To bad they don't explain the physics behind this. Otherwise, pretty amazing stuff!

It's an efficient wind machine, but not a perpetual motion device as it is powered by the wind. Speed is not an indicator of power output in this case as the machine did not produce MORE wind than was put into it. Yeah, something like that.

The force to move forward is greater than the weight of the vehicle.

If there was a human sitting on it, it'll be a lot heavier, thus require much more energy for that initial launch I would think. Not to mention the size of the propeller and headaches you'd get when aerodynamics change when human sits on it.

Put some pedals and chains on that thing, and I would think it's gonna be a great energy saving bike, though I bet it's gonna be a little chilly on the driving seat. As long as you got the pedals, it wouldn't have to rely on wind for initial takeoff.

"In the end the physical world does not succumg to scientific theories..."

Huh?

I posted something like this 2 weeks ago. 2 votes. Arrggh


http://www.videosift.com/video/Downwind-faster-than-the-wind-fascinating

betchu it has to do with pressure differential right in front of the propeller and right behind it. This wouldn't work with a common sail design...

mycroft where are you?!!!!

Since it's on a tread mill it's actually remaining stationary with wheels turning below it so it's actually going 0 mph

lol, after watching aspartams video you can see that the wheels rotating on the treadmill make the propeller spin which causes vehicle to move forward. Where's the wind?

>> ^Fusionaut:
lol, after watching aspartams video you can see that the wheels rotating on the treadmill make the propeller spin which causes vehicle to move forward. Where's the wind?


good point...would this test work on, let's say, the ice with blades instead of wheels?

>> ^Fusionaut:
lol, after watching aspartams video you can see that the wheels rotating on the treadmill make the propeller spin which causes vehicle to move forward. Where's the wind?


They explained that. The wind is moving forward relative to the surface it is riding on. When he places the vehicle on the treadmill it is going the same speed as the wind but manages to propel itself forward faster than the air around it. If this was not the case it would never move forward on the treadmill.

would this test work on, let's say, the ice with blades instead of wheels?

I remember listening to a sailing race at work once where the commentators were talking about the boats moving faster than the wind. I looked around and found this: http://www.boatsafe.com/kids/bramp1099.htm . There is a lot of information out there about it, but I liked the illustration from this one.

^ Unfortunately that link is to do with apparent wind and travelling faster than it.

This video is about travelling DIRECTLY downwind faster than the wind (hence ddwfttw).

Ok now i've got it, if no one else does i'll explain it tomorrow.

Edit:
The guy made a few posts about this device on a major forum (PhysicsForum) and got both threads closed down among cries of "heresy! burn the wizard!" He insisted that it worked in the face of hundreds of pseudo(and non pseudo) scientists/engineers telling him he was a fool and having his threads locked/deleted. Then he converted one of his friends (who also said it wouldn't work) and they made the device. I can't find out definitively who made it but it wasn't those 2 guys (the guys who also made this video), but it seems to be the slightly elderly guy whose wife we see pushing the larger scale model. The guys who made this then made a few more threads saying "see?" and are still being treated with skepticism.

>> ^therealblankman:
"In the end the physical world does not succumg to scientific theories..."
Huh?


This simply means science was wrong. Could such a thing be possible?

>> ^Psychologic:
>> ^Fusionaut:
lol, after watching aspartams video you can see that the wheels rotating on the treadmill make the propeller spin which causes vehicle to move forward. Where's the wind?

They explained that. The wind is moving forward relative to the surface it is riding on. When he places the vehicle on the treadmill it is going the same speed as the wind but manages to propel itself forward faster than the air around it. If this was not the case it would never move forward on the treadmill.


So since there is no wind and it is moving forward it is going faster than the wind that isn't there?

The only way this would be cool at all is if the vehicle is being powered by wind but is going faster than wind that is powering it which is IMPOSSIBLE!

This vehicle is sitting on a treadmill, which is turning the wheels, which is turning a shaft, which is attached to a propeller, which is blowing wind away from the vehicle, which makes it go forward, relative to the "air" around, VERY slowly.

It is not going faster than the wind because THERE IS NO WIND.

The moving treadmill relative to still air is equivalent to moving air relative to a still road. As they said in the video, it's just easier to do the experiment with a treadmill so the frame of reference is stationary.

It also doesn't violate the second law of thermodynamics, so it's not perpetual motion. It just means that the device seems to be able to extract more energy from the wind than a sail would, and turn it into forward motion.

Pretty cool, if you ask me.

>> ^Aemaeth:
>> ^therealblankman:
"In the end the physical world does not succumg to scientific theories..."
Huh?

This simply means science was wrong. Could such a thing be possible?


I don't think there was anything wrong with the line as stated. If the statement were true, then its inverse would also be true: scientific theories succumb to the physical world. If science does not accurately model and explain events in the physical world, then that scientific theory is in fact wrong and a new theory is needed. It's not that 'science' is wrong, but just the particular theory.

I think this is still a "lift" situation; it's just that the propeller allows them to create a "directly downwind" pressure differential, which sails can only create when somewhat crosswind. So, essentially, the wind is not the sole source of energy here.

The whole treadmill thing is a cheat because it's doing the opposite of what they're claiming is possible. It's using the "ground" of the treadmill to overcome the air/ground friction, not using wind to go faster than the wind. Their one actual wind test just shows that the wind will blow it (well duh!) not that it goes faster than the wind.

Essentially what I think they've done is create a propeller/linkage that has less friction than the car's air resistence, this allows the treadmill to power the propeller with enough force to let the car climb the hill slowly.

