Merged DDWFTTW in a “Real” Wind

[profpangloss]

Does profpangloss not work on Sundays? I'm waiting to hear from him with his straightforward analysis in the earth-stationary frame.

Sorry, fttw, but I had a choice between getting in a round of golf, or sitting here working on mathematics to disprove something I saw on an Internet forum. Guess which one I chose?

I will get around to posting my analysis when it is done, but from what I have seen here recently, I don't expect much positive response to it.

Incidentally, the analysis pasted here that came from Talk Rational, is NOT mine, and for that reason you will not see me defending it. There are clearly some parts of it that will fit into my own analysis, but as I said, I will be basing mine on the supposed "proof of concept" that was presented in the Appendix to the NALSA submission report.

 

[humber]

That's a halibut story you told about that gentleman's sole!

WindGrins

Ah.....sole.
It seems that NALSA are a bit reluctant to commit.

 

[profpangloss]

I thought the first part made sense. I don't see why if the thrusts work out you need to go on to consider the energy, but if you do, I think adding in extra drag at the rear wheel to get the 174N figure is incorrect. If that was the real drag at the rear wheel it should have been used in the first place instead of assuming 1kW and calculating 110N. That would make both analyses indicate that the cart would slow down; however even that, because of the real-world inefficiencies assumed in the analysis, wouldn't speak to the physicality of the situation.

Without getting into the merit of that particular analysis, I do think that examining forces alone without considering energy, is a mistake in this case. If you consider that the thrust force is only developed providing the cart can move a certain distance and the cart cannot move that distance if it does not have sufficient energy, then you can see that the force is dependent on the energy being there.

Two things you might give some thought to:

1). Because force is the time derivative of momentum, the concept of force is redundant and subordinate to the conservation of momentum, and is not used in fundamental theories.


2). A consequence of the law of energy conservation is that perpetual motion machines can only work perpetually if they deliver no energy to their surroundings.

I think you will find a 295 kg cart, moving faster than the wind it is in, must give up energy to its surroundings, including to the wind that is supposed to be powering it!

 

[humber]

2). A consequence of the law of energy conservation is that perpetual motion machines can only work perpetually if they deliver no energy to their surroundings.

http://en.wikipedia.org/wiki/Perpetual_motion
Perpetual motion of the third kind
A more obscure category is a perpetual motion machine of the third kind, usually (but not always)[3] defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever (due to its mass inertia). Third in this case refers solely to the position in the above classification scheme, not the third law of thermodynamics. Although it is impossible to make such a machine,[4][5] as dissipation can never be 100% eliminated in a mechanical system, it is nevertheless possible to get very close to this ideal (see examples in the Low Friction section). Such a machine would not serve as a source of energy but would have utility as a perpetual energy storage device


There are other more general types;
Type 5
Absurd even to most enthusiasts: a careless or incomplete attempt.
i.e. Objectively Dubious

Humbergrins.

 

[3point14]

I'll be happy to do that, in detail, but I don't want to go to all the trouble if the basic premise of using the ground as the stationary reference for an inertial frame is going to be rejected out of hand, making all the mathematical work a waste of my time. That is why I need to get this argument settled first.

I haven't finished reading past this one, but I think I see the trouble.

The defined inertial reference frame moves in a given direction at a give rate.

You choose a reference frame in line with the ground then they're both moving at the same rate in the same direction, but (and this is the bit I think profpg doesnt' get) they're not tied together. The frame has to keep moving in the same direction at the same rate for the maths to work, but if a force acts on the gound and pushes it backwards then the ground is out of synch with the reference frame such that the ground is moving within the frame.

It's not that hard, but the absolute compulsion of some to disagree with everything they possibly (and impossibly) can makes it much more difficult to communicate this stuff.

 

[A.T.]

You choose a reference frame in line with the ground then they're both moving at the same rate in the same direction, but (and this is the bit I think profpg doesnt' get) they're not tied together. The frame has to keep moving in the same direction at the same rate for the maths to work, but if a force acts on the gound and pushes it backwards then the ground is out of synch with the reference frame such that the ground is moving within the frame.

That's why it's better to use instantaneous calculations:
http://www.internationalskeptics.com/forums/showpost.php?p=7185375&postcount=6022

 

[jduffy77]

http://en.wikipedia.org/wiki/Perpetual_motion
Perpetual motion of the third kind
A more obscure category is a perpetual motion machine of the third kind, usually (but not always)[3] defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever (due to its mass inertia). Third in this case refers solely to the position in the above classification scheme, not the third law of thermodynamics. Although it is impossible to make such a machine,[4][5] as dissipation can never be 100% eliminated in a mechanical system, it is nevertheless possible to get very close to this ideal (see examples in the Low Friction section). Such a machine would not serve as a source of energy but would have utility as a perpetual energy storage device


There are other more general types;
Type 5
Absurd even to most enthusiasts: a careless or incomplete attempt.
i.e. Objectively Dubious

You forgot the special Humber type. The utterly failed perpetual motion machine. A PM machine so flawed that it excels at something else entirely, you know, like the failed upwind cart.

Examples of failed PM machines which fall into this category:

The space shuttle - failed wheat storage PM machine
Refrigerators - failed PM central heating PM device
The BB - failed upwind PM machine
Submarines - failed PM dirigible

 

[3point14]

Could Profpangloss please present his argument "in neat", so to speak?

He doesn't do that. He won't explain why.

 

[humber]

You forgot the special Humber type. The utterly failed perpetual motion machine. A PM machine so flawed that it excels at something else entirely, you know, like the failed upwind cart.

Proven to what? Not very committal in support.

 

[3point14]

We completely agree. Once you prove that input exceeds output (at zero losses), then it's an engineering problem rather than a physics problem.

