Down wind faster than the wind

[humber]

Originally Posted by sol invictus

You just contradicted yourself. Either you end up at windspeed - which means zero speed relative to the air, which means the cart stays at fixed position on the treadmill - or you go slower. Make up your mind.

Of course you'll be wrong either way. You can't seem to understand that the motion of the cart is not powered by the wind alone, it's powered by the difference between the speed of the wind and the speed of the ground. That difference has nothing to do with the speed of the cart, and (in principle at least) one can always extract energy from it.

Well, I am truly benighted. If cart is said to be at windspeed when on the belt, and the propellor is in the air. If I get out of the car, I should be blown into the propellor. You model fails to predict this admittedly foolish behavior.
Perhaps you can enlighten me.
To anticipate your objection, you told me that the wheels are the ground.
So, if I hang my legs out of the car, and onto the ground, I will be subjected to torque, rather than the linear motion that we mortals would expect.
Try as I may, I still can't understand why there is wind blowing over the propellor, but not when I put my hand out of the window.
The only thing I could think of is that the belt might be the wind, but you say not.

[Ivor the Engineer]

It has taken me a while to "see" it, but drawing a picture of the cart held stationary on a moving treadmill in a 0m/s wind (which is *identical* to an observer on the cart moving at the speed of the wind on a stationary treadmill) makes it easy to see how thrust generated by the wheel-driven propeller accelerates the cart to a higher speed than the treadmill.

I think.

[humber]

Originally Posted by spork

I don't have the faintest clue. But if you find it you can put it in an escrow account with my $100K and we'll bet on what this cart does.

I wonder why you should suddenly be so coy about publishing calculations that you previously offered for free.

[humber]

Originally Posted by Ivor the Engineer

It has taken me a while to "see" it, but drawing a picture of the cart held stationary on a moving treadmill in a 0m/s wind (which is *identical* to an observer on the cart moving at the speed of the wind on a stationary treadmill) makes it easy to see how thrust generated by the wheel-driven propeller accelerates the cart to a higher speed than the treadmill.

I think.

Yes. The cart is said to be travelling at windspeed, and the motion you see is the difference of the two. That motion is said to be the cart's speed above windspeed, which is oddly like zero.
They will affirm this.

[CyCrow]

I'll repeat myself a bit here: The correct analogy is downwind-tacking iceboats. It is pushed by the propeller, it's not like a geared windmill moving directly upwind. The force/torque to spin the prop is provided by the wheels, and the lift-to-drag ratio of the propeller airfoil allows the lift (push) to exceed the total drag (torque) which is transfered to the wheels. This requires a difference in wind and ground speed. As far as I can see, the top speed is not limited to the wind speed either, it depends on the total lift-to-drag achieved.

// CyCrow

[spork]

Originally Posted by technoextreme

No the prop blades are directly analagous to a sail boat running directly into the wind.

I guess they are if the prop is not spinning. But if the cart is moving the prop is spinning.

[Modified]

Originally Posted by spork

Yes, but unless you show that the vehicles in question can average a downwind velocity component faster than the wind, connecting such vehicles doesn't get you there.

If you can achieve a speed faster than the wind in some direction, then with a small enough friction and drag, you can average faster than the wind in any direction. This can be done by turning in the desired direction, dropping the sail, coasting until the speed is below some threshold, turning back in a favorable direction, re-accelerating, and repeating this process.

[ThinAirDesigns]

Originally Posted by humber

You must have changed your frame of integrity.

-

Humber, you'll have to explain the above comment because it's a mystery to me.

I have repeatedly attempted to engage you and JW in a basic discussion of intertial frames of reference -- no one will discuss it and I'm wondering why. It appears to the be the elephant in the room.

Quote:

Elephants are gray
Mice are gray
Mice are elephants

Perfect example. I asked a simple question upon which an exchange can be based and I get an answer from you that leads to nowhere.

My post requesting that you review my numbers and return your own carries no implication that you agree with me -- even if you agree with those numbers. It means that if you and I agree on those numbers we move on and look at other examples *until* we find where we *do* disagree.

This entire thread has deteriorated and currently has no hope of recovery unless we can determine the precise point of disagreement.

Ball is in your court -- animals answers will get us no closer to agreement ... numbers just might.

JB

[Ivor the Engineer]

Originally Posted by CyCrow

I'll repeat myself a bit here: The correct analogy is downwind-tacking iceboats. It is pushed by the propeller, it's not like a geared windmill moving directly upwind. The force/torque to spin the prop is provided by the wheels, and the lift-to-drag ratio of the propeller airfoil allows the lift (push) to exceed the total drag (torque) which is transfered to the wheels. This requires a difference in wind and ground speed. As far as I can see, the top speed is not limited to the wind speed either, it depends on the total lift-to-drag achieved.

