Merged DDWFTTW in a “Real” Wind

[Subduction Zone]

Sorry humber, out of the vast crowds that debate this topic only two deniers claim that the treadmill is not equivalent to the cart running on the road at wind speed. You have proven nothing and your continued running away from actual debate shows that you know that you are wrong.

 

[Llyricist]

I did not ask you for net force. If you like I can show you how to increase net force bt reducing efficiency, but I asked

"And if you want to see the consequences of your own math, calculate how much power it takes JB to push the cart to WS, ( or 1mph above it) and then do it using the prop. "

As soon as you explain the relevance of that calculation to the supposed "problem" you found with Drela's math I'll explain, again, why all my calculations are above wind speed.

 

[ThinAirDesigns]

And by the way, the ratchet was not operational during the trial as you claimed.

Another lie of course.

JB

 

[Giordano]

From your reasoning, If there are 60N forces acting on the cart in the vertical direction, we should expect to see the following from F=MA:

60N=0.2A

A=300 m/s**2 or approximately 30gs +z direction-1g for earth's gravity acting on the cart in the -z direction or vertically over the belt since there is nothing to prohibit this acceleration other than the weight of the cart.

Since we do not see the carts rocketing off the belts vertically at 29 gs acceleration, I would think you might want to check the credibility of this claim.

If you want to use math to justify physics outcomes, first you must be able to understand what the equations are telling you!

ETA: I went back and look and you stated 80N in the vertical direction for force. This translates to approximately 39 vertical gs for acceleration!

Windgrins: I've been curious about this quote of 60 to 80 N of noise in a treadmill belt. My wife weighs approximately 45 kilograms. 80N would mean an acceleration of 1.8 meters/s^2, or almost 1/5 of a g orthogonal to the direction of travel of the belt. If this is the noise in the system, am I correct that this would vary from 1/5 g up to 1/5 g down, and every value in between? How could any one walk or run under these conditions? If this was true of the average treadmill, people would be swept off their feet every few minutes at every gym and spa. It would be like running on a small boat deck in an intensely choppy sea. Or have a made an error in my interpretation?

 

[humber]

Another lie of course.

JB

Have it your way. But I have your confirmation.

 

[humber]

It's one of humber's standard tactics: Proof by insult. If he calls the small cart a toy, or the BB a "rolling junkyard", he doesn't have to account for the fact that both work exactly as claimed.

That's because both are examples of mechanical ineptitude. Badly designed and constructed, and subject to repeated breakages until the component size is increased until that stops. The latter is passed off as being the result of "the torque of a Corvette". That translates to 8000N at the wheel, and so a ridiculous claim to cover the real cause of the failures.

 

[Subduction Zone]

And humber still does not understand as simple of a concept as torque.

 

[humber]

As soon as you explain the relevance of that calculation to the supposed "problem" you found with Drela's math I'll explain, again, why all my calculations are above wind speed.

And that conclusion about the power is what you went out of your way to avoid, and are still doing.

Explain how 1.8W drives the cart to the rising speeds, against a falling opposing drag, when your own calculations are based upon both the prop power and drag forces rising with speed.
You would not want to contradict Dr Drela.


Prop power = 1.8W

Belt = 5m/s
Net = 1N - 0.36N = 0.64N
(Power demand 5m/s*1N = 5W)

Belt = 10m/s
Net = 1N - 0.18N = 0.82N
(Power demand 10m/s*1N = 10W)

Belt = 20m/s
Net = 1N - 0.09N = 0.91N
(Power demand 20m/s*1N = 20W)

Belt = 100m/s
Net = 1N -.018N = .982N.
(Power demand = 100m/s*1N = 100W)

 

[Subduction Zone]

humber, the different belt speeds represent different wind speeds. Do we need to go through the Galilean transformations again? Most people see it perfectly reasonable that a wind with a higher velocity can give more energy to an object.

 

[Llyricist]

And that conclusion about the power is what you went out of your way to avoid, and are still doing.

