Author Topic: Mess with your minds: A wind powered craft going faster than a tail wind speed.  (Read 147178 times)

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Offline electrodacus

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The calculation this way is absolutely not easy, as there is no accepted formula for the maximum power available to a vehicle. So the difficulty is  in deriving (not just propose a solution and claim it must but ture as an act of god). As there are multiple possible ways to harness the wind power this is a really difficult task. To make it a proof it needs a really good explaination that most people would agree with.


There is an accepted formula is the one that I posted and that is the ideal case (best case if you want) of available wind power to any vehicle you can imagine.
You can see in the formula what influences the available wind power and that is wind speed relative to vehicle and area that wind/air has to interact with.
That is all it can not be any simpler than that.


Just presenting an expression that most people think is wrong is far from supporting the claim. It is more like showing poor understanding of logic and science in general.

The V_w * F_w form was never claimed to be the available wind power, but the power needed by the vehicle. Just like for another force to push against the power is force times speed (by definition and not by mistake). Thinking the power would stay constant, essentially independent of the speed is just a rediculous idea, that causes obvious contradictions.  One such contraticion would be that the power when going in the same direction as the wind would be the same as the maximum avialable power and thus all wind genrator would be 100% efficient. I don't think that sounds plausible.

What are you even talking about ? When have I ever said that wind power available to vehicle is not dependent on speed (it is clearly show in the equation).
I even provided an example yesterday showing highest wind power available is when vehicle is just starting to move super low by the time it gets to half the wind speed and zero when vehicle speed equals wind speed.

Online Kleinstein

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The calculation this way is absolutely not easy, as there is no accepted formula for the maximum power available to a vehicle. So the difficulty is  in deriving (not just propose a solution and claim it must but ture as an act of god). As there are multiple possible ways to harness the wind power this is a really difficult task. To make it a proof it needs a really good explaination that most people would agree with.


There is an accepted formula is the one that I posted and that is the ideal case (best case if you want) of available wind power to any vehicle you can imagine.
You can see in the formula what influences the available wind power and that is wind speed relative to vehicle and area that wind/air has to interact with.
That is all it can not be any simpler than that.


Just presenting an expression that most people think is wrong is far from supporting the claim. It is more like showing poor understanding of logic and science in general.

The V_w * F_w form was never claimed to be the available wind power, but the power needed by the vehicle. Just like for another force to push against the power is force times speed (by definition and not by mistake). Thinking the power would stay constant, essentially independent of the speed is just a rediculous idea, that causes obvious contradictions.  One such contraticion would be that the power when going in the same direction as the wind would be the same as the maximum avialable power and thus all wind genrator would be 100% efficient. I don't think that sounds plausible.

What are you even talking about ? When have I ever said that wind power available to vehicle is not dependent on speed (it is clearly show in the equation).
I even provided an example yesterday showing highest wind power available is when vehicle is just starting to move super low by the time it gets to half the wind speed and zero when vehicle speed equals wind speed.
The formula presented is not an accepted formula for the available wind power for the moving vehicle - it is not even correct. If it would be show us a reliable source ! If you can't , just give up on repeating that formula.

The point of essentially independet of velocity was for the low velocity case (e.g. vehicle much slower than the wind). Sorry forgot about hat detail.
The slower one goes the more rediculous your claim gets.
 

Online IanB

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The easiest part will be to show that directly down wind faster than wind is not possible without some sort of energy storage device or an external energy source.
That can be proved with the correct equation for wind power available to any wind powered vehicle

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

It is irrelevant how vehicle is build as long as wind power is the only source then the above is the correct formula for an ideal system (so absolutely best case scenario).

It's a very circular argument:

"Why can no vehicle go downwind faster than the wind speed? Because this correct formula says so."

"Why is this formula correct? Because no vehicle can go downwind faster than the wind speed."

Each conclusion depends on the other.
 

Offline electrodacus

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The formula presented is not an accepted formula for the available wind power for the moving vehicle - it is not even correct. If it would be show us a reliable source ! If you can't , just give up on repeating that formula.

The point of essentially independet of velocity was for the low velocity case (e.g. vehicle much slower than the wind). Sorry forgot about hat detail.
The slower one goes the more rediculous your claim gets.

I do not need to provide you with any source. That formula works in all real world applications.
If you disagree with the one I provided just provide the one you think is the correct and we can test that.

Offline electrodacus

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It's a very circular argument:

"Why can no vehicle go downwind faster than the wind speed? Because this correct formula says so."

"Why is this formula correct? Because no vehicle can go downwind faster than the wind speed."

Each conclusion depends on the other.

