Author Topic: Mess with your minds: A wind powered craft going faster than a tail wind speed.  (Read 104193 times)

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Online Kleinstein

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If I where to compete with a similar vehicle just using a round 5.3m diameter sail instead of the propeller I will win the race any time against the blackbird.
What will happen is that I will be the first to accelerate while blackbird will waste a lot of time initially to store energy and while blackbird will have higher top speed the average speed will be lower due propeller being less efficient than a sail.
So if the race is about top speed then blackbird can win but if it is about getting first to finish line then sail vehicle will win.
For such a race is depends on the lenght of the race. Initially the backbrid needs additional energy for the kinetik energy of the propeller - that is the main extra energy storrage. So in the acceleration phase to maybe 90% of the wind speed the sail drive may be more efficient, but later the propeller extra pushing action can give it an edge and finally reaching the higher sustained speed (e.g. 120% the wind speed), while the sail may only reach 95%. 

If there is extra energy storred this extra would go up with higher speed. So that extra energy could not be used to accelerate - this would be the wrong way round, like using the gain in potential energy to go up faster up-hill, which obviously does not work. There just is not significant energy storrage that would help to accelerate the vehicle (only to slow down the slow down).
The energy storage is just there to confuse and maybe find an explaination for seeing the experiment but not believing. The idea with energy storrage just does not work.

The example with wheels can be calculated without, with very basic math - not even physics. The movement to the right is the only one compatible with the gear ratio and no slip at the wheeels. Trying to convince us of the opposite as nearly as crazzy as claiming that 3x3 is 7. :horse:
 

Offline electrodacus

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Where is the energy storage in a lever?  Where is it in a gear ratio?  Energy storage is not required here.

Not quite sure what you are asking. In real world same as you can not get rid of friction you can not get rid of energy storage. You can reduce both friction and energy storage but you can not completely eliminate them.
If you are talking about the geared toy cart in my first video then as explained the frame of the vehicle torsion acts as an energy storage device again is like a spring same as with the belt elasticity just less pronounced but if you look closely in the video you will see how the metal pins on the side of the vehicle move up and down as the energy is stored and then used.

Online Kleinstein

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There is some parasitic energy storage, but it is not relevant. It is just too little to explain the experiments shown. The right explaination works without it.
It's just  red hering - and a dead hering.  :horse:
 

Offline electrodacus

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If I where to compete with a similar vehicle just using a round 5.3m diameter sail instead of the propeller I will win the race any time against the blackbird.
What will happen is that I will be the first to accelerate while blackbird will waste a lot of time initially to store energy and while blackbird will have higher top speed the average speed will be lower due propeller being less efficient than a sail.
So if the race is about top speed then blackbird can win but if it is about getting first to finish line then sail vehicle will win.
For such a race is depends on the lenght of the race. Initially the backbrid needs additional energy for the kinetik energy of the propeller - that is the main extra energy storrage. So in the acceleration phase to maybe 90% of the wind speed the sail drive may be more efficient, but later the propeller extra pushing action can give it an edge and finally reaching the higher sustained speed (e.g. 120% the wind speed), while the sail may only reach 95%. 

If there is extra energy storred this extra would go up with higher speed. So that extra energy could not be used to accelerate - this would be the wrong way round, like using the gain in potential energy to go up faster up-hill, which obviously does not work. There just is not significant energy storrage that would help to accelerate the vehicle (only to slow down the slow down).
The energy storage is just there to confuse and maybe find an explaination for seeing the experiment but not believing. The idea with energy storrage just does not work.

The example with wheels can be calculated without, with very basic math - not even physics. The movement to the right is the only one compatible with the gear ratio and no slip at the wheeels. Trying to convince us of the opposite as nearly as crazzy as claiming that 3x3 is 7. :horse:

Yes there is some kinetic energy stored in the propeller but that is much smaller in that initial phase than the energy stored in pressure differential energy storage.
There can not be a sustained speed above wind speed and that I what I try to make people understand.
No matter the length of the race the sail will win the race if wining means being first at finish line. If race is about top speed obviously blackbird will win.

Have you watched my slow motion video https://odysee.com/@dacustemp:8/wheel-cart-energy-storage-slow:8
The energy storage is fairly visible there and you can see vehicle peak speed even above paper speed but average speed is much lower. Same will happen to blackbird if you waited long enough to see multiple cycles then it will look the same as my toy cart.

