Down wind faster than the wind

[John Freestone]

Careful: if we translate the treadmill situation back to real life, we'll see ground all round the cart moving forwards at wind speed.

Not in the southern hemisphere, where they hang upside down. How many bloody times did I check that?!

But this really is irrelevant. We might just as well say that the fact that there's a ceiling in the room and not in the open air has an influence, or that it makes a difference if somebody is standing next to the machine. The essential point in the treadmill test is that local conditions around the cart on the treadmill are exactly the same as they are around a cart on the road running downwind.

I agree, from my humble position of utter ignorance.

Look, this is bugging me, so I'll just come out and say it. I keep getting stuff wrong, and now I'm trying to just either ask questions or clearly say "I imagine...", etc. I am asking reasonable questions, I think, and I am even making statements about the system under consideration that are true. It's hard trying to take part in a discussion with experts. I'm not sure sometimes if it's worth it. I don't know whether it would be better to ban anyone who hasn't got relevant qualifications and then just get on with it. I'm not quite sure, with all the mathematical proof I keep being reminded of, why anyone is interested in building anything or discussing any physical manifestations of the maths. It would be nice, when I ask a question, if it was just answered, rather than being 'corrected'. It would be nice if, when I make a correct statement, it was occasionally agreed with before being pronounced irrelevant. I don't know, perhaps I'm just a human being, wanting a little appreciation and encouragement.

Furthermore, I have a feeling that the reason why building things is important is because the maths we're all supposed to go off and check describes reality as demonstrated, not the other way round. I think you'll find that is why Eddington bothered to go off and see if starlight was shifted by the gravity of the sun, rather than just putting a headline in the paper: "Einstein proves Newton not quite right. I've checked the maths".

Many people who can't "intuitively" see how the thing can work start imagining all sorts of possible complex influences, from vibrations, turbulence or whatever. In fact the physics behind it is simple. We have a good understanding of how propellors work, and more than a century of evidence that they do work on aeroplanes. Once we realise that a propellor is just a device for moving through air (or for moving air past it, which really does amount to the same thing), we can analyse the cart with classic Newtonian mechanics. The analysis shows that it works, just as clearly as an analysis of a bicycle shows that it works.

Yes, but Einstein made a big fuss about the importance of imagination, and it is often having a picture in our heads, rather than being able to balance equations, that inspires the technoligical uses of discoveries. The maths describing the way a bicycle works - did someone work it all out on paper and then invent the thing to demonstrate it?

 

[sol invictus]

I don't know, perhaps I'm just a human being, wanting a little appreciation and encouragement.

JREF is not a nice, polite forum. I like it that way.

Furthermore, I have a feeling that the reason why building things is important is because the maths we're all supposed to go off and check describes reality as demonstrated, not the other way round.

Isn't that precisely what spork and JB did?

I think you'll find that is why Eddington bothered to go off and see if starlight was shifted by the gravity of the sun, rather than just putting a headline in the paper: "Einstein proves Newton not quite right. I've checked the maths".

You've picked the worst possible example. At least according to legend, when Einstein was asked what he would do were Lord Eddington's observations to fail to confirm his theory, he replied "I would feel sorry for the good Lord. The theory is correct."

Most of the debate here has been over whether or not the treadmill test constitutes adequate evidence that the cart will travel faster than the speed of a steady wind. The evidence in favor of that consists of more than four centuries of physics theory and experiment. It is not in doubt - it is a physical law. There is little or nothing in life we can be more certain of.

So while it's fine to discuss it, one needs to be able to distinguish between one's own ignorance of the facts and the facts themselves.

 

[humber]

Um, Humber, I'm a bit behind on this thread, so I'm not sure if anyone has pointed it out yet, but do you realize that your diagram here is wrong?

Whenever a wheel completes one rotation, the cog sharing the axel of that wheel also completes one rotation, and vice versa. Your diagam isn't doing it. The speed of the top wheel in your diagram is exactly the same as the speed of the bottom wheel, which isn't how my little animated cart was geared.

Yes, Brian _M, I do realise that is is not as expected. Comments have been made, but only superficially, and in the usual manner. The idea was to break down all of the gears and wheel so that the all ratios could be seen.

