Merged DDWFTTW in a “Real” Wind

[windgrins]

WindGrins checking in with RP

Really? I must have missed that. Can you post a link or give me an idea on about what page I might find that explanation?

@Windgrins: Excellent post before your last one. You should read some of Humber's exchanges with uncool at TR. I'll post a link to a couple. Be curious to see what you make of them.

RP,

Happy to take a look if you send me the references. To be honest I've read about 3/4 of everything I could find on this.

I'm actually feeling a bit blue for Humber. This seems to be consuming him. It's a tough position when everyone is after you. I'm sure JB and Spork felt the same but they have the situation of moving from being thought of as silly to the enthralled position of completely vindicated and admired for the achievement. That's a far easier path. It's like a poor kid who grows up to become rich. That direction is far easier to tread than the converse.

In spite of his actual modesty, I feel like I owe a debt to Spork and JB for teaching me a lot I had never thought of in detail. There are lots of folks vying for their time and Spork has afforded me much more than I warrant.

I'd like to think that if I have an aero question in the future, I could send him an email and get an answer. One doesn't want to abuse that privilege.

Thanks for the nice comment regarding my post!

 

[recursive prophet]

Actually he promised it many months (years?) before that.

Yes, but remember we've seen pictures of the cart El Jefe and most of the carteers assured us would never be built. Some great sarcasm by spork as I recall, amidst a choir of hecklers. And yet, the cow which is not a hat we'd seen so often, was right there; proof this was Humber's cart. The one that would never exist. After so much time. Now a repeat? I also smell the fear.

 

[windgrins]

An ultimate Irony-albeit a low probability

RP,

I think you'll have a good laugh about this: The reason I suspect Humber won't be able to produce the advertised cart is that from the way its described, it would seem to violate COE-the ultimate irony.

If I've learned anything from this blog, its that there is always room for someone to do something very clever that you didn't really think was possible initially.

If Humber can produce what it sounds like he thinks he can. I'm ready to celebrate with him!

The one mysterious question I've seen in this entire blog was Ynot's mystery marble on the circular treadmill. I don't think it violates any laws but that was potentially interesting behavior of a dynamic object that I did not expect. There may be issues with the fact that he was not running the table at a constant speed but the behavior of that marble was sort of lost due to the questions of impropriety. It's just possible that there might be a principle hidden in there like dynamic soaring. Not something for nothing, but milking different paths for energy. Everything else that I've seen on this blog was just good solid (although unexpected) physics and engineering, very clever theory, and hard work. A pretty good formula for success. Just so I'm clear-I'm not saying the marble's behavior was inexplicable, I just didn't understand it. I would like to know more....

Too bad!

Regards,

WindGrins

 

[recursive prophet]

In spite of his actual modesty, I feel like I owe a debt to Spork and JB for teaching me a lot I had never thought of in detail. There are lots of folks vying for their time and Spork has afforded me much more than I warrant.

I'd like to think that if I have an aero question in the future, I could send him an email and get an answer. One doesn't want to abuse that privilege.

Believe it or not I probably feel far more indebted to them, and I have no doubt spork would take the time to answer your question. Despite the disparaging comments, overall I hold them in high regard. I'm more than willing to extend a lot of deference to characters less than half as interesting as sporkle. In a world of grey, he adds colour.

Of course we all have our weak areas, and often introspection is among them for those who's thoughts are immersed in technology. You have recently witnessed a small sample of how this can play out online. For a novice, it becomes hard to separate the facts from emotions at some point. I'm guilty of having tweaked Butch and Sundance on occasion, but unlike them for me it's not personal. All pure glassperlenspiel at this stage, at least until we see Humbers video.

Don't give up on converting Humber. You might yet make it into the DDWFTTW hall of fame! As the Chief has often said, I think you're almost there.

As to ynot's marble, I only vaguely recall that episode but thought it brought out some interesting questions. I asked ynot about the arm holding the cart on the circular mill acting as a tether way back, and he said it wouldn't matter ims. I would still like to see Blackbird's 16g chick self start via the apparent tailwind on a much longer belt, or travel up one for say 100 feet. Who knows? Somebody may do it down the road.