Provide an equation that you think is the correct one for a wind powered vehicle.
The one I provided is valid for any case and it perfectly predicts what happens in reality.
Even the incorrect formula used by many predicts no wind power available above wind speed so that is not an argument either.

Online Kleinstein

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It's a very circular argument:

"Why can no vehicle go downwind faster than the wind speed? Because this correct formula says so."

"Why is this formula correct? Because no vehicle can go downwind faster than the wind speed."

Each conclusion depends on the other.

Provide an equation that you think is the correct one for a wind powered vehicle.
The one I provided is valid for any case and it perfectly predicts what happens in reality.
Even the incorrect formula used by many predicts no wind power available above wind speed so that is not an argument either.
I don't think there is an generally accepted ready made formula for the maximum available wind power for the moving vehicle. At least I don't know one.
It is not up to us to provide a formula for a rather tricky problem. Chances are you would not understand or accept it anyway. It is your turn to show a good source, ideally with a good explaination.

The formula with the (w-v)²*v is the power available to a simple sail for velocities lower than the speed of the wind. However this does not have much relevance to a vehicle driven by a prop. It shows that going faster than the wind does not work with a simple (e.g. spinnacker like) sail, when going straight down the wind.
This is not really surprising and know for a long time.
 

Offline electrodacus

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I don't think there is an generally accepted ready made formula for the maximum available wind power for the moving vehicle. At least I don't know one.
It is not up to us to provide a formula for a rather tricky problem. Chances are you would not understand or accept it anyway. It is your turn to show a good source, ideally with a good explaination.

It will be ridiculous if there was none but I mentioned many times. Problem is not that tricky if you know that equation

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

The formula with the (w-v)²*v is the power available to a simple sail for velocities lower than the speed of the wind. However this does not have much relevance to a vehicle driven by a prop. It shows that going faster than the wind does not work with a simple (e.g. spinnacker like) sail, when going straight down the wind.
This is not really surprising and know for a long time.

Blackbird is not driven by the propeller it is driven by wind power that pushes against the equivalent back area of the vehicle and it is also pushed by the pressure differential.
So what energy you take from the wheel is provided by the combination of wind + stored energy in pressure differential that basically push the vehicle same as any sail vehicle as that is the only way air can interact with the vehicle. Above wind speed is the stored pressure differential alone that "pushes"/powers the vehicle.
When that stored energy is all used up the vehicle will just slow down (decelerate).

Offline PlainName

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it is driven by wind power that pushes against the equivalent back area of the vehicle

So close! It's pushing against the rearward-moving airflow from the propeller, not any part of the vehicle (which would be receding forwards).
 

Offline electrodacus

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it is driven by wind power that pushes against the equivalent back area of the vehicle

So close! It's pushing against the rearward-moving airflow from the propeller, not any part of the vehicle (which would be receding forwards).

Yes as the vehicle speed increases the equivalent area of the propeller increases up to the max swept area of the propeller.
Still air density and of course pressure is increased at the back of the propeller and decreased on the front and this pressure differential stored energy is powered by wind power.
But while vehicle is above wind speed there is no more wind power available so the pressure differential that now pushes the vehicle will start to drop reducing the acceleration rate up to the point pressure differential is small enough that can no longer cover the vehicle frictional losses and then the vehicle will start to slow down.

Offline PlainName

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But while vehicle is above wind speed there is no more wind power available

You're falling into your hole again. When the vehicle is at or above wind speed, the airflow from the propeller is still going backwards at slower than wind speed. Thus the wind is still pushing against that airflow and generating power.

The prop doesn't need much power to do that. Just enough to turn it and move the vehicle through almost static air - any drag is from the vehicle going faster than the wind, and we only need it to be tiny to score.
 

Offline electrodacus

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You're falling into your hole again. When the vehicle is at or above wind speed, the airflow from the propeller is still going backwards at slower than wind speed. Thus the wind is still pushing against that airflow and generating power.

The prop doesn't need much power to do that. Just enough to turn it and move the vehicle through almost static air - any drag is from the vehicle going faster than the wind, and we only need it to be tiny to score.

:) No that is not the case.
There is no wind power available as soon as vehicle speed equals wind speed.
There air is compressed and that is what still pushes the vehicle but as it is doing so pressure will drop thus stored energy is used up.

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Offline lordium

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Is it possible to get an summary from start to finish about why it is impossible?
Examples and illustrations along to way would be helpful so that I can follow all the steps.
I'm really struggling to follow the thought process here. Guess I'm not smart enough. So please put it as plainly as possible.

