Newton's third law problem.

[IanB]

You did that yourself with your gif animation.

You had a 3:2 gear ratio
Showed a wheel traveling 3 squares and the other 2 squares while vehicle also moved one square.
I mentioned to fix one of the moving surfaces to represent the earth and your answer was

"With the fixed ground on the left the treadmill moves to the right one square. When this happens the vehicle moves two squares to the left."

I asked if you observe such a thing in reality meaning treadmill moves one square relative to ground while vehicle moves two squares also relative to ground.

I obviously got no answer from you.

It didn't deserve an answer. Of course it would do the same thing in reality. It is a model of reality.

In the same way you can claim that with a 1:1 gear ratio the vehicle moves 2 squares while treadmill does not move at all.

Equally, of course you cannot claim this. Because no accurate model will predict such a thing.

[IanB]

If it exceeds wind speed directly downwind or it drives at any speed directly upwind you know for sure energy storage is involved as else it can not work based on currently agreed laws of physics.

There are no "currently agreed" laws of physics that would claim this. You are the only person who says this. Every textbook, every physics professor, everyone in this forum, every qualified engineer in the world would disagree with you.

You keep making incorrect statements, such as suggesting that power has a direction like "left" or "right", "forwards" or "backwards", when everyone here has repeatedly told you that power is a scalar quantity, it has no direction.

[electrodacus]

Equally, of course you cannot claim this. Because no accurate model will predict such a thing.

Your mathematical model will can predict almost anything with not many constraints.
And yes you can show your vehicle moving two squares relative to the grid and of course 2 squares on the fixed treadmill representing ground and also two squares on the non moving treadmill.
But if you insist in treadmill moving you can move it 1 square and vehicle can move any random value relative to ground.
 
The thing that your model is not considering is Newton's 3'rd law.
The gear is locked and treadmill applying a force to the generator wheel will not create a larger force at the motor wheel because that is physically possible without some other external force or force provided by stored energy.
Since there are no other external sources it is clear is energy storage. (Also demonstrated in my slow motion video).

I'm still not sure if is the wrong understanding of the difference between power and energy or the fact that any action has an equal and opposite reaction.

Power at the motor wheel will always be lower than power at the generator wheel meaning vehicle can not move against the direction of the treadmill powering the generator wheel.
Power out (at the motor wheel) will need to be larger than power extracted at the generator wheel in order for the vehicle to move against the treadmill direction and the only way to do that is to store energy then use that stored energy to power the motor wheel at any power you want (higher power for lower duration or lower power for longer duration but always more than generated at that time in order to be able to move in the other direction).

Why do none of you use the electric model ?  It should be harder to make mistakes for someone with electrical knowledge (at least I will think so).
But no matter if electrical or mechanical system the output power will always be lower unless you add energy storage and then for small portion of time you can output higher power by using stored energy.

[electrodacus]

If it exceeds wind speed directly downwind or it drives at any speed directly upwind you know for sure energy storage is involved as else it can not work based on currently agreed laws of physics.

There are no "currently agreed" laws of physics that would claim this. You are the only person who says this. Every textbook, every physics professor, everyone in this forum, every qualified engineer in the world would disagree with you.

You keep making incorrect statements, such as suggesting that power has a direction like "left" or "right", "forwards" or "backwards", when everyone here has repeatedly told you that power is a scalar quantity, it has no direction.

Actually there are and law of conservation of energy is a law for a good reason.
Your output (propulsion) power can not be larger than input generated power.

I showed the wind power equation used by any engineer in the world that needs it and it shows that wind power available is highest when the wind speed is highest relative to vehicle and zero when there is no wind speed relative to vehicle.

So a vehicle can move against the wind direction only when output (propulsion power) is higher than input wind power.
Since that can not happen due to energy conservation law you need to use energy storage to move a vehicle upwind.

If you ever swimmed in a river against the current without being anchored to the ground you will have needed a minimum power just to maintain your position relative to the ground.

