profpangloss
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Read the paper I referenced. The vibrations are present when the motor is turned on and no subject is on the treadmill. They are inherent in the treadmill itself.
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Merged DDWFTTW in a “Real” Wind
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Read the paper I referenced. The vibrations are present when the motor is turned on and no subject is on the treadmill. They are inherent in the treadmill itself.
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.
Why would anyone bother to try and discuss nonsense like this with someone that's clearly not willing to have an honest discussion?
Read the paper I referenced. The vibrations are present when the motor is turned on and no subject is on the treadmill. They are inherent in the treadmill itself.
They will be there for all sorts if reasons. The tension in the top of the belt will not be the same as the bottom, because gravity will act on one, but the base plate acts on the other. Generally, the length of belt is longer on the underside.
If the motor's speed is controlled by phase-chopping, that too will appear as accelerations of the belt.
This video show how tenuously the cart is attached to the belt. It is barely stable without the fan, but the fan which is held at a distance, blows it off the end of the belt.
http://www.youtube.com/watch?v=rb_4q2LSRsM
The Carteers don't like the claim that the tailwind turns the rotor CW, so is an opposing force. The "failed upwind cart" really gets to them.
Wind turbines are controlled to face the wind, so as to maximize output. That output falls when the turbine is at an angle to the wind, and likewise, the cart benefits from not being ddw, because the opposing turbine force falls. That can be seen in this video.
http://img52.imageshack.us/img52/2677/5o3.mp4
Why would anyone bother to try and discuss nonsense like this with someone that's clearly not willing to have an honest discussion?
I don't have any crayons to hand, but if you would like to start, please go ahead.
The TM is likely to be affected by vibration, but can be part of the process and not necessarily the entire process. The first belt material I used was heavy pool liner vinyl. That stretched too much, and even a simple wheeled cart would be twisted by the variation across the belt. - a possible source that could drive the cart, but I did not try that.
I now use a composite laminated paper. That does not show that effect and all runs smoothly.
The TM is a simple problem to solve. If a mass is placed on the belt, it is accelerated away with the belt, and gains KE wrt the ground observer. The cart at "WS" has no KE wrt the ground observer.
To bring that moving mass to rest, get rid of that linear KE. That can be done by some means of transfer, but if there is still friction to the belt, the belt will again accelerate the object and put it back. Solve both problems by transferring the linear KE to angular KE, and so to another frame, and use wheels to lower the friction, so the belt can't replace it.
That all happens when first held by the hand. The rest, including the above WS motion, are spurious or additional effects.
In other words the cart does not in any way travel, but avoids being dragged by the belt. Drela's method alone shows that the same process is largely independent of belt speed. The only power required, is that to run the avoidance mechanism - which includes the thrust - and that takes very little power.
I now use a composite laminated paper. That does not show that effect and all runs smoothly.
The TM is a simple problem to solve. If a mass is placed on the belt, it is accelerated away with the belt, and gains KE wrt the ground observer. The cart at "WS" has no KE wrt the ground observer.
To bring that moving mass to rest, get rid of that linear KE. That can be done by some means of transfer, but if there is still friction to the belt, the belt will again accelerate the object and put it back. Solve both problems by transferring the linear KE to angular KE, and so to another frame, and use wheels to lower the friction, so the belt can't replace it.
That all happens when first held by the hand. The rest, including the above WS motion, are spurious or additional effects.
In other words the cart does not in any way travel, but avoids being dragged by the belt. Drela's method alone shows that the same process is largely independent of belt speed. The only power required, is that to run the avoidance mechanism - which includes the thrust - and that takes very little power.
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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.
So what you are saying (if you don't mind me making an attempt at interpretation), is that an object in contact with the belt, resting on it as it moves along, is likely to be subject to accelerations along that (x) direction. Moreover it will be subject to these accelerations in z, and y.
You say they measured these accelerations as forces, using strain gauges. So, they had an average commercial grade treadmill running, and they measured reaction forces developed between the chassis and the floor, is that right?
But what you cannot say, is what the nature of these accelerations is with regard to an object on the belt, nor if there is any significance to that on the performance of the cart. What is the acceleration characteristic (i guess it is periodic, but what sort of shape, magnitude etc) of the belt when set at "steady" speed? How would that affect various objects on the belt? Would a cube of some particular mass and friction be likely to skid and bounce?
What we do see, is a nice smooth cart operation driving along the belt. What we do not see is a cart operating in this manner with no propeller, nor jumping up and down, nor suddenly side to side.
