Author Topic: Mess with your minds: A wind powered craft going faster than a tail wind speed.  (Read 147587 times)

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Offline Alex Eisenhut

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One thing's for sure, if we could harness the energy/force/power of this thread, that craft would still be accelerating now..
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Offline electrodacus

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We are going in circles.

As I mentioned the big misconception for you is to think that a treadmill is the same thing with a dragged piece of paper and that is not the case.
Until that is proven it will be useless to continue the discussion.

In the airplane example there are two energy sources plane and human and on top of that travel is done in a single medium. There is no analogy to be made there.

Yes in my diagram there is only one source of power and that is the treadmill witch is also stationary compared to ground unlike the dragged paper.
In ideal vehicle as long as you do not take any power from the treadmill trough the generator wheel the vehicle will not move then if you take power from the generator wheel and put all that in to motor wheel the vehicle will also not move.
Since in real world you can not put all the generated power from generator wheel in to Motor wheel the vehicle will be moved from right to left by the treadmill.

Think about in 3 different steps
a) Treadmill only rotationg at 4m/s
b) Treadmill rotating at 2m/s and also pushed at 2m/s
c) Treadmill not rotating and pushed at 4m/s

You think there will be no difference between the 3 cases ?
In case b) can instead of pushing the treadmill form right to left at 2m/s push the table form left to right at 2m/s. Will that not be the same thing ?

Offline Alex Eisenhut

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Put a stationary bowling ball on a OFF treadmill belt. Put another stationary bowling ball on a stationary rug.

With me so far? Do you need a diagram?
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Offline electrodacus

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Put a stationary bowling ball on a OFF treadmill belt. Put another stationary bowling ball on a stationary rug.

With me so far? Do you need a diagram?

See what I just posted a few seconds before you.
We are talking about a vehicle between two different mediums not a vehicle on a single medium.

Offline IanB

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As I mentioned the big misconception for you is to think that a treadmill is the same thing with a dragged piece of paper and that is not the case.

The top of the treadmill is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.
The piece of paper        is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.

Explain where is the difference between these two cases?
 

Offline Alex Eisenhut

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OK here we go.

Would you agree that the Canadian Shield is a sufficiently large and massive surface to consider as "stationary" for our purposes?
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Offline electrodacus

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The top of the treadmill is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.
The piece of paper        is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.

Explain where is the difference between these two cases?

Have you even read my entire post ? That post already explains what happens.

In this vehicle diagram the treadmill is the road and the ground/table is the wind.
We considering that wind speed and vehicle speed are the same thus they are both stationary at the start of the experiment.
Can you not see the problem when you have the treadmill running at 2m/s and it is also pushed at 2m/s that case b)
If you where to move the ground/table representing the wind from left to right at 2m/s it will be the same thing but maybe now is more visible for you why treadmill is different from dragged paper.
Case a) and case c) are not at all the same and quite the opposite.
You can imagine keeping the paper fixed and moving the table from left to right then it may be more visible for you.

Offline Alex Eisenhut

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Can you not see the problem when you have the treadmill running at 2m/s and it is also pushed at 2m/s that case b)


Wait... you think the entire treadmill moves too? Maybe English isn't your native language, please be more precise.

What is being "also" pushed here?

Do you understand that the treadmill doesn't move? Like in a gym? It's only the belt? The belt is the black thing that people stand on.
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Offline electrodacus

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Wait... you think the entire treadmill moves too? Maybe English isn't your native language, please be more precise.

What is being "also" pushed here?

Do you understand that the treadmill doesn't move? Like in a gym? It's only the belt? The belt is the black thing that people stand on.

Yes what your paper represent is case c) a powered off treadmill pushed relative to the ground.
The case b) is my way to show an intermediary state so that you get the fact that a treadmill is not at all the same as a pushed paper.
I understand that treadmill doesn't move you are the ones that does not understand that.

Offline IanB

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The top of the treadmill is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.
The piece of paper        is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.

Explain where is the difference between these two cases?

Have you even read my entire post ? That post already explains what happens.

No. Do not go off on a tangent. Do not start introducing other topics.

Compare my two sentences. Explain what is the difference between those two scenarios?
 

Offline electrodacus

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No. Do not go off on a tangent. Do not start introducing other topics.

Compare my two sentences. Explain what is the difference between those two scenarios?