It's a total cheat, these guys are hacks. Not worth Mythbuster's valuable time.

The treadmill is a good tool. Sure, relative to the handles there's no wind, but relative to the tread, there is wind. Think of standing on a moving sidwalk. If the sidewalk moves fast enough, even inside a building you'd feel wind blowing against you.

Also, this device doesn't break any laws of physics - it's not a perpetual motion device because when you take away its power source (the wind), it will slow down and stop on its own.

This is just an ingenious method from extracting more power from the wind than you could by friction alone. The sailboat link from above is another good example of this, one can sail almost directly into the wind and even against the current and still move forward relative to the shore.

I don't see the problem. You take a large 2d area of wind, wich contains an amount of energy and convert it to forward momentum on a small, light object. You're essentially just talking about the principle of gears here. Torque into velocity.

mythbusters already proved part of this myth.

The episode where they show that a plane can take off on a treadmill, they explain that when the ground is moving under the object, so long as the object has wheels, its going to be unaffected by the friction of the ground and therefore stay in the same place.

What they've done, is added a fan to the front axle of the wheels, which then gives thrust to the back of the cart, and since there's nothing stopping the object from moving forwards, it has nowhere to go BUT forward.

Using the treadmill proves my theory, but the problem with MY theory in proportion to the "Myth" is that the vehicle would have to generate thrust to move, and treadmill is doing that for it this video.
They give a very brief showing of the vehicle on the road, but it veers off, and we don't see it again, and we're unable to tell if it's self-sustaining, or if the thrust it needs to generate is too great, because the treadmill is actually supplying a power source.

I'm not skeptical about this, I actually think it's very cool, but I'd like to see more of the vehicle powering itself.

This thing gains no power from "wind".

It's all torque and power conversion from the electric motor powering the treadmill. It all can be looked at as a geared system.


EDIT: or like what the second guy above me said... :rolleyes:


ps. You guys are wrong, it DOESN'T travel "forward", it travels in the direction of the treadmill at a much slower speed in relation to someone standing beside the treadmill. REMEMBER YOUR VECTORS PEOPLE!!!

Treadmill moves at 10mph to left.
You move at 0mph.
Air from fan moves at 12mph to left.
Fan moves at -2mph to left.

It all cancels out. tread-fan-wind = 0 = 10mph-(-2mph)-12mph
No gain. In fact, the air is probably moving 12.2mph, because of loss to heat in the parts...

They need to measure the air moving from the props...

Ya ya ya, they fooled me into believing the outside machine actually did anything. It's a hoax. Look below for what I finally figured out about their indoor "proof".

>> ^Drachen_Jager:
The whole treadmill thing is a cheat because it's doing the opposite of what they're claiming is possible. It's using the "ground" of the treadmill to overcome the air/ground friction, not using wind to go faster than the wind. Their one actual wind test just shows that the wind will blow it (well duh!) not that it goes faster than the wind.
Essentially what I think they've done is create a propeller/linkage that has less friction than the car's air resistence, this allows the treadmill to power the propeller with enough force to let the car climb the hill slowly.
It's a total cheat, these guys are hacks. Not worth Mythbuster's valuable time.


Sorry, but that is utter bollocks.

Your mistake is that you haven't realised that they are simulating the cart at full speed. This example doesn't demonstrate the cart getting to wind speed, it simply demonstrates how the cart acts AT and then BEYOND windspeed.

The treadmill is exactly the same as a road with a 10mph wind as newton and einstein et al tells us. For the purposes of this experiment there is no difference between a stationary road with a 10mph wind and a treadmill travelling at 10mph.

Just think about it, if you've even half the scientific knowledge you seem to display you'll understand it if you think carefully enough:
- The treadmill simulates motion at 10mph. The air is stationary relative to the cart.
- The wind blows the cart to 10mph, the cart experiences no wind for or against due to travelling at the speed of the wind. Ergo the air is stationary relative to the cart.

In both of these frames of reference all you are seeing is the road (or treadmill) rotating the wheels to a speed of 10mph.

It's like debating whether the universe moves around outside the earth and the earth is stationary, or whether the eart moves around inside the universe and the universe is stationary. Which is real? It depends on your perspective.

Also, i'll explain how this works:

The prop on the back of the cart has a large flat surface area. The wind blows the cart up to the windspeed by blowing on this surface like a sail. The prop is shaped so that the wind would turn the prop in the other direction if it wasn't geared to the wheels.

So the cart is blown up to 10mph with the prop acting as a sail. Once it reaches this speed, the prop's shape and position is such that the prop now exerts a force in the opposite direction to motion.

Because of the 10mph wind, the cart experiences no air resistance and is only experiencing the resistance of the wheels on the ground (and some from the gears).

While this seems counter intuitive, as though it's perpetual motion, it isn't because the prop can only power the cart if the wind is creating the environment of decreased air resistance!

at 5:10 he makes a fatal mistake that proves this is a hoax.

EVERYBODY knows there is no spoon.

>> ^dannym3141:
The prop on the back of the cart has a large flat surface area. The wind blows the cart up to the windspeed by blowing on this surface like a sail. The prop is shaped so that the wind would turn the prop in the other direction if it wasn't geared to the wheels.
So the cart is blown up to 10mph with the prop acting as a sail. Once it reaches this speed, the prop's shape and position is such that the prop now exerts a force in the opposite direction to motion.


I think dannym3141 is right. Also, I suspect that the counter-winding prop at speed, in addition to providing a positive forward force from the tailwind acting on the prop surface area, is also providing a negative forward force (ie, lift) on the front side of the prop. This "double-use" of wind lets the car go a bit faster than the wind in a method similar to a sailboat on a close or beam reach (where a 10mph wind can provide both push and lift to a properly trimmed sailboat sailing roughly perpendicular to the wind, maybe reaching up to 15mph speed).

