Merged DDWFTTW in a “Real” Wind

[windgrins]

Another fine example of "No knowledge whatsoever."

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.
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.

As usual Humber doesn't have a clue what he is talking about. Here's a web page describing exactly what I stated and the author of the paper stated that Humber thinks he knows something about but clearly illustrates he doesn't.

Humber, your credibility is so low we need a logarithmic scale to find it!

Exitation Hammers:

http://www.onosokki.co.jp/English/hp_e/products/keisoku/s_v/gk_series.html


From the web page cited:

GK series impulse hammer is an excitation hammer which is built in a sensor to measure a natural vibration frequency or perform modal analysis of a mechanical structure.

In addition to the GK-3100 for general purpose usage, the GK-2110 is an ultra compact type weighing of 4.8 g for excitation of small and light-weighted parts. For excitation of large structures such as automobile’s framework structure, the large type of the GK-4110G10 weighing of 1.1 kg is suitable. You can choose any one depending on your requirements.

By mounting an accelerometer on a measurement object and hitting it with impulse hammer, excitation force signals from an impulse hammer and response acceleration signals from an accelerometer are input to an FFT analyzer to enable measurement of the frequency response function (natural frequency). Moreover, you can perform modal analysis of the object by sending the obtained frequency response function data to a PC in which modal analysis software is installed.

 

[humber]

As usual Humber doesn't have a clue what he is talking about. Here's a web page describing exactly what I stated and the author of the paper stated that Humber thinks he knows something about but clearly illustrates he doesn't.

Humber, your credibility is so low we need a logarithmic scale to find it!

Exitation Hammers:

http://www.onosokki.co.jp/English/hp_e/products/keisoku/s_v/gk_series.html


From the web page cited:

GK series impulse hammer is an excitation hammer which is built in a sensor to measure a natural vibration frequency or perform modal analysis of a mechanical structure.

In addition to the GK-3100 for general purpose usage, the GK-2110 is an ultra compact type weighing of 4.8 g for excitation of small and light-weighted parts. For excitation of large structures such as automobile’s framework structure, the large type of the GK-4110G10 weighing of 1.1 kg is suitable. You can choose any one depending on your requirements.

By mounting an accelerometer on a measurement object and hitting it with impulse hammer, excitation force signals from an impulse hammer and response acceleration signals from an accelerometer are input to an FFT analyzer to enable measurement of the frequency response function (natural frequency). Moreover, you can perform modal analysis of the object by sending the obtained frequency response function data to a PC in which modal analysis software is installed.

I think you will find that is used as a rough guide, unless you have some means of calibrating the hitter. Even with the sensor in the hammer, angle of incidence, contact time and the damping effects of the hand, will influence the result. (And the authors used a wooden mallet)
Not a precision tool by any means. Once again. you have never been within 100 meters of any vibrational tests. Perhaps you can explain why turning on the motor produces forces of 80N, and the general noise level is apparently 3N. Perhaps they need to check the floor. Ever built a floating floor for sound isolation purposes windgrins? It is quite worrying as you watch 80m^3 of really hard to remove concrete being poured, and success or failure rests on your math.

 

[Llyricist]

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.

This is just wrong, it is the same calculation, so it will result in the same conclusion.

And the gearing DOES matter if you calculate the resistive force from the propeller from torque. ETA: and wheel size is part of the gearing, along with prop pitch, they ALL matter.

And that force will always be lower with higher ground speeds when the prop's demand remains the same. Whether calculated from power demand or torque demand.

 

[CORed]

I think you will find that is used as a rough guide, unless you have some means of calibrating the hitter. Even with the sensor in the hammer, angle of incidence, contact time and the damping effects of the hand, will influence the result. (And the authors used a wooden mallet)
Not a precision tool by any means. Once again. you have never been within 100 meters of any vibrational tests. Perhaps you can explain why turning on the motor produces forces of 80N, and the general noise level is apparently 3N. Perhaps they need to check the floor. Ever built a floating floor for sound isolation purposes windgrins? It is quite worrying as you watch 80m^3 of really hard to remove concrete being poured, and success or failure rests on your math.

