# Wind-Powered Car Actually Moves Faster Than Wind Speed, Answering Tricky Physics Question

Car travels directly downwind faster than the wind, creators say

Wind-Powered Car This wind-powered car traveled directly downwind faster than the wind, according to its creator. Faster Than The Wind

A California team recently tested a wind-powered car that can actually outrun the wind, adding more fuel to a lingering physics debate.

In a test two weeks ago, the car hit a top speed 2.86 times faster than the wind, according to its creators. Some physicists say this should be impossible, but car-builder Rick Cavallaro says that's exactly what happened on May 16. What gives?

Cavallaro had funding from Google and Joby Energy to build the car, basically an aerodynamic foam chassis attached to a wind turbine, with the San Jose State University aerodynamics department.

Wired’s Autopia blog features the car and Cavallaro’s quest to prove it is possible to travel directly downwind faster than the wind.

The wheels turn the car’s propeller, and the prop thrust pushes the car, which turns the wheels, Cavallaro says. It's not a perpetual motion machine, because the prop is also using wind energy as an external power source.

He says the toughest part was designing a transmission system to transfer power from the wheels to the propeller. Design and construction took almost a year, and Cavallaro has detailed photos and schematics on his blog.

His team made eight test runs May 16 at New Jerusalem Airport in Tracy, Calif. The next step is a land-sailing record certified by the North American Land Sailing Association, Cavallaro says.

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Not too hard to figure out. You use the wind speed to propel the vehicle, but if this is designed properly you only need to use a fraction of the energy from the wind to propel it to the winds speed. With the extra energy you store it and then use that energy accelerate the vehicle beyond the winds current speed.

My "explanation" of how it works in the article is a bit unfortunate. That was intended to be my explanation as to why so many people think it should be impossible.

@Setarip: We don't make any use of stored energy. This vehicle can go more than 2.5X windspeed, directly downwind, steady-state.

Ah ok, Sounds pretty interesting. What was the actual windspeed during this?

Yes KH, that is a very good point (about sailing not used car salesmen), but that isn't always true. Wait... never mind, that is always true, you can't go faster than the wind compared to the direction of the wind.

The thing that makes me uneasy is that the car goes downwind, and that, as KH said, would make "You lose the power of the wind when you reach the windspeed..." My only explanation for getting any faster would be from the inertia of the propeller, which could go faster than the wind, because it still has energy from the wind when the wind (relative to the speed of the car) was faster. This wouldn't be anything special, heck, I could do that in my back yard. I'd just say it is a clever energy capturing storing device, with a big fly wheel.

i'm sure it works. wind varies in angle. it kinda snakes around. plus, it blows in bursts. i'd guess that during the trip downwind that the propellor blades would have moments where it slowed down and sped back up. good job.

Thank you Setarip for the logical explanation - there's the energy that the wind transfers into spin on the huge propeller blades, and there's the energy required to move the prop assembly (the car) forward in a straight line. There's no reason that the two should have to cancel each other out at the speed of the wind that powers the blades - the wind itself is not linearly pushing this car.

>> you can't go faster than the wind compared to the direction of the wind.

Indeed you can. Ellison's speed in the recent Americas Cup on a direct downwind projection was nearly 3X the windspeed.

>>My only explanation for getting any faster would be from the inertia of the propeller

I assure you the inertia of the propeller does not come into play. This cart can go DIRECTLY downwind at better than 2.5X windspeed continuously.

The wind blows against the back of the car and propeller. The wheels turn, which is geared to turn the propeller for forward thrust, against the direction of the wind. ie. backwards. Once the speed of the wind is reached, the backward thrust pushes the car beyond that speed. I'm just guessing. It's the only way that I can think that it would work.

You know, I didn't believe it at first. But it makes an odd kind of sense if you think about the work done on the air being at a different speed than the work done by the air.

The answer is simple, the faster you go against the wind, more power will come from the wind.

Ex: If the wind is at 50km/h and you go downwind at 50km/h this mean you have the power of a wind at 100km/h.
(sorry, english isn't my native language

Skeptics think that the wind is turning the prop, and the car is turning the wheels, and that’s what makes the car go,” Cavallaro said. “That’s not the case. The wheels are turning the prop. What happens is the prop thrust pushes the vehicle.

This is a quote from the Autotopia article, and it doesn't make sense to me. If the prop is directly connected to the axles, and if the car starts moving with no outside intervention than the statement is incorrect per se. If you push it to start it then the next question would concern thrust.

As far as I know air can only flow one way at a time across an airfoil, so if the wind comes from the rear of the vehicle than wouldn't the thrust vector also be downwind, the opposite to the movement. By this reasoning you wouldn't get any thrust until you exceeded the wind speed.

It may be that they have found a new principle at work and simply haven't recognized it yet. Of course they said bumblebees couldn't fly, but it would be nice to see some numbers.

>>
I didn't mean to say that the car can't go faster than the wind. I intended to point out that the same angular forces which cause the boat to go at a higher speed apply to the car as well... it just isn't as seemingly logical due to the change of where the angular forces are being applied.
<<

You're quite right.

>> Why doesn't someone put a model of this car into a wind tunnel?

Wind tunnels are for vehicles that go into the wind. We put this on a treadmill - so it will advance slowly (even on an inclined treadmill) when going just above wind speed.

@Reeseman:
Initially the vehicle is pushed by the wind as a bluff-body. As the cart begins to move, the prop begins to spin. As it approaches wind speed, more and more of the prop becomes unstalled (starting at the tip). At some point well below wind speed the prop is creating significant positive thrust. This continues to well above wind speed (2.86X is our best run so far - several runs in the 2.75X range).

>>It may be that they have found a new principle at work and simply haven't recognized it yet.

Nope. We use all the old tried and true principles - and actually understand them quite well.

@TicezyIntelligent:

I'm skeptical and suspect the vehicle is just storing and releasing energy to briefly exceed the wind speed. The data presented on their website shows no steady state. It shows the vehicle accelerating, but the vehicle brakes _immediately_ after obtaining its maximum speed. The videos corroborate the posted data. One can see it braking as soon as it hits its maximum speed.

Do you really have any steady state runs with data?

>>I'm skeptical and suspect the vehicle is just storing and releasing energy to briefly exceed the wind speed.

In point of fact we don't even have a way to use stored energy to accelerate. To do that we'd have to slow the prop down as we increase the speed of the wheels. But our gearing is fixed.

>> The data presented on their website shows no steady state. It shows the vehicle accelerating, but the vehicle brakes _immediately_ after obtaining its maximum speed.

I don't recall exactly what data we posted on the blog, but I can tell you the only good data runs we have to date were done on the runway at New Jerusalem. I had to brake before running off the runway for some of the runs (I was still accelerating), and I topped out briefly (at around 40 mph if I recall correctly) for another couple - before having to brake to avoid running off the relatively short runway).

>>Do you really have any steady state runs with data?

As I mentioned, we have a couple of runs where I topped out briefly before having to brake. We also have small scale models that run indefinitely on the treadmill - even climbing an incline. But more importantly, the analysis shows that it can clearly exceed the wind speed by a large margin - steady state.

In effect you have created a greater drag than a propeller's area would have. The propeller is pushing against the wind. The two forces are creating this action. It would be easy to suggest that a plane can travel faster than wind since it has a propeller and motor. In this approach the wind is both the sides powering the action.

>>In point of fact we don't even have a way to use stored energy to accelerate. To do that we'd have to slow the prop down as we increase the speed of the wheels. But our gearing is fixed.

You can still store energy and accelerate beyond the wind speed with fixed gearing. This is because you are using props with a variable pitch. This effectively does change the gearing (as far as thrust is concerned). You can start with a pitch that is favorable to getting up to speed. Then once you get up to the wind speed, the drive extracts this rotational energy by changing the pitch of the props to produce rearward trust. Your website says the pitch is adjustable from the cockpit.

More importantly, your claim of steady steady has not be demonstrated. A steady state period that last longer than the entire earlier phase of the experiment is needed to prove the vehicle isn't just storing and releasing energy. Carl Sagan said, "extraordinary claims require extraordinary evidence."

When this car goes downwind, wind does not rotate propeller blades. Blades are rotated by the wheels through transmission. The propeller creates a thrust against the direction of the wind (i.e. backwards). This is how it goes faster than the wind.

OK....my 2 cents

The article was interesting and even a bit entertaining.

Off to the medicine chest for me.

I believe it is possible after reviewing the physics of sailing and watching this video www.youtube.com/watch?v=aJpdWHFqHm0

The pitch of the props are equivalent to a sailboat sailing at close reach which allows it to go faster than the wind.

It would still be cool to see the full scale model go for a long time.

Mechanical Engineer.

Sailboats leverage the wind against the water to travel faster than the wind, but at an angle. Wheeled vehicles with sails do the same thing.

Going directly downwind, the propeller would slow as it reached wind speed, because there is no relative wind. Even with gearing or pitch control, no wind is no wind. This is crap.

It also cannot propel itself directly into the wind, although that would seem more plausable, and would have a better chance of duping people, which I'm sure is what they are trying to do. Soon you will see a call for investors. Maybe they should buy Moller International's 'investor' list.

@ziploc

So the wing starts in stall. If the vehicle acts as a bluff body then you have a mechanism to prevent counter rotation. Is that the ratchet mechanism I saw referred to on your site? Okay so far, so early on it's a kite. Now as the speed increases the prop unstalls gradually until it provides thrust. To increase beyond wind speed the thrust must add to the force of the wind. So now it's like swimming with the tide. To go any further I have to assume that the total energy output is equal to the force of the wind on your vehicle, minus losses else wise we are in perpetual motion territory. This implies to me that your are using the prop to recover the lost energy due to friction of one type or another. Effectively you are using your prop to increase your efficiency. Do you have any numbers on that.

@poindextrose: "You can still store energy and accelerate beyond the wind speed with fixed gearing. This is because you are using props with a variable pitch."

Nope -- the only way to use the stored energy from the drivetrain (prop, etc) to accelerate is to slow down portions of the drivetrain (say the prop) and use that energy to speed up the wheels. With fixed gearing that is impossible.

Change the pitch of the prop all you wish, but you'll never be able to use any of that stored energy with the fixed gearing.

Nice MAKE though.

>>You can still store energy and accelerate beyond the wind speed with fixed gearing.

Actually, you can't without dragging the wheels along for the ride. To USE the energy stored in the spinning prop you have to slow it down. This will slow the wheels down. Unless you skid the wheels, the cart will slow down.

There's no period of time that conclusively demonstrates steady-state. But we've done it ridiculously long with our model on a treadmill. And again, the analysis shows it can do so.

The prop is driven by the wheels. When the body of the vehicle is at windspeed the prop is climbing through the air faster than that.
Look at it this way. If you're standing along the track with a windspeed of 10 (pick your preferred units) this cart drives past you with at 20. Its prop is climbing through the air at 25. The air along the track just before the cart is moving at 10. Just after the cart passes it's moving in the same direction at 5.
They're slowing the wind down just like any other windmill by extracting energy from it.

@PhillnYork The prop doesn't slow down because it is directly attaching to the wheels via gearing. It's not a one way thing; if the wheels turn, the prop turns, if the prop turns, the wheels turn. What you are saying is that it's one way reaction that the prop turns the wheels but the wheels don't turn the prop..which isn't this case.

btw thanks ziploc for responding to all the comments with your information! This has the most genuinely conversational comments that aren't involved in a flame war that I've seen on here.

>>
It's not a one way thing; if the wheels turn, the prop turns, if the prop turns, the wheels turn. What you are saying is that it's one way reaction that the prop turns the wheels but the wheels don't turn the prop..which isn't this case.
<<

Actually, for practical reasons we do have a custom machined ratchet in the middle of the prop-shaft that prevents the prop from driving the wheels in the forward direction. This was done in part so we wouldn't have to rapidly brake the prop when braking the cart. This isn't really much of an issue as it happens. And now that we have a variable pitch prop we do just the opposite - we use the prop to brake the wheels at the end of the run (before applying the disk brakes).

The other reason for that particular ratchet is related to a transmission approach we considered (spool and take-up reel) but didn't need to implement in the end.