[IanB]

Equally, of course you cannot claim this. Because no accurate model will predict such a thing.

Your mathematical model will can predict almost anything with not many constraints.

But the model does have constraints. It is constrained by an accurate representation of the system. What the model does, the real system does. And vice versa.

And yes you can show your vehicle moving two squares relative to the grid and of course 2 squares on the fixed treadmill representing ground and also two squares on the non moving treadmill.
But if you insist in treadmill moving you can move it 1 square and vehicle can move any random value relative to ground.

And what's wrong with that?
 

The thing that your model is not considering is Newton's 3'rd law.

Because it is not relevant.

The gear is locked and treadmill applying a force to the generator wheel will not create a larger force at the motor wheel because that is physically possible without some other external force or force provided by stored energy.

This is demonstrably not true. If I have a 10:1 lever, I can apply a force of 1 N on the longer end and get a force of 10 N at the shorter end. Gears are no different from levers. Even if the wind exerts a force of 1 N on the vehicle, we can use gearing to make the motor exert a force of 10 N at the wheels in the opposite direction.

Since there are no other external sources it is clear is energy storage. (Also demonstrated in my slow motion video).

Clearly not true, as above.

I'm still not sure if is the wrong understanding of the difference between power and energy or the fact that any action has an equal and opposite reaction.

Everyone has been asking you to look inside yourself for the wrong understanding, but you won't do it.

Power at the motor wheel will always be lower than power at the generator wheel

True

meaning vehicle can not move against the direction of the treadmill powering the generator wheel.

Not true. Any small amount of power at the motor wheel can move the vehicle with appropriate gearing.

Power out (at the motor wheel) will need to be larger than power extracted at the generator wheel in order for the vehicle to move against the treadmill direction and the only way to do that is to store energy then use that stored energy to power the motor wheel at any power you want (higher power for lower duration or lower power for longer duration but always more than generated at that time in order to be able to move in the other direction).

Not true. See above.

Why do none of you use the electric model ?  It should be harder to make mistakes for someone with electrical knowledge (at least I will think so).
But no matter if electrical or mechanical system the output power will always be lower unless you add energy storage and then for small portion of time you can output higher power by using stored energy.

The electrical model is even easier. As long as there is some small power at the electric motor the vehicle can move. The stronger the wind, the more power, so the easier it is for the vehicle to move.

If it exceeds wind speed directly downwind or it drives at any speed directly upwind you know for sure energy storage is involved as else it can not work based on currently agreed laws of physics.

There are no "currently agreed" laws of physics that would claim this. You are the only person who says this. Every textbook, every physics professor, everyone in this forum, every qualified engineer in the world would disagree with you.

You keep making incorrect statements, such as suggesting that power has a direction like "left" or "right", "forwards" or "backwards", when everyone here has repeatedly told you that power is a scalar quantity, it has no direction.

Actually there are and law of conservation of energy is a law for a good reason.

Conservation of energy is not a useful analysis here.

Your output (propulsion) power can not be larger than input generated power.

True, but irrelevant.

I showed the wind power equation used by any engineer in the world that needs it and it shows that wind power available is highest when the wind speed is highest relative to vehicle and zero when there is no wind speed relative to vehicle.

As has previously been explained by many people, it is the wind speed relative to the ground that decides how much power can be extracted by the vehicle, not the speed relative to the vehicle. If you take an equation and apply it incorrectly, you will draw incorrect conclusions.

So a vehicle can move against the wind direction only when output (propulsion power) is higher than input wind power.

As repeated many times, not true.

Since that can not happen due to energy conservation law you need to use energy storage to move a vehicle upwind.

Nonsense.

If you ever swimmed in a river against the current without being anchored to the ground you will have needed a minimum power just to maintain your position relative to the ground.

Yes, but the vehicle is anchored to the ground. It has wheels with friction in contact with the ground. So the swimming analogy does not apply. The swimming analogy would only apply to a free floating airship above the ground (a body which would be "swimming" in the air).

