it goes backwards quite a lot.
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Merged DDWFTTW in a “Real” Wind
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it goes backwards quite a lot.
That on is where a distant fan blows the cart off the belt. If not for being repeatedly stopped and replaced, it would be on the floor.
Ooops, that's Spork's claim.
The rear edges alone of the uprights, have half the blade area. You failed to mention that the wind is only measured at hub height, but the prop reaches 2.5m into the faster air above that.
A sail only needs much, much less energy than the prop cart.
Not really.
Winds shift by 100 degrees. dv/dt = a.
The same velocity wind, can provide force by chaging direction. NASA's Stever Smith thinks the changing winds could drive the cart, and not just that the wind is is not ddw. The wind changes, and is no ddw.
The turbine is there. When the chain comes off, the tailwind readily drives the prop CW. The turbine force does not drive the cart, but slows it. The cart would work better without the chain.
What you don't understand, you are force to ridicule.
The cart is pushed to WS, so gains energy that is not from the wind. That adds to the total KE, and so the final speed.
Roads don't have motors.
Yes, but NALSA were also cheated.
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Dave_46
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tobermoryphil
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But it takes stamina to do it for two years, eh, Humber?
nvidiot
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I didn't get a chance to view the vid at work (thanks very much optus, your 3G is just awesome
) but will check it out properly when I get home.But to clear something up, if a propellor is reversed, turned 180 around to face the other way, doesn't it provide a force that goes the other way? I'm sure I am just missing something there, but if the propellor is the force pushing the cart forward when running "normally", wouldn't reversing the cart make the force operate in the opposite way?
I mean, wouldn't it "pull" rather than "push"? But I have a feeling that I'm missing something there, and I'll check out the vid when I get to a decent connection to find out what that is.
Excellent observation. I wasn't sure anybody was even reading these!
Thanks,
WindGrins
I didn't get a chance to view the vid at work (thanks very much optus, your 3G is just awesome
But to clear something up, if a propellor is reversed, turned 180 around to face the other way, doesn't it provide a force that goes the other way? I'm sure I am just missing something there, but if the propellor is the force pushing the cart forward when running "normally", wouldn't reversing the cart make the force operate in the opposite way?
But I have a feeling that I'm missing something there, and I'll check out the vid when I get to a decent connection to find out what that is.
Since the wheels turn "backwards" in this configuration, the prop also turns "backwards". They are not quite as efficient in this mode but they are close enough to symmetrical to work fine, apparently. This "backwards mode" happens to be another nail in the coffin of the "vibration theory". but I doubt they will get this.
WindGrins
And yet, the video #6 still can be mined for "gold"! I watched the video very closely and made an observation that the other videos weren't as clear on before. With the TM set at a speed to hold the cart at a (near) fixed point, if one watches the "pinwheels" on the front wheels, they give a lot of info. These "pinwheels" are video aliasing but they do have an attribute that may not be obvious. When you see aliasing like this with a constant velocity device and a constant speed video, in essence, it acts like a constant frequency strobe. Constant Rate "pinwheels" (with very slow and mild deviations as the cart "wanders") imply a no slip condition or a very precise constant slip which is untenable. If slip occurred, one would see a jerky "pinwheel" speed change since the wheels have loading from the prop. This never occurs throughout the video indicating a "no slip" condition which negates one of the deniers favorite counter-explanations.
Here's the link for convenience:
http://www.youtube.com/watch?v=dgHBDESd38M&feature=related
Amusing and educational!
WindGrins
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profpangloss
Critical Thinker
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No, it is not wrong and the numbers are correct. You don’t even need to read the entire paper, here is the relevant part again:
In the given example, 70 N is approximately 10% of a subject’s body weight which is mg. So a person with a mass of 70 kg has a weight (force) on the treadmill of approximately 700 N and 10% of that is 70 N. That is the same magnitude as the “noise” forces recorded on the treadmill with no subject on the treadmill. In fact, in the vertical direction the noise was 80 N. The readings of 60 N in the horizontal and lateral directions degraded the signal/noise ratio during physiological testing with subjects on the treadmill.
