Thanks 😁😁 it makes me very happy to have you as a visitor on my little channel! I have really enjoyed thinking about this design, thanks so much for introducing me (and 6+ million others) to it.

I hope that you picked up 10k for this Derek. It's nearly worth that for riding in that vehicle as it looked scary as hell with that out of balance prop.

@@EngineeringwithRosie , Hi Rosie! A good video - you really did explain how the craft can travel faster than the wind! Although I believe you made a slight mistake. I also made a video about this machine on my teeny tiny channel where I explain that there is in fact no mode difference in propulsion above and below windspeed. kzfaq.info/get/bejne/ech-dt1hxM-zZ5c.html Please check it out, I'd love to know what you think!

@@chalichaligha3234 you have made some great illustrations there, well done. I really liked your explanations. I don't think I made the mistake you mention, but perhaps I wasn't very clear. The prop starts generating thrust as soon as the wheels start turning, so that is a constant as soon as it has any movement at all. But at very low cart speeds, the greater part of its forward-acting force will come from bluff body drag. Do you not agree there is any bluff body drag pushing the cart forward below wind speed that changes direction to start pushing it backwards as it crosses wind speed?

@@EngineeringwithRosie I think that at low speed the greater part of the force on it is coming from the drag _on the propeller._ This is evident with the small model cart, which doesn't have any body to speak of.

Same here

Agreed!

I'm really happy to be one of them!

Yep this has been fun seeing people respond to this.

The windspeed measurements in the tests are nonsense. Behind a sail on a sailboat the windspeed is greatly reduced. You've built your whole model on the propeller reducing the speed of the wind to get power and then measure it downstream of the propeller. How about driving a car along at the same speed as the cart with wind indicators on a mast? If the system really works the wind direction will be reversed at that speed.

Wow, thanks! Right back at you: nicely done!

LMAO. April fools. No one can see putting a wind turbine on backward doesn't make the vehicle go in reverse.

Hey John, will the next version allow you to make negatie pitch for faster starts?

@@EngineeringwithRosie why are you congratulating this abusive troll?

you coulda hidden the electric motors better, like the do in pro cycle racing.

Glad I could help!

just keep trying. that is how you eventually get it.

You were lucky to have a 6th grade teacher who understood how sails work!

You’d have conversion losses to deal with twice, but there may still be an envelope where it can work?

The air speed at the ribbon is not the same as the distant wind speed, because: - The ribbon is before the prop. The prop is accelerate the air backwards, so it deccelerate the wind. The ribbon is in wind shadow. - The wind speed near the ground is lower than higher. - May the wind and the cart direction not egsactly the same. - Usw.

where is the spreadsheet?

​@@nadavsofer2686 It's the one she shows in the video

@@SassySimian How did you get the spreadsheet?

@@anterokaarakka62 It's the one she's showing in the video. You could probably get it from her or reproduce it.

@@widgewunner I don't know if we deserve any respect, but I'd be a lot happier if we weren't being called idiots and charlatans.

Haha, What a comment from the man himself.

@@Rick_Cavallaro you work for military intelligence. so yeah, idiot & charlatan is about right.

Hi, I've have same thoughts. We have initially still car and no wind at all. We push the car to certain speed. Can the thrust be bigger or equal to the drug. /Biker can use still cars to accelerate himself/?

@@malingeorgiev2962 "We have initially still car and no wind at all. We push the car to certain speed. Can the thrust be bigger or equal to the drug." No, it is essential that the air is moving *relative* *to* *the* *ground* or else the cart cannot extract energy from the air to accelerate.

Ah, fascinating. So propellers work in the same way as money printers... BRRR

@@ak205 Air conditioning makes me go BRRRR!

I love it! And I'm right with you.

It’s funny because basically that’s what’s happening. As long as you get enough thrust from the wind on the blades when it’s relatively stationary to develop a little bit of vehicle momentum you can get the prop to just do prop things. It won’t really do you a hell of a lot good on a draggy keelboat, but the transition from prop-as-static-sail to prop providing thrust driven by craft’s mass acting on the wheels (or underwater prop if you wanted to try this with a boat) when you’ve got your drive ratios and pitches right on an efficient-enough platform, is essentially there from a very low speed above rest

I think if the problem was explained properly in the Veritasium video, it wouldn’t have come across as counter-intuitive. The Veritasium video misleads you to think that the propeller is a turbine driving the wheels, but this is not the case, the wheels drive the propeller which is what produces the thrust, like the propeller on a plane. My view is the initial video is very misleading Edited to correct propeller

@@philippetts1701 The veritasium video never claimed that. Also, if you cannot explain it to someone else, you do not understand it...