I have made a video but is maybe a bit long and boring

In any case I will try to make a summary.
The easiest part will be to show that directly down wind faster than wind is not possible without some sort of energy storage device or an external energy source.
That can be proved with the correct equation for wind power available to any wind powered vehicle

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

It is irrelevant how vehicle is build as long as wind power is the only source then the above is the correct formula for an ideal system (so absolutely best case scenario).
The air density can be considered a constant so not very relevant and then there are just two other therms the area of the vehicle that in the particular case of blackbird will increase with speed up to a max of swept area of the propeller but while that increase in area helps make more power available to vehicle it will only be valid as long as vehicle speed is smaller than wind speed since as it can be seen in the equation if vehicle speed equals wind speed the wind power will be zero.

This formula is all that is needed in order to demonstrate that any wind powered only vehicle will need an energy storage device in order to exceed wind speed directly down wind.
It seems that many people do not work with power and prefer to work with force and speed separately and this is how a wrong equation ended everywhere.
The equation for force is correct
Fw = 0.5 * air density * area * (wind speed - vehicle speed)2

But then when they want to calculate wind power they just multiply by vehicle speed and leave the wind speed out of the equation.  The most likely reason they do that is because someone made this mistake first and they just copy paste the same wrong equation everywhere without thinking to much or testing to see if it is true.

They just think that if vehicle speed is zero the wind power available to that vehicle is zero and they think that since they imagine zero speed as a vehicle with brakes engaged.  That seems as a super silly mistake to make is like saying that a sail boat has zero wind power available when boat speed is zero because the boat is anchored to the ground.

Let me know if you agree with the above and then I can continue with how the Blackbird can actually exceed wind speed for a limited amount of time using energy storage in pressure differential created by the propeller with part of the wind power.

Ah ok. So the only thing relevant to the vehicle speed is the air pushing it (assuming everything else ideal). The part that is confusing me is the spinning propeller. I know from experience that those do push or pull air depending on orientation when spinning. And spinning this does since it is driven by the wheels (which are also spinning), So shouldn't this factor into the problem in some way? And sorry I don't have access to youtube here.
 

Offline thm_w

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Hey guys, isn't it absurd to think that one could move into 500km/h winds with only 1W of power at a speed of 0.000001km/h? That is clearly WRONG. The equation is WRONG.
Here is a video of 500km/h winds destroying a car to prove my point.

:palm:

Its like you haven't heard of gear reduction or understand that taking equations to their limit makes the numbers seem "wrong" (as pointed out already).
A racing bike shown is not capable of riding at 1km/h at cadence, the gear ratio simply does not allow it.
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Offline electrodacus

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Is it possible to get an summary from start to finish about why it is impossible?
Examples and illustrations along to way would be helpful so that I can follow all the steps.
I'm really struggling to follow the thought process here. Guess I'm not smart enough. So please put it as plainly as possible.

In any case I will try to make a summary.
The easiest part will be to show that directly down wind faster than wind is not possible without some sort of energy storage device or an external energy source.
That can be proved with the correct equation for wind power available to any wind powered vehicle

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

It is irrelevant how vehicle is build as long as wind power is the only source then the above is the correct formula for an ideal system (so absolutely best case scenario).
The air density can be considered a constant so not very relevant and then there are just two other therms the area of the vehicle that in the particular case of blackbird will increase with speed up to a max of swept area of the propeller but while that increase in area helps make more power available to vehicle it will only be valid as long as vehicle speed is smaller than wind speed since as it can be seen in the equation if vehicle speed equals wind speed the wind power will be zero.

This formula is all that is needed in order to demonstrate that any wind powered only vehicle will need an energy storage device in order to exceed wind speed directly down wind.
It seems that many people do not work with power and prefer to work with force and speed separately and this is how a wrong equation ended everywhere.
The equation for force is correct
Fw = 0.5 * air density * area * (wind speed - vehicle speed)2

But then when they want to calculate wind power they just multiply by vehicle speed and leave the wind speed out of the equation.  The most likely reason they do that is because someone made this mistake first and they just copy paste the same wrong equation everywhere without thinking to much or testing to see if it is true.

They just think that if vehicle speed is zero the wind power available to that vehicle is zero and they think that since they imagine zero speed as a vehicle with brakes engaged.  That seems as a super silly mistake to make is like saying that a sail boat has zero wind power available when boat speed is zero because the boat is anchored to the ground.

Let me know if you agree with the above and then I can continue with how the Blackbird can actually exceed wind speed for a limited amount of time using energy storage in pressure differential created by the propeller with part of the wind power.