Offline fourfathom

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I am now halfway through this entire thread, and I apologize to all for beating a thoroughly dead horse.
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Offline electrodacus

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I am now halfway through this entire thread, and I apologize to all for beating a thoroughly dead horse.

The crowd effect is quite a bad thing especially here when the majority is wrong.

Online Kleinstein

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Have you watched my slow motion video https://odysee.com/@dacustemp:8/wheel-cart-energy-storage-slow:8
The energy storage is fairly visible there and you can see vehicle peak speed even above paper speed but average speed is much lower. Same will happen to blackbird if you waited long enough to see multiple cycles then it will look the same as my toy cart.
I watched the video, and when taking the paper as the reference and the ground as the driving system, the average velocitiy is larger - the vehicle moved to the right in the picture after all, so more to the right than the ground has moved.
The movement is a bit jerky, because the paper is not moved at a constant speed. Move the paper at a constant speed and vehicle would also more at a constant speed.

There can not be a sustained speed above wind speed and that I what I try to make people understand.
However this is only a claim and not a valid argument. This claim is also wrong - any most of us here have recognized this and try to explain how it is possible. The videos show it - just believe what you see and don't thing it is the red hering making this happen. It is much simpler.
 

Offline electrodacus

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Have you watched my slow motion video https://odysee.com/@dacustemp:8/wheel-cart-energy-storage-slow:8
The energy storage is fairly visible there and you can see vehicle peak speed even above paper speed but average speed is much lower. Same will happen to blackbird if you waited long enough to see multiple cycles then it will look the same as my toy cart.
I watched the video, and when taking the paper as the reference and the ground as the driving system, the average velocitiy is larger - the vehicle moved to the right in the picture after all, so more to the right than the ground has moved.
The movement is a bit jerky, because the paper is not moved at a constant speed. Move the paper at a constant speed and vehicle would also more at a constant speed.

There can not be a sustained speed above wind speed and that I what I try to make people understand.
However this is only a claim and not a valid argument. This claim is also wrong - any most of us here have recognized this and try to explain how it is possible. The videos show it - just believe what you see and don't thing it is the red hering making this happen. It is much simpler.

The paper is moved at fairly constant speed and it is not the reason for the type of movement. Please look closer at the video as you will see paper always moves at a decently constant speed while vehicle just stops many times.
Not that vehicle needs to stop to demonstrate what I'm saying it can just speed up and slow down as it is the case with the gear version of the vehicle where there was less energy storage so the elastic/springy type of storage is smooth out by the vehicle kinetic energy that will no longer be zero when it starts to move.

If you understand what you see in this video then you will also understand how blackbird works is just that blackbird has so much larger energy storage and lower friction that cycle is hundreds of seconds instead of hundreds of milliseconds.
Look at the front wheel turning while back wheel is stationary. Is clear energy from front wheels is stored in the rubber band since that is stretched.
Then when front wheel starts to slip the stored energy is what is used to push the vehicle forward using the back wheels.
If there was no energy storage the front wheel will never turn without the back wheel also turning and since that can not work the front wheel will just slip in best case so vehicle will not move at all else vehicle will move backwards right to left as in my theoretical example.
In practice is a bit hard to get rid of both friction and energy storage.
Paper moves at least 2x faster from right to left than the vehicle moves from left to right in average but there are peaks where vehicle may move faster than paper in the opposite direction but the average speed is what counts and that is why a sail vehicle will win against a blackbird type vehicle if wining means getting first to finish line.

Offline ejeffrey

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Do you not agree with that fact that all air molecules move in the opposite direction of travel when vehicle is above wind speed traveling in the wind direction?
No, we do not agree.

Please provide details if you do not agree.
My statement is not only very simple but also correct so I wait for you explain how my statement is incorrect

We do not agree that there is an apparent violation of conservation of energy -- because there isn't: the vehicle extracts energy from the velocity difference between the wind and the ground and uses that to make the vehicle go faster.

We don't agree that kinetic energy is a vector.  Because it is not, as taught in every physics class since Newton.   Momentum is a vector, kinetic energy is a scalar.  This is your most fundamental, most wrong misunderstanding of basic physics. See: Kinetic energy is a scalar

We don't agree that "the resultant velocity must be in the direction of the net work" because that is a meaningless statement based on the above two points.