Astonishingly, the characteristics we see of the cart on the belt are exactly the same as those of the BB on the desert floor.
Is this a reasonable presentation of your "case"?
profpangloss
Critical Thinker
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So what you are saying (if you don't mind me making an attempt at interpretation), is that an object in contact with the belt, resting on it as it moves along, is likely to be subject to accelerations along that (x) direction. Moreover it will be subject to these accelerations in z, and y.
That is correct. The forces were measured at 60 N in the hor and lateral directions and 80 N vertically. Those are significant forces when you consider the cart has a mass of 0.2 kg resulting in a force of only 2 N on the belt vertically and much much less than that horizontally and laterally.
You say they measured these accelerations as forces, using strain gauges. So, they had an average commercial grade treadmill running, and they measured reaction forces developed between the chassis and the floor, is that right?
The strain gauges were mounted in a lab-quality force platform. The treadmill itself was custom made with precision machined rollers to reduce vibration. The vibrations from this treadmill should have been considerably less than what you would expect to find on an ordinary consumer grade treadmill. Having said that, I see where the flywheel was a large pulley and not a precision machined and precision balanced flywheel. They admit that in the paper and admit that a large fraction of the vibration forces was most likely due to not having a precision flywheel. I found that to be somewhat baffling, that they would go to all the trouble of using custom machined rollers and then put a pulley on as a flywheel. Very sloppy work, in my opinion, but even so the vibrations should be less than what is found on an ordinary treadmill.
But what you cannot say, is what the nature of these accelerations is with regard to an object on the belt, nor if there is any significance to that on the performance of the cart. What is the acceleration characteristic (i guess it is periodic, but what sort of shape, magnitude etc) of the belt when set at "steady" speed? How would that affect various objects on the belt? Would a cube of some particular mass and friction be likely to skid and bounce?
I cannot say what the level of disturbance is to the cart nor how it would affect the cart. All I can say is what I did say; that the vibrations will certainly be present on the belt to some degree and they may have a significant roll to play in how the cart moves on the treadmill. a mass of only 200 grams on the belt would certainly "feel" vibrational forces on the treadmill frame of 60 N.
What we do see, is a nice smooth cart operation driving along the belt. What we do not see is a cart operating in this manner with no propeller, nor jumping up and down, nor suddenly side to side.
You cannot say that the operation is smooth. How do you make that determination? There are conveyors that work on vibration alone. Here the cart does have a propeller as well as vibrations. Can you make assurances that the combination of spinning the propeller up to maximum speed on the belt and then having both the thrust and the vibrations working together will not allow the cart to advance on the belt? How do you know the cart is not skipping on the belt without at least doing some tests to ensure it isn't? You cannot trust only what you want to see and what you want to believe.
Astonishingly, the characteristics we see of the cart on the belt are exactly the same as those of the BB on the desert floor.
It is astonishing that you make such a claim! As I said earlier, if you scale up those forces to the same scale as a 200 kg cart, somewhere beneath the desert floor there would be vibration forces of 60,000 N. I think even the big cart would be seen to be hopping with those sorts of forces in play.
Is this a reasonable presentation of your "case"?
I would say your presentation was anything but reasonable and only reflects your bias. You might try looking at this more scientifically and with less emotion.
profpangloss
Critical Thinker
- Joined
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The TM is likely to be affected by vibration, but can be part of the process and not necessarily the entire process. The first belt material I used was heavy pool liner vinyl. That stretched too much, and even a simple wheeled cart would be twisted by the variation across the belt. - a possible source that could drive the cart, but I did not try that.
I now use a composite laminated paper. That does not show that effect and all runs smoothly.
The TM is a simple problem to solve. If a mass is placed on the belt, it is accelerated away with the belt, and gains KE wrt the ground observer. The cart at "WS" has no KE wrt the ground observer.
To bring that moving mass to rest, get rid of that linear KE. That can be done by some means of transfer, but if there is still friction to the belt, the belt will again accelerate the object and put it back. Solve both problems by transferring the linear KE to angular KE, and so to another frame, and use wheels to lower the friction, so the belt can't replace it.
That all happens when first held by the hand. The rest, including the above WS motion, are spurious or additional effects.
In other words the cart does not in any way travel, but avoids being dragged by the belt. Drela's method alone shows that the same process is largely independent of belt speed. The only power required, is that to run the avoidance mechanism - which includes the thrust - and that takes very little power.