// CyCrow

The bolded section is what I'm not certain about.

[spork]

Originally Posted by humber

I wonder why you should suddenly be so coy about publishing calculations that you previously offered for free.

I have no idea what you're talking about. You said you wanted to accept my wager for $100K. Now you seem to be looking for your $100K. If you find it, let's get this bet on the road.

[CyCrow]

Originally Posted by humber

Yes. The cart is said to be travelling at windspeed, and the motion you see is the difference of the two. That motion is said to be the cart's speed above windspeed, which is oddly like zero.
They will affirm this.

Advancing on the treadmill in still air proves that it is able to exceed downwind speed. To measure top speed, you would need either a very long treadmill, or a combination treadmill and wind tunnel. Or you could do it in less controlled conditions outside. "Oddly like zero" is not zero.

// CyCrow

[spork]

Originally Posted by CyCrow

I'll repeat myself a bit here: The correct analogy is downwind-tacking iceboats. It is pushed by the propeller, it's not like a geared windmill moving directly upwind. The force/torque to spin the prop is provided by the wheels, and the lift-to-drag ratio of the propeller airfoil allows the lift (push) to exceed the total drag (torque) which is transfered to the wheels. This requires a difference in wind and ground speed. As far as I can see, the top speed is not limited to the wind speed either, it depends on the total lift-to-drag achieved.

// CyCrow

I think we have to include CyCrow in the group of people that understand this cart. The only slight correction I'd make is that the top speed is governed by the advance ratio (prop pitch vs. wheel drive for a single prop rotation). the L/D only tells us how closely we can match that theoretical top speed.

[Thabiguy]

Originally Posted by Ivor the Engineer

It has taken me a while to "see" it, but drawing a picture of the cart held stationary on a moving treadmill in a 0m/s wind (which is *identical* to an observer on the cart moving at the speed of the wind on a stationary treadmill) makes it easy to see how thrust generated by the wheel-driven propeller accelerates the cart to a higher speed than the treadmill.

Yes - if the transmission is right. If the propeller was just blowing air backwards at the same speed that the treadmill moves, then the thrust generated by the propeller would be cancelled by equal but opposite force exerted by the treadmill on the cart as it drives the propeller, and nothing would happen.

In order for the device to accelerate, the propeller must be geared to move the air slower (wrt device) than the ground moves (wrt device). Speed will be slower, but exerted force will be greater. This is what will generate the net forward force to accelerate the vehicle.

[mhaze]

Originally Posted by spork

This is an absolute train wreck....But you three can correct us all with no evidence or background whatever - based only on truly bizarre "theories" you make up on the fly?

Build the stupid cart....

Yep. At issue as far as I am concerned is the experimental paradimn (which you have not delivered) that would conclusively prove or disprove the claims made concerning the device.

"Build the stupid cart", is in fact, no more or less than a plea for more stupidity in the form of carts.

By the way in this thread I have not seen an aerodynamic approach to the issues at all. Here I am referring to the conceptual frameworks and grammer as used in such a discussion, as opposed to physics and vectors. Humber comes close with his noting that air close to the cart on the treadmill is stationary, and this is not the same as airflow in the open field. Further, when the prop imparts momentum to the air while on the treadmill, it creates only the local airflow effects of a prop. This is in still air a low performance implementation with high amounts of eddies and swirls behind the prop, which says that your machine would do best with large, very slow turning props.

Looks to me like a reinvention of the autogyro with the prop perpendicular to the earth, and with the treadmill test being a reinvention of the autogyro's "jump start".

[sol invictus]

Originally Posted by humber

I see. We have 450 years of understanding, yet it seems that you are suggesting that the understanding of these laws is yuckky?

No. Read it again.

What I said was that you are denying one of the most basic laws of physics (one which has been understood for 450 years) while simultaneously claiming that those same laws make this device impossible (although of course without ever specifying which law you think it violates).

Originally Posted by humber

Well, I am truly benighted. If cart is said to be at windspeed when on the belt, and the propellor is in the air. If I get out of the car, I should be blown into the propellor. You model fails to predict this admittedly foolish behavior.

Huh?

Is this really so hard for you to understand? If you've ever sailed downwind on a sailboat or a windsurfer you'd see immediately what your error is there. If you stand on deck while sailing straight downwind, you feel almost no wind at all (even when the boat is moving very fast with respect to the water). You don't seem to be able to grasp that.