We don’t need to get into the physiology here, only the kinematics of the treadmill itself. What matters in this discussion is that even with a custom-made treadmill with specially machined rollers, significant forces were measured in all three spatial directions.
It is not difficult to imagine that a 60 N force concentrated in the frequency spectrum between 46 to 86 Hertz can have some effects on a 200 gram cart that is loosely coupled to the treadmill belt. In fact, it is nonsensical to think that it would have no effect!
I do not need to prove what the effect is to discount the Galilean transform of the cart on a treadmill to a cart on a road in a wind. I only need to show that these forces are present on the treadmill and they have not been transformed to the situation of the cart on the road. That is more than enough to say that such a transform is incorrect, incomplete and invalid!
Not at all. When "backwards" like that, the rotor still accelerates the air down the belt, but over the front of the cart instead of to the rear. The cart is all but stationary wrt the air, so producing static thrust. The efficiency will be 10%, and the power much the same for both directions of the rotor rotation.
The "lawnmover" and "vibration" models have a great deal in common. It's really only a matter of circumstance as to which is the dominant effect.
There is nothing "difficult" about making a cart do what the TM cart does, and it can work under a wide range of conditions. Stability is the biggest problem, not power or thrust.
Show us one!
Agreed, we said the same thing.
Please illustrate where you came up with this 10% number for static thrust!
You are correct! The "great deal they have in common" is that neither work!
We would love for you to show us just one since its so easy. Balls in your cart! Please, please show us the reel mower going up the TM also. I can't wait for the video!
Windgrins
Agreed, we said the same thing.
Please illustrate where you came up with this 10% number for static thrust!
You are correct! The "great deal they have in common" is that neither work!
We would love for you to show us just one since its so easy. Balls in your cart! Please, please show us the reel mower going up the TM also. I can't wait for the video!
Windgrins
We need some fresh deniers.
I had a thought about using a turntable instead of a tread mill:
The wheels would have to be different sizes; inner one larger radius; perhaps 2 grooves cut into turntable...the cart would either advance; remain 'stationary', or retreat.
Would said hypothetical be a fair test, or cheating?
I had a thought about using a turntable instead of a tread mill:
The wheels would have to be different sizes; inner one larger radius; perhaps 2 grooves cut into turntable...the cart would either advance; remain 'stationary', or retreat.
Would said hypothetical be a fair test, or cheating?
With the small cart in the wind, you were shown a cart that was said to be doing something wonderous, but wasn't. The TM is the same.
This prop is like the prop on the TM cart, but smaller. The TM cart runs at 800rpm and the chart says ~200mW, 0.14N thrust and an efficiency of 10% or less for the static or near-static case. The belt drag will be 200mW/5ms-1
= 0.04N, which is value I calculated from watching the videos.
You are tempting fate in the hope that it won't be tempted.
Attachments
YNot's Circular Turntables
Quarky, are you referring to one like this?
http://www.youtube.com/watch?v=vvrf78dNihk
WindGrins
Quarky, are you referring to one like this?
http://www.youtube.com/watch?v=vvrf78dNihk
WindGrins
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Who said anything about the cart doing anything "wondrous"? The cart is just operating at its minimum speed in video #6. At this speed, the prop thrust has to match the "wheel drag". Otherwise it would accelerate either up or down.
According to the chart you just posted, thrust is maximized at whatever the lowest value is above 0 velocity. The efficiency is 0 since the formula doesn't work for that value. We've been over this before. You seem to be trying to infer that the thrust is 10% of the design point value which is nonsense. The thrust is a monotonically decreasing value in the range that it is measured with the maximum thrust at the lowest speed.
From your chart, what is obvious, is that the thrust (blue line) is maximized the closer it gets to the static thrust condition.
It's not obvious what you are trying to infer with your "efficiency number" but you've seen it stated multiple times that the prop efficiency formula doesn't work for static thrust.
Please strive for a little more clarity as it is very tough trying to decipher your points.
We welcome you demonstrating any of the proposed modes of cart functioning that you allege.
I like to live dangerously, tempt away!
WindGrins
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PPG-Dead vibration/acceleration/whatever theory!