Thanks! I enjoyed drawing myself into that cart 😀

That's a HUGE testament to Rosie's talents!

@@satunnainenkatselija4478 the cart initially accelerates from a stand-still in a tail wind (simply being pushed by the wind as a bluff body). Once it's moving, the propeller begins to generate thrust which is able to take it to, and beyond, wind speed.

Most engineers do not sail, I guess ^_^

@@Rick_Cavallaro But Mr.Cavallaro, you didn't answer my question under your video: If the propeller is generating thrust, then the cart could also move in a still atmosphere provided we give it an initial velocity. The cart doesn't need any wind. What is the role of the wind BEFORE (I repeat BEFORE) the cart reaches the wind speed? It has no role at all. The cart can move forever.

@@MitkoGorgiev >> If the propeller is generating thrust, then the cart could also move in a still atmosphere provided we give it an initial velocity. The prop won't generate thrust on a still day. >> What is the role of the wind BEFORE It pushes the cart. >> (I repeat BEFORE) t I repeat IT PUSHES THE CART! >> It has no role at all. I'm sorry, I thought you had a question. You find this is a better way to learn things? >> The cart can move forever. NO.

Well I am Australian so that counts as polite here. Thanks!

That's maybe the most polite thing I've seen on the topic. :)

Actually just call her a Bloody Legend, Cheers from Las Vegas!

There is...you simply say "wow! That's awesome!" Or if you are English you can say "My word!" or "Good Lord!" or even "Oh, I say!"

@@funquay2219 "my word" ? Are you like 1000 years old?

I mean the first video explained it better than was done in the follow-up wager video. You combine the two expertly, and with the simplicity which I understand.

>> As you say, once you understand the physics, it's not impossible. Even if you don't understand the physics, it's still possible. :)

If you sail directly downwind, you do not exceed the velocity of the wind.

8 timed the speed of the wind? The record for landsailors is arround 4 times , 135mph and an iceboat has never been recorded that fast.

I saw one talking the math on it, and saying that it couldn't. Lol does he still have a job? I know he lost $10k on the bet.

>> Have no one of them ever heard about Oberth effect? The Oberth effect is in fact a super nifty thing, but it's unrelated to how this works.

Shit - now I think I've made a fool of myself. I have never stopped to realize this lever effect ends up manifesting as the Oberth effect. My apologies! I'm leaving the above comment in place as a testament to me being wrong. :(

@@Rick_Cavallaro, shows good caricature!

This basically boils down to pulleys/gear ratios. I find it kind of funny that what we call "simple machines" are still stumping scientists.

research zero point energy and overunity effects. Wings have "negative" drag here in this vehicle. Some large industrial vacuum pumps speed up shortly when they are shut down. If one would apply a brake to keep the system in that state, one could extract energy. They did it on the atomic level, slowing down a hydrogen atom with a laser until the proton should collapse into the core at 0 Kelvin. But this doesn´t happen and one can continue to cool it down forever. Tesla an Viktor Schauberger understood these sweet spots in vortex systems.

"an open system extracting energy from the wind" that puts it in a nutshell and makes everything clear. The more formal explanation of this video is very nice too though.

@@martinjandt9573 no, it’s nothing to do with “overunity”. It’s extracting energy from the relative motion between the air and the ground. No need for zero point energy here.

@@dreamok732 if you think that puts it in a nutshell then I don’t think you understand the issue. That statement is true, the energy comes from the relative motion between the air and ground but the mechanism it uses is totally counterintuitive. How’s this for weird. If the prop and transmission efficiencies are 100%, the force accelerating the kart is infinite when the kart reaches wind speed. Tell me that makes sense!?!?!

😂 oh man this exact thing happened to me about fifty times during the making of this video. Even now I sometimes wake up in a cold sweat thinking I've found another "paradox"!

I think a rear-facing propeller would be better, since the supporting structure wouldn't disturb the vortex nearly as much. Actually, two of them would be better for stability, one over each rear wheel, along with them being triple-blade, to avoid some resonance.

Thanks, I'm really glad it helped 😀

Ha ha! Well there is more to the spreadsheet than I showed, but in the end I felt I would be setting a bad example to show too many details of my spreadsheet model with about 10 design variables that I calibrated with a single design point...

@@EngineeringwithRosie Can we see the spreadsheet?

@@EngineeringwithRosie Yes, it is a bit of a laugh, really.

Ha ha, just for you 😉

Oh that sounds cool 😊 I did see a few other examples of downwind faster than the wind, maybe I'll pull them all together on a post later on.