Quote:

To anticipate your objection, you told me that the wheels are the ground.
So, if I hang my legs out of the car, and onto the ground, I will be subjected to torque, rather than the linear motion that we mortals would expect.

What in the world are you talking about?

Quote:

Try as I may, I still can't understand why there is wind blowing over the propellor, but not when I put my hand out of the window.
The only thing I could think of is that the belt might be the wind, but you say not.

Again, I have no idea what you're talking about. You evidently have some scenario in your head you haven't told the rest of us about, which makes it hard to understand you.

[spork]

Originally Posted by Thabiguy

In order for the device to accelerate, the propeller must be geared to move the air slower (wrt device) than the ground moves (wrt device). Speed will be slower, but exerted force will be greater. This is what will generate the net forward force to accelerate the vehicle.

As much pain as this thread brings me, it really is a comfort when I see postings from guys like Thabiguy that clearly lay out the reality of this little puzzle. It's like a glimmering beacon of hope for humanity.

[Ivor the Engineer]

Originally Posted by spork

As much pain as this thread brings me, it really is a comfort when I see postings from guys like Thabiguy that clearly lay out the reality of this little puzzle. It's like a glimmering beacon of hope for humanity.

Hey, you haven't seen the threads on the Monty Hall problem...

[spork]

Originally Posted by mhaze

Yep. At issue as far as I am concerned is the experimental paradimn (which you have not delivered) that would conclusively prove or disprove the claims made concerning the device.

I'm sorry that you're unable to follow my posts, and those of JB, sol, and Thabiguy.

Quote:

"Build the stupid cart", is in fact, no more or less than a plea for more stupidity in the form of carts.

Actually it's more of a plea for you to follow the long standing scientific tradition of: STFU and try it yourself.

Quote:

By the way in this thread I have not seen an aerodynamic approach to the issues at all.

That's because you haven't understood my vector analysis, and as yet not a single person has asked for any explanation of them. I can only assume that's because there are two kinds of people in the world - those who need no explanation, and those for whom no explanation will help.

[spork]

Originally Posted by Ivor the Engineer

Hey, you haven't seen the threads on the Monty Hall problem...

Sad to admit I've actually started threads on that problem (on other forums).

[ThinAirDesigns]

Originally Posted by CyCrow

Advancing on the treadmill in still air proves that it is able to exceed downwind speed. // CyCrow

Thanks CyCrow.

humbert, if you are willing to have an exchange regarding inertial frames of reference perhaps you too can join the group who agree with Galileo, Newton, Einstein, et al.

JB

[sol invictus]

Originally Posted by mhaze

By the way in this thread I have not seen an aerodynamic approach to the issues at all. Here I am referring to the conceptual frameworks and grammer as used in such a discussion, as opposed to physics and vectors. Humber comes close with his noting that air close to the cart on the treadmill is stationary, and this is not the same as airflow in the open field.

Et tu, Brute?

I'm truly shocked by the lack of even rudimentary physics knowledge displayed here, especially by self-styled engineers.

Here's an analysis of the forces, since so many of you seem incapable of doing it yourself.

Use the frame in which the cart is stationary, the air is stationary, the ground is moving, and the wheels are spinning. That frame and initial condition are physically identical in every way to a situation in which the cart starts off rolling along the ground at exactly the speed of a steady wind. We'll ignore friction, air resistance other than what is relevant to the propeller, and assume the wheels and connection from wheels to propeller can't slip. We want to know if the cart can go faster than the wind, which would mean it accelerates from this initial condition in a direction such that it increases its speed relative to the ground (and its wheels spin faster).

The physics is simple. If the wheels weren't connected to the propeller, Newton's first tells us the cart would remain stationary in this frame (no friction, and no wind force on the propeller since the air is still). When the wheels are connected the propeller spins and generates a force. There is also a force from the torque on the wheels (which is now non-zero since there is resistance from the propeller).

To see what happens next, consider re-orienting the propeller. If you aim it up, like a helicopter, there will be a force up from that, and a force back from the wheels, so the cart will start to fall back (i.e. move with the ground, with its wheels spinning slower). If you orient it so it pushes back, the cart will fall back faster. But if you orient it so it pushes forward, opposite to the ground motion, there are two forces acting in opposite directions and one must check their magnitudes. There is no principle which says one must be bigger than the other - and given some assumptions about the propeller and the gearing one could easily estimate them. If the propeller force is larger, the cart will move forward against the direction of the ground motion - which means faster than the wind.

