It would be opposing wind pushing against wind, which would allow it to go faster than the pushing wind. In other words there is excessive trust in relation to, ratio to, the devices total weight/drag and it accelerates because of that excess.
If this is based on honest people sharing what they built, the answer is mechanical advantage. If, a gear attached to the rotor is made in a ratio to rotate 3 times to the 1 time rotation of the driving gear attached to the wheels that is only mechanical advantage. Explaining why it would start on a tail wind, if the device was light enough, even against the tail wind, once the propeller began to produce thrust, it would be opposing wind pushing against wind.
You could use the principle on a bicycle, but it would be impractical for a lot of reasons (not the least of which is the safety issue). Also, the torque of the prop would be trying to push you over all the time. And without pivoting the whole prop mount, it would only work directly upwind or downwind.
@pwpike As an engineer I feel totally myself to build a cart that would runs using windpower.
As a realist I know that I'll never find a 1 km of a straight isolated road, a wind source that blows constantly along the path on that road, of course I will not find 10 anemometers in my closet to put along the road. I won't be able to test the speed of the cart so that it doesn't hurt the results.
There are lots of thing that defines the real experiment from the amateur propellers on the wheels.
@tezropunkel Depends on what you're trying to prove. I don't need to know exact numbers to see if the cart's moving 3x faster than windspeed, just like I don't need instruments to tell a car is moving faster than a bike when it's moving 3x faster. I only need those numbers if I'm trying to make a physics formula or something. I think it's pretty clear that these guys (as well as others) have demonstrated DWFTTW, and you don't need to know exactly how fast the wind or the cart was to see that.
@pwpike Am i getting it right that you say that you can clearly see how fast the wind goes and compare it to the speed of the cart? I mean, I can't. Neither can anybody by the way unless he has an anemometers built inside a head or something. You know it sounds like "Look there are invisible fish in the aquarium" and believe that...
@tezropunkel As I said, you can build your own cart and prove this wrong if you wish. The physics seems fine to me; the evidence seems clear enough; it's been validated by an independent 3rd party; you have the ability to debunk the theory. Seems like pretty sound science to me.
I guess this shouldn't be too surprising, given that no one has a theory called the conservation of speed. Now, if someone managed to show that the DDWFTTW don't obey the conservation of energy, now that would be something!
This is quite an amazing device, and so simple at the same itme. I plan to build my own small model.
Are there any specific ratios regarding gearing between the propeller shaft and the axle, with wheel diameter in mind?
A little question on the side ( call me crazy; I'm no physicist ) but what will happen if you reverse the propeller direction? Would it be possible to make it go upwind at equal speed to the wind, or perhaps slightly more?
We established a world record with "Blackbird" by going directly downwind at 2.8X wind speed. This winter we'll be replacing the propeller with a turbine (which will look just about the same) so we can go directly upwind faster than the wind.
So, in theory, if one pushed / towed this vehicle up to a certain speed on a calm day and then let it go free, would it accelerate up to some speed and then continue to travel at that speed until it ran out of road?
The air in the room is still - relative to the room. Rather than move air over the surface (wind), we move the surface beneath the air (same relative motion - still "wind").
Sure, I can see that the cart is going uphill on the treadmill....but this does still not verify their claim that the cart can move faster than the tail wind. To do that they need further instrumentation... Specifically, they should have setup a meter to show what the speed of the wind is and also shown us the speed of the treadmill. Without that how do we know it is truly going faster than the tailwind???
The air in the room is still. This is demonstrated in some of our other videos. Only the belt is moving. If the vehicle maintains its position on the treadmill it is going downwind at exactly wind speed. Just as you would feel no wind if you rode your bike downwind at wind speed, the cart experiences no wind at this point. If it advances on the treadmill, it begins to experience a relative headwind, as you would if you rode your bike DDWFTTW.
Makes sense to me, the wind that's pushing the kart is the actual breeze plus what's generated from the propeller. All of that total only has to be enough to keep the kart from losing momentum. If you placed the thing on the treadmill with everything constant but the propeller not generating thrust, it would slowly drift backwards, not fly backwards instantly. Like a plane taking off on a treadmill, the treadmill isn't pushing the plane, just spinning it's wheels.
It would be hard to do, but it would be cool if you could measure the drag force the cart exerts on the treadmill. I'm guessing that's where the primary energy input to the system is. either version, treadwill or wind powered, is getting its energy from slowing down the relative motion of the air and the ground.
I have to admit, I probably wouldn't have given this much thought without seeing your demonstration. good job!
@momerathesoutgrabe You're correct - on both points. The energy does come from slowing down the two media relative to one another - and we found it difficult to instrument the retarding force on the axles due to the vibration.
Forgetting the tread mill and putting the vehicle on the ground with a 10mph tail wind the vehicle moves forward by the wind on surfaces of the vehicle and the force generated by the spinning propeller. When the vehicle reaches 10mph it has zero tail wind force but has gained kinetic energy which transfers back to the propeller moving the vehicle forward. However, the kinetic energy is lost with friction and the vehicle will slowly return to a speed below that of the wind, cycle starts over.
Sorry Capn - but it has nothing to do with capturing the kinetic energy of the vehicle, and it doesn't settle back to less than wind speed. The manned vehicle we built will do better than 2.5X windspeed continuously.
I can explain it but you may prefer not to know. Look away now.
A brick does no work sitting on a table. A little vehicle does no work standing still. Think of energy and forces but separately. Work done is different from force.The vehicles start stationary and use drag on the vehicle body to move it forward which spins the propeller which now has its own rotating velocity with lift separate from the vehicle.The vehicle speed matching wind speed is nothing special to the propeller. Its levers!
Seems to me that the prop is angled in such a way that the cart is "pinched" between the wind and the treadmill just as a boat on a tack is "pinched" between the wind and the water via the keel.
There's really no need for them to do it now - since we've done it with a 23' tall, 450 lb, manned vehicle that will be setting a new world record in the next few weeks.
It is wonderful when skeptics get pwned by the sheer reality of a working physical prototype. Skepticism which is shallow and falsely intellectual is what these "naysayers" are all about. It is their way to convince open, yet weak, minds of their logically-fallacious debunkery. I can see through the axe-grinding of these shallow naysayers and distinguish them easily from the honorable class of meek skeptics who, in a seemingly miraculous manner, manage not to make asses of themselves.
@superifico Seems to me that the prop is angled in such a way that the cart is "pinched" between the wind and the treadmill just as a boat on a tack is "pinched" between the wind and the water via the keel.
The drag force of the tailwind pushes on the vehicle like a parachute. The corresponding power decreases by a cubic function approaching zero at TAS=0mph. On the other hand, the torque delivered to the fan by that same tailwind attempts to turn the wheels backwards. However, because such backwards torque is due to pressure change from the rear of the prop to its front, which itself is a function of prop speed, the vehicle moves forward....
When the craft moves faster than the wind, TAS>0. The drag force of the "headwind" pushes on the vehicle, but now its torque on the prop helps sustain forward movement of the wheels. The power of this increases, at best, by the cube of TAS. However, friction and drag forces that are linear with lower speeds become quadratic at higher speeds, and corresponding power losses are quadratic and cubic respectively. This has a compounding effect on the power transfer to the vehicle, limiting velocity.
"If the cart goes forward on the belt, it's going faster than that 10 mph tailwind."
It's more complicated than that. To travel faster than a 10 mph tailwind, its true air speed must be *POSITIVE*. The wheels must spin faster than the speed of the treadmill + 10mph. Compared to the situation with no treadmill, with the treadmill, the prop will generate a higher thrust corresponding to this higher wheel speed. Whether a given prototype will work depends on *POWER* balance.
Nice point to make. Would you mind quoting the now deleted typo ridden post you were actually criticizing?
BTW, I'm not against DWFTTW at all. I actually hate it when people such as yourself, who tell it like it is, are called quacks or advocates of perpetual motion. That's why I'm here. AFAIK, those "ardent DWFTTW deniers" or "pseudo-anti-pseudoscience people" or "science pseudo-experts" should be called out for their statements of "complete nonsense", not me.
Why the hell do emotions even enter into it. If you need a belief system, there's a church right down the road. This is science you idiots. Science is and always will be the study of how wrong we are.
"Why the hell do emotions even enter into it. If you need a belief system, there's a church right down the road. This is science you idiots. Science is and always will be the study of how wrong we are."
The truth is that emotions have entered the "debate". The video above gives the impression that people saying this is an obvious hoax perpetrated by quacks are emotional themselves. It is funny, because those who try to defend science with emotion are the least credible.