I would still like to see Mythbusters tackle it, though.

Yes fuzzy, the lift is what i was referring to with the "exerts a force in the opposite direction to motion". However the term lift is easy to confuse someone who isn't considering engineering/science terms

>> ^Aemaeth:
>> ^therealblankman:
"In the end the physical world does not succumg to scientific theories..."
Huh?

This simply means science was wrong. Could such a thing be possible?


How was science "wrong" in this example, considering there isn't a "grand unified theory of not travelling faster than the wind"? What happens in the video can be completely explained using highschool physics and the fact that a few armchair physicists on the intarwebs are unable to do so is hardly an example of science being wrong.

It takes a minute to wrap your head around this one, but I think it makes sense.

I'm still fighting with the equivalence of the treadmill scenario, though. On the treadmill, the energy input is through the wheels and the output is through the propeller. Similar to the "push" the wife gave the original device, the test device would need to be held in place on the treadmill until the propeller got going, otherwise it would simply fall off the back of the treadmill. A 10-mph treadmill does not equal a 10-mph tailwind, since the treadmill guarantees 10-mph, while the tailwind only guarantees what air friction will impart to the device. (Which would be less than 10, right?)

Once it's going, it makes sense to me, though - the rotational energy from the wheels is converted into lift (directed horizontally) in the propellers. As long as there is energy being delivered to the wheels, the propeller will spin and provide more lift, which will *supplement* the forward motion of the wheels and cause the device to travel forward. I'm assuming the supplement is steady, though - that is to say it doesn't continue to accelerate, but reaches a steady "overspeed". (As opposed to a perpetual motion machine, which would continue to accelerate.)

What's helpful to me is to picture the device being allowed to run off the treadmill into dead air - it would propel itself somewhat using the residual "lift" from the propeller, but would eventually coast to a stop. Now, taking that image, if we introduce a tailwind, that could introduce enough energy to keep the device moving forward. Maybe? Hrm.

HRRRRRRRMMMM.

proof you don't need a physics background to argue physics.

>> ^ReverendTed:
"I'm still fighting with the equivalence of the treadmill scenario, though."


It's all about reference frames. Say there is a car travelling at 10mph, and there is a tailwind of 10mph. From the reference frame of the car, the road is moving backwards at 10mph, and the air is still. The treadmill merely simulates such a reference frame by making the "road" move backwards at 10mph.

"On the treadmill, the energy input is through the wheels and the output is through the propeller."

Sources of kenetic energy changes depending on the reference frame. For example, say there is a car travelling at 10mph, and there is a tailwind of 10mph. The car and wind will have kinetic energy in this "stationary" reference frame. From the "moving" reference frame of the car, however, the air is not moving, and has no kinetic energy, but the road is moving backwards at 10mph and will have kinetic energy.

The treadmill here is supplying the kinetic energy to move the "road" backwards at 10mph. Now, the treadmill is not a perfect simulation of a moving reference frame. But the important thing is that forces acting on the cart is consistent.

"Similar to the "push" the wife gave the original device"

The "push" from the wife was unecessary. The cart would have gained enough speed eventually, albeit slowly.

"the test device would need to be held in place on the treadmill until the propeller got going, otherwise it would simply fall off the back of the treadmill."

Ideally, we'd use an infinitely long treadmill to do the simulation =P. Then you won't need to hold on to the cart.

"Once it's going, it makes sense to me, though - the rotational energy from the wheels is converted into lift (directed horizontally) in the propellers. As long as there is energy being delivered to the wheels, the propeller will spin and provide more lift, which will *supplement* the forward motion of the wheels and cause the device to travel forward. I'm assuming the supplement is steady, though - that is to say it doesn't continue to accelerate, but reaches a steady "overspeed". (As opposed to a perpetual motion machine, which would continue to accelerate.)"

Your intuition from here on is pretty much correct.

"... and the terrorists will win."

I should go back and redact my previous post, because I went at it from the angle that what they show in the video was fact, but they claimed it was perpetual motion, which it isn't.

THEY ARE LYING.

1) The machine outside is either being towed, the video is playing backwards, or the contraption is actually moving INTO the wind, not with it.

2) The reason why the treadmill actually proves them WRONG is easier to understand when you realize the air speed of the air inside the room is NOT a factor. The ONLY airspeed you should consider is the airflow past the propeller. The air 1/100,000 inch away from the outer edge of the propeller could be 300mph, and it wouldn't impact this one bit. So...

It is a simple machine.

OUTSIDE:

Air pushes propeller (actually a turbine), which turns elastic band, which turns gears, which turns wheels, which push against the ground.

When you put it on the treadmill...

Ground pushes wheels, to gears, to eleastic, to prop, pushes air.

While on the treadmill, the contraption only generates enough thrust to move it barely to the right, while, if you were to believe THEIR physics, it should move to the right at a velocity equal to the treadmill PLUS an amount because the airflow THROUGH the propeller should be GREATER than the speed of the treadmill. It is obviously moving MUCH slower to the right than the treadmill moves to the left, therefore disproving them. Remember, EVERYTHING not going through the propeller blades ARE NOT CONSIDERED IN THE "WIND MOVING OVER GROUND IS EQUAL TO GROUND MOVING UNDER WIND" FALSEHOOD. ONLY the air through the propellers can be considered. Everything else is smoke and mirrors.

>> ^Payback:
"but they claimed it was perpetual motion, which it isn't."