I have not done the estimate of the forces, which is why (as I have said all along) I don't consider it obvious that this particular design will work. However there is no reason why it shouldn't, and the videos are convincing. The burden of proof is fully on anyone that doubts it - there is no legitimate reason given by anyone here why it shouldn't work.
That's it.

[ThinAirDesigns]

Originally Posted by sol invictus

Et tu, Brute?

I'm truly shocked by the lack of even rudimentary physics knowledge displayed here, especially by self-styled engineers.

Here's an analysis of the forces, since so many of you seem incapable of doing it yourself.

Use the frame in which the cart is stationary, the air is stationary, the ground is moving, and the wheels are spinning. That frame and initial condition are physics identical in every way to a situation in which the cart is rolling at exactly the speed of a stead wind. We'll ignore friction, air resistance other than what is relevant to the propeller, and assume the wheels and connection from wheels to propeller can't slip. We want to know if the cart can go faster than the wind, which means it accelerates from this initial condition in a direction such that it increases its speed relative to the ground (the wheels spin faster).

The physics is simple. If the wheels weren't attached, Mr. Newton tells us the cart would remain stationary in this frame (no friction and no wind force on the propeller since the air is still). When the wheels are connected the propeller spins and generates a force. There is also a force from the torque on the wheels (which is now non-zero since there is resistance from the propeller).

To see what happens next, consider re-orienting the propeller. If you aim it up, like a helicopter, there will be a force up from that, and a force back from the wheels, so the cart will start to fall back (i.e. move with the treadmill). If you orient it so it pushes back, the cart will fall back faster. But if you orient it so it pushes forward, opposite to the treadmill motion, there are two forces acting in opposite directions and one must check their magnitudes. There is no principle which says one must be bigger than the other - and given some assumptions about the propeller and the gearing one could easily estimate them. If the propeller force is larger, the cart will move forward against the direction of the treadmill motion - which means faster than the wind.

I have not done this estimate, which is why (as I have said all along) I don't consider it obvious that this particular design will work. However there is no reason why it shouldn't, and the videos are convincing. The burden of proof is fully on anyone that doubts it - there is no legitimate reason given by anyone here why it shouldn't work.
That's it.

And I get to take yet another breath of very fresh air.

Thanks sol.

JB

[humber]

Originally Posted by sol invictus

No. Read it again.

Again, I have no idea what you're talking about. You evidently have some scenario in your head you haven't told the rest of us about, which makes it hard to understand you.

No. There is no wind blowing over the cart at any time. The car held in the hand is the same as said to be at windspeed. The incremental gain that you see, is the actual speed relative to ground.

Your model is wrong, because, as has been stated several times, the belt is the wind, but it is not it is the ground. Otherwise the porpeller should be embedded in the belt. This is not a new frame of reference.

The cart is the cart
The wheels are the wheels
The belt is the ground ( connected to the real ground of the treadmill body)
The air is the air
The propellor is the propellor
The observed speed is the actual speed relative to ground

Is it not amazing that this light cart is not blown away by the wind. Seems to happen in the video.
There is no wind. The concept is a sophism.

Please note that this thread has a high Einstein citation index.

[sol invictus]

Originally Posted by humber

No. There is no wind blowing over the cart at any time.

This is amazing.

How much education in physics do you have? Have you taken the equivalent of a first-year college course?

Quote:

Your model is wrong, because, as has been stated several times, the belt is the wind, but it is not it is the ground. Otherwise the porpeller should be embedded in the belt.

"the belt is the wind, but it is not it is the ground. Otherwise the porpeller should be embedded in the belt."

Are you a random text generator?

[Ivor the Engineer]

Originally Posted by humber

No. There is no wind blowing over the cart at any time. The car held in the hand is the same as said to be at windspeed. The incremental gain that you see, is the actual speed relative to ground.

Your model is wrong, because, as has been stated several times, the belt is the wind, but it is not it is the ground. Otherwise the porpeller should be embedded in the belt. This is not a new frame of reference.

The cart is the cart
The wheels are the wheels
The belt is the ground ( connected to the real ground of the treadmill body)
The air is the air
The propellor is the propellor
The observed speed is the actual speed relative to ground

Is it not amazing that this light cart is not blown away by the wind. Seems to happen in the video.
There is no wind. The concept is a sophism.

Please note that this thread has a high Einstein citation index.

And how can an observer sitting on the cart tell if the ground (treadmill) is moving under the cart with no wind, or the cart is moving with the wind over a stationary ground (treadmill)?

[humber]

Yes. Simple arithmetic calculations. Why bother with the real windspeed over the cart, when you can simply eliminate it by subtracting the belt speed.

[spork]

Originally Posted by sol invictus

Are you a random text generator?

