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Posted
If you ask me – I don’t know the equation. Here is my reason to believe. I hope you can read from picture. I just check this with the simulating program. If this reasoning is wrong, where is the mistake?

 

The green arrows represent a vertical force if and only if there is an equal and opposite force to offset it. The reaction shows a torque or moment but if that point was fixed there would be a reactionary force there as well. If it is free to move at that point, that point will accelerate downward due to this equal and opposite force that is not shown. There will be no net lift. The thing might be able to jump, but it will never hover.

Posted
If you ask me – I don’t know the equation. Here is my reason to believe. I hope you can read from picture. I just check this with the simulating program. If this reasoning is wrong, where is the mistake?

 

But the simulation program needs a force (or acceleration) in order to calculate the motion. How did you do that?

 

Precession is a constant angular speed motion in response to a torque. It's not a linear force.

Posted
The green arrows represent a vertical force if and only if there is an equal and opposite force to offset it. The reaction shows a torque or moment but if that point was fixed there would be a reactionary force there as well. If it is free to move at that point, that point will accelerate downward due to this equal and opposite force that is not shown. There will be no net lift. The thing might be able to jump, but it will never hover.

Yes, to my regret I think you are right …

Maybe something wrong happen with the simulating software when I transfer the models from Solid Edge to Parasolid and then to Visual Nastran.

I will try to make the model directly in Visual Nastran to see what will happen.


Merged post follows:

Consecutive posts merged
But the simulation program needs a force (or acceleration) in order to calculate the motion. How did you do that?

 

Precession is a constant angular speed motion in response to a torque. It's not a linear force.

 

Well, I thought that a tendency for precession which will appear in response to a motor torque (and which starting direction is UP) can oppose to gravity, but now I am very hesitate in my opinion.

Posted

I think we've made excellent progress here. The important part is to recognize that simulations are extremely useful tools, but you have to careful in applying what is learned from them.

 

I know of at least 2 published simulations that were wrong. In both cases the material slipped through the journal review case because the reviewers did not understand the material. The authors were unclear as well.

 

Fortunately, the other people on this forum seem quite good at understanding these issues - much better than I can.

 

I think that there are many interesting things for you to learn here as you work with your simulations and perfect them.

Posted

Well, I thought that a tendency for precession which will appear in response to a motor torque (and which starting direction is UP) can oppose to gravity, but now I am very hesitate in my opinion.

 

You would need something to block the rotation in order to convert this to motion. You could get a torque which could lift up an axle on one end, for example, but only it were on a surface. That way the surface could exert a force.

 

The questions other have been asking, "what does the force act on?" are very important to the discussion. Or, put another way, how is linear momentum being conserved?

Posted

Ok, I understand that I have to push something to get its reaction to push me, but by the same reason I can get a torque without being on a surface and there is no need to block the rotation to have a torque – if I rotate something it rotates me but there is a torque. So, this device could work if precession was a linear motion, but not angular.

I can’t answer to the question how is linear momentum being conserved here, because I don’t think that this device will work (for the present:-)), but the things are not always so clear.

What will you say about that:

While a torque acts on an object (gyroscope) the result is a CONSTANT angular speed motion (precession).

Instead of:

While a torque acts on an object the result is ACCELERATING angular speed motion.

Posted
Ok, I understand that I have to push something to get its reaction to push me, but by the same reason I can get a torque without being on a surface and there is no need to block the rotation to have a torque – if I rotate something it rotates me but there is a torque. So, this device could work if precession was a linear motion, but not angular.

I can’t answer to the question how is linear momentum being conserved here, because I don’t think that this device will work (for the present:-)), but the things are not always so clear.

What will you say about that:

While a torque acts on an object (gyroscope) the result is a CONSTANT angular speed motion (precession).

Instead of:

While a torque acts on an object the result is ACCELERATING angular speed motion.

 

Look carefully at the torque during precession. Is it constant?

Posted
Look carefully at the torque during precession. Is it constant?

 

Well, I can’t see the reason why torque not to be constant during precession. The magnitude of torque has influence on the speed of precession but this speed is constant.

 

Gyroscope just has strange reaction on torque. And this reaction is a criminal – it rudely breaks Newton’s laws:

 

Let’s imagine a stone with a gyroscope inside and we don’t know that. The gyroscope inside have constant angular velocity. And let’s imagine that we are in space without gravity.

1. Now there are no outside actions and noting happened – first Newton’s law is satisfied.

2. We decide to action on that stone with a constant torque (with two small jets for example) and, according to Newton’s second law, we expect this stone to start rotation with increasing angular velocity (angular acceleration). But stone respond us with rotation where angular velocity is constant. The second Newton’s law is broken.

3. According to Newton’s third law we expect equal and opposite reaction but what we find? Reaction in another direction. The third Newton’s law is broken.

Posted

Gyroscope just has strange reaction on torque. And this reaction is a criminal – it rudely breaks Newton’s laws

 

No. Really, if you come into a situation where it appears that physical law is broken, one really needs to re-evaluate the data and the analysis. That's invariably where the problem is.

 

But stone respond us with rotation where angular velocity is constant. The second Newton’s law is broken.

 

Angular velocity, or angular speed? There's a big difference. For the angular velocity to be constant, the rotation axis must always point in the same direction. Precession, by definition, is the change in the orientation of this axis.

Posted

 

Angular velocity, or angular speed? There's a big difference.

 

Ok, I will try to understand the difference. In Bulgarian there is only one word for speed (or velocity) I think ...

Posted
Well, I can’t see the reason why torque not to be constant during precession. The magnitude of torque has influence on the speed of precession but this speed is constant.

 

Gyroscope just has strange reaction on torque. And this reaction is a criminal – it rudely breaks Newton’s laws:

 

Let’s imagine a stone with a gyroscope inside and we don’t know that. The gyroscope inside have constant angular velocity. And let’s imagine that we are in space without gravity.

1. Now there are no outside actions and noting happened – first Newton’s law is satisfied.

2. We decide to action on that stone with a constant torque (with two small jets for example) and, according to Newton’s second law, we expect this stone to start rotation with increasing angular velocity (angular acceleration). But stone respond us with rotation where angular velocity is constant. The second Newton’s law is broken.

3. According to Newton’s third law we expect equal and opposite reaction but what we find? Reaction in another direction. The third Newton’s law is broken.

 

The magnitude of torque, may be constant, but the direction (axis) of that torque constantly changes. (compare it, say, at 180 degrees of precession)

 

2,3. None of Newton's laws are broken

Posted (edited)
... the direction (axis) of that torque constantly changes.

 

But what changes it? - The reaction.

And what the Law says? - For every action there is an equal and opposite reaction.

If the reaction was opposite there would be no change in direction.

 

 

P.S. Ok I wrote it too fast... I am thinking now if the changeing of direcion of toorque means that the reaction is not