1. You agree, that Ft= Fc?

2. You agree with the internal force ratios?

3. You agre with the internal velocity (turns) ratios?

Because the small cog has half the diameter (or circumference) of the large cog, the large cog will complete half a rotation (in the opposite direction) for every full rotation of the small cog.

Yes, I agree, as I did in an earlier post.

Because the wheels share the same axle as the cogs, they will complete the same number of rotations as the cogs.
So the top wheel rotates half the distance of the bottom wheel in the same amount of time.

Yes, of course, but be aware that there is another common ration. The wheel to the cog, as you know.

Because of the law of conservation of energy, the top wheel has the same amount of energy as the bottom wheel.

If you mean that the work done by the top wheel must equal the work done by the bottom wheel, then yes.

Energy = Force times Distance
Force = Energy/Distance

Yes, but that does not change because of gears. The 'gain' appears when the gears of my diagram are rearranged, so that the applied force results in differential movement of the gears and wheels.

The diagram shows that the original cart is the same as a unity cart, but with the force applied so as to exploit the differential motion of the wheels. The gears set the ratio of that differential. As such, you will gain velocity, but lose acceleration meaning more distance, or however you choose to express it.

So if the top wheel turns half the distance of the bottom wheel, and is applying the same amount of energy it must have twice the force.

If you do not accept that the force applied to the ground is the same as the input, then things will not add up. Taking a gear from the center to the circumference is the same. Agreed? Then the diagram shows the Ft=Fc.
Showing the individual forces makes the diagram ambiguous, and opportunity to add up the vectors incorrectly. "Velocites" and "turns" are freely exchanged, and that sort of thinking leads to error.

The diagram is intended to show the relationship between input and output forces. The velocity of the wheels is also unity. It is equivalent to your cart, and a unity cart.

If we set up four wheels in the same setup as your diagram, the top wheel would turn at exactly the same rate as the bottom wheel, so of course the force would be the same.

That is the point. All geared carts have a unity equivalent.
It is equivalent for the ratios of force and velocity. Your cart is the same, but arranged so that the internal ratios, are externalized, allowing you to take advantage of the differential motion.

As I have said, I agree with the way that you derived the velocity gain, but not the force. That was the main goal to dhow that Ft =Fc.
In terms of force transformation, this is equivalent, Brian_M.

As you have it; Top wheel to Gear 1 (x2). Gear 1 to Gear 2 (x2). Gear 2 to Wheel 2 (x1/4) Answer = 1, Ft = Fc.
There is no "force cancellation", due to the relative velocities. There is one line of force that makes input = output. Wheels and gears are transmissions.

Hell, let's make it simpler and get rid of the wheels altogether. My cart would work exactly the same if it was running with the cogs directly on the surface, so take off the top and bottom wheels on your diagram and tell me what you get.

Yes, it is possible to simplfy this arrangement.

 

[Dan O.]

[humbers reality ignored]

 

[humber]

I was close to that several times, and have speed-read much of what Humber has posted. I have made some of the same errors he makes, but I seem to learn quicker. However... no, I'll save that till the end...

We have the trailer John, how about the film?

Now, the bit of Humber I'm interested in is this: although I absolutely and utterly accept the physical reality of the equivalence of intertial frames of reference (I think I understand that, but may be wrong), there do seem nevertheless to be actual physical differences in this case between the treadmill test and a reasonable reading of the claim. This isn't anything to do with "but there's no wind blowing", but is more akin to considering the limits within which the relevant conditions are equivalent. For instance, to translate correctly the treadmill situation back to real life, would there not be, a few feet beyond the cart, on each side, and some distance ahead and behind it, an indefinitely large piece of ground moving backwards at windspeed? Now, this may be irrelevant or it may not, but it seems to my mind to be true.

The "no wind" is the condensation of many failures of the model. The equivalence idea is banal. If you do make your model precisely the same, then you have two identical systems. Wind tunnels are not exactly like the wind, but a good enough approximation for their purposes. They are modified and improved, as the demand for accuracy increases. The science, the skill, lies not in the trite reversal of vectors, but implementing that operation in the real world.