Downwind faster than true wind speed is easy, just like with an actual sailing vessel. In light to moderate breeze, the vessel's downwind velocity causes the wind velocity, relative to the vessel, to increase and the airfoils' angle of attack to decrease; sailors would say boatspeed has caused the apparent wind to shift forward.

On the wind-car, the apparent wind to the prop blades is quite a bit higher than the true wind and the angle of attack is similarly decreased, as prop & vehicle speed increases. Obviously, once the vehicle speed equals true windspeed, the apparent wind to the prop will still be significantly higher than true windspeed, allowing the vehicle to further accelerate.

What I'd really like to know is what happens when the wind car heads up, i.e. turns into the wind. Assuming the car doesn't capsize, reaching across the wind should be easy & it should also be able to sail at slightly less than a 90 degree angle to the true wind.

Thin Air guys, any interest in getting some hiking straps and big, empty parking lot so you can build us some polars? ;)

@ziploc Oh, so..it's really the propulsion of the propeller that's pushing the car? The only function of gearing the two together was for braking? (I'm just vocalizing my thought process) Or, wait, the wheels turn the prop which generates thrust. I think it's that. I'm sure it's said somewhere in the article/comments, I just needed to wrap my head around it.

I need to pay attention in my classes more..

Why not show us the equations that show what you're claiming to be achieving? If the wind is truly (only) in the direction of the vehicle movement, there is no propulsion force applied once the speeds of the vehicle and wind are equal. Likewise, the air will slow the vehicle once it is moving faster than the wind.

If there is a component of the wind that is perpendicular to the direction of travel, then THAT can result in further propulsion of the vehicle. I suspect that this is exactly what is being seen and believe this vehicle is functioning exactly like a sailboat.

Bryan, it *is* functioning "exactly like a sailboat" to the extent that the sails of the vehicle are on one long continuous, spiralling broad reach while the chassis drives directly downwind.

You're tripping up on the part that gets a lot of people -- you're considering the air relative to the chassis as relevent (and it's not). It's only the air over the sail that's important and just like the latest America's Cup boats, the sails of the vehicle have no problem achieving downwind VMGs of greater than the wind while on a broad reach

>> so..it's really the propulsion of the propeller that's pushing the car?

Yup.

>> The only function of gearing the two together was for braking?

Nope. The wheels turn the prop.

>> the wheels turn the prop which generates thrust.

Yup.

gravitational acceleration

>> gravitational acceleration

I'm not sure where you're going with that - but as a skydiver I'm all for it.

Hey guys,

I saw this a few years ago and at first thought it was a hoax. After alot of thinking and calcs, I figured out it wasn't, and here is why.

It all works due to the relatice velocity between the vehicle and ground. Most people discredit it by thinking 'if wind velocity is zero, than there is nothing to derive power from and thus the vehicle cannot go faster than wind'. This is NOT a sailboat. Any analogies as such are incorrect. A sailboat travels through two different fluids. This is travelling through air, and over a solid surface. With that being said, here is how it works:

There are two main forces in our simplfied assumption, the thrust produced by the prop, and the drag at the wheels. Note that the drag at the wheels is created becase the wheels drive the prop.

For this to work, two conditions must be met.
1) The force of thrust MUST exceed the drag at the wheels in order for the vehicle to accelerate.
2) The power absorbed by the wheels must be GREATER than the power produced by the propeller to comply with the second law of themodynamics.

So, what is power? There are several ways to calculate, all of which arrive at the same value. The simplest is force times velocity, F*v. Now heres the key. The velocity of the wheels is much higher than the velocity of the prop, due to the tailwind. This allows the force of thrust at the prop to be GREATER than that of the wheels, while still compling with rule #2, that the power at the wheels must be greater. This occurs IF and ONLY IF the difference between the airspeed (relative wind across vehicle) and groundspeed is sufficiently high to allow for the Fxv of the wheels to be HIGHER than Fxv of the propeller.

Done. Any questions?

@andyhenault:

Your explanation of the power-flow is correct. You model the propeller as a "black-box", that uses power to create a force F = P / v.

But I disagree with: "This is NOT a sailboat. Any analogies as such are incorrect."

You can go one abstraction level lower, and look at the individual propeller blades. They are in fact analogous to sails on a broad reach. The torque that drives the prop is analogous to the wind-perpendicular-force-component on the keel.

This youtube animations explain it best:
watch?v=UGRFb8yNtBo
watch?v=zPFzHoubQzg

"A sailboat travels through two different fluids. This is travelling through air, and over a solid surface."

This is an irrelevant distinction. You could theoretically build a dead-downwind-faster-than-wind boat as well. It would have a water turbine instead the wheels.

@eyytee

Yes, you can look at it like a sailboat on a broad reach, but it overcomplicates the problem. It's easier to take one step back and look at the net power, which is what I have done. If you want to complicate it, you might as well look at the losses over the airfoils, and the L/D ratios. If you break it down to a sailboat on a broad reach, you get a lot of dirty vector math to figure out.

And yes I know you could do this with a real boat, but the losses would be retarded with a water turbine.

@ziploc

sorry i misread, i thought the vehicle was moving down a slope for some reason. in place of my smart aleck comment, instead of gravitational acceleration, i would say momentum or something or other...

If the windspeed was 10 mph i.e., im guessing that means the thing went 28.6 mph which is crazy. What if the transmission has like a really heavy chain so once its got its push from the wind it generates enough momentum from the weighty gears and the chain to accelerate?? I dont know, im just trying to go with the easiest explanation

@ poopshoop

"What if the transmission has like a really heavy chain so once its got its push from the wind it generates enough momentum from the weighty gears and the chain to accelerate??"

No. To accelerate the cart, you also need to accelerate the transmission. You cannot do this by momentum stored in the transmission, because that would slow down the transmission & the cart.

"I dont know, im just trying to go with the easiest explanation"

watch?v=E7vcQcIaWSQ
watch?v=g8bxXRQtcMY

Again guys,

This is not a sailboat. It's going directly downwind. Yes, a sailboat can travel faster than the true wind speed, but only at an angle. Directly down wind, or a run for us sailing folks, a sailboat cannot go faster than the true wind speed. See my explanation above. That is how it works. It has nothing do do with vectors, it's all about power and the relative difference between airspeed and groundspeed.

(ring knocking sound)

Also,

@PhillinYork, are you actually a Mechanical Engineer? If you are, you should turn it in. Crack a textbook.

Actually, it all works due to the constant presence of a relative velocity between the vehicle and the air.

I am not an engineer nor a physicist and when I first discovered this mind twister early this morning I initially thought it was impossible. A hoax. Breaks the laws of physics. But after spending the morning thinking about it, I figured it out.

BTW, I am baffled why one of the creators claims that the moving wheels turn the prop that propels the vehicle that makes the wheels move, etc. This is perpetual-motion-machine type reasoning.

The key to understanding why this vehicle works starts with the wheels' contact with the ground. The rubber wheels' sliding friction is high enough to fully resist the force from the wind that's striking the vehicle.

To appreciate this better, imagine the vehicle were resting on an completely slippery, totally frictionless surface. The whole vehicle would quickly accelerate backward in response to the force of the wind until it was moving at 0 relative windspeed. The propeller would hardly move at all. Same story if it were an airplane in midair.

But because this vehicle can successfully hold fast against the impinging force of the wind, the propeller experiences constant relative windspeed so it starts to spin.

Once spinning, the propeller drives the vehicle forward via the transmission, converting wind energy into vehicle kinetic energy. Assuming the vehicle starts oriented into the wind, as the vehicle starts moving into the wind, the relative windspeed increases further and more kinetic energy is created in a virtuous cycle making the vehicle go faster and faster.

The only reason the vehicle won't accelerate forever is that drag, transmission friction, and rolling friction increase with speed until energy lost to them balances with the energy added by the spinning turbine.

The "faster than the wind" standard is an arbitrary benchmark. The speed of the wind is just one element determining how fast the vehicle can go.

The terminal speed is also determined by:
- how efficient is the turbine (provides more kinetic energy)
- how low is the mass (added energy makes the vehicle move faster)
- how low is the drag (good aerodynamics)
- how low is the transmission friction (good design)
- how low is the wheels' rolling friction (good tires)

@scsci

"To appreciate this better, imagine the vehicle were resting on an completely slippery, totally frictionless surface. The whole vehicle would quickly accelerate backward..."

What? Backward? It has a true tailwind, not a true headwind. See the video (youtube):

What you descibe is an UPwind cart, that goes against the true wind. This is a DOWNwind cart that goes with the true wind, faster than the true wind. This shows how the two types are related:

watch?v=za_rPKSwiyc

@eyytee

Ooops! Thanks for the correction and the links. I didn't realize it was a downwind vehicle. Will think about that case now.

Did some reading elsewhere. Wow. The physics behind it certainly takes deeper thought to get your head around. The whole thing is really about reference frames and energy transfer.

My previously described upwind cart that captures earth/air relative velocity energy to drive itself further upwind is using the same principles used by the downwind cart that captures earth/air relative velocity energy to drive itself further downwind.

In both cases the propeller/wheel linkage is used for the energy transfer. However, the upwind cart is anchored to the earth by wheel sliding friction and the downwind cart is anchored to the air by air resistance.

Fascinating.

So I have an idea. Im not an aerospace engineer or whatever. But im thinkin that the friction on the blades builds up and heats up the blades slightly. When the cooler air hits the warmer blades it makes a vortex simialar to a tornado around the blade tip. These help push extra air aound the blades providing a slight boost that increases with time.

I guess...

andyhenault: Yes, I am a Mechanical Engineer from Penn State University, with a specialization in fluid flow and heat transfer. I do computational fluid dynamics.

This nonsense reminds me of Wile E. Coyote using a house fan to power the sail on his skate board. You people are conmen or hoaxers.

Everyone else: Several of these conmen are logging in with different ID’s and posing as “Gee I thought it was wrong too, but it’s true.”

Thieves.

@scsci

Yes "going upwind" & "downwind faster than wind" are symetrical applications of the same principle. The difference is that the roles of air & surface are swaped. Here a university lecture about both types (youtube):

watch?v=4ZjX_DIosM8

@ PhilInYork

"This nonsense reminds me of Wile E. Coyote using a house fan to power the sail on his skate board."

You mean like shown here? (youtube):
watch?v=0CrXvOKPymk

The analogy that clicked for me is a robot resting stationary on an airport peoplemover belt moving at 10 inches/sec. The robot extends an arm with a wheel and rests it on the stationary ground next to the moving belt. A transmission carries power from the wheel to the robot's own wheels so it starts to move forward on the belt at some speed, say 2 inches per sec. The robot is now moving 12 inches/sec versus the ground.

No laws of physics are violated, the peoplemover has to draw that much more current. The robot has just "double dipped" on the energy differential between the belt and the ground. The robot could even adjust the gearing and move forward 14 inches/sec or however fast it wanted to, as long as the peoplemover motor could provide the energy.

The downwind cart is harnessing the wind vs earth speed difference to get it up to wind speed versus the ground, then "double-dipping" on that differential to move itself faster, like the robot. The cart takes advantage of the fact that unlike a calm day where 0 relative windspeed = 0 wheel speed, being carried along in a 15mph wind with 0 relative windspeed = 15 mph wheel speed. That "free 15mph" wheel speed, courtesy of the wind, can be tapped to move the card forward faster.

What if the wind were blowing 1000 miles an hour? Once the cart were up to windspeed, its wheels would be turning incredibly fast. Hook them to a generator and you could generate huge amounts of electricity that could then power a strong propeller to drive the cart forward much faster relative to the surrounding airmass.

The overall airmass moves that much slower afterward. Energy is conserved.

@PhillenYork: "This nonsense reminds me of Wile E. Coyote using a house fan to power the sail on his skate board."

ROFLAO -- are you just *trying to get on the wrong side of everything?

You do realize that you can put an ordinary house fan on a skateboard with a sail and use it to move the skateboard in the direction the fan is pointing.

JB

Streamers are not a reliable indicator of wind direction or speed because of the bias created by the means of attachment, and the ill-defined lift ratio.

Commercial indicators with any pretense to accuracy, are all pivoted and employ fixed areas exposed to the wind.