@@EngineeringwithRosie You'll find that on my channel: "under the ruler faster than the ruler" :)

The engineer and sailor, Theo Schmidt was the first to do it with a model. He published an article over 20 years ago in Catalyst, the journal of the Amateur Yacht Research Society. It may be available online.

@@petersharp6833 - The Brennan torpedo operates on the same principle, and was made in 1877. The physics people at the time had already determined it would work, before committing the money it took to build the setup. Wikipedia has an article on Brennan torpedo.

it’s strange that you didn’t figure it out, look at the explanation, странно что вы не разобрались, вот посмотрите объяснение kzfaq.info/get/bejne/g6ugl6ySvJyUdas.html

@@Olexsy952 Это объясняет движение пропеллера, но не системы тележка-пропеллер. Как только тележка достигнет скорости ветра никаких сил, со стороны ветра, на пропеллер действовать не будет и тележка будет продолжать двигаться только за счет иннерции всей системы, постепенно приходя в состояние равновесия сил. На мой взгляд, фокус кроется в стойках поддерживающих пропеллер. Уж очень напоминают парус-крыло. Учитывая что ветер не ламинарный поток, а вихревой это создаст ту самую таинственную силу, позволяющую превысить скорость ветра. Но, теперь движитель не пропеллер, а парус.

yes it's the new flat earth. google promoted that too.

I still don't get it. As I understand it, the wind pushes the cart and is where all the ultimate energy comes from. The wheels now rotate, and being chained to the propeller, it also rotates. So, the wind is pushing the cart AND rotating the wheels against the ground + propeller chain resistance AND rotating the propeller via the wheels. And I understand that whatever wind energy the propeller takes up in being turned continues to be replenished by MORE wind until the cart is at wind speed. Thus the cart is absorbing more energy from the wind than one without a propeller would. I get that. Now the propeller converts this extra wind energy absorption very efficiently into forward motion, so it more than makes up for its drag and maybe the cart gets up to wind speed sooner than a plain cart. BUT the instant the cart goes faster than the wind, the wind is no longer pushing it. No energy is being input into the system. All the saved up energy in the propeller turning will allow the cart to exceed wind speed for a while but ultimately without any push to overcome the drag and frictions the propeller should slow down by degrees until the cart is back at wind speed again. UNLESS the answer lies in the fact that the propeller converts energy into forward motion (and turn the wheels) more efficiently than the turning wheels and chain create drag??? But that's perpetual motion, except for the fact that you do need a wind input. I DON'T UNDERSTAND

@@greatbriton8425 "the instant the cart goes faster than the wind, the wind is no longer pushing it. No energy is being input into the system." There's still energy being input into the system. Even though the cart is going faster than the wind the propeller is spinning fast enough that overall the cart is *slowing* wind down behind it rather than accelerating it. This is where the energy is extracted from.

@@greatbriton8425 in the test, the measurements for the wind speed was a streemer in front of the propeller. That will give you a FALSE reading slower than the actual wind speed.

@@lelandtsnyder9684 No, the streamer was to indicate speed of wind RELATIVE to cart.

@@greatbriton8425 that what I said. You won't get that the n front of the propeller.

Oh wow are you serious?! I have been doing it wrong this whole time! Thanks so much for taking the time to tell me that 😀😀😀

Sailboats can travel faster then wind - IF the wind hasn't the same direktion then the boat. With only complete tailwind it is impossible! Faster then wind are only the blades of the Propeller but not the vehicle. In my opinion it is a very good fake.

@@guri311 //"Faster then wind are only the blades of the Propeller but not the vehicle. "// This is incorrect. The entire vehicle is traveling directly downwind, faster than the wind.

@@johnborton4522 No, this is not possible, because then the force to the blades gets a direction AGAINST the driving direction. Why should there be a forward force, when the propeller wants to turn in the opposite direction? There ist no reason.

@@guri311 It's a brainteaser. Keep trying ... you'll figure it out.

I have sailed catamarans. If you go directly down wind, you just go at the speed of the wind... *BUT* ... if you go *DIAGONALLY* downwind, the relative velocities (boat air) are actually faster, and your net downwind speed is FASTER. Note that we're using the phenomenon of lift (like an aircraft's wing) so you get lift in a different direction (i.e. not so useful) but the lift is GREATER, so there's a net benefit, i.e. a net gain in down-wind speed. This just proves that there is a way to extract more energy from the difference of two velocities (air v. water) and you are effectively using a gear ratio.

Good, but surely her assertation that below the windspeed the cart is pushed by it's body's drag force is incorrect. I demonstrated in my video that even if the body had no interaction with the air, the cart would accelerate from rest up to it's maximum speed.

