Down wind faster than the wind

[humber]

1. Tell any non-believers they "no nothing about science"
2. If they persist, "nothing about physics"
3. Up a level, "nothing about math" ( Math is the bestest of the sciences)
4. Back to basics, "nothing about the real world"

ETA:
The cart is on a treadmill in a truck moving downwind at windspeed. The model agrees.

What would indicate a failure of that model, and how would you explain it?

I can do the math gentleman, if I couldn't, I could find a simple simulator.

But can you answer my question?

 

[H'ethetheth]

I haven't. But I should. I could go with smaller wheels, higher prop pitch, or both.

Let me know how that works out, or better yet: see.

 

[GreyICE]

He's not using high school physics but the world view from over 400 years ago before Newton. When humber shows that he can actually apply physics and use the math to solve problems I'll take him off ignore and try to help with any remaining misunderstandings. In the mean time, I'd appreciate it if you didn't continue to pollute this thread by quoting his gibberish.

It looks like a simplified Newtonian Physics, which is more or less High School (non-honors) level. The fact that it is simple Newtonian Physics poorly applied and wrong simply means he didn't learn much in the class. The diagrams are straight out of textbooks.

 

[sol invictus]

It looks like a simplified Newtonian Physics, which is more or less High School (non-honors) level. The fact that it is simple Newtonian Physics poorly applied and wrong simply means he didn't learn much in the class. The diagrams are straight out of textbooks.

It's not Newtonian physics. It's wrong pre-Newtonian physics (and even pre-Newton many people wouldn't have made this mistake).

Newton's laws are invariant under Galilean boosts (i.e. shifts in reference frame) - that's why the treadmill is equivalent to a steady wind, why it's totally meaningless to try to decide which object involved in a collision in space is at rest, etc. Humber obviously doesn't understand this concept, which means s/he doesn't understand basic Newtonian dynamics.

But it goes beyond that - it requires truly mind-numbing stupidity not to recognize that the chain-crawler Myriad posted earlier will crawl down-chain faster than the chain. You don't need any equations to see that - just common sense. And once you recognize that the bottom drops out of any basis for objecting to this thing (being generous and assuming one ever existed in the first place).

 

[Brian-M]

I don't need to, Micheal C. The average velocity of the hand must be that of the cart, or it would accelerate away and leave the hand.
It is possible to move the device, while simultaneously pushing the hand back and forth, in oscillation, so that the journey of the hand will have a longer displacement, but the average would still be that of the cart.

He is playing a trick, by operating his hand in a similar way as the cart extends itself, but the movements are small, so you don't notice.
The integral of the applied force, will be that required to accelerate a simple skateboard, of the same mass and frictional load, to the same velocity.

Humber, with all due respect, the cart you're talking about was posted in this thread because it was effectively the same as the animated one I posted. You'll find the explanation and math behind it back in post 925. You even quoted that post, so you should be aware of it.

Have you found any flaw in the math or logic that I'm not aware of?

 

[humber]

It's not Newtonian physics. It's wrong pre-Newtonian physics (and even pre-Newton many people wouldn't have made this mistake).

Newton's laws are invariant under Galilean boosts (i.e. shifts in reference frame) - that's why the treadmill is equivalent to a steady wind, why it's totally meaningless to try to decide which object involved in a collision in space is at rest, etc. Humber obviously doesn't understand this concept, which means s/he doesn't understand basic Newtonian dynamics.

But it goes beyond that - it requires truly mind-numbing stupidity not to recognize that the chain-crawler Myriad posted earlier will crawl down-chain faster than the chain. You don't need any equations to see that - just common sense. And once you recognize that the bottom drops out of any basis for objecting to this thing (being generous and assuming one ever existed in the first place).

Well, from the way you three talk, I would assume you were still in school.

Can you give me answer to the question, please?

 

[Brian-M]

Roadside observer and driver may claim to have "equivalent relative velocities", but that does not mean that the driver can insist that his
velocity is zero, and the ground is moving beneath at 60mph, because the car would have to be capable of rotating the entire planet.

"Equivalancy" means that the car is bound to the Earth, by the same means and forces, as the Earth is bound to the car. Our participants will
also agree that the Earth is a planet, a car is car, and that a road is not a treadmill.

"Two things may be relative to each other but common to a third, and at the same time"

Practically though, the problem is not about "frames of reference" but of the accuracy and completeness of the model.

Who can argue with logic like that? I can't, because I have no idea what you're trying to say. So, instead of trying to explain my understanding to you, I'm going to ask you to explain your understanding to me.

Let's go back to the car and skateboarder example for this.

We'll assume that in both situations the car's velocity is unaffected by the impact. (The moving car's engine is capable of instantly compensating for a sudden change in load, and the parked car has a very good hand-brake.)