So, did they deduct the cost of pouring and removing the concrete from your salary, or did they just fire you?

 

[windgrins]

Smartest comment all day.

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.

PPG, This is an intelligent comment except for the "seeming simple" part. If the cart were breaking traction, the non-linear behavior would be far from simple.

It is clear from Video #6 with the single speed aliasing effect throughout the video that the cart does not lose traction. Therefore the vibrations are not an issue that seem to be any sort of cause.

If the wheels break traction, the prop would very quickly change their speed due to the load which would be evidenced in this video as alias speed variations which are not present. The reason this video is so good is that it stays very stable at the lowest WS possible for such a long time.

Windgrins

 

[humber]

This is just wrong, it is the same calculation, so it will result in the same conclusion.

And the gearing DOES matter if you calculate the resistive force from the propeller from torque. ETA: and wheel size is part of the gearing, along with prop pitch, they ALL matter.

No, only the radius of the wheel matters.
For example you have 144.5rpm at 11.62m/, and 302N.m shaft torque.
If geared 1:1 that appears at the wheel shaft.
To achieve 114.5rpm ( 1.9 rev/sec) at 11.62m/s
r = 0.97m
F = T/r = 302/.97 = 311N.

Add gearing 23/65 = 0.35
Prop shaft AV = 114.5rpm
Prop torque = 302N-m

Wheel shaft AV = 114.5/.35 = 327.14rpm
Wheel torque = 302N-m/.35 = 105.7N-m

To achieve 327.14rpm ( 5.4 rev/sec) at 11.62m/s
r = 0.34m
F = T/r = 105.7N-m/.34 = 311N.
= 310.88N

It's a logical consequence of the fact the gears don't change power.

 

[windgrins]

I think you will find that is used as a rough guide, unless you have some means of calibrating the hitter. Even with the sensor in the hammer, angle of incidence, contact time and the damping effects of the hand, will influence the result. (And the authors used a wooden mallet)
Not a precision tool by any means. Once again. you have never been within 100 meters of any vibrational tests. Perhaps you can explain why turning on the motor produces forces of 80N, and the general noise level is apparently 3N. Perhaps they need to check the floor. Ever built a floating floor for sound isolation purposes windgrins? It is quite worrying as you watch 80m^3 of really hard to remove concrete being poured, and success or failure rests on your math.

I think I understand it pretty well since I've done it several times (not pouring concrete but performing vibration analysis of machinery). That's why they put a transducer in the hammer and one needs to hit the object squarely. I don't think you seem to understand the concept of impulse response.

I commented earlier that it was not clear from their paper how the author performed their measurement setup so we can't really tell if the measurement magnitudes were valid. Frequency response-yes, absolute magnitudes from the data presented-no.

I'm not use to lying about my expertise like you are on everything. As a professional engineer they frown on that in my discipline. You, on the other hand, don't seem to be bothered by it in the slightest as you seem to do it on all your claimed expertise as evidenced by your posts and subsequent questioning!

Again, what you think doesn't matter as you are clearly incapable of discerning expertise and think you have it in all disciplines.

PS. Did you calculate you had enough concrete, just right, or too little?

WindGrins

 

[Llyricist]

No, only the radius of the wheel matters.
For example you have 144.5rpm at 11.62m/, and 302N.m shaft torque.
If geared 1:1 that appears at the wheel shaft.
To achieve 114.5rpm ( 1.9 rev/sec) at 11.62m/s
r = 0.97m
F = T/r = 302/.97 = 311N.

Add gearing 23/65 = 0.35
Prop shaft AV = 114.5rpm
Prop torque = 302N-m

Wheel shaft AV = 114.5/.35 = 327.14rpm
Wheel torque = 302N-m/.35 = 105.7N-m

To achieve 327.14rpm ( 5.4 rev/sec) at 11.62m/s
r = 0.34m
F = T/r = 105.7N-m/.34 = 311N.
= 310.88N

It's a logical consequence of the fact the gears don't change power.

