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Newton's third law problem.

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bdunham7:

--- Quote from: electrodacus on November 27, 2022, 10:04:29 pm ---One link shows the equation the other is a calculator using that equation and that equation will provide you with any question you may have about power needed to overcome drag when driving upwind and it can also calculate the max wind power available to vehicle when driving downwind.

--- End quote ---

Nope, every word of that is entirely wrong.

electrodacus:

--- Quote from: bdunham7 on November 27, 2022, 10:08:05 pm ---
Nope, every word of that is entirely wrong.

--- End quote ---

That is your unqualified opinion.  You will need to measure and prove it is not true assuming you even understand what you will need to measure and 3.5 digit will be enough :)

PlainName:

--- Quote from: electrodacus on November 27, 2022, 07:54:25 pm ---
--- Quote from: PlainName on November 27, 2022, 07:18:41 pm ---
a) How did you derive those terms? You could post anything and say that's correct, or copy anything and say it's correct "because someone else uses it too", but unless you know how the terms were derived it's meaningless to you.

b) Which term(s) cover the propeller and wheel operation? The propeller, and connection to the wheels, is kind of super-important since it's the thing that makes it work, and yet it doesn't exist in your copied equation. How can that equation possibly account for it, then?

--- End quote ---

a) not only I know how that is derived but also know it is correct as I build things not just play with numbers.

--- End quote ---

So tell us then. Show us your workings so we can go "Doh! Of course, now we can see it."


--- Quote ---b) The equation for available wind power to any wind power vehicle is independent of the design other than shape and area interacting with air particles.
The wheel propeller connection is a separate issue ...

--- End quote ---

It isn't a separate issue. Consider two scenarios:

1. The propeller blades are perpendicular to the wind. In this case the propeller might as well be a flat surface with area the same as the blades, and the power sucked from the wheel (if that's what you think happens) will be near enough zero.

2. The propeller blades are parallel to the wind. In this case the propeller is more or less non-existent so far as the wind pressure is concerned, but it is sucking maximum power from the wheels.

How can you say it's irrelevant when it can affect the system so much?

electrodacus:

--- Quote from: PlainName on November 27, 2022, 10:23:31 pm ---
--- Quote ---b) The equation for available wind power to any wind power vehicle is independent of the design other than shape and area interacting with air particles.
The wheel propeller connection is a separate issue ...

--- End quote ---

It isn't a separate issue. Consider two scenarios:

1. The propeller blades are perpendicular to the wind. In this case the propeller might as well be a flat surface with area the same as the blades, and the power sucked from the wheel (if that's what you think happens) will be near enough zero.

2. The propeller blades are parallel to the wind. In this case the propeller is more or less non-existent so far as the wind pressure is concerned, but it is sucking maximum power from the wheels.

How can you say it's irrelevant when it can affect the system so much?

--- End quote ---

1 and 2.  Do you even read what I write ?
"independent of the design other than shape and area interacting with air particles"

I see your interest is in the direct downwind faster than wind vehicle and blackbird to be specific as the same thing can be done without any propeller and in that case the propeller is
a) a sail with increasingly large effective area as the rotational speed increases.
b) propulsion device
c) part of the energy storage device.


The discussion here is much more basic and asks the amount of wind power available to any wind powered vehicle. All you need to know about vehicle design is shape (so drag coefficient) and vehicle area facing the wind.
You seems to disagree with that based on your false impression that above wind speed direct downwind blackbird is powered by wind (not the case).
While blackbird is above wind speed it is powered by stored energy only. And yes that means acceleration rate will drop if you can not control the rate at witch you use that stored energy. With the blackbird you can control that as pilot can change the propeller pitch. The treadmill model has no pitch control so on that it will be very easy to observe decrease in acceleration rate as stored energy is used up.

PlainName:

--- Quote --- The treadmill model has no pitch control so on that it will be very easy to observe decrease in acceleration rate as stored energy is used up.
--- End quote ---

And yet the videos showed them accelerating. Must've been accumulating energy for storage, eh.

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