 

[ynot]

RP,

I think you'll have a good laugh about this: The reason I suspect Humber won't be able to produce the advertised cart is that from the way its described, it would seem to violate COE-the ultimate irony.

If I've learned anything from this blog, its that there is always room for someone to do something very clever that you didn't really think was possible initially.

If Humber can produce what it sounds like he thinks he can. I'm ready to celebrate with him!

The one mysterious question I've seen in this entire blog was Ynot's mystery marble on the circular treadmill. I don't think it violates any laws but that was potentially interesting behavior of a dynamic object that I did not expect. There may be issues with the fact that he was not running the table at a constant speed but the behavior of that marble was sort of lost due to the questions of impropriety. It's just possible that there might be a principle hidden in there like dynamic soaring. Not something for nothing, but milking different paths for energy. Everything else that I've seen on this blog was just good solid (although unexpected) physics and engineering, very clever theory, and hard work. A pretty good formula for success. Just so I'm clear-I'm not saying the marble's behavior was inexplicable, I just didn't understand it. I would like to know more....

Too bad!

Regards,

WindGrins

The “magic marble” video I posted wasn’t on a powered turntable but the relatively small amount it was slowing had very little effect on the action of the marble (not discernable). When I repeated the tests with a constant speed turntable the result was the virtually same. The marble had quite a bumpy surface as you can hear on the video. When I used a smooth and heavier large ball bearing the effect was even more impressive and the marble could “hover“ for quite some time. It could never keep exactly the same position of course and always gradually lost ground to the turntable. The only way it could possibly gain against the turntable was to push it toward the centre of the turntable where the surface was moving more slowly. I didn’t post any videos of this because I went overseas and when I returned I spent all my time building the cart. Tests with the cart proved conclusively (to me at least) that that it wasn’t storing energy in any way as I previously thought it might be. In other words what the marble does has nothing to do with what the cart does. The Coriolis effects where quite entertaining and the video seems to have had more views than the cart ones.

 

[spork]

I have tried to show patience and illustrate common misunderstandings with care as I greatly appreciate when others give me the same courtesy.

I like to think I have nearly infinite patience for people that have genuine questions and don't call me a liar, cheat, or idiot. There's no question I have nearly zero patience for the folks that do attack me in that way - which I've found to be surprisingly common.

RCP is famous for claiming that I insult people for simply disagreeing with me. Total nonsense. There are plenty of people that disagree with me on plenty of things, including this silly cart - and I never insult them. If however, they call me an idiot, liar, cheat, etc. as they disagree with me on the silly cart, yes, I make a point of returning the insult.

it is clear that Humber's training in modern or classical physics is lacking but that should not be held against him as that is the predominant way of the world.

And I don't hold that against him. There are plenty of people that don't understand physics. But they don't act like humber. Interestingly, the forum rules permit him to act as he does, but they don't permit me to say what way that is.

I'd like to think that if I have an aero question in the future, I could send him an email and get an answer. One doesn't want to abuse that privilege.

I would certainly try and answer any question I could. No need to worry about abusing any privilege, but people that know me, know it doesn't hurt to remind me of things. Emails tend to scroll by like movie credits in my browser. I very often fail to keep up.

The one mysterious question I've seen in this entire blog was Ynot's mystery marble on the circular treadmill. I don't think it violates any laws but that was potentially interesting behavior of a dynamic object that I did not expect.

I'd have to look at it again, but my recollection is that it imitated typical orbital dynamics. If you look at the behavior of a spacecraft in a local gravity-aligned frame, it can seem pretty bizarre (and makes it difficult for astronauts to control them for docking, etc.). When you hit forward thrusters you go "up" (away from Earth). Reverse thrusters make you go down (toward earth). Down thrusters will send you forward, and up thrusters will send you back.

So if you're all lined up for docking, and hit forward thrusters to do the deed, you end up missing the target. In a true inertial frame it all makes sense. But in the local frame, the craft appears to go in circles as a result of a single thrust.

 

[humber]

I see no reason to defend the other two statements as they are correct as stated by Spork-not exactly as they are stated above.