​@@chalichaligha3234 Chali, I am one of the primary designer/builders of the Blackbird so I have a complete understanding of the craft. I watched your excellent video and it's clear that you too have grasped the concepts in their entirety (nice work). As far as the initial motion from rest (where the propeller has not yet begun to develop thrust), it takes very little drag against the tailwind to get it started. You are likely correct that if the body magically had no drag at all, merely the drag against the propeller would get the vehicle moving. Conversely, if you took the propeller entirely off the Blackbird, the drag on the chassis alone would be enough to get it started rolling at accelerated to some percentage of windspeed. In the end, since by necessity they both exist on the craft, it is the drag from both that start the initial motion.

@@chalichaligha3234 One more comment on your excellent video. You use the word "turbine" to describe the rotor of the Blackbird. You are correct that the function of the *entire vehicle* is to act as a turbine and slow the wind relative to the ground. You can even argue (as you did) that that is the function of the rotor itself. You're not wrong in that, but we find that to get people to understand how the device works, we first have to get their minds out of the track that it is the wind hitting the blades directly that is turning them (like a normal wind turbine). Most people understand how a wind turbine works (input thrust, output torque). Most people understand how a propeller works (input torque, output thrust). Since the rotor of the Blackbird functions as the latter, we find it confuses people less to describe it individually for what it is ... a propeller. In the end, use whatever words or concepts you need to get your understanding of the craft across to people -- you're one of the few who truly get it right as to how it works. Well done.

​@@johnborton4522 , I am humbled by your praise. I'm just happy that my explanation did justice to the machine in your eyes. I understand what you mean about confusing people if considering it a turbine. One of the several commenters on Steve Mould's video after taking in the consensus we had reached on the thread produced a diagram that is perhaps the simplest explanation of the machine. I couldn't find it, but have recreated it: ibb.co/1b8jh0d It shows that a faster than the wind downwind machine can be powered by a Savonius turbine, which of course would not work if the wheels were driving it, as this type of turbine cannot double as a propeller.

@@chalichaligha3234 Again, you are spot on -- there are numerous ways to design a device which can travel directly downwind faster than the wind apart from one using a propeller. A few good examples from Rick here; kzfaq.info/get/bejne/jpyffdOfuLDdhmw.html However, IF you simply put a turbine rotor on a tower and put a cart under it (which is what people see when they look at the Blackbird), it will never work.

There are lots of ways to understand it. My background is aero and specifically wind turbines, so I analysed it like that. People who sail think of it like a tacking sailboat, and many people think the gears/ level/ screw way to understand is the most intuitive.

Realizing you had it wrong after you thought you understood it is 93.7% of the battle. Watch the video carefully (and repeatedly if necessary) and I'm confident it will become clear. But I warn you that lots of people do finally get it, and then find their mind questioning aspects of it. I think Rosie said she went through a bit of this if I recall correctly.

^^^^ THIS Changing the gear ratio between the wheels and the prop is the equivalent of using the rudder on the sailboat to change the angled path through the water (point of sail). Changing the pitch of the blades is the same as rotating a wing-sail on an AC racing yacht.

Not quite the same. From the boat's frame of reference, the source of energy is the apparent wind, and a component of lift (which by definition, is perpendicular to the apparent wind), is in the same direction as the boat, propelling the boat forwards. From the DDWFTTW cart's frame of reference, the source of energy is from the ground (the forward force of the wheels accelerates the surface of the earth by a very tiny amount, reducing the angular kinetic energy of the earth from the cart's frame of reference). Through reduction gearing, the drivetrain converts the higher speed, lower force from the ground into a lower speed, higher force at the propeller, despite losses. There is no analogy to reduction gearing for the boat.

@@rcgldr yes, the analogy is the angle between course and real wind. Have a high gearing (rotor spins fast) is like sailing at a wide angle. Low gearing, you are more parallel to the wind. No gearing and is like when you are sailing straight downwind. You have to find the optimal angle/gearing to optimize VMG.

@@markotrieste - A propeller is used because it's an efficient way to produce thrust. If turbine compressor with axis perpendicular to direction of wind was efficient enough, then it would work, with no equivalent to tacking. It is easier to see this in the case of a cart that interacts with two solid surfaces, where energy loss is not an issue. There is reduction gearing from table to ruler, so the cart moves under the ruler, faster than the ruler. There nothing that resembles tacking for this cart. kzfaq.info/get/bejne/oZOkpad3nb_QlJc.html

@@rcgldr just watch at 9:39. Sailboat at an angle.

Yes! That is a very clear analogy... wish I thought of it 😁

Great idea. And if you can imagine an axle across the boat, spanning the river with wheels on the two river banks, giving the rotational power to mechanically drive the oars you'd have an exact analogy.

