Merged DDWFTTW in a “Real” Wind

[Llyricist]

It isn't PM for the ground to "drive" the wheel. The forward force on the cart results in a rearward tangential force on the wheel from the ground of the same value. That force is transmitted, through appropriate gearing to present a larger torque force on the prop shaft than the torque force the wind creates in the opposite direction. the result will be forward motion of the cart with the prop spinning as a prop.

You can repeat your mantra that gearing doesn't make any difference all you want, you will only continue to discredit yourself.

 

[humber]

It isn't PM for the ground to "drive" the wheel. The forward force on the cart results in a rearward tangential force on the wheel from the ground of the same value. That force is transmitted, through appropriate gearing to present a larger torque force on the prop shaft than the torque force the wind creates in the opposite direction. the result will be forward motion of the cart with the prop spinning as a prop.

You can repeat your mantra that gearing doesn't make any difference all you want, you will only continue to discredit yourself.

Drivel PM is about over-unity energy. The derived net force is bogus, because you don't have the energy to drive it. That inconsistency proves that the argument is false.

 

[humber]

Spork's electical cart in the NALSA submissom tell you that it won't work mechanically either. The wheel drives a generator, which drives a motor at the prop.
But...
http://www.animations.physics.unsw.edu.au/jw/electricmotors.html
Back emf
"Now, as the first two animations show, DC motors and generators may be the same thing. For example, the motors of trains become generators when the train is slowing down: they convert kinetic energy into electrical energy and put power back into the grid. Recently, a few manufacturers have begun making motor cars rationally. In such cars, the electric motors used to drive the car are also used to charge the batteries when the car is stopped - it is called regenerative braking.
So here is an interesting corollary. Every motor is a generator. This is true, in a sense, even when it functions as a motor. The emf that a motor generates is called the back emf. The back emf increases with the speed, because of Faraday's law. So, if the motor has no load, it turns very quickly and speeds up until the back emf, plus the voltage drop due to losses, equal the supply voltage. The back emf can be thought of as a 'regulator': it stops the motor turning infinitely quickly (thereby saving physicists some embarrassment). When the motor is loaded, then the phase of the voltage becomes closer to that of the current (it starts to look resistive) and this apparent resistance gives a voltage. So the back emf required is smaller, and the motor turns more slowly. (To add the back emf, which is inductive, to the resistive component, you need to add voltages that are out of phase.

The generator may drive the motor, but when the wind drives the prop so as to aid the motor, the back EMF rises, and the current from the generator fall.
Just like the finger at the prop. Work at the prop, is taken from work at the wheel.
You may know this, the current in a motor will rise when loaded, so will fall when aided.

 

[Llyricist]

Drivel PM is about over-unity energy. The derived net force is bogus, because you don't have the energy to drive it. That inconsistency proves that the argument is false.

Right there is no energy available in volume of air with cross section of ~20 sq feet moving at 10 knots.....

I'll remember that.

 

[Jack by the hedge]

Not possible. The prop and wheel speeds are fixed.
And what drives the wheel to drive the prop?
See, PM, but with a sugar coating.

What's not possible? You're not making any sense.

If you lift the wheels off the ground and blow air from the front then the prop spins. If the cart runs downwind faster than the wind then the prop turns in the same direction and from the prop's point of view the air is flowing over it in the same direction.

What does the fixed relationship between the wheels and prop's speed have to do with it? In the first case the wheels are just spinning off the ground.

The prop is being pushed forward by the wind. (It's a headwind from the cart's point of view, but the prop is turning quickly enough that it appears to be a tailwind from the blades' point of view.) The forwards push on the prop pushes the whole cart forwards and that turns the wheels which in turn spins the prop.

That's not perpetual motion so long as the work done to turn the prop is less than the work done pushing the prop forwards (plus friction blah, blah). So a fundamental requirement is that the wind pushing on the back of the blade applies more forwards force than it applies turning force.

The energy comes from the wind's movement over the ground. Because of the friction of the wheels and their gearing to the prop, there is effectively a rigid connection from the ground to the prop blade.

From the point of view of each fingers-breadth airstream which the prop's leading edge cuts through, the surface of the prop as it slides past presents a surface which is advancing slower than the airstream, so the air pushes it.

The push from the air partly contributes a force trying to oppose the spinning of the prop, but so long as it's less than the force pushing the cart forward against friction and turning the prop the desired way, it'll keep accelerating.