Ah ok. So the only thing relevant to the vehicle speed is the air pushing it (assuming everything else ideal). The part that is confusing me is the spinning propeller. I know from experience that those do push or pull air depending on orientation when spinning. And spinning this does since it is driven by the wheels (which are also spinning), So shouldn't this factor into the problem in some way? And sorry I don't have access to youtube here.

The propeller is a wheel for traveling trough a medium instead of traveling on top surface of a medium like a regular wheel.
Propeller is powered by wind and or pressure differential depending on vehicle speed.
Since output power of the propeller is lower than input power from the wheel there could not be any net gain.
The role of the propeller is to compress air creating that pressure differential where energy is stored to allow vehicle to exceed wind speed for a limited amount of time.

Wind power is split between accelerating the vehicle and powering the propeller that in turn creates pressure differential.
Say at some particular moment there are 100W available as wind power and say this is for 1ms
then say 40W is used to accelerate the vehicle so vehicle kinetic energy will increase by 40W * 0.001s = 40mWs thus the vehicle speed has increased a little bit.
The other 60W is taken by the wheel that sends it to propeller that say it is 70% efficient so 60W * 0.7 = 42W are available as propeller output and they end up stored as pressure differential so 42mWs of stored energy.
If this continues in the same way the vehicle will be storing about the same amount of energy in pressure differential as there is stored in vehicle kinetic energy maybe just slightly more.
In ideal case all this stored energy can then end up as vehicle kinetic energy and thus vehicle peak speed can be even multiple times larger than wind speed but from that max speed the vehicle will just start to decelerate as there is nothing more to power it.

Offline electrodacus

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Hey guys, isn't it absurd to think that one could move into 500km/h winds with only 1W of power at a speed of 0.000001km/h? That is clearly WRONG. The equation is WRONG.
Here is a video of 500km/h winds destroying a car to prove my point.

:palm:

Its like you haven't heard of gear reduction or understand that taking equations to their limit makes the numbers seem "wrong" (as pointed out already).
A racing bike shown is not capable of riding at 1km/h at cadence, the gear ratio simply does not allow it.

I think 1km/h on a bike should be possible if you have good enough balance. It is about 30cm per second so 1ft per second.
But yes getting things to extreme is a good way to test if an equation provide correct results.
The correct equation will not provide this insane results for 1km/h bicycle speed.
If all you have is around 300W max power available then my equation correctly predicts that you can drive at 1km/h in head winds of 35km/h
35km/h + 1km/h is 36km/h round number as it is 10m/s
So 0.5 * 1.2 * 0.408 * 103 = 244.8W will say that the rest to 300W is friction and rolling resistance.

So if you have 300W available you can drive at 36km/h or a max headwind of 36km/h so (bicycle speed + wind speed) < 36km/h
Nothing as absurd as 230km/h head wind and can be tested.

Offline thm_w

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I think 1km/h on a bike should be possible if you have good enough balance. It is about 30cm per second so 1ft per second.
But yes getting things to extreme is a good way to test if an equation provide correct results.
The correct equation will not provide this insane results for 1km/h bicycle speed.
If all you have is around 300W max power available then my equation correctly predicts that you can drive at 1km/h in head winds of 35km/h
35km/h + 1km/h is 36km/h round number as it is 10m/s
So 0.5 * 1.2 * 0.408 * 103 = 244.8W will say that the rest to 300W is friction and rolling resistance.

So if you have 300W available you can drive at 36km/h or a max headwind of 36km/h so (bicycle speed + wind speed) < 36km/h
Nothing as absurd as 230km/h head wind and can be tested.

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.

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Offline electrodacus

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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.

I provided this example before but if you want to stay stationary in a river you will need to output significant amount of power to swim against the current and maintain approx zero speed relative to ground.
The lowest energy state is your speed relative to ground being the same speed as the current or air speed.

Online IanB

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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.
Not necessarily. I could just put my feet on the pedals and stop them from turning. No need for brakes.

Quote
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)...
Why do you introduce absurdly irrelevant things into the discussion? It is a tricycle. It does not fall over when stationary.

Quote
...but some arbitrary low speed 1km/h or 2km/h against the head wind will require 300W.
This is against all experimental evidence. For this experiment we have an appropriately low gear ratio. One turn of the pedals moves the bike forwards 30 cm. It will be effortless to move the bike against the headwind. Nothing like 300 W required. Not even breaking a sweat. (Note: 30 cm/s = 1 km/h)

Quote
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.
Again, no experiment shows this. If it were true, the brakes would get hot and start smoking. But they don't.
 

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.
 