In this case, one can pick whatever efficiency numbers one wants to use (even 99% losses) and it can still be shown to work given a high enough wind speed and a low enough multiple (for instance, 1,000.001mph in a 1,000 mph wind).

JB

I'd love to watch the practical demonstration of that one.

Perhaps on film, after the event, from a way away.

 

[drewid]

Proven to what? Not very committal in support.

Once more in English?

 

[ThinAirDesigns]

I'd love to watch the practical demonstration of that one.

Perhaps on film, after the event, from a way away.

Watch close, it happens quick.

JB

 

[humber]

This is a plot of the vane on the CV. The jumps are there for various reasons. I have relocate them to align with the remainder.

It can still be seen, that the vane moves over a range of 100 degrees, and that is typical.

I have asked NALSA why that can be considered to be suitable condition for ddw testing.
There are other discrepancies in the data, its handling and processing, which can not be accounted for.

That may be expected when there is no prior experience with ddw, nor test runs, nor verification. Sailing has a long history of proven methods to call upon, whereas this form of ddw does not.

Without open discussion of the methods, TAD had too much influence on the procedure, and that will be a bias against future competitors.

The best course of action would be to run the trial again under more suitable conditions, and with the appropriate equipment.

 

[humber]

After the response to my email, NALSA will be paying some attention to this forum, and will be able to better judge the validity of the theory and the trial, than they previously were.

 

[fttw]

Sorry, fttw, but I had a choice between getting in a round of golf, or sitting here working on mathematics to disprove something I saw on an Internet forum. Guess which one I chose?

I'd choose the Golf, personally - if I played golf.

I will get around to posting my analysis when it is done, but from what I have seen here recently, I don't expect much positive response to it.

I can't speak for anyone else, but I'll look at it and see if I can see any holes in it. No more, and no less.

Incidentally, the analysis pasted here that came from Talk Rational, is NOT mine, and for that reason you will not see me defending it. There are clearly some parts of it that will fit into my own analysis, but as I said, I will be basing mine on the supposed "proof of concept" that was presented in the Appendix to the NALSA submission report.

Fair enough.

 

[drewid]

After the response to my email, NALSA will be paying some attention to this forum, and will be able to better judge the validity of the theory and the trial, than they previously were.

I wonder what sort of character they will read into your responses scattered throughout the thread ?

 

[fttw]

Without getting into the merit of that particular analysis, I do think that examining forces alone without considering energy, is a mistake in this case. If you consider that the thrust force is only developed providing the cart can move a certain distance and the cart cannot move that distance if it does not have sufficient energy, then you can see that the force is dependent on the energy being there.

I'm sorry, I don't really understand that point. It may not be important to your forthcoming analysis, in which case don't sweat trying to get me to understand it.

Two things you might give some thought to:

1). Because force is the time derivative of momentum, the concept of force is redundant and subordinate to the conservation of momentum, and is not used in fundamental theories.

Hmm. To the extent I understand *that*, I don't agree. An analysis of the forces on the cart should be sufficient to demonstrate that it will work, or won't work (subject to whatever frictional forces you assume etc.)

One glaring thing I didn't like about the previous analysis was that a force analysis suggested it would work, but an energy analysis suggested it wouldn't. Your point is that the analyses are distinct; my point is that they're two ways of looking at the same physical system, and they should be consistent. The inconsistency I found was that the drag force was taken as 110N in the force analysis, and then "corrected" in the energy analysis to 174N. Whereas the same figure should apply to both. (I make no judgement as to which - if either - figure is correct.)

2). A consequence of the law of energy conservation is that perpetual motion machines can only work perpetually if they deliver no energy to their surroundings.

Agreed.

I think you will find a 295 kg cart, moving faster than the wind it is in, must give up energy to its surroundings, including to the wind that is supposed to be powering it!

Well, if I agreed with that a priori I would be taking the cart before the horse, so to speak. I'm prepared to look at your analysis that says it must be so however, and I look forward to the opportunity to do so.

 

[fttw]

Regarding that analysis also, I agree with 69dodge (and maybe others, there are a lot of posts and I may have missed some) who said:

I don't believe 9 m/s is the right speed to use here. That's the cart's speed relative to the ground. But the propeller exerts a force on the air, not on the ground. Since the propeller's thrust is moving the propeller through the air at only 2 m/s, only (160 N)(2 m/s) = 320 Watts of power is required.

As an alternative view, you may (if you wish) take the "point of application of the thrust" of the propeller on the air as moving at 9m/s but you must then also account for an extra source of energy which is the equal-and-opposite force of the air on the propeller, and the point of application of that force moves forwards at 7ms. The difference between the two gives the same 320W.

 

[Subduction Zone]

Sorry, fttw, but I had a choice between getting in a round of golf, or sitting here working on mathematics to disprove something I saw on an Internet forum. Guess which one I chose?

I will get around to posting my analysis when it is done, but from what I have seen here recently, I don't expect much positive response to it.

Incidentally, the analysis pasted here that came from Talk Rational, is NOT mine, and for that reason you will not see me defending it. There are clearly some parts of it that will fit into my own analysis, but as I said, I will be basing mine on the supposed "proof of concept" that was presented in the Appendix to the NALSA submission report.

One of the reasons that Harold is always making new sock puppets is that after a while he gets tired of sticking his foot in his mouth. He thinks that creating a new on line name will get rid of the taste. It never does. By the way, note to the moderators, I am not insinuating in anyway that ppg is Harold. I am only making a note about the analysis that ppg was talking about.

 

[humber]

I wonder what sort of character they will read into your responses scattered throughout the thread ?

You mean Spork?

Who was delighted at Ynot's misfortune in loosing his house and projects?

Who posts personal PM's and email addresses?

Who has more than 50 times claimed I have alexia, and made fun of it?

Three times wished others to be dead?