"Science is and always will be the study of how wrong we are."
Science is not the study of how wrong we are. Science shows how wrong we are. Science is the study of things and their phenomena, which we believe we know well about, yet actually don't, in a way (via the scientific method) that will allow us to know the err of our thoughts.
I'm curious as to how the wheels are connected to the fan. I understand that turning the fan turns the wheels, but does turning the wheels turn the fan?
Suppose the wheels drive the fan:
With little friction in the wheels, and the treadmill going very fast, you would expect the vehicle to roll with gravity, but with the wheels spinning very fast in the other direction (driven by the treadmill). In this case, the wheels spinning cause the propeller to turn, pushing it up... No?
"I'm curious as to how the wheels are connected to the fan. I understand that turning the fan turns the wheels, but does turning the wheels turn the fan?"
Yes.
In one video, the wind from the rear forces the blades CCW. However, rolling the cart and wheels forward forces the blades CW. If the air flow from rear to front creates CCW rotation, CW rotation produces air flow from front to the rear. Source of the energy of F2R thrust is the drag of the wind pushing the cart.
"With little friction in the wheels, and the treadmill going very fast, you would expect the vehicle to roll with gravity, but with the wheels spinning very fast in the other direction (driven by the treadmill). In this case, the wheels spinning cause the propeller to turn, pushing it up... No?"
The problem with DWFTTW is that good, informative articles and videos on this subject are hard to come by, and reasonable analyses seem to get lost in the shouting. I myself thought initially that this couldn't work, then worked it out on my own, only to be insulted by the rabid DWFTTW supporters who obviously don't have a clue how it works but feel entitled to belittle reasonable skepticism. If you can't explain it to the lay-person, it's not science, just engineering.
Sure, but you claimed that what cannot be explained to a layman cannot be science. But that is not the definition of science. Science is science whether understood by laymen or not. If no layman can understand a certain specialist part of science, that is not science's fault. That's the scientists' fault.
I've been sort of following your saga to try to make skeptical sciencey people understand. You might try pointing them at this video: Cz4sf-pZ8jk , which is not the same thing, but shows the same principle. Replace the geared bar (rack) with "wind" and the gear (pinion) with "perfectly efficient propeller" and it's clear it's theoretically possible, and then your video shows it's possible in practice as well.
"I know they did one where they flew an airplane rolling on a treadmill."
It is strange how (or even why) they prove it. Many assume that the treadmill is supposed to go the same speed as the plane's wheels, but the only force required to do that is for the prop to generate enough thrust to overcome friction at the wheels, etc. If you get the prop to produce any more thrust, it will go forward like any other plane, and the only difference is the wheels will spin faster.
"I know they did one where they flew an airplane rolling on a treadmill." (Continued...)
A lot of people imagine that the plane on treadmill scenario implies that the plane's wheels are moving as fast the treadmill, and the reason is that exercise treadmills, the kind people usually regard as treadmills, have an front and end not very far apart from each other. If the trust is not astronomical, the plane will be far below stall speed, and it will not fly.
@Nomoreidsleft Nope. We tried everything to get them to do it. We gave up and decided to do it ourselves. If you look at traderturok's youtube videos you can see a segment the Discovery show did on our cart a few days ago in Canada.
Wind speed relative to cart speed is irrelevant. It's like saying airplanes will never fly because they are heavier than air. It's converting he angular momentum of the propellers to linear momentum of the cart. So as long as the wind is strong enough to move the propeller they go forward.
"It's hilarious that so many people can watch this and still not get it."
No it is sad. It is direct proof that some people can make systematically wrong conclusions due to their "education". Why does it take a few weeks or so for a cynic to change his mind about something like this? They have to be missing something important in their reasoning.
When you jog on ground, you can feel the relative wind. When you jog on a treadmill, you don't feel the win.
I think the point of this demonstration is that the torque provided by the wheel should cancel by the counter torque made by the wind on the propeller, thus the cart move at most at constant speed. Apparently , so is not the case..
@vietarc When you jog at 10 mph in a 10 mph tailwind you don't feel any wind. That is exactly the scenario we're demonstrating on the treadmill. If the cart goes forward on the belt, it's going faster than that 10 mph tailwind.
The treadmill is an invalid surrogateg... ignore it for the red herring that it is.
If you have a cart on level ground with a 10mph tailwind, the cart can start and accelerate nicely... there's no controversy there. BUT, as the speed of the cart nears the speed of the wind behind it, the windspeed over the propeller will drop to zero as will any force generation.
Without force generation there is no energy to move the vehicle. Bottom line... physically impossible.
And yet we have a 300 lb cart that stands 22' tall that will carry a driver directly downwind faster than the wind. We will be testing it on the dry lake bed next week for the first time.
If you think the treadmill is not valid, you simply don't understand that all motion is relative.
@kuhndj67 This note is to update spork's reply. Yes they ran their man sized version at the dry lake bed, and it performed far past expectations. They were hoping for twice wind speed and it looks like they were at three times wind speed. Congrats boys, you did great!
You're storing energy. When the vehicle is held stationary on the mill the excess kinetic energy is stored by the propeller. The energy is dissipated as the vehicle moves forward. When you stop it with the spork the energy is replenished. You are not letting it move far enough to dissipate the energy.
When it's maintaining position on the treadmill it is expending exactly as much energy as it's using. The only time energy is being stored is the time during which the prop is being accelerated. The only time that energy gets used is when the prop is slowing down.
One of your main arguments is the reference to ice-boats. I have searched and can find no hard data (gps speed, wind speed, wind angle, vmg angle) to confirm that ice-boats can achieve a downwind component greater than true wind. Sure, they can go 3 or more times windspeed at 90degrees, but show us data on what they do at 135degrees. I'm a windsurfer of 15 years and know it can't be done. Windsurfers hold the speed record and it is less than true wind at 135degrees.
I've been a windsurfer for over 20 years and I can assure you it CAN be done. I can't post a URL here but if you search on "cetus iceboat" and click on the first link you'll see the data you want.
WindSphinx, I would encourage you to attend either an iceboat regatta or a dirtboat regatta so you can witness first hand what you say cannot be done. I assure you that it can be done. I do it everytime I sail. We can do it so easily, that no data is necessary. You can see it with your own eyes.
@789995 They did take their man sized cart to Ivanpah and ran it at close to three times the speed of the wind directly downwind. They were very well received by NALSA.
@Dexistomors The wheels provide the power that turns the propeller which pushes the cart. It sounds like perpetual energy, but it isn't . The power for it comes from the air. The cart runs off of the difference between air speed and ground speed. After the cart passes it leaves behind a path of air that has been slowed down relative to the ground. If there is no wind there is no power available for the cart to run on. It is a feedback system very much like a tacking boat experiences.
One thing you'll notice about machines like this and other things like the windmill driven boat direct against the wind are that they serve to decrease the relative velocities of air to the other medium they happen to be travelling in.
It is not free energy. It is extracting from the pool of energy that is two different media with differing relative velocities.(the air and ground in this case) or air and water in other cases.
Note the equation Energy = Force X distance. The force created by the fan can be greater without violating the conservation of energy law than the force exerted on the wheels, as the distance the wheels travel relative to the road is greater than the distance travelled by the fan relative to the air.
I want to buy one. How much will you sell one (that works well outside) for? You should sell them as toys... I think you'd make a fortune if you could make them pretty cheap. Looks cool.
Look at my other videos. I posted a series of three bideos that takes you through the build process in detail. I also give all the part numbers etc., as well as where to get them.
I imagine the rotation of the propellor as being like a helicopter's rotor on its side, then can consider the familiar forces of 'drag' and 'lift'. Lift propels the cart forwards whereas drag opposes the rotation of the prop, and hence acts to slow the cart down. However, the connection between the wheels and the prop is such that a small change in prop speed causes a relatively large change in cart speed. Hence, by some 'lever law', the lift 'wins' and the cart is propelled forwards til AOA=0.
There is power that can be extracted from the difference in speed between the ground and the wind. The power entering the vehicle is the velocity of the ground multiplied by the force from the propeller. The power exiting the vehicle is the velocity of the wind going through the propeller multiplied by the same force. Since the wind speed is less small, much less than the road speed, the power in is greater than the power out. The input power in the video comes from the treadmill.
It's just as accurate to say the power comes from the air, the treadmill, or both. It's simply a matter of the frame of reference you choose for the analysis.