Offline electrodacus

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Not necessarily. I could just put my feet on the pedals and stop them from turning. No need for brakes.

It will depend in what gear you are and your weight but if it can not lift you then that is a sort of gravitational brake not that different from friction brake.
It will also an energy storage device since if wind power can lift the pedal up when it will come down it will release all that stored energy so your standing on the pedal will have no real effect.

Why do you introduce absurdly irrelevant things into the discussion? It is a tricycle. It does not fall over when stationary.
I see you did not get my analogy. The analogy was referring to being able to keep the speed at zero like trying to swim in a river against the current and maintain zero speed relative to ground. You may average around zero but it will me more or less that that at any one time.


This is against all experimental evidence. For this experiment we have an appropriately low gear ratio. One turn of the pedals moves the bike forwards 30 cm. It will be effortless to move the bike against the headwind. Nothing like 300 W required. Not even breaking a sweat. (Note: 30 cm/s = 1 km/h)

You did not do this experiment else you will know that it will be about 300W and not sure in what physical shape you are but I'm fairly certain you will be sweating.


Again, no experiment shows this. If it were true, the brakes would get hot and start smoking. But they don't.

Most brakes will handle 300W. I have not see any smoking brakes when going down hill either and there you also need to brake with about the same power level unless you like extreme speed.

Offline electrodacus

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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.

Let me put this in a different way.
You have a high power LED connected to a solar panel. While there is light from the sun the LED is nice and bright then you say I can continue to have light even when there is no longer any sun light reaching the solar panel because the power LED produces light (propeller) and that LED is powered by the solar panel (wheel on the ground).
« Last Edit: December 30, 2021, 04:57:41 am by electrodacus »
 

Offline lordium

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...
...
...

The propeller is a wheel for traveling trough a medium instead of traveling on top surface of a medium like a regular wheel.
Propeller is powered by wind and or pressure differential depending on vehicle speed.
Since output power of the propeller is lower than input power from the wheel there could not be any net gain.
The role of the propeller is to compress air creating that pressure differential where energy is stored to allow vehicle to exceed wind speed for a limited amount of time.

...

I draw a picture to help here...

So there are 2 cases:
A) the fan is NOT spinning (but wheel is, clutch?)
B) fan is being spun from the wheel through some gearbox or similar

so in case A the wind is pushing the vehicle, but then we turn the gearbox on and now the fan is spinning... The wind is still pushing the same, and now the fan also adds some to the vehicle. You say the power needed to turn the fan from the wheel and generate thrust is higher than just having the fan locked and not spinning (like a sail)?
 

Offline electrodacus

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I draw a picture to help here...

So there are 2 cases:
A) the fan is NOT spinning (but wheel is, clutch?)
B) fan is being spun from the wheel through some gearbox or similar

so in case A the wind is pushing the vehicle, but then we turn the gearbox on and now the fan is spinning... The wind is still pushing the same, and now the fan also adds some to the vehicle. You say the power needed to turn the fan from the wheel and generate thrust is higher than just having the fan locked and not spinning (like a sail)?

Do you agree that a propeller is less efficient than a wheel ? Propeller maybe a realistic 70% while a wheel can easily be 95% efficient.
If you agree then why not just take the power from wind pushing the vehicle from the back wheel and outing that in to driving the front wheel ?
Do you see the problem?
The difference is that road is a solid thus not compressible and you can not store any energy.
The only reason the propeller works is because you can store energy by increasing the pressure differential.
If you where to replace the air (compressible fluid) with water (incomprehensible fluid) the it will be the same useless stuff as getting the power from back wheels and putting in to front wheels.
So neither a gear box nor a propeller are magic devices they can only output less power than you put in so the thing that helps here is the air (compressible fluid).

So all you do when you take part of the wind power from the wheel and putting it in to propeller is storing energy.

Offline lordium

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Do you agree that a propeller is less efficient than a wheel ? Propeller maybe a realistic 70% while a wheel can easily be 95% efficient.
If you agree then why not just take the power from wind pushing the vehicle from the back wheel and outing that in to driving the front wheel ?
Do you see the problem?
The difference is that road is a solid thus not compressible and you can not store any energy.
The only reason the propeller works is because you can store energy by increasing the pressure differential.
If you where to replace the air (compressible fluid) with water (incomprehensible fluid) the it will be the same useless stuff as getting the power from back wheels and putting in to front wheels.
So neither a gear box nor a propeller are magic devices they can only output less power than you put in so the thing that helps here is the air (compressible fluid).

So all you do when you take part of the wind power from the wheel and putting it in to propeller is storing energy.

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?
 


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