I am hardly qualified, but will risk comparing this with another objection of Humber's - whether there are real mechanical differences concerning the aerodynamic properties of the cart, that show up when it is on the road and on the cart (which I think he said were about the wind whistling past). <snip>
Another 'real' difference might be that the 'carpark' would have to be folded on itself and travelling backwards at twice windspeed, if I've got my head round it properly, a great river of tarmac and grass, a few meters below. There may be others. My gut instinct is that they're probably of no true consequence (mainly because clever people tell me that math stacks up anyway in ideal situations).<snip>

The model fails, even if the the relative windspeed is agreed to be zero at windspeed. Indeed, so many differences, but only some are of consequence in terms of supporting the faster than wind claim.

I'm not sure whether I want to find a video test of Humber's variation, where the prop is turned upwards, or some other means is used to demonstrate that all that is happening is that the energy of the belt is being dissipated, and hence the model ends up staying 'still', thanks to Newton (if I've misunderstood the argument, Humber, pardon me)...or not. Really. Oh, go on then.

Oh, but I was thinking it would only be a minute's job, but maybe you'd have to rig up a different kind of cart. Down to the hardware store again!

If the propeller is fitted so that it turns according to its bias, then more thrust will be generated. The cart will still stay still.
In practice, I think that friction to the belt will not support such a high load. The cart will go down the belt, using the propeller as an (intermittent) brake.

No need to wonder, we can ask what happened when it was tried.

Not in the southern hemisphere, where they hang upside down. How many bloody times did I check that?!

I wonder how kinetic energy is measured in equivalency-land? Take a static mass, add to it the energy gained from spinning around at the velocity of the Earth's circumference. Accelerate that object, then subtract the previous addition. Useful.

Re: Eddington. It is claimed that he fudged the results, but then Richardson used the same papers to speculate about black holes, while fighting from the trenches of WW1. Interesting, but as relevant to the cart...

ETA:

Dan O
[humbers reality ignored]

Perhaps adequately expressed, but logically flawed.

 

[Dan O.]

Perhaps adequately expressed, but logically flawed.

Is your hold to your own reality is so fragil that you refuse to try even the simplest of math problems? Where is the logic in that?

Here is the problem again: It takes 1 joule of energy to accelerate a pair of 1 kg masses to +1 and -1 m/s. How many joules of energy are required to accellerate the masses to +2 and -2 m/s ?

 

[Michael C]

Dan,
a while back, you posted this:

It stuck in my mind; somewhere I'd already seen something like it. Now I've found it: the Voith Schneider propeller. It works in exactly the same way as your cart. Had you already seen this type of propeller?

It's designed to work in water. I don't know if there is a version that works in air.

 

[ynot]

This is a rough representation of the what I plan to build unless someone else does it first. Unfortunately I won’t be able to even start on it for 5 - 6 weeks so I would be very happy if someone else does do it earlier. I don’t think the circular “road” needs to be any larger than 4 - 6 feet in diametre and can be cut from a sheet of plywood or particle board. The second bogey wheel to hold up the propeller is optional as this can be done from the axle that doesn‘t spin with the wheel. As this would be working in still air it’s the same as working in a steady wind. Very frustrating that I can’t spend any time on it for so long. Thanks for the positive support most have given this idea.

 

[humber]

Is your hold to your own reality is so fragil that you refuse to try even the simplest of math problems? Where is the logic in that?

Here is the problem again: It takes 1 joule of energy to accelerate a pair of 1 kg masses to +1 and -1 m/s. How many joules of energy are required to accellerate the masses to +2 and -2 m/s ?

I see that nobody has responded to your homework assignment, so now you hope to force the issue.
Possible inferences:
(a) Humber can't do algebra
(b) Humber doesn't respond to taunts by self-appointed experts.

ETA:
I know what your intention is Dan O, but we have been through that. It concerns your view of "equivalence". The kinematics of the collisions are not in question, whereas that very narrow view of equivalence is, if for no other reason than it is at the expense of all other factors. The entire time scale is reduced to the moment of impact.
Also, the calculations are very simple. They are text book problems and not relevant to actual modeling, other than being some simplified starting point.
But you know that equivalence if correctly applied, means that there can be nothing gained from doing so. The ground energy idea dates back centuries, and re-appears in one form or another, as a quick review of appropriate patents will confirm.