But with rowing, we'd have an external source of energy to push the water away, right?

@@punya1621 Not if it's mechanically driven by the relative speed difference of the stream to the bank, via the wheels and axle, rather than a person. Rather than oars, you could drive a screw instead.

@@hankdewit7548I hate to admit it but even after watching two explainer videos on this (Steve Mould being the other one), I still don't understand it. 😔

And the propeller “pushes” against the air using what energy? The energy of the air molecules. When a flat sail is used instead of a propeller, the second Newton law applies: the air pushes the sail in one direction and the sail pushes the air in the opposite direction ( backwards). Is a rotating propeller that dissipates energy by pushing some molecules sideways more efficient that a sail? Why are we not using propellers instead sails in sailboats?

Yep they pitch, but manually. If I were to build one, I think I would try to make the pitching at least semi-automatic. And put a derailleur on it so I could change gears to optimise for both low and high speeds. A propeller is like a wind turbine in that its optimised for a single tip speed ratio (except that they are weirdos and use the inverse) and you mess that up as you go faster if you can't change gear.

@@EngineeringwithRosie One reason for the fixed gear ratio is to prevent using stored rotational energy of the propeller to accelerate. If the propeller rotation slows down, then so must the rotation of the wheels. They had to meet very strict NALSA requirements preventing any stored energy use for propulsion for their sailing record.

@@EngineeringwithRosie so in for example a plane, they don't change the RPM of the propeller to keep at the designed TSR? I think we're going to try to make a Blackbird in Ashes, it's just too cool not to do it!

@@AshesWindTurbineSimulation I volunteer in advance to help you however I can to beat our record. I have no doubt it's doable.

@@AshesWindTurbineSimulationif you make the simulation, I'll make a video about it... and maybe Rick can help us try to improve on the Blackbird design and make a new record attempt!

If this actually worked, you wouldnt even need a wind at all. You would only need to push it up to sufficient speed and it would run forever.

@@ronalddump4061 That's not true. Wind relative to ground is crucial for it to work.

The energy is coming from the wind.

@@seneca983 but it spins against the wind, its wrong direction

@@sebastjansslavitis3898 If the propeller were to spin in the opposite direction it would slow down the cart. It is the right direction. Consider the inertial frame tied to the ground. In that frame the wind gets decelerated by the propelled behind the cart so the air is losing kinetic energy and the cart is gaining some.

@@seneca983 it is right direction to produce thrust, but its not the direction wind would spin it. And thats the problem. It accelerates where it should decelerate

@@sebastjansslavitis3898 "its not the direction wind would spin it" The wind is not directly spinning it. It's being spun by the wheels to such direction that it generates thrust.

That is a different principle, and basically is a poor implementation of reverse thrust as used on commercial airliners.

Radiation pressure?

Maybe I missed something. Did the video say something can be blown around in a vacuum? Why would you ask this? The video talked about high pressure air and low pressure. You can't blow air if the air is removed. You can blow photons...which is electro magnetic radiation... to push a solar sail.

That's a good idea for a video, thanks for the suggestion! And also, I only learnt that term "jibing" after I recorded this video... I always get the sailing terms wrong every time I mention it in a video!

Stirling engine works on a temperature difference which is a bit different.

Yes, she is good at the con.

It could be me but as explained, it seems to me that if there is no wind, pushing it to sufficient speed should keep it in motion too. I'd love to see them put that to the test, even if it's just the driver pedaling until the prop starts accelerating the vehicle.

@@Neetje42ever no, because you need to be able to detract power from the wind. She mentioned in the beginning that an outside observer will see the wind behind the turbine being slower than in front. This won't be the case when there is no wind. ;)

@@Robbedem True but I wasn't looking at the general wind speed differences. If you look at 12:27 and beyond you'll see that a lot of the forward force isn't generated directly by thrust, but by lift. An aerofoil can generate a lot more lift compared to the drag it induces. The wheels have a lot less effort needed than it appears to keep the propeller spinning and generating lift. But I'm not an engineer and considering this sounds an awful lot like a perpetuum mobile, I'm just going to call bs on my own claims.

@@Neetje42ever actual energy is extracted from DIFFERWNCE in speed of GROUND AND WIND

@@Neetje42ever No, you are right, you don't need wind. You can move the ground instead, like the small modells they put on treadmills. ;D But it's the same thing as wind blowing, but i had to think about it for a few minutes.

YES! And when the flywheel kicks in to power the propeller to accelerate the vehicle to go faster than the wind there is no longer any wind pushing it, no more transfer of wind energy to the vehicle so that stored flywheel-stored energy gets used up and the vehicle slows down. The best you could do is fluctuate between a little bit faster than the wind and a little slower, with the AVREAGE SPEED of the vehicle being simply the wind speed.

