Can a wind powered vehicle travel down wind, faster than the wind?

[jakee 1,263]

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ok I thought we were talking about going faster than the wind. I didn't
realize we were only talking about going directly downwind.

Maybe you should have READ before you sounded like an idiot then, eh?

Do you want to have an ideagasm?

[vanair 0]

True

[rehmwa 2]

Simple - charge up a bunch of light weight batteries with a windmill and use it to power a plane.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[DrewEckhardt 0]

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Yeah, I read it and it will NOT go directly downwind and sustain a speed faster than the wind. It is impossible. What they are proposing to do is akin to powering a car with electric motors that run off current produced by generators driven by the wheels.

Working models prove that it's not impossible.

http://www.youtube.com/watch?v=86vhmTp7tKU

Consider a line parallel to the propeller shaft intersecting its disk area. I'd speculate that workable gearing + propeller pitch combinations result in the propeller's point of intersection along all such lines moving backwards relative to the vehicle such that their a average total velocity with respect to the ground is less than the wind's.

That seems more intuitive to me than the simplified explanation of the relative wind always hitting the blades at an angle.

[Belgian_Draft 0]

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Yeah, I read it and it will NOT go directly downwind and sustain a speed faster than the wind. It is impossible. What they are proposing to do is akin to powering a car with electric motors that run off current produced by generators driven by the wheels.

Working models prove that it's not impossible.

http://www.youtube.com/watch?v=86vhmTp7tKU

Consider a line parallel to the propeller shaft intersecting its disk area. I'd speculate that workable gearing + propeller pitch combinations result in the propeller's point of intersection along all such lines moving backwards relative to the vehicle such that their a average total velocity with respect to the ground is less than the wind's.

That seems more intuitive to me than the simplified explanation of the relative wind always hitting the blades at an angle.

If you look at the streamers on the vehicle you can see that there is a crosswind component and they are NOT going directly downwind.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[Belgian_Draft 0]

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What you are talking about is perpetual motion. Obviously not possible to anyone with any grasp of physics. The machine they are building is NOT perpetual motion, because it does require wind.

Remember that even though the air is still around the machine AT the speed of the wind, there is still a velocity over the ground. This machine can not run without wind, ie it's not perpetual motion.

Look around the Internet about this. It's not a hoax.

A perpetual motion machine is what they are trying to build. Just like the guys with their magnet motors. The only way to recover energy from a wind...the ONLY way...is to have a relative wind. Just because the air is moving over the ground doesn't mean it can provide energy to a vehicle that is moving in the same direction at the same speed. To quote the builder, "It sounds like a perpetual motion machine — but you’ve got the wind as an external power source,”
The wind is only an external power source when there is a relative wind. Same direction at the same speed means no relative wind. It really is that simple.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[bfilarsky 0]

That's a great explanation. Problem is, they're actually doing it.

http://www.wired.com/autopia/2010/06/downwind-faster-than-the-wind/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+Index+3+%28Top+Stories+2%29%29&utm_content=Google+Feedfetcher

[masterrig 1]

Hell, I proved that under a Manta on my first static-line jump!


Chuck

[shropshire 0]

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[Belgian_Draft 0]

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That's a great explanation. Problem is, they're actually doing it.

http://www.wired.com/autopia/2010/06/downwind-faster-than-the-wind/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+Index+3+%28Top+Stories+2%29%29&utm_content=Google+Feedfetcher

That's the same article linked in the OP.
And it is still wrong for the same reason...once the vehicle is going the same speed as the wind it can no longer be used as a source of energy because there is no relative wind.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[wolfriverjoe 1,362]

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That's a great explanation. Problem is, they're actually doing it.

http://www.wired.com/autopia/2010/06/downwind-faster-than-the-wind/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+Index+3+%28Top+Stories+2%29%29&utm_content=Google+Feedfetcher

That's the same article linked in the OP.
And it is still wrong for the same reason...once the vehicle is going the same speed as the wind it can no longer be used as a source of energy because there is no relative wind.