 

[John Freestone]

JREF is not a nice, polite forum. I like it that way.

We can't both have our way, so have yours. I'll see what I can do.

Isn't that precisely what spork and JB did?

Not according to spork. He said he made some calculations and they convinced him, and then he built a cart.

You've picked the worst possible example. At least according to legend, when Einstein was asked what he would do were Lord Eddington's observations to fail to confirm his theory, he replied "I would feel sorry for the good Lord. The theory is correct."

Do you think Einstein was being serious? And if he was serious, are you holding up a failure of his scientific principle as admirable? You seem to hold a strangely unscientific viewpoint.

ETA: What luck I chose that example.

Most of the debate here has been over whether or not the treadmill test constitutes adequate evidence that the cart will travel faster than the speed of a steady wind.

Yes, but what's the point? If it doesn't do that, it's wrong. You leanred that from Einstein.

The evidence in favor of that consists of more than four centuries of physics theory and experiment. It is not in doubt - it is a physical law. There is little or nothing in life we can be more certain of.

Which kind of makes me wonder which is more irritating, there being controversy around a claim, getting intruiged by that, learning about it, reading 30-odd pages of argument, putting a week of effort into it, riding the belittlement, only to find out it was a scam perpetrated by a bunch of timewasters, or to go through the same only to find out it was absolutely certain, and a bunch of timewasters drip-fed the absolute certainty of that fact by page 37.

ETA: Page 39.

 

[humber]

<snip.
Not according to spork. He said he made some calculations and they convinced him, and then he built a cart.

According to Spork,
"This (Platt's proposal) is even easier to prove than the cart going faster than the wind directly downwind, outdoors."

But now there are problems. There is no need to worry that the experiment will not meet the requirements of faster than wind. Just getting to windspeed will be enough to show that there is something to explain. The experiment can then be refined as appropriate.
Won't happen though.

 

[sol invictus]

We can't both have our way, so have yours. I'll see what I can do.

Good!

Not according to spork. He said he made some calculations and they convinced him, and then he built a cart.

Sorry - I think I misunderstood you before.

Do you think Einstein was being serious? And if he was serious, are you holding up a failure of his scientific principle as admirable? You seem to hold a strangely unscientific viewpoint.

And you hold a very naive view of science. The grade-school version of the scientific method - that one formulates a hypothesis, tests it, and then modifies the hypothesis if necessary - is correct in practice only through (at most) the second step. And in fact philosophers of science argue the progress of science is better served that way, since clinging desperately to evidently failed theories, while it might be bad for most individuals, is occasionally very good for science in the long run.

Yes, but what's the point? If it doesn't do that, it's wrong. You leanred that from Einstein.

My point is that one should know what is at issue. If the treadmill turned out not to model the behavior of the cart in the wind (and not for some obvious reasons like the wind not being as steady as the motion of the treadmill), it would overturn four centuries of physics research. That makes it a very big fish - but one with an incredibly small chance of being true.

I find knowing that very useful; for example, I believe that the odds that my personal intuition is wrong about something are vastly greater than the odds that essentially all of physics is wrong. I don't know about you. I fact I'm even willing to accept that Galileo, Newton, Einstein, every other physicist since, and every experiment were in fact correct, and use their discoveries to make further progress rather than re-inventing the wheel (or the cart?) every time. A novel idea for some in this thread, isn't it?

Which kind of makes me wonder which is more irritating, there being controversy around a claim, getting intruiged by that, learning about it, reading 30-odd pages of argument, putting a week of effort into it, riding the belittlement, only to find out it was a scam perpetrated by a bunch of timewasters, or to go through the same only to find out it was absolutely certain, and a bunch of timewasters drip-fed the absolute certainty of that fact by page 37.

ETA: Page 39.

 

[Dan O.]

Dan,
a while back, you posted this:

[qimg]http://www.internationalskeptics.com/forums/imagehosting/151444929c5360d05e.jpg[/qimg]

It stuck in my mind; somewhere I'd already seen something like it. Now I've found it: the Voith Schneider propeller. It works in exactly the same way as your cart. Had you already seen this type of propeller?

