General > General Technical Chat
Mess with your minds: A wind powered craft going faster than a tail wind speed.
Brumby:
--- Quote from: electrodacus on December 21, 2021, 05:43:46 am ---What happens is that energy is stored as pressure differential (propeller uses some of the wind power to increase pressure differential).
This stored energy while vehicle is below wind speed is then used to accelerate for some limited amount of time above wind speed.
--- End quote ---
I'm beginning to see where you might have overlooked something.
If I am right, what you said here makes sense, but there is an assumption you have made that is incorrect. One which would lead you to a particular conclusion - that looks very much like the sort of thing you have been saying.
Labrat101:
Also you have still forgotten they used a variable pitch propeller on blackbird that If you had watch the video he said he pulled the handle by guess so the
exact angle between reverse & feathering is unknown but I guess it was between 13 16.5 degrees which would give the forward thrust .
So NO your formulae is wrong . :-- :-- :-- :--
PS IF you are thinking of getting a new Job DON'T take up FLYing .. :-DD
gnuarm:
--- Quote from: dunkemhigh on December 21, 2021, 10:56:47 am ---
--- Quote ---We can agree to disagree.
--- End quote ---
What!??!!! After 958 comments? NOOOOOooooooo
--- End quote ---
Lol
I didn't read the whole thread. How long has electrodacus been insisting the car that goes down wind faster than the wind doesn't? How long has he insisted energy involves time and power doesn't?
I find his arguments mildly entertaining. The diagram posted seems to me to be a lot of fluff. Especially amusing is his stored energy argument to explain "impossible actions" when it is just poor construction at work. Then he says a better constructed model has "micro storage" of energy or something.
If the wheels are geared 2:1, applying a force to the 1 wheel by moving the belt it is riding on will exert say 1 unit of force in the direction of the belt. The gearing will result in twice the movement in the 2 wheel and half the force. The two forces are opposite, so the vehicle has a half unit of force pushing it in the direction of the moving belt with the movement relative to the ground being twice the velocity of the movement of the belt.
I'm willing to say I'm wrong when someone shows that to me. Happy to, in fact. But someone who doesn't understand that "rate of change" in regards to values like power and energy fundamentally involves time can't possibly construct a rational argument. While rate of change can refer to some other variable, in the case of power, it is the rate of change of energy wrt time. Power involves time. Energy does not.
This is such an insane argument! I won't argue with the guy because his arguments are so specious, yet I want so badly to help him understand. But I'm not going to chase impossible dreams. They guy clearly does not want to understand, so no one can help him.
Brumby:
A question, if I may....
Let's say the Blackbird has gone through all this "energy storage" exercise and has been running along the ground for long enough that the "stored energy" is all gone. We are looking for the steady state where the speed is constant - no acceleration nor deceleration. (I don't care how long this will take as we can imagine a test track as long as we want and a nice, consistent wind.)
electrodacus - what do you say it's speed will be?
1. Greater than wind speed
2. Equal to wind speed
3. Less than wind speed
gnuarm:
--- Quote from: Brumby on December 21, 2021, 02:51:13 pm ---A question, if I may....
Let's say the Blackbird has gone through all this "energy storage" exercise and has been running along the ground for long enough that the "stored energy" is all gone. We are looking for the steady state where the speed is constant - no acceleration nor deceleration. (I don't care how long this will take as we can imagine a test track as long as we want and a nice, consistent wind.)
electrodacus - what do you say it's speed will be?
1. Greater than wind speed
2. Equal to wind speed
3. Less than wind speed
--- End quote ---
This has probably already been posted, but there is a second video with much more detail that should convince any doubter. It settled a $10,000 bet which was won by the guy making the video saying the downwind car will go faster than the wind.
The car will ultimately run faster than the wind.
In the first video the car was not just running faster than the wind, it continued to accelerate. How much energy is stored in the pressure waves or whatever is imagined?
It's a shame they don't have a larger test facility to clearly dispel this stored energy myth.
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