Merged DDWFTTW in a “Real” Wind

[drewid]

The gimmick is childishly simple, Humber. Suppose the tow vehicle is putting 10 Watts into the system by towing the vehicle. If the efficiency of the cart from wheels to air is 90%, then the prop will extract 9 Watts from the wind. For a brief instant, the cart has an effective power of 19 Watts and tries to accelerate. Just as soon as it does (or the tow rope is released) the 10 Watts from the tow vehicle is gone. Now the cart has 9 Watts and begins to slow down, constantly losing power as it does, until it is once again well below wind speed. The entire idea is childish and incredibly naive.

That is precisely not what is shown in the figures.

 

[Llyricist]

Sure.
The energy of the wind is less than the energy you claim is used by the cart. It is not because of losses,

Wrong, the energy "used" by the cart is precisely the energy lost by the cart plus the KE gained by the cart.

In this case, in an FOR where the ground is stationary, the losses amount to:
86 J/s to aerodynamic drag;
437 J/s to rolling resistance;
365 J/s to losses in the drive train, and;
724 J/s to aerodynamic losses at the propeller. For a total of

1612 J/s, in losses

And with a net force of 50 newtons the cart will accelerate by 50 N / 295 kg = .17 m/s in one second, from 11.62 m/s to 11.79 m/s.

.5 * 295 * 11.62² = 19916 J
.5 * 295 * 11.79² = 20503 J

For a gain of 587 J

Giving a total energy used by the cart of 2199 J in one second. Close enough to the 2189 J lost by the air with all the rounding errors.

That's how the energy balances.

Javaprop applies to propellers driven by an engine.

It applies to propellers regardless of how they are driven.

You will not find any sign of the prop shaft taking energy from the wind.

That's good, because it is all taken linearly, along the axis of the shaft.

The only source of energy coming in, is the KE of the wind flow, and you are claiming to exceed that.

nope, I'm only claiming 2189 J out of the 3209 J it started with.

The cart does not work as described, because that would be over unity.

Yes it does, and no it wouldn't.

 

[humber]

And that 2189 J is more than enough to cover all the losses in the cart and add to it's KE to boot.

And you have a scheme for slowing the air to a standstill wrt the ground, and doing so at 100% efficiency? That is news, and I am sure that current wind turbine designers will want to know how Betz's limit was exceeded.

But, even that impossible energy does not fill the gap

Wheel Power = 3983W
Transferred to air as = 2280W
Loss = 1703W

Aero Drag = 86W
Wheel Drag = 437W

Total Loss = 1703 + 437 + 86
2226J/s
As earlier calculated.

If all the energy from the wind could be extracted, it could supply only
2189J/s. That is less than the 2280J/s added as air power.
So, a gain upon a 100% efficient system.

 

[Llyricist]

And you have a scheme for slowing the air to a standstill wrt the ground,

Wrong it slows from 6.23 m/s to 3.604 m/s, do the math.

and doing so at 100% efficiency?

nope

That is news, and I am sure that current wind turbine designers will want to know how Betz's limit was exceeded.

by using a propeller, rather than a turbine. There is no Betz limit on propellers.

But, even that impossible energy does not fill the gap

Wheel Power = 3983W
Transferred to air as = 2280W
Loss = 1703W

It doesn't work that way, 2900 W is the number to use, not 2280.

 

[humber]

Wrong, the energy "used" by the cart is precisely the energy lost by the cart plus the KE gained by the cart.

In this case, in an FOR where the ground is stationary, the losses amount to:
86 J/s to aerodynamic drag;
437 J/s to rolling resistance;
365 J/s to losses in the drive train, and;
724 J/s to aerodynamic losses at the propeller. For a total of

1612 J/s, in losses

Those are the losses from wheel to prop and drag losses. The total demand is 3989W at the wheel.

The entire power of the wind relative to the ground at 6.39m/s wind speed
P = E/t = 1/2*A*p*v^3
P = 1/2*20*1.23*6.39^3
=3209W

Even a 100% lossless cart would lose the battle.

 

[humber]

Wrong it slows from 6.23 m/s to 3.604 m/s, do the math.

If it slows to zero, the maximum possible extraction the energy is 3209J/s
No such extraction is possible.
You have a wheel consumption of 3828J/s.

 

[Llyricist]

Those are the losses from wheel to prop and drag losses. The total demand is 3989W at the wheel.

Wrong, you said "energy used" the cart doesn't use any energy beyond what it loses and what KE it gains.

The entire power of the wind relative to the ground at 6.39m/s wind speed
P = E/t = 1/2*A*p*v^3
P = 1/2*20*1.23*6.39^3
=3209W

Even a 100% lossless cart would lose the battle.

The cart does not use a turbine.

 

[Llyricist]

If it slows to zero, the maximum possible extraction the energy is 3209J/s
No such extraction is possible.

Wrong, do the math, the change in velocity is as I stated, remember KE has a quadratic relationship to speed.

You have a wheel consumption of 3828J/s.

And a power in an FOR where the ground is stationary of thrust * v_cart, or 5089 W pushing the cart.

