Author Topic: Mess with your minds: A wind powered craft going faster than a tail wind speed.  (Read 147172 times)

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Offline Labrat101

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Any thing that spinning will ,& does also produces centrifugal force this has also seams to be forgotten.

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Offline electrodacus

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We lose some power to spin the propeller, but we gain it (some?) back because it is now easier to move forward.
like we decrease drag, so we can go a little faster using same power.
I see it like we move energy around in the system, but the total is still pretty much the same (minus some loss here and here).
We make something less efficient (spinning the thing isn't free) but make something else more efficient (lower pressure infront of us, woho here we come).
so the total energy is the same for the 2 cases, but the speed isn't. How much difference? Now is where all the %'s come in.
But I still see it as "possible" to go faster without "cheating". Or where did my thoughts go wrong?

The only source of energy is wind.
Wind can power the vehicle only as long as vehicle speed is lower than wind speed.
To exceed wind speed you need to store energy else is just not possible for the vehicle to exceed wind speed.
It is simple to test just wait until vehicle acceleration speed drops to zero then see how vehicle decelerates.
No test has done that so with the incomplete tests come wrong conclusion about what the test showed.

Online IanB

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But I still see it as "possible" to go faster without "cheating". Or where did my thoughts go wrong?

You didn't go wrong anywhere. For a simple sail, you take the difference between vehicle speed and wind speed. When there is a propeller connected to the wheels, then you have wind speed minus vehicle speed plus propeller speed. You are not getting something for nothing as the vehicle is still being pushed along by the wind, and all the power required is coming from the wind.

It's a bit like gearing on a bicycle. If you change to a higher gear, you can go faster, but you have to push harder on the pedals. As long as the wind can push hard enough, the vehicle can keep going faster.
 

Offline cgroen

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The only source of energy is wind.
Wind can power the vehicle only as long as vehicle speed is lower than wind speed.
To exceed wind speed you need to store energy else is just not possible for the vehicle to exceed wind speed.
It is simple to test just wait until vehicle acceleration speed drops to zero then see how vehicle decelerates.
No test has done that so with the incomplete tests come wrong conclusion about what the test showed.

Repeating something that is wrong over and over and over does not make it right.
I'm extremely impressed with the knowledgeable people here that tries again and again to make you realize that you are soooo wrong. It takes an impressive amount of patience to do what they do.
Now, I could handle it if you were "just wrong", but the "god-like" way you try to convince people about that they are wrong and you are right "because you say so", is really something that turns my stomach around  |O
 

Offline electrodacus

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Repeating something that is wrong over and over and over does not make it right.
I'm extremely impressed with the knowledgeable people here that tries again and again to make you realize that you are soooo wrong. It takes an impressive amount of patience to do what they do.
Now, I could handle it if you were "just wrong", but the "god-like" way you try to convince people about that they are wrong and you are right "because you say so", is really something that turns my stomach around  |O

I'm sorry if you can not understand complex dynamic interactions.  The only way it will convince you is a test.
Tho even with a test you may not understand what happens as I showed a very clear example for the direct upwind version and people still try to find some other alternative explanations of what happens when it seems super clear what it happens there.

Offline cgroen

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Repeating something that is wrong over and over and over does not make it right.
I'm extremely impressed with the knowledgeable people here that tries again and again to make you realize that you are soooo wrong. It takes an impressive amount of patience to do what they do.
Now, I could handle it if you were "just wrong", but the "god-like" way you try to convince people about that they are wrong and you are right "because you say so", is really something that turns my stomach around  |O

I'm sorry if you can not understand complex dynamic interactions.  The only way it will convince you is a test.
Tho even with a test you may not understand what happens as I showed a very clear example for the direct upwind version and people still try to find some other alternative explanations of what happens when it seems super clear what it happens there.

Thanks for confirming my post  :palm:
 

Offline Brumby

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"extra thrust" ?  You get that vehicle is only powered by wind ? There is no extra thrust and all the thrust as in the case of a sail is provided by the wind.
But the propeller is spinning.  A spinning propeller pushes air.  This is called thrust and it must exist in the local region around the propeller.  Surely this thrust has an effect when applied to the surrounding air.

If propeller has no input power or if the input power is taken from the output power (always smaller than input) then vehicle will just slow down and not accelerate.

You skipped over the question.