Explain how 1.8W drives the cart to the rising speeds, against a falling opposing drag, when your own calculations are based upon both the prop power and drag forces rising with speed.
You would not want to contradict Dr Drela.


Prop power = 1.8W

Belt = 5m/s
Net = 1N - 0.36N = 0.64N
(Power demand 5m/s*1N = 5W)

Belt = 10m/s
Net = 1N - 0.18N = 0.82N
(Power demand 10m/s*1N = 10W)

Belt = 20m/s
Net = 1N - 0.09N = 0.91N
(Power demand 20m/s*1N = 20W)

Belt = 100m/s
Net = 1N -.018N = .982N.
(Power demand = 100m/s*1N = 100W)

Because in the real cart, the omega and airspeed increase with speed, while the wheel size stays the same. In your example the omega and airspeed stay the same, and the wheel size changes.

Apples and oranges.

 

[humber]

humber, the different belt speeds represent different wind speeds. Do we need to go through the Galilean transformations again? Most people see it perfectly reasonable that a wind with a higher velocity can give more energy to an object.

The belt speed represents both the wind and cart speed.

 

[humber]

Because in the real cart, the omega and airspeed increase with speed, while the wheel size stays the same. In your example the omega and airspeed stay the same, and the wheel size changes.

Apples and oranges.

That does not matter. You have no reason to think that the 5m/s is the "correct" wheel size of AV.
The model predicts that if that AV is kept constant, the cart can travel at any speed, on that same AV. A variable transmission could replace the wheel size change.
If you try that or changing the wheels in your calculations, you will not reach the same conclusion, neither over power or net force.
Try again at the coconut shy of certain failure. Much simpler to realise that you have fallen for the remonstrations of two individuals, who's technical skill is less than average.

 

[Llyricist]

That does not matter. You have no reason to think that the 5m/s is the "correct" wheel size of AV.
The model predicts that if that AV is kept constant, the cart can travel at any speed, on that same AV. A variable transmission could replace the wheel size change.
If you try that or changing the wheels in your calculations, you will not reach the same conclusion, neither over power or net force.
Try again at the coconut shy of certain failure. Much simpler to realise that you have fallen for the remonstrations of two individuals, who's technical skill is less than average.

You are clueless, the calculation you did is no different than what would happen with mine if I changed the wheel size or gearing to keep the omega constant at different ground speeds with airspeed at 0.

 

[Subduction Zone]

The belt speed represents both the wind and cart speed.

humber actually got something right

Does he realize that a faster belt speed means a faster air speed which means much more energy is available? Since energy and air speed has a quadratic relationship doubling the air speed means there is four times the available energy in the wind. If it is ten times higher there is one hundred times the amount of energy available.

 

[humber]

Windgrins: I've been curious about this quote of 60 to 80 N of noise in a treadmill belt. My wife weighs approximately 45 kilograms. 80N would mean an acceleration of 1.8 meters/s^2, or almost 1/5 of a g orthogonal to the direction of travel of the belt. If this is the noise in the system, am I correct that this would vary from 1/5 g up to 1/5 g down, and every value in between? How could any one walk or run under these conditions? If this was true of the average treadmill, people would be swept off their feet every few minutes at every gym and spa. It would be like running on a small boat deck in an intensely choppy sea. Or have a made an error in my interpretation?

That's easy. Windgrins has made another mistake, but the matter is more general. The Earth is not quite an IFOR, but the effects of that small difference are also small. If you conduct experiments on the ground that are not sensitive enough to record the effects of those differences, and then do the same on a moving ship, that is also not quite an IFOR, and again do not note the tiny differences, you may conclude that the conditions are exactly the same.
Well, they are. Both show the same but ignored effects. However, you may find that sometimes when on a ship, the effects are large enough to produce sea-sickness.
TM belt is nothing like a ship, nor the ground, and the effects of it not being an IFOR are large.