This is so dumb. Or dishonest. What do you think you are proving other than that wheel size is part of the gearing? You achieved the same results by changing both the wheel size and the gearing between your two example.

See what happens if you change one without changing the other, whether the ONE you change is gearing or wheel size, the results will be different.

 

[humber]

I think I understand it pretty well since I've done it several times. That's why they put a transducer in the hammer and one needs to hit the object squarely. I don't think you seem to understand the concept of impulse response.

I'm not use to lying about my expertise like you are on everything. As a professional engineer they frown on that in my discipline.

Which is? Can't be electronics, that's for sure.

You, on the other hand, don't seem to be bothered by it in the slightest as you seem to do it on all your claimed expertise as evidenced by your posts and subsequent questioning!

You show no expertise of someone with any actual knowledge.
12g RMS is a typical shaker table level used to test components for fighters; specifically the JSF (X35). What else is used, windgrins, and why?

Not a hammer in sight. Calibrated impact transducers are used for that purpose. Hitting something with a hammer, and counting the number of cycles will tell something of the resonance frequencies, but not a lot.


It did not seem to bother you that the motor apparently produces larger forces that someone actually running on the platform. The results suggest that the floor may not be stiff enough. The conclusions are not very sound. This one is much better, as the results of a fixed plate, and a belt were directly comparable.
http://jap.physiology.org/content/104/3/747.full

Watch how the runner's torso pivots over the foot that is planted ahead.
http://www.youtube.com/watch?v=T7A_QUlMbvY
Now a runner on a TM
http://www.youtube.com/watch?v=zbgSEG_Yx2k&feature=related

 

[humber]

This is so dumb. Or dishonest. What do you think you are proving other than that wheel size is part of the gearing? You achieved the same results by changing both the wheel size and the gearing between your two example.

The gearing is totally superfluous. If does nothing. Series gears never do.

See what happens if you change one without changing the other, whether the ONE you change is gearing or wheel size, the results will be different.

Total nonsense. Exactly the same.
If not, the prop's AV changes and so the power.
How dim do you have to be not to see that the torque is inversely related to the AV of the shaft, so will never change at the wheel?
By all means, prove me wrong.

 

[humber]

So, did they deduct the cost of pouring and removing the concrete from your salary, or did they just fire you?

The shimming process for the isolation dampers, which is my idea, is patented.

 

[Llyricist]

The gearing is totally superfluous. If does nothing. Series gears never do.

Wrong.

Total nonsense.

That period should be a colon.

Exactly the same.

What is exactly the same as what?

If not, the prop's AV changes and so the power.

Uh yeah, if you change either the gear ratio, or the wheel size, the props omega at a given ground speed will change, so what? That is MY point.

How dim do you have to be not to see that the torque is inversely related to the AV of the shaft,

The prop shaft? If so, wrong again, it is not inversely related to omega. If airspeed remains the same, it will increase with omega at constant airspeed.

If you mean the axle, at constant prop omega and airspeed, then the torque is inversely related rpm of the axle, and that is wholly dependent on gearing.

so will never change at the wheel?

wtf?

By all means, prove me wrong.

I would if that made enough sense to even be wrong, Say something that is even nearly coherent enough to be parse able, and I will prove it wrong. Unless you happen to get it right by accident of course.

 

[windgrins]

Which is? Can't be electronics, that's for sure.

How would you possibly know since you have little or no expertise in this? You didn't do so well on your trivial test as I recall!

You show no expertise of someone with any actual knowledge.
12g RMS is a typical shaker table level used to test components for fighters; specifically the JSF (X35). What else is used, windgrins, and why?

You may well have the competence to bolt some component to a shaker table and apply a transducer or strobe light. If this is what you are referring to, then the answer is: so one can see visually the magnitude of the excursions of the vibration of the UUT.

Past this, I'm not going to entertain questions on this severely off-topic set of questions as we understand its one of your favorite diversions when you have no valid point to make. Your questions are always so vague that you can make up any nonsense answer you want after the fact and say the person answering it "missed it" which is what you tend to do.