Well, it works only on a treadmill. In open space once the vehicle reaches the speed of wind there is no wind that can power the vehicle. If you go downwind on a vehicle at the speed of the wind you will feel no wind once you travel at its speed. Simple. It's all relative.
Lots of people post their incorrect opinions and state them as fact. It's true that when the cart reaches wind speed the occupant would feel no wind at all. But the spinning propeller still would - and the cart continues to accelerate beyond wind speed.
Nope. The prop always behaves as a propeller - not a turbine. The wheels are spinning the prop - not the other way around. So even at exactly wind speed, the prop is creating thrust to continue accelerating the cart.
Unfortunately people I have attempted to show this video claimed that there was a big fan behind the treadmill, artificially altering the windspeed. Perhaps you guys could repeat the experiment in a closed room, and circle the treadmill with the camera to show that there are none.
hardly a breakthrough; no educated scientist would contest that per bernoulli's principle a craft can go significantly faster than the wind speed that powers it.
I find the way the video presents this as a breakthrough, or at odds with scientific understanding to be misleading.
I'm sorry if you think we've presented this as a scientific breakthrough. That's not our intention. As it happens however, there are plenty of scientists that continue to claim it's impossible. That's as surprising to us as it is to you.
The prop not only rotates, it travels in a line relative to the ground. The complete motion is a spiral. It is designed to be pushed linearly harder than it is pushed to rotate so it rotates backward. This creates a zone of wind slowing down as it is sucked from in front and pushed back behind the prop. The cart sees it as accelerating it's apparent wind by using ground motion to drive the prop.
I think the confusing part is that in a 10mph wind when the cart gets to 10mph there is no relative wind over the prop. At this point there has to be a little bit of stored energy in the prop to get the cart going faster than 10 mph. Once this happens the relative wind reverses for the prop and it continues to tap energy and can then pick up more speed.
I haven't read all of the previous posts so I hope this is not a duplicate explanation.
That is one of the confusing parts, but that's not what happens. At no time does it rely on stored momentum or stored energy. Even when the cart is going exactly the speed of the wind it will continue to push against us, or push its way up an incline indefinitely.
If the cart moves 5m/s then if the wheels are braking with a force of 1N you have 1N*5m/s=5J/s=5W of power for the propeller. If the propeller takes previosly stationary (relative to car) air and accelerates it to 2m/s backwards, then it can generate a force of 5W/(2m/s)=2.5N a net forward force of 1.5N
Where did this power surplus come from? Well the air was pushed backwards, so seen from the ground it went from 5m/s to 3m/s - that is: it lost energy and gave it to the car.
Ice boat or multi hull on a dead down wind run in a 10 mph wind it will hit lets say 8 mph now bear off to at an angle to dead down wind and the wind the sail sees (apperent wind) is now an added additional force that will propell to faster than the actual wind but you just cant do it dead down wind with a sail. now may be another device like a propeller can make use of this dead down wind foward motion vector and add it to foward thrust just like a sail does on a reach.
Maybe I am missing something. Isn't the cart going toward the wind instead of away or downwind (wind at its heals?) Many of the posts here do confuse the notions of Force, Energy and Power. Going downwind in the way illustrated here isn't really a paradox. The power delivered by the propeller may be the same as the power delivered by the wheels but this doesn't mean that the forces and velocities have to be the same. Consider a block and tackle system, its ability to do work and the forces.
What this cart demonstrates on the treadmill is that it will go directly downwind faster than the wind on an open road. In other words we could have a 10 mph wind from North to South, and this vehicle would go 15 mph from North to South, propelled by that wind. Yes, an observer on the vehicle would feel wind in his face at that point because he's going faster than the wind. But the cart is still going "downwind" because both the cart and wind are going the same direction over the ground.
I am sorry, I misunderstood the setup. The wheels are driving the propeller in a reference frame in way emulating running before the wind. I thought it was the wind from the treadmill from the attached layer that was driving the cart. I was mistaken. Still, I'm not sure I understand why this is considered a paradox. I can get a spool of thread to roll toward me faster than I can pull as long as it is drawn from underneath it. It is pretty elementary exercise in rotation dynamics.
One of my students (and later, my son) told me how to grab the other related videos. This is a cool demo. I may get rid of my yo-yo demo and assign this one instead. Great job.
As I explained to superlox3, he is onto some of the key parts of the "puzzle". But there are some aspects he didn't get quite right. See my comment below.
The trick is that the propeller doesn't make the wheels move, the wheels make the propeller move. That's why it needs a push to gain momentum at the start, but after that since the wheels add to the propeller speed it is quite possible to move faster than the wind.
This speed adds on itself, the faster the cart moves the faster the propeller will move and the more propulsion it will have.
The cart does not need a push to start. We have a couple of videos showing it self-starting in a tailwind. Also, it will not continue to just go faster and faster. With a given gear ratio, the cart will have a theoretical maximum speed relative to the wind. Getting past 2X wind speed is possible but challenging.
It's obvious that you have devised some sort of sorcerous matter that takes out friction, and applied the said matter on the wheels, most likely in the form of some gel of sorts.
The belt is supplying the energy for the prop to turn; pushing the cart up against the belt; wheels turn more; prop spins more; pushes harder against the belt, etc.
The faster the belt, the more quickly the cart will accelerate, i think.
I think there is a lower limit to the speed of the belt where this will occur.
Decrease speed; you should be able to keep the cart static in the middle of the belt, or lower where the forward push of the prop is too little for the belt to impart more energy.
Yes, but with a traditional sailboat you can't sail directly downwind faster than the wind. That's part of what makes this vehicle both interesting and also hard to believe for some people.
This deals with a concept that I have been thinking about. One must think about the ratio between the wheel's circumference and the rod's circumference. This ratio corresponds with the rotations per unit of time. If the wheel's circumference is 5 times the axle's circumference, the turbine will spin 5 times as fast as the wheels.
eg:
ground moves at 10 meters per second.
Wheel circumference = 10 meters.
Rod circumference = 2 meters.
The rod will rotate 5 times faster than the wheel. Simple!!
I think you've got a couple things turned around. The ratio of the wheel advance vs. the prop advance is an important parameter, but it's not related to the ratio of diameters of wheel and rod.
A great problem! I study Aeronautics and Astronautics at Purdue and this problem stuck me for a couple of days. The answer is not perpetual motion and it's easier than you think. A drag powered vehicle cant go DWFTTW. The answer is lift. The angled prop produces a small lift in the forward direction in addition to drag power. This is why DWFTTW is possible. This is also why racing bikes have limitations on spoke designs if you were curious. The effect is small, but not zero.
Lift-generating forces are not immune from the requirement to conserve momentum, unfortunately. You'll learn this next semester.
Lift connotes drag: you are accelerating air that was previously happy being vertically stratified into a downward direction. This is not free - when analyzing energy flows, and is the reason you can't have a heavier-than-air glider that stays up nearly indefinitely. For the same reason, heavier planes require more powerful engines.
You are correct, lift does induce pressure drag and some skin friction drag. You are also correct that momentum is conserved (I'm fairly confident that I as a senior or my professors would not have suggested it would not) the issue s conserving it in all directions. The relative velocity of the air over the prop being faster than freestream may be the key, I will investigate this further. This must still be possible because sailboats do it and employ the same principle. Very good problem...
While counter intuitive, it does not violate any principles of physics. First, there is a energy source that it is tapping, the tail wind. I know the cart goes faster than the tail wind, but the tail wind is required or the cart will stop.
Consider how unintuitive a heat pump is - it is more efficient at warming a house than directly warming the air with an electric heating element. The cart it more efficient at transferring energy into forward momentum than a direct push of the wind.
Seeing this for the first time, I was missing a key piece of information: The fact that the wheels where powering the propeller. I caught that the third time through. After careful consideration, it does sound like perpetual motion.
Someone with all the facts should be able to solve this with a fairly simple equation. The question is, how can a propeller deliver more force than that required to turn it. It must power the vehicle that powers the prop.
It seems like perpetual motion, but it stops when the wind stops (which makes it a rather poor perpetual motion machine). We look forward to discussing it with you on one of the many forums that are addressing the topic.
I'm starting to get it. The device will only travel through air that is close to it's ground speed. Since it doesn't have to overcome much wind resistance, the energy is sufficient to maintain forward motion.
oh i get it now. hmm I still wonder how well this would work if they placed it in a wind tunnel or something instead of on a treadmill. I guess it'd be limited by gear-ratio and the fact that wind resistance increases as a square of speed
Obviously it would work just as well in a wind tunnle as everywhere else. But it would be hard to study because it would speed of down the tunnel and hit the end quickly.