We don't agree that energy storage beyond the kinetic energy of the vehicle is relevant in any of the demonstrations because they are not, and you have not been able to quantify or explain them

We solved the free body diagram to find the net torque and direction of motion of the mechanical analog.  You don't agree that we did math correctly, but you didn't explain why other than your misguided "net work" argument.

And now that you finally agree that a moving piece of paper is equivalent to a treadmill, you have invented a new energy storage theory that also makes no sense.  I did the experiment you said would prove you right or wrong, it proved you wrong, and you don't believe it.  I was sitting right there and I can tell you that the belt was stretching a negligible amount and not storing energy.

Multiple experiments demonstrate that you are incorrect, so yes we disagree.
 

Offline electrodacus

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We do not agree that there is an apparent violation of conservation of energy -- because there isn't: the vehicle extracts energy from the velocity difference between the wind and the ground and uses that to make the vehicle go faster.

We don't agree that kinetic energy is a vector.  Because it is not, as taught in every physics class since Newton.   Momentum is a vector, kinetic energy is a scalar.  This is your most fundamental, most wrong misunderstanding of basic physics. See: Kinetic energy is a scalar

We don't agree that "the resultant velocity must be in the direction of the net work" because that is a meaningless statement based on the above two points.

We don't agree that energy storage beyond the kinetic energy of the vehicle is relevant in any of the demonstrations because they are not, and you have not been able to quantify or explain them

We solved the free body diagram to find the net torque and direction of motion of the mechanical analog.  You don't agree that we did math correctly, but you didn't explain why other than your misguided "net work" argument.

And now that you finally agree that a moving piece of paper is equivalent to a treadmill, you have invented a new energy storage theory that also makes no sense.  I did the experiment you said would prove you right or wrong, it proved you wrong, and you don't believe it.  I was sitting right there and I can tell you that the belt was stretching a negligible amount and not storing energy.

Multiple experiments demonstrate that you are incorrect, so yes we disagree.

Obviously there is no violation of conservation of energy just your explanation if it where to be true (it is not) will violate the conservation of energy.

If you know the vehicle weight and kinetic energy you can find out the speed. Since weight is constant we can agree that a drop in kinetic energy will result in a drop of speed so when I use vehicle kinetic energy I'm using that to demonstrate that speed can not increase.
The wheel only vehicle has mostly kinetic energy stored in vehicle but in case of the propeller version the propeller kinetic energy is significant and needs to be considered.
Using forces only is your main problem as force on the wheel is not the same with force on vehicle when gear ratio is different from 1:1.
I do not invent anything it is super clear from my video that without energy storage the vehicle can not move from left to right. If you do not see that please look closer and try to find anything else that will allow vehicle to move from left to right.

How can you say the belt is not storing energy ?  Negligible amount is your definition but I will say sufficient not negligible.  This is a ultra small ultra light vehicle and in slow down video it is clearly seen how vehicle stop's and starts multiple times (same as back wheel) while front wheel always rotates.
Multiple experiments are interpreted incorrectly. None of the experiments contradict my explanation.

Offline electrodacus

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Please just watch the video again ideally set the video player at 0.25x and watch a few times.
https://odysee.com/@dacustemp:8/wheel-cart-energy-storage-slow:8

It is very clear in video that the back wheel is not rotating at a fixed speed or proportional with the front wheel and gear ratio and actually there are multiple times when the back wheel is not spinning at all while the front wheel is.
It should be very clear that in those moments the belt is extended by the front wheel basically an energy storage device and is also clear that when back wheel moves the energy storage is discharged belt tension drops.
I can not make it much more clear that energy is being stored and then used to advance the vehicle and without that there will be no vehicle moving from left to right.

It seems most of you just want to ignore the energy storage device or call it negligible in therms of storage capacity as that will make it go away.
If there will not have been any energy storage then front wheel will just slip and there will be no movement.  The discharge of that stored energy together with the stick slip hysteresis helps the vehicle move forward (left to right).

Your explanation ignores any storage and stick slip hysteresis and so your explanation will violate the conservation of energy.
Seems clear to me that you do not understand conservation of energy.
Front wheel powers the back wheels and so if power at the back wheel can only be smaller than power on the front wheel then vehicle can not advance from left to right. The way you wrongly solve this is to say force at the back wheel is higher than force at front wheel thus vehicle can advance from left to right and this explanation is wrong as it is violating the energy conservation.
So vehicle (any of them) is not violating energy conservation since it works the way I say with energy storage but what will violate that is your wrong explanation.