I asked about the interaction between this thrust and the surrounding air.
 

Offline electrodacus

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You skipped over the question.

I asked about the interaction between this thrust and the surrounding air.

There is nothing skipped.
Propeller will create a pressure differential thus energy is being stored.
After vehicle exceeds wind speed this stored pressure differential is the only thing powering the vehicle.
When this pressure differential drops below the level that it can cover the vehicle friction losses the vehicle will start to slow down.
All the energy that vehicle is using is provided by the wind before vehicle exceeds wind speed since above wind speed there is no longer any wind power available.

Offline MikeP

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 Friends, I found this thread by accident. There appears to be no consensus. 54 pages is beyond my strength, but I saw the film. This is incredible! New horizons are before us!

 Unfortunately, I still have questions. First of all - the car moves faster than the wind, that is, it moves in the oncoming air flow ?! Tell me, why is this impossible with complete calm? After some initial impulse, of course. No, no, a perpetual motion machine is impossible.

 And one more thing, it seems to me that the ribbon (speed indicator) is in the aerodynamic shadow (or inside the vortex) and much lower than the propeller, where the wind is slower.

 Finally, regarding the background for the invention. Under certain conditions, the movement of a sailboat at an angle to the wind can have a higher speed than the wind. But not in the direction the wind is blowing!

 

Offline electrodacus

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Friends, I found this thread by accident. There appears to be no consensus. 54 pages is beyond my strength, but I saw the film. This is incredible! New horizons are before us!

 Unfortunately, I still have questions. First of all - the car moves faster than the wind, that is, it moves in the oncoming air flow ?! Tell me, why is this impossible with complete calm? After some initial impulse, of course. No, no, a perpetual motion machine is impossible.

 And one more thing, it seems to me that the ribbon (speed indicator) is in the aerodynamic shadow (or inside the vortex) and much lower than the propeller, where the wind is slower.

 Finally, regarding the background for the invention. Under certain conditions, the movement of a sailboat at an angle to the wind can have a higher speed than the wind. But not in the direction the wind is blowing!

What film have you seen ?  The one made by Derek / Veritasium ?

It is not impossible as demonstrated to drive faster than wind direct down wind but the way that happens is by storing energy before exceeding wind speed and then using that stored energy to exceed wind speed for a limited amount of time.

Online IanB

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Finally, regarding the background for the invention. Under certain conditions, the movement of a sailboat at an angle to the wind can have a higher speed than the wind. But not in the direction the wind is blowing!

In fact, certain racing yachts can beat the wind: they can get from A to B faster than a balloon carried by the wind could achieve. This is done by sailing at an angle to the wind and using the action of the keel pushing against the water to make the boat move incredibly fast (for a visual analogy, consider pushing down hard on a marble on the table until it pops out sideways).
 

Online IanB

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Friends, I found this thread by accident. There appears to be no consensus. 54 pages is beyond my strength, but I saw the film. This is incredible! New horizons are before us!

Certainly there is consensus. A set of equations describing how to design such a vehicle has been put together using established principles of physics, and accepted as correct by qualified professors of engineering. Both full size and scale models have been constructed and shown to work.

This was first done as long ago as 1969. Reference here: https://projects.m-qp-m.us/donkeypuss/wp-content/uploads/2009/06/Bauer-Faster-Than-The-Wind-The-Ancient-Interface.pdf
 
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Online Kleinstein

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It is 100% not possible on a racing bike with wind blowing in gusts.
The highest gear ratio (53/39 + 25 cassette + 60rpm) puts you at 12km/hr. Try to pedal at 6rpm (10s per rotation) with any power.
If you were crazy enough to build a high enough gear ratio, and have guides preventing the bike from falling over, it should work.

Keep in mind, as pointed out to you already, moving 0 km/h takes ZERO power. So its a matter of interpolating after that point. 0.001km/h might take 1W say. It sounds "wrong" but its not.

Not quite sure you understand.
I provide you with a bike that has no brakes and put you in a head wind of 36km/h. If you input no power your bike will accelerate in theory up to wind speed 36km/h in practice it will be less than that due to friction.
So in order for you to keep some speed around 0km/h relative to ground (exactly 0 will not be practical same as balancing something on the edge of a knife) but some arbitrary low speed 1km/h or 2km/h against the head wind will require 300W.
In the other direction direct down wind with friction brakes enabled to maintain 1 or 2km/h the friction brakes will need to be capable to dissipate around 300W as heat.
A bike that is not moving because is anchored to the ground has nothing to do with this problem as you basically become one with the earth and so that power accelerates the earth rotation witch considering the earth mass is just ridiculously low and nobody will ever care about that and so earth is just considered stationary.