I don't buy it. Probably could be done, but the treadmills not a cart in the wind. Goodman video only one I could. find showing one. I didn't see an explanation about how speeds were determined either, wind or cart, or any neutral observers. And what about gusts? They could keep that wind sock showing higher speed than wind speed after a lull, via the kinetic energy. This is all pure woo science at this stage.
What difference is there between the cart on the treadmill and the cart in the wind? The treadmill test is very analogous to a wind tunnel test for a wing. It allows you to limit distractions. If it works on the treadmill it will work in the wind.
I actually discovered this 3 years ago on the internet on an old PDF scientific document.
It was concerning boats and it was to sail DIRECTLY UPWIND (not like sailboats) with a fan. I found some pictures and an old GIF video of a boat with a fan sailing upwind.
I wanted to build a model but it required certain skills and patience.
So, for me, obviously this thing is no trick and I am very happy to see it.
Shame on all the people who said "it is impossible" without checking concretly.
make a demonstration video on how to exactly replicate this device. So everyone can build one according to your design. this is important. We need to kick the scientific society in the nuts if we ever are gooing to evolve old physics in deperate need of an overhaul.
"Old" physics isn't in need of an overhaul. What's going on here is predicted by physics known for hundreds of years. It's just a surprising and unintuitive application of what we've known for all these hundreds of years.
I'll admit, I was a little skeptical when I first heard of this idea. As soon as I saw the design, I had an "A-Ha!" moment. It's so simple, yet completely non-obvious. Anyone who thinks this is impossible just doesn't understand mechanical engineering or physics.
Nice. This is maybe the same as using a card with a propeller that pushes the cart directly into the incoming wind. If the card has little surface area for the incomming wind to push it back, then the propeller can move the cart upwind...
Making the cart light and efficient is necessary, but not sufficient. Without explicitly taking advantage of the energy available at the ground/air interface the cart would never quite achieve steady-state wind speed.
Physics says energy cannot be created or come from nothing. Thats energy not speed. Energy = speed x force. If you have extra force, you can convert it into speed. Wind force is wind speed squared so at higher wind speeds you definately have extra force to convert into speed.
I think you're getting a little excited, jeremiah. I will work things out in any way i choose and it is not for you to tell me the correct or incorrect way to get my head around things. I think your arrogance is your main downfall, here. Both in the working out of the experiment and in your correspondence with others.
The higher pressure difference can speed up the cart faster than the wind but the speed increase is limited. The cart has weight and experiences friction which use up the available energy. The available energy is not (as many assume) the same as the wind speed. It is proportional to the cube of wind speed.(wind speed x wind speed x wind speed) As wind speed increases, extra energy comes from the increasing wind force. Thus the cart is better at going faster than wind at higher wind speeds.
The wind makes a turning force (torque) on the prop but the prop is geared to the wheels. The same wind makes a torque on the wheels which opposes the prop torque. The connection between them is geared to give the wheel torque the advantage. Thus the cart rolls with the wind and the prop sucks air from in front of the cart and pushes it behind the cart into the wind. This increases high pressure behind the cart and low pressure in front beyond the pressure difference normal for that wind.
It would be opposing wind pushing against wind, which would allow it to go faster than the pushing wind. In other words there is excessive trust in relation to, ratio to, the devices total weight/drag and it accelerates because of that excess.
michaelqshaw 4 months ago
If this is based on honest people sharing what they built, the answer is mechanical advantage. If, a gear attached to the rotor is made in a ratio to rotate 3 times to the 1 time rotation of the driving gear attached to the wheels that is only mechanical advantage. Explaining why it would start on a tail wind, if the device was light enough, even against the tail wind, once the propeller began to produce thrust, it would be opposing wind pushing against wind.
michaelqshaw 4 months ago
That is brilliant, thank you
BC3012 8 months ago
Would this principle be useful for a wind-aided bicycle? Or would the propeller required be too big/heavy to be practical.
WestLABoy 10 months ago
@WestLABoy
You could use the principle on a bicycle, but it would be impractical for a lot of reasons (not the least of which is the safety issue). Also, the torque of the prop would be trying to push you over all the time. And without pivoting the whole prop mount, it would only work directly upwind or downwind.
spork33 10 months ago
@tezropunkel They show you how to make your own cart. Feel free to do it yourself and prove them wrong....
pwpike 1 year ago
@pwpike As an engineer I feel totally myself to build a cart that would runs using windpower.
As a realist I know that I'll never find a 1 km of a straight isolated road, a wind source that blows constantly along the path on that road, of course I will not find 10 anemometers in my closet to put along the road. I won't be able to test the speed of the cart so that it doesn't hurt the results.
There are lots of thing that defines the real experiment from the amateur propellers on the wheels.
tezropunkel 1 year ago
@tezropunkel Depends on what you're trying to prove. I don't need to know exact numbers to see if the cart's moving 3x faster than windspeed, just like I don't need instruments to tell a car is moving faster than a bike when it's moving 3x faster. I only need those numbers if I'm trying to make a physics formula or something. I think it's pretty clear that these guys (as well as others) have demonstrated DWFTTW, and you don't need to know exactly how fast the wind or the cart was to see that.
pwpike 1 year ago
@pwpike Am i getting it right that you say that you can clearly see how fast the wind goes and compare it to the speed of the cart? I mean, I can't. Neither can anybody by the way unless he has an anemometers built inside a head or something. You know it sounds like "Look there are invisible fish in the aquarium" and believe that...
tezropunkel 1 year ago
@tezropunkel As I said, you can build your own cart and prove this wrong if you wish. The physics seems fine to me; the evidence seems clear enough; it's been validated by an independent 3rd party; you have the ability to debunk the theory. Seems like pretty sound science to me.
pwpike 1 year ago
I guess this shouldn't be too surprising, given that no one has a theory called the conservation of speed. Now, if someone managed to show that the DDWFTTW don't obey the conservation of energy, now that would be something!
Good video though, thanks!
alpinevisions 1 year ago
I would LOVE to see this on Mythbusters.
jimday666 1 year ago
Poor choice on audio mixing. It's very annoying to those of us who hear with only one ear.
paulgibeault 1 year ago 2
@paulgibeault
I agree. That was not intentional. It was more a result of the free program we used - and our lack of video editing skills. Sorry.
spork33 1 year ago 5
@paulgibeault true, annoying.
jimday666 1 year ago
This is quite an amazing device, and so simple at the same itme. I plan to build my own small model.
Are there any specific ratios regarding gearing between the propeller shaft and the axle, with wheel diameter in mind?
A little question on the side ( call me crazy; I'm no physicist ) but what will happen if you reverse the propeller direction? Would it be possible to make it go upwind at equal speed to the wind, or perhaps slightly more?
jake5680 1 year ago 2
@jake5680
We established a world record with "Blackbird" by going directly downwind at 2.8X wind speed. This winter we'll be replacing the propeller with a turbine (which will look just about the same) so we can go directly upwind faster than the wind.
spork33 1 year ago 2
@jake5680
The top speed (either upwind or down) should only be limited by the efficiency of the power transmission between the propeller and the wheels.
technolope 1 year ago
@jake5680
The top speed (either upwind or down) should only be limited by the efficiency of the power transmission between the propeller and the wheels.
technolope 1 year ago
Comment removed
jake5680 1 year ago
@jake5680
Look for my build videos under "spork33". They will walk you through a build with part numbers and everything.
spork33 1 year ago 2
So, in theory, if one pushed / towed this vehicle up to a certain speed on a calm day and then let it go free, would it accelerate up to some speed and then continue to travel at that speed until it ran out of road?
ehu42 1 year ago
@ehu42
Sadly no. With no wind the cart will coast to a stop on level ground from any speed.
spork33 1 year ago 3
@spork33 in #4 video you've said there was no wind. i don't get it.
someman7 1 year ago
@someman7
The air in the room is still - relative to the room. Rather than move air over the surface (wind), we move the surface beneath the air (same relative motion - still "wind").
spork33 1 year ago 2
@ehu42
This video has confused you.
There is energy being added to the system in the video by the motor running the treadmill.
When the same cart is outside on the road the energy is being added by the wind on the blades.
The 2 scenarios are mathematically interchangeable.
