Merged DDWFTTW in a “Real” Wind

[humber]

Wrong.



Lie.

JB

You don't have an official weight, and the post is where you once again lied to cover up for that. M'kay?
I am not going to look for that post, because of your liturgical history of mendacity. M'kay?

 

[Subduction Zone]

Nonsense. All of the prop moves forwards at once. Anything else as written above, it the result of an over-active and erroneous imagination, brought about by the need to support a failed idea.

Since humber does not understand the simple concept of relative velocity there is no way that he could see that the surface of a rotating propeller could impart a force to air. But then that means he cannot understand how a propeller imparts a force on air. He probably thinks it is some sort of magic and lets it go at that. In the humberverse magic is okay, if spork isn't the one doing it.

 

[humber]

Well, except that his link was only presented to prove your blatently misrepresented '*theoretical* straight chain' assertion wrong.

And it did.

If you don't like being 'dirty', do your research better.

JB

The tensioner wangs up and down with the flexing tower, and you have no hope whatsoever of claiming the efficiencies of that article.
If you had any engineering knowledge, you would know that is a naive to expect that of a long twisted chain.

 

[humber]

Wrong.



Wrong.



Wrong.




You seem to have gotten it backwards. Ask the question before coming to all your wrong conclusions and telling us we have it all wrong.

Ynot is absolutely right, and you have based your loss calculations of the submission upon the same. The days when you could give a simple no, have long passed, and you are being questioned to see what you know.

The near constant acceleration of 1.1m/s clearly shown in the trial data implies a constant force of 32N, whereas your theory produces much larger figures, and is not constant with cart velocity.
You are always saying the empirical evidence trumps theory, so you have been not only trumped, but lost the game.

 

[Llyricist]

Is it posted here? I didn't see it. I would be most obliged if I can examine it, thank you!

Okay let's take a hypothetical cart weighing 295 kg, and give it the type of efficiency you think is appropriate and push it up to 9 m/s in a 7 m/s tail wind.

Using a crr of .02 (which is about twice that of a car tire on concrete) I'll have a rolling resistance of 57.8 Newtons. (crr * mass * 1G)

Using a Cd of .7 (the same as a Caterham open wheeler) and a frontal area of 2 m², gives a drag force of 3.43 Newtons at the 2 m/s airspeed.
(Fd = .5 * air density (1.225 standard day at sea level) * Cd * Frontal area * airspeed²)

For a total opposing force of 61.23 Newtons.

I'll let a (theoretical at this point) 4.876 meter (16 foot) diameter prop through a drive train that is 80% efficient, add an additional 83.4 Newtons of opposing force. So we have the prop, through the drive train doing negative work on the cart at the rate of 83.4 N * 9 m/s = 750 W.

Since the drive train is only 80% efficient the prop only gains 600 W of power from its negative work. At his level of power and this airspeed the theoretical maximum efficiency for a prop of this size is 64.5%, so I will give it 12% less than that, which is more than I should (see this page for formulas and explanations). So the prop efficiency is 52%. 600 W * .52 = 312 W of power to the air.

312 W / 2 m/s = 156 Newtons of thrust.

with a total opposing force of 83.4 Newtons from the prop's rotational drag and drive train,
plus 57 Newtons of rolling resistance,
plus 3.43 Newtons of aerodynamic drag
equals 143.83 Newtons
acting against a thrust of 156 Newtons, giving a net acceleration force of 12.17 Newtons.

There you have it. A total piece of crap that can accelerate beyond wind speed directly down wind.

 

[humber]

.... five meter(plus) long chain, in an outdoor environment with sand and dirt, twisted between two sprockets that are at right angles to each other, kept in place with home-made chain tensioners,

The "tensioner" is as crude as it gets. A tether, and some skate wheels once used in the hilarious "counter-rotation" video.

no possible hope of optimum alignment or tension, a chain that has a history (yes I can read) of breaking and bending sprockets out of whack, THAT chain, is somehow comparable to the chain in the lab? Do you think THAT chain drive was/is 90% efficient? Try a little honesty here, instead of trying to find hidden meanings in my posts.

The Makey-Breaky cart, with the "torque of a Corvette".

 

[humber]

A: The 98+% is achieved for real, not just in theory (everyone here knows exactly how you meant that.)

B: According to your "theory" of correctness, this statement would also have been just as valid. "... theoretical efficiencies of over 10%".

You're the only one who believes your story.

JB

And why would you worry? Just dial up some more power from the wheel. The Harrypothesis is a risible delusion.

 

[profpangloss]

Okay let's take a hypothetical cart weighing 295 kg, and give it the type of efficiency you think is appropriate and push it up to 9 m/s in a 7 m/s tail wind.

Using a crr of .02 (which is about twice that of a car tire on concrete) I'll have a rolling resistance of 57.8 Newtons. (crr * mass * 1G)

Using a Cd of .7 (the same as a Caterham open wheeler) and a frontal area of 2 m², gives a drag force of 3.43 Newtons at the 2 m/s airspeed.
(Fd = .5 * air density (1.225 standard day at sea level) * Cd * Frontal area * airspeed²)

For a total opposing force of 61.23 Newtons.