Strangely Enough, I had not seen this video #7-Harold Bricer test before. I don't know how I missed this one.
It is the final nail in the coffin for PPG's "vibrations theory". The TM is running at a constant velocity and the cart goes up TM. When the control variable-headwind, changes, the cart no longer goes up TM and as the wind is varied, the carts ability to go up TM is impacted in direct relation to the wind as illustrated by the streamer.
If the vibration of the belt was the transport mechanism, this should not be influenced by this since the cart and belt are operating at the same speed and would have the same "vibration modes".
This is one dead theory at this point-Please let it RIP and not reappear as a zombie!
None of your objections have withstood scrutiny to date. So far they are clearly unworkable and nonsense.
You never really explained your lawnmower going up the TM theory of operation! I'd still love to see the video of it on the TM, however!
We welcome you demonstrating any of the proposed modes of cart functioning that you allege. It's up to you to show us differently.
I think you guys should, perhaps, question your math and physics skills unless you can show us one of your proposed carts going up TM as described by one of your theories. A lot of talk and no action! As the Texans say, "all hat, and no cattle!"
Strangely Enough, I had not seen this video #7-Harold Bricer test before. I don't know how I missed this one.
It is the final nail in the coffin for PPG's "vibrations theory". The TM is running at a constant velocity and the cart goes up TM. When the control variable-headwind, changes, the cart no longer goes up TM and as the wind is varied, the carts ability to go up TM is impacted in direct relation to the wind as illustrated by the streamer.
If the vibration of the belt was the transport mechanism, this should not be influenced by this since the cart and belt are operating at the same speed and would have the same "vibration modes".
This is one dead theory at this point-Please let it RIP and not reappear as a zombie!
None of your objections have withstood scrutiny to date. So far they are clearly unworkable and nonsense.
You never really explained your lawnmower going up the TM theory of operation! I'd still love to see the video of it on the TM, however!
We welcome you demonstrating any of the proposed modes of cart functioning that you allege. It's up to you to show us differently.
I think you guys should, perhaps, question your math and physics skills unless you can show us one of your proposed carts going up TM as described by one of your theories. A lot of talk and no action! As the Texans say, "all hat, and no cattle!"
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It is simply a toy on a belt. Not proof of ddw. Not something that you seem to think can't be done by several means, and without a prop. It's trivial.
Like the small cart and the BB. Nothing except for hyperbolic promotion.
You would not want to contradict Dr Drela, would you?
"P = sqrt[ T^3 / (2 rho pi) ] / (eta_h R)
T = thrust
rho = air density
pi = 3.14159
eta_h = hover figure of merit = hover efficiency ( = 0.8 typically)
R = rotor radius
F = P / V
V = 5 m/s = 11 mph (looks like the speed of the cart)
T = 1 N (102 grams)
R = 0.4 m
eta_h = 0.5 (assume crummy prop to be conservative)
rho = 1.2 kg/m^3
This gives the following prop shaft power P = 1.8W
The power-generating force on the wheels is:
F = P/V = 1.8 W / 5 m/s = 0.36 N
T_net = T - F = 1.0N - 0.36N = 0.64 N = 65 gram = 2.3 oz"
Change the belt to 10m/s. To keep the same prop AV, and so the same power, the wheel radius must be doubled. The force at the belt is then
1.8W/10ms = 0.18N
Net = 1N - 0.18N = 0.82N
Change that to 20m/s, and again double the wheel radius
1.8W/20ms = 0.09N
Net = 1N - 0.09N = 0.91N
All will work on the belt. So "proving" that the same 1.8W cart can travel at 5, 10, 20....m/s.
Then don't ask questions about static thrust, and then attribute your ignorance to me.
You do think it's magic.
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It's blown off the belt. That does not speak well of how it may do in the >WS headwind. Mender recently offered to show RP, that the cart would advance against the fan.
It's not my or Profpangloss's ideas that have problems, but the Carteers.
And you say you have experience in vibration analysis. Sure you do...
That's a good suggestion, humber, and that already seems to be the norm; people are quite willing to attribute your ignorance to you. But thanks for agreeing with that policy.
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