Let's say the skateboarder weighs 100 pounds, the car weighs 2000 pounds, and the collision is non-elastic.

Using the formula for kinetic energy; E = (M/2)(V^2), it looks to me like...

The kinetic energy imparted to a stationary skateboarder weighing 100 pounds from a car moving at 60 mph would be: E=(100/2)(60^2)

The kinetic energy imparted from a stationary car to a skateboarder moving at 60 mph, and weighing 100 pounds would be: E=(100/2)(60^2)

Clearly, if you're right about the two situations being different, the outcomes should be different; but no matter how hard I look, I just can't find a difference.

So please, explain to me where this difference is, show me how I can apply the formulas to find out what the difference should be myself, and tell me exactly how much kinetic energy is really imparted from the car to the skateboarder in each case.

 

[humber]

Humber, with all due respect, the cart you're talking about was posted in this thread because it was effectively the same as the animated one I posted. You'll find the explanation and math behind it back in post 925. You even quoted that post, so you should be aware of it.

Have you found any flaw in the math or logic that I'm not aware of?

Brian-M,
I did take a look. The speed will be doubled, but so will the force. The differential velocity of the top and bottom wheels results in a speed ratio of two. That is clear from the ratio of the two gray gears.
The top wheel and gears as a set are 2:1, so doubling the force, but the ratio of the lower wheel and gear set is 1:4, so the product is 2. The forces act in series through the belt; the other wheel can be thought of as an idler.

The problem with the other cart is that it will eventually reach the speed of the source. Instead of pushing, pull it. Place the wheels at the rear of the board. As you move, the wheels will move forward. So, now what do you do? Reset, and continue. If you make a longer board, then it will only extend the time between resets, or when it catches up to you and assumes your velocity. The deception concerns the amount of force. That is disguised, so what is actually an increase in acceleration, looks like velocity over the short term.

But I think that you can always assume that Newton will catch up. If the force is the same, and you overcome the problem of attaching a continuous force to the board/wheels, then it will not show any increase over the non-geared version. All other things being equal, I think these two carts will reach the same velocity, in the same time.

 

[Brian-M]

Brian-M,
I did take a look. The speed will be doubled, but so will the force. The differential velocity of the top and bottom wheels results in a speed ratio of two. That is clear from the ratio of the two gray gears.
The top wheel and gears as a set are 2:1, so doubling the force, but the ratio of the lower wheel and gear set is 1:4, so the product is 2. The forces act in series through the belt; the other wheel can be thought of as an idler.

The problem with the other cart is that it will eventually reach the speed of the source. Instead of pushing, pull it. Place the wheels at the rear of the board. As you move, the wheels will move forward. So, now what do you do? Reset, and continue. If you make a longer board, then it will only extend the time between resets, or when it catches up to you and assumes your velocity. The deception concerns the amount of force. That is disguised, so what is actually an increase in acceleration, looks like velocity over the short term.

The cart will travel at twice the speed, and it will require greater force to push. That's not in question.

The question is, will it consistently travel faster than the medium pushing it?
(In other words, will it move faster than the board pushing it, at least until you run out of length on the board?)

 

[spork]

This is beginning to remind me of the clever way the mice study the scientists reactions based on the paths they choose to follow through the maze.

 

[ynot]

This is beginning to remind me of the clever way the mice study the scientists reactions based on the paths they choose to follow through the maze.

SPORK - What’s your wheel turn to propeller turn ratio? Nearly through the maze. Film at 11:00

 

[Michael C]

SPORK - What’s your wheel turn to propeller turn ratio?

- - -​

The gear ratio between the axle and prop shaft is 1:1.

 

[spork]

SPORK - What’s your wheel turn to propeller turn ratio? Nearly through the maze. Film at 11:00

Ynot, the maze comment was not aimed at you. It was aimed at all of us that continue to try and straighten humber out. We think we're trying to help, but the fact is that he has us dancing like puppets to try and fix the unfixable.


So... the prop and axle are geared 1 to 1. We use the tail drive from an R/C heli for that drive. JB bought the tail-drive from a T-Rex 500 and I bought only the gears and milled the "gearbox" out of delrin.

That being said, the gear ratio is not really the important thing. What is important is the advance ratio. You want to make sure that the theoretical distance the prop advances through still air in a single rotation is less than the wheels advance in that same single rotation of the prop. You can do this through prop-pitch, gearing, wheel size or any combination thereof.

The advance ratio on my cart is: 7 / 14.5 This comes from using a 14" diameter prop with a 7" pitch (that's the 7) and wheels with a 14.5" circumference (that's the 14.5)

I should warn you ahead of time that it will almost certainly take a bit of tweaking before this thing takes off on the treadmill. I finished mine yesterday, and was surprised that it didn't perform as well as the first one. But with a little tweaking and alignment it's kicking butt now. You need to make it turn smooth as silk with absolutely minimum drag. Depending on your wheels they may initially slip on the treadmill. We spray our gears with a silicone lubricant. If you have sealed bearings you may need to open them and remove the grease. You'll probably struggle with the steering a bit before it'll stay on the treadmill even long enough to tell it's working.