Yes, it is a combination of thrust plus vibrations to break the traction that would pull the cart backwards. It seems simple but to express it all in a mathematical equation is difficult, to say the least.
I cannot say what the level of disturbance is to the cart nor how it would affect the cart. All I can say is what I did say; that the vibrations will certainly be present on the belt to some degree and they may have a significant roll to play in how the cart moves on the treadmill. a mass of only 200 grams on the belt would certainly "feel" vibrational forces on the treadmill frame of 60 N.
Right, but this 60N is just a reaction force to the floor. It does indeed seem excessive for a well designed piece of equipment, quite strange.
But regardless of that, I just don't see how such an imbalance is going to affect the motion of the belt, given the machine is constrained to the floor.
Lets imagine a treadmill with a purposely imbalanced roller, like a sledge hammer bolted on the roller by the handle, with the head a few feet off axis.
That thing will cause terrible forces to stress the mounts and the bearings, but will it necessarily change the belt speed as it goes around? Only due to gravity force on the hammer head alternately assisting and loading the motor but depending rather a lot on the type of motor, motor controller, gearing and overall system mass properties. You could put the same imbalance on the opposite roller 180 degrees out of phase and balance that effect while still torturing the mounts and bearings. In other words, the imbalance causing mounting stresses, won't necessarily translate to belt accelerations.
What is more, every design of treadmill will be different, and a cart would have to be tuned to each specific treadmill to work, unless it turned out that the much simpler and more logical explanation as offered by the carteers was the real driving mechanism.
ETA: Is that really all you've got?
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Careful with the terminology, that will only confuse him further.
Hmmm, interesting.
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.
What complete nonsense. The old ppg straw man again. It reminds me of Humber talking about crosswinds and invisible sails. The compounded absurdity of their arguments actually helps them generate responses. If the argument was merely ridiculous instead of completely insane the debate would be shorter.
Because the crosswinds could not have helped even a cart that had a sail we are drawn in to proving that fact instead of focusing on the fact that the cart actually has no sails.
The cart has no mechanism by which it could take advantage of any vibrations present even if they were significant, which they are not. Sounds familiar.
ppg is saying the transform is invalid because not all forces were taken into account which is complete and utter nonsense. No analysis ever takes into account all the forces present in a system. It just needs to account for all the relevant ones. There are always thousands upon thousands of negligible forces present that we can ignore by virtue of the fact that we are not stupid. The cart is also not significantly influenced by static electricity, magnetism, quantum entanglement, pressure differences, gravity fluctuations, photon sails or temperature gradients just to name a few.
Because his math was shown to prove the opposite of what he thought it did he has been reduced to talking about foolishness like "vibrations". Its embarrassing ppg, I know you can do better. Why not talk about Spork's psychokinetic abilities. At least that would be a little bit less silly.
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Apples and Oranges.
Since the author of the paper did not state how the TM measured was instrumented its a little difficult to state what and how they were measuring the frame. After reading the paper what did become clear was that the high g measurements were high frequency vibrations starting around 45 Hz and plotted as being higher with higher frequency. This frequencies are higher than low "bass" notes on a stereo system (20 Hz considered the threshold of hearing) and the author called it "noise" transients. The expectation is that any high frequency vibration (from a mechanical point of view) would be typically sinusoidal and would be considerably diminished via the elastomeric (rubber) tread and rubber wheels of any device on a TM. The author did state they excited the frame with a hammer (normal practice) to obtain transient response. Basically an impulse has frequency components from dc to infinity and this will normally excite any natural resonant frequency components of the TM frame. The assumption is that the author of the cited paper was placing their transducers on the frame and seeing this "ringing". I was initially surprised at the plot showing the magnitude increasing for higher frequencies but then I read the scale and saw it was the integrated power which shows most of the noise is at higher frequencies than the ones of interest. For their use, the simply low pass filtered the data as they did not consider the high frequency noise as important to their measurements of gait analysis. The use of the word "noise" by the authors indicate that it is uncorrelated and random and not a consistent vibration. In the graph in their paper, a true resonance will appear as a step function in the integral as a lot of energy is contained there. They note their first resonances are near 90 Hz which corresponds to that step but they don't mention anything about the one at about 73 Hz so I'm not sure what that is. Noise can occur from transducer placement, type and nature of the coupling of the transducers, electrical noise in the amplifiers and other ambient noise sources so it is difficult to know what the "mat" of their TM transmitted without more info. They were trying to characterize their noise from the motors, flywheels, etc. to be able to separate it from actual signals from a person walking on the TM.