[electrodacus]

But the model does have constraints. It is constrained by an accurate representation of the system. What the model does, the real system does. And vice versa.


This is demonstrably not true. If I have a 10:1 lever, I can apply a force of 1 N on the longer end and get a force of 10 N at the shorter end. Gears are no different from levers. Even if the wind exerts a force of 1 N on the vehicle, we can use gearing to make the motor exert a force of 10 N at the wheels in the opposite direction.

This must be a record. I was not going to replay but there are parts that I want to help you with.

Your constraints are just geometrical. Not enough for physical simulation.

You can only get 10N out with 1N in if the body of the gearbox is not floating as it is for this example vehicle.
In the case where gearbox body is floating (not attached to anything) your output force can not be anything other than equal with input force.

Take a pair of scissors have it open it half way and glue some adhesive tape between the tip of the cutting blade on one side and at half the distance between the tip and the pivot point on the other side.
Now try and pull apart the two handles and see if you can have two different forces at the two handles
If you can prove that force is different at one of the handles I will be happy to admit I was wrong.
But I hope you do not even need to do the test to know you can not get a different force at one handle than on the other one.

[electrodacus]

All usable gearboxes have 3 points of contact.

1) Input
2) Output
3) Body

If the body of the gearbox is not connected to anything as it is the case for all this vehicles then output force can not be different from input force.

If you have a vehicle you can imagine the gearbox body being disconnected from the vehicle body and if say it is also locked the force at the input will be exactly the same as on the output.
You can not have a usable gearbox with only input and output connected with the body floating. You always need 3 points for the gearbox to work.

So this is not a usable gearbox with just two points of contact in total.

[fourfathom]

All usable gearboxes have 3 points of contact.

1) Input : Ground
2) Output: Propeller / Air
3) Body: Chassis

[IanB]

This must be a record. I was not going to replay but there are parts that I want to help you with.

Then stop trying to help. You cannot be a successful student if you keep trying to teach instead of learning.

Your constraints are just geometrical. Not enough for physical simulation.

I gave you the example of a pantograph. Look it up. It has only geometrical constraints.

You can only get 10N out with 1N in if the body of the gearbox is not floating as it is for this example vehicle.

In the very previous post we had the point where it is not floating. It is sitting on the ground.

In the case where gearbox body is floating (not attached to anything) your output force can not be anything other than equal with input force.

Then you need to enlarge your understanding of how gears work.

Take a pair of scissors have it open it half way and glue some adhesive tape between the tip of the cutting blade on one side and at half the distance between the tip and the pivot point on the other side.
Now try and pull apart the two handles and see if you can have two different forces at the two handles
If you can prove that force is different at one of the handles I will be happy to admit I was wrong.
But I hope you do not even need to do the test to know you can not get a different force at one handle than on the other one.

Yes, this is exactly the example to think about. Suppose the force between the handles is 10 N. What is the force (tension) on the tape?

[IanB]

So this is not a usable gearbox with just two points of contact in total.

Having F1 equal to F2 is not relevant to how the vehicle will move. Forces are useful in static analysis problems. They do not help with kinematic problems like this one. The vehicle will move in accordance with how all the parts are connected. It is pure geometry. Unless you think the real world does not obey geometric constraints?

[Alex Eisenhut]

Thanks for taking the time to replay.

Sorry, but:

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[electrodacus]

Having F1 equal to F2 is not relevant to how the vehicle will move. Forces are useful in static analysis problems. They do not help with kinematic problems like this one. The vehicle will move in accordance with how all the parts are connected. It is pure geometry. Unless you think the real world does not obey geometric constraints?

OK so you understood the floating gearbox problem.
Static analysis is the important part here. Vehicle is stationary to start so you need a higher F2 if you want to accelerate the vehicle to the right.
What helps you have a higher F2 is both energy storage in the rubber belt and stick slip hysteresis as shown clearly in the slow motion video.