I really hope you get it built and tested, and use a bit of patience if necessary to make it perform properly. Please take videos and post them. There's nothing like a converted skeptic to help the cause.

 

[humber]

The cart will travel at twice the speed, and it will require greater force to push. That's not in question.

The question is, will it consistently travel faster than the medium pushing it?
(In other words, will it move faster than the board pushing it, at least until you run out of length on the board?)

I got the idea from your post #925 that the force was half of that for a normal cart, Fc =Ft/2?.

Anyway, it seems that you agree. The answer to your above question would be, yes,
Such devices are centuries old, and as I have said, they can be seen at work in looms for example. I have seen a sorting machine that uses a similar idea to eject items from a moving conveyor. (The ejector moves forward with the item, rather than being ejected from the sides).

If you built such a machine, it would need twice the force, so there would be no advantage.
I expect you know that, and think that there is a way of reducing the force, as you appear to have done in #925?

ETA:
Do you agree that the carts shown are equivalent?

Spork,
I will get back to you mice later. But, where is the cheese? Can you please give me an answer to my question at #1101?

 

[Michael C]

If you built such a machine, it would need twice the force, so there would be no advantage.

There would be no force gained, yes. But that's not the point of the machine. Any machine will trade speed with force: in a low gear, a bicycle produces a lot of force bit not much speed, enabling you to climb a hill slowly, or in a fast gear it produces less force and more speed, enabling you to go fast on a flat road.

Spork's cart, Brian-M's cart and all the other devices presented here do not propose to give an advantage in force: they will all need a greater force to push them than the force with which they could push something. They propose to give an increase in speed, at the cost of a decrease in force.

The "speed of the wind" is not itself a force. It is the kinetic energy of the wind that provides the motive force for the cart. Kinetic energy is proportional to mass. The force gained from the wind comes from the mass of air hitting the propeller. You can gain more force from the same wind by increasing the size of the propeller.

 

[humber]

There would be no force gained, yes. But that's not the point of the machine. Any machine will trade speed with force: in a low gear, a bicycle produces a lot of force bit not much speed, enabling you to climb a hill slowly, or in a fast gear it produces less force and more speed, enabling you to go fast on a flat road.

Yes, that is transformation.

Spork's cart, Brian-M's cart and all the other devices presented here do not propose to give an advantage in force: they will all need a greater force to push them than the force with which they could push something. They propose to give an increase in speed, at the cost of a decrease in force.

That is the problem. You need more power from exactly the same source. Brian-M's device indicates you DO need more force.
There is an error that leads to the conclusion that F = Fc/2. (#925)

The ratio of the gray gears demands that F = Fc, meaning twice the force of a standard cart, for twice the velocity. The second ground wheel can be made idle, just somewhere for the belt to go, so think of how much power the remaining ground wheel consumes, and how much the upper wheel must supply. That ground wheel is greedy!

The "speed of the wind" is not itself a force. It is the kinetic energy of the wind that provides the motive force for the cart. Kinetic energy is proportional to mass. The force gained from the wind comes from the mass of air hitting the propeller. You can gain more force from the same wind by increasing the size of the propeller.

[/QUOTE]

Agreed, though you can find posts where the two are equated.
Gathering momentum from the wind is largely what sailing boats do. They extract more power, so that it may be transformed by various means. They are sophisticated machines that have been developed to do just that, and use lift to reduce the drag of the hull, for example.
Direct comparison with the cart is unfounded, because as you note, it can only gather what impinges upon the propeller, imaginary sliding booms or not. A bigger propeller may mean more power, but the forces generated will be opposed. More power is more speed, but that only extends the terminal velocity as expected, which will still be below windspeed.

Just a note. Supporters are invariably upset when claims of deception are made. Sometimes the deception is deliberate, and sometimes it is the designer fooling himself. One of science's attributes, is that it helps control those errors. An 'honest' video would have at least shown the forces involved; a cheap spring force-gauge would have been sufficient, a simple grid behind the cart could show the relative velocities. Evidence need to be more than "look, it works".

 

[H'ethetheth]

Direct comparison with the cart is unfounded, because as you note, it can only gather what impinges upon the propeller, imaginary sliding booms or not. A bigger propeller may mean more power, but the forces generated will be opposed. More power is more speed, but that only extends the terminal velocity as expected, which will still be below windspeed.

Just a note. Supporters are invariably upset when claims of deception are made. Sometimes the deception is deliberate, and sometimes it is the designer fooling himself. One of science's attributes, is that it helps control those errors. An 'honest' video would have at least shown the forces involved; a cheap spring force-gauge would have been sufficient, a simple grid behind the cart could show the relative velocities. Evidence need to be more than "look, it works".