Ok, I think I get it.

It isn't sustained. They are simply building momentum by using the propeller as an energy gathering system, and then transferring that energy back to forward thrust once they reach the same speed as the wind (zero relative wind).

You could do the same thing with a flywheel. Use the wind to spin the flywheel up to speed and to propel the vehicle. Then when you reach the same speed as the wind, use the energy stored in the flywheel to accelerate beyond the speed of the wind.

You'll be able to achieve a speed faster than the wind, but you won't be able to sustain it.

Big difference.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[bfilarsky 0]

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That's a great explanation. Problem is, they're actually doing it.

http://www.wired.com/autopia/2010/06/downwind-faster-than-the-wind/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+Index+3+%28Top+Stories+2%29%29&utm_content=Google+Feedfetcher

That's the same article linked in the OP.
And it is still wrong for the same reason...once the vehicle is going the same speed as the wind it can no longer be used as a source of energy because there is no relative wind.

Yes, I completely understand that there is no relative wind. However, there is relative motion (of the ground) with no relative wind.

Lets assume this vehicle has been moved by some other means to the speed at which there is no relative wind - say 10 mph (ie moving downwind at 10 mph with a 10 mph tailwind). The wheels are turning with a tangential velocity of 10 mph, and driving the fan through a reduction box.

Now, we know the fan will create a propulsive force to push the vehicle forward. With no wind at all (meaning a 10 mph frontal relative wind), this force would necessarily be less than the force created in the opposite direction by the wheels, otherwise you would have violated the first law of thermodynamics (conservation of energy).

However, with the wind, we now have a fan pushing into what it feels is static air. This will provide more force than the same fan turning with a 10 mph "headwind" Hence, it can accelerate. This does not break the first law of thermodynamics, as there is wind which powers the vehicle.

Once again, while intuitively it does seem like its impossible, it does obey the laws of physics.

Check out this video: http://www.youtube.com/watch?v=xHsXcHoJu-A

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That's a great explanation. Problem is, they're actually doing it.

http://www.wired.com/autopia/2010/06/downwind-faster-than-the-wind/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+Index+3+%28Top+Stories+2%29%29&utm_content=Google+Feedfetcher

That's the same article linked in the OP.
And it is still wrong for the same reason...once the vehicle is going the same speed as the wind it can no longer be used as a source of energy because there is no relative wind.

Ok, I think I get it.

It isn't sustained. They are simply building momentum by using the propeller as an energy gathering system, and then transferring that energy back to forward thrust once they reach the same speed as the wind (zero relative wind).

You could do the same thing with a flywheel. Use the wind to spin the flywheel up to speed and to propel the vehicle. Then when you reach the same speed as the wind, use the energy stored in the flywheel to accelerate beyond the speed of the wind.

You'll be able to achieve a speed faster than the wind, but you won't be able to sustain it.

Big difference.

Nope. They are sustaining it. The propeller is linked directly to the wheels, its not accelerated and then bled of energy.

[nigel99 151]

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What you are talking about is perpetual motion. Obviously not possible to anyone with any grasp of physics. The machine they are building is NOT perpetual motion, because it does require wind.

Remember that even though the air is still around the machine AT the speed of the wind, there is still a velocity over the ground. This machine can not run without wind, ie it's not perpetual motion.

Look around the Internet about this. It's not a hoax.

This has really been bothering me as I can normally grasp engineering principles fairly quickly. I don't believe that they are going directly down wind.

The models on the treadmill had me going for a while but I believe they are misunderstanding the principles at work (on the little models). The treadmill is driving the wheels in effect what we are seeing is a gearing principle at work.

That said I am not a sailor and so it may be that I simply don't understand a key principle involved somewhere.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[jakee 1,263]

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The models on the treadmill had me going for a while but I believe they are misunderstanding the principles at work (on the little models). The treadmill is driving the wheels in effect what we are seeing is a gearing principle at work.

