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Messages - jduffy77
I was just browsing back through some of the older posts in this thread.
Take this post as a starting point. I took a bunch of numbers that Heinz provided (for the thrust from a certain propeller at a certain RPM, and for the power requirement for that same propeller, as well as his suggested transmission efficiency) and found a braking force that was less than the thrust. So the cart should advance on the treadmill, steady state, no need for any of the vibrational stuff from Heinz's fantasyland (which wouldn't work anyway, but that's another story).
You can see in this response that Heinz has a total tantrum/meltdown over it. Putting aside all the rabid frothing, there are really two vaguely substantial aspects to his critique of my post.
First: He had worked out (incorrectly, but let's pretend otherwise) the rotational energy in the prop, in Joules. Then he magically changed the units to Watts. Then he asserted (with no basis) that this number (or some magical fraction thereof) represented an additional amount of power required just to keep the prop turning! The actual power requirement had already appeared in one of the other variables, but he took this additional term from his hindquarters and added it on, just to try to force the numbers to work out the way he wants them to.
The change of units alone is enough to see that this tactic of his was complete nonsense. But in the meltdown post (linked above) he doubled down on it! Nevertheless, I think he realized eventually that this term was nonsensical, so he dropped that line of argument. (Of course he wouldn't acknowledge explicitly that he had made an error; he doesn't have enough integrity to do that.)
Second: He goes berserk over the fact that the difference between the thrust and the braking force is only 0.04 N (given the set of numbers used as input), and claims that I haven't considered all the possible losses. But of course, those "other losses" were the whole point of the less-than-perfect "transmission" coefficient that he suggested (and I accepted), so his critique misses the mark, as usual.
The really funny thing here is that he didn't even realize how close he had come to admitting that there's no problem with the cart advancing up the treadmill in steady state. Having dropped his first objection, his remaining objection (focusing on "other losses") doesn't imply anything against the cart in principle.
If there's a problem with the cart in principle (as he usually tries to argue, such as with his completely idiotic misuse of P = F v), then his objection involving "other losses", and involving the small magnitude of the force difference I found, would be irrelevant. Instead, he should have been able to find an error in my math. But of course he couldn't. He never has.
Of course that pales in comparison to the all time favorite from the hilarious train wreck that is our hyev in which he proved that the cart must work. If you haven't seen it give it a careful read it is worth it:
Quote from: Hyeveinz
The parameters are: windspeed is 7 M/s, cart velocity is 9 m/s DDW, both measured wrt the ground which is not moving. Cart weighs 270 Kg and has a 5 m diameter propeller.
Let the wheels generate 1000 Watts as the cart moves over the ground at 9 m/s and the wheel drag is 111.1 N.
Note: All calculations are in the frame of reference where the ground is stationary and has NO energy. The cart, moving at 9 m/s and with a mass of 270 Kg has 10,935 Joules of Kinetic Energy. The 1000 J/s developed at the wheels comes entirely from this KE of the cart being transformed into 1000 J/s of energy at the wheels and then this energy is used to do Work at the propeller to exert a thrust force on the air, accelerating it.
Let the overall efficiency of the cart be 87.5% so that there is 875 J/s of Work being done at the propeller on the air. (In reality such a high overall efficiency is impossible as the propeller taken by itself will not have this high an efficiency, but I am using a best case analysis here)
Thrust = mass x acceleration = л/4•D^2•[v+∆v/2] • ρ•∆v where л/4•D^2•[v+∆v/2] • ρ is the mass of the air moving through the propeller and ∆v is the acceleration of the air by the propeller. With the 5 meter prop, л/4•D^2• ρ works out to 24. V is the velocity of the relative headwind and that we know to be 2 m/s in this case. We don't yet know what the value of ∆v is and we don't yet know the value of thrust.