They never claim it's perpetual motion. They only mention perpetual motion as an arguement people use against them.

"Air pushes propeller (actually a turbine), which turns elastic band, which turns gears, which turns wheels, which push against the ground.

When you put it on the treadmill...

Ground pushes wheels, to gears, to eleastic, to prop, pushes air."

Every action has an equal and opposite reaction. When you say "turns wheels, which push against the ground" the gound also pushes on the wheel, just like the treadmill pushes against the wheel.

"While on the treadmill, the contraption only generates enough thrust to move it barely to the right, while, if you were to believe THEIR physics, it should move to the right at a velocity equal to the treadmill PLUS an amount"

It should move to the right at a velocity equal to the treadmill PLUS an amount, with respect to the treads, NOT the camera.

"It is obviously moving MUCH slower to the right than the treadmill moves to the left"

Yes, because now you're looking at the cart from the camera's reference frame, NOT the treads reference frame.

GUYS this is impossible!

Look at it this way. Let's give a 10 mph wind an energy value of 10. Craft is stopped it receives 10 energy units. It accelerates to 5 mph, now the wind is only hitting it at 5 mph from behind, it recieves 5 energy units.

Now, here comes the tricky part. At 10 mph the energy from the wind = 0 There is no possible way in the world to cheat that. You cannot make a craft powered by the wind that goes away from the wind faster than the wind.

>> ^Drachen_Jager:
Now, here comes the tricky part. At 10 mph the energy from the wind = 0 There is no possible way in the world to cheat that. You cannot make a craft powered by the wind that goes away from the wind faster than the wind.


You are ignoring the propeller. The propeller HAS to spin as long as the cart is moving relative to the ground. The blades of the propeller moves through the air EVEN if the wind is not blowing, and the ROTATING BLADES generates force. Analyze the forces acting on the cart and you'll see this actually works. It's very counter-intuitive and tricky, but the physics behind it actually works, which is why it's pretty cool.

Mentality:

The energy is coming from the air not the ground.

Once the car reaches a speed equal to the wind it no longer gets any energy input.

In your example you are taking energy from the ground. The ground is not providing energy here, so what you're saying is impossible, for the same reason that the car, when pushed in a windless environment does not go speeding off. It coasts to a halt.

>> ^Payback:
I should go back and redact my previous post, because I went at it from the angle that what they show in the video was fact, but they claimed it was perpetual motion, which it isn't.
THEY ARE LYING.
1) The machine outside is either being towed, the video is playing backwards, or the contraption is actually moving INTO the wind, not with it.
2) The reason why the treadmill actually proves them WRONG is easier to understand when you realize the air speed of the air inside the room is NOT a factor. The ONLY airspeed you should consider is the airflow past the propeller. The air 1/100,000 inch away from the outer edge of the propeller could be 300mph, and it wouldn't impact this one bit. So...
It is a simple machine.
OUTSIDE:
Air pushes propeller (actually a turbine), which turns elastic band, which turns gears, which turns wheels, which push against the ground.
When you put it on the treadmill...
Ground pushes wheels, to gears, to eleastic, to prop, pushes air.
While on the treadmill, the contraption only generates enough thrust to move it barely to the right, while, if you were to believe THEIR physics, it should move to the right at a velocity equal to the treadmill PLUS an amount because the airflow THROUGH the propeller should be GREATER than the speed of the treadmill. It is obviously moving MUCH slower to the right than the treadmill moves to the left, therefore disproving them. Remember, EVERYTHING not going through the propeller blades ARE NOT CONSIDERED IN THE "WIND MOVING OVER GROUND IS EQUAL TO GROUND MOVING UNDER WIND" FALSEHOOD. ONLY the air through the propellers can be considered. Everything else is smoke and mirrors.


EXACTLY!

Furthermore, wind can not blow into the propeller to make it spin the right direction to provide thrust in the opposite direction the wind is blowing.

There is NO POSSIBLE WAY that this machine is even wind powered at all... just think about it people

http://en.wikipedia.org/wiki/Propeller

A propeller is not a sail... end of the frickin' discussion

Guys i'm going to quote myself because you appear to have overlooked this.

>> ^dannym3141:
Also, i'll explain how this works:
The prop on the back of the cart has a large flat surface area. The wind blows the cart up to the windspeed by blowing on this surface like a sail. The prop is shaped so that the wind would turn the prop in the other direction if it wasn't geared to the wheels.
So the cart is blown up to 10mph with the prop acting as a sail. Once it reaches this speed, the prop's shape and position is such that the prop now exerts a force in the opposite direction to motion.
Because of the 10mph wind, the cart experiences no air resistance and is only experiencing the resistance of the wheels on the ground (and some from the gears).
While this seems counter intuitive, as though it's perpetual motion, it isn't because the prop can only power the cart if the wind is creating the environment of decreased air resistance!


The TREADMILL scenario is EXACTLY THE SAME as the scenario in which a cart is travelling at in a 10mph wind for the purposes of this experiment. If you cannot understand how that is true then you might as well give up trying to understand this cart right now.

The treadmill does NOT simulate the cart getting up to 10mph because that is done by the wind and is pretty much a moot point. Many people can make a cart that travels at wind speed. That's not the challenge. They are in fact using a treadmill to negate any external factors and conduct the experiment in a controlled environment.

So we all accept that the cart can REACH wind speed (10mph in our example), and now the question is can the cart accelerate PAST wind speed?