So to answer your question, the assumption is that the authors measured the values on the steel frame of the TM where their force transducers were and the forces were indeed vibrational in nature of low amplitude in the steel frame and it is not clear how they coupled into their "mat" or belt. In essence, not a whole lot can be gleaned without putting a vibration transducer on the belt itself for our purposes and as you can imagine this is difficult due to the rotating nature of the belt. One could do this "hammer test" on the frame with the non-rotating belt to understand the coupling but this was not done or discussed in this paper.
For our purposes, what is important is that there is a no-slip condition on the wheels. This is ascertained in Video #6 as earlier stated. Any vibrations that don't have the ability to cause any slip can't transport the cart since they don't lose contact with the surface. The hypothesis is a red-herring that isn't consistent with the evidence presented. One of the interesting things to note is that the experiment was not done to ascertain the noted non-slip condition so fraud or trickery would not be normally considered in the subtly of my observation of the smoothly and continuously aliased wheel spokes in video #6. The other interesting observation is that the cart wonders from equilibrium and there is little net tendency to go up or down TM but when the speed is slightly increased it always goes up and when reduced it always goes down TM. This is consistent with carteer's standard theory of operation but not the denier's vibration hypothesis.
On my final note on this, the paper chosen has limited applicability due to the author's intent having little to do with our subject matter, so generalizations from the paper to our topic have to be carefully considered for any meaningful conclusions. There is one generalization the author makes which is meaningful in the discussion session which is in opposition to the fundamental assertion of the deniers about TMs and reference frames (my italics and underline).:
"From a purely mechanical perspective, steady-speed
walking or running on an adequate motorized treadmill
is identical to overground walking and running; the
only difference is the frame of reference for each
situation (23). Locomotion on a treadmill with inadequate power or momentum (i.e., no flywheel) does
indeed differ from overground locomotion. However, on
a treadmill with an adequate motor and flywheel,
where the belt speed does not vary, the kinematics (21),
ground-reaction forces (19), and metabolic cost (2) of
locomotion are nearly indistinguishable from overground locomotion. As detailed above, our motor and
flywheel appear to be adequate in maintaining a constant tread speed."
Hopefully this helped but it is difficult to use this "apples" paper to discuss our "oranges". It is clear our opponents are "grasping at straws" and "cherry picking" to try to find some solace while ignoring the 500 lb gorillas in their own citations of papers. They either don't seem to understand the significance of the giant contradictions to their claims in their papers or are just ignoring them.
Regards,
WindGrins
The paper is a bit dry but I include a link so you know what I'm basing my answers about it on.
Here is the link to the paper:
http://jap.physiology.org/content/85/2/764.full.pdf
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?
Since the author of the paper did not state how the TM measured was instrumented its a little difficult to state what and how they were measuring the frame. After reading the paper what did become clear was that the high g measurements were high frequency vibrations starting around 45 Hz and plotted as being higher with higher frequency. This frequencies are higher than low "bass" notes on a stereo system (20 Hz considered the threshold of hearing) and the author called it "noise" transients. The expectation is that any high frequency vibration (from a mechanical point of view) would be typically sinusoidal and would be considerably diminished via the elastomeric (rubber) tread and rubber wheels of any device on a TM. The author did state they excited the frame with a hammer (normal practice) to obtain transient response. Basically an impulse has frequency components from dc to infinity and this will normally excite any natural resonant frequency components of the TM frame. The assumption is that the author of the cited paper was placing their transducers on the frame and seeing this "ringing". I was initially surprised at the plot showing the magnitude increasing for higher frequencies but then I read the scale and saw it was the integrated power which shows most of the noise is at higher frequencies than the ones of interest. For their use, the simply low pass filtered the data as they did not consider the high frequency noise as important to their measurements of gait analysis. The use of the word "noise" by the authors indicate that it is uncorrelated and random and not a consistent vibration. In the graph in their paper, a true resonance will appear as a step function in the integral as a lot of energy is contained there. They note their first resonances are near 90 Hz which corresponds to that step but they don't mention anything about the one at about 73 Hz so I'm not sure what that is. Noise can occur from transducer placement, type and nature of the coupling of the transducers, electrical noise in the amplifiers and other ambient noise sources so it is difficult to know what the "mat" of their TM transmitted without more info. They were trying to characterize their noise from the motors, flywheels, etc. to be able to separate it from actual signals from a person walking on the TM.