However we do know the power absorbed by the propeller is 875 Watts (875 J/s) and there is another equation that says *Engine power = Thrust•[v+∆v/2]. So we can equate these two relationships to solve for ∆v and then solve for thrust:
л/4•D^2•[v+∆v/2] • ρ•∆v = *Engine power / •[v+∆v/2]
Let ∆v be replaced by x
48x + 12 x^2 = 875 / (2 +x/2)
12x^3 + 96X^2 + 192 x =1750, x ~ 2.99
So ∆v = 2.99 and plugging that into either or both of the above equations gives a value for Thrust = 250 N.
Wheel Drag is 111 N and we can calculate Rolling Resistance from mgCrr using Crr of 0.02 and RR = 53 N. There is also air drag due to the 2 m/s headwind but I am not going to bother calculating it and assume a reasonably low value of 10 N for a Total drag force of 174 N.
At this point the less informed among the cart crowd will say I have just shown the cart works, because the thrust is 250 N and the drag is 174 N, right? No, forces alone are not the whole story as we need to consider energy and power. The thrust force is what would be there IF and only IF, there is sufficient energy in the system to develop and sustain that thrust. Now we will see if that is the case or not:
We know the prop will accelerate the air mass passing through it by ∆v and that is 2.99 m/s (effectively slowing the 7 m/s wind down by that amount)
We can calculate the air mass from the thrust equation: air mass = л/4•D^2•[v+∆v/2] • ρ and we already have all the values to fill in: = 24 (2 +1.5) = 84 Kg.
The initial KE of that mass is 2058 Joules and after being slowed it is 672 Joules so the air has lost 1386 Joules of KE.
In this best case analysis I will allow for ALL of that energy to be transferred to the cart! (In reality there will be air turbulence around the propeller, and such a 100% transfer is absolutely impossible).
Now we must consider the losses: In order for the cart to generate that 1000 Joules of energy at the wheels, it must move a distance of 9 meters over the ground against the drag force that we calculated to be 174 N. 174 N x 9 meters = 1,566 Joules of energy the cart requires in order to do the work at the propeller and overcome all drag at the wheels and due to air resistance.
Now it just a simple matter of seeing if the energy taken from the air is enough to replace the energy taken from the cart's kinetic energy to do the work at the propeller and overcome all losses. 1566 J/s needed vs 1386 J/s supplied leaves a shortfall 180 J/s.
It should be obvious at this point, to even the most devout member of the cart cult, the cart simply will not work as advertised!
10 years or so ago Uncool and Lyricist immediately corrected his energy analysis and our resident laughingstock went on a fairly long hiatus and came back with the vibration nonsense.
I don't understand how anyone who is aware of the NALSA certification can state that "it doesn't work". We all KNOW it works with the diligence of NALSA and the almost 3x windspeed record.
Now, if the stated certification was that the BB achieved 1.1x windspeed, some doubts about gusts, lulls, measurement accuracy etc. may be credible. At 2.8x windspeed, any skepticism is just for trolling purposes.
I personally witnessed the BB rolling along at roughly 1.5x - 2x windspeed in a gentle wind that seemed to average around 10 mph.
I don't know how long you have been laughing at our Hyevpropangloss but one of the more hilarious things about him was how much reverence he initially had for NALSA. He was completely certain that they would shoot down the whole DDWFTTW concept as soon as they had a close look at it. We all know what has has happened since. Poor Haryevpan. I almost feel sorry for the nitwit.
Would the deniers ever accept...Let me stop you right there. NO - the deniers will not accept *anything* if it implies the vehicle went DDWFTTW - not even if they accepted it before. Not even if they themselves used it to prove it can't go DDWFTTW.
Definitely without a doubt true. Although I think we are down to a singular denier now.
Hyeveinz, did you see those Aeolus folks exceeded wind speed?
Honestly, I think Heinz is far more consistent than humber or Harold. This is the part where I expected there to be a problem, given past posts.
Now we just need to know if he's up for discussing it.
Heinz is Harold.