I'll let a (theoretical at this point) 4.876 meter (16 foot) diameter prop through a drive train that is 80% efficient, add an additional 83.4 Newtons of opposing force. So we have the prop, through the drive train doing negative work on the cart at the rate of 83.4 N * 9 m/s = 750 W.

Since the drive train is only 80% efficient the prop only gains 600 W of power from its negative work. At his level of power and this airspeed the theoretical maximum efficiency for a prop of this size is 64.5%, so I will give it 12% less than that, which is more than I should (see this page for formulas and explanations). So the prop efficiency is 52%. 600 W * .52 = 312 W of power to the air.

312 W / 2 m/s = 156 Newtons of thrust.

with a total opposing force of 83.4 Newtons from the prop's rotational drag and drive train,
plus 57 Newtons of rolling resistance,
plus 3.43 Newtons of aerodynamic drag
equals 143.83 Newtons
acting against a thrust of 156 Newtons, giving a net acceleration force of 12.17 Newtons.

There you have it. A total piece of crap that can accelerate beyond wind speed directly down wind.

Thanks for that. I will print it out, go over it in some detail and comment on it. If I agree, I will let you know and the same goes if I don't. Fair enough? Thanks again!

 

[temporalillusion]

I don't say this often but when it comes to trolls, humber is truly is a class by himself; the others don't even come close.

Though it was interesting to see him become more shrill and overt in the past few pages when people were talking amongst themselves.. that's the only real option, leave humber be to do his analysis and submit his report and ignore the provocations.

 

[Subduction Zone]

You don't have an official weight, and the post is where you once again lied to cover up for that. M'kay?
I am not going to look for that post, because of your liturgical history of mendacity. M'kay?

Or official color, don't forget that humber. And what astrological sign does the Blackbird have? Not to mention what feng shui,

 

[CORed]

Or official color, don't forget that humber. And what astrological sign does the Blackbird have? Not to mention what feng shui,

Well, since there's no official weight, how do we know that spork and company didn't achieve their phony record by using a cart with negative mass?

(Just as plausible as humber's "tacking and wind gradients" explanation)

 

[humber]

With a IMAGINARY 90% drive train efficiency, fresh BMX tires, Cd of .365, the prop operating at an IMAGINARY 89% efficiency with a theoretical max of 93%. I'm getting:
26 horsepower at the shaft, 569 ft lbs torque, and 228.8 lbs of thrust, and a 10 newton net acceleration force.

And you forgot tyre power losses. This is a test report for a tire with an 85kg rider over two wheels at 18mph on smooth steel drum. A cart of 295kg at 28mph on dirt, will be much much higher.

 

[CORed]

Though it was interesting to see him become more shrill and overt in the past few pages when people were talking amongst themselves.. that's the only real option, leave humber be to do his analysis and submit his report and ignore the provocations.

It also seems that the last few pages have laid to rest humber's "the carteers haven't provided any math" complaint.

 

[humber]

Well, since there's no official weight, how do we know that spork and company didn't achieve their phony record by using a cart with negative mass?

(Just as plausible as humber's "tacking and wind gradients" explanation)

I note that you have understood the difference between a tacking boat and the cart in the wind, so I need not bother to address your remarks at all.

 

[Llyricist]

And you forgot tyre power losses. This is a test report for a tire with an 85kg rider over two wheels at 18mph on smooth steel drum. A cart of 295kg at 28mph on dirt, will be much much higher.

The weight is part of the calculation. the surface probably does make a difference, but how much? You don't know any better than I do.

 

[Subduction Zone]

And you forgot tyre power losses. This is a test report for a tire with an 85kg rider over two wheels at 18mph on smooth steel drum. A cart of 295kg at 28mph on dirt, will be much much higher.

Nope, Tire power losses is mostly through rolling resistance which he calculated. The rest is through bearing losses and that is minimal on a vehicle like this one.

 

[humber]

how about a video of it actually doing it. Surely reality trumps mathematics?

How about that changing wind, eh? The cart is obviously never ddw, and a lot less so than TAD's deceptively manicured chart, presented for publication suggests. The constant acceleration is not predicted by the theory, so the theory is wrong, and your above statement implies that you must agree.

 

[humber]

I don't say this often...

You hardly ever stop saying it, and sent me a series of disturbingly frenetic PM's to add to that.
This thread is no more technical that it was, thanks to ProfPangloss. I have an electrical model to add to whatever is next produced, Harold's DE, Yevhgeni's calculation, and the argument from momentum. There is little room for village gossips.

 

[Subduction Zone]

How about that changing wind, eh? The cart is obviously never ddw, and a lot less so than TAD's deceptively manicured chart, presented for publication suggests. The constant acceleration is not predicted by the theory, so the theory is wrong, and your above statement implies that you must agree.

What constant acceleration? The acceleration of the cart varied. It was always accelerating, but that is predicted as long as the cart is below the speed that it would get from its advance ratio.

 

[ThinAirDesigns]

You don't have an official weight, and the post is where you once again lied to cover up for that. M'kay?
I am not going to look for that post, because of your liturgical history of mendacity. M'kay?

Wrong.

Lie.

JB