Not a hammer in sight. Calibrated impact transducers are used for that purpose. Hitting something with a hammer, and counting the number of cycles will tell something of the resonance frequencies, but not a lot.

You must not be testing anything much larger than a circuit board or assembly since you are not familiar with calibrated impact hammers as described by the data sheet I referenced. Not an issue by the way, just that they are used all the time with larger structures such as rotating machinery.

It did not seem to bother you that the motor apparently produces larger forces that someone actually running on the platform. The results suggest that the floor may not be stiff enough. The conclusions are not very sound.

This is the one statement I agree with. Since we don't have enough data about how the tests were performed, the magnitudes of the forces in PPGs quoted paper are suspect as I mentioned in my detailed answer to Giordano but you are correct that the general response spectrum can be obtained just not calibrated magnitudes if they don't have a way to measure input energy.

I don't want to criticize the author because they subsequently LPFed their data to remove high freq vibration noise which is what they were after.

This one is much better, as the results of a fixed plate, and a belt were directly comparable.
http://jap.physiology.org/content/104/3/747.full

It's about time to kill this one also. Physiological factors associated with these measurements do not have a lot to do with the subject at hand. The author of the paper has the following to say about this:

Second, if the treadmill belt speed does in fact change, then the acceleration patterns of the limbs under the two conditions would change, requiring a different control strategy to maintain constant kinematics.Similar to previous studies (29, 30), we did observe a slight drop in belt speed at heel contact (e.g., <2.5%) which can explain the differences in the dorsiflexor moments we observed in early stance. However, the differences in knee and hip moments observed later in the gait cycle would presumably not be affected by this issue.

Perhaps the most likely reason we observed differences between the two walking conditions is that optic flow subjects receive on the treadmill is in stark contrast to what they receive while walking overground. Studies have shown that vision plays a role in gait (32) such that different optic flow patterns may alter locomotor control strategies. When walking on the treadmill, subjects do not receive the same optic flow as they do when walking overground, which may alter their balance and stability or their perception of where they are on the treadmill or the speed at which they are ambulating. These factors are supported by previous studies, because Regnaux et al. (28) found that treadmill ambulation was not an automated task. Since the optic flow patterns are different between treadmill and overground walking, small perceptual changes at one stage of the gait cycle could lead to altered joint moments and consequently to a cascade of changes during the remainder of the gait cycle if the goal is to preserve their kinematic patterns, which is what we hypothesize. This hypothesis is further supported by Carollo and Matthews (6) and Ivanenko et al. (17, 18), who suggested that during human locomotion, the kinematics appear to be the desired control variable.

The most cogent remark from these papers has been:

"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."

Which, unfortunately, is exactly opposite of what you are claiming.

WindGrins

 

[windgrins]

The shimming process for the isolation dampers, which is my idea, is patented.

Is your name one of the names on the patent? I'm betting "No" That would be standard procedure for issuing patents.

WindGrins

 

[humber]

How would you possibly know since you have little or no expertise in this? You didn't do so well on your trivial test as I recall!

I have already shown you that it won't work, because the transistor is not correctly biased, and you failed to show that it is, or anything else for that matter.

You may well have the competence to bolt some component to a shaker table and apply a transducer or strobe light. If this is what you are referring to, then the answer is: so one can see visually the magnitude of the excursions of the vibration of the UUT.

As if.

Past this, I'm not going to entertain questions on this severely off-topic set of questions as we understand its one of your favorite diversions when you have no valid point to make.

Caught red-handed bluffing.

You must not be testing anything much larger than a circuit board or assembly since you are not familiar with calibrated impact hammers as described by the data sheet I referenced. Not an issue by the way, just that they are used all the time with larger structures such as rotating machinery.

Which you also have no experience of, but hope that I don't. Try again.

This is the one statement I agree with. Since we don't have enough data about how the tests were performed, the magnitudes of the forces in PPGs quoted paper are suspect as I mentioned in my detailed answer to Giordano but you are correct that the general response spectrum can be obtained just not calibrated magnitudes if they don't have a way to measure input energy.