Not sure what school you (most of you did) but I will sure ask for a refund.

Offline IanB

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Front wheel powers the back wheels and so if power at the back wheel can only be smaller than power on the front wheel then vehicle can not advance from left to right.

Why not?

Power does not have a direction, so whether left to right, or right to left is not relevant. If the vehicle can move, it can move in any direction we want: left, right, or sideways. It only depends on the gearing. There are no physical constraints that prevent this.
 

Offline electrodacus

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Front wheel powers the back wheels and so if power at the back wheel can only be smaller than power on the front wheel then vehicle can not advance from left to right.

Why not?

Power does not have a direction, so whether left to right, or right to left is not relevant. If the vehicle can move, it can move in any direction we want: left, right, or sideways. It only depends on the gearing. There are no physical constraints that prevent this.

Of course there is a direction as the generator wheels in order to produce the power will need to oppose the moving paper direction so whatever you extract from there you can call that breaking power.
So if you have 10W of breaking power you will need a motor on the other wheels (back wheels) that also receives 10W just for vehicle to remain stationary(ideal vehicle in real world you will need more power on the back wheels to also cover the friction losses).
So in the ideal case with 10W generated and 10W put in to motor wheels the generator wheels will push the vehicle form right to left while the motor wheels will push the vehicle in the opposite direction left to right and since the powers are equal the vehicle will just not move in any direction.

Not sure if you ever played with a generator spinning it by hand then short the wires or just connect a load to feel the difference in the amount of power you need to apply in order to maintain the same rotational speed.
At some point I think I posted a photo of a scam "free energy" where they show a motor connected trough a belt to a generator.
If you think about that say you supply the motor with power and it is connected to generator trough a belt but motor will need just say 2W to cover the friction losses and nothing more. Now if you try to take 10W from the generator you can no longer just provide 2W to the motor as then you will not be able to get the 10W from the generator but you will need to provide the motor with those 2W for friction that you provided before and maybe another 12W so a total of 14W to get the 10W from the generator.
You can never get more power from the generator than you put in the motor if there is no energy storage device.
This wheel vehicle and the motor generator scam are basically the same sort of problem. Most people seem to be OK calling that motor generator a scam but this wheel cart is the exact same problem.


People seems not to get the generator part as I hear many times in my business people saying things like while not charge my RV battery while I drive as there is power available at the alternator that is free to use since I still need to drive anyway.
They have a hard time understanding that taking 1kWh from the alternator and putting it in the battery will cost them an extra liter of gasoline so about $1/kWh or about 50x more expensive than getting that 1kWh from a solar panel.
So there is no free energy available at alternator since as soon as you take power out of alternator say 1kW then you add an extra 2kW load to the engine (alternators are typically just 50% efficient so the other 1kW is just heat in the alternator).
A liter of gasoline contains about 9kWh of energy if you burn it but since engine is typically just around 20% efficient you can see how 1 liter is needed for 1kWh took out from alternator.
Same thing happens when you use the car air conditioner to cool the car the fuel consumption will increase.

Not sure why I made such a long comment as I'm sure nobody reads my long comments.

Offline IanB

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2 W on the motor is more than enough to move the vehicle from left to right. So if you have 10 W from the generator, you have 2 W to turn the motor and 8 W spare to overcome friction and other losses. Since 2 W is much less than 10 W, there is no problem with conservation of energy.

Remember that it takes no power at all to keep the vehicle stationary. All you have to do to achieve that is to lock the motor axle so the wheels cannot turn. If it takes zero power to keep the vehicle stationary, it follows that any power greater than zero can move it to the right.
 

Offline fourfathom

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The aerospace industry , Lockheed , NASA , and all the others .
Don't use this in a wind tunnels or for replacing the use of a wind tunnel due to there significance and disturbance in testing.
So Please get over the treadmill . .. hamsters likes them .