Lift and direction are not completely separable. That is why all commercial wind indicators are pivoted and[U] vertically[/U] mounted to avoid the influence of lift and gravity. Cheerleader pon-pons are NOT scientific tools.

If the streamer is bent over the top of the bar so pointing to the front, can you tell me how it can do anything else other then pass through the horizontal if it is to change?

When the cart is traveling fast enough, such that the tailwind is insufficient to sustain force to keep the steamer bent over the bar, gravity and the stress set up in streamer by the bending, will see it relax to the rear, no matter what.

All streamers have a minimum air flow necessary to keeping them aloft, so that change can occur well below WS. There is now nothing to stop simple lift keeping it that way.

I can’t believe I’m arguing science with people who believe Loony Tunes physics.

Ok, say Mr. Coyote is on his skateboard without a sail, just blowing an electric fan backward for propulsion, like an everglades airboat. Fine, he tools around until he runs out of extension cord. So he attaches a generator to the skateboard wheels and plugs the fan into it. Of course, the generator needs movement to create power, so Wile E. pushes the board with one furry foot until he generates the power needed to turn the fan. He can stop pushing then, because once the fan is going he can cruse forever on his perpetual motion machine.

“No” you say? The losses will make him slow down and stop, you say? OK, what if he replaces the generator and fan motor with sprockets and bicycle chain? Then surely he can just tool around with the wheels powering the fan, on and on and on. Heck he can even ACCELERATE with just the power from the wheels turning the fan, and finally catch that pesky Roadrunner. “No?” This won’t work? The power has to come from somewhere, you say?

Hmm, OK, so let’s say the wind is at the Coyote’s back and is blowing just as fast as he is going. He is caught in dead air with no wind resistance, and no tail wind. Then surely he will accelerate now right? RIGHT? No? Still no power input, you say? But, isn’t this last case exactly what these people claim will happen? That the vehicle going down wind at wind speed will accelerate?!?

The vehicle stores kinetic energy due to its forward speed and mass. By powering the fan with the wheels, the KE is consumed. This means the forward speed must decrease. If the fan is powered by the wheels, the vehicle slows down. That’s intuitive, right?

@eyytee: I looked at the video you linked. The whole front of the fan is covered in what they call a sail. It is not a sail; it is an air duct that directs the air sideways and back.

The air comes into the fan from all around the whole back side, so the resultant force from sucking air is weak. I have seen this in the CFD fan studies I have done. On the downstream side, the air is ducted around backwards, and that force overcomes the weak inlet force. Jet aircraft use the same exact trick to slow down by means of turning veins that turn the jet outlet flow back towards the front of the plane. The engines are running, but they push against the oncoming flow. That is what’s happening in the video.

If the sail had been mounted on its own mast, a foot or so away, then the fan outlet flow would propel the craft in the opposite direction. A sail mounted in this way is not a sail at all, but just a blockage in the way of the propulsion jet.

"You do realize that you can put an ordinary house fan on a skateboard with a sail and use it to move the skateboard in the direction the fan is pointing."

No. You can't. Try it.

And then switch to the Science Channel and stop watching Cartoon Network.

Phil

>> I can’t believe I’m arguing science with people who believe Loony Tunes physics.

I've got bad news for you. It's even worse than you think.

>>I have seen this in the CFD fan studies I have done...

You've done CFD studies!? And you can't sort out the astonishingly basic math involved with this?

Saw videos, know how a sailboat works, get that a sailboat travelling at an angle goes super fast, get that the propeller is traveling at an angle to the wind (like sailboat), & get that the wheel just keep the prop moving at an angle to the wind, the wind provides the ENERGY.

So now I'm doing it relativistic and building my own -> in space!

2.86 X Lightspeed here I come! (only Mr. Coyote can catch me!)

@Ziploc:
I just want to make sure: You are a key player in this project, and you are defending the Fan-&-Sail-on-a-Skateboard as feasible?

LOL -- PhillnYork, since where in the rules does it state that if the sail is right in front of the fan it isn't a sail?

A sail is nothing more than an object shaped to redirect air and thus create a force in a desired direction and what you called impossible is shown to be very easy.

Face it ... your CFD can't save you -- you fd up and wrote a check that bounced.

>>I just want to make sure: You are a key player in this project, and you are defending the Fan-&-Sail-on-a-Skateboard as feasible?
---

I just want to make sure: you saw the video where it was demonstrated - and you're sticking with your story that it's impossible. Just like with our DDWFTTW cart - huh?

Place the fan at a 90 degree angle, dead on from the side of the skate board. Angle the sail slightly away from pointing dead back. Hold fan close to the sail.
Better propulsion than from just pointing the fan back as a prop without the sail. And guess what... I never tried this, and never spent a day in proper education, but I don't need to, logic rules.
I suppose Coyote pointed the fan from the back into a wide open sail? No, that won't net much thrust. It doesn't disprove the oncept though.

Hey, cartoon understand wind technology better than most (self-)lauded phycicists. Remove spaces.

Check this out: ht tp://w ww.talk rational.org/showp ost.php?p=951299&postcount=922

@TAD: "since where in the rules does it state that if the sail is right in front of the fan it isn't a sail?"

A piece of paper scotch taped to a fan outlet is not a sail. It’s a duct.

@Colxxki: You are exactly right. A paper tube elbow mounted to the end of the fan that turns the air 180 degrees to flow in the opposite direction would work just as you describe. The cart would move against the fan direction. This is called a ducted fan.

In the video, the performance is bad because the builders were constrained with the task of making the duct look as much like a sail as possible in order to fool people. They succeeded.

@Ziploc:
Since you avoided my question, I’ll just assume you believe that a sail and a fan on a skateboard actually works.

I saw one DDWFTTW cart, I don’t know if it was yours. It was on a treadmill. They put the wheels down on the moving surface and the fan starts spinning. They let go and the cart accelerates forward to run off the front of the treadmill.

I laughed really hard; it was such a hysterical fake. I thought it was a joke, and wondered if they used a thread to pull it, or had a fan off-screen to push it. Then I realized they really were trying to deceive the viewers. Was that you?

I also saw one of a truck pushing your vehicle. Sort of like Wile E. pawing the ground to get the skateboard going. I don’t know what that was supposed to prove, momentum?

Sorry, but these are too easy to fake to be compelling. There are lots of impossible fake videos on the net. I also read your article and I noticed that you don’t have any reputable verification of your results. Did I miss something?

@PhilonYork: "I can’t believe I’m arguing science with people who believe Loony Tunes physics."

Then you obviously have yet to see their first video. Check out spork33 on youtube. The first one is about 7 minutes and shows his first cart going up a treadmill as 'proof' that DDWFTTW was possible. It actually ends with Wiley Coyote and the Loony Tunes theme song. Too bad their version of Laurel and Hardy stage a race between a turbine and prop cart isn't there. It was hilarious. These 'carteers' have been pushing this folly for 2 years now and soon NALSA will pop their bubble.
There is NO scientific evidence that supports their claims. NALSA will be their fist and last objective test, which is why I predict it will never happen.

Another problem that hasn't been mention here is that the gears cannot work as claimed. A force applied to a wheel cannot reverse itself, and oppose the force that drives it. There must be a fulcrum for the force, just as with a lever.

It looks that there may be no structure to the small cart, but round tube sections create a lot of drag, and there is the area of the gearbox and even the wheels.

That video shows the cart moving very slowly because the net force ( bluff body - turbine force) is small. The prop is working against the cart's motion. It is almost a constant speed because the balance, and so the net force, tends to remain the same over that distance.

Moreover, the wind test in the street shows the cart actually sliding with the wheels and prop not turning. That happens because the opposing forces become large, and traction breaks. Now it can slide.

The cart would go faster if the prop was removed and blown along by the bluff force alone.
The rest of the game is illusion created by simple deception, suggestion, and assumptions about streamers that have not been proven away from the cart.

>> Did I miss something?

@PhilInYork

Yes.

I should mention that humber has been our most ardent skeptic (and extremely insulting) for the duration. We've found the best way to address his arguments is to let him talk. You'll see.

Phil I was pretty much in agreement with you until you said the treadmill is a hoax. There is no reason for that to be a hoax because all it is, is the carts wheels being turned by the treadmill motor. There is no reason why that should not work and even some school kids built one as a science project and it works. I suggest you rethink the treadmill but I still agree with you the cart cannot go ddwfttw because at the wind speed there is no energy source. They have claimed the ground is an energy source, same as a treadmill but that is a load of horseshit!

The ice man

Correct me if i'm wrong but wouldn't it be possible to make it go faster than the wind if the gear attached to the prop was bigger than the ones attached to the wheels? Or would the resistance stop it from going faster?

@the ice man

Your "horseshit" argument notwithstanding, you really need to consider what the treadmill shows us. As far as the vehicle is concerned, it sees a surface (the treadmill belt) and the air (which is moving relative to the treadmill belt). Galileo, Newton, and Einstein tell us that it makes no difference whether the air moves over the surface or the surface moves under the air. The two are one and the same. This is known as Galilean relativity.

Ask yourself this... if you were on a sailboat far out at sea, and you felt a 10 knot breeze, but couldn't see land in any direction, couldn't you tack into that breeze? How do you know you're not in a 10 knot current with no "real" wind?

PhillnYork has it right. Some here have tried to make very complicated what is elementary: the first law of thermodynamics. Energy cannot be created from nothing. To accelerate into the wind requires a source of energy which is not present. QED.

BTW, no wind-driven object in contact with a surface -- soil, water, or ice -- can travel directly downwind even as fast as the true wind speed. Newton's second law comes into play. The force that the wind exerts on the object to drive it against surface resistance is matched by an opposite force pushing back and slowing the wind. So the air mass behind the object -- whether sailboat or other -- must move at a speed somewhat less than that of the unimpeded air mass around it. A free balloon can travel at exactly the same speed as the wind because there is nothing holding it back. But its speed relative to the wind is zero. Those who claim here that any kind of sailboat can travel straight downwind -- which is not the same as a 'broad reach' -- faster than the wind speed are confused or misinformed.

>> PhillnYork has it right.

And yet our cart does exactly what we claim. Kind of curious - huh?

>>Some here have tried to make very complicated what is elementary: the first law of thermodynamics. Energy cannot be created from nothing.

And we've explained in every way we can that we're not making any such claim. Our vehicle is propelled by wind energy. Pretty simple.

>>To accelerate into the wind requires a source of energy which is not present. QED.

Thus proving that sailboats can't tack upwind. QED.

Sorry, I don't see any need to respond point-by-point. You're simply wrong. We've shown the analysis and we've shown the proof. If you care to understand how it works, we're happy to explain it.

@kanbrain:

This "confused and misinformed" group with their 'impossible' vehicle will soon hold a ratified record issued by the North American Land Sailing Association. This record will show that under the personal supervision and scrutiny of an organization whose expertise in the field of wind powered land speed records is unparalleled, the vehicle exceeded the speed of the wind DDW by more than 2x wind speed.

Their report will show that there was no external power other than the wind involved. No stored energy was used to accelerate through the course. The vehicle left the course faster than it entered. The vehicle was not allowed to tack back and forth during any part of the run (including getting up to speed) The top speed was higher than the highest peak gust. The course was level (even uphill), Etc, etc.

What will you say about the "impossible" then?

@Ziploc:
I would like to personally apologize to you. I have been a condescending ass, while you have held your composure in the face of unfair attacks on your intelligence and ethics.

I finally put that degree I brag about to good use and did a free body diagram of your machine. You are right. It does work, and I can prove it. I also believe the cart on the treadmill trick.
Phil

PhillnYork, Kudos on the apology -- that's standup. Drop by and see us sometime and we'll let you drive it. :-)

>>I would like to personally apologize to you. I have been a condescending ass, while you have held your composure in the face of unfair attacks on your intelligence and ethics.
<<

@PhilInYork
WOW - you're one of a very small group of people that can admit they got it wrong and offer a genuine apology for insulting us. This thing is a brain-teaser - it's all about keeping an open mind and really being analytical. Congratulations for doing just that.