It's designed to work in water. I don't know if there is a version that works in air.

I hadn't heard of that one but I believe I've seen a kite that works on a similar principle.

 

[Marcus]

Have you guys considered doing a more rigorous experiment to prove that the craft can mantain a faster-than-wind speed? Wind speed indicators are small and cheap, you could put 1 on the cart and several along, say, a 1 mile course. Average speed can be determined by measuring time and distance.

Sorry if this has been covered, I haven't had time to read the whole thread.

 

[mender]

But now there are problems. There is no need to worry that the experiment will not meet the requirements of faster than wind. Just getting to windspeed will be enough to show that there is something to explain. The experiment can then be refined as appropriate.
Won't happen though.

Directly downwind faster than the wind. That is the claim. Test that. Stop obfuscating.

 

[Dan O.]

I see that nobody has responded to your homework assignment, so now you hope to force the issue.
Possible inferences:
(a) Humber can't do algebra
(b) Humber doesn't respond to taunts by self-appointed experts.

Humber, your failure is complete.

The cart does travel downwind faster than the wind. This has been shown by video demonstrations, physics and math. That you continue to insist that this is not true shows that you cannot do the simple arithmetic.

 

[spork]

Not according to spork. He said he made some calculations and they convinced him, and then he built a cart.

The calcs I did constituted a very basic vector analysis based on real world measurements (i.e. L/D values that are easily achievable). There was no "theory" involved. That's why I felt quite confident the cart would do as indicated by the analysis. Admittedly, there was a small but finite chance I had made an error in my vector diagram. Had that been the case I might have been very surprised to find the cart would not do what I expected it to do. So in the end, I suppose physical proof is the only real proof. But I can tell you, the analysis was sufficiently simple, and based on such conservative measured values, that I didn't feel the need to build the cart (until JB insisted). By a similar argument, you probably wouldn't have to push a glass of milk off the table to know it's going to fall - although you'd have to do exactly that if you wanted to be truly certain.

Which kind of makes me wonder which is more irritating, there being controversy around a claim, getting intruiged by that, learning about it, reading 30-odd pages of argument, putting a week of effort into it, riding the belittlement...

I'd have to say that looks like a bit of intentional selective memory. You showed up on the scene with insults. When you returned with a better attitude, having studied the thread a bit, everyone treated you with respect. I haven't seen a exception to that.

..only to find out it was a scam perpetrated by a bunch of timewasters, or to go through the same only to find out it was absolutely certain, and a bunch of timewasters drip-fed the absolute certainty of that.

Now you've completely lost me. It's not like we were here laying in wait for you to stumble along with your wrongness and bravado. We posted this interesting toy here, and we are happy to answer questions about it. If people arrive on the scene with insults we (I) respond in kind.

 

[humber]

Humber, your failure is complete.

The cart does travel downwind faster than the wind. This has been shown by video demonstrations, physics and math. That you continue to insist that this is not true shows that you cannot do the simple arithmetic.

No evidence for the first point. The rest shows that you are willing to base that supposed physics and calculation upon an assumption, supported by the flawed model that is the treadmill. I am not sure that adds up.

 

[Dan O.]

Have you guys considered doing a more rigorous experiment to prove that the craft can mantain a faster-than-wind speed? Wind speed indicators are small and cheap, you could put 1 on the cart and several along, say, a 1 mile course. Average speed can be determined by measuring time and distance.

Sorry if this has been covered, I haven't had time to read the whole thread.

The difficulty is in finding a 1 mile stretch of flat road in the same direction as the wind and where the wind will blow steadily for the duration of the test.

There is work in progress for independent testing at this location: http://maps.google.com/?ie=UTF8&ll=37.78615,-122.318085&spn=0.000592,0.001345&t=h&z=20

The alternative though is to mimic the setting in a controlled environment as was done with most of the videos that have been posted to youtube.

 

[humber]

Directly downwind faster than the wind. That is the claim. Test that. Stop obfuscating.

Nevertheless, it was adequate at one point. Make a more modest claim; "at least as fast as the wind".