Please think about this one.  How are you going to use a treadmill to test the aerodynamics of a car or airplane?  Put the plane on a mile-long treadmill and run alongside with your instrumentation?  You might as well try to measure things while actually flying the plane.  They use a wind tunnel because it is a good way of generating an airflow on a stationary object (that "reference frame" thing).
« Last Edit: September 18, 2021, 02:15:37 pm by fourfathom »
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Offline electrodacus

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2 W on the motor is more than enough to move the vehicle from left to right. So if you have 10 W from the generator, you have 2 W to turn the motor and 8 W spare to overcome friction and other losses. Since 2 W is much less than 10 W, there is no problem with conservation of energy.

Remember that it takes no power at all to keep the vehicle stationary. All you have to do to achieve that is to lock the motor axle so the wheels cannot turn. If it takes zero power to keep the vehicle stationary, it follows that any power greater than zero can move it to the right.


I think is best to mention what you are seeing in my slow motion video https://odysee.com/@dacustemp:8/wheel-cart-energy-storage-slow:8
If you want to take everything as it is there no modified reference frame then what it represents is vehicle driving against the wind direction with wind being the moving piece of paper and vehicle driving much slower than the wind speed.
If you want to look at it as vehicle driving in same direction as the wind speed then you need to consider the implications of modified reference frame.
You switch vehicle and road so vehicle kinetic energy is now the road (moving paper kinetic energy) and vice versa.
So when you consider everything correctly the result will be clear as you take much more energy from the moving paper (vehicle kinetic energy) than you put back in.

I just feel that there are to many things that you (all) do not understand and so it makes sense why I can not explain to you how the vehicle works.
Even if I'm able to explain one thing there are 10 more things that you wrongly understand (or better to say do not understand).

At this point I'm happy if I can make people understand the wheel only vehicle and why that can not move from left to right without energy storage.
Think at the exact moment that back wheel starts to move and what is powering that as the front wheel can not do it without the help of stored energy.
I wish I had a more robust toy vehicle so that there was much less energy storage so that vehicle can not move to demonstrate that to you also but not sure if that will have been of any help since you also need to understand the theoretical part of why the vehicle works the way it does.

Online NiHaoMike

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People seems not to get the generator part as I hear many times in my business people saying things like while not charge my RV battery while I drive as there is power available at the alternator that is free to use since I still need to drive anyway.
They have a hard time understanding that taking 1kWh from the alternator and putting it in the battery will cost them an extra liter of gasoline so about $1/kWh or about 50x more expensive than getting that 1kWh from a solar panel.
So there is no free energy available at alternator since as soon as you take power out of alternator say 1kW then you add an extra 2kW load to the engine (alternators are typically just 50% efficient so the other 1kW is just heat in the alternator).
A liter of gasoline contains about 9kWh of energy if you burn it but since engine is typically just around 20% efficient you can see how 1 liter is needed for 1kWh took out from alternator.
Those figures are a bit dated, a modern Atkinson cycle engine can reach 40%. And what makes more sense is to charge the batteries using regenerative braking.
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Offline electrodacus

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Those figures are a bit dated, a modern Atkinson cycle engine can reach 40%. And what makes more sense is to charge the batteries using regenerative braking.

We are not talking about best record efficient engine but about what people actually have and 1 liter /kWh is a rounded value but fairly close to what 90% of vehicles will get.
Obviously regenerative breaking is great as instead of wasting that energy as heat on the brake disks you can use it to charge the battery.
Tho you will need modifications done to your vehicle to be able to do that if you do not have an EV or hybrid vehicle.
In any case way to many people think charging the battery from alternator is free as in there is no fuel penalty.
Same happens here where people think they can take energy from the wheel of the blackbird and somehow that has no effect on the vehicle speed / kinetic energy.

Offline ejeffrey

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Of course there is a direction as the generator wheels in order to produce the power will need to oppose the moving paper direction so whatever you extract from there you can call that breaking power.
So if you have 10W of breaking power you will need a motor on the other wheels (back wheels) that also receives 10W just for vehicle to remain stationary(ideal vehicle in real world you will need more power on the back wheels to also cover the friction losses).

We are actually maybe getting somewhere here.  The paper does positive work on the cart.  Work (energy) is force * displacement while power = force * velocity.  If the force and velocity are in the same direction then the power input is positive and can increase the kinetic energy of the car.  If they are in opposite directions it the work is negative and will decrease kinetic energy.  While the paper is moving backwards and the cart is moving forwards, the bottom surface of the wheel is moving backwards so the work done is actually positive.  This power input is what allows the cart to accelerate, or in the steady state with no acceleration provides energy to overcome frictional losses.  Due to the gear ratios the acceleration of the cart is in the opposite direction of the force applied to the wheel, but that is no big deal because energy doesn't have a direction.