An honest question for you, humber:
Do you agree that propellers can generate thrust in still air, when a torque is applied?

If not, you may have to read up on propeller driven aircraft.

If you do, on the other hand: this is exactly what the prop does on the cart at windspeed. It takes up torque from the wheels; not directly from the wind. At speeds below wind speed the propeller takes up cw torque from the wheels but ccw torque from the wind.

This designer is not fooling himself, or anyone nor is he trying.

 

[humber]

An honest question for you, humber:
Do you agree that propellers can generate thrust in still air, when a torque is applied?

If not, you may have to read up on propeller driven aircraft.

If you do, on the other hand: this is exactly what the prop does on the cart at windspeed. It takes up torque from the wheels; not directly from the wind. At speeds below wind speed the propeller takes up cw torque from the wheels but ccw torque from the wind.

This designer is not fooling himself, or anyone nor is he trying.

1. Yes.

2. I was referring to the double-speed skateboard device. If you are thinking of the treadmill, then one of the two options certainly applies. I have already made those reasons clear.

3. "At windspeed" assumes that it is already possible by the means given.
If so, please provide the evidence in a clear and unambiguous form.
'How' can come later.

The only source of energy is the wind. The wheels provide the reaction to the torque from the propeller or other motive forces.

ETA:
In that last remark of mine in the previous post, the claim was that bad practice leads to the effect of deception. You took up one cudgel, but not other, which indeed supports the meaning of the remark.
More pointedly, if you take the treadmill as evidence, then I think you are fooling yourself.
Once again, can you please answer the question posted at #1101.

 

[H'ethetheth]

3. "At windspeed" assumes that it is already possible by the means given. If so, please provide the evidence in a clear and unambiguous form.
'How' can come later.

The only source of energy is the wind. The wheels provide the reaction to the torque from the propeller or other motive forces.

Fair enough, I'll give it a try.

Okay, the cart is standing still, and the wind causes
(a) an aerodynamic force forward on the entire cart including the propeller. This force together with the friction between the tire and the ground creates a torque that wants to turn the wheels forward.

(b) an aerodynamic torque on the propeller that wants to turn the wheels backward.

Now the question is: Which torque is bigger?
If the prop is small enough and the wheels are big enough the propeller will lose. Therefore the cart will start rolling forward. As soon as this happens, two things follow:

(a) The cart has a forward velocity, which lessens the relative tailwind and therefore the countering torque on the propeller

(b) The prop starts spinning and therefore creating thrust, adding to the forward aerodynamic forces on the cart, and increasing acceleration.

This situation is true for all speeds below wind velocity, so the cart will reach wind velocity (QED).
At speeds higher than wind velocity there must be an equilibrium between thrust on one hand, and friction and drag forces on the other. Since thrust in non-zero at wind speed (as evidenced by the treadmill experiment), the equilibrium speed will be higher than wind speed.

My €0.02

ETA:
In that last remark of mine in the previous post, the claim was that bad practice leads to the effect of deception. You took up one cudgel, but not other, which indeed supports the meaning of the remark.
More pointedly, if you take the treadmill as evidence, then I think you are fooling yourself.
Once again, can you please answer the question posted at #1101.

I'm sorry, I cannot answer that question. I've only read pages 1-4, and the last two.

Also, I don't understand the question.

 

[Michael C]

Yes, that is transformation.

Transformation is exactly what Brian M's cart does: it transforms a force of Fc over a distance x into a force of Fc/2 over a distance of 2x. Nothing unusual there.

That is the problem. You need more power from exactly the same source.

What do you mean by that? Of course all the power is coming from one source. Indeed, most machines only have one source of energy. That doesn't stop them working.

Brian-M's device indicates you DO need more force.
There is an error that leads to the conclusion that F = Fc/2. (#925)

Can you point out this error and explain it? I don't see it in Brian's calculations.

The ratio of the gray gears demands that F = Fc, meaning twice the force of a standard cart, for twice the velocity.

No, the ratio of the gears does not demand that F = Fc. The cart works just like any other assemblage of gears. Why don't you make one and try it out?

Just a note. Supporters are invariably upset when claims of deception are made. Sometimes the deception is deliberate, and sometimes it is the designer fooling himself. One of science's attributes, is that it helps control those errors. An 'honest' video would have at least shown the forces involved; a cheap spring force-gauge would have been sufficient, a simple grid behind the cart could show the relative velocities. Evidence need to be more than "look, it works".

I'm not a "supporter", and I'm not upset. We're talking about basic physics here. The principles of physics, tested and verified over centuries, show that Spork's cart, Brian M's cart and all the other engines presented here can work. Once more: if you really don't think Brian's cart can work, why not make one yourself and test your theory?