Thanks for the assist. I was beginning to think I was solely responsible for insults on this thread.

[spork]

Originally Posted by humber

Yes. Simple arithmetic calculations. Why bother with the real windspeed over the cart, when you can simply eliminate it by subtracting the belt speed.

FINALLY!!! (if only you weren't being sarcastic)

[Ivor the Engineer]

Originally Posted by humber

Yes. Simple arithmetic calculations. Why bother with the real windspeed over the cart, when you can simply eliminate it by subtracting the belt speed.

Is your claim that the cart can never get up to windspeed in the first place?

[technoextreme]

Originally Posted by sol invictus

The physics is simple. If the wheels weren't connected to the propeller, Newton's first tells us the cart would remain stationary in this frame (no friction, and no wind force on the propeller since the air is still). When the wheels are connected the propeller spins and generates a force. There is also a force from the torque on the wheels (which is now non-zero since there is resistance from the propeller).

The physics is simple and yet you think there is zero torque on a cart rolling on a treadmill?

[humber]

On the belt, the cart is at windspeed, with a little forward motion.
Stop the belt and the cart will remain in place.
That difference in velocities is the actual difference between the cart's velocity in the presence of wind and still air.

Conclusion.This is not a model of the real cart in wind.

[Ivor the Engineer]

Originally Posted by technoextreme

The physics is simple and yet you think there is zero torque on a cart rolling on a treadmill?

<snip>

Huh? Sol explicitly stated that by connecting the propeller to the wheels means a torque greater than zero is required to turn the wheels. With suitable gearing and propeller selection the net force from the treadmill on the cart and the prop can be adjusted (in theory and apparently in practice) to be in a direction which causes the cart to accelerate to above the speed of the treadmill.

[ThinAirDesigns]

Originally Posted by technoextreme

The physics is simple and yet you think there is zero torque on a cart rolling on a treadmill?

The insanity is you claiming he said "zero" when he said "non-zero".

JB

[Thabiguy]

Originally Posted by technoextreme

Perhaps you should stop doing that.

[ThinAirDesigns]

Originally Posted by Thabiguy

Perhaps you should stop doing that.

I think the really BIG question on this tread is will techno's forehead survive his physics lessons.

JB

[humber]

It's not a claim, because the concept is nonsense. To try to answer your question, the cart is assumed to be at windspeed when placed upon the belt.

Ignoring the observed tiny speed. we have two options:
The cart is at windspeed when in the hand or on the belt. ( no sensible wind over cart)
The cart is at zero velocity when in the hand or on the belt. ( no sensible wind over cart)
It's paradoxical, because it is nonsense.
This platform represents a cart that keeps itself at zero velocity regardless of windspeed.
It is understandable, but unbelievable that such a model would be proposed. That's the difficulty of understanding.
All this headbanging is astonishment at support of such a banal and absurd claim. It is not even wrong.

[technoextreme]

Originally Posted by Ivor the Engineer

Huh? Sol explicitly stated that by connecting the propeller to the wheels means a torque greater than zero is required to turn the wheels.

Which is wrong from a physics standpoint. You always need a torque greater than zero to turn a wheel.

Quote:

With suitable gearing and propeller selection the net force from the treadmill on the cart and the prop can be adjusted (in theory and apparently in practice) to be in a direction which causes the cart to accelerate to above the speed of the treadmill.

Right but it needs to be done in BOTH DIRECTIONS at the same time in order to travel faster than wind. You can't do it with just a belt drive.

[spork]

I have to wonder - if Galileo, Newton, and Einstein came back from the dead to explain this in simple terms, mathematical formulas, and simple pictures (using multiple colored markers) - would humber and techno tell them they're all idiots?

I take it back. Of course they would.

[ThinAirDesigns]

ivor:

Quote:

Huh? Sol explicitly stated that by connecting the propeller to the wheels means a torque greater than zero is required to turn the wheels.

-
techno:

Quote:

Which is wrong.

How can it be wrong techno? With the propellor attached, a torque greater than zero IS required to turn the wheels.

First you incorrectly say Sol thinks it's zero. When it's pointed out to you that So correctly said "non-zero" you now say it's wrong.

So, we have a clearly stated position from techno:

It's insane to think the torque is zero and it's wrong to think it's non-zero.

I rest my case.

JB

[ThinAirDesigns]

Originally Posted by spork

I have to wonder - if Galileo, Newton, and Einstein came back from the dead to explain this in simple terms, mathematical formulas, and simple pictures (using multiple colored markers) - would humber tell them they're all idiots?

There's no need to wonder.

JB