 

[Llyricist]

humber actually got something right

Does he realize that a faster belt speed means a faster air speed which means much more energy is available? Since energy and air speed has a quadratic relationship doubling the air speed means there is four times the available energy in the wind. If it is ten times higher there is one hundred times the amount of energy available.

Careful with the terminology, that will only confuse him further. When I have used the term airspeed, I am not talking about the speed of the wind over the ground, but you were.

 

[humber]

Careful with the terminology, that will only confuse him further. When I have used the term airspeed, I am not talking about the speed of the wind over the ground, but you were.

When stationary at "WS" the cart speed relative to the ground is the same as the wind speed relative to the ground. The cart is travelling over the ground at the same speed as the wind.

This still remains:

The model predicts that if that AV is kept constant, the cart can travel at any speed on that same AV. A variable transmission could replace the wheel size change.
( I said earlier that the gearing did nothing but change the effective wheel size, and so the gearing could be ignored in the power calculation, and you agreed)

If you try that gearbox or changing the wheels in your calculations, you will not reach the same conclusion as for TM, neither over power or net force.

The TM is not a predictor of wind performance.

 

[profpangloss]

From your reasoning, If there are 60N forces acting on the cart in the vertical direction, we should expect to see the following from F=MA:

60N=0.2A

A=300 m/s**2 or approximately 30gs +z direction-1g for earth's gravity acting on the cart in the -z direction or vertically over the belt since there is nothing to prohibit this acceleration other than the weight of the cart.

Since we do not see the carts rocketing off the belts vertically at 29 gs acceleration, I would think you might want to check the credibility of this claim.

If you want to use math to justify physics outcomes, first you must be able to understand what the equations are telling you!

ETA: I went back and look and you stated 80N in the vertical direction for force. This translates to approximately 39 vertical gs for acceleration!

Now you are trying to be funny? No one has claimed that the 60 N forces are acting directly on the cart. What has been established from this research is there are ground reaction forces of 60 N in all three spatial directions, measured in the force platform that is supporting the treadmill. These are essentially vibrations in specific frequency spectrums and they will most certainly be present on the treadmill belt, but exactly to what extent is unknown. It is also unknown to what exact extent they will have an effect on the cart, or in what manner that effect will be manifest.What is known is that these vibrations are present and since they are of a substantial magnitude, it would be disingenuous to discount their effect on a cart that weighs less than 200 grams and is very loosely coupled to the belt.

You cannot claim that you have performed a valid, scientific Galilean transformation of the cart on a treadmill to the situation of a cart on a road in the wind, unless you have included a transform of these vibration forces. That is the entire point; your transform is incomplete and inaccurate and invalid.

You cannot pick and choose what forces you would like to include and what you would like to exclude because you may be overlooking something that has an important effect on the cart. If you perform only a velocity transform of the cart on a treadmill, that can only result in a situation with a cart that is still on a running treadmill with the velocities transformed, and nothing else, unless you can transform all of the forces that are acting, and you have no way of doing that.
This is not a matter of opinion. Your transform will not be accepted by any scientific body or get past any peer review. You may have some success peddling it on Internet talk forums, but that is as far as it will ever go.

 

[Subduction Zone]

What vibrations ppg? Don't compare the vibrations caused by a runner hitting the track with his feet to whatever vibrations there might be from an object rolling smoothly on the treadmill. Once again you have made a claim it is up to you to provide evidence for it.

 

[profpangloss]

Wrong again ppg. All real forces were analyzed and transformed. You want to try to transform imaginary forces. If there is a force that we are not analyzing it is up to you to prove that force exists and how it affects the cart. And your error ridden energy analysis has been shot down many times over. I see that you are still running away from the force analysis challenge.

That is a lie. The vibration forces are real and can be easily measured with strain gauges and recorded as was done in the research I referenced. At no time have you taken any of these forces into consideration in your simplified velocity transform. I do not have to prove how these forces affect the cart on the treadmill. All I need to do is what I have done; reference sources that show these forces are present and that your velocity transform is invalid.