An object floating with the wind, such as balloon, cannot obtain energy from the wind, as it moves with equal speed. A windmill mounted on a truck moving downwind at wind speed will not even turn, as it is caught in dead air. A sailboat cannot sail directly downwind faster than wind speed.

If a windmill were on free-turning casters, it would accelerate to near wind speed and stop producing power. When a windmill is attached to the ground, however, it plays the ground against the wind. Because it is mounted fast, the blades can bite the wind and pull out energy. It is the DIFFERENCE between the ground and the wind that is the source of energy.

The DWFTTW cart has a rotor connected by gearing to its wheels. It is like a mobile windmill. It is always connected to the ground, even when it is moving. No matter how fast it is moving, it is always between the ground and the wind, and can harness the difference.

Imagine you are standing on a moving conveyer belt. Right next to your belt, is another belt traveling in the opposite direction. You kneel down on your belt, pull out a generator & wheel, and put the wheel in contact with the other belt. Your generator produces power. You then sit on a scooter with an electric motor and plug the motor into your generator. Your scooter will move, even if you are now moving faster relative to the other belt.

It doesn’t matter how fast the belts are going relative to the earth, so long as they are moving relative to each other. Either one could be stopped; they could both be moving in the same direction, just so long as they are moving relative to each other, your generator will play one belt against the other and create power for your scooter.

Now imagine the belt you are standing on is the wind. You are moving directly downwind at wind speed in a DWFTTW cart. You are maintaining your position with the wind, because you have a turning rotor that is in sync with it and holds your position relative to it. You are a windmill being blown by the wind, but your blades do not stop. The other imaginary belt is the ground. It is a source of power now, because the wind is blowing you along. You tap the power from the moving ground and feed it to the rotor. It pushes against the stagnant wind, and you go faster down wind.

The cart/treadmill trick works because there is no air movement in the room. If you just put the cart of the floor and pushed it, it would grind to a halt as one would expect. It is the fact that there is NO wind that allows the cart to play the still air against the moving conveyer, to create power.

kanbrain,

As you can see, Phil now disagrees with you.
It's not an obvious thing, but look at the situation you claim has no energy available. In order to be at zero velocity relative to the wind, you have to be at a non-zero velocity relative to the surface. THAT is a source of energy. It then just a matter og gearing.

Imagine Phils analogy of a generator, on;y repace it ithe a simple drive shaft turning a gearbox which turns the scooter wheels at a higher speed than the conveyer belt. The scooter moves forward.

The propellor is simply a propultion device like a driven wheel, set at a gearing ratio to provide a higher speed than the input wheels.

Ice man- Try standing on a treadmill on a pair of roller skates. Does the tradmill "Drive" the wheels, or does the frixction of the wheels cause you to go backwards.

You might try getting your head around the concept of relative velocities before calling "Bullshit" on something these guys have put years of work into, and which has been helped along by the likes of Joby, Google and, lately, NASA!!

@PhillnYork
Welcome to the ranks of the "believers" (aka kool-aid drinkers). Now be prepared to develop a thick skin and a lot of patience, and prepare for frustration. : )

"These 'carteers' have been pushing this folly for 2 years now and soon NALSA will pop their bubble.
There is NO scientific evidence that supports their claims. NALSA will be their fist and last objective test, which is why I predict it will never happen."

Humber,

I predict that when it DOES happen, you will not admit the above statement was wrong.

@PhillnYork "You are right. It does work"

But how do we know, that you not one of the "conmen" who "are logging in with different ID’s and posing as “Gee I thought it was wrong too, but it’s true.”" ? :-D

And we still disagree on the fan on skatebaord with sail issue. At which distance from the fan, does a "duct" become a "sail"? I think you have to apologize to Wile E. Coyote as well!

@eyytee:
The fan & sail on a skateboard is still a silly cartoon.

You're right that you have no way of knowing if I have been masquerading this whole time. For what it's worth, I have been posing on PopSci for years with this ID, taking perverse pleasure in trashing fake science. I have no trouble insulting conmen and fools, its just way too much fun. Eating crow once in a while is a small price to pay for the rare pleasure of learning something new.

Crow doesn't taste too bad when you wash it down with the kool-Aid.

@PhilInYork "taking perverse pleasure in trashing fake science. I have no trouble insulting conmen and fools"

And the only purpose of this vehicle is to fool skeptics like you, into arguing against it. :-D

Soon you will see, that there is even more perverse pleasure in trashing arguments from skeptics, who try desperately to debunk this. You will find that many of the internet skeptics are (unlike you) not smarter than actual cranks.

But the best is; You have even physics professors arguing against it. Google "dotphysics ddwfttw"

Have fun!

@Phil,

Sorry, but anyone who changes his mind that abruptly and that completely cannot be considered to be reliable let alone an authority. You were wrong about the treadmill before but right about the cart. Now you just wrong! You cannot draw more energy from your own relative wind than the energy you expend to create that relative wind. There IS a distinct difference between a "real" wind and a "relative" wind. Not to worry, maybe in a day or two you will change your mind again, eh?

@the ice man
"@Phil,Sorry, but anyone who changes his mind that abruptly and that completely cannot be considered to be reliable let alone an authority."

You confuse physics with religion. He did the math, and saw that his initial guess was wrong. Why should he stick to it, like it was a religious dogma?

"You cannot draw more energy from your own relative wind than the energy you expend to create that relative wind."

This is true. However the cart is not doing this.

Once the cart has achieved windspeed it is no longer receiving any energy from the differential between itself and the wind. In fact as it starts to move faster than the wind the cart/wind interface looses some of the cart's energy to the wind via drag.

At windspeed and beyond the cart is receiving all the energy accelerating it from the wind/ground speed differential.

Admittedly, it's hard to fully, intuitively grasp how the wheel/prop linkage accomplishes this since we are so used to seeing objects that just receive energy from only one other direct source. I am continuing to work to get my own head around it.

"There IS a distinct difference between a "real" wind and a "relative" wind. "

ice man,

Describe an experiment that would differentiate air moving past you as a "Real" as opposed to "Relative" wind....

@scsci "Admittedly, it's hard to fully, intuitively grasp how the wheel/prop linkage accomplishes this since we are so used to seeing objects that just receive energy from only one other direct source. I am continuing to work to get my own head around it."

search youtube for "eyytee", "coolaun", "axelerat3d" for intuitive animations

Once the car is already in motion, it is not inertia, but the conversion of the wind's kenetic energy thru the angular momentum/ velocity of the wind turbine. Inertia is just getting the car of the line until it gains momentum.
Since the car is already in motion, inertia (the object at rest will stay at rest unless acted upon by a form of energy sufficient to overcome the effects of gravity, all forms of resistance (air, rolling/sliding etc.) until it can no longer hold it's position)is not the law of physics in play here, when discussing a speed greater than the wind speed.
Then, once set in motion, the object tends to stay in motion, but still against these same external forces mentioned above.
The the wind turbine, which absorbs the wind's kinetic energy, converts it to angular momentum,(now taking advantage of FORWARD momentum, like you folks were mentioning with the airport people mover). This angular momentum, when applied in the form of a wind turbine pushing air from the front to the rear, is one form of an effective energy transfer for the car's weight and the other characteristics of physics which apply. Besides using air for propulsion, theoretically, it could also be applied towards the car's forward motion thru a weighted flywheel to another wheel intermittently. (like a kid riding a scooter, and every so often pushing off on the ground to increase his speed)if it's sufficiently geared to absorb some of the available torque from the turbine, converting it to a higher velocity than the other wheels are going, such as the 1800 rpm generator in a 10/60 rpm large wind turbine. Remember those little friction cars, where you push the car a few times and the highly geared and weighted flywheel sent the car off at tremendous speed across the ground? The heavy flywheel technology, utilized in Scaninavia since the 60s in buses and trolleys, was enclosed in a vacuumous chamber, and had same pole magnetic bearings...both of which all but eliminated friction and heat build up. The turbine is probably capable of something simular.

RossFW wrote: “Describe an experiment that would differentiate air moving past you as a "Real" as opposed to "Relative" wind.”...

OK. Two identical sailboats, one is on still water with a 10 Knot breeze blowing out of the East and the boat is moving West at 7 Knots. The other one is in a current moving at 10 Knots out of the West through still air and this boat is moving at 3 Knots to the East. Now, if they are far from land and have no other reference such as GPS, there is no experiment that can be performed aboard ship to determine whether the wind is real or relative. However, I am giving both captains a working GPS unit so that they can determine their true direction of travel. With that GPS information it is very easy to determine which boat is in the current with a relative wind and which is in the still water with a true wind. That is a perfectly valid experiment and it shows the difference between the two. Even though all the on-board observations are exactly the same, the GPS shows that the two boats are in fact moving in opposite directions. To make it even simpler, just give both captains a clear view of land.

The ice man

The vehicle in question has yet to be taught to use a GPS -- perhaps you could help us think of another way the vehicle could know.

>> The the wind turbine, which absorbs the wind's kinetic energy, converts it to angular momentum

@inventorworks2

The cart doesn't use a turbine. The big spinning thing is a propeller. The wind doesn't turn it - the wheels do. Also, this cart does not make use of inertia. Of course there is inertia in the moving vehicle and the spinning prop - that's inescapable - but they don't in any way help it to accelerate.

>> I am giving both captains a working GPS unit so that they can determine their true direction of travel

@t.i.m.

There is no such thing as a "true" direction of travel. Velocity is relative by definition. GPS will tell you your velocity relative to the surface of the earth. If the GPS receiver were programmed differently it could tell you your velocity in the ECIF (earth centered - inertially fixed; i.e. non-rotating) frame. It's all a matter of what you want to know your velocity relative to.

I’m not the first guy to think of this, but I did think of it before I Googled it.

The Yo Yo Proof:

With an ordinary yo-yo, pull out half the string. Place the yo-yo on a table so that the yo-yo is resting on its edge, like a wheel. The string should be coming off the yo-yo underneath, and trail out from it. Pull the string. The yo-yo will move in the direction of the pulled string, faster than you are pulling.

This is EXACTLY how a DWFTTW cart works. The table is the ground. The string is the air. The Yo-Yo is the cart mechanism that gears the wheels to the rotor. Instead of the cart rotor pulling on the air, the yo-yo spindle is the pulling the string.

It also proves the DWFTTW cart model on the tread mill:
Again pull out half the string. Place the yo-yo on a sheet of paper so that the yo-yo is resting on its edge, with the string coming off underneath and trailing out from it. Hold the end of the string down so it does not move. Slide the paper away from the string. The yo-yo will move in the direction of the string opposite to the paper movement.

You can do the same trick on an actual treadmill, just like the cart model. Hold the end of the yo-yo string and place the yo-yo on the moving belt. It darts up the treadmill, just like the DWFTTW cart model. Like the cart pulling on the still air, the yo-yo is pulling on the still string.

Proviso: The reason you can’t pull out all the string is that modern yo-yo’s have bearings at the spindle and will spin free unless there is some string wound up and binding it to the body.
Phil

Keep in mind that the mechanisum is between the two moving bodies and is attached to both. That's the trick. A sailboat going down wind is only attached to the air. It is sliding on the water.

All these good folks trying to understand this brain teaser.

When the real answer should have been obvious.

"The wheels turn the car’s propeller, and the prop thrust pushes the car, which turns the wheels"

Ah, huh. And where does the energy to drive the wheels come from?

Unless you're hiding batteries in the housing. Or using a flywheel to store energy. In which case, it's a hoax.

Just the fact you'd claim energy was COMING from the wheels stamps you as dumber than the Over-Unity guys.

If this hack works at all, it might be because the wind blows at slightly different speeds at different heights.

With a big prop, you could be catching more windspeed than an anemometer at ground level could detect.

@Jkirk3279: "Ah, huh. And where does the energy to drive the wheels come from?"

It does not work in till air. That is why it is not a perpetual motion machine. It only works because there are two bodies, air and ground, moving relative to each other. The mechanism attaches to both and mines the energy there.

...It does not work in still air...

>> Just the fact you'd claim energy was COMING from the wheels stamps you as dumber than the Over-Unity guys.

Thanks for your considered opinion JKirk. It seems it's always the deniers that are quick to insult others' intelligence.