[electrodacus]

Sorry, but:

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Thanks for the correction. I'm sure you can find way more than that if you search.

[electrodacus]

In the very previous post we had the point where it is not floating. It is sitting on the ground.

Can you be more specific ? Where there 3 points of contact for the gearbox ?

Then you need to enlarge your understanding of how gears work.

Like I mentioned a gearbox with floating body is not actually a gearbox.

Yes, this is exactly the example to think about. Suppose the force between the handles is 10 N. What is the force (tension) on the tape?

Force at the tape is irrelevant as that represents the belt and the only points making contacts are the two handles one is the input the other the output with the floating body and non relevant internal mechanism because the body is floating.

[electrodacus]

All usable gearboxes have 3 points of contact.

1) Input : Ground
2) Output: Propeller / Air
3) Body: Chassis

What vehicle are you referring here ?
I'm going to guess the direct downwind version.

Yes input wheel is in contact with ground and the propeller is the output but the body of the gearbox is floating even if it just happens that the body of the gearbox can also be called the body.

The problem is that input is not between the body and the wheels. There is no internal engine or motor witch will be connected with the stator to body and rotor to gearbox input. 

[IanB]

Static analysis is the important part here. Vehicle is stationary to start so you need a higher F2 if you want to accelerate the vehicle to the right.
What helps you have a higher F2 is both energy storage in the rubber belt and stick slip hysteresis as shown clearly in the slow motion video.

Firstly, there is no rubber belt and no stick slip hysteresis because this is a CAD model. It does not contain those elements.

Secondly, no such invention is needed. If you move the treadmill, then by necessity the wheel on the treadmill will turn, and the belt will move, and the other wheel will turn, and the cart will move.

[IanB]

Can you be more specific ? Where there 3 points of contact for the gearbox ?

The axles (or bearings), the input shaft and the output shaft.

Like I mentioned a gearbox with floating body is not actually a gearbox.

But it is not actually floating. When the input shaft rotates the gearbox is not free to rotate with it, it is fixed to the body of the cart. It would only be a floating gearbox if it was free to rotate with the input shaft.

Force at the tape is irrelevant as that represents the belt and the only points making contacts are the two handles one is the input the other the output with the floating body and non relevant internal mechanism because the body is floating.

Not at all irrelevant, because forces come in pairs (Newton's 3rd law: every force has an equal and opposite reaction). In the same way that there is no such thing as a voltage at a single point (a voltage is always a difference between two points), there is no such thing as a force at a single point. There is always a reacting force paired with it. So the force pair on the handle of the scissors is like the input voltage on the primary of a transformer, and the force pair on the blades of the scissors is like the output voltage on the secondary of the transformer. Bear in mind that a transformer can often be floating; it does not have to be grounded at all.

[electrodacus]

Firstly, there is no rubber belt and no stick slip hysteresis because this is a CAD model. It does not contain those elements.

Secondly, no such invention is needed. If you move the treadmill, then by necessity the wheel on the treadmill will turn, and the belt will move, and the other wheel will turn, and the cart will move.

Exactly. Since the diagram makes no mention about belt or any other part being elastic and since slip is also not mentioned then this diagram as a problem will  represent a system that can not move as F2 can not be larger than F1 no matter how large the F1 is the system will not move.

[IanB]

Exactly. Since the diagram makes no mention about belt or any other part being elastic and since slip is also not mentioned then this diagram as a problem will  represent a system that can not move as F2 can not be larger than F1 no matter how large the F1 is the system will not move.

This is faulty reasoning. The movement of the cart has nothing to do with the size of F2 and F1. They don't affect the analysis.

[electrodacus]

The axles (or bearings), the input shaft and the output shaft.

The input shaft is connected to treadmill and the output shaft to ground.
That is all the rest represent the gearbox body that is not connected to anything.

But it is not actually floating. When the input shaft rotates the gearbox is not free to rotate with it, it is fixed to the body of the cart. It would only be a floating gearbox if it was free to rotate with the input shaft.