 

[Llyricist]

Spork's electical cart in the NALSA submissom tell you that it won't work mechanically either. The wheel drives a generator, which drives a motor at the prop.
But...
http://www.animations.physics.unsw.edu.au/jw/electricmotors.html
Back emf
"Now, as the first two animations show, DC motors and generators may be the same thing. For example, the motors of trains become generators when the train is slowing down: they convert kinetic energy into electrical energy and put power back into the grid. Recently, a few manufacturers have begun making motor cars rationally. In such cars, the electric motors used to drive the car are also used to charge the batteries when the car is stopped - it is called regenerative braking.
So here is an interesting corollary. Every motor is a generator. This is true, in a sense, even when it functions as a motor. The emf that a motor generates is called the back emf. The back emf increases with the speed, because of Faraday's law. So, if the motor has no load, it turns very quickly and speeds up until the back emf, plus the voltage drop due to losses, equal the supply voltage. The back emf can be thought of as a 'regulator': it stops the motor turning infinitely quickly (thereby saving physicists some embarrassment). When the motor is loaded, then the phase of the voltage becomes closer to that of the current (it starts to look resistive) and this apparent resistance gives a voltage. So the back emf required is smaller, and the motor turns more slowly. (To add the back emf, which is inductive, to the resistive component, you need to add voltages that are out of phase.

The generator may drive the motor, but when the wind drives the prop so as to aid the motor, the back EMF rises, and the current from the generator fall.
Just like the finger at the prop. Work at the prop, is taken from work at the wheel.
You may know this, the current in a motor will rise when loaded, so will fall when aided.

The air never aids the rotation of the prop.

 

[Jack by the hedge]

The derived net force is bogus, because you don't have the energy to drive it.

The energy comes from the wind moving over the ground.

 

[Jack by the hedge]

...The generator may drive the motor, but when the wind drives the prop so as to aid the motor, the back EMF rises, and the current from the generator fall.
Just like the finger at the prop. Work at the prop, is taken from work at the wheel.
You may know this, the current in a motor will rise when loaded, so will fall when aided.

Fail. The wind pushes the prop forward, but it also acts in part against the turning of the prop. It does not aid it. The load on the motor is increased, not decreased.

I really think you need to think more carefully about you precise terminology. For example when you say "the wind drives the prop", you fail to differentiate between the wind's forwards pressure on the prop and its turning force on the prop. In this machine it is vital to consider the two separately, as one provides motive power but the other is a loss.

 

[spork]

Randi's appearances on this forum are very rare indeed. You could always try mailing him directly.

He and I actually have traded a few emails, but he said something to the effect of "I'm not an engineer" and pretty much dropped it. I hoped that if one of his peeps from the forum brought it up, he might give it a look.

I'd love to see your upwind trials. Are you still planning to bring the cart to Europe?

People have suggested bringing it to Europe, but we've never really given that any serious thought. I can't imagine anyone in their right mind spending the money for that.

 

[Jack by the hedge]

I can't imagine anyone in their right mind spending the money for that.

Well that should usefully narrow down the search for a sponsor: You can limit your enquiries to insane millionaires.

 

[humber]

What's not possible? You're not making any sense.
If you lift the wheels off the ground and blow air from the front then the prop spins. If the cart runs downwind faster than the wind then the prop turns in the same direction and from the prop's point of view the air is flowing over it in the same direction.

The claim is that the cart is not PM, because it extracts energy from the wind. But, the wheel drives the prop. What drives the cart, to get that headwind that is said to drive the prop?

It's the wheel, apparently. Spork has a generator at the wheel, driving a motor at the prop. This is plausible if the cart is towed above WS. Then the cart's KE can run the generator. So far, so good. But, when released, the cart will lose KE, so slow. The wind must then be the power source to replace the towing car. But that wind comes from the cart's motion. That should say "PM"

But, it won't work at the mechanical level, if you could get energy from the wind. In principle, motors and generators consume no power. They are transducers, converting electrical energy to mechanical energy.
So, in principle, a motor or generator without a mechanical load, will not consume any power. If the wind drives the prop, that will reduce the mechanical load on the motor, and so the generator output will fall by the same amount. To argue that it won't, is to deny regenerative braking.
It can't work.
Recall that the is supposedly a ratchet, so there is not chance of the prop influencing the wheel, but if it's not there, it still won't work. The small cart has no ratchet, yet the the BB and that cart are said to be the same.
Inconsistency brought about by ad-hoc theory.

What does the fixed relationship between the wheels and prop's speed have to do with it? In the first case the wheels are just spinning of the ground.

When off the ground, no work is done on the cart.

The prop is being pushed forward by the wind. (It's a headwind from the cart's point of view, but the prop is turning quickly enough that it appears to be a tailwind from the blades' point of view.) The forwards push on the prop pushes the whole cart forwards and that turns the wheels which in turn spin the prop.

Which means the wheel must turn faster. Which turns the prop faster, which turns the wheel faster. Why does that not work in still air?
Push the cart, and it sees a headwind, which you say is tailwind to the spinning prop, so off it goes?

That's not perpetual motion so long as the work done to turn the prop is less than the work done pushing the prop forwards. So a fundamental requirement is that the wind pushing on the back of the blade applies more forwards force than it applies turning force.

As long as....
What wind pushing from the rear? There is no tailwind. That is why dwfttw is considered to be impossible. You have the cart generating it's own headwind and tailwind! Good grief. The simpler, and realistic explanation, is that the cart is driven by gusts and not ddw. It is not ddw.

The energy comes from the wind's movement over the ground.