I'd be more than happy to explain it all to you, but I can see that's not necessary.

>> ...It does not work in still air...

Ours works *best* in still air. In fact I got mine up to 15X windspeed once in still air : )

Iceman,

And will the fact that the GPS data shows the relative motion of each boat to the Earth effect the relationship between the relative velocities of the air, boat, and water, or the forces they create on the hull or sails?

The point is that on the treadmill, the model cart is effected by it's relative velocities to the surface beneath it and the air around it. Which is moving relative to the Earth and which isn't does not effect the forces involvoved. The cart on the treadmill in still air is the dynamic equivelent of a cart on a still surface in moving air.

Jkirk,

Would it be possible to build a cart powered by a conveyer belt, that travelled on a conveyer belt, faster than the conveyer built?

"Would it be possible to build a cart powered by a conveyer belt, that travelled on a conveyer belt, faster than the conveyer built?"

Please don't trouble jkirk with the facts or logic. He already has it sorted out to his satisfaction.

TAD wrote: "The vehicle in question has yet to be taught to use a GPS -- perhaps you could help us think of another way the vehicle could know."...

Now that sort of remark does you no good at all and just reinforces my suspicions that you are crackedpottery! I presume that there are some humans involved who do measure the speed of the vehicle? Pray tell what instruments are they using and what is the speed measured in reference to? For example, are they using a GPS and is the speed measured in respect to the ground?

The ice man

Jkirk wrote: "The wheels turn the car’s propeller, and the prop thrust pushes the car, which turns the wheels"..

Yes that is the "explanation" I have seen also. I suppose it does not disturb anyone that this is perpetual motion?

The ice man

We do measure the cart's speed with GPS. We measure it relative to the ground - just as we measure the wind's speed relative to the ground - because that's what people want to see. That's what they think of when we say the cart can go faster than the wind.

When we're doing our own experiments we sometimes measure the cart's speed relative to our treadmill belt, or the big cart relative to the dyno wheels it's sitting on. This is exactly the same. In fact it's simply another instance of the cart going DDWFTTW. It's just doing it in another valid inertial frame.

If the cart works on a treadmill - don't you think it would still work if we loaded that treadmill in the back of a semi and did the experiment while the enclosed semi cruised down the road at at a steady 10 mph?

>> I suppose it does not disturb anyone that this is perpetual motion?

It would certainly disturb me if it WERE perpetual motion. But since I know it's wind powered I sleep fine.

Doesn't it disturb you that your theory of what clearly has been demonstrated in the real world seems to require perpetual motion, while our theory only requires basic everyday principles of well accepted physics?

@eyytee

"search youtube for "eyytee", "coolaun", "axelerat3d" for intuitive animations"

Thanks for the pointers. Your videos nicely convey the concept of leverage / gearing relative velocities between moving objects. I do intuitively grasp that looking at the solid objects pictured.

I know the same principles apply to the propeller in the air, but unlike a solid lever, that linkage is harder to intuitively grasp. Intuitively air seems "flowy and squishy" and not effective as a solid fulcrum to lever off of.

Of course as any swamp fan boat shows air follows Newton's 3rd law just the same as any solid surface.

@scsci "I know the same principles apply to the propeller in the air, but unlike a solid lever, that linkage is harder to intuitively grasp."

It helps to imagine there is a sail on the lever, where it interacts with the air.

A sailboat can go faster than the wind, but not directly downwind. It can go at an angle, and with the wind glancing off the sail, actually moves faster than the wind itself.

The sailboat can even go upwind, if it "tacks," or zig-zags toward the wind.

There is a valley in New Mexico in which the wind blows faster than the wind elsewhere. Any time there is a windstorm, the newspapers like to report the wind speed there.

If the principle that makes that happen could be harnessed, a wind turbine could put out even more power than it normally does.

Oh, this one is sweet. Isn't it true that once relative vehicle speed has been established, that the propeller's blade has more surface area on the front that the rear, just like an airplane wing? It receives forward thrust on the same lift principle. The vortex behind the propeller is lending more energy. Ziplock?

If I'm right, do I get a PhD?

ziploc wrote:

"It would certainly disturb me if it WERE perpetual motion. But since I know it's wind powered I sleep fine.

Doesn't it disturb you that your theory of what clearly has been demonstrated in the real world seems to require perpetual motion, while our theory only requires basic everyday principles of well accepted physics?"

Contrary to what you claim, I rely totally on the fundamental principles of physics to show that the cart cannot possibly go directly down the wind faster than the wind. At wind speed, the wind does not exert any force on the cart. Do you wish to dispute this fact? At any speed, the ground opposes the motion of the cart with friction and the ground is not a source of energy. Do you wish to dispute this fact? Those two fundamental facts alone are enough to show that the cart at wind speed has no source of energy and it must overcome friction to continue moving at that speed. It must also be capable of doing work on the air in revolving the wheels and propeller. It cannot do any of these things with no energy source. This is clearly a joke and it will be exposed in due time.

The ice man

>>Contrary to what you claim, I rely totally on the fundamental principles of physics to show that the cart cannot possibly go directly down the wind faster than the wind.

And yet it does just that - with me in it.

>> At wind speed, the wind does not exert any force on the cart. Do you wish to dispute this fact?

Nope.

>> At any speed, the ground opposes the motion of the cart with friction and the ground is not a source of energy. Do you wish to dispute this fact?

Yes - I do. Energy is not an intrinsic property like mass. In the frame of the cart the ground whizzing by is very definitely a source of energy. As you say, the ground is still trying to slow the cart, but it's putting energy into the cart that's being used to turn the prop to create thrust.

>>Those two fundamental facts alone are enough to show that the cart at wind speed has no source of energy...

But the cart DOES accelerate right through wind speed to nearly three times wind speed. Do you wish to dispute THAT fact?

>> This is clearly a joke and it will be exposed in due time.

It is clearly a brain-teaser. And we've been trying our very best to expose it for the past few years.

ziploc wrote:

>>> Energy is not an intrinsic property like mass. In the frame of the cart the ground whizzing by is very definitely a source of energy. As you say, the ground is still trying to slow the cart, but it's putting energy into the cart that's being used to turn the prop to create thrust.<<<

Oh my, so that is what this is all about; switching the frame of reference once the cart is at the wind speed? If I understand you correctly, you want to place the cart in the frame that is moving with the wind, and in that frame the cart is stationary with respect to the wind and the ground is moving, right? Now you want us to believe that you can extract energy from that ground to make the cart go faster than the wind! Cute, very cute, but it is a load of nonsense! The reason why the cart is in that frame, if indeed it ever is, is because the wind was exerting a force on it and driving it against the friction with the ground and driving it towards the speed of the wind. Once it is at the speed of the wind, that wind force is gone, as you have already agreed. So the force which was allowing the cart to travel in the frame that is moving with the wind is also gone. The cart cannot stay in this frame and it cannot extract energy from the ground. That should be enough to bust your bubble, I think!

ziploc also wrote:

>>>But the cart DOES accelerate right through wind speed to nearly three times wind speed. Do you wish to dispute THAT fact?<<<

Yes indeed I do! What proof do you have? Where and when was it tested before witnesses and independetly verified to ge travelling directly dow with the wind faster than the wind steady state? Whet were the test protocols? How was the determination made? Who were the witnesses and what are their qualifications?

ziploc also wrote:

>>>It is clearly a brain-teaser. And we've been trying our very best to expose it for the past few years.<<<

It may well be a brain teaser for some, but it is not science!

The ice man

>> "The reason why the cart is in that frame, if indeed it ever is..."

Do you know what a "frame of reference" is? The cart is in EVERY frame of reference. We don't put it in one and move it to another. We can study the behavior of the cart from any frame we choose.

>> "Cute, very cute,"

There's nothing "cute" about this. It's not a scam. We're not asking for money. It's a brainteaser. It's physics. And we're trying to explain it to you while enduring a minimum of attacks on our intelligence and integrity. But I'm about to give up on that.

>>That should be enough to bust your bubble, I think!

You do understand that we have a 450 lb cart that stands 23' tall and goes directly downwind at nearly 3X windspeed - right? That supports my analysis pretty well. But it seems to torpedo your theory that it can't be done.

>>It may well be a brain teaser for some, but it is not science!

It seems that like "reference frames" you don't know what "science" is. We designed and then built and tested this vehicle based on an analysis that proved quite accurate. We've documented every step of the process, successes and failures, and made it all available for the world to see. We posted detailed build videos of our small scale working models so others could reproduce our results independently - and many have.

You claim "B.S." - sorry but that doesn't really count for anything.

Elsewhere spork explained it thus:

"The retarding force on the wheels (from driving the prop) multiplied by the speed of the cart over the ground gives us the amount of power available to drive the prop. The thrust being produced by the prop multiplied by the speed of the prop through the air tells us how much power we need. Because we have a tailwind, the speed of the prop through the air is less than the speed of the cart over the ground. That means we have more power available to us at the wheels than we need to drive the prop to get the needed thrust."

>> "Elsewhere spork explained it thus:..."

Hey, that's a really great explanation! *

* but of course I may be biased since elsewhere I'm spork : )

Cool! Thanks for all your hard work and contributions to this topic.

You're welcome. You got to see me completely change my mind on this. I take small solace in the fact that it only took me a few days to see the light. Glad to see most people are a lot more stubborn.

Ziploc, my new compatriot, why don’t you sell these things as toys? Not to make money, but just to get them into the hands of people. Even a build-it-yourself kit would work. Tell any skeptic to just buy one and try it out. Put it together and drop it on a treadmill, or in a windy parking lot.

PhilinYork, spork does have a series of build videos on YouTube under his user name "spork33". And don't feel sorry about not getting it at first, it took me a lot longer than it took you.

>> why don’t you sell these things as toys?

That's been suggested before. Interestingly, it just came up on another forum today. I'd be more than happy to make money on these gizmos, but I think the market would be extremely small. At one point I built something like 12 of them for the people that either did believe it and wanted one for themselves or didn't believe it and wanted to give it a try. I did have a few more people ask after the fact, but never got a flood of interest from the masses.

Once you put it on a treadmill and see it advance, you've kind of seen all its tricks. Maybe if you could sell it with a mini treadmill and let it continuously climb the treadmill as a sort of "Sharper Image" gizmo art kind of thing?

>> don't feel sorry about not getting it at first, it took me a lot longer than it took you

To be fair to you SZ, you were pretty quick to come around when you saw our first toy on the treadmill.

<<<"What proof do you have? Where and when was it tested before witnesses and independetly verified to ge travelling directly dow with the wind faster than the wind steady state? Whet were the test protocols? How was the determination made? Who were the witnesses and what are their qualifications?">>>

Ah, the iceman cometh. It's the "dow" of physics, you see. Sure reads like a done deal though, doesn't it? The cart DOES accelerate to nearly THREE TIMES WIND SPEED! I'm using caps (as 'ziploc' does above) to show this is proven fact. If Bob Dill of NALSA was somewhere in the vacinity while they made the Ivanpah runs, it means that NALSA verification is a mere formality, right?

Im surprised ziploc hasn't offered his standard, oft repeated 10-1 bet. It's a variant of 'Reference Frame Monte'. All the details of this game were revealed at several sites, like TalkRational. The current part there, #16, covers the 'Disaster in the desert.' http://talkrational.org/showthread.php?p=907789#post907789

Been busy of late and dropped out of the comic drama about a month back. Again I anticipate that there will be 'problems' with the NALSA test, and they will finally reveal the hilarity of ziploc's claims one way or another. Most likely it simply wont happen.

Oh humber, you still haven't learned after all I see. For anyone who does not know humber is a very reliable "negative predictor". If he predicts something, that opposite always comes true. He is a bit entertaining at first, but after a while he is just annoying. I thought he crawled away in shame after it was obvious to everyone else that spork and JB were more than successful. Once again, humber's resistance to learning shows that there are some people for whom there is no hope.