MrHurricaneFloyd 1 year ago 4
Sure, I can see that the cart is going uphill on the treadmill....but this does still not verify their claim that the cart can move faster than the tail wind. To do that they need further instrumentation... Specifically, they should have setup a meter to show what the speed of the wind is and also shown us the speed of the treadmill. Without that how do we know it is truly going faster than the tailwind???
grhd76 1 year ago
@grhd76
The air in the room is still. This is demonstrated in some of our other videos. Only the belt is moving. If the vehicle maintains its position on the treadmill it is going downwind at exactly wind speed. Just as you would feel no wind if you rode your bike downwind at wind speed, the cart experiences no wind at this point. If it advances on the treadmill, it begins to experience a relative headwind, as you would if you rode your bike DDWFTTW.
spork33 1 year ago 6
Makes sense to me, the wind that's pushing the kart is the actual breeze plus what's generated from the propeller. All of that total only has to be enough to keep the kart from losing momentum. If you placed the thing on the treadmill with everything constant but the propeller not generating thrust, it would slowly drift backwards, not fly backwards instantly. Like a plane taking off on a treadmill, the treadmill isn't pushing the plane, just spinning it's wheels.
DrNeroCF 1 year ago
It would be hard to do, but it would be cool if you could measure the drag force the cart exerts on the treadmill. I'm guessing that's where the primary energy input to the system is. either version, treadwill or wind powered, is getting its energy from slowing down the relative motion of the air and the ground.
I have to admit, I probably wouldn't have given this much thought without seeing your demonstration. good job!
momerathesoutgrabe 1 year ago
@momerathesoutgrabe You're correct - on both points. The energy does come from slowing down the two media relative to one another - and we found it difficult to instrument the retarding force on the axles due to the vibration.
spork33 1 year ago
Forgetting the tread mill and putting the vehicle on the ground with a 10mph tail wind the vehicle moves forward by the wind on surfaces of the vehicle and the force generated by the spinning propeller. When the vehicle reaches 10mph it has zero tail wind force but has gained kinetic energy which transfers back to the propeller moving the vehicle forward. However, the kinetic energy is lost with friction and the vehicle will slowly return to a speed below that of the wind, cycle starts over.
capnbrown 1 year ago
@capnbrown
Sorry Capn - but it has nothing to do with capturing the kinetic energy of the vehicle, and it doesn't settle back to less than wind speed. The manned vehicle we built will do better than 2.5X windspeed continuously.
spork33 1 year ago
I can explain it but you may prefer not to know. Look away now.
A brick does no work sitting on a table. A little vehicle does no work standing still. Think of energy and forces but separately. Work done is different from force.The vehicles start stationary and use drag on the vehicle body to move it forward which spins the propeller which now has its own rotating velocity with lift separate from the vehicle.The vehicle speed matching wind speed is nothing special to the propeller. Its levers!
jparsons2222 1 year ago
Comment removed
jparsons2222 1 year ago
This has been flagged as spam show
Seems to me that the prop is angled in such a way that the cart is "pinched" between the wind and the treadmill just as a boat on a tack is "pinched" between the wind and the water via the keel.
heathwoodscience 1 year ago
OMG! Black Magic!
NadimAJ 1 year ago
I was skeptical once too, however the NALSA record for DDWFTTW is near ratification! nay-sayers can begin preparing their apologies.
Congrats to the ThinAirDesign team!
FlyingZippy 1 year ago
I hope mythbusters never responds to this. It would be like telling a 5 year old that there is no Santa Claus. Unnecessarily cruel.
superifico 1 year ago 2
@superifico
There's really no need for them to do it now - since we've done it with a 23' tall, 450 lb, manned vehicle that will be setting a new world record in the next few weeks.
spork33 1 year ago 8
@spork33
;o)
superifico 1 year ago
Comment removed
superifico 1 year ago
@spork33
It is wonderful when skeptics get pwned by the sheer reality of a working physical prototype. Skepticism which is shallow and falsely intellectual is what these "naysayers" are all about. It is their way to convince open, yet weak, minds of their logically-fallacious debunkery. I can see through the axe-grinding of these shallow naysayers and distinguish them easily from the honorable class of meek skeptics who, in a seemingly miraculous manner, manage not to make asses of themselves.
kmarinas86 1 year ago
@superifico Seems to me that the prop is angled in such a way that the cart is "pinched" between the wind and the treadmill just as a boat on a tack is "pinched" between the wind and the water via the keel.
heathwoodscience 1 year ago
Comment removed
alexfair8589 1 year ago
@alexfair8589
I see that your comment has been removed. Does that mean that YOU removed it?
spork33 1 year ago
The drag force of the tailwind pushes on the vehicle like a parachute. The corresponding power decreases by a cubic function approaching zero at TAS=0mph. On the other hand, the torque delivered to the fan by that same tailwind attempts to turn the wheels backwards. However, because such backwards torque is due to pressure change from the rear of the prop to its front, which itself is a function of prop speed, the vehicle moves forward....
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
This has been flagged as spam show
When the craft moves faster than the wind, TAS>0. The drag force of the "headwind" pushes on the vehicle, but now its torque on the prop helps sustain forward movement of the wheels. The power of this increases, at best, by the cube of TAS. However, friction and drag forces that are linear with lower speeds become quadratic at higher speeds, and corresponding power losses are quadratic and cubic respectively. This has a compounding effect on the power transfer to the vehicle, limiting velocity.
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
@kmarinas86
Complete nonsense.
spork33 1 year ago
This has been flagged as spam show
Typos found:
"If the cart goes forward on the belt, it's going faster than that 10 mph tailwind."
It's more complicated than that. To travel faster than a 10 mph tailwind, its true air speed must be *POSITIVE*. The wheels must spin faster than the speed of the treadmill + 10mph. Compared to the situation with no treadmill, with the treadmill, the prop will generate a higher thrust corresponding to this higher wheel speed. Whether a given prototype will work depends on *POWER* balance.
kmarinas86 1 year ago
This has been flagged as spam show
@spork33
"Complete nonsense."
Nice point to make. Would you mind quoting the now deleted typo ridden post you were actually criticizing?
BTW, I'm not against DWFTTW at all. I actually hate it when people such as yourself, who tell it like it is, are called quacks or advocates of perpetual motion. That's why I'm here. AFAIK, those "ardent DWFTTW deniers" or "pseudo-anti-pseudoscience people" or "science pseudo-experts" should be called out for their statements of "complete nonsense", not me.
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
Why the hell do emotions even enter into it. If you need a belief system, there's a church right down the road. This is science you idiots. Science is and always will be the study of how wrong we are.
AliasUndercover 1 year ago
@AliasUndercover
"Why the hell"
"you idiots"
"there's a church right down the road"
My emotometer just exploded.
kmarinas86 1 year ago
This has been flagged as spam show
@AliasUndercover
"Why the hell do emotions even enter into it. If you need a belief system, there's a church right down the road. This is science you idiots. Science is and always will be the study of how wrong we are."
The truth is that emotions have entered the "debate". The video above gives the impression that people saying this is an obvious hoax perpetrated by quacks are emotional themselves. It is funny, because those who try to defend science with emotion are the least credible.
kmarinas86 1 year ago
@AliasUndercover
"Science is and always will be the study of how wrong we are."
Science is not the study of how wrong we are. Science shows how wrong we are. Science is the study of things and their phenomena, which we believe we know well about, yet actually don't, in a way (via the scientific method) that will allow us to know the err of our thoughts.
kmarinas86 1 year ago
I'm curious as to how the wheels are connected to the fan. I understand that turning the fan turns the wheels, but does turning the wheels turn the fan?
Suppose the wheels drive the fan:
With little friction in the wheels, and the treadmill going very fast, you would expect the vehicle to roll with gravity, but with the wheels spinning very fast in the other direction (driven by the treadmill). In this case, the wheels spinning cause the propeller to turn, pushing it up... No?
crazyswedishguy 1 year ago
@crazyswedishguy
"I'm curious as to how the wheels are connected to the fan. I understand that turning the fan turns the wheels, but does turning the wheels turn the fan?"
Yes.
In one video, the wind from the rear forces the blades CCW. However, rolling the cart and wheels forward forces the blades CW. If the air flow from rear to front creates CCW rotation, CW rotation produces air flow from front to the rear. Source of the energy of F2R thrust is the drag of the wind pushing the cart.
kmarinas86 1 year ago
This has been flagged as spam show
@crazyswedishguy
"With little friction in the wheels, and the treadmill going very fast, you would expect the vehicle to roll with gravity, but with the wheels spinning very fast in the other direction (driven by the treadmill). In this case, the wheels spinning cause the propeller to turn, pushing it up... No?"