So to answer your question, the assumption is that the authors measured the values on the steel frame of the TM where their force transducers were and the forces were indeed vibrational in nature of low amplitude in the steel frame and it is not clear how they coupled into their "mat" or belt. In essence, not a whole lot can be gleaned without putting a vibration transducer on the belt itself for our purposes and as you can imagine this is difficult due to the rotating nature of the belt. One could do this "hammer test" on the frame with the non-rotating belt to understand the coupling but this was not done or discussed in this paper.
For our purposes, what is important is that there is a no-slip condition on the wheels. This is ascertained in Video #6 as earlier stated. Any vibrations that don't have the ability to cause any slip can't transport the cart since they don't lose contact with the surface. The hypothesis is a red-herring that isn't consistent with the evidence presented. One of the interesting things to note is that the experiment was not done to ascertain the noted non-slip condition so fraud or trickery would not be normally considered in the subtly of my observation of the smoothly and continuously aliased wheel spokes in video #6. The other interesting observation is that the cart wonders from equilibrium and there is little net tendency to go up or down TM but when the speed is slightly increased it always goes up and when reduced it always goes down TM. This is consistent with carteer's standard theory of operation but not the denier's vibration hypothesis.
On my final note on this, the paper chosen has limited applicability due to the author's intent having little to do with our subject matter, so generalizations from the paper to our topic have to be carefully considered for any meaningful conclusions. There is one generalization the author makes which is meaningful in the discussion session which is in opposition to the fundamental assertion of the deniers about TMs and reference frames (my italics and underline).:
"From a purely mechanical perspective, steady-speed
walking or running on an adequate motorized treadmill
is identical to overground walking and running; the
only difference is the frame of reference for each
situation (23). Locomotion on a treadmill with inadequate power or momentum (i.e., no flywheel) does
indeed differ from overground locomotion. However, on
a treadmill with an adequate motor and flywheel,
where the belt speed does not vary, the kinematics (21),
ground-reaction forces (19), and metabolic cost (2) of
locomotion are nearly indistinguishable from overground locomotion. As detailed above, our motor and
flywheel appear to be adequate in maintaining a constant tread speed."
Hopefully this helped but it is difficult to use this "apples" paper to discuss our "oranges". It is clear our opponents are "grasping at straws" and "cherry picking" to try to find some solace while ignoring the 500 lb gorillas in their own citations of papers. They either don't seem to understand the significance of the giant contradictions to their claims in their papers or are just ignoring them.
Regards,
WindGrins
The paper is a bit dry but I include a link so you know what I'm basing my answers about it on.
Here is the link to the paper:
http://jap.physiology.org/content/85/2/764.full.pdf
Why not talk about Spork's psychokinetic abilities. At least that would be a little bit less silly.
No, it wouldn't.
And your remarks are as always general denial, personal, childish, and without a shred of math or technical input. As far as I am concerned you are a follower, following for the sake
of following.
The TM is not a model of a cart in the wind, and none of the calculations obtained from it can be applied to the cart, and the cart's math demands more energy from the wind than is available.
Perhaps you can as Llyricist why calculating the energy required to push the cart to WS, and using the prop, is causing him so much bother.
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No, it wouldn't.
Are you saying that you believe that talking about "vibrations" is more silly than talking about psychokinesis or are you saying that Spork did move the cart up the belt with his mind?
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.
This is total nonsense. If the ship is on flat water moving at a steady speed, it is equivalent. When the boat is rolling, pitching yawing, surging, heaving, and swaying in troubled seas is clearly not equivalent. These concepts have zero to do with why the earth and the ship is not a true IRF. If so, you would be motion sick when sitting still on the ground.
You are not making any sense. I guess desperation does this.
WindGrins
The TM is not a model of a cart in the wind, and none of the calculations obtained from it can be applied to the cart,
I agree that to call it a model of a cart in the wind probably understates the reality. It should be called an instance of a cart in the wind since the two are indistinguishable in all relevant ways.
and the cart's math demands more energy from the wind than is available.
No Humber, it doesn't. You have made a mistake. If you need me to post links to some of the posts in which you were corrected let me know.
Perhaps you can as Llyricist why calculating the energy required to push the cart to WS, and using the prop, is causing him so much bother.