At which point we are 10 years back in time arguing the exact same shit
You have a point there. Without any scientific evidence it really is a pointless argument, but somebody has to counter crackpots.
Could you share with us what your definition of "crackpot" is?
One of the more interesting arguments about the cart on the treadmill centers on the idea of relative motion. It seems that the believers in ddwfttw think that applying a force to move a belt under a wheel must be the same as applying a force to move a wheel over the belt. While this kind of reciprocity is considered to be some sort of fundamental truth in mechanics, it may shock some people to learn it is not universally true!
It is true that if a force F is applied to one end of a sliding block, and then the same force F is applied to the other end of the same block, the resulting motions of the block will be symmetrical; the block behaves the same in both directions.
However, if the physical system is more complex, involving springiness and rotations, as the cart on the belt does, there is no guarantee that the motion will be symmetrical in such a non-linear system. In fact, there is currently quite a lot of research being done in this area, with several materials already being made that exhibit this non-symmetrical, non-linearity to motion.
That is just one more nail in the coffin for the claim that the treadmill cart, being powered by the belt, says something about a cart on a road powered by the wind.
Before anyone claims that this is denying Galileo, no, it is not! The GT of the cart on the belt is just changing the frame of reference while staying with the same situation; it is always a cart on a treadmill, powered by the belt.
What the carters are claiming is a magical transform; that a cart on a belt, powered by the belt, is the same as a cart in the wind, powered by the wind and that is total nonsense!
Hyeveinz, you are a loon.
I might send over a child with a bunch of helium balloons to show what a farce this is.
No you won't.
Any loss of traction will result in less acceleration of the device,
And you know this how?
I think of all the H's nonsense and stupidity over the years I find hyev's idea that a cart which loses traction could perform better than a cart which does not the most fascinating. It would be truly incredible how many over unity schemes the H's have proposed to explain the cart's function regardless of how they misunderstood its mechanisms. The irony of the fact that in their ignorance they think ddwfttw itself is over unity is what makes their flailing so hilarious.
Three simple questions, Hopalong:
1: An ant is clinging to the treadmill surface. Does he notice a wind?
2: If he holds up a little toy windmill, will it rotate?
3: Is the energy causing that rotation coming from the still air in the room?
Our resident laughingstock will not answer these questions. He has ignored them for 10 years. As I have said many times, thinking about how large a TM would have to be before you could not tell you were on one terrifies our nitwit Hyev more than any other cog dis inducing issue. As you say we sure should thank him for all the laughs over the years; it is Thanksgiving in the US today.
..................I had assumed that you would realize that this is not a matter of faith for most of us. It's not as if Spork and JB made claims that DDWFTTW is possible and the rest of us said to ourselves, "Well, Spork seems sure about it so I suppose I will accept it".
I continue to be befuddled by the utter certainty on both sides. I mean, think of all the examples of widely accepted science that was eventually proven wrong. Oh ye of too much faith.
So in my case and I expect most others, I KNOW it works. Not like a religion where you must have faith. I know it works because early on I had doubts and realized that calculations were possible to resolve the issue. I have shared those pretty simple calculations here a number of times. Then I bought one of the cart models and operated it. Then I saw the Blackbird videos and saw it clearly and undeniably spank the wind going downwind, over the ground with at least 2x windspeed.
So, it's not "too much faith". It's a simple fact.
Unlike our H's unfortunately RP is just a troll, yes he is stupid, but he does not really believe the H's could be right. Otherwise we could have had the fun of announcing that rocks were denser than pillows. Wait a minute non-troll RP says, that widely accepted scientific fact might not actually be true after all as he picks up a good sized rock and smashes himself in the face with it. Too bad...
I'm a little curious about the idea that the cart on the treadmill "loosing traction" somehow allows it to appear to be working when it really isn't, or however that argument goes. I don't quite follow the rationale behind that.