Consider a cart travelling at 10mph in a NO WIND environment. What are the forces acting on the cart excluding internal forces?
- A force to maintain the cart's 10mph speed.
- Friction from the road acting on the wheels.
- Drag worth 10mph (Air resistance equal to 10mph headwind on a stationary cart)

Consider a cart travelling at 10mph in a 10mph TAILWIND. What are the forces acting on the cart excluding internal forces?
- A force to maintain the cart's speed of 10mph (in this case the wind)
- Friction from the road acting on the wheels.
- No drag (air resistance)

Now consider a stationary cart on a treadmill going at 10mph. What are the forces acting on the cart?
- A force to maintain the cart's position on the treadmill.
- Friction from the treadmill acting on the wheels.
- No drag (air resistance) - because it is a still environment, no wind.

If the cart moves forward along the treadmill, it is now accelerating past the simulated speed of the wind. The question now is "What are the forces acting on a cart accelerating in either situation if it does indeed accelerate?" Now it is time to reconsider the forces acting on a cart accelerating past wind speed.

Consider a cart in a 10mph wind travelling at 12mph. What are the forces acting on the cart excluding internal forces?
- A force to maintain the cart's speed of 12mph.
- Friction of the road acting upon the wheels.
- Drag (air resistance) of 2mph.

Consider a cart on a 10mph treadmill travelling forward at 2mph. What are the forces acting on the cart excluding internal forces?
- A force to maintain the cart's 2mph speed (note that the wheels are travelling at 12mph, but because the treadmill is going at -10mph, the cart only MOVES at 2mph)
- Friction of the treadmill on the wheels.
- Drag (air resistance) of 2mph.

This is very basic mechanics. I have laid it out and spelt it out for you to demonstrate that the cart on a treadmill running at 10mph is the exact same for the purposes of this experiment as a cart travelling 10mph in a 10mph tailwind.

If you can't understand this, then you have no right to argue whether or not this cart can or can't work. This is the undeniable scenario you have to work with. From these premises you base your argument regarding whether or not the cart does or does not travel faster than the wind.

You can argue whether or not my explanation is correct, or indeed whether the cart works (despite that it has been shown to work), but you cannot argue about the treadmill vs. wind simulation.

DannyM3141

"Consider a cart in a 10mph wind travelling at 12mph. What are the forces acting on the cart excluding internal forces?
- A force to maintain the cart's speed of 12mph.
- Friction of the road acting upon the wheels.
- Drag (air resistance) of 2mph."

What force would maintain the cart's speed beyond 10 mph? The wind is taking energy away, not providing energy at that point. You have to at least explain where the energy is coming from for your scenario to make any sense.

Ok, folks - here's a mental exercise that I hadn't considered. This helps me understand it a bit. danny mentioned in a comment to me that the ideal test on a treadmill would be an infinitely long treadmill. Ok, let's imagine that.

Are you ready? Here we go:
Device is placed on infinite 10mph treadmill in still air (and not held). It begins to "fall" backward away from the point of placement at 10mph because it's not moving relative to the treadmill surface.

BUT - the propeller and device exert an amount of drag in air, so the device can't QUITE stay with the treadmill as it travels backwards at 10mph. This drag "pushes" the device forward slightly on the treadmill (so it's going, say, 9.5mph backwards on a 10mph treadmill). This would happen with any wheeled device. However, in this case the motion which we'll call 0.5mph "forward" relative to the treadmill surface, is beginning to spin the wheels and therefore the propeller which increases the drag (or adds "lift" or whatever you want to call it) and causes the device to continue slowing its backwards progression.

Eventually, this approaches 10mph - and this far it's still easy to understand - a simple wheeled device with a sail would approach this point (but never reach it, for all of the reasons already stated). Now, picture this point where the device is traveling 10mph relative to the treadmill surface (standing still with respect to us, off the treadmill), and consider that the propeller is spinning furiously behind it. This is why it will advance forward some small amount above the speed of the treadmill.

>> ^Drachen_Jager:
DannyM3141
"Consider a cart in a 10mph wind travelling at 12mph. What are the forces acting on the cart excluding internal forces?
- A force to maintain the cart's speed of 12mph.
- Friction of the road acting upon the wheels.
- Drag (air resistance) of 2mph."
What force would maintain the cart's speed beyond 10 mph? The wind is taking energy away, not providing energy at that point. You have to at least explain where the energy is coming from for your scenario to make any sense.


Ok, the cart has been accelerated to 10mph and at this point the wind is exerting the maximum force upon the cart that it can exert. Because the wind is BLOWING the cart along, it is forcible rotating the wheels (because the wheels are in contact with the ground).

The prop is shaped such that, when the cart is travelling at 10mph, the prop is spinning and exerting a lift force. Now what happens is that the air resistance faced by the cart (the 2mph one we keep mentioning) is now "sucked in" by the prop, and expelled out the back, causing a pressure difference which pulls the cart forward. This pressure difference is made possible by the wind.

That was what i was trying to get across poorly when i was talking about the prop exerting a force. The pressure difference. But like i say, i'm still thinking and still working it out

I'm really sorry if this is not concise enough for you, i've been thinking about it non-stop for 3 days and mulling it over, asking questions, answering questions, and i'm a bit burnt out. (and in a rush, my patience to explain things here is waning)

"Ok, the cart has been accelerated to 10mph and at this point the wind is exerting the maximum force upon the cart that it can exert."

No. The wind is exerting 0 force on the cart. The maximum force is when the cart is standing still, there is a difference of 10 mph at 0 mph for the cart and 10 for the wind. At 10 mph for the cart and 10 for the wind the difference is 0. There is no energy, ergo it is impossible.