As mender once said... "assistance is futile". : )

scsci wrote: <<< Elsewhere spork explained it thus:
"The retarding force on the wheels (from driving the prop) multiplied by the speed of the cart over the ground gives us the amount of power available to drive the prop. The thrust being produced by the prop multiplied by the speed of the prop through the air tells us how much power we need. Because we have a tailwind, the speed of the prop through the air is less than the speed of the cart over the ground. That means we have more power available to us at the wheels than we need to drive the prop to get the needed thrust.">>>>

That almost makes sense, until you think about it a bit more. Basically what this is saying is that there is leverage between the wheels and the propeller. Even if that were true, the only variables that get leveraged are distance and force, but the product of these is work and the work is the same at both ends of a lever and so is power. Power is just work / time and unless this cart is also capable of time travel, the time is the same at both the wheels and the propeller. Right off the bat you can drop the claim for more power available at the propeller than is generated at the wheels because that is just not possible. There will always be losses between the source and the load and the power at the propeller will always be less than the power generated at the wheels. That is strike one.

As regards to leveraging the force at the propeller due to the propeller travelling a lesser distance through the air than the wheels travel over the ground, that is only possible if you have some stationary reference to act as a fulcrum for this supposed lever. The only thing available to act as a fulcrum is the cart itself! The cart is not a stationary reference at all as it is travelling along with the wheels the same linear distance. Indeed it is also travelling along with the propeller! That means the propeller and the wheels are travelling the same linear distance along the ground. Thus there is no leverage. That is strike two.

Finally, please remember basic Newtonian mechanics, in particular the Third Law of Motion and equal and opposite forces. Since we have now established that the Power and Work is the same at both ends of this supposed magic lever, we must also conclude that the force is also the same according to the Third Law. Strike three and you and this phoney cart are out of here!

The ice man

humber wrote:
<<<"Again I anticipate that there will be 'problems' with the NALSA test, and they will finally reveal the hilarity of ziploc's claims one way or another. Most likely it simply wont happen.">>>

If there is to be an upcoming NALSA test, they should have already agreed on the test methods and required test and measurement equipment. Everything must be independently verified and witnessed by qualified observers who are willing to answer questions about the test protocols. The procedure should already have been made public. I don't believe any of this nonsense.Nice to know there is at least one more sane person on this forum and I hope some more will join in!

The ice man

>> Right off the bat you can drop the claim for more power available at the propeller than is generated at the wheels

We're way ahead of you. We never made that claim to begin with. In fact it's only our detractors that EVER make that claim.

>> the propeller and the wheels are travelling the same linear distance along the ground. Thus there is no leverage. That is strike two.

Yes, they both travel the same distance over the ground, but what does that mean to a prop? The prop works on the air, the wheels on the ground.

>> Strike three and you and this phoney cart are out of here!

And yet here we and the cart remain. And it continues to do exactly what you seem to think can't be done.

>> Nice to know there is at least one more sane person on this forum

I guess like inertial frames of reference it's all relative.

But in all seriousness, the less you make comments like that, the less silly you're going to feel when you realize this is just a simple physics brainteaser. Honest.

Do explain to ice man the one about the reference frame of the guy in the space ship observing the cart, sporkster. He'll love it! Definitely one of my all time favorites.

Looks to me like Joby has finally put a muzzle on your more egregious insulting retorts zippy. Getting nervous as the date with NALSA nears, are they?

Never teach a pig to sing. It is a waste of time and it annoys the pig.

In this case, however, it is kind of fun. Seeing other people fooled by a brain teaser, I can see now why you stay so cool with the all the insults. They are laughable.

Yo, Ice man. Did you spend \$5 at Wal Mart and buy a yo-yo? Then imagine the string is connected to the wind? Try it.

I did. I really did.

>> I can see now why you stay so cool with the all the insults.

I wish that were true. Unfortunately I have responded in kind far too often to insults. And no - no one has "put a muzzle on me." But I am trying to learn to be smart enough to take your advice about teaching a pig to tell time.

Ice man,

Before you get too enamored with Humb or and his reasoning, get him to explain to you that Balloons travel slower than the air around them, streamlined shapes travel down rivers, powered only by the rivers flow, faster than non-streamlined ones, and that unpowered, heavier than air craft such as kites and gliders can remain airborne, without a string, in a uniform wind indefinitely.

Yes, he really does think that....

PhilnYork wrote: <<<"Yo, Ice man. Did you spend \$5 at Wal Mart and buy a yo-yo? Then imagine the string is connected to the wind? Try it.">>>

Since you have not explained what this has to do with wind force, I will explain what you should have observed while playing with your yo-yo. First of all, you should have observed as you pull on the string, the yo-yo will roll across a table faster than the string is being pulled backwards as evidenced by the motion of your hand. Do you know why? Mainly this is because of the difference in radius between the center spool and the outer body, an elementary example of gearing and leverage. You should have also noticed that you must maintain a constant force on the string to keep the yo-yo in motion in order to counter the frictional forces that are trying to stop that motion. As long as the velocity is constant (the yo-yo is not accelerating) the net force on the yo-yo is zero.
Therefore, in order for this to be relevant to the wind force on the cart, the wind must be providing a constant force on the cart as the cart accelerates. It should be obvious to you that this is quite impossible, as the force of the wind on the cart varies inversely to the velocity of the cart until at the speed of the wind there is no wind force at all. Thus, the yo-yo example is irrelevant to this discussion.
Now I suppose you will say that the end of the string is attached to a sail and as the sail approaches the speed of the wind, the yo-yo cart will be going even faster than the wind, right? The trouble with that is the drag from the yo-yo cart will not allow the sail to approach anywhere near to the speed of the wind. Therefore, even if the yo-yo cart moves faster than the sail, it will be short lived as the string is wound up! The system as a whole will move slower than the wind. However, I hope you and your yo-yo have many hours of enjoyment together. I also think “yo-yo cart” is a more appropriate name for this joke than “blackbird” don’t you?

The ice man

For anyone who's interested, it's now official just as of this morning that the NALSA record run attempts will occur at Smith Creek, Nev. from the 25th through the 27th of this month, weather permitting. Depending on weather and surface conditions it's possible that the effort will move south to the El Mirage lakebed as needed.

NALSA BOD member and technical guru Bob Dill will be the point man for NALSA during the tests along with other BOD member observers per requirements.

Anyone who wishes to come out is welcome.

I have not seen a final copy of the newly written NALSA rules (I think they may be awaiting official ratification from the NALSA BOD), but I am familiar with what they contain in principle. I'll make sure and publish a copy (on our project blog) once we get them from NALSA.

JB

PS: Sorry ice-man, the physics of this situation will dictate a NALSA observed, instrumented, documented and ratified record of more than 2x the speed of the wind DDW. Other than you looking silly, it won't matter that you can't follow how it works.

>>I hope you and your yo-yo have many hours of enjoyment together. I also think “yo-yo cart” is a more appropriate name for this joke than “blackbird” don’t you?

I think your plan is an excellent one - make fun of this just a few short days before it sets an official world record in front of highly qualified witnesses, under a set of stringent rules. I don't see any way for you to come out looking silly here.

Ah yes, the sarcastic spork. Cracks me up every time. From a literary standpoint I assure you his sardonic wit will be remembered long after whatever aero feats he achieves are forgotten. At his best he is nothing short of astoundingly funny. At his worst...I won't go there. To quote Al, there are limits to genius but not to stupidity, and we all have our moments of the latter; even the actual geniuses.

Iceman I like your style. Hope you keep the faith. If you can just hold onto it until the tests you will be among the chosen few. For I have followed this cyber-strand since it's conception back in 11/08 on Randi.net, and you would be amazed at the number of deniers that I've seen 'baptized' in the THREE THOUSAND PLUS pages of just this 'strand;' there are MANY others. It's very counter-intuitive for a variety of reasons, but I sure wouldn't bet against these guys, and in fact did the opposite way back.

This said, I'm also a big fan of humber's wit. I would love to see that I had been played wrt how I perceive the physics involved. I can't really follow the maths, and then there's the intriguing fact that Dan Kammen, a Noble winning physicist, has never recanted his original 'over-unity' assessment. So take a look at Blackbird's 16g chick going up the treadmill being an 'instance' of ddwfttw for starters. I'd like to read your views on this claim.

@"humber:" Hi humber. Hows tricks? I heard about you turning up here on TR, and at first a little saddened you wouldn't have let me know in an email. And while of course there's the possibility you're in route, there was something I picked up in one of your posts that made me wonder if you are really the same humber from JREF, RDF, and TR? Then there's the fact you are seldom so laconic.

Please send me just a quick-e to verify you are the same humber I have conversed with extensively online. And do come back to TR. Everybody misses you, especially spork and jb. How can you pass up being there when your adversaries are laughed off the lake bed? People will actually flood it with their tears, so great will the hilarity be when Rick's Rickety Rickshaw wabbles along at .53% of wind speed, right? I just can't imagine-unless you've had some epiphany-you wouldn't stick around for the crow banquet.

Keep in mind that humber's latest prediction is that we'd never go through with the official NALSA run. I sure wish he'd make stock market predictions.

ziploc wrote: <<< I think your plan is an excellent one - make fun of this just a few short days before it sets an official world record in front of highly qualified witnesses, under a set of stringent rules. I don't see any way for you to come out looking silly here.>>>

Despite the intended similarity between the acronym NALSA and NASA. NALSA is neither a scientific nor a government organization. It is a sports association of land sailors and has no standing whatsoever in the scientific community. Having finally caught up on my reading of the background of this ddwfttw claim, of the friends in high places and public relations bullshit going on behind the scenes for this stunt, I am convinced that these crackpots will indeed emerge with some certification that their cart has gone directly down the wind faster than the wind. In fact, I will go so far as to concede this certification to them right now!
However, a certification from a recreational sports organization that is given in the interest of public relations and the advancement of a sport that is not very popular to begin with, is a far cry from a certification from a scientific or professional engineering body.
In short, the certification from Bob Dill, member of the “good old boy network” done as he attends a B-B-Q at ziploc (spork’s) house changes nothing! The physics and the mathematics, the science, clearly indicate that this claim is nothing but nonsense and eventually this bullshit and hype will be shown for what it is and NALSA and Bob Dill especially will regret any unprofessional conducting of this matter. In particular, certifying this phoney cart, cheapens all the legitimate records that NALSA has already sanctioned, including GreenBird’s. That is something that will be regretted for years to come.

The ice man

That's the spirit ice man! Keep the faith. Never let the facts side-track your thinking and conviction. 'at-a-boy!

And speaking of 'facts' -- here's a few:

No member of the Blackbird crew has any significant history of landsailing (I've been on a cheap one one time).

No member of the Blackbird team had ever even *heard* of NALSA or Bob Dill before approaching them and asking them if they would be willing to instrument, observe and ratify our efforts last year.

No member of the Blackbird team has ever been to Bob's house nor has Bob ever been to of the team members houses (we live 3,000 miles apart).

This isn't a Bob Dill 'good 'ol boy's' effort -- all of the NALSA BOD members are involved and in fact it will require more than Bob's observation (NALSA rules) and ratification by the entire BOD.

We are not allowed to even buy the plane tickets for the attending NALSA crew for these runs to avoid the very thing that ice man is carelessly accusing NALSA of.

Ice man attempts to build NALSA up for it's history of excellent work and then drag them down for their acceptance of our offer to oversee our runs. He doesn't rationally get to have it both ways.

We are total and complete NALSA outsiders, while Richard Jekins (GreenBird) was a known associate of that organization for many years before they ratified his record. Due to this fact, our record will be far more 'pure' than the GreenBird record and not a soul that I have seen has questioned the NALSA ethics on that one.

JB

Iceman,

You've just accused a lot of people, including an entire sporting association, of being liers and cheats.

That's a pretty big call, and a hellishly cowardly one if you are not willing to back it up.

JB has extended an invitation for anyone to attend the reord attempt.

Why don't you do, and then explain why what you see with your own eyes isn't really happening?

BTW iceman,

You never responded to ziplocks rebuttle of your assertion that the cart cannot make use of leverage, in which he pointed out that it can because the air the prop works with is moving at a different speed than the ground that the wheels work with.

Now that you've accused people of fraud, care to explain why this is wrong?

As RossFW points out, we have always encouraged and welcomed all interested parties to any of our tests.

The only exception to this will be any upcoming tests at NASA Ames Research facilities -- we have to go through special training to be out on their runways per their rules and thus public can't just drop by.