@@RogerGarrett No, a cart like this can consistently exceed wind speed. It can accelerate even when going faster than the wind.

​@@seneca983 The claim is that it's the wind that provides the motive force. The wind pushes the vehicle from behind, accelerating it forward. If there's no friction (e.g. wheels against the ground, other mechanisms) then the vehicle MY accelerate up to the point where the vehicle is moving at the exact same speed as the wind. At that point there is NO FORCE pushing the vehicle. If the vehicle slows down (friction) then there will again be wind force against the back of the vehicle that can possibly once again accelerate it up to moving at wind speed. But once the vehicle is at wind speed there is no force, so what is it that powers the propeller? The vehicle certain is moving, it has MOMENTUM, and that momentum can indeed power the propeller (for some period of time). But that propeller DEPLETES the momentum of the vehicle, meaning that the vehicle will slow down, MUST slow down, and the propeller will turn more slowly. The wheels rotating against the ground only serve as the mechanism for TRANSFERRING the vehicle momentum into propeller motion, they are not a "source" of energy. Rather, the source of energy, once the vehicle is at wind speed, is the momentum of the vehicle. When that momentum is tapped into it explicitly means that the vehicle slows down. Slower vehicle means less momentum available for rotating the propeller. And IF, by some magic, the vehicle is ever actually going faster than the wind then there is no pushing force on the back of the vehicle but rather a relative pushing force against the FRONT of the vehicle, counteracting the momentum of the vehicle and further SLOWING IT DOWN. In other words, when the vehicle is going faster than the wind the wind is NOT powering the vehicle, yet the claim is that this vehicle is fully powered, at all times, directly by the wind, and in particular they discount the assertions concerning stored energy via momentum. So, HOW DOES IT WORK?

@@RogerGarrett "At that point there is NO FORCE pushing the vehicle." No, that's not true. Even at that point the propeller (powered by the wheels) is spinning and pushing the cart forward. Why aren't the wheels, which power the propeller then slowing the cart by at least as much? It's because the air is moving *relative* to the ground.

@@seneca983 It IS TRUE that the WIND is not providing a force to push the vehicle, which is what I was saying in that statement. The claim is made over and over, even by the original builder of the vehicle, that momentum is NOT what powers the propeller but that it is only the wind. The vehicle certainly is moving and its momentum can continue to cause the wheels to rotate, TRANSFERRING some of that momentum to the propeller. The wheels are NOT a "source of power", unless you figure in the momentum of the rotation of the wheels. Heck there's stored momentum even in the propeller and the shafts and drive train. But all of that momentum is NOT coming from the wind once the vehicle is going the same speed as the wind. And as any and all of that momentum drives the propeller that momentum gets used up and that explicitly SLOWS DOWN the vehicle. And again, if the vehicle ever WERE to be going faster than the ground-relative wind, the vehicle would then encounter a vehicle-relative wind coming at it from the front, being a DRAG on the vehicle and slowing it down. The claim is made that once the vehicle is going faster than the wind it gets its energy from the interaction of the wheels and the ground, which powers the propeller, and the propeller causes the vehicle to ACCELERATE, which causes the wheels to rotate even faster, which causes the propeller to rotate even faster, which causes the vehicle to move even faster, which goes on and on in an endless feedback loop. Now, seriously, where is all that extra energy coming from? Doesn't that look an awful lot like an Over-Unity claim, a mechanism that creates more energy than it uses?

Wow, thank you!

Sorry, it takes energy to to pull back on those wires, energy that is lacking in Rosie's overly rosy explanation. See my separate comment above - It is for sure possible to cause a wind powered craft to go faster, even much faster than a buoyantly neutral balloon traveling with the wind, but the craft can not sustain that speed, it will slow down. The best you can do is pulse the speed of a wind powered craft.

@@roberthigbee3260 Energy is there, in plenty, supplied by the relative movement between the wind and the ground. The vehicle takes advantage of the difference in speed of the two mediums to harvest velocity. It wouldn't work if the vessel were in contact with just one of them (that would require another energy source to "pull the wire", as you said in the case of the Brennan torpedo). I was struggling myself with this too until I saw Derek's cart demonstration, see at 14:00 here: kzfaq.info/get/bejne/r6mjmtJ9yMXKqn0.html (to be honest I still find it counterintuitive)

@@roberthigbee3260 - you missed the part "If the wires were attached to posts, the torpedo would move downstream faster than the stream." So from earth|posts frame of reference, only the water and the boat are moving, and there's no energy being used to pull back on the wires. As for sailboats downwind component of speed, called "velocity made good", the high end catamarans used in the America's cup racing have achieved an average downwind component at about 1.8 x true wind speed over a sustained period of time.