In one-dimension this is true; but in 2 or more dimensions it's not always true. Consider the case of two cars passing on the highway - one northbound and the other southbound. They pass with several car widths between them. Let's say each is going 60 mph. At the moment they're adjacent to one another, their relative speed is 120 mph. But their closing speed is 0 mph at that moment.
During their approach or departure, their relative speed and closing speed become more closely aligned the further away from this point at which they're adjacent.

Incorrect, and the same folksy mistake. At no time is there a relative speed, anything other than 120mph. When at 100m that is true, at 1m and 1mm.

The distance between the vehicles falls as they approach, but the rate of change is constant. That is, measuring that change in distance over time, gives the relative speed and that is constant. There can be no "closing speed" and "relative speeds", that become more closely aligned as the cars approach, And no, there is no "sweet spot, when d =0 .

The others concerns balloons that accelerate with zero time, which implies infinite force, and that NB balloons have no gravitational potential energy.

The point about the two cars, it that Spork mistakes differential speed ( two things moving in opposite directions) and two things moving in the same direction, and that mistake appears in the TM.

From an observer in space or even altitude, the surface of the planet and a car may be moving in the same direction, but the vehicle may be moving forwards faster. (That is more than an illusion, but real, and would be necessary say, if the driver wanted to circumnavigate the Equator, in the direction of rotation, but do so in less that 24 hours. )
At no time does the Earth move backwards relative to the car, at any speed including zero. If the car is mentally stopped, or in your parlance, viewed from the frame of the high attitude observer, then the ground still moves forwards but under the car. If the ground is mentally stopped, the car moves forwards.

We have just witnessed the Carteers being corrected on their notions of relative KE, but that is only part of the error of thinking that A hitting B, is the same as B hitting A, based solely on the idea that the relative velocities are the same. From that error, comes scoffing about "most people" thinking that a car hitting a truck, is different from the same truck hitting the car at the same speeds.
"From the frame of our stationary truck", the car is inevitably approaching the at speed. Do you think that at the point of impact, and prior to that, the driver may have applied the brakes and for good reason?

"From the frame of the stationary car" with the truck approaching, would you have your foot on the brake or not?

 

[humber]

Humber,
In spite of his actual modesty, I feel like I owe a debt to Spork and JB for teaching me a lot I had never thought of in detail. There are lots of folks vying for their time and Spork has afforded me much more than I warrant.

I don't believe you are genuine, Windgrins. Too much time and efforts proselyting, and being an apologist, while tip-toeing.

 

[humber]

RP,

I think you'll have a good laugh about this: The reason I suspect Humber won't be able to produce the advertised cart is that from the way its described, it would seem to violate COE-the ultimate irony.

If I've learned anything from this blog, its that there is always room for someone to do something very clever that you didn't really think was possible initially.

If Humber can produce what it sounds like he thinks he can. I'm ready to celebrate with him!

The one mysterious question I've seen in this entire blog was Ynot's mystery marble on the circular treadmill. I don't think it violates any laws but that was potentially interesting behavior of a dynamic object that I did not expect. There may be issues with the fact that he was not running the table at a constant speed but the behavior of that marble was sort of lost due to the questions of impropriety. It's just possible that there might be a principle hidden in there like dynamic soaring. Not something for nothing, but milking different paths for energy. Everything else that I've seen on this blog was just good solid (although unexpected) physics and engineering, very clever theory, and hard work. A pretty good formula for success. Just so I'm clear-I'm not saying the marble's behavior was inexplicable, I just didn't understand it. I would like to know more....

Too bad!

Regards,

WindGrins

The ball spins on the surface. There are two forces at work.
Friction rolling the ball, or driving it as a linear mass. It is difficult for that to remain stable, and the sphere takes up rotation in another plane, and that appears as circular motion.
My TM is no trick, and you want to know about threads etc No need to bother with unecessary tricks like that.

Spork's cart can be tied to the chassis by a thread from the front, and nothing will change if the cart is at "windspeed". That is why so many tests were declined. The cart can pull nothing, so it is poked with a fork instead, which gives away it's dynamic behaviour, but hey, what do Carteers ever notice?
The prop functions as that thread to the chassis, by providing a small static force against friction from the belt. To equate that force with one driving a cart traveling at the same speed in the wind, it to say that the cart is driven by a force equal to the rolling resistance. (but actually, even less)

 

[3point14]

In one-dimension this is true; but in 2 or more dimensions it's not always true. Consider the case of two cars passing on the highway - one northbound and the other southbound. They pass with several car widths between them. Let's say each is going 60 mph. At the moment they're adjacent to one another, their relative speed is 120 mph. But their closing speed is 0 mph at that moment.