Due to scheduling, our upcoming NALSA testing runs will not be at the Ames facility, but will be on one of three dry lakebeds and will of course be open to the public.

Stay in tune to the project blog for updates and drop on by. There is nothing we won't show or share with you.

JB

@ the ice man
Instead of developing paranoid conspiracy theories, you should learn some physics, and try to understand how it works. If you are interested in the opinion of scientists, rather than NALSA, then google:

"Drela Mark Dead Downwind Faster Than The Wind"
"Drela Mark MIT" for info about the author.

Or watch this lecture from the Technical University of Denmark on youtube:

watch?v=4ZjX_DIosM8

@the ice man
"As regards to leveraging the force at the propeller due to the propeller traveling a lesser distance through the air than the wheels travel over the ground, that is only possible if you have some stationary reference to act as a fulcrum for this supposed lever. The only thing available to act as a fulcrum is the cart itself! The cart is not a stationary reference at all as it is traveling along with the wheels the same linear distance. Indeed it is also traveling along with the propeller! That means the propeller and the wheels are traveling the same linear distance along the ground. Thus there is no leverage."

This is an argument I can't agree with.

Hopefully all can agree if instead of a propeller in air, the cart had a wheel on top pressing upward onto a overhead moving conveyor all the leverage arguments work perfectly. The cart need not be stationary versus anything in order to leverage one moving mass against another mass to accelerate itself faster than either.

@ice man "Therefore, in order for this to be relevant to the wind force on the cart, the wind must be providing a constant force on the cart as the cart accelerates. It should be obvious to you that this is quite impossible, as the force of the wind on the cart varies inversely TO THE VELOCITY OF THE CART until at the speed of the wind there is no wind force at all. Thus, the yo-yo example is irrelevant to this discussion." [emphasis added]

Dear Mr. Man,

This is your last chance, after this I leave you to these career trolls posing as aerodynamicists to carve your pathetic and inadequate skills up.

Your fundamental mistake is in CAPS above; the WIND VELOCITY RELATIVE TO THE CART is irrelevant to the reason the cart can go directly downwind *faster* than the wind; it is relevant only for the final speed.

1) ziploc et alia know that the wind force on the cart, if the cart is going downwind at the speed of the true wind, is zero, and they DO NOT CARE.

2) ziploc et alia know that the wind force on the cart, if the cart is going Directly DownWind Faster Than The (true) Wind (DDWFTTW), is upwind i.e pushing AGAINST the direction they want to go i.e. down-true-wind, and they DO NOT CARE about that either; it's just another loss to be miminized by design.

3) ziploc et alia know that the ground force on the wheels, required to drive the prop through the wind the prop sees (the D of L/D; force only matters here, not power) (if there is *any* hope for you, the light *should* be coming on now;-), is also pushing against them, and they DO NOT CARE about that either.

4) ALL (well, not all; mostly all?) ziploc et alia DO CARE about is the action of the prop pushing upwind on the true wind moving downwind. THAT is where you miss the boat because THAT is where the only energy available is delivered to the cart once it is moving downwind at (or above) the speed of the true wind; everything else is losses, absorbs that energy and only determines the top speed.

Your analysis is flawed because it treats the cart as if it were a balloon floating in the air in contact with no other medium, which it is not. If you can't see that, read it again until you do.

Just like any fixed-sail sailboat not sailing directly downwind, the DDWFTTW cart extracts the energy available between two media: the wind and the ground. Period, end of story, grok that or grok nothing. The rest is clever gearing, not sleight of hand, not hoaxstering, not violation of any laws of Newton or Thermodynamics, not anything else impossible. If the wind doesn't blow wrt the ground the cart CANNOT accelerate and if you push it it will slow down and stop. If the cart is put on a flatbed moving downwind at the speed of the true wind it CANNOT accelerate off the flatbed.

The yo-yo example is an almost exact analogy: the table under the yo-yo is analogous to the ground under the cart, and your fingers pulling the string are analogous to the wind on the prop. The energy to move the yo-yo is supplied by the differential between your fingers and the table top. I suppose if you greased your fingers, or better yet replaced pulling the string by hand with a drogue parachute on the string and a tailwind it may be more closely analogous; only with a prop the cart never runs out of string.

Like I said, this is your last chance, if you don't get it now I will only extract humour from you and lolz from the wit of ziploc et al. because at this point I see nothing useful in a technical sense you can offer on this topic. They know the device works, functional prototypes have existed for over two years, their explanation is on firm technical ground and its presentation is well honed so they don't need debate to improve it. As far as I can see they only toy with detractors for laughs at this point. That may be a pathology to be studied but it does not affect the cart's dynamics; or perhaps they do it because it is rewarding to see the few come around from what their initial intuition tells them.

Personally, I am envious of the wisdom of those that ask questions when their intuition contradicts what they see and never post any "it's impossible" statements.

Not sure about the yo-yo + drogue thing. If - and it's a big if - I am right and you put the yo-yo on the treadmill with the string+drogue extended toward the front of the treadmill then the yo-yo should move toward the front, and the drogue chute toward the back, at steady state.

It may take some fiddling with the diameter ratios and drogue chute size, the drogue chute efficiency may not be up to the task, and you may run out of string before you get to steady state.

I just noticed that "directly," as in DDW, didn't appear until the fourth paragraph in the story.

Note to Ms. Boyle: salient information goes in the first paragraph. Otherwise it's well written.

If an animal passes by your "wind-pwered" car, then we will know what will that animal become into.

@sirclicksalot, and Ice Man:

Here is how to make the Yo-Yo steady state. Hold a bit of string taut between your hands. It should loop once around the spindle of a yo-yo between your hands. The Yo-Yo is on edge and resting on the table. As you move the string back and forth, the yo-yo moves along the string faster than you move the string. If it moves slower, turn the yo-yo over.

Now imagine that the string goes on forever in both directions, and that the string is moving with a constant speed relative to the ground. The yo-yo will move down the string faster than the string, in steady state, forever.

I realized the truth when I imagined this:

When the cart is traveling at wind speed, the tail wind is not blowing against the rotor. The wind is blowing the cart AND the air exiting the rotor; the whole thing. And since the air from the rotor is coming AT the tail wind, it can still push against it.

Later I imagined the rotor engaging the air like a nut engaging a threaded rod. Without friction, a spinning rotor will move through air like a spinning nut moving along a thread. At steady state, the rotor moves at a different speed than the air, but at peace with it, with no energy moving from one to the other, and engaging it like the nut and thread. As a nut spins, it moves down a rod. If the rod is moving, the nut is moving faster -- in frictionless steady state -- yet fully engaged.

In frictionless steady state, moving directly downwind, the rotor is moving faster than the wind. If the wind blows just a little harder, it will push on the rotor, even though the rotor is moving down range faster than wind speed. The rotor is attached to the air and can be blown by it, even if it is moving faster than it.

>> The wind is blowing the cart AND the air exiting the rotor; the whole thing. And since the air from the rotor is coming AT the tail wind, it can still push against it

This is a very common misconception. But it is in fact a misconception. The prop is immersed in the air - it is not being pushed from behind by an air-pad like a pool-que.

Everything about the prop and the flow around, in front of, and behind it, is identical to any prop operating on an airplane in flight. And as with the plane in flight, there's no difference at all when the plane happens to be flying downwind.

Two days of NALSA testing complete. ~16-18 speed runs in ~12-13 distinct passes -- wind was lengthwise the lake on the first day giving us room run throught 2 sequential 'traps' on one pass.

Every run well over 2x. Most runs over 2.5x. Best runs near 3x or perhaps above. We won't know details of which runs qualify against NALSA rules until they go through the large amount of data and figure out which runs are best documented. There is a fairly comprehensive list of requirements to be met for a run to be NALSA valid and I'm certain that some runs will be disqualified if all the sensor info was not to their liking (wind switching direction too much during the run, etc).

There are reams of data for them to go through from more than 20 separate sensors (multiple gps, wind direction and wind speed sensors) on the vehicle itself, chase vehicle and lakebed, plus multiple video cameras. It will take some time for them to go through it all once they get home.

To say the least we are quite confident that a record over 2x will be ratified by the NALSA BOD.

On the project blog (www.FasterThanTheWind.org) Pictures, video and more information to follow as we recover from the long days and long drive home.

A special thanks to the NALSA officials who put in so much time, effort and money (they wouldn't let us pay for their travel expenses) to make this happen. Thanks also to the NALSA BOD who saw something interesting in this crazy little project.

We now know that NALSA has data sets showing peak speeds of over 3.5x and what we believe to be the best 10 second average of 3.48x.

This does not mean that NALSA will be ratifying a record for that particular run -- there are a host of requirements to be met (wind can't switch directions during run, etc.) before a run becomes NALSA valid.

We are becoming more and more confident that NALSA could ratify a record that is greater than 3x the speed of the wind.

@Humber:
****************
"These 'carteers' have been pushing this folly for 2 years now and soon NALSA will pop their bubble.

There is NO scientific evidence that supports their claims. NALSA will be their fist and last objective test, which is why I predict it will never happen."
****************

Humber wrong (as usual).

JB

WIRED posted an update on our project: http://www.wired.com/autopia/2010/07/downwind-faster-than-the-wind-possible-and-theyll-prove-it/#respond
It sounds like they plan to publish another article when last weekend's record runs become official.

Sigh. I don't know why this concept is so difficult to explain...the math is so easy, the concept is right out of actual, in-your-face reality with many not-so-difficult-to-understand examples, what else do we need?

It's really hard to watch.

For a given wind speed, the maximum speed (VMG) along a downwind course is equal to

VMG=(L/D)*sin(alpha)*cos(alpha)+cos^2(alpha)

It's easily derived with a few quick vector sketches.

where L/D is the ratio of lift to drag. The drag portion includes rolling friction, transmission losses, parasitic drag from frontal area, propeller efficiency, etc. The lift would be the simple thrust of the propeller at the design point.

Alpha is the mean angle of transit for any point on the propeller blade relative to the downwind course.

The results of the above equation *exactly* replicate sailboat race trim charts. To use the race charts, one determines the closest angle to the wind a particular sailboat can sail at. Not surprisingly, this angle is determined by the maximum lift/drag characteristics of the boat (L/D). This angle (or ratio), and this angle alone, determines the maximum speed the boat can achieve on a beam reach, or perpendicular to wind: L/D times the wind speed. It also is the sole determinant of the speed it can reach on any other point of sail. Solving for d(VMG)/d(alpha)=0 will show that the maximum VMG depends on a minimum L/D of somewhere between .5 and .6. It's simple math, and the fact is that most sailboats cannot achieve this minimum efficiency. Pretty much any ice boat can, and so can the Blackbird. Plotting VMG versus alpha on a polar chart will trace a beautiful lobed curve with VMG(max) at around 47 degrees for an efficient iceboat or 1.0 for a average small efficient sailboat at far smaller angles. Most recreational displacement hulls won't make a VMG anywhere near 1.0.

Working backwards (recursively in practice, beginning with an assumed L/D of 6 to determine alpha, then using the alpha to compute L/D, etc until no change is seen from the iteration), one can calculate the efficiency (L/D) of the Blackbird: around 4.8 to 1. Not bad. A typical light general aviation propeller would have a L/D of around 2.7:1, given the drag from the high speeds it is spun at. The airfoil sections of the blade themselves have L/D ratios of around 15:1 (taken from a random Sensenich data sheet). Overall, the airplane might see 8:1 or 10:1. A sailplane can see ratios in excess of 45:1 or even 50:1 in competition class ships. Perhaps the connections seem scattered, but it becomes obvious that real improvements are possible for the Blackbird given that overall design is heavily dominated by vehicle/transmission drag rather than by the potential L/D of the propeller.

@Humber:
>>There is NO scientific evidence that supports their claims. NALSA will be their first and last objective test, which is why I predict it will never happen.
************

ROFLAO!!! -- Humber wrong (as usual).

Just a bit ago I received a copy of the comprehensive three page report from the El Mirage attending NALSA Observers to the full NALSA BOD. This report contains all relevent details and data of the test and recommends that the NALSA BOD ratify a record of 2.8x the speed of the wind.