Correct.
kmarinas86 1 year ago
Comment removed
crazyswedishguy 1 year ago
The problem with DWFTTW is that good, informative articles and videos on this subject are hard to come by, and reasonable analyses seem to get lost in the shouting. I myself thought initially that this couldn't work, then worked it out on my own, only to be insulted by the rabid DWFTTW supporters who obviously don't have a clue how it works but feel entitled to belittle reasonable skepticism. If you can't explain it to the lay-person, it's not science, just engineering.
superhakujin 1 year ago
@superhakujin
"If you can't explain it to the lay-person, it's not science, just engineering."
Why do you believe science can't be explained to the lay person?
kmarinas86 1 year ago
@kmarinas86 That's the opposite of what I said.
superhakujin 1 year ago
Comment removed
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
This has been flagged as spam show
@superhakujin
"That's the opposite of what I said."
Sure, but you claimed that what cannot be explained to a layman cannot be science. But that is not the definition of science. Science is science whether understood by laymen or not. If no layman can understand a certain specialist part of science, that is not science's fault. That's the scientists' fault.
watch?v=aWzbazYGKJM
kmarinas86 1 year ago
I've been sort of following your saga to try to make skeptical sciencey people understand. You might try pointing them at this video: Cz4sf-pZ8jk , which is not the same thing, but shows the same principle. Replace the geared bar (rack) with "wind" and the gear (pinion) with "perfectly efficient propeller" and it's clear it's theoretically possible, and then your video shows it's possible in practice as well.
ribsngibs 1 year ago
Did the Mythbusters finally do an episode on this? I know they did one where they flew an airplane rolling on a treadmill.
Nomoreidsleft 1 year ago
@Nomoreidsleft
"I know they did one where they flew an airplane rolling on a treadmill."
It is strange how (or even why) they prove it. Many assume that the treadmill is supposed to go the same speed as the plane's wheels, but the only force required to do that is for the prop to generate enough thrust to overcome friction at the wheels, etc. If you get the prop to produce any more thrust, it will go forward like any other plane, and the only difference is the wheels will spin faster.
kmarinas86 1 year ago
@kmarinas86
"I know they did one where they flew an airplane rolling on a treadmill." (Continued...)
A lot of people imagine that the plane on treadmill scenario implies that the plane's wheels are moving as fast the treadmill, and the reason is that exercise treadmills, the kind people usually regard as treadmills, have an front and end not very far apart from each other. If the trust is not astronomical, the plane will be far below stall speed, and it will not fly.
kmarinas86 1 year ago
@Nomoreidsleft Nope. We tried everything to get them to do it. We gave up and decided to do it ourselves. If you look at traderturok's youtube videos you can see a segment the Discovery show did on our cart a few days ago in Canada.
spork33 1 year ago
This has been flagged as spam show
Wind speed relative to cart speed is irrelevant. It's like saying airplanes will never fly because they are heavier than air. It's converting he angular momentum of the propellers to linear momentum of the cart. So as long as the wind is strong enough to move the propeller they go forward.
Nomoreidsleft 1 year ago
It's hilarious that so many people can watch this and still not get it.
AlephNeil 1 year ago
@AlephNeil
"It's hilarious that so many people can watch this and still not get it."
No it is sad. It is direct proof that some people can make systematically wrong conclusions due to their "education". Why does it take a few weeks or so for a cynic to change his mind about something like this? They have to be missing something important in their reasoning.
kmarinas86 1 year ago
When you jog on ground, you can feel the relative wind. When you jog on a treadmill, you don't feel the win.
I think the point of this demonstration is that the torque provided by the wheel should cancel by the counter torque made by the wind on the propeller, thus the cart move at most at constant speed. Apparently , so is not the case..
vietarc 1 year ago
@vietarc When you jog at 10 mph in a 10 mph tailwind you don't feel any wind. That is exactly the scenario we're demonstrating on the treadmill. If the cart goes forward on the belt, it's going faster than that 10 mph tailwind.
spork33 1 year ago
Comment removed
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
Comment removed
kmarinas86 1 year ago
The treadmill is an invalid surrogateg... ignore it for the red herring that it is.
If you have a cart on level ground with a 10mph tailwind, the cart can start and accelerate nicely... there's no controversy there. BUT, as the speed of the cart nears the speed of the wind behind it, the windspeed over the propeller will drop to zero as will any force generation.
Without force generation there is no energy to move the vehicle. Bottom line... physically impossible.
kuhndj67 1 year ago
And yet we have a 300 lb cart that stands 22' tall that will carry a driver directly downwind faster than the wind. We will be testing it on the dry lake bed next week for the first time.
If you think the treadmill is not valid, you simply don't understand that all motion is relative.
spork33 1 year ago
@kuhndj67 This note is to update spork's reply. Yes they ran their man sized version at the dry lake bed, and it performed far past expectations. They were hoping for twice wind speed and it looks like they were at three times wind speed. Congrats boys, you did great!
subductionzone 1 year ago
@kuhndj67 said;
The treadmill is an invalid surrogateg... ignore it for the red herring that it is.
,.. as the speed of the cart nears the speed of the wind behind it, the windspeed over the propeller will drop to zero as will any force generation.
Without force generation there is no energy to move the vehicle. Bottom line... physically impossible.
I wanted to show how wrong you were now that the issue has been settled, the nay-sayers deserve to be pointed out and made fun of as they did!
nixter1nixter1 1 year ago
You're storing energy. When the vehicle is held stationary on the mill the excess kinetic energy is stored by the propeller. The energy is dissipated as the vehicle moves forward. When you stop it with the spork the energy is replenished. You are not letting it move far enough to dissipate the energy.
I am not a physicist but I play one on TV.
MegaUnbeleivable 1 year ago
When it's maintaining position on the treadmill it is expending exactly as much energy as it's using. The only time energy is being stored is the time during which the prop is being accelerated. The only time that energy gets used is when the prop is slowing down.
spork33 1 year ago
Spork,
One of your main arguments is the reference to ice-boats. I have searched and can find no hard data (gps speed, wind speed, wind angle, vmg angle) to confirm that ice-boats can achieve a downwind component greater than true wind. Sure, they can go 3 or more times windspeed at 90degrees, but show us data on what they do at 135degrees. I'm a windsurfer of 15 years and know it can't be done. Windsurfers hold the speed record and it is less than true wind at 135degrees.
WindSphinx 2 years ago
I've been a windsurfer for over 20 years and I can assure you it CAN be done. I can't post a URL here but if you search on "cetus iceboat" and click on the first link you'll see the data you want.
spork33 2 years ago
@WindSphinx
WindSphinx, I would encourage you to attend either an iceboat regatta or a dirtboat regatta so you can witness first hand what you say cannot be done. I assure you that it can be done. I do it everytime I sail. We can do it so easily, that no data is necessary. You can see it with your own eyes.
789995 1 year ago
@789995 They did take their man sized cart to Ivanpah and ran it at close to three times the speed of the wind directly downwind. They were very well received by NALSA.
subductionzone 1 year ago
So the wheels generate the power behind the fan, which then push the cart forward, generating more speed via fan? Or am I misunderstanding this?
Dexistomors 2 years ago
@Dexistomors The wheels provide the power that turns the propeller which pushes the cart. It sounds like perpetual energy, but it isn't . The power for it comes from the air. The cart runs off of the difference between air speed and ground speed. After the cart passes it leaves behind a path of air that has been slowed down relative to the ground. If there is no wind there is no power available for the cart to run on. It is a feedback system very much like a tacking boat experiences.
subductionzone 2 years ago
One thing you'll notice about machines like this and other things like the windmill driven boat direct against the wind are that they serve to decrease the relative velocities of air to the other medium they happen to be travelling in.
mukmuk7 2 years ago
It is not free energy. It is extracting from the pool of energy that is two different media with differing relative velocities.(the air and ground in this case) or air and water in other cases.