When going at a very low speed, that is low RPM on the pedeal on will not be able to get 300 W. The driver has the same problem as the vehicle: it is hard to get the same power, as the forces have to go up.
The problem why going 1 km/h again a 40 km/h head wind with a normal bicyle is not possible is not because the 300 W are needed, but because it is hard to produce even 30 W at such a low speed, as this needs very high force.
The is just not enough force to produce 100 W at a very low speed. So if the magic (..)³ expression would be true one would never be able to start from a stand still aginst any headwind. One allways starts with infinitesimal low speed and thus infintesimal small (essentially zero) mechanical power.

There is no need to repeat the supposed formula for the maximum available wind power for the moving vehicle. Without a good source or maybe an acceptable explaination this is worthless like repeating "The earth is flat.".

The (w-v)³ type equation is not only withput a good source, but in addition also proven wrong (see above).
 
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Offline Domagoj T

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You can be offended if you want but you do not even deserve an answer as it will be a long and involved one from me and you will have no clue of what I just said.

Don't worry about my feelings, I'm a big boy, I can handle it. Will I'll have no clue what you would have said because you think I have reduced mental capability or because you just can't provide an argument?
You keep saying that at wind speed a sail has no power, yet when I give you an example of sail traveling below wind speed, you deflect and avoid.

My answer was generic and included all possible vehicle types powered only by wind directly down wind and no vehicle can exceed wind speed unless it uses an energy storage device or an external energy source.
So let's focus not on generic, but on this specific example.
And yes, this vehicle does have an external energy source - the wind.
 

Offline Brumby

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You skipped over the question.

I asked about the interaction between this thrust and the surrounding air.

There is nothing skipped.
Yes, there was.... but let me pick up from your next statement:

Quote
Propeller will create a pressure differential thus energy is being stored.

Other people call it thrust - and you call it a pressure differential - but the question is on the energy storage.

Rather than running around with words - where we all seem to get nowhere - it would make life so much easier if you could provide the formula which tells us how much energy is stored.
 

Offline Labrat101

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I gave the formula for the thrust and kinetic power of a propeller. 
But he ignored it completely.
 
« Last Edit: December 30, 2021, 12:19:51 pm by Labrat101 »
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Online CatalinaWOW

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Friends, I found this thread by accident. There appears to be no consensus. 54 pages is beyond my strength, but I saw the film. This is incredible! New horizons are before us!

Certainly there is consensus. A set of equations describing how to design such a vehicle has been put together using established principles of physics, and accepted as correct by qualified professors of engineering. Both full size and scale models have been constructed and shown to work.

This was first done as long ago as 1969. Reference here: https://projects.m-qp-m.us/donkeypuss/wp-content/uploads/2009/06/Bauer-Faster-Than-The-Wind-The-Ancient-Interface.pdf

Thanks for the paper.  A clear and coherent description of why it works. 

Most importantly a set of equations that properly represents all elements of the system.
 
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Offline electrodacus

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When going at a very low speed, that is low RPM on the pedeal on will not be able to get 300 W. The driver has the same problem as the vehicle: it is hard to get the same power, as the forces have to go up.
The problem why going 1 km/h again a 40 km/h head wind with a normal bicyle is not possible is not because the 300 W are needed, but because it is hard to produce even 30 W at such a low speed, as this needs very high force.
The is just not enough force to produce 100 W at a very low speed. So if the magic (..)³ expression would be true one would never be able to start from a stand still aginst any headwind. One allways starts with infinitesimal low speed and thus infintesimal small (essentially zero) mechanical power.

There is no need to repeat the supposed formula for the maximum available wind power for the moving vehicle. Without a good source or maybe an acceptable explaination this is worthless like repeating "The earth is flat.".

The (w-v)³ type equation is not only withput a good source, but in addition also proven wrong (see above).