 

[humber]

Wrong, do the math, the change in velocity is as I stated, remember KE has a quadratic relationship to speed.

And a power in an FOR where the ground is stationary of thrust * v_cart, or 5089 W pushing the cart.

KE 1m^3 air at 1m ( m= 1.23kg)
= 1/2mV^2
= 1/2*1.23*1
= 0.615J

KE of air 1m^3 at 2m/s
= 1/2*1.23*2^2
= 2.46J

But v has been doubled so 2m^3 pass in 1 second
P = 2*2.46J/1s
= 4.92J/s
=4.92W

so,
P = v*1/2m^v^2
=1/2mv^3

At 6.39m/s
P = 1/2*1.23*6.39^3
160.46J/s

Prop disk = 20m^2
P = 20*160.46
3209W

That is 100% of the available energy, but can't be extracted. That is less than 5089W you are claiming, and proof that you are using the same energy at least twice.

 

[Llyricist]

KE 1m^3 air at 1m ( m= 1.23kg)
= 1/2mV^2
= 1/2*1.23*1
= 0.165J

KE of air 1m^3 at 2m/s
= 1/2*1.23*2^2
= 2.46J

But v has been doubled so 2m^3 pass in 1 second
P = 2*2.46J/1s
= 4.92J/s
=4.92W

so,
P = v*1/2m^v^2
=1/2mv^3

At 6.39m/s
P = 1/2*1.23*6.39^3
160.46J/s

Prop disk = 20m^2
P = 20*160.46
3209W

That is 100% of the available energy, but can't be extracted. That is less than 5089W you are claiming, and proof that you are using the same energy at least twice.

I'm only claiming 2189 J of energy. That energy, and 2900 J of the 3989 J negative work done on the cart, account for the 5089 W of power pushing the cart in an FOR where the ground is stationary,

 

[humber]

I'm only claiming 2189 J of energy. That energy, and 2900 J of the 3989 J negative work done on the cart, account for the 5089 W of power pushing the cart in an FOR where the ground is stationary,

The total but impossible to extract energy input from the wind is 3209J/s.
The wheel has a drag force to drive it ( the generator of the submission) and produces 5093J/s.

You are claiming more energy from the generator than can be input, and then trying to put that energy back in, so the consumption is reduced to 2189J. That is not possible. No machine can be constructed to extract more energy than input, even if it "puts it back"

Even the impossible the 2189 claim is further damned, because that would be an impossible 2189/3209 = 68.2% efficiency.

 

[jduffy77]

That is precisely not what is shown in the figures.

Most hilariously ppg's own figures.

 

[jduffy77]

The total but impossible to extract energy input from the wind is 3209J/s.
The wheel has a drag force to drive it ( the generator of the submission) and produces 5093J/s.

You are claiming more energy from the generator than can be input, and then trying to put that energy back in, so the consumption is reduced to 2189J. That is not possible. No machine can be constructed to extract more energy than input, even if it "puts it back"

Even the impossible the 2189 claim is further damned, because that would be an impossible 2189/3209 = 68.2% efficiency.

Humber do you even notice when you do an "analysis" and the results contradict hundreds of your own prior "analyses"? You should work on at least trying to keep your own Humbermath straight. Does it ever bother you that you never get the same result twice?

 

[drewid]

And you might want to go back to your day-care centre.



I agree with all of that! It IS possible the top of the belt can be at a constant velocity, but only IF great care is taken to ensure this is so. For medical research there are very special "force treadmills" in use that employ unusually powerful motors and heavy flywheels attached to the rollers in an effort to eliminate the accelerations on the belt due to the non-inertial nature of the belt going around the rollers.

Medical treadmills are used for precise measurements in high stress conditions. The idea that a 170 pound human being, using muscle force, walking or running on a treadmill can be compared to a small lightweight wheeled cart is clearly nonsense.

It would be interesting to see if the cart can run on one of these specially modified treadmills.

Would you accept it as evidence if it could?

 

[Llyricist]

The total but impossible to extract energy input from the wind is 3209J/s.

The number is right, the "impossible" is wrong (this is not a turbine), and the cart only extracts 2189 J/s from the wind in this circumstance. By slowing it down by less than half.

The wheel has a drag force to drive it

The drag force hinders it.

( the generator of the submission)

This is not the submission, there is no generator in this case.

and produces 5093J/s.

nothing produces 5093 J/s by itself.

You are claiming more energy from the generator than can be input, and then trying to put that energy back in, so the consumption is reduced to 2189J. That is not possible. No machine can be constructed to extract more energy than input, even if it "puts it back"

This from somebody who claims to understand electronics.

Feedback loops are commonplace, and only need to be fed enough energy to cover their losses.

The only energy that is used, is that which is either lost to heat or useless work, and that which is gained in KE.

Even the impossible the 2189 claim is further damned, because that would be an impossible 2189/3209 = 68.2% efficiency.

A propeller is not a turbine, there is no Betz limit on propellers.

 

[profpangloss]

Medical treadmills are used for precise measurements in high stress conditions. The idea that a 170 pound human being, using muscle force, walking or running on a treadmill can be compared to a small lightweight wheeled cart is clearly nonsense.