The gearbox body is not connected to anything so it is free to rotate with the input shaft if there is enough friction in the front wheel bearing.

Not at all irrelevant, because forces come in pairs (Newton's 3rd law: every force has an equal and opposite reaction). In the same way that there is no such thing as a voltage at a single point (a voltage is always a difference between two points), there is no such thing as a force at a single point. There is always a reacting force paired with it. So the force pair on the handle of the scissors is like the input voltage on the primary of a transformer, and the force pair on the blades of the scissors is like the output voltage on the secondary of the transformer. Bear in mind that a transformer can often be floating; it does not have to be grounded at all.

Not quite sure the analogy works.
But an electronic component with just two connections will have the same current at input and output.

So F1 is the equal and opposite force in this setup and so they will always be equal unless energy storage and stick slip hysteresis or some similar trigger for charge discharge exist.

[electrodacus]

This is faulty reasoning. The movement of the cart has nothing to do with the size of F2 and F1. They don't affect the analysis.

That is your mathematical approach only. The cart can not move if all forces acting on it are equal and opposite.
In the math model you do not care about physics just geometry so you select an arbitrary distance that you want to move the vehicle and then plot the movement of all parts but in real world there is nothing that can move the vehicle if there is no energy storage and stick slip hysteresis.

[IanB]

The gearbox body is not connected to anything so it is free to rotate with the input shaft if there is enough friction in the front wheel bearing.

Don't be absurd. The gearbox is fixed to the cart, so it can't rotate unless the cart rotates, which clearly the cart doesn't.

So F1 is the equal and opposite force in this setup and so they will always be equal unless energy storage and stick slip hysteresis or some similar trigger for charge discharge exist.

F1 acting on the wheel has an equal and opposite force F1' acting on the belt the wheel is in contact with. F2 can be anything different from F1, depending on the design of the system, and F2 definitely doesn't have to be equal and opposite to F1.

[electrodacus]

Don't be absurd. The gearbox is fixed to the cart, so it can't rotate unless the cart rotates, which clearly the cart doesn't.


F1 acting on the wheel has an equal and opposite force F1' acting on the belt the wheel is in contact with. F2 can be anything different from F1, depending on the design of the system, and F2 definitely doesn't have to be equal and opposite to F1.

The cart body just happens to be the same with the gearbox body.

There will be no F2 without F1 and if slip is not allowed and there is no energy storage then F2 will be equal and opposite of F1.

This device can be called a cart or a gearbox it just depends on the definition you want to give but there is nothing more than just a gearbox.
It has the input connected to treadmill the output to ground and the body not connected to anything.

[IanB]

The cart body just happens to be the same with the gearbox body.

And since the cart doesn't fly through the air doing somersaults, we can agree that the cart/gearbox doesn't rotate, right?

There will be no F2 without F1 and if slip is not allowed and there is no energy storage then F2 will be equal and opposite of F1.

There is no law of physics that says this.

This device can be called a cart or a gearbox it just depends on the definition you want to give but there is nothing more than just a gearbox.
It has the input connected to treadmill the output to ground and the body not connected to anything.

Just like car's gearbox then? It has the input connected to the engine, the output to the road, and the body not connected to anything? And yet, somehow, the gearbox in a car works.

[electrodacus]

And since the cart doesn't fly through the air doing somersaults, we can agree that the cart/gearbox doesn't rotate, right?

It could fly if the friction is high enough or the acceleration rate of the treadmill is large enough.
The point is the body is floating.

There is no law of physics that says this.

It is for this particular gearbox configuration as it is locked basically no different from a rock

Just like car's gearbox then? It has the input connected to the engine, the output to the road, and the body not connected to anything? And yet, somehow, the gearbox in a car works.

The car gearbox body is connected to the motor stator or engine body.
It is like the treadmill body was connected to this vehicle body instead of the ground.