Why can you put 300W and go at low speed when climbing a hill ?
Why do you think driving in head wind is any different in that regard?
The bicycle speed will be low but your gear ration can be set so that your legs move very fast thus even with low force needed at the pedals you can still produce 300W
There is a limit based on when the traction wheel will start to slip but 300W even at 1km/h is possible on a bicycle.
You do not start with an infinitesimal small amount of power you just have this wrong.
Have you not seen the (w-v)3 in enough places ? It is basically everywhere.
But more important that that the equation works and produces the correct results as seen in any real test.

Offline PlainName

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Quote
But more important that that the equation works and produces the correct results as seen in any real test.

It doesn't, simple as that.
 

Offline electrodacus

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Don't worry about my feelings, I'm a big boy, I can handle it. Will I'll have no clue what you would have said because you think I have reduced mental capability or because you just can't provide an argument?
You keep saying that at wind speed a sail has no power, yet when I give you an example of sail traveling below wind speed, you deflect and avoid.


So let's focus not on generic, but on this specific example.
And yes, this vehicle does have an external energy source - the wind.

I do think people mental capabilities are very different.
There is no wind power available to a sail vehicle traveling at wind speed. There is of course plenty of power available to a sail traveling below wind speed. The slower it travels relative to wind speed the higher the available wind power.
It is clearly seen form the equation that I constantly post here.

Pw = 0.5 * air density * area * (wind speed - vehicle speed)3

I even provided examples. Maybe you got here more recently and did not see them but here is one example just for you

area 1m2
air density 1.2kg/m3
Wind speed 20m/s
Vehicle speed:
a)0m/s
b)5m/s
c)10m/s
d)15m/s
e)20m/s
Wind power available to vehicle
a)4800W
b)2025W
c)600W
d)75W
e)0W

 

Offline fourfathom

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It is clearly seen form the equation that I constantly post here.

Unfortunately, regardless of your claims your equation does not apply to the Blackbird-type vehicles, where there is a propeller connected to wheels rolling on the ground.
We'll search out every place a sick, twisted, solitary misfit might run to! -- I'll start with Radio Shack.
 

Offline electrodacus

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Other people call it thrust - and you call it a pressure differential - but the question is on the energy storage.

Rather than running around with words - where we all seem to get nowhere - it would make life so much easier if you could provide the formula which tells us how much energy is stored.

If this was a non compressible fluid like water then there will be no pressure differential and no energy storage just thrust.
Simplest analogy that I can think of right now and it is visual enough will be pushing a vehicle with another vehicle having just a solid bar connecting them (non compressible fluid like water) or having a spring between them (compressible fluid like air).
The spring is an energy storage device and it is moving together with the pushed vehicle. As any analogy it has limitations but a compressible fluid can be used to store energy and a propeller can be used to increase the pressure differential thus energy can be stored.

This may be hard for some to understand as most will think that there is no way to maintain this pressure differential and there is not much I can do about this.
The main point I want to make since this is ester to understand (at least is what I was thinking) is that there is no wind power available to a direct down wind traveling at or above wind speed.
I provided the correct equation and anyone that is not agreeing with that equation is welcome to provide the correct one.
Nobody can claim to understand a wind powered only vehicle without being able to provide an equation describing the amount of wind power available to vehicle. 

Offline electrodacus

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Unfortunately, regardless of your claims your equation does not apply to the Blackbird-type vehicles, where there is a propeller connected to wheels rolling on the ground.

It applies to any wind powered vehicle and if you disagree post the one that you think applies to blackbird.
The energy storage is a separate equation and it is not relevant since I claim energy storage is involved and you claim that vehicle needs no energy storage and it is powered directly by wind power.
I showed the correct wind power equation (ideal case) and it shows that at wind speed there is zero power available to any wind powered vehicle.

Offline fourfathom

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Other people call it thrust - and you call it a pressure differential

No, he is considering the spinning propeller as effectively being a static sail, and somehow pressure-differential is being "stored" behind it while the vehicle is moving below windspeed.  This is not the same thing as thrust.  (I don't think it's a thing at all.)
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Online IanB

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Have you not seen the (w-v)3 in enough places ? It is basically everywhere.

If it occurs basically everywhere, can you point to one credible reference other than yourself that contains that equation?

As I recall, we have not seen any references yet. When you went to find one in Wikipedia and it wasn't there, you decided Wikipedia was wrong.
 


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