You totally ignored the time over which the force is applied, and assumed a constant force. The average will of course be zero, or the treadmill plate will show a fixed displacement. That would appear as a constant strain in the force plate.

I don't want to criticize the author because they subsequently LPFed their data to remove high freq vibration noise which is what they were after.

To remove the 80N noise above 47Hz. Where does that come from?

It's about time to kill this one also. Physiological factors associated with these measurements do not have a lot to do with the subject at hand. The most cogent remark from these papers has been:

"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."

Which, unfortunately, is exactly opposite of what you are claiming.

And that is wrong, as so many other experiments show. That particular TM was developed in 1998, and the other paper is 2006. The difference has nothing to do with frames of reference. If the belt is moving, and the runner runs along the belt, so is in motion relative to the ground, then if the belt is good, there will be no difference. That is like walking on an airport walkway.
That does not apply when the runner is stays in place wrt the ground.

There are many more references that all state that in that case, there is a difference. Of course there is. The motor pulls the foot back, which never happens on the ground. Try it. Walk, and you will see that your foot swings back under gravity as you move forwards. You will raise your foot so it does not hit the ground as it swings back, but that won't work unless your torso moves forwards. On a TM, it doesn't, so the belt pulls it back. Runners adjust to that.

 

[CORed]

I have already shown you that it won't work, because the transistor is not correctly biased, and you failed to show that it is, or anything else for that matter.


As if.


Caught red-handed bluffing.


Which you also have no experience of, but hope that I don't. Try again.


You totally ignored the time over which the force is applied, and assumed a constant force. The average will of course be zero, or the treadmill plate will show a fixed displacement.


To remove the 80N noise above 47Hz. Where does that come from?



And that is wrong, as so many other experiments show. That particular TM was developed in 1998, and the other paper is 2006. The difference has nothing to do with frames of reference. If the belt is moving, and the runner runs along the belt, so is in motion relative to the ground, then if the belt is good, there will be no difference. That is like walking on an airport walkway.
That does not apply when the runner is stays in place wrt the ground.

There are many more references that all state that in that case,

Citation needed.

there is a difference. Of course there is. The motor pulls the foot back, which never happens on the ground. Try it. Walk, and you will see that your foot swings back under gravity as you move forwards. You will raise your foot so it does not hit the ground as it swings back, but that won't work unless your torso moves forwards. On a TM, it doesn't, so the belt pulls it back. Runners adjust to that.

Humber demonstrates for the 8,145th time that he has no clue about relative motion or frames of reference.

ETA: We have had a three page derail now, where the deniers try to pretend that the vibration, relative to the floor, of a particular treadmill used for experiments related to people running or walking on that treadmill, is in any way relevant to the treadmill tests of the small ddwfttw cart on different treadmills. As usual, much hilarity ensued from humber's and /0's tortured interpretation and bizarre misconceptions of this article.

 

[humber]

Is your name one of the names on the patent? I'm betting "No" That would be standard procedure for issuing patents.

WindGrins

Go fish. It's one disclosure regarding a patent for isolation dampers.

 

[CORed]

Is your name one of the names on the patent? I'm betting "No" That would be standard procedure for issuing patents.

WindGrins

They rarely put the janitor's name on patent, even if he does claim they stole the idea from him.

 

[humber]

Citation needed.

http://jap.physiology.org/content/early/2007/11/29/japplphysiol.01380.2006.full.pdf
http://www.ncbi.nlm.nih.gov/pubmed/7898346
http://www.springerlink.com/content/vk36p660367179n6/

http://www.mendeley.com/research/ki...s-overground-walking-in-healthy-older-adults/
http://www.clinbiomech.com/article/S0268-0033(08)00235-0/abstract
http://books.google.nl/books?id=dF4...wBTgK#v=onepage&q=gait on a treadmill&f=false

 

[ThinAirDesigns]

Have it your way. But I have your confirmation.

Another lie of course.

JB