The table provides a forward force but since it is stationary and so is the bottom of the wheel it does no net work.  The table is still important because we still need a forward force to balance F=ma.  But the table can provide that balancing force without doing any work, positive or negative.
 

Offline electrodacus

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Of course there is a direction as the generator wheels in order to produce the power will need to oppose the moving paper direction so whatever you extract from there you can call that breaking power.
So if you have 10W of breaking power you will need a motor on the other wheels (back wheels) that also receives 10W just for vehicle to remain stationary(ideal vehicle in real world you will need more power on the back wheels to also cover the friction losses).

We are actually maybe getting somewhere here.  The paper does positive work on the cart.  Work (energy) is force * displacement while power = force * velocity.  If the force and velocity are in the same direction then the power input is positive and can increase the kinetic energy of the car.  If they are in opposite directions it the work is negative and will decrease kinetic energy.  While the paper is moving backwards and the cart is moving forwards, the bottom surface of the wheel is moving backwards so the work done is actually positive.  This power input is what allows the cart to accelerate, or in the steady state with no acceleration provides energy to overcome frictional losses.  Due to the gear ratios the acceleration of the cart is in the opposite direction of the force applied to the wheel, but that is no big deal because energy doesn't have a direction.

The table provides a forward force but since it is stationary and so is the bottom of the wheel it does no net work.  The table is still important because we still need a forward force to balance F=ma.  But the table can provide that balancing force without doing any work, positive or negative.

You also need to consider what the example represents.
Moving paper is the energy source for the vehicle and is the analog of win in a wind powered vehicle. So in my video you see the equivalent of a vehicle moving in the opposite direction to wind direction at around half the wind speed.

If you want to see things in modified reference frame and want to consider the moving paper as the road so the vehicle and road reference frame are switched then you need to consider that kinetic energy of the vehicle and road (moving paper) have been switched so when trying to interpret what happens with vehicle speed you will need to look at the paper not vehicle.

So an ideal vehicle traveling at a fixed speed of say 10m/s will have a certain kinetic energy based on speed and weight and you will consider ground as stationary and thus no kinetic energy.
If for some reason you want to look at this system from a modified frame of reference and switch the vehicle characteristics with ground and then continue the experiment from there then you need to look at now moving ground kinetic energy to know what happens with vehicle speed.
I do not get why people will want to change reference frame and deal with all the complexities of that (seems people wrongly think changing reference frame has no implications and then get to wrong conclusions).

So in my video when analyzing that vehicle you either look at it as wind powered vehicle traveling against wind direction at half the wind speed and all is what it seems no modified reference frame.
Or you consider the modified reference frame to analyze a vehicle traveling above wind speed in the same direction as the wind but then you need to look at what happens with moving paper (road) energy as that is switched with the vehicle kinetic energy.
So for example in that period where only the front wheel rotates the vehicle seems stationary while energy is put in to rubber band but if you interpret correctly the modified reference frame you will need to look at how much energy you took from the paper to charge that rubber band and since that is not zero it means vehicle speed was reduced during that period (not obvious if you just look at the vehicle).

Online Kleinstein

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If for some reason you want to look at this system from a modified frame of reference and switch the vehicle characteristics with ground and then continue the experiment from there then you need to look at now moving ground kinetic energy to know what happens with vehicle speed.
I do not get why people will want to change reference frame and deal with all the complexities of that (seems people wrongly think changing reference frame has no implications and then get to wrong conclusions).

The change of reference frame is helpfull. If one understands how to do it, it is a realtively simple step - though it can confuse others.

An obvious point with the change of reference frame is that the movement would be the same independent from the reference frame. So if you look at it with the fixed ground as reference and you accept that the vehicle moves to the right this means that with the pater as the reference from the vehicle will more faster than the driving system (the ground).  When looking at kinetic energies the change of reference frame can be a bit complicated. When looking at force it is not at all complicated. When your argument has a problem with the change of refrence frame and gives different results (e.g. violation of conservation of energy in one frame but OK in the other) than this shows a problem in your "theory" understanding.