I would prefer to see the model in a windtunnel than on a treadmill but... the wheels driving the prop in nil (relative) wind seems like it's the same on a treadmill as in a windtunnel.

I think Bfil's post above is the key.

How do sailing boats and ice boats travel faster than the wind when tacking? The interaction between the solid connection to the ground and the moving wind. With a boat with a static sail they need to be moving crosswind to a degree to allow the sail to continue feeling a relative wind. With the geared prop they still have a solid connection between the ground and the wind* and since the prop is moving, not static, it can still feel a relative wind in the right direction even when the craft is travelling at or above the windspeed DDW.


* That's a rubbish sentence, but I'm not sure how to put it better than that.

Do you want to have an ideagasm?

[bfilarsky 0]

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What you are talking about is perpetual motion. Obviously not possible to anyone with any grasp of physics. The machine they are building is NOT perpetual motion, because it does require wind.

Remember that even though the air is still around the machine AT the speed of the wind, there is still a velocity over the ground. This machine can not run without wind, ie it's not perpetual motion.

Look around the Internet about this. It's not a hoax.

This has really been bothering me as I can normally grasp engineering principles fairly quickly. I don't believe that they are going directly down wind.

The models on the treadmill had me going for a while but I believe they are misunderstanding the principles at work (on the little models). The treadmill is driving the wheels in effect what we are seeing is a gearing principle at work.

That said I am not a sailor and so it may be that I simply don't understand a key principle involved somewhere.

The treadmill is about the best way to demonstrate the effectiveness of this. Remember frames of reference? You can accurately calculate a physics problem from any frame of reference (so long as we're not approaching the speed of light). This is precisely why wind tunnels work - the physics don't change whether you fly the airplane through still air, or blow air over a still aircraft. The treadmill is, essentially, a wind tunnel for the car. If the car can travel up the treadmill, it can travel up an equivalent hill with a tailwind, and faster than that wind.

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The models on the treadmill had me going for a while but I believe they are misunderstanding the principles at work (on the little models). The treadmill is driving the wheels in effect what we are seeing is a gearing principle at work.

I would prefer to see the model in a windtunnel than on a treadmill but... the wheels driving the prop in nil (relative) wind seems like it's the same on a treadmill as in a windtunnel.

I think Bfil's post above is the key.

How do sailing boats and ice boats travel faster than the wind when tacking? The interaction between the solid connection to the ground and the moving wind. With a boat with a static sail they need to be moving crosswind to a degree to allow the sail to continue feeling a relative wind. With the geared prop they still have a solid connection between the ground and the wind* and since the prop is moving, not static, it can still feel a relative wind in the right direction even when the craft is travelling at or above the windspeed DDW.


* That's a rubbish sentence, but I'm not sure how to put it better than that.

Yes, you've got the right idea.

[Belgian_Draft 0]

I will stick to my view that what they are claiming to do is not possible. Once the vehicle reaches wind speed there is no source of energy available to them except whatever energy has been stored in the mass of the vehicle. If geared correctly some of this can be used to briefly accelerate past wind speed but then they have a relative wind working against them, not for them. You cannot use wind coming directly at the vehicle to power the vehicle into the wind. Can't happen. It matters not what they do to the pitch of the prop or gearing. If it were possible then aircraft would not need engines.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[ryoder 1,403]

1. We are not talking about a fixed sail; We are talking about a propellor.

2. The vehicle runs on the ground, and the prop is powered by the wheels.
Last time I looked, an "aircraft" was defined to be a vehicle that flew without touching the ground.
So comparisons with aircraft are irrelevant.

"There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones.

[Belgian_Draft 0]

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1. We are not talking about a fixed sail; We are talking about a propellor.