In most circumstances loosing traction would cause something to falter or fail. How does loosing traction, theoretically or whatever, allow the cart to stay on the treadmill, if i understand the argument behind that correctly, which I'm pretty sure I don't, or I wouldn't be asking.
If this has already been explained, a link back would suffice and would be much appreciated.
I'm guessing maybe the idea is the cart is being held "motionless" to start with so being off the treadmill allows it to stay in one place rather than being carried down and off the end of the treadmill? Just guessing.
Unless you are a Hidiot it is in fact obvious that any loss of traction would result in a loss of efficiency making any ddwfttw cart video more convincing not less.
Unrelated question: Why do I see people using "loose" when they mean to use "lose"? To me it makes them seem ignorant and foolish but I see it so much lately I am wondering if it is some sort of redefinition the millennials have come up with? Has any one else noticed it?
It's not like a quack cancer cure, where people are dying because they use the cure instead of getting treatment that might actually work.And it's not being promoted for *anything*. No one is losing their life savings, no one is getting famous. There are three guys that are looking like complete idiots, but that appears to be voluntary.
Three? Heinz is Harold. There was Humber. If you are talking about RP I would say of course he is an idiot but he is an idiotic troll rather than a true zealot for the cause.
It has been clear all along that Heinz is quite incompetent. But what I'm only belatedly realizing (maybe the rest of you figured it out long ago) is how unhinged he is. It's very hard to read his last response to cold one as anything but psychotic.
What has always fascinated me is the epic scope of the Heinz's failure. Stuff gets exaggerated all the time on the internet but in this case I believe it is a fact to say that they are among the biggest fails in the history of civilization. I have over 18 million words the H's have written (the King James bible has 750k) in my own database and over 90000 posts. I used to post a bunch of statistics about the time he and the other Hidiot have spent on this endeavor with not a single convert or any other indication of any sort of success or progress in convincing someone, anyone of their correctness. Instead there have been instance after instance of there nonsensical arguments prompting someone initially skeptical to educate themselves and gain understanding of the ddwfttw cart's function. Donald Simanek would be a prime example of this opposite effect. It is profoundly sad but definitely, at least to me, fascinating at the same time.
Extra Credit: (Only for true experts in Hyeveinz's imaginary world)
Could forcing the periodic loss of traction during an airplane's takeoff be utilized in order to takeoff from shorter runways, save fuel or some other benefit?
Heinz poses the question: If you have a treadmill running at v0 = 4.0 m/s, and a cart initially keeping up with the treadmill (presumably because it has been held in place to get the wheels and prop up to speed, then released), with a braking force of FB = 0.25 N, and with a transmission efficiency (from the wheels to the propeller) of τ = 0.90, what is the thrust from the propeller?
The answer depends on a bunch of other factors, of course. But having given us a figure for FB, that helps narrow things down.
Let I be the moment of inertia of all the rotating parts of the cart, considered collectively, as measured at the wheels. Let r be the radius of the wheels. Let m be the mass of the cart. We don't need these things individually, but we are interested in the ratio χ = I/(m r2). This ratio can be just about any positive number, although I think a case with χ > 1 would be rather weird. It will be low if the cart's mass is concentrated in the body, and somewhat higher if the mass is concentrated in the rims of the wheels and/or in the propeller.
Yes, for sure that would be weird since I is usually taken to be 1/2 mr^2, so your silly "ratio" of I/mr^2 is just 1/2.
Other things we need: Let ρ denote the density of the air, let A denote the area of the disc swept by the propeller, and let ζ denote the propeller's "figure of merit" for the case of static thrust.
The to get the thrust force FT, we need to solve
FT3/2 / (ζ v0 (2 ρ A)1/2) + χ FT = (χ + τ) FB.
(Where does that come from? I'll happily go through it if someone asks, although Heinz probably won't be able to follow the math.)
Oh, I have a good idea of where that came from! Wherever it was, that is most definitely NOT a proper equation for propeller thrust.