@@rcgldr I will look into your America’s cup boat claim which I am interpreting from your statement to mean that those high end cats, while zig zagging with the wind can actually go faster than a buoyantly neutral balloon floating with the wind. I am assuming you are not confusing the velocity vector of the boat pointing straight out the bow with the wind velocity vector. Boats for sure can go faster than the wind, but at an angle with respect to the wind. However, on an intuitive basis, and because it is hard to fake the performance of America’s cup yachts, I am predisposed to believe you, without further proof, that a boat’s velocity vector in the direction of the wind can also exceed wind speed. But boats, with their sails and tacking and keel-water interactions, operate entirely differently than the prop-car we are discussing. Bringing up boats muddies the discussion… it is part of the magician’s purposeful misdirection. I am not sure why you are also continuing with the Brennan torpedo analogy, this is also a totally different thing and is another misdirection. Also, many others arguments in support of this prop-car, not necessarily you, say the words “it’s all about relative speed” are just repeating stuff they heard others say without understanding. They also start talking about “lever action” without really knowing anything. Rosie talks about “energy balance”, but does not rigorously and conclusively prove where the energy is coming from. A lot of fuzzy thinking. To be fair to you, I will watch that video link you gave me about the $10,000 bet tomorrow to see if it has any meat to it. Thanks for your reply…. BTW, I once saw, with my own eyes, a guy saw a lady in half… I saw it, so it must be true right?

@@gastonpossel ​I watched the Veritasium $10,000 bet video and I am now a believer, but a big part of the confusion lies with false and confusing statements by everyone including Veritasium in parts of his video (he is a classic “over seller”). Here is what I wrote in the $10,000 Veritasium video comments: Life is a process. This Veritasium video is a process. This video has a lot of wrong and misleading statements, but at the end, gets the explanation correct, sort of. At the end, he still is promoting the treadmill experiment, which is for sure not doing what the Blackbird is doing (some aspects are similar, but it confuses things more than it helps). My next comments dissect this video by explaining what is said incorrectly or in a misleading way, but also congratulating Veritasium on the one good explanation he comes up near the end. Also, spoiler, the Professor ended up giving Veritasium the $10,000! Time mark 11:45 - false/misleading statement - “power is input into the system by the ground moving under the car”. The error in this statement is that there is zero energy created as the wheels interact with the ground. A transfer of energy within the “system” is all that can happen at the wheels. Saying “power is input into the system” at the wheels is the key not-true part of this statement. Presumably, he means the “system” is an imaginary dotted line (a “control volume”) that encompasses the entire vehicle (wheels, chassis, chain drive, mast & prop). The bottom line, clear as a bell, concept regarding energy, is that for Blackbird to accelerate, energy of some form has to enter this control volume. “Control volume” is a favorite concept with the Thermodynamic folks, but is it very useful in this discussion. The energy input could be that the ground was not really level and the energy input was really the exploitation of the potential energy due to Blackbird being higher at the start than at the finish, or due to momentary wind gusts as first proposed by the Professor. Olive branch - If the wind was steady, if the ground was level, if there were no hidden power sources on the vehicle, if the data was recorded properly (no hanky panky) and the Blackbird really and truly can go faster than the wind, in the same direction as the wind and for sustained periods at constant or accelerating velocities, then the only logical available external power source that can enter the system control volume is the wind (let’s ignore solar energy input for now). So, there must be some sort of unaccounted for prop thrust amplification factor that is sustained by the interaction of the wind and the control volume. BTW, the treadmill experiment is not a proof at all. There the energy input to the control volume is for sure at the wheels - the sloped treadmill transfers mechanical power to the wheels and then to the prop that generates thrust that moves the car forward and up the slope of the treadmill. This is not how the Blackbird interacts with the air. Consider a level surface, with zero wind - you could tow the Blackbird behind a pickup truck and watch the Blackbird catch up with and pass the truck, heck, it could then tow the truck… this ain’t gonna happen, but Veritasium’s mishmash of fuzzy explanations would make one think that could happen. Another error at time mark 12:40 - lever action and bicycles going up hill are inappropriate comparisons. Yes, a lever exists, yes, mechanically, the torque at the wheels can be less than the torque at the prop drive shaft because the rotational speed is faster at the wheels (Torque, lb in = (63025 * HP)/RPM). So, yes, the force acting at the periphery of the wheel can be smaller than the force generated by prop, this is plain old everyday physics, no magic, no mystery, not new. The missing concept is the source of the energy entering the control volume. The kid is the energy source on the bike, a lever does not move unless you expend energy to push down on one side of it. Time mark 14:20 - The “ah ha” moment - The little cart & 2x4 experiment - First off, and I don’t think he was trying to fool us, and he points this out too, watch carefully how the top big wheel is rotating counter clockwise. So, due to the ratio of the drive train, the small clockwise rotating wheels will drive the big wheel due to his energy input by shoving the board forwards, and the big wheel will “walk” along the board and go faster than the board’s velocity. **** The key here is that board is both the energy source as well as a body for the big wheel to push against. **** This was really the “ah ha” moment for me. Replace the board with the wind and imagine that the top big wheel has paddle wheel fins attached to each side such that they also rotate counterclockwise. The essential fact here is that the wind is the energy input and the paddle wheels have to have enough “bite” (call it friction sort of) to claw itself faster than the wind. Paddle wheels are too inefficient. The prop does the trick. I still stand by my earlier texts that the real problem here were the false and incorrect explanations from every one and that, from early on, I felt that for this thing to work, the interaction of the prop with the wind must be causing some sort of thrust amplification effect. Kudos to Veritasium for finally stumbling onto a good explanation, and that is what matters in the end.