2. The vehicle runs on the ground, and the prop is powered by the wheels.
Last time I looked, an "aircraft" was defined to be a vehicle that flew without touching the ground.
So comparisons with aircraft are irrelevant.

It was a comparison made to show the absurdity of the idea. They are trying to build a "free energy machine".

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[bfilarsky 0]

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I will stick to my view that what they are claiming to do is not possible. Once the vehicle reaches wind speed there is no source of energy available to them except whatever energy has been stored in the mass of the vehicle. If geared correctly some of this can be used to briefly accelerate past wind speed but then they have a relative wind working against them, not for them. You cannot use wind coming directly at the vehicle to power the vehicle into the wind. Can't happen. It matters not what they do to the pitch of the prop or gearing. If it were possible then aircraft would not need engines.

So how do sailboats go upwind (not directly), faster than the wind?

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1. We are not talking about a fixed sail; We are talking about a propellor.

2. The vehicle runs on the ground, and the prop is powered by the wheels.
Last time I looked, an "aircraft" was defined to be a vehicle that flew without touching the ground.
So comparisons with aircraft are irrelevant.

It was a comparison made to show the absurdity of the idea. They are trying to build a "free energy machine".

For about the 20th time, no they aren't. They only way this thing works is with wind. Wind=energy. Haven't you ever seen a windmill? Are those free energy machines? Yes I know they have relative wind, but relative wind doesn't affect the energy available, it just makes it harder to capture. Check out their website. http://www.fasterthanthewind.org/2010/05/we-done-good.html

A San Jose State University Project. Last time I checked, Universities weren't in the field of perpetual motion, as most have physics departments.

[Belgian_Draft 0]

As I have already stated several times, it is not only possible to exceed the wind speed using it for power, or even travel against the prevailing wind direction, but it has been doen for centuries. It is no big deal and 2-3 times wind speed is way behind the 8-ball when it comes to record speed. It only requires skillful jibing and tacking.
What I am saying is that it is impossible to travel in the same direction at the same speed as the wind for more than a brief period witout having some sort of energy storage device aboard. The vehicle discussed in this thread can only exceed wind speed by keeping a crosswind component. The video in the link clearly shows a crosswind component coming from the vehicles right and causung the streamers to push left.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[bfilarsky 0]

So how does the one on the treadmill work?

[ryoder 1,403]

SlashDot has picked up the story today:

http://tech.slashdot.org/comments.pl?sid=1676544

"There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones.

[MakeItHappen 15]

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So how does the one on the treadmill work?

The wheels start to skid and the treadmill pulls it across.
eg the energy is added by the treadmill
That's why the steering is needed as the wheels skid momentarily on one side and then the other.

.

.
Make It Happen
Parachute History
DiveMaker

[Belgian_Draft 0]

Energy is supplied by the treadmill. The treadmill rotates the wheels which turn the prop whose thrust is ballanced against the rolling resistance of the vehicle. With careful tuning a static equilibrium can be found.
The difference between running one on a treadmill and running one on the earth in a wind is that on a treadmill the energy is supplied continuously and could run as long as the treadmill was running. Treadmill stops, vehicle stops. Running in a wind on the earth the one and only source of energy is the wind, which the vehicle will lose once it is going the same speed as the wind. Sure, the wheels could drive the prop, but this removes more energy from the system than the prop can return due to losses in the system and zero or near zero relative wind.

HAMMER:
Originally employed as a weapon of war, the hammer nowadays is used as a
kind of divining rod to locate the most expensive parts adjacent the
object we are trying to hit.

[ryoder 1,403]

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

stationary air & moving surface == moving air & stationary surface

The wheels/propellor mechanism effectively applies a gear-ratio to the propulsion supplied by the wind.
On forums.randi.org, I found this:

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Take a wineglass, preferably one with a base that's around the same diameter as the widest part of the glass. Lie it on its side and position a finger horizontally, under the stem. Move your finger forward, and the glass will roll forward faster than your finger.

"There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones.