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A Follow up on the Faster Than Wind Cart

06/30/2021 4:00 PM

"A UCLA Physics Professor bet me $10,000 that my video about going downwind faster than the wind was wrong. "

Refer to :

https://cr4.globalspec.com/thread/149260/Can-You-go-Faster-than-Downwind-Speed-Directly-Downwind

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#1

Re: A Follow up on the Faster Than Wind Cart

06/30/2021 5:05 PM

Can anyone get in on this. I will bet on the side of the downwind racer...

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#2
In reply to #1

Re: A Follow up on the Faster Than Wind Cart

06/30/2021 5:30 PM

He's giving the money away to anyone who can make a video that displays physics problems that are contrarian to what would seem to be the case from the casual observer....things that would seem to work one way but actually work the opposite?

Like heavier objects fall at the same speed and light objects, assuming wind resistance matches....Like you wouldn't expect a fish to generate electricity, but an eel can shock the crap out of you....Like capillary action in straws and water where water can move uphill...Like a cheetah can run faster than a bird can fly...

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#3

Re: A Follow up on the Faster Than Wind Cart

06/30/2021 8:39 PM

In the earlier thread, I argued along some of the same lines as the professor. We both turned out to be wrong, although not for bad reasons. Of course, the earlier thread convinced me of the fact of faster-than-downwind speed, but it did not explain the how very well. This video succeeded. Thanks for the update.

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#4
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Re: A Follow up on the Faster Than Wind Cart

06/30/2021 10:36 PM

Yeah he does a much better job of explaining it than I did...and the model really helps

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#5

Re: A Follow up on the Faster Than Wind Cart

06/30/2021 11:26 PM

Xyla Foxlin just posted a video on youtube. Apparently it is possible.

https://youtu.be/VUgajGv4Aok

https://youtu.be/yCsgoLc_fzI

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#6
In reply to #5

Re: A Follow up on the Faster Than Wind Cart

07/01/2021 12:57 AM

There's an aptly named individual...

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#7
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 1:00 AM

Yup !

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#9
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 4:40 AM
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#8
In reply to #5

Re: A Follow up on the Faster Than Wind Cart

07/01/2021 1:31 AM

Fantastic! Thanks to you and to SE!

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#10

Re: A Follow up on the Faster Than Wind Cart

07/01/2021 5:52 AM

I can understand how it works and the physics of gear ratios and force multipliers but before it starts to move both the wheels and the prop are stopped. There is no force to be multiplied. How does it start to move?

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#11
In reply to #10

Re: A Follow up on the Faster Than Wind Cart

07/01/2021 6:40 AM

Well ordinarily it would be the wind....

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#12
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 9:24 AM

If the wind turns (windmills) the fan then the cart would move backwards so that can't be the method. I see no auxiliary sail or any provision for mounting one. How does the wind start the wheels turning to drive the fan? Does it need a push or a tow to start? Is there an electric/petrol drive to initiate motion? The explanation given for the physics does not hold when the cart is stopped. How does it get from a resting state where the physics won't work to a moving state where the physics will work?

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#13
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 11:31 AM

No mention of a uni-directional clutch in the drive train, but if there is, it would prevent the cart from moving backwards as you describe, and the wide blades would then initially act as sails to provide forward movement from rest.

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#14
In reply to #12

Re: A Follow up on the Faster Than Wind Cart

07/01/2021 11:34 AM

The car won't move backwards towards the wind, so the wind won't cause the prop to move backwards either (they're chain connected).

It sounds like the differential between the wheels and the prop is how it will start once the wind engages the vehicle.

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#15
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 1:53 PM

Yes, the prop and the wheels are chain connected, but as jhhassociates points out, when the cart is at rest, a tailwind will tend to turn the prop in a windmill fashion (opposite to its rotation when underway moving forward) which would move the cart rearwards. How then would it start? This seems to be a reasonable question. If initial forward movement from rest is a problem, I think a uni-directional clutch in the drive train would solve it.

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#16
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 3:17 PM

I believe that the ratio differential between the wheels and the prop is how it would start.

Yes, the wind would "tend" to move the prop in reverse, but the wheels/vehicle take less force from the wind to move forward and hence it does.

Or so I think.....

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#17
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 3:33 PM

I agree. As Zyla found and pointed out, both the diameter and the pitch of the prop have to be appropriate in order for it to work. If the pitch of the prop is too great, then it will windmill, and the device won't work.

The analog of the dolly moving in the opposite direction to the force exerted by the 2x4 is a great illustration of the forces.

Before seeing these videos, I'd have agreed with the professor. ...hardly the first time I've been wrong!

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#21
In reply to #16

Re: A Follow up on the Faster Than Wind Cart

07/02/2021 8:16 AM

Here is another example of the same principle:

"Stand on the ground beside a bicycle that faces right and has its pedal at the 6 o'clock position. Push the pedal left (clockwise). Which way will the bike move? Most people will answer that the bike moves forward as the pedal moves clockwise toward 7 o'clock. But, in fact, the bike moves backward and the pedal moves counterclockwise toward 5 o'clock. It is very easy to set this up with a real bicycle and the effect never fails to surprise. "

more...

If you install the Wolfram player, there is a simulator that you can use to play with the pedal angle and sprocket ratio.

The Bicycle Paradox - Wolfram Demonstrations Project

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#18
In reply to #12

Re: A Follow up on the Faster Than Wind Cart

07/01/2021 3:37 PM

In the real cart, not the model, the pitch of the propeller is adjustable....so when you start out the blade is flat and acts as a sail, its turning has no effect....when you reach wind speed, you then adjust the pitch with hand controls, to a sweet spot that exists in the ratio between the wheel size and the prop diameter as explained in the model by Xyla....

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#19
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 5:43 PM

Right. I forgot about the adjustable pitch. I nevertheless think that my suggestion of a uni-directional clutch has merit. Maybe it would even eliminate the need for pitch adjustment. If so, it would be simpler. After all, it is not as if all design variables have been tested.

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#20
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Re: A Follow up on the Faster Than Wind Cart

07/01/2021 6:49 PM

Well there probably is a weight limit, so simplicity is your friend....

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#22

Re: A Follow up on the Faster Than Wind Cart

07/03/2021 2:13 PM

I am convinced that the Blackbird car can go faster than the wind downwind, but if I were the professor I would not have paid the $10,000. because I am not satisfied with the explanation. Veritasium (Derek) attempts to explain what is happening by way of a couple of analogies:

1) The motorized treadmill/toy car demonstration is supposed to be analogous to the frame of reference of the Blackbird moving at wind speed - so from that frame the car is stationary in still air, and the ground is moving backwards, driving the wheels. The Power (Force X Velocity) of the moving treadmill is presented as analogous to the power of the wind, in this frame of reference, causing the ground to move backwards. It isn't. It is analogous to having a motor installed in the Blackbird driving it at wind speed.

2) Between 14:00 - 14:40 Derek uses a long board to push and roll a large wheel/small wheel toy car along the floor to demonstrate that the velocity of the toy car can exceed the velocity of the long board pushing it, with the explanation that this is analogous to the Blackbird car being able to exceed the velocity of the wind. But the long board being pushed by Derek is not analogous to wind. It is analogous to a motorized vehicle following the Blackbird and pushing Blackbird with a long pole.

Both of these analogies are inadequate because the power imparted by the wind is represented as a direct mechanical linkage to the Blackbird car. In the real world, no such mechanical linkage exists between the wind and the car. The wind is the ultimate source of power for the car, so at wind velocity and above the car must continue to extract power from the wind (no mechanical linkage allowed) to enable it to accelerate. Derek's statements: "At the wheels power is input into the system by the ground moving underneath the car. The power generated is the force of the ground on the wheels times the velocity of the car." (11:37 - 11:47); and, "So at wind speed the car can keep accelerating because the wheels turn the fan that blows air back, generating forward thrust." (10:58 - 11:04). These statements accept "the ground moving underneath the car" as a given, with no acknowledgement that the wind is the ultimate source of power causing the movement, and no explanation is offered how the car continues to extract power from the wind when the car is at or exceeding wind speed. In the real world, the Blackbird car is not sitting on a motorized treadmill, nor is it being pushed from behind with a long pole.

In the previous thread on the subject, I hypothesized that the collision of the tailwind air mass with propeller driven rearward moving air mass would compress the air immediately aft of the rotating propeller. The force required for this compression would extract power from the tailwind, and the resulting pressure differential between the air aft of the propeller and the air forward of the propeller would exert a force on the wide blades, causing them to act as sails, and providing forward thrust. As speed relative to the ground increases, so does the speed of the propeller rotation, so the zone of compressed air aft of the blades caused by the two moving opposing air masses will not dissipate and the car can continue to extract power from the wind as it accelerates beyond wind speed, until thrust balances drag.

I suggest that this proposed explanation, whether correct or not, at least acknowledges that the fundamental source of power is the wind, not the ground moving backwards beneath the vehicle.

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#23
In reply to #22

Re: A Follow up on the Faster Than Wind Cart

07/03/2021 7:39 PM

This is the way I understand it...

From #21:

"Stand on the ground beside a bicycle that faces right and has its pedal at the 6 o'clock position. Push the pedal left (clockwise). Which way will the bike move? Most people will answer that the bike moves forward as the pedal moves clockwise toward 7 o'clock. But, in fact, the bike moves backward and the pedal moves counterclockwise toward 5 o'clock. It is very easy to set this up with a real bicycle and the effect never fails to surprise. "

Analogous to the example in #21, your hand pushing on the petal is the wind pushing on the fan blades. Like the bicycle, the wheels and blades (pedals) are chained together. The blades turn in the opposite direction as you would expect, just as the bicycle pedal does. It is because there are two forces acting on the pedal and fan blades, i.e., your hand (wind) and the force from the wheels via the chain.

When you push backward on the bottom pedal, the bicycle moves to your left faster than your hand is moving to the left, i.e., downwind faster than the wind.

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#24
In reply to #23

Re: A Follow up on the Faster Than Wind Cart

07/03/2021 9:02 PM

But when the car reaches wind speed and above, the wind cannot reach the fan, cannot exert any force on the fan, and the effect you describe therefore cannot occur. Clearly though, the car does continue to extract power from the wind when it equals and exceeds wind speed. I suggest that although the wind has been left behind, it is still able create, in concert with the rearward air flow from the fan, a high pressure zone aft of the fan blades. The car cannot outrun this high pressure zone, and thrust is thereby maintained.

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#25
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Re: A Follow up on the Faster Than Wind Cart

07/04/2021 9:11 AM

You are right, as the car reaches wind speed, the tailwind can't reach the fan, but it can blow against the slipstream behind the fan resulting in a higher pressure. Also, ahead of the fan there is no headwind or less headwind as the car moves even faster. The difference in pressure between the front and back of the fan provide the thrust, and even when the car is moving faster than the wind, the tailwind increases this difference.

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#26
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Re: A Follow up on the Faster Than Wind Cart

07/04/2021 9:54 AM

It seems then, that we are in complete agreement.

I will add an observation regarding the toy car in the video that Derek propels across the floor with the long board: All of the rotating elements rotate in planes parallel to direction of applied force and the direction of the toy car's movement. In the Blackbird car the fan blades rotate in a plane perpendicular to the direction of applied force and the direction of the car's movement. In the toy car the top large wheel (presented as analogous to the Blackbird fan) rotates at the point of contact with the board towards the applied force - analogously, rotates into the wind, so as the toy car moves downwind, the "fan" will not outrun the tailwind. But on the Blackbird car, the fan rotates perpendicular to the wind, so when the car reaches wind speed, it and the fan will have outrun the tailwind - and something else must be happening to provide and sustain thrust. That something else, you agree, must be a fore and aft pressure differential. There is no suggestion of this in Derek's explanation in the video. The professor should ask for the return of his $10,000.

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#27
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Re: A Follow up on the Faster Than Wind Cart

07/04/2021 9:37 PM

I will also add that, regarding the toy car's acceleration on the treadmill, I do not share Xyla's amazement, Derek's delight, or the good professor's skepticism. I think they are all a bit daft. The toy car's wheels are being driven by the moving treadmill belt, which itself is being driven by the powerful treadmill motor. Note that Xyla holds the toy car in place until the propeller winds up to speed, then releases it. With different gearing the propeller could be driven at say, 5000 rpm. Then, still holding the car in place until the prop winds up to that speed, and then releasing it, the toy car would blast off the front end of the treadmill, probably becoming airborne. But so what? With respect to the real world performance of the Blackbird wind driven vehicle, the toy car on the treadmill demonstration proves nothing.

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#28
In reply to #26

Re: A Follow up on the Faster Than Wind Cart

07/04/2021 11:03 PM

I don't agree that the professor should be reimbursed. He fell for a sucker bet. (I too might have fallen for it I had the money.)

The gust criticism was unwarranted; that could be fixed simply by doing the demo on a non-gusty day. The wind speed gradient issue has a little more merit, but that too is easily fixed by multiple telltales at various heights. If the asserted ground speed were only, say, 1.05 x wind speed, that could be chalked up to measurement error. But not a 2+ x wind speed scenario. Something else is going on that is not yet accounted for.

The video can be faulted for being a poor technical write-up. Important missing details include wheel size and rpm; propeller size, pitch angle and direction , and rpm; drive connection between prop and wheel shafts, and prop rotation direction. Of course, those details would give away the game. This lack of detail is just like what an over-unity scammer might do. Jazzing up things with a bet, and providing a visual distraction, fit right in with that idea.

However, directing the bet proceeds to an educational endeavor somewhat excuses the scientific obscurity.

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#29
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Re: A Follow up on the Faster Than Wind Cart

07/05/2021 8:39 AM

Further to my debunking of the treadmill demonstration: Holding the toy car in place on the treadmill until the propeller winds up to speed nullifies the claim that the treadmill set-up replicates the Blackbird car's frame of reference when Blackbird is moving at wind speed. As Derek says, from the car's frame of reference the car is sitting in still air and the ground is moving backwards at wind speed. Let us assume that speed is 25kph, and that therefore, in the toy car demonstration, the treadmill speed is set at 25kph. Holding the toy car in place is equivalent (equal and opposite force) to a 25kph tailwind still hitting the car while the car is moving at 25kph before a 25kph tailwind. In the real world, this does not occur.

The effect of holding the toy car in place on the treadmill until the propeller winds up to speed then releasing it, is to replicate, in this example, the Blackbird car moving at 25kph in a 50kph tailwind. I submit that this is the reason the toy car accelerates when released.

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#30
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Re: A Follow up on the Faster Than Wind Cart

07/05/2021 12:26 PM

"Holding the toy car in place is equivalent (equal and opposite force) to a 25kph tailwind still hitting the car while the car is moving at 25kph before a 25kph tailwind. In the real world, this does not occur."

NO! As the toy car's wheels and propeller got up to speed, Zyla had to exert less and less forward push on the car, until somewhere near full speed she had to switch from pushing forward to restraining it. Then when she removed the restraining force, the inertia of the car and propellers produced enough thrust to cause the car to accelerate forward.

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#31
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Re: A Follow up on the Faster Than Wind Cart

07/05/2021 3:39 PM

I see what you are saying. So, is it just inertia that causes the toy car to accelerate forward? If the treadmill were a mile long would the little car continue to accelerate for the entire length? If that is the case then let's eliminate the treadmill. Give the toy car an initial push on a smooth surface on a windless day and we can watch it accelerate to the horizon.

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#32
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Re: A Follow up on the Faster Than Wind Cart

07/05/2021 8:32 PM

NO again! Acceleration requires a force, a source of energy. In the real car, that source of force/energy is the wind; for the toy car, the source is the treadmill. Take away the source of energy, and the acceleration will soon fall to zero, and then become negative (a deceleration).

Note that, supposing we had a very long treadmill and a car that could go straight enough to stay on it, the acceleration would not remain constant. As the speed of the car increases, so do the drag forces, without a proportional increase in propelling forces. The car will continue to move faster than the belt, but as it moves faster and faster, there will definitely be a point at which the drag forces equal the propelling forces. Beyond that point the acceleration will remain zero, and the speed will become a constant, at some value higher than the speed of the belt. How much higher, I have only the slightest idea.

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#33
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Re: A Follow up on the Faster Than Wind Cart

07/06/2021 8:19 AM

Sticking with the treadmill demonstration: If the car is accelerating then it has outrun the treadmill belt. The force/energy at the toy car's wheels required for that acceleration must therefore come from the wind. But there is no wind.

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#34
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Re: A Follow up on the Faster Than Wind Cart

07/06/2021 10:56 AM

Just before the car is released, the wheels are no longer slipping on the treadmill (as they were until the propeller reached full speed). The treadmill is moving with a constant speed, so the acceleration of the car is zero, and a restraining force (Zyla's hand) must be applied to prevent acceleration.

At release, the fan is blowing air toward the rear of the car. The reaction to the force of the fan blowing the air towards the rear is an equal and opposite force of the air pushing forward on the fan. That forward force must be greater than the rearward force exerted by the treadmill on the car's wheels, in order for the car to accelerate as it does. This can only occur if all the factors, such as wheel diameter, gear ratio, bearing friction, blade diameter, and blade pitch are appropriate.

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#35
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Re: A Follow up on the Faster Than Wind Cart

07/06/2021 11:41 AM

I think a lot of people miss the point that it is the differential speed of the wind and the ground that provides the driving force. That is equivalent to the differential speed between the treadmill belt and the wind.

I think you could also extrapolate to a water fall - you have no problem visualizing a water fall being able to generate electricity to pump water that could pump some of the water back up above the falls - but only a portion can be pumped back up, not all of the water used. In the same way the cart can run "faster" than the wind until the point the energy losses match the differential energy and losses of the relative wind velocity.

Or, consider a windmill - they generate power, that could be used to have something use a portion of that energy to run another (smaller) fan to blow wind in any direction desired. There is still an energy balance that occurs.

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#36
In reply to #35

Re: A Follow up on the Faster Than Wind Cart

07/06/2021 11:50 AM

I pointed that out(-ish) in #16, but I think people blew past it.

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#37
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Re: A Follow up on the Faster Than Wind Cart

07/06/2021 1:09 PM

Assuming no losses, Power in at the wheels from the treadmill will equal Power out at the fan. However the various elements are tweaked there cannot be more Power out at the fan than is being put in by the treadmill. Surely you must sense that there is something fishy going on. It is a free energy demonstration. I stated in an earlier post that the force applied by Xyla to hold the car in place until it winds up to speed is equivalent to her providing the non-existent wind force necessary for acceleration. Did this store sufficient inertia for the short acceleration to the front of the treadmill? It seems unlikely, but I wonder. Or is there a silent Dyson fan out of the camera frame - the concealed energy source for the perpetual motion machine?

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#39
In reply to #37

Re: A Follow up on the Faster Than Wind Cart

07/06/2021 5:17 PM

Of course there are losses between the power in at the wheels and the power out at the fan, so the power out at the fan must be less than the power in at the wheels. BUT, remember that, in the absence of friction (which includes drag forces), zero power is required to continue moving at constant velocity.

By keeping the weight low, using good bearings and moving parts, and minimizing aerodynamic drag, the friction losses can be made small. Then only a portion of the power available at the blades is used in overcoming friction and drag. Whatever blade power is greater than the friction and drag power must accelerate the car.

Again, as the car goes faster, the drag forces increase exponentially, while the blade forces increase more linearly, so there will be a point where they become equal, and the car will cease to accelerate.

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#38
In reply to #33

Re: A Follow up on the Faster Than Wind Cart

07/06/2021 4:24 PM

If the car is accelerating then it has outrun the treadmill belt. The force/energy at the toy car's wheels required for that acceleration must therefore come from the wind. But there is no wind.

The acceleration is due to thrust from the spinning fan, which is connected to the wheels. It generates thrust by accelerating the air.

Here is one way to look at it:

Put a sail on the cart and the wind cannot push the cart faster than the wind speed. But a fan is like a moving sail. A laser beam shined into the fan would show how the blade surface moves toward the back of the cart as the fan turns and the blades pass by. The cart may be moving downwind faster than the wind, but the fan blades are not.

And since the fan is connected to the wheels, the faster the cart goes, the faster the fan turns. The driving force is the difference in speed between the air mass and the surface the wheels are rolling on. It makes no difference what the frame of reference is.

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#40
In reply to #38

Re: A Follow up on the Faster Than Wind Cart

07/07/2021 8:24 AM

"A laser beam shined into the fan would show how the blade surface moves toward the back of the cart as the fan turns and the blades pass by. The cart may be moving downwind faster than the wind, but the fan blades are not."

Thanks. That makes complete sense to me.

I watched an old video by Rick Cavallaro, one of the designers/builders of the Blackbird. In the video he also demonstrates a toy car on a treadmill. He shows it accelerating, pans the camera around the room to show there are no fans providing a wind force, shows a level on the treadmill... He said in a later video that he built the full size car because even with the evidence of the toy car/treadmill demonstration, most of his colleagues were not convinced that downwind faster than the wind is possible. It is counter intuitive. It seems to be a lift-yourself-by-your-own-bootstraps scenario.

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#41
In reply to #40

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 6:26 AM

So why not make cars or ships that use the same principle?

A small motor to get going,then ---Walla! Magic!

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#42
In reply to #41

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 8:10 AM

Your question is essentially the same as the question I asked in my post #31: Why not eliminate the treadmill and simply give the toy car an initial push on a smooth surface on a windless day and we can watch it accelerate to the horizon. So it should be clear that, like you, I have had difficulty understanding and accepting what I see with my own eyes in the videos. You and I are in good company in our struggle to understand and accept this concept. Direct your question to those here who claim no such cognitive struggle. Direct your question to those here who state that it is obvious what is going on with the Blackbird car.

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#50
In reply to #42

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 3:08 PM

It's a force multiplier, if you remove the force there's nothing to multiply...basically it's a rolling lever...

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#52
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Re: A Follow up on the Faster Than Wind Cart

07/08/2021 8:27 PM

My bicycle is a force multiplier and a rolling lever, and if I don't pedal it, it won't go. If it were as simple as that Rick Cavallaro's engineering colleagues would not have scoffed at his idea of a wind driven cart that could move downwind faster than the wind, and a physics professor would not have bet $10,000 that it was not possible, even after it was built.

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#43
In reply to #41

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 9:56 AM

I don't think the operation of the downwind cart is obvious to anyone. It's completely counterintuitive, which makes it interesting.

It requires relative motion between the surface and the air. It makes no difference if the surface is moving (treadmill) and the air is stationary, or if the surface is stationary and the wind is blowing.

Obviously, with a sail on the cart, you cannot go downwind faster than the wind. The output cannot be more than the input, i.e., input --> output.

Replace the sail with a fan driven by the wheels blowing backward, and now the wind adds to the speed of the cart, i.e., input + output --> output.

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#45
In reply to #43

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 12:31 PM

So what happens if you push the cart on a windless day fast enough to get the prop turning?

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#46
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Re: A Follow up on the Faster Than Wind Cart

07/08/2021 12:48 PM

So what happens if you push the cart on a windless day fast enough to get the prop turning?

It will coast to a stop.

There has to be motion between the air and the ground to give the cart energy.

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#48
In reply to #46

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 12:55 PM

So if the wind goes to zero,the cart will coast to a stop?

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#49
In reply to #48

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 1:06 PM

Now that should indeed be intuitive!

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#47
In reply to #43

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 12:49 PM

Quantum computing is REALLY counterintuitive,but it works.

Check this out:

A quantum computer solves a problem without even running:

https://www.sciencedaily.com/releases/2006/02/060223084147.htm

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#51
In reply to #47

Re: A Follow up on the Faster Than Wind Cart

07/08/2021 7:24 PM

If you want to talk about quantum, please check your intuition at the door...

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#53
In reply to #51

Re: A Follow up on the Faster Than Wind Cart

07/10/2021 10:29 AM

Also check your thinking cap,and your logic and common sense.

It goes over the edge of reality.

"Beyond here there be dragons."

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#56
In reply to #53

Re: A Follow up on the Faster Than Wind Cart

07/11/2021 9:28 AM

It's just a simple feedback loop. What is there not to understand?

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#44
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Re: A Follow up on the Faster Than Wind Cart

07/08/2021 11:45 AM

What fraction of the time does a car or ship need to go in the same direction as the wind? What fraction of the time does a car or ship need to go a bit faster than the wind?

I commonly drive just under hurricane wind speeds (low 70's)

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#54

Re: A Follow up on the Faster Than Wind Cart

07/10/2021 12:15 PM

After digesting all that I have read here,and a few belches,I understand what is happening.The speed exceeds the wind speed by the same speed as the car would achieve if it had a motor turning the prop at the same speed, on a still day.The speed of the wind simply adds to this speed.

If the car with a motor turning the same prop could achieve 10 mph with no wind,then a tail wind of 5 mph would increase it's speed,relative to the ground by 5 mph.

If the tail wind stopped,it would coast down to 10mph.

If the motor stopped,it would stop.

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#55
In reply to #54

Re: A Follow up on the Faster Than Wind Cart

07/10/2021 3:51 PM

There are WAY too many variables for it to be that simple. Think about the various factors that cause losses.

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#57
In reply to #55

Re: A Follow up on the Faster Than Wind Cart

07/11/2021 3:24 PM

Consider the above scenario with a airplane:Wind speed vs ground speed.

With and without a tailwind.

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#58
In reply to #57

Re: A Follow up on the Faster Than Wind Cart

07/12/2021 12:17 PM

This appears to be a repeatable experiment.... Doubters should try their own experiment in the scientific mind set.

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#59
In reply to #58

Re: A Follow up on the Faster Than Wind Cart

07/12/2021 6:54 PM

True, anyone with the requisite skills could build a vehicle identical to Rick Cavallaro's Blackbird. If it were to go downwind faster than the wind (which I suspect it would) the repeat experimenter would have confirmed what the original cart did, but not why it did what it did. That the cart went faster downwind than the wind (2.8 times faster!) is a troublesome reality for most, even for those educated in the physical sciences. The explanations proffered here and elsewhere satisfy some but not everyone. How would repeating the experiment change that? Analogously, dropping a rock a dozen times shows beyond doubt what gravity does, but it does not explain why it does what it does. Seeking an explanation does not make one a doubter of gravity.

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#60
In reply to #59

Re: A Follow up on the Faster Than Wind Cart

07/12/2021 8:41 PM

Personally I am a believer - if the wind is blowing across the ground we can extract energy, how we use it is what is novel - so we decide to travel down wind, or pump water, or make electricity - great! As long as the available energy exceeds the losses - we win. When the losses exceed the input power we grind to a halt.

I see two arguments -

1) How does that work?

2)Incorrigible naysayers - those are the ones I think need to "put their money where their mouth is".

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#61
In reply to #60

Re: A Follow up on the Faster Than Wind Cart

07/12/2021 9:28 PM

Seems reasonable. Those in the #2 camp, the incorrigible naysayers, should pool their resources and build a Blackbird II. Then, if it works, they can join the #1 camp and perhaps add fresh insight to why it works. Of course, if it doesn't work, they get "I told you so!" naysaying bragging rights.

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#62
In reply to #61

Re: A Follow up on the Faster Than Wind Cart

07/12/2021 10:01 PM

"if it doesn't work, they get "I told you so!" naysaying bragging rights."

Not necessarily. Unless they get the friction down, the powertrain right, the sizes right, and the pitch/design of the blades right, it probably won't work. It could take a lot of experimentation and adjusting to make it work.

It only takes one correctly done experiment to prove that something does work, but no amount of failed experiments can prove that it can't ever work.

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#65
In reply to #62

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 9:46 AM

Rick Cavallarro stated that originally the Blackbird cart was not equipped with a variable pitch prop - and it still went faster than the wind. The addition of variable pitch blades enabled the later 2.8 X windspeed. Certainly blade diameter and gearing is critical, but not difficult to get that right - just copy the Blackbird specs. Standard off-the-shelf bicycle chain was used in the drive train, and if there was anything special about the wheel and prop bearings surely Cavallarro would have mentioned it. Structurally, it is a simple device, and according to the designer/builder only blade pitch fine tuning was necessary to achieve the record 2.8 X windspeed. Even an unrefined embodiment of the idea managed to slightly exceed windspeed and thereby proved the concept. Therefore, if all this is true, a naysayer's repeat of the experiment would not be as open to surreptitious fudging of details as you suggest.

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#67
In reply to #65

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 10:50 AM

I definitely did NOT suggest anything surreptitious, and making adjustments to improve performance does not fit my concept of "fudging".

Hiding a battery and motor, or any other source of energy not related to the wind, somewhere in the vehicle would be fudging.

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#68
In reply to #67

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 11:07 AM

Exactly WHERE in my post did I say to hide the motor?

I merely suggested it as a means to get the prop up-to-speed.

The REMOVING (or DISENGAGING) the power source,mechanical,electrical,mules,horses,windmill,water wheel,solar etc.(Your choice.)