How the cart got to WS is completely irrelevant and I have not seen any evidence of the props energy calcs causing him any bother so asking him that question would not make any sense. I will be happy to ask him questions for you but you will have to elaborate on what you mean.
Read the paper I referenced. The vibrations are present when the motor is turned on and no subject is on the treadmill. They are inherent in the treadmill itself.
Nonsense. Didn't you notice that they hit it with a hammer (as stated in the paper) to excite the vibrational modes. This is standard impulse response characterization and standard practice.
And for your other point: We can ignore certain forces and all forces don't have to be transformed. We do this when we say the earth's surface is a valid reference for an IRF. When we ignore the 500 lb gorilla of gravity in the z direction and state that experiments are rotation invariant in the x and y planes we are doing just that. Try turning a grandfather clock on its side and see how well it runs as an example. When we are ignoring the false force of Coriolis effects, we are doing just that. You have to display some intelligence when you are doing physics. The high frequency vibrations on the TM frame which aren't transmitted into the belt is a good example of where discretion is appropriate.
WindGrins
"From a purely mechanical perspective, steady-speed
walking or running on an adequate motorized treadmill
is identical to overground walking and running; the
only difference is the frame of reference for each
situation (23). Locomotion on a treadmill with inadequate power or momentum (i.e., no flywheel) does indeed differ from overground locomotion. However, on a treadmill with an adequate motor and flywheel,
where the belt speed does not vary, the kinematics (21),ground-reaction forces (19), and metabolic cost (2) of locomotion are nearly indistinguishable from overground locomotion. As detailed above, our motor and
flywheel appear to be adequate in maintaining a constant tread speed."
You should read more carefully. Running along an ideal treadmill, is indeed like running on the ground. Running on a large ship, is much like running on the ground. But, that is not the same as running in place when on a treadmill. There are countless references that will inform you of the differences.
Moreover, Dr Drela's calculations show that the TM can't be equivalent to a cart in the wind.
It is absolutely not necessary for the belt to have any acceleration or vibration to power the cart, as seen. In fact, imbalance in the cart itself, is likely to over shadow even a crude belt, and so provide the necessary stimulus for control of the wheel's contact to the belt. It is the prop's AV that is the primary means of control and that is governed by how much time is spends in contact with the belt.
It makes no difference to my cart, if I "short out" the isolation from the motor or not. Personally, I doubt the measurements given in that reference. A shaker table will perhaps be 12g RMS, and you certainly know about that if you stand on one.
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You cannot say that the operation is smooth. How do you make that determination? There are conveyors that work on vibration alone. Here the cart does have a propeller as well as vibrations. Can you make assurances that the combination of spinning the propeller up to maximum speed on the belt and then having both the thrust and the vibrations working together will not allow the cart to advance on the belt? How do you know the cart is not skipping on the belt without at least doing some tests to ensure it isn't? You cannot trust only what you want to see and what you want to believe.
For our purposes, what is important is that there is a no-slip condition on the wheels. This is ascertained in Video #6 as earlier stated. Any vibrations that don't have the ability to cause any slip can't transport the cart since they don't lose contact with the surface. The hypothesis is a red-herring that isn't consistent with the evidence presented. One of the interesting things to note is that the experiment was not done to ascertain the noted non-slip condition so fraud or trickery would not be normally considered in the subtly of my observation of the smoothly and continuously aliased wheel spokes in video #6. The other interesting observation is that the cart wonders from equilibrium and there is little net tendency to go up or down TM but when the speed is slightly increased it always goes up and when reduced it always goes down TM. This is consistent with carteer's standard theory of operation but not the denier's vibration hypothesis.
So, from your statements, we are to conclude the following:
One can't test a cart on a TM due to vibrations.
One can't test a cart in the wild due to fluctuating wind conditions.
So, since there is no test possible the cart can't be shown to be DDWFFTW capable in any situation at all.
There is no evidence possible to convince you that this can be tested. Why are you bothering to be here if this is the case?
Of if there is an environment where it can be tested that provably exists, please state it.
WindGrins
Like hell it is. The response also depends on the material's damping factor, and that is low in aluminum. Along with the imbalanced flywheel, I do wonder what this experiment hopes to prove.Nonsense. Didn't you notice that they hit it with a hammer (as stated in the paper) to excite the vibrational modes. This is standard impulse response characterization and standard practice.
I don't have any accelerometers to hand, but an electret microphone capsule should be a good enough indicator - as I am sure with you vast depth of knowledge, you can well appreciate.
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