Yes, such a comparison would be nonsense, and that is probably why I never made any such comparison. What I did compare was the treadmills themselves, making the observation that the modified "force treadmill" largely eliminates belt variations due to the belt itself (with nobody walking on it) going around the end cylinders. The variations would be tiny, and are of no concern during normal treadmill usage, but may be large enough to influence the behaviour of the equally tiny cart on the belt. It is possible that very slight back and forth accelerations on the belt may act in the manner of a vibratory conveyor, in sending the cart up the belt. It is a possibility that cannot be discounted.

Would you accept it as evidence if it could?

As evidence of DDWFTTW? No I would not. If there can be assurance the belt is not under going any accelerations at all, I would have to discount the possibility of the cart being shuffled up the belt due to such accelerations. That still would not convince me of the treadmill equivalency because a power analysis says the cart cannot power itself up the belt, powered by the belt in any normal fashion. If the "vibratory conveyor" possibility is eliminated, then I would have to consider other possibilities.
I have already alluded to one of those possibilities when I pasted that photo of the (cylindrical) lawn mower. If you have ever used one you would know that sometimes when you push on it, instead of cutting the grass it rides up over the top of the grass. The wheels still spin and the cylinder still spins but it is cutting no grass and it is much easier to push than when it is cutting. The cart, after being held on the belt and allowed to spin up and develop thrust, can be doing something similar to that lawn mower. It can just be scooting along the belt, very lightly in contact with the belt, running on the built-up thrust and only gaining a tiny bit of energy from the belt to keep the thrust topped up, so to speak. It is not rolling up the belt and drawing full power and thus feeling full drag, just lightly riding over the top of the belt in a similar manner to the lawn mower that has ridden up on the grass. It is a possibility that should be investigated. Perhaps a strobe light would shed a bit of light on the issue?

 

[spork]

As evidence of DDWFTTW? No I would not.

Is there anything that you could ever possibly imagine seeing that you would accept as evidence that the DDWFTTW cart works?

Just kidding - we all know the answer to that one.

Would you be willing to enter a very simple and brief discussion that could illustrate to you that the cart on the treadmill is a valid demonstration of the cart going DDWFTTW?

Never mind. If these questions make you uncomfortable, please ignore them completely. It's probably best to simply pretend this post does not exist. Delusion is its own reward.

 

[mender]

The cart, after being held on the belt and allowed to spin up and develop thrust, can be doing something similar to that lawn mower. It can just be scooting along the belt, very lightly in contact with the belt, running on the built-up thrust and only gaining a tiny bit of energy from the belt to keep the thrust topped up, so to speak. It is not rolling up the belt and drawing full power and thus feeling full drag, just lightly riding over the top of the belt in a similar manner to the lawn mower that has ridden up on the grass. It is a possibility that should be investigated. Perhaps a strobe light would shed a bit of light on the issue?

And what would the strobe show?

 

[phunk]

And you might want to go back to your day-care centre.

I was serious, you're making pretty simple mistakes that could be cleared up by re-reading your high school physics book, assuming you ever took the class.

I agree with all of that! It IS possible the top of the belt can be at a constant velocity, but only IF great care is taken to ensure this is so. For medical research there are very special "force treadmills" in use that employ unusually powerful motors and heavy flywheels attached to the rollers in an effort to eliminate the accelerations on the belt due to the non-inertial nature of the belt going around the rollers.

Wrong. They employ powerful motors and flywheels to eliminate the deceleration caused by a hundreds of lbs of runner bouncing on them. An unloaded treadmill doesn't need all that to run at constant speed, and a tiny cart in constant contact isn't creating any sort of pulsating load on the treadmill.

It would be interesting to see if the cart can run on one of these specially modified treadmills.
Ordinary treadmill belts do undergo accelerations and those accelerations cannot be isolated from the flat parts of the belt.

I have $1000 that says the cart doesn't behave any differently on an ordinary treadmill vs a medical one (running at the same speed and incline of course).

Add to this the fact the belt is rotating in the IFOR that the carteers have chosen for their reference frame, and it is undeniable the rotational energy from the belt is frame invariant. The fact is, there are more differences than similarities, between a cart on a treadmill and a cart in the wind. Discounting all of those differences is what is leading you to accept the treadmill equivalency; and that is a big mistake as well as unscientific.

Nonsense. The part of the belt that is in contact with the cart is moving at a constant speed and a single direction at all times. It's a perfectly valid frame of reference, and the rotation at the ends of the belt has nothing to do with anything.

 

[mender]

What I did compare was the treadmills themselves, making the observation that the modified "force treadmill" largely eliminates belt variations due to the belt itself (with nobody walking on it) going around the end cylinders. The variations would be tiny, and are of no concern during normal treadmill usage, but may be large enough to influence the behaviour of the equally tiny cart on the belt. It is possible that very slight back and forth accelerations on the belt may act in the manner of a vibratory conveyor, in sending the cart up the belt. It is a possibility that cannot be discounted.

But easily tested; just take off the prop that is causing all the losses and see how much faster the cart goes up the belt.