Please the the case b) intermediary state to understand that there is a big difference between a treadmill that is not moving relative to the ground and a powered off treadmill moved relative to the ground (powered off treadmill is your piece of paper or moving flat surface).
I think case b) is a good way to explain/visualize the difference between a) treadmill  and c) piece of paper

Offline Labrat101

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Hi , Really interesting and cool,
Yes this is totally possible ,and should work .
as the subject says Mess with your mind . there are 4 forces all working together here  . Plus the fan is not just a propeller .
This experiment just would not work on a tread mill as in real life they ran it on a very large flat open surface without opticals .
The bit were the fan started wobbling but as the wind increased it stop .. this is caused by fan tip speeds and centrifugal force which in turn stabilizes
the craft and the tip air flow will be faster than wind speed . So when all the forces balance it will travel faster .
These guys really went to the next level .
 :popcorn:

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Offline electrodacus

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Hi , Really interesting and cool,
Yes this is totally possible ,and should work .
as the subject says Mess with your mind . there are 4 forces all working together here  . Plus the fan is not just a propeller .
This experiment just would not work on a tread mill as in real life they ran it on a very large flat open surface without opticals .
The bit were the fan started wobbling but as the wind increased it stop .. this is caused by fan tip speeds and centrifugal force which in turn stabilizes
the craft and the tip air flow will be faster than wind speed . So when all the forces balance it will travel faster .
These guys really went to the next level .
 :popcorn:

Yes it seems it messes with many peoples mind.
What do you mean by the fan is not just a propeller ?
The experiment worked perfectly fine on a treadmill see the propeller based cart showing as moving forward on a treadmill.

Online Kleinstein

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No. Do not go off on a tangent. Do not start introducing other topics.

Compare my two sentences. Explain what is the difference between those two scenarios?

Please the the case b) intermediary state to understand that there is a big difference between a treadmill that is not moving relative to the ground and a powered off treadmill moved relative to the ground (powered off treadmill is your piece of paper or moving flat surface).
I think case b) is a good way to explain/visualize the difference between a) treadmill  and c) piece of paper
Ok you introduce the case with the powerd of an pushed treadmil as a 3rd scenario. If it help you to make clear were the diffence is Ok.
However I still don't see, if the powered off and manually pushed treadmill is more like the running treadmill, or more like the piece of paper pulled across the floor.

The next question is, how does the vehicle know which of the 2 (or 3) cases is present and which way to go ? So there should be a difference to the vehicle, not just to your mind.
 

Offline Labrat101

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Hi , Really interesting and cool,
Yes this is totally possible ,and should work .
as the subject says Mess with your mind . there are 4 forces all working together here  . Plus the fan is not just a propeller .
This experiment just would not work on a tread mill as in real life they ran it on a very large flat open surface without opticals .
The bit were the fan started wobbling but as the wind increased it stop .. this is caused by fan tip speeds and centrifugal force which in turn stabilizes
the craft and the tip air flow will be faster than wind speed . So when all the forces balance it will travel faster .
These guys really went to the next level .
 :popcorn:

Yes it seems it messes with many peoples mind.
What do you mean by the fan is not just a propeller ?
The experiment worked perfectly fine on a treadmill see the propeller based cart showing as moving forward on a treadmill.
The Fan is not just a Propeller as it has several functions in this type of setup . I was sorry that they did not use a smoker to show how the air was moving.
the wind is turning the fan . that is connected to the drive wheels . that energy move it forward . the fan/Propeller starts to spin faster . The tips of the propeller
are now creating a rotating vortex . Screw effect . so the air to the side of the vortex will move outwards >  So the when equilibrium is reached the front
should have a lower air pressure . less resistance (vacuum)  the propeller is now blowing the craft .  Yes there is ground resistance but it gets faster the
propeller will try to tilt back and will stay . More like a gyroscope would Ballance.
I see how this works but find it hard to explain exactly why .

Quote
The experiment worked perfectly fine on a treadmill see the propeller based cart showing as moving forward on a treadmill.
Yes I saw that experiment with a small model and a good wind source  but it needs the distance to get all forces balanced very hard .


Update whats with the treadmill . this is thinking back 100years when people thought if a Car went faster than 7mph you would get sucked out
« Last Edit: September 02, 2021, 07:07:34 pm by Labrat101 »
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Offline electrodacus

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Ok you introduce the case with the powerd of an pushed treadmil as a 3rd scenario. If it help you to make clear were the diffence is Ok.
However I still don't see, if the powered off and manually pushed treadmill is more like the running treadmill, or more like the piece of paper pulled across the floor.

The next question is, how does the vehicle know which of the 2 (or 3) cases is present and which way to go ? So there should be a difference to the vehicle, not just to your mind.