Right, and that wind not there for objects at wind speed. The damn thing contradicts the Galilean theory on which it is built.
Exactly at WS, there is no wind. That is a claim invoked in the TM.
But the prop is turning. It is churning that "still" air. What drives it? The ground? The prop powers itself?

Because of the friction of the wheels and their gearing to the prop, there is effectively a rigid connection from the ground to the prop blade.
From the point of view of each fingers-breadth airstream which the prop's leading edge cuts through, the surface of the prop as it slides past presents a surface which is advancing slower than the airstream, so the air pushes it.
The push from the air partly contributes a force trying to oppose the spinning of the prop, but so long as it's less than the force pushing the cart forward against friction and turning the prop the desired way, it'll keep accelerating.

No. The prop does not do that.
The blade strikes the air, and a flow occurs. The air immediately above the surface travels at the speed of the surface.
http://en.wikipedia.org/wiki/No-slip_condition
From there is returns eventually to the free stream velocity of the wind.

 

[humber]

He and I actually have traded a few emails, but he said something to the effect of "I'm not an engineer"

Snap.

People have suggested bringing it to Europe, but we've never really given that any serious thought. I can't imagine anyone in their right mind spending the money for that.

But your mind is not right.

 

[Llyricist]

Jack,

You're getting close to where he will claim, outright, that the distance the prop moves through the air is the same as the distance the wheels move over the ground.

 

[humber]

Will you want a ticker parade for the giant upwind cart that exploits the wind gradient?

One of you sponsor's Joby, is planning to launch turbines it get access to the high speed wind. Your cart will be a lower altitude version of that.
I tell you what. I will post you the record, and save you the trouble of building the foregone conclusion.

ETA:
I wonder what special sauce you are going to add to your cart? Other than the wind gradient, of course.
There are many designs amongst the competitors of upwind carts. Some are mechanical, and some electrical.
They have variable pitch props and all sorts of other refinements. It is the gearing?
Many have variable transmissions. I suppose that none of the 20 engineering students or their Professors, who
comprise those teams, just didn't get around to turning the transmission control to "11".

 

[Subduction Zone]

Myriad, I took this quote from you:

Yes, those are some of the arguments that I find unconvincing, and in some cases, not even relevant. If anyone else finds them relevant and convincing, I invite them to explain to me why.

That seemed to be in reference to the treadmill. I once, by limiting humber to yes no responses, got him to almost admit that the cart on the treadmill was equivalent to the cart running directly downwind at wind speed outside. If you like I could run through this exercise again with you.

 

[humber]

Jack,

You're getting close to where he will claim, outright, that the distance the prop moves through the air is the same as the distance the wheels move over the ground.

Oh, so you can play games, but without the math. Isn't that right?
Talk of absolute space, over a flying scrap heap. That is so woo.

The idea of that distance traveled through the air, came from Steve Smith.

Spork posted an email from smith, in response to questions I put to NASA.

In that same post, Smith suggested that measuring the current in the generator, may tell if the idea works or not.
It doesn't.

ETA:
And BTW, I suggested that test to Spork before that e-mail. And even for the TM.
Now, I am good at electronics so you won't be able to play games, and I have NASA's validation that the idea sound.

 

[Myriad]

Myriad, I took this quote from you:


That seemed to be in reference to the treadmill. I once, by limiting humber to yes no responses, got him to almost admit that the cart on the treadmill was equivalent to the cart running directly downwind at wind speed outside. If you like I could run through this exercise again with you.

No, it's in reference to all of humber's claims. Sorry if that was unclear.

Respectfully,
Myriad

 

[humber]

Myriad, I took this quote from you:


That seemed to be in reference to the treadmill. I once, by limiting humber to yes no responses, got him to almost admit that the cart on the treadmill was equivalent to the cart running directly downwind at wind speed outside. If you like I could run through this exercise again with you.

If I recall, the yes/no limit restricted me to "yes, that's ********" and "no, that's ********". SZ.

 

[Llyricist]

Oh, so you can play games, but without the math. Isn't that right?
Talk of absolute space, over a flying scrap heap. That is so woo.

The idea of that distance traveled through the air, came from Steve Smith.

No, it came from reality. It comes from anyone that understands aerodynamics. It was always part of the power analysis. And you still think the distance is the same, which is the point, which btw, you haven't denied.

 

[humber]

No, it came from reality. It comes from anyone that understands aerodynamics. It was always part of the power analysis. And you still think the distance is the same, which is the point, which btw, you haven't denied.

It came from Steve Smith. Up until that point, Drela and Bauer where the references, and neither of those two make that distance claim, and neither did Spork.

But, I have the NASA approved motor test, from one of their engineers who wrote to me with the very claim you are making. Steve Smith. He suggested it as a test of the idea.

But, acceleration tells all. Both the cart and the prop must accelerate at the same rate. So for linear acceleration, each will travel S= 1/2at^2.
That distance that is independent of initial velocity. Hence S = ut +1/2at^2, where u is the initial velocity.