For one thing, the rotational kinetic energy of the propeller has nothing to do with the calculation for propeller thrust and propulsive power absorbed by the propeller. The rotational KE of the propeller is an entirely separate issue.
For the propeller you have used, with a diameter of 0.4 m, we can consider the APC 16-8, which has a mass of approximately 50 grams.
The moment of Inertia, I = 1/2 (.05) (.2)^2 = .001
At a belt speed of 4 m/s and wheel circumference of 0.25 m, gear ratio of 1:1 (which is what the treadmill carts use) the propeller will be spinning at 16 rev/sec (960 rpm) and ω is approximately 100 rad/s
Rotational KE of the propeller alone is 1/2 I ω^2 = 5 Watts
Fortunately for you, that 5 Watts of rotational KE does not need to be fed into the propeller continuously. Once the propeller is spun up, only the energy lost due to friction needs to be replaced. We assumed 90% efficiency, so a constant 0.5 Watts needs to be fed into the propeller just to keep it spinning, and that is entirely separate from the propulsive power needed to provide thrust.
I provided a good workable equation for thrust earlier:
The static thrust for a propeller Ts = 1.283 x 10-12 x RPM2 x D4 x p x K
Where Ts is static thrust in Kg
D is diameter inches
P is air density in kg/m^3
K is a static thrust coefficient (0.73)
For the APC 16-8 spinning at 960 rpm, that works out to 69.3 grams, .68N, or 0.153 lbf
The propulsive power needed in horsepower:
= Pitch x RPM x Thrust / 12 x 33000
Where pitch is in inches and thrust is in lbf
For this propeller that works out to 2.967 X 10-3 HP or 2.2 Watts
With 90% transmission efficiency that is 2.5 Watts at the wheels of continuous power.
Unlike you, I provide a source for my equations. You can use the calculator or right click to get the source code:
So, the total continuous power requirement at the wheels is 3 Watts. (2.5 W propulsive power + 0.5 W continuous losses to provide the rotational KE to the propeller)
Braking force at the wheels is 3 W / 4 m/s = 0.75 N
Total Thrust = 0.68 N
The cart cannot hold position and goes backwards on the belt, as expected.
There are plenty of other losses in the cart I can add in, such as wheel deformation loss, but this is enough to show the cart cannot hold position let alone advance on the belt, steady state.
In fact, any sane person would know this must be true because if the thrust was more than the brake force, you could push the cart on the ground at 4 m/s and it would roll forever as a perpetual motion machine!
The ONLY possible way the cart advances up the belt is by the periodic loss of traction, which lowers the braking force but hardly affects thrust force because there is energy stored in the propeller to maintain thrust.
The claim of ddw is a CRACKPOT claim and you people in the cargo cult are just insane for believing it besides being too GUTLESS to even look at a high frame rate video which will CONFIRM the cart is oscillating up the belt with periodic loss of traction that probably occurs at the propeller blade pass frequency. Indeed, it is impossible for such a lightweight cart to maintain constant traction on the belt once released since the rotational KE of the propeller is more than enough to cause the wheels to lose contact with the belt.
Multiple choice section:
A. Frame switching
B. Inappropriate / misapplied formula
C. Double counting error
D. Arithmetic error
E. All of the above
Still haven't heard how you got on convincing the AAPT that they are wrong about DDWFTTW, Heinz?
How come not one physics teacher has questioned it?
Now who do we believe might be right- Heinz, or several thousand fully qualified physics teachers?
And you may have missed this tobermory we can add Mark Levi another genius,, PHD from the Courant Institute and Penn State math professor who wrote another effectively peer reviewed article:
DDWFTTW post by Mark Levi, professor of mathematics at the Pennsylvania State University, writing for the Society for Industrial and Applied Mathematics:
I had a nice list of the folks who our favorite laughingstock hpaninzyev has declared incompetent but I do not have my old database accessible at the moment a few more from memory:
One of the foremost aerodynamicists in the world MIT professor and fellow of the American Institute of Aeronautics and Astronautics Mark Drela.
