particles. At least, that's how I interpret the physics in the video.

Also, the comments on the video contain anything between civil discussion, flat earth, cylindrical earth, or people calling this a hoax. Please stay on topic, and be civil.

Edit: Follow up of the first video, feat. Bill Nye, Neil deGrasse Tyson, and Mark Drela.



Skip to 14:25 on second video for the explanation of how the Blackbird car works.

 

The wind speed is relative. The faster the vehicle moves, the faster the perceived wind is, and as a result the vehicle will move even faster and so on. Now this might lead to a wrong conclusion that it is a positive feedback loop causing the vehicle to be infinitely fast over time. But at some point the air drag will cause resistance towards forward movement. The windmill also has a limit on how fast it can spin. So basically, the vehicle has a speed limit.
The same goes for moving upwind, since the fan will stop rotating once the vehicle is moving at the same speed as the wind, the perceived wind speed becomes effectively zero.

 

It's fake. There's something called energy transformation ratios in which some portion would lost during the process. Which is why there's nothing called perpetual motion.

 

I agree on there being a speed limit. The fan is not spinning because of the wind. It's spinning because of the wheels. The fan keeps spinning until the wheels stop spinning. Also, I imagine that this vehicle would do poorly going upwind, since the vehicle would lose speed as the fan adds energy to the wind. Sorry in advance if I misinterpreted your comment.

No one in the video claimed the vehicle was a perpetual motion machine. They claimed that a vehicle can go faster than the wind because it utilizes the wind to jumpstart the wheels turning, which in turn cause the fan to spin, taking energy from the wind and converting it to speed. The limit of the vehicle's speed depends on drag, friction, and potential energy in the wind. The same vehicle can be put on a treadmill to become faster than the treadmill. There's no wind on the treadmill, but the vehicle is still going faster than the treadmill.

 

The fan is definitely spinning because of the wind. The fan's rotation is then being transferred to the wheels. As the vehicle moves forward, the wind speed measured while sitting in the vehicle will be greater than the wind speed measured by someone standing outside. So, it might appear like the vehicle is moving faster than the wind.

 

Just to be sure, did you watch the video? The video shows the car with a telltale and a windsock. The telltale is in the opposite direction of the windsock at 16:39 in the video.

I know how propellers work, since I've built a working model in high school. Lift is generated when air passes around the wings of a plane, and the propeller acts as acceleration.

The fan on the vehicle spins because of the wheels attached. The vehicle also works on a treadmill with no wind. A smaller scale vehicle will actually go faster then the treadmill spins.

 

I think you completely misunderstood the video. I don't think the wheels are connected to the fan.

 

Can you point to the part of the video, so I can see that myself? Are you talking about 8:40?

 

It's literally the whole point of the video. To be pushed by wind alone and go faster than that wind speed.

 

Yes, the video was trying to prove that the car can go faster than the wind, but I don't see where you say that the wheels aren't connected to the fan.

11:30 is where Veritasium talks about the wheels turning the fan.
"Now that causes the wheel to turn, and they are geared to the propeller..."

 

Because it's what they were trying to prove. If you say they were connected that means you're one of the people who believe the video was false and they cheated. I won't argue against that because I don't know if they cheated. But if you say you believe this video to be true then you also believe the wheels are not connected.

 

So, you're saying that for this car to be faster than the wind, the wheels must not be connected to the fan? Why is that a problem? I'm genuinely curious, because the car can only go faster than the wind if there's some way for the fan to propel the car forward.

Keep in mind, the vehicle also works on treadmills, which has no wind.

 

Catamarans have been known to reach speeds close to 3 times the available wind speed on water. It makes sense that similar principles can be used on land.

 

Does the principles actually work on land, though? That's what I'm trying to understand. I would like it to be true, which is why I'm asking for other people's thoughts.

 

No, that's not what I'm saying at all. I'm saying it's the literal point of their video, to prove that wind alone can push the cart forward faster than the wind itself. So if the wheel was connected that means they cheated. Right?

I don't know. What do you think was the point of the video then?

 

Just think about it.
- The windmill would pose a surface resistant to wind in addition to the vehicle body. Since they do not powered to propel forward faster than the wind forces itself what you have here essentially a sail.
- Kinetic energy that are generated by windmill that would be lost during it's transfer to the wheel via connecting power shaft or chains.
- Weight of the whole vehicle and surface friction connected to it.

 

I re-watched the video. The wind helps move the wheels, which spin the fan. The wind alone is what gives the car the energy to move forward. Nothing else is being used, unless you mean that Wind -> Wheel -> Fan -> Acceleration is cheating since there's steps between wind and acceleration. This vehicle uses similar principles to boats and ships that don't have engines or motors.

I agree that the point of the video is proving that wind can make a vehicle move faster than the wind around it.

I agree that the car is built with what is essentially two sails, but the design is made such that the wheels provide the energy for the sails to spin around the "cylindrical" Earth.
Energy is lost due to drag and friction, but there exists enough energy leftover to accelerate the car faster than the wind around it. The weight of the vehicle is light enough that wind can push it forward. (11:20 in the video.)

 

If you agree with my first comment you wouldn't say that the leftover energy could've move the vehicle faster than the winds it is converted from.

 

There is no perpetual motion, yes. The energy is taken directly from the wind behind the fan. Energy is not coming from nowhere. The wind behind the car is now slower than the wind around it.

Your points are correct, but we differ in how the physics work out. You say that the car is not a perpetual motion machine, so the video is false. I say that the car is not a perpetual motion machine, so the video is true.

These are the facts in the video:
The two fins act as a sail to propel the car forward.
Kinetic energy is lost when transferred from the wind to the car.

I do believe that the energy lost is insufficient to slow the car down, and in fact speeds the car up to a point. It's possible this video is fake, but I consider Veritasium to be a trustable source of information, since he spends much of his time verifying whatever he does before he posts a video. That is why I'm asking for people's thoughts to disprove Veritasium. It's always possible to be wrong, even if a person verifies something themselves.

 

I haven't watch the video before my two comments but after actually watching i can totally now says it's fake yes.

- In the video the vehicle went against the wind direction.
- the windmill rotation rates per minute visually slower than the wheels rpm. Even if they use differential gear conversion it'll make greater kinetic lost during transfer. Windmill rpm and wheel rpm did not match.
- wheels design would dig into the surface adding additional friction to them.

I've presented to you 3 points why it wasn't possible and you can now add this as well.