The change of reference frame is mainly needed to understand the experiment with the vehicle on the treadmill.  The same step is than used for the wheeled vehicle on the treadmill. So the slow wheeled vehicle is a direct analog to the prop driven vehicle on the treadmill.
 

Offline Brumby

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I had a look at your video and I can see where your argument is based - however it is nowhere near an accurate representation of the Blackbird mechanism.  The best I can say is that it is somewhat backwards and that this claim:
You can see the effect of how blackbird works in my slow down video version.
is completely invalid.  You presume your presentation models the Blackbird mechanism - which it clearly does not.

If you want to insist on there being some form of energy storage, then the only quarter I will give in that direction is that there is energy in the wind.

Nevertheless, all our arguments have been, are and will continue to be in vain if you persist with this generator/motor wheels topology.  The key elements here are the wheels, the propeller and the driveline between them in a windy environment.

Those elements have been explored in two frames of reference, which have both shown the effect is real.  These frames of reference are:
 1. with respect to the ground, where the vehicle is in motion, as is the air (wind)
 2. with respect to the vehicle, where only the ground is in motion and the air is still
In both frames, the wheels are rotating and the propeller is spinning


Your generator/motor wheels topology is not appropriate - yet you continue to insist that it is.  The problem is that you cannot (or will not) consider it might not be correct ... and it is this stubbornness that will see you consistently mislead yourself.
« Last Edit: September 18, 2021, 02:00:48 pm by Brumby »
 

Online Alex Eisenhut

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Jesus Christ! STILL can't spell BRAKING correctly?  |O

Look, the spinning propeller creates a virtual sail behind the vehicle. It pushes against the wind, if you sum the velocities you end up with 0, but since it's blowing backwards, it adds to the ground velocity of the vehicle.

You can view this virtual sail as storing the initial energy of the vehicle being blown from rest to its cruising velocity.
Hoarder of 8-bit Commodore relics and 1960s Tektronix 500-series stuff. Unconventional interior decorator.
 
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Online iMo

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"Flywheel storage" - that is a concept which works.
Why the rotating propeller and rotating wheels cannot be considered (in the Blackbird's case) an "energy storage"?
https://en.wikipedia.org/wiki/Flywheel_energy_storage
 

Offline electrodacus

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    • electrodacus
"Flywheel storage" - that is a concept which works.
Why the rotating propeller and rotating wheels cannot be considered (in the Blackbird's case) an "energy storage"?
https://en.wikipedia.org/wiki/Flywheel_energy_storage

They are an energy storage and spinning propeller due to much larger weight and diameter stores significantly more energy that all wheels combined so usually I do not mention the wheels.
But this energy storage can not by itself accelerate the vehicle above wind speed that is why it was ignored even if I'm sure they considered that.
To be more precise the propeller flywheel storage effect is not useful if blade pitch is fixed but it is not so that is another mistake they made allowing variable blade pitch.
Still even vehicle with no variable blade pitch like the small treadmill model shows it can exceed wind speed meaning that another energy source is responsible for exceeding wind speed and that is pressure differential energy storage.
Seems pressure differential energy storage is less known as it is a very different type of energy storage and less useful.  Perfect equivalent for pressure differential energy storage is an inductor and also not many people see the inductor as a useful energy storage device compared to a capacitor that will be perfect analog of a flywheel.
The difference is that in a capacitor same as in a flywheel you can store energy longer therm with minimal losses while in an inductor and pressure differential you need to maintain a current to keep the stored energy else if you stop the energy gets dissipated super fast so no long therm storage is possible like with a capacitor / flywheel.
Same as amount of energy is very significant with a large flywheel (like the one on blackbird) vs a typical electrolytic capacitor there is a large difference in storage capacity between a typical inductor and the pressure differential created by blackbird propeller.
So blackbird electrical circuit equivalent is made of a large inductor and two capacitors (pressure differential and flywheel + vehicle kinetic energy).
While the pressure differential discharges it charges the flywheel and vehicle kinetic energy that is proportional with vehicle speed.
There is also a resistor in circuit representing the friction losses so the inductor (pressure differential) that is charged in the initial acceleration phase (vehicle well below wind speed) is then discharged and that energy charges the two capacitors and some smaller part is lost in the resistor (representing friction).

Not sure is you have enough electrical knowledge to find the analogy useful but someone here most likely has that knowledge.


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