KZfaq added an unwanted space, so be sure to click the "read more" to see my full comment.

>> in case of a battle between scientist and engineer I'd always take engineer's side I'm the one that conceived of it and built it with a friend, but I can't call myself the "inventor" because we learned that at least one other person had the same idea decades before me. That being said, I'm an engineer, but my title at my day job is "Chief Scientist" so I'm not sure which to root for. :)

@@Rick_Cavallaro Well, we - Russians, call people who mastered to perfection their engineering and craftsmanship skills "Levsha" ("Lefty" - character from one great fictional story) or Kulibin (Russian inventor). -You're, Sir, 100% deserve any of them!

@@AaaAaa-ly3on I've worked with lots of Russian engineers and I take that as a great compliment.

Sounds like you need to make that video visualising it in this way!

Best answer yet. You win the internet today!

In my mind, I picture an expanding 'teardrop' of red (indicating higher pressure) behind the propeller, which the prevailing wind is pushing against (and, of course, a corresponding 'blue' region of low pressure, in front). For me, the 'a-ah' was when I started to think of the wind blowing against the propeller, and pushing the whole vehicle forward. As the propeller turns, it begins generating an expanding volume of 'compressed' air, behind itself (thrust). At a certain point, the prevailing wind is no longer pushing directly on the physical propeller. Instead, it is pushing against this expanding volume of high pressure air, which resists being further 'compressed', and in turn, pushes the propeller forward, faster and faster, as the vehicle's wheels drive the propeller to expand that volume of compressed air, further and further behind.

@@CineSoar this high pressure wind buffer is a very common misconception with this vehicle. When we're moving faster than the wind, we don't have a tail wind pushing us anymore. At that point the propeller is pulling us through the air mass it finds itself in. But it has an advantage in that air mass since it's moving more slowly through that air than the wheels are moving over the ground. The aerodynamics around and through our propeller are exactly the same as that of a propeller on the front of a Cessna. In the case of a Cessna we don't imagine that the propeller has to create a high pressure air buffer for the wind behind it to push on.

Another way I'm picturing it, after further thought... You have a car, there is a 100' long screw, threaded through the body, most of it's length is coming out the front. The wheels are geared, to rotate the screw, which moves it out the back of the car, as it advances. If you push against the screw, you begin moving the car forward, faster than you are pushing the end of the screw. The difference is the ever-growing length of screw, between you and the car. Now wind is 'mushier' than that screw, but that is a minor adjustment to the scenario.

@Leberschnitzel I think that the financial cost due to his loss of reputation far exceeds the actual cost of the bet - and this is stated in the contract that was signed.

Not stonks for him.

@@ratandmonkey2982 "financial cost due to his loss of reputation" Has there been any such cost? I seriously doubt it. Everyone makes mistakes.

>> even on self-evident subject matters such as this one, you still make it interesting. She did an excellent job, and it's great that you're among the few that see this as self-evident; but it seems the vast majority find it somewhere between counter-intuitive and impossible to accept.

WADR one can not factually say what the "vast majority" thinks... Since many ppl who know its self-evident, do not waste time commenting on it.... And for example the "vast majority" on "flat earth" forums think the world is flat. That's why Science is based on fact and logic, not an inaccurate opinion poll based on the lowest common denominator ie YT and SM...

@@nc3826 I've been at this for more than a decade. I give you my absolute assurance that I know what the vast majority thinks. When I give talks on the topic I've never pre-selected the audience for non-believers. But thanks for telling me (the "Chief Scientist") how science works.