Powered off and pushed treadmill is exactly like the piece of paper.
The difference is in changing the reference frames without considering you did that.
That is why case b is a perfect intermediary example.
As you can see case b) as a treadmill rotating at 2m/s and the ground moving in opposite direction at 2m/s
Ground was considered the wind speed in my diagram and was not moving so vehicle and wind had the same speed.
While pushing the treadmill from right to left at 2m/s or pushing the ground from left to right means the same thing
But then if you do that push the ground from left to right it clearly shows a 2m/s wind speed.

So a) where a rotating treadmill is used the analog is a vehicle traveling at 4m/s with wind speed of 4m/s in the same direction
and c) will be the analog of vehicle traveling in the opposite to wind direction at lower speed than the wind. So as different as it can be.

Offline electrodacus

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The Fan is not just a Propeller as it has several functions in this type of setup . I was sorry that they did not use a smoker to show how the air was moving.
the wind is turning the fan . that is connected to the drive wheels . that energy move it forward . the fan/Propeller starts to spin faster . The tips of the propeller
are now creating a rotating vortex . Screw effect . so the air to the side of the vortex will move outwards >  So the when equilibrium is reached the front
should have a lower air pressure . less resistance (vacuum)  the propeller is now blowing the craft .  Yes there is ground resistance but it gets faster the
propeller will try to tilt back and will stay . More like a gyroscope would Ballance.
I see how this works but find it hard to explain exactly why .

You describe what happens before vehicle exceeds wind speed.
What do you think will power the vehicle after the wind speed is exceeded ? As wind can no longer power the vehicle that travels in the exact same direction?

Offline IanB

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Please the the case b) intermediary state to understand that there is a big difference between a treadmill that is not moving relative to the ground and a powered off treadmill moved relative to the ground (powered off treadmill is your piece of paper or moving flat surface).
I think case b) is a good way to explain/visualize the difference between a) treadmill  and c) piece of paper

a treadmill that is not moving relative to the ground
- is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.
a powered off treadmill moved relative to the ground     
- is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.

There is no difference between these two cases.
 

Online Kleinstein

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Hi , Really interesting and cool,
Yes this is totally possible ,and should work .
as the subject says Mess with your mind . there are 4 forces all working together here  . Plus the fan is not just a propeller .
This experiment just would not work on a tread mill as in real life they ran it on a very large flat open surface without opticals .
The bit were the fan started wobbling but as the wind increased it stop .. this is caused by fan tip speeds and centrifugal force which in turn stabilizes
the craft and the tip air flow will be faster than wind speed . So when all the forces balance it will travel faster .
These guys really went to the next level .
 :popcorn:

Yes it seems it messes with many peoples mind.
What do you mean by the fan is not just a propeller ?
The experiment worked perfectly fine on a treadmill see the propeller based cart showing as moving forward on a treadmill.
The Fan is not just a Propeller as it has several functions in this type of setup . I was sorry that they did not use a smoker to show how the air was moving.
the wind is turning the fan . that is connected to the drive wheels . that energy move it forward . the fan/Propeller starts to spin faster . The tips of the propeller
are now creating a rotating vortex . Screw effect . so the air to the side of the vortex will move outwards >  So the when equilibrium is reached the front
should have a lower air pressure . less resistance (vacuum)  the propeller is now blowing the craft .  Yes there is ground resistance but it gets faster the
propeller will try to tilt back and will stay . More like a gyroscope would Ballance.
I see how this works but find it hard to explain exactly why .

Quote
The experiment worked perfectly fine on a treadmill see the propeller based cart showing as moving forward on a treadmill.
Yes I saw that experiment with a small model and a good wind source  but it needs the distance to get all forces balanced very hard .


Update whats with the treadmill . this is thinking back 100years when people thought if a Car went faster than 7mph you would get sucked out

I totally agree that they should use something like smoke or a small thread on a pole to indicate air movement for the experiment on the treadmill.
This would show that when at the speed of the wind (e.g. whicle stand still on the picture) the prop is pushing the air against the direction of the belt of the treadmill.  So the wheels are powering the prop, and not the other way around. This is the main point for the understanding.

There is no need to include complications like a vortex around the prop, just consider the prop as a way to drive the vehicle relative to the air and generate thrust. To make the vehicle go forward the porp has to generate a little more forward force than the wheels generate backward force when they generate the power for the fan.  The technical difficulty is getting the fan to produce enough thrust with the given power. So while the principle is simple, getting the prop at the right speed and pitch is not so much.

....
What do you think will power the vehicle after the wind speed is exceeded ? As wind can no longer power the vehicle that travels in the exact same direction?

The wind can not longer power the prop, when the vehicle goes faster than the wind. However the wind can still power the vehicle. This is the special effect shown here.