Considering the particularly careful way that this feat was documented (way above NALSA requirements) and considering that we have data showing even faster runs but WE chose to submit this lower one for it's exceptional defensibility, there is no reason to believe that the BOD will not ratify and every reason to believe that they will. Remember, a good percentage of their BOD members have already seen the Blackbird in action at over 2x at the Ivanpah test.

(No, I won't release any NALSA document I've been CC'd on. The Observers Report will be public once the BOD ratifies the record and will appear on the NALSA website. Folks can get it from them, not from me -- that way they'll know it's real)

It would surprise me if this isn't wrapped up within a week, but that's just my own opinion based on how NALSA has been moving on it so far.

Seems I've been wrong about a lot of things JB. I spent a few days this week with an old friend who is one of the most competent physicist I've ever known. I told him about the BUFC and after a discussion that lasted all afternoon and into the night he was able to show me all the mistakes in my reasoning.

When I get the time I plan to write it all out, along with sincere apologies to you, spork, and all the carteers at Talk Rational. I just wanted to let you know before the NALSA results were in that I finally 'got it' and fully expect they will certify that there is no doubt you have proven your claims and then some. I now finally realize you did so long ago on the treadmill. Sorry doesn't really cut it I know, but it's the best I can do for now.

Sorry, but I simply don't believe this is the same humber we've debated for so long. If it is, you should tell us so on the TR forum. No need to post an apology there - just confirm we're talking about the same person.

@humber
"Sorry doesn't really cut it I know,"

Quite right. Your punishment will be explaining it to Harold... until he gets it.

Perhaps a simple explanation might satisfy everyone. The problem with a simple sail perpendicular to the wind (not a wing design) is that once the cart and sail are moving at the wind speed (i.e. zero relative velocity) there is no longer any force exerted. This cart gets around that problem by turning the propeller to push against the moving wind. I think of this more in terms of a level shift to the sails (props) relative velocity to the wind such that the wind can exert force on it. The level shift needs to increase at high cart velocity. Conveniently the wheels and therefore the propeller turn in proportion to cart velocity.

@robertroorda:
>>Perhaps a simple explanation might satisfy everyone.

No.

Thanks TAD. Everyone in agreement is hopelessly unrealistic. I mainly hoped to decouple the relative wind velocity discussions from energy source concerns to short circuit various perpetual motion rants. To be fair, I'm not totally certain that I have it straight in my head either given my limited aerodynamics knowledge. Is my grossly simplified explanation reasonable in your view?

@robertroorda
I was just being a smartass at your optimism. :-)

Your explanation is not unreasonable considering it's brevity. It really is a tough gig to explain it in short.

JB

I've been trying to wrap my mind around this, and have come up with the following thought experiment for the skeptics.

Build (in your mind) a free wheeling propeller powered air cart powered by an electric motor, capable of moving overland on a perfectly still day at 20 mph.

Now give the same cart a 10 mph tail wind, but with the same power applied to the prop.. Does it move faster now? Of course it does. We are now extracting the extra energy from the wind, while going faster than the wind, downwind.

The proof in this case would be the second cart is moving faster than the first. This would be a very easy case to actually model if you're that stubborn.

For some reason, it is much easier for me to see the wind energy extraction with the vehicle "uncoupled" like this.

So if the energy is still there to be harvested, moving faster than the wind then the rest is just in the clever engineering and machining details.

I've sorted through lots of old threads and arguments on this, and if I do say so myself, this is the only "simple" thought model that works for me. No voodo No witchcraft.

I have a doctorate, and it's not in engineering or physics, but I think that a lot of folks get so bogged down in the force/vector analysis, that they don't first answer the basic question. "Is the energy extraction theoretically possible." With my example, I don't think it's that hard to see.

We have to be careful not to be constrained by our educations, rather than enabled by them.

John

Hi John. Just wanted to let you know I was the one who has posted as humber on PopSci. This same message will appear there like a second later if you check the times. Of course you could maintain we coordinated this, but that would make most rationale people question your paranoia level, doncha think? :)

Let me put my 2 cents in the pot. First I would like to start by offering my congratulations and thanks to Rick Cavallaro and John Borton for their great accomplishment. Thanks for the many hours I have spent thinking and analyzing what the Blackbird did and what it might mean. I can not remember when I have been so enthralled and obsessed about something. I first heard about the Blackbird when I read the article in Wired magazine. As a windsurfer I knew that you could not go straight down wind faster than the wind on a sailboard. I taught windsurfing at one time and was aware that when the wind speed doubled, the pull on the sail quadrupled. I had always felt, that in going faster than the wind I was some how getting more out than was being put in, even after knowing the theory behind it. I guess that was part of my being so intrigued by what the Blackbird did. If I would have read Rick's explanation before hand, I would have been on his side. Another way I thought about it after it had been accomplished, helped me personally come to terms with it. It is just a little bit different way of thinking about it. The sails (props) of the Blackbird at no point in time sailed straight down wind , they were always sailing across the wind. The moment the Blackbird started to move, its sails (props) began sailing across the wind. This means that the sails never sailed straight down wind faster than the wind, always across. Every thing together went faster than the wind straight down wind. Can you imagine how fast the prop had to sail across the wind to do that? To get going 3 times the speed of the wind down wind (not straight down wind) on a sailboard I would probably need to be going at least 6 times the wind speed at a 45 degree angle off wind. Can this be done on ice? If not, then there is definitely more going on with the Blackbird than meets my eye.
When the Blackbird began to move, it was be pushed by a tail wind. Both the wheels and prop begin to move as they are tied together. At some point the prop turns fast enough to provide propulsion. At the same time the tail wind is decreasing. Movement is depending more and more on prop propulsion and less on the tail wind. The fact that the tail wind reduces the head wind that would be there without it, is reducing drag.
I think maybe the reason this could be possible is, like I said before, that lift is not directly proportional to wind speed. It is exponential. It seems to me that the energy required to produce the wind is less than the energy provided by the lift. Until now no one knew how to take advantage of this.
Think of it like this, using a spark to extract energy from gasoline. The energy it takes to create a spark is much less than the energy released by the gasoline. The reason being is that the energy is already in the gasoline. You are just using a spark to extract it. The wind might be like the spark. The wind is what is being used to extract energy from the atmospheric pressure in an amount greater than the energy needed to create the wind. Just a thought.
To find out if the Blackbird could self propel, could be done by pulling or pushing it to say 20 mph on a windless day and letting go. If it is capable of self propulsion it will do so. What do you have to lose, Rick? Remember, few thought that the Blackbird could go down wind as fast as it does. I do not think that before hand, you even thought it would go as fast as it did. Maybe more is going on here than meets the eye.
If it can self propel, I have already thought of how a windless windmill (atmospheric pressure engine) could be made. :-)

I like to always realize that things are going on at the sub atomic level, that no one knows anything about. Most of the time this has no visible affect at our level, that we know of. But every once in a while it is seen at our level. Like the Gecko lizard walking on the ceiling. Scientist believe that a sub atomic force is coming into play that enables this. The van der Waals force. This is not to say that I think that something is going on with the Blackbird at the sub atomic level, I am only trying to make people realize how much there is that man does not know. Even at the Newtonian level man does not fully understand the forces of a vortex or cavitation. We should always keep an open mind and not be too quick in dismissing something as being impossible.
At 70 I am still a dreamer and maybe losing it.

Upon further thought I realized that I would only need to sail 4.2 times the speed of the wind to achieve the equivalent of what the Blackbird did. That is probably achievable on ice, even though the Greenbird did not do it on land. It is still pretty amazing what the Blackbird accomplished. Nothing to lose, other than feeling stupid for trying, in trying to see if the Blackbird could self propel. It does not seem possible to me, but then again I would not have thought that the Blackbird could have gone 3 times the speed of the wind straight down wind. I say 3 times, rather than 2.8, as I believe Rick when he says it did it in some of the runs.

Here is my take on going directly into the wind faster than the wind. Using Rick Cavallaro's explanation for being able to do it down wind, I would have to ask, is it possible to tack upwind faster than the wind? To reach a point up wind faster than the wind on a sailboard, I would need to sail up wind at a 45 degree angle at over 1.41 times the speed of the wind in order to duplicate going directly into the wind faster than the wind. Let me explain this a little more. When you are sailing up wind across the wind there is an up wind element. This up wind element has a speed that would need to be faster than the wind in order to tack up wind faster than the wind. Not sure, but would say right off hand that it can not be done.
Another thing to realize in going upwind faster than the wind, is that if it is possible, then this vehicle would be capable of self propulsion. It could go, until it wore out., without any wind upon reaching a given speed. That is not to say it is impossible, but things would have to be going on that we don't know about. Like maybe a vortex for example. I was talking to my son about it, and he told me that I should read about Schauberger's findings on the subject of vortexes. Schauberger had noticed that a trout could stay stationary in a swift stream using very little movement. Schauberger thought it had to do with a natural vortex caused by the shape of the trout. How ever the trout does it, it seems to be reducing the equivalent of a head wind. How that could be used in sailing up wind I do not know. It does seem to open a possibility. Remember too, that lift (vacuum in the atmospheric pressure) is exponential to wind speed.
Anyway, I am not going to be too quick to say it is impossible to go directly into the wind faster than the wind. If it can be done, the ramifications are mind boggling.

Actually, the numbers suggest that going directly upwind faster than the wind should be quite do-able - and using only the mundane laws of physics that we already know and love.

We're well aware that it would seem to imply the vehicle could operate in no wind, but it's really not the case. It is a wind powered vehicle. It requires true wind relative to the surface on which it operates. It can't keep itself going using only the relative wind that results from it's own motion.

Here's how it works.

Or here's how a wind-powered car can travel directly downwind at greater than wind speed:

First, the only way to extract (kinetic) energy from the wind is to slow it down. Kinetic energy is proportional to (1/2) x wind mass x velocity-squared. Once the wind is slowed down to zero speed (zero velocity), there is no more energy that can be extracted. (The wind-powered vehicle slows the wind but not all the way down to zero speed.)

In order for the vehicle to go faster than the wind speed, the wind from behind has to push on something that is moving slower than the wind speed. What it pushes on is the air discharged rearward by the propeller. Or more accurately, the air discharged by the propeller, and the wind from the rear, push on each other. This slows down the wind from the rear and applies force in the forward direction to the propeller blades. The force is sufficient to overcome the drag that the rest of the vehicle develops when traveling at faster than wind speed. The energy extracted from the wind is transferred to the vehicle's forward motion.

Some of the energy transferred into the vehicle is coupled by the wheels and transmission to drive the propeller, which forces the air rearward against which the wind pushes. The remainder of the energy goes into accelerating the vehicle, overcoming drag, and frictional losses.

The propeller discharges air rearward at a speed (relative to the vehicle) greater than the vehicle's speed less the wind speed, perhaps much greater than that minimum speed.

That's the explanation.

You may substitute the word "power" for "energy" everywhere if you change "wind mass" to "mass flow rate". And the power extracted from the wind goes as the cube, not square, of the wind speed, because the mass flow rate increases linearly with wind speed.

Interesting. If I understand this correctly, you could turn it around and it will go upwind too, though the airfoils will be in the wrong direction.

Also, you could get better acceleration with an adjustable pitch prop by using the wind to start accelerating, then switch to driving the cart with the prop once you have enough speed.

Also, if you could adjust the rotation of the mast, you could actually drive it around using the wind, no matter what direction it came from! Very exciting. I might have to build one.

How much optimisation did you have to do the get it to work? IE how efficient does the drivetrain and aerodynamics have to be to travel at a reasonable speed. The real question being, can I hack one out of junk and have a reasonable expectation that it will work?

Also, I bet PhilinNY is a climate change denier...

Actually, come to think of it, what I want to know is if an electric generator/motor driver would be efficient enough, since a drivetrain incorporating a rotating mast, with a variable pitch prop, and infinitely variable/reversible wheel drive would be pretty complicated.

And actually the NuVinci bicycle hub might be useful for that. Hmmmm... gears turning. Literally and figuratively.

Just read some of your blog, and I see you have built a VP prop. Do you have enough adjustment to start as a turbine, and switch to prop?

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