Incorrect, and the same folksy mistake. At no time is there a relative speed, anything other than 120mph. When at 100m that is true, at 1m and 1mm.

You appear to have accidentally agreed with him.

 

[humber]

I like to think I have nearly infinite patience for people that have genuine questions and don't call me a liar, cheat, or idiot.

There's no question I have nearly zero patience for the folks that do attack me in that way - which I've found to be surprisingly common.

You don't think that the two may be connected?
How many reading this thread, find that they are commonly attacked?

I'd have to look at it again, but my recollection is that it imitated typical orbital dynamics. If you look at the behavior of a spacecraft in a local gravity-aligned frame, it can seem pretty bizarre (and makes it difficult for astronauts to control them for docking, etc.). When you hit forward thrusters you go "up" (away from Earth).
Reverse thrusters make you go down (toward earth). Down thrusters will send you forward, and up thrusters will send you back.
So if you're all lined up for docking, and hit forward thrusters to do the deed, you end up missing the target. In a true inertial frame it all makes sense. But in the local frame, the craft appears to go in circles as a result of a single thrust.

Blah....blah...urban.
The craft moves in a direction opposite to the thrust.
There are some precession effects etc. For example, two objects within the ISS, will orbit each other, but the periodicity and force is very low. Know a lot about the ISS, Spork? Guess what ESA-ESTEC have a lot to do with?.

 

[humber]

You appear to have accidentally agreed with him.

"They pass with several car widths between them. Let's say each is going 60 mph. At the moment they're adjacent to one another, their relative speed is 120 mph. But their closing speed is 0 mph at that moment."

How does one calculate the relative speed of the vehicles? Measure the change in distance between them over time v = dv/dt. That is a constant 120mph, regardless of distance apart.
A closing speed of zero. I see, at one point, just prior to them being 0m apart, the speed is 120mph, then instantly becomes zero, to become instantly 120mph again. "Closing speed" comes from the movies.
Spork is a manager in the sports broadcasting business.

 

[3point14]

"They pass with several car widths between them. Let's say each is going 60 mph. At the moment they're adjacent to one another, their relative speed is 120 mph. But their closing speed is 0 mph at that moment."

How does one calculate the relative speed of the vehicles? Measure the change in distance between them over time v = dv/dt. That is a constant 120mph, regardless of distance apart.
A closing speed of zero. I see, at one point, just prior to them being 0m apart, the speed is 120mph, then instantly becomes zero, to become instantly 120mph again. "Closing speed" comes from the movies.
Spork is a manager in the sports broadcasting business.

Does that mean 'Yes, I accidentally agreed with him"?

Look, if it's an error, retract it, but it's there in black and white to anyone who cares to read.

 

[humber]

Does that mean 'Yes, I accidentally agreed with him"?

Look, if it's an error, retract it, but it's there in black and white to anyone who cares to read.

Patently he is wrong. Have you understood that bit, not just what I say, about what he says, which seems to be your central focus on every matter?
The relative velocity does not change, while "closing velocity" is a folksy and incorrect notion. It does not exist.

Carteers are not interested in hearing they may be wrong, nor learning. The lesson from Rhett, says you have at least one fundamental idea wrong, but instead of like Jamie, accepting that, you deny it, so that you can keep alive the cart.
On the other hand, I know that the TM has nothing to do with a cart in the wind, and the recently acquired NALSA data says the cart is not a ddwfftw vehicle.
This is because the constructors are office managers, with aspirations of being seen as scientists.

 

[sol invictus]

"They pass with several car widths between them. Let's say each is going 60 mph. At the moment they're adjacent to one another, their relative speed is 120 mph. But their closing speed is 0 mph at that moment."

How does one calculate the relative speed of the vehicles? Measure the change in distance between them over time v = dv/dt. That is a constant 120mph, regardless of distance apart.
A closing speed of zero. I see, at one point, just prior to them being 0m apart, the speed is 120mph, then instantly becomes zero, to become instantly 120mph again. "Closing speed" comes from the movies.
Spork is a manager in the sports broadcasting business.