Think of it in simpler terms. The wind is a car, driving 10mph you are on a very efficient tricycle being pushed by the car. Now, assuming that you're frictionless you'll go 10 miles per hour but how can you go faster? Even if you could outpace the car you'd no longer be getting any energy from it.

The principle is the same with the wind. If you're travelling 10 mph in a 10 mph tailwind the air appears perfectly still to you, since there is no 'relative' wind you cannot be getting energy from it.

I love the ridiculously over simplified discussions. First of all, these guys fail for putting it on a treadmill as it is not equal because there is a difference between a belt providing a force to spin wheels (the power involved is coming from the treadmill, in real life this can only happen with an incline and gravity, which is not the same as treadmill moving wheels).

A few problems with this is the reality of a 10mph wind versus moving 10mph with a 10mph tailwind. The reality of travelling 10mph with a tailwind is not exactly the same as a 0mph wind. There is static friction differences, rolling resistance changes, the turblence and wind drag change based on the speed, etc.

Can a plane take off if it is put on a giant treadmill? (assuming the prop/jet doesn't blow across the wings?)

"Can a plane take off if it is put on a giant treadmill?"

Yes, the prop is pushing the wind, it's not a car where it's driven by pushing against the ground. I knew this already but the Mythbusters did this one and showed that it doesn't effect take off distance at all (measured against a stationary object).

Yes you're right, the maximum force is exerted when the cart is stationary.

As i say, i have been thinking, explaining, learning and questioning the whole thing for 3 days now and in my rush to make that reply (surprisingly i have more to do than armchair science) i made a small error in my english and i apologise.

However i can address some of the fallacies raised in the 3 previous posts:
1. The tricycle is a completely inappropriate analogy because the tricycle does not have its own means of propulsion in the scenario you suggest.

2. Also, the analogy of the car simulating the force of the wind doesn't work either because the car doesn't accurately (or perhaps at all) imitate the pressure differences at work. Nor the (lack of) air resistance, etc. etc. etc. The car analogy is far far too simple (and wrong) to introduce and try to make arguments with!
(please think about these points some more because i can't begin to imagine how you think it's an appropriate simulation)

3. No one claims that travelling 10mph in a 10mph tail wind is EXACTLY the same as a treadmill in all ways. What people say is that it is an adequate simulation for the purposes of a controlled environment. That is the reason a treadmill is used - in order to eliminate any external influences that may "cheat" the system. (as i said in my posts wherever i remembered or had the remaining motivation, they are exactly the same for the purposes of this experiment)

4. You're wrong joe about the belt supplying the force somehow changing the entire situation. If you still can't grasp how the treadmill simulates the wind, after all i've tried to explain in simple terms (the only ones i have), i can't say anything further to convince you otherwise.

5. "I love rediculously over simplified discussions" -- i assume this is somehow an attempt at mockery, your disdain has been noted and i'm sure all parties shall feel ashamed for taking part in this discussion now that you've told us you don't like it. No need for stuff like this

I'm sure some of the things i've said here are wrong. It's been a long time since i did any mechanics or physics, and all i'm trying to do here is explain how i think it works and help others to understand how i think it works. I think i've been at least illustrative and literate in my arguments, and until i see a literate and illustrative argument that makes me think i'm wrong, i'll stick to it. So i invite corrections and more intelligent people to set me straight (in fact i'd love it), but so far that hasn't been done. I still think my explanations are more convincing (and based in fact and my own attempt at science) than other ones on the thread so far

If all this crap so far doesn't convince, then fair enough, let's agree to disagree. However i do believe this cart is possible and real and i think time will show that i was justified to think that - even if not for the exactly right reasons. About the treadmill, though, i (and others who have said it long before i) am definitely right.

"The tricycle is a completely inappropriate analogy because the tricycle does not have its own means of propulsion in the scenario you suggest."

Neither does the "propeller car" a means of propulsion means a motive force, POWER! It has none.

Simple question.

At 10 mph in a 10 mph tailwind, where does the power come from?

That's the only question you need to ask. What force is present to allow the car to accelerate beyond the speed of the tailwind?

>> ^Drachen_Jager:
Simple question.
At 10 mph in a 10 mph tailwind, where does the power come from?
That's the only question you need to ask. What force is present to allow the car to accelerate beyond the speed of the tailwind?

Simple. When the cart is traveling at 10mph in a 10mph tailwind, the wheels are rolling along at 10mph, turning the propeller at the rear.

"Simple. When the cart is traveling at 10mph in a 10mph tailwind, the wheels are rolling along at 10mph, turning the propeller at the rear."

The wheels are not gaining power from anywhere though. All forces acting on the wheels are acting to take power away.

The wheels are the means by which we're able to extract energy from the wind while the device as a whole remains stationary in it. The wheel-propeller apparatus extracts energy from the wind more efficiently than drag alone (e.g.: a sail).
This is because the propeller is moving against the air even when the air is not moving relative to the frame of the device.

What? That makes no sense Ted. You have to be getting energy from somewhere to maintain speed. You admit you are not getting energy from the wind but you seem to be unable to explain where the energy might be coming from. Don't you see the problem here?

>> ^ReverendTed:
The wheel-propeller apparatus extracts energy from the wind more efficiently than drag alone (e.g.: a sail).


I am saying that the energy comes from the wind.

If you're going the same speed as the wind there is no energy, no wind either. Once you're going faster than the wind the air will take energy away.

>> ^Drachen_Jager:
If you're going the same speed as the wind there is no energy, no wind either. Once you're going faster than the wind the air will take energy away.

That's true if you're relying entirely on drag.

If we picture this device with no wind - then it just sits there. There's no energy to be transferred, fine.