When looking  in the reference frame of the vehicle (or wind when at the same speed), the prop takes energy from the wheels and blows air forward against the wind.
When looking  in the reference frame of the ground, the prop takes energy from the wheels and as it produces thrust (asignst the wind) it also absorbes power from the wind. If designed well the power absorbed from the wind can be larger than the power needed to drive the fan.
 

Offline Labrat101

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The Fan is not just a Propeller as it has several functions in this type of setup . I was sorry that they did not use a smoker to show how the air was moving.
the wind is turning the fan . that is connected to the drive wheels . that energy move it forward . the fan/Propeller starts to spin faster . The tips of the propeller
are now creating a rotating vortex . Screw effect . so the air to the side of the vortex will move outwards >  So the when equilibrium is reached the front
should have a lower air pressure . less resistance (vacuum)  the propeller is now blowing the craft .  Yes there is ground resistance but it gets faster the
propeller will try to tilt back and will stay . More like a gyroscope would Ballance.
I see how this works but find it hard to explain exactly why .

You describe what happens before vehicle exceeds wind speed.
What do you think will power the vehicle after the wind speed is exceeded ? As wind can no longer power the vehicle that travels in the exact same direction?
As said I find it hard to explain exactly how this happens.
Can I give you another example .  A torpedo travelling though water (sea) with currents in any direction .
As travels it is spinning and creates a tubercular vortex around it so the out casing is no longer in contact with the water .
The new Torpedo's  can have almost zero surface resistance losses
Just like when you pull the plug out the bath you get that lovely vortex whirlpool that if your are careful one put ones finger in the middle without getting wet .
The propeller also blows
The same thing happens with air it just harder to see
Did that help !!

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Offline electrodacus

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a treadmill that is not moving relative to the ground
- is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.
a powered off treadmill moved relative to the ground     
- is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.

There is no difference between these two cases.

I think your confusion comes from the shape of the treadmill. If that treadmill was just a rotating wheel with central axis not moving relative to the ground you will have seen things differently. Maybe think about the treadmill like a track (like you see on tanks or some construction equipment).
Look at the center of the treadmill or axis of one of the two cylinders and see if they move relative to the ground.
Then power off the treadmill and push it relative to the ground now the center of the treadmill or center of the cylinders move relative to the ground.

There is a very big difference between the two cases and key in understanding what will happen in my diagram and why vehicle will not be able to move from left to right if you use a treadmill. 

Offline electrodacus

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As said I find it hard to explain exactly how this happens.
Can I give you another example .  A torpedo travelling though water (sea) with currents in any direction .
As travels it is spinning and creates a tubercular vortex around it so the out casing is no longer in contact with the water .
The new Torpedo's  can have almost zero surface resistance losses
Just like when you pull the plug out the bath you get that lovely vortex whirlpool that if your are careful one put ones finger in the middle without getting wet .
The propeller also blows
The same thing happens with air it just harder to see
Did that help !!

Sorry not sure how your torpedo example has anything to do with the wind powered vehicle.
First the torpedo travels only in a single medium (water).

If you want a proper example then think about a vehicle driving on wheels at the bottom of a river so the water flow will represent the wind in air and the bottom of the river the road.
Now in this case since air is replaced with water the vehicle will be unable to exceed the water flow speed. The reason that is not possible is because water is a non compressible fluid and so energy can not be stored thus vehicle can not exceed water flow speed.
In air vehicle can exceed wind speed but only for a limited amount of time dictated by the amount of stored energy and vehicle losses.

Offline Labrat101

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There is a low level vacuum on one side so lower than ambient pressure and on the other side there is a higher than ambient pressure.
As I mentioned before Wikipedia is not always a source of reliable information but it is sure way better for this than the youtube video performed by someone with no knowledge about the subject.
Link to articlehttps://en.wikipedia.org/wiki/Axial_fan_design
And diagram I posted before showing clearly the pressure differential

[/quote]
Totally correct   It would help others if maybe some could do a 3D model   :-+ :popcorn:
« Last Edit: September 02, 2021, 07:59:22 pm by Labrat101 »
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Online iMo

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Imaging a small zeppelin (an airship) with the same propeller as it is in the Blackbird configuration. The zeppelin will fly, say, 5m high above the ground.
Will the zeppelin fly faster then the tail wind speed?
 
« Last Edit: September 02, 2021, 08:01:07 pm by imo »
Readers discretion is advised..
 

Offline IanB

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a treadmill that is not moving relative to the ground
- is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.
a powered off treadmill moved relative to the ground     
- is a flat surface moving from right to left under the front wheels of the cart, relative to a stationary surface on which the back wheels rest.

This is really simple. If you think there is something wrong with one of these two statements, change some of the green words to make it correct.
 


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