There is

[latex]${\vec v}_{\rm rel} = {d \over dt} \left( \vec x_1 - \vec x_2 \right)$[/latex] and
[latex]s_{\rm clos} = {d \over dt} \left| \vec x_1 - \vec x_2 \right|[/latex].

But [latex]$|{\vec v}_{\rm rel}| \neq s_{\rm clos}$[/latex]. In the situation described, [latex]$|{\vec v}_{\rm rel}| = 2v \equiv 120{\rm mph}$[/latex], while [latex]$s_{\rm clos}=2v \left[2vt/\sqrt{(2vt)^2+b^2} \right]$[/latex] (b is the distance between the cars at t=0 when they pass each other).

 

[3point14]

Patently he is wrong. The relative velocity does not change, while "closing velocity" is a folksy and incorrect notion. It does not exist.

Oh, you're just making it up as you go along now, Brian.

 

[humber]

As to ynot's marble, I only vaguely recall that episode but thought it brought out some interesting questions. I asked ynot about the arm holding the cart on the circular mill acting as a tether way back, and he said it wouldn't matter ims. I would still like to see Blackbird's 16g chick self start via the apparent tailwind on a much longer belt, or travel up one for say 100 feet. Who knows? Somebody may do it down the road.

The reaction arm takes up the torque from the wheel. If the arm where the axle of the wheel, and free to turn with the wheel, then the effect would all but disappear but for residual effects.
I will go backwards with the table.

 

[windgrins]

Long Treadmill question

Believe it or not I probably feel far more indebted to them, and I have no doubt spork would take the time to answer your question. Despite the disparaging comments, overall I hold them in high regard. I'm more than willing to extend a lot of deference to characters less than half as interesting as sporkle. In a world of grey, he adds colour.

Of course we all have our weak areas, and often introspection is among them for those who's thoughts are immersed in technology. You have recently witnessed a small sample of how this can play out online. For a novice, it becomes hard to separate the facts from emotions at some point. I'm guilty of having tweaked Butch and Sundance on occasion, but unlike them for me it's not personal. All pure glassperlenspiel at this stage, at least until we see Humbers video.

Don't give up on converting Humber. You might yet make it into the DDWFTTW hall of fame! As the Chief has often said, I think you're almost there.

As to ynot's marble, I only vaguely recall that episode but thought it brought out some interesting questions. I asked ynot about the arm holding the cart on the circular mill acting as a tether way back, and he said it wouldn't matter ims. I would still like to see Blackbird's 16g chick self start via the apparent tailwind on a much longer belt, or travel up one for say 100 feet. Who knows? Somebody may do it down the road.

RP,

I was just thinking about your question about self starting when I was passing through an airport a few days ago. They had the "escalator like" people movers which run on a flat surface. I recall Denver and Atlanta airports as having examples.

If those were turned up in speed just a bit, one could probably get the cart set on the entrance end and before it fell off exit end, it should self start and run back up and run off the entrance end. (the entrance and exit being defined by the way people normally use it.) This would provide the appropriate tailwind condition. If any of our demo cart people live near these airports, It might be an interesting (albeit predictable) video.

For those of us who do understand the correct use of inertial reference frames, it wouldn't add much, but a very cute demo, nonetheless.

Regards,

WindGrins

 

[humber]

Oh, you're just making it up as you go along now, Brian.

You point to where you say I agree with him, and write down the formula for "closing velocity" or ask Spork to.
Can you do that Spork? Write a line of math, the is the formula for "closing velocity" of the two cars?

 

[3point14]

You point to where you say I agree with him, and write down the formula for "closing velocity" or ask Spork to.
Can you do that Spork? Write a line of math, the is the formula for "closing velocity" of the two cars?

Yes, I can point you to the part where you agreed with him. You simply missed it. If you go back and read it again you'll see that you were in violent agreement that the relative velocity was 120mph.


ETA This is getting so very far from the point of the thread it's almost surreal.

I did like the bit about kinetic energy being relative (right word?) to the inertial frame. Which I suppose is obvious when you think about it, but I don't know if it would be obvious if I hadn't been told.