However, if there IS any wind, in order to be stationary in it we must to be traveling as FAST as it, which means the wheels will be spinning on the road beneath, turning the propeller. A propeller turning in stationary air will provide thrust.

Oh my god Ted. How is the ground providing energy? Is it magical ground?

In order for an object to accelerate you must apply energy to it. You've conceded the wind is not providing energy any longer once the cart reaches wind speed, the ground can't just give energy, it doesn't work that way. If the ground provided energy like that we'd just plug all our appliances into the nearest hillside.

>> ^Drachen_Jager:
Oh my god Ted. How is the ground providing energy? Is it magical ground?
In order for an object to accelerate you must apply energy to it. You've conceded the wind is not providing energy any longer once the cart reaches wind speed, the ground can't just give energy, it doesn't work that way. If the ground provided energy like that we'd just plug all our appliances into the nearest hillside.


The ground is providing energy in exactly the same way as the threadmill is doing in the indoor experiment. Just imagine that we don't have wind over ground, but that the earth is rotating "under" still air... it's just another frame of reference... but as valid as any other valid frame of reference. In fact the cart will try to slow down the earth in its challenge to outspeed air-vs-ground speed! But I don't think the earth will bother much (... just a tiny bit).

The ground is inert. It cannot provide energy. The treadmill has an electric motor and is providing energy. What is so complicated about that that you don't get it?

>> ^Drachen_Jager:
The ground is inert. It cannot provide energy. The treadmill has an electric motor and is providing energy. What is so complicated about that that you don't get it?

What is your definition of inert?
The earth doesn't have an electric motor inside, but surely it is moving big time (around itself, around the sun, and who knows to what other reference), so I wouldn't call that inert. Maybe it "looks" inert to an object that is standing still on it (because that would be the natural frame of reference), but to all the other frames of reference it doesn't look inert at all.
If I would be "standing still in the universe", and the earth was about to hit me, I think that I would feel quite some energy.
In fact if there would be consistent earth-winds (never mind where that would come from), and we could make a big enough cart, we could in fact slow down the earth (so I don't see this happening in practice any time soon).

If you ride your bike as fast as you can, and then you fall, I'm sure you will personally feel the energy of the earth! ;-)

Another one: I'm drifting in a balloon on the wind, and I drag a little trolley on a long electric rope behind me over the ground. The trolley is having a little generator, and will supply some power to the balloon. So the ground is providing energy! If I just keep sitting in the balloon, not touching the ground in any means, there is no way I will get that extra energy.

Honestly, to say that the ground is the only source of that energy is over-simplifying, whereas in fact it is the difference between the ground-speed and air-speed which is the source real source of the energy here.

"What is your definition of inert?"

Inert for these purposes. ie "does not provide energy in this scenario."

"If you ride your bike as fast as you can, and then you fall, I'm sure you will personally feel the energy of the earth!"

No, you will feel the energy of your body's momentum relative to the earth. If you lie down on the ground it doesn't hurt, if the earth were what you were feeling in your example it would hurt the same to just lie down as it would to skid across the ground.

"I'm drifting in a balloon on the wind, and I drag a little trolley on a long electric rope behind me over the ground. The trolley is having a little generator, and will supply some power to the balloon. So the ground is providing energy!"

No, the wind is providing the energy. The ground is helping you to harness that energy. Big difference. If the earth were providing the energy you wouldn't need wind in this scenario.

Honestly guys, you're wrong. How you can think you're right is beyond me, it's obvious you know nothing about physics yet you insist on arguing with people who do know what they're talking about. It's bizarre, like that clip where Joe Scarbourough argues with the Israeli expert on Palestine/Israeli relations. Sure the guy has made it his life's work to study the subject but you've read a couple of newspaper articles that disagree with him, therefore you are the more informed party.

Only you guys don't even have a couple of newspaper articles, just your own misguided intuitions. If you really believe this works build it. If you put a patent on it you've solved the world's energy problems and you will quickly become the richest person on earth! Seems like a worthwhile prize for success to me.

*sigh*

I never said>> ^Drachen_Jager:
You've conceded the wind is not providing energy any longer once the cart reaches wind speed, the ground can't just give energy, it doesn't work that way.

I haven't conceded anything of the sort. ALL of the energy comes from the wind, it's just harnessed more efficiently than by using drag alone.

Your argument is that being stationary in the air causes us to lose all energy transfer. For the frame of the vehicle, this is absolutely true, but as the frame of the vehicle becomes stationary in the air, the propeller is NOT.

This isn't perpetual motion any more than a ramjet (though it is an entirely different principle). It's just not immediately intuitive.

Also, this is new.

Ted. See my last two paragraphs above. Until you go out and do it you apparently won't understand that it doesn't work. If you can make it work you'll be wealthy beyond your wildest dreams. So, if you're right, go out there and become the next billionaire!

"Also, this is new."

Are you saying that wind is like a giant ruler? Man go learn some physics, come back when you have a basic understanding of the principles involved...

"If you really believe this works build it. If you put a patent on it you've solved the world's energy problems and you will quickly become the richest person on earth! Seems like a worthwhile prize for success to me."

I have to disappoint you in three ways:
1. it has been build, and shown that it works (maybe you should build one to convince yourself)
2. one will not solve the world's energy problem with it (BTW, we have already windturbines to harvest wind energy...)
3. so I also doubt seriously that one will become the richest person on earth with it

1) Show me where the evidence is, so far the evidence (one poorly shot video) is about as convincing as the evidence for Bigfoot.