Note the equation Energy = Force X distance. The force created by the fan can be greater without violating the conservation of energy law than the force exerted on the wheels, as the distance the wheels travel relative to the road is greater than the distance travelled by the fan relative to the air.
mukmuk7 2 years ago
I want to buy one. How much will you sell one (that works well outside) for? You should sell them as toys... I think you'd make a fortune if you could make them pretty cheap. Looks cool.
gmrecneps 2 years ago
Look at my other videos. I posted a series of three bideos that takes you through the build process in detail. I also give all the part numbers etc., as well as where to get them.
spork33 2 years ago
I imagine the rotation of the propellor as being like a helicopter's rotor on its side, then can consider the familiar forces of 'drag' and 'lift'. Lift propels the cart forwards whereas drag opposes the rotation of the prop, and hence acts to slow the cart down. However, the connection between the wheels and the prop is such that a small change in prop speed causes a relatively large change in cart speed. Hence, by some 'lever law', the lift 'wins' and the cart is propelled forwards til AOA=0.
ancalagon12321 2 years ago
There is power that can be extracted from the difference in speed between the ground and the wind. The power entering the vehicle is the velocity of the ground multiplied by the force from the propeller. The power exiting the vehicle is the velocity of the wind going through the propeller multiplied by the same force. Since the wind speed is less small, much less than the road speed, the power in is greater than the power out. The input power in the video comes from the treadmill.
halcyonmje 2 years ago
It's just as accurate to say the power comes from the air, the treadmill, or both. It's simply a matter of the frame of reference you choose for the analysis.
spork33 2 years ago
How was the vehicle made at 0:23???
But anyways great vid i've seen the others but i want to try it at home so any info on how to construct it would be great.
Kaza128 2 years ago
Well, it works only on a treadmill. In open space once the vehicle reaches the speed of wind there is no wind that can power the vehicle. If you go downwind on a vehicle at the speed of the wind you will feel no wind once you travel at its speed. Simple. It's all relative.
protztom 2 years ago
Lots of people post their incorrect opinions and state them as fact. It's true that when the cart reaches wind speed the occupant would feel no wind at all. But the spinning propeller still would - and the cart continues to accelerate beyond wind speed.
spork33 2 years ago
it spins the other way so thers no propulsion from it as it reaches the wind speed,it would only decelerate the cart?
spshecot 2 years ago
Nope. The prop always behaves as a propeller - not a turbine. The wheels are spinning the prop - not the other way around. So even at exactly wind speed, the prop is creating thrust to continue accelerating the cart.
spork33 2 years ago
Unfortunately people I have attempted to show this video claimed that there was a big fan behind the treadmill, artificially altering the windspeed. Perhaps you guys could repeat the experiment in a closed room, and circle the treadmill with the camera to show that there are none.
AcerbicMaelin 3 years ago
We address that concern in "Downwind Faster than the Wind #7"
spork33 3 years ago
Yeah, I found that whole sequence only after I'd seen this little introductory one. Good work, guys!
AcerbicMaelin 3 years ago
hardly a breakthrough; no educated scientist would contest that per bernoulli's principle a craft can go significantly faster than the wind speed that powers it.
I find the way the video presents this as a breakthrough, or at odds with scientific understanding to be misleading.
Lemondud101 3 years ago
I'm sorry if you think we've presented this as a scientific breakthrough. That's not our intention. As it happens however, there are plenty of scientists that continue to claim it's impossible. That's as surprising to us as it is to you.
spork33 3 years ago
Haha, yes indeed, this is hardly a breakthrough just a novelty.
Yet I have had endless discussions with my advisor - a professor in physics - whether or not this is possible.
It is not at odds with scientific theories, yet it is apparently very counter-intuitive to many people, even educated scientists.
On the upside, once I get around to building one myself, I win a bottle of wine.
Sgrunterundt 2 years ago
The prop not only rotates, it travels in a line relative to the ground. The complete motion is a spiral. It is designed to be pushed linearly harder than it is pushed to rotate so it rotates backward. This creates a zone of wind slowing down as it is sucked from in front and pushed back behind the prop. The cart sees it as accelerating it's apparent wind by using ground motion to drive the prop.
Wesnex1 3 years ago
I think the confusing part is that in a 10mph wind when the cart gets to 10mph there is no relative wind over the prop. At this point there has to be a little bit of stored energy in the prop to get the cart going faster than 10 mph. Once this happens the relative wind reverses for the prop and it continues to tap energy and can then pick up more speed.
I haven't read all of the previous posts so I hope this is not a duplicate explanation.
lead2feather 3 years ago
That is one of the confusing parts, but that's not what happens. At no time does it rely on stored momentum or stored energy. Even when the cart is going exactly the speed of the wind it will continue to push against us, or push its way up an incline indefinitely.
spork33 3 years ago
Can you offer an explanation how the propeller extracts energy when there is no air moving past the blades...cart moving 10 mph in 10mph wind?
lead2feather 3 years ago
Sure.
If the cart moves 5m/s then if the wheels are braking with a force of 1N you have 1N*5m/s=5J/s=5W of power for the propeller. If the propeller takes previosly stationary (relative to car) air and accelerates it to 2m/s backwards, then it can generate a force of 5W/(2m/s)=2.5N a net forward force of 1.5N
Where did this power surplus come from? Well the air was pushed backwards, so seen from the ground it went from 5m/s to 3m/s - that is: it lost energy and gave it to the car.
Sgrunterundt 3 years ago
Comment removed
Sgrunterundt 3 years ago
Ice boat or multi hull on a dead down wind run in a 10 mph wind it will hit lets say 8 mph now bear off to at an angle to dead down wind and the wind the sail sees (apperent wind) is now an added additional force that will propell to faster than the actual wind but you just cant do it dead down wind with a sail. now may be another device like a propeller can make use of this dead down wind foward motion vector and add it to foward thrust just like a sail does on a reach.
ifishli 3 years ago
Maybe I am missing something. Isn't the cart going toward the wind instead of away or downwind (wind at its heals?) Many of the posts here do confuse the notions of Force, Energy and Power. Going downwind in the way illustrated here isn't really a paradox. The power delivered by the propeller may be the same as the power delivered by the wheels but this doesn't mean that the forces and velocities have to be the same. Consider a block and tackle system, its ability to do work and the forces.
phytch 3 years ago
What this cart demonstrates on the treadmill is that it will go directly downwind faster than the wind on an open road. In other words we could have a 10 mph wind from North to South, and this vehicle would go 15 mph from North to South, propelled by that wind. Yes, an observer on the vehicle would feel wind in his face at that point because he's going faster than the wind. But the cart is still going "downwind" because both the cart and wind are going the same direction over the ground.
spork33 3 years ago
I am sorry, I misunderstood the setup. The wheels are driving the propeller in a reference frame in way emulating running before the wind. I thought it was the wind from the treadmill from the attached layer that was driving the cart. I was mistaken. Still, I'm not sure I understand why this is considered a paradox. I can get a spool of thread to roll toward me faster than I can pull as long as it is drawn from underneath it. It is pretty elementary exercise in rotation dynamics.
phytch 3 years ago
One of my students (and later, my son) told me how to grab the other related videos. This is a cool demo. I may get rid of my yo-yo demo and assign this one instead. Great job.
phytch 3 years ago
Phytch <<You are completely rigth, but that wont stop people from thinking they have every thing figured out and claiming that it is impossible.
Sgrunterundt 3 years ago
SuperLux3 nailed it! My "amature intuition" tells me that this is that provocative of a question.
Jedlmind 3 years ago
As I explained to superlox3, he is onto some of the key parts of the "puzzle". But there are some aspects he didn't get quite right. See my comment below.
spork33 3 years ago
Obviously this is witchcraft.
Very nice video though, I'm glad to see actual experimentation being done rather than just arguing about theory.
theoriginal42 3 years ago
The trick is that the propeller doesn't make the wheels move, the wheels make the propeller move. That's why it needs a push to gain momentum at the start, but after that since the wheels add to the propeller speed it is quite possible to move faster than the wind.
This speed adds on itself, the faster the cart moves the faster the propeller will move and the more propulsion it will have.
superlox3 3 years ago
The cart does not need a push to start. We have a couple of videos showing it self-starting in a tailwind. Also, it will not continue to just go faster and faster. With a given gear ratio, the cart will have a theoretical maximum speed relative to the wind. Getting past 2X wind speed is possible but challenging.
spork33 3 years ago
Ah, thank you for the clarification.
superlox3 3 years ago 2
It's obvious that you have devised some sort of sorcerous matter that takes out friction, and applied the said matter on the wheels, most likely in the form of some gel of sorts.
Universum4444 3 years ago
Shhhh!!!
spork33 3 years ago
well this should be on it
blink1420 3 years ago
The belt is supplying the energy for the prop to turn; pushing the cart up against the belt; wheels turn more; prop spins more; pushes harder against the belt, etc.
The faster the belt, the more quickly the cart will accelerate, i think.
I think there is a lower limit to the speed of the belt where this will occur.