The motor could be EXTERNAL to do this for all that matters.

I thought I made that very clear,but if you need further explaining,I will do so.

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#69
In reply to #68

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 11:34 AM

I was not referring to ANY of your posts. I was simply refuting CSW's statement: "... a naysayer's repeat of the experiment would not be as open to surreptitious fudging of details as you suggest." (Underlining added for clarity), and clarifying my understanding of the term "fudging" (closest to definition #2 in the Apple/Oxford English dictionary), by giving a possible example.

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#71
In reply to #69

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 4:56 PM

Sorry! My bad.I misread the "In reply to".

Gotta watch out for that bifocal zone!Sheeez.

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#70
In reply to #67

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 12:23 PM

According to the designer/builder it did not take, as you state, "a lot of experimenting and adjusting to make it work", therefore, if indeed it did work, an incorrigible naysayer's repeat of the experiment would also not require a lot of experimenting and adjusting to make it work. I trust you find this revision acceptable. I have fine tuned my post to assuage your sensitivities. If Rick Cavallarro is being truthful, the downwind cart is far less sensitive than you, and it would be a simple matter for an incorrigible naysayer to build a downwind cart that would achieve a slightly higher than windspeed and prove the concept.

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#63
In reply to #61

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 12:20 AM

And because they are incorrigible naysayers they will not take the effort to do a proper experiment, It is destrined to fail.

(Someone needs to pattern Xyla's model and demonstrate it in a wind -`just to remove all doubts about the relative frame of reference.

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#72
In reply to #63

Re: A Follow up on the Faster Than Wind Cart

07/14/2021 8:55 AM

Copy the wheel size, the gear ratio, the prop diameter, and the blade pitch of the original fixed-pitch Blackbird cart. That is all that is required to repeat the experiment. It is just simple mechanics - on which an experimenter's personal bias can have no influence. Whether the builders are true believers or hard core skeptics, it will either go faster than the wind or it won't. A phrase I coined years ago is apt: A machine will never lie to you.

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#64

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 5:31 AM

I can understand it if the wind is variable in velocity.The momentum of the blades and the vehicle will allow it to coast through the slower pulses of wind,and temporarily achieve faster than wind speed.

Could you disengage the wheels,use a motor to speed up the prop,the turn off the motor,engage the wheels,how far would the vehicle travel with the motor off and no wind?

What you would have is a form of a flywheel battery,but not over-unity.

If this would work,we could have some very cheap transportation.

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#66
In reply to #64

Re: A Follow up on the Faster Than Wind Cart

07/13/2021 10:27 AM

Reportedly, for the Blackbird measured downwind speed tests, the cart was pushed by a motorized vehicle until up to wind speed, then released (identical to holding the toy car on the treadmill until it matched the treadmill speed). Cavallarro said that it could accelerate from a dead stop, but took a long time and used up a lot of track space, so for the official speed tests they gave it an initial push. I understand the moving sail concept explained in this thread by Rixter and by others elsewhere, and I understand how this could push the cart slightly faster than downwind. But 2.8 X windspeed!? Then the cart is pushing through a strong headwind. What is happening then?

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#73

Re: A Follow up on the Faster Than Wind Cart

07/15/2021 7:26 PM

Just following some general comments, but anybody for roadside wind turbines ? I must be missing something - driving vehicles to power wind turbines ? Surely that's some kind of April Fool's suggestion.

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#74
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Re: A Follow up on the Faster Than Wind Cart

07/16/2021 7:29 AM

No joke.Wind is always present in the median,as vehicles pass by.It will be there whether or not you harvest it.

The turbines simply take advantage of the energy lost by vehicles as they push through the air,as well as the updraft created by the hot pavement.

There are actually wind vortices enhanced by vehicles passing in opposite directions.

I think this is a very good idea,and should be implemented widely.

It could power lighted billboards,highway lights,yellow lighted lane lights in fog,early warning sighs for traffic congestion and or bad weather.

And lots of other applications too numerous to mention.

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#75
In reply to #73

Re: A Follow up on the Faster Than Wind Cart

07/16/2021 4:48 PM

Diminishing returns. A wind farm propeller can have a diameter over 240 ft. with tip above 380 ft.

Turbulence from a vehicle is nothing in comparison. I doubt you could charge your cell phone.

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