2) If you're moving as fast or faster than the wind you're no longer "wind powered". You're harnessing a new form of power which I will dub "Magical Thinking".

3) If you can truly tap into this new and heretofore undiscovered source of power you will surely become the richest person on earth

Read the following if you still don't believe me.

http://www.make-digital.com/make/vol11/?pg=60&pm=2&u1=friend

http://www.boingboing.net/2008/12/03/directly-downwind-fa.html

http://blog.dotphys.net/2008/12/physics-and-directly-downwind-faster-than-the-wind-dwfttw-vehicles/

This argument is still going on?

Yes, the argument about bigfoot is still on... and yes there will always remain people doubting about DDWFTTW also.

Drachen_Jager said: "Read the following if you still don't believe me"
my answer:
link 1: poor attempt to rebuild the DDWFTTW trolley, so no surprize it's not working... but that doesn't proof it's impossible.
link 2: lot's of people on boingboing giving good hints why it IS working, and the usual sceptics also surely.
link 3: poor blogger is a non-believer and a professor... shame on him, but again no proof it doesn't work

Wouterd

If it's so easily proven then why hasn't anyone proven it yet? The concerns with the only proper wind propulsion (not treadmill propulsion) video anyone's shot are legitimate, it certainly looks to me like there's a line coming off the front of the cart. If it's so easily done then how come nobody's shot a video showing that there's no strings attached?

Why don't you do it? It's pretty simple.

Your questions have been asked and answered many times already, just go through the links you mentioned yourself.
But basically:
1. the "threadmill proof" is a real proof, and typically one of the most convincing ways of proofing the concept.
2. the "outdoor proof" is more complicated to perform in a convincing way, i.e. perfectly flat and straight road, and strictly controlled windconditions (both strenght and force). Most all attempts in that direction would hardly convince any non-believer, as there would always be something that is not 100% clear or controlled. Indeed, the Bauer proof might have been (even) more convincing if it also showed that nobody was pulling the trolley, but even then, there would be many reasons why non-believer could still doubt about its validity.

I guess you've never heard of a "Wind Tunnel" Wouterd?

Goes to show how much you know about science I guess.

Let's not get personal, no need for that. We just have a difference of opinion, that's all!

BTW, I do know the concept of a wind tunnel, but I don't have one in my garden. ;-)
But I guess nobody really sees the point in spending the time and money to try to proof the concept inthere. What's the point after all? It's not gonna be profitable anyway, and I don't need to be convinced anymore anyway. So, I would just need to do that to convince you? I'm spending already way to much time and effort just on this forum...

BTW, do you believe/know that ice-sailors can go faster than the wind downwind VMG wise?

No, sail boats and Ice 'sailors' can go faster than the wind but not DOWNWIND.

You really don't know what you're talking about. How many post secondary physics classes have you taken? Given that the answer is zero (and I think that's obviously a safe assumption) why would you think that you are capable of judging whether something like this is possible or not?

>> ^Drachen_Jager:
No, sail boats and Ice 'sailors' can go faster than the wind but not DOWNWIND.


"not downwind" -> if you mean:
1. "icesailors can not go dead downwind in a STRAIGHT LINE faster than the wind": than I fully agree with you
2. "ice-sailor can not go faster than the wind downwind VMG-wise" (i.e. they can NOT catch up with the wind downwind or with a balloon just drifting with the wind by zigzagging downwind), than you should reconsider or ask some of those guys. That's a fact!

Let me know what your position is on point (2).

If you don't agree on point (2), than I'm not going to bother you any further. ;-)
But if you agree on point (2), than that should be a good basis to believe that the trolley concept could work.

BTW, I don't think I need to specify how many physics classes I went through, not sure if it is relevant at all here, but I can safely say it's more than what you currently think. No worry! ;-)
Let me know if all your physics courses allow you to see where this guy might have gone wrong: http://home.roadrunner.com/~tadhurst/DWFTTW.htm

Another way to realise this could really work:
Replace the air (=light, not-dense), by something (lotsa) more dense and heavy... like water, or liquid mercury. Whether we take air, or a liquid like water or mercury, doesn't seem to me make any difference to the "theory" that such cart could never move faster (DDW) than the medium (gas or liquid) that it is in.

Now think of the propellor blades of the cart in the liquid mercury. If the blades were not angled, the cart would reach (almost) speed of the liquid... as the balloon (or a non-angled-bladed-cart) does in air. No problem there! Right?

Now start angling the blades a bit (=positive pitch), so as the cart moves at close to liquid speed, do you think that the blades will just start "milling" through the liquid? That would take lots of power!? (like from friction in the cart set-up...). No, they will find the way af least resistence, by "cutting" through the liquid, and starting to move the cart faster than the liquid. So this will rather accelerate the cart (small effort), instead of milling through the liquid. Smart blades!? ;-)

In fact, exactly the same thing happens in air, so it is my feeling that the thought experiment with a dense liquid is more convincing.

Your milage may vary...

Now you've explained it in a way which shows exactly where you went wrong.

Yes the blades will accept energy from the wind. Yes they could power the cart forwards. But when the cart reaches close to the speed of the wind friction wastes enough energy that you can't go faster. If you had only good friction and no bad friction you could reach the speed of the wind, but at that speed the propeller isn't getting any rotational energy from the wind. Should the cart be pushed faster than the wind the air would flow backwards over the propeller forcing the cart to slow down (even the "perfect" frictionless cart).

Nope, the air is not flowing backwards over the propellor (when it is pitched correctly), just make a vector drawing (or check the ones in previous DDWFTTW threads)!

Again my main question: What is your position on ice-sailors going faster than wind downwind VMG-wise?