Decrease speed; you should be able to keep the cart static in the middle of the belt, or lower where the forward push of the prop is too little for the belt to impart more energy.
cribley 3 years ago
which i can see you've done in "Downwind Faster Than the Wind #6"
cribley 3 years ago
Hope you win, I'd like to see that myth tested.
opower95 3 years ago
you can sail faster than the wind, of course this is possible.
acidbass808 3 years ago
Yes, but with a traditional sailboat you can't sail directly downwind faster than the wind. That's part of what makes this vehicle both interesting and also hard to believe for some people.
spork33 3 years ago
that is wrong... ther are already solutions for this problem. They All involve some kind of sail with extra movement towards the boat...
yeustm 3 years ago
"They All involve some kind of sail with extra movement towards the boat"
And this means they're NOT a "traditional sailboat". My statement is correct.
spork33 3 years ago
And decrease axle size.
h1ghj3sus 3 years ago
My theory is that car's with proper gears could have much better gas mileage by using larger Circumference wheels.
h1ghj3sus 3 years ago
This deals with a concept that I have been thinking about. One must think about the ratio between the wheel's circumference and the rod's circumference. This ratio corresponds with the rotations per unit of time. If the wheel's circumference is 5 times the axle's circumference, the turbine will spin 5 times as fast as the wheels.
eg:
ground moves at 10 meters per second.
Wheel circumference = 10 meters.
Rod circumference = 2 meters.
The rod will rotate 5 times faster than the wheel. Simple!!
h1ghj3sus 3 years ago
I think you've got a couple things turned around. The ratio of the wheel advance vs. the prop advance is an important parameter, but it's not related to the ratio of diameters of wheel and rod.
spork33 3 years ago
A great problem! I study Aeronautics and Astronautics at Purdue and this problem stuck me for a couple of days. The answer is not perpetual motion and it's easier than you think. A drag powered vehicle cant go DWFTTW. The answer is lift. The angled prop produces a small lift in the forward direction in addition to drag power. This is why DWFTTW is possible. This is also why racing bikes have limitations on spoke designs if you were curious. The effect is small, but not zero.
shoto2kyu 3 years ago
Lift-generating forces are not immune from the requirement to conserve momentum, unfortunately. You'll learn this next semester.
Lift connotes drag: you are accelerating air that was previously happy being vertically stratified into a downward direction. This is not free - when analyzing energy flows, and is the reason you can't have a heavier-than-air glider that stays up nearly indefinitely. For the same reason, heavier planes require more powerful engines.
lesqual 3 years ago
You are correct, lift does induce pressure drag and some skin friction drag. You are also correct that momentum is conserved (I'm fairly confident that I as a senior or my professors would not have suggested it would not) the issue s conserving it in all directions. The relative velocity of the air over the prop being faster than freestream may be the key, I will investigate this further. This must still be possible because sailboats do it and employ the same principle. Very good problem...
shoto2kyu 3 years ago
While counter intuitive, it does not violate any principles of physics. First, there is a energy source that it is tapping, the tail wind. I know the cart goes faster than the tail wind, but the tail wind is required or the cart will stop.
Consider how unintuitive a heat pump is - it is more efficient at warming a house than directly warming the air with an electric heating element. The cart it more efficient at transferring energy into forward momentum than a direct push of the wind.
Civbert1 3 years ago 4
Great work! Thanks for posting.
rossmcd 3 years ago
Seeing this for the first time, I was missing a key piece of information: The fact that the wheels where powering the propeller. I caught that the third time through. After careful consideration, it does sound like perpetual motion.
Someone with all the facts should be able to solve this with a fairly simple equation. The question is, how can a propeller deliver more force than that required to turn it. It must power the vehicle that powers the prop.
IOW: Perpetual motion. I still call BS.
Bucknik 3 years ago
It seems like perpetual motion, but it stops when the wind stops (which makes it a rather poor perpetual motion machine). We look forward to discussing it with you on one of the many forums that are addressing the topic.
spork33 3 years ago
I'm starting to get it. The device will only travel through air that is close to it's ground speed. Since it doesn't have to overcome much wind resistance, the energy is sufficient to maintain forward motion.
You're right. It's not perpetual motion.
Thanks for making my brain hurt.
Bucknik 3 years ago
"Thanks for making my brain hurt."
Sure it may kill a few brain cells - but only the weak ones! : )
spork33 3 years ago
if the treadmill is going 10mph shouldn't there be wind blowing at 10mph for the experiment to show dwfttw
swimkid4 3 years ago
The surface of the treadmill moving at 10 mph relative to still air creates the same situation as a wind blowing at 10 mph relative to the ground.
coolaun 3 years ago
oh i get it now. hmm I still wonder how well this would work if they placed it in a wind tunnel or something instead of on a treadmill. I guess it'd be limited by gear-ratio and the fact that wind resistance increases as a square of speed
swimkid4 3 years ago
Obviously it would work just as well in a wind tunnle as everywhere else. But it would be hard to study because it would speed of down the tunnel and hit the end quickly.
Sgrunterundt 2 years ago
I don't buy it. Probably could be done, but the treadmills not a cart in the wind. Goodman video only one I could. find showing one. I didn't see an explanation about how speeds were determined either, wind or cart, or any neutral observers. And what about gusts? They could keep that wind sock showing higher speed than wind speed after a lull, via the kinetic energy. This is all pure woo science at this stage.
MultiplePersonas 2 years ago
What difference is there between the cart on the treadmill and the cart in the wind? The treadmill test is very analogous to a wind tunnel test for a wing. It allows you to limit distractions. If it works on the treadmill it will work in the wind.
subductionzone 2 years ago
I actually discovered this 3 years ago on the internet on an old PDF scientific document.
It was concerning boats and it was to sail DIRECTLY UPWIND (not like sailboats) with a fan. I found some pictures and an old GIF video of a boat with a fan sailing upwind.
I wanted to build a model but it required certain skills and patience.
So, for me, obviously this thing is no trick and I am very happy to see it.
Shame on all the people who said "it is impossible" without checking concretly.
Newtoon 3 years ago
make a demonstration video on how to exactly replicate this device. So everyone can build one according to your design. this is important. We need to kick the scientific society in the nuts if we ever are gooing to evolve old physics in deperate need of an overhaul.
Abrin19 3 years ago
"Old" physics isn't in need of an overhaul. What's going on here is predicted by physics known for hundreds of years. It's just a surprising and unintuitive application of what we've known for all these hundreds of years.
I'll admit, I was a little skeptical when I first heard of this idea. As soon as I saw the design, I had an "A-Ha!" moment. It's so simple, yet completely non-obvious. Anyone who thinks this is impossible just doesn't understand mechanical engineering or physics.
prometheusg 3 years ago 2
Nice. This is maybe the same as using a card with a propeller that pushes the cart directly into the incoming wind. If the card has little surface area for the incomming wind to push it back, then the propeller can move the cart upwind...
bbkingdom 3 years ago
Unfortunately, I don't know what this means.
spork33 3 years ago
It seem also long the cart is super light and efficient it can faster than the wind.
spark300c 3 years ago
Making the cart light and efficient is necessary, but not sufficient. Without explicitly taking advantage of the energy available at the ground/air interface the cart would never quite achieve steady-state wind speed.
spork33 3 years ago
Physics says energy cannot be created or come from nothing. Thats energy not speed. Energy = speed x force. If you have extra force, you can convert it into speed. Wind force is wind speed squared so at higher wind speeds you definately have extra force to convert into speed.
Wesnex1 3 years ago
I think you're getting a little excited, jeremiah. I will work things out in any way i choose and it is not for you to tell me the correct or incorrect way to get my head around things. I think your arrogance is your main downfall, here. Both in the working out of the experiment and in your correspondence with others.
dannym3141 3 years ago
The higher pressure difference can speed up the cart faster than the wind but the speed increase is limited. The cart has weight and experiences friction which use up the available energy. The available energy is not (as many assume) the same as the wind speed. It is proportional to the cube of wind speed.(wind speed x wind speed x wind speed) As wind speed increases, extra energy comes from the increasing wind force. Thus the cart is better at going faster than wind at higher wind speeds.
Wesnex1 3 years ago
The wind makes a turning force (torque) on the prop but the prop is geared to the wheels. The same wind makes a torque on the wheels which opposes the prop torque. The connection between them is geared to give the wheel torque the advantage. Thus the cart rolls with the wind and the prop sucks air from in front of the cart and pushes it behind the cart into the wind. This increases high pressure behind the cart and low pressure in front beyond the pressure difference normal for that wind.
Wesnex1 3 years ago