The folks at NALSA.
The Guinness World record folks.
Richard Jenkins famous land sailor and pilot of the record breaking Greenbird.
All the mentors and editors over at PhysicsForums.
The audiences members at AIAA, Stanford, SJSU and many others.
Donald Simanek, another Penn State PHD and well known investigator of physics hoaxes.
A thousand or so physics blogs, Guaanna, Chu-Carroll, Winkler.
Numerous well known publications, the editor of Wired, the editor of MAKE
The Aeolus teams particularly hilarious now that they have broken 100% of WS which of course was something else our Hnut declared completely impossible.
I should power up my old database,
Actually for HH scholars his current absence was entirely predictable. As soon as A.T. posted that link the other day I could have told you we would be entering a Hyev hiatus. The length of it will depend on how long Mark Levi takes to decide Heinzyevpangloss is a raging loon. Something like this article for the Society for Industrial and Applied Mathematics will particularly enrage our resident crackpot since he knows it is a thoroughly peer reviewed scenario just as the AAPT was.
I see the slipping argument as borderline insanity.It's ludicrous. But, as Spork says, Heinz starts with the premise "the cart cannot work" and takes it from there. I expected this sort of "rebuttal" from Harold, Humber and Heinz before the documented DDWFTTW record, but after? Hahahahaa. A troll gold star awarded to Heinz aka Humber.
Heinz is Harold, Humber is actually a different nutter. Amazingly there have really only ever been the two freak deniers other then folks who have been convinced they were wrong after ddwfttw was explained to them.
Possible misinterpretation alert: I latched onto the word "same" and took it too literally (beep boop). The power extracted from the wind (in the rest frame of the surface) doesn't have to be equal in value to the power extracted from the treadmill (in the rest frame of the air). But the general principle is the same, and there's nothing "unjustified" about it.Quote from: HeinzYour assumption that the same power can be had from the wind as the cart can draw from the belt is another Cargo Cult unjustified assumption.Who ever assumed that?
Try to understand what exactly you're criticizing before you criticize it.
But it can't be equal. The wind obeys Betz, the treadmill motor never heard of Betz.
Hey Hyeveinz, do you think the Aeolus folks will make 125% of WS?
Hyeveinz, how about those Aeolus folk? Over 100% WS now! Do you think they will make 125%?
You have been taken in by a childish notion and now you cannot admit it.
Hey Hyeveinz how is your quest to get the AAPT to apologize going? And how about those Aeolus scammers, over 100% of WS now, are you on that?
Must be some miscommunication regarding this. There is no reason that longer treadmill belt length would cause airspeed variability above the belt. Very near the belt the boundary layer of air may move more in the direction of belt movement with a longer belt but I wouldn't think this is what Spork meant by variability.
How large would a treadmill have to be before you could not tell you were on one?
It is *exactly* as accurate to say the air is moving as it is to say the ship is moving. It's not a matter of what it "seems" like.movement
an act of changing physical location or position
By definition when something moves, it changes location, or position. An object moving through still air is obviously moving. If the air is still, not moving in relation to the ground, and you ride a bike (or an aircraft carrier) through the still air, this does not somehow allow us to claim all the air is now moving. Because it's not.
Of course the moving object experiences the air (and the entire world) as moving, But it's absurd to claim the air (or the ground) is moving.
You could do a similar thing, and move yourself at the exact speed of an actual wind, and then claim the wind is not blowing. It's just as absurd. Of course from the POV of a moving object everything else is moving, but we don't say the world moves when we drive to the store.
It doesn't matter for the cart experiment, because the cart experiences a wind on the treadmill, or aircraft carrier, since the relative motion of course causes a wind. But it does no good to claim the air is moving over the treadmill, since it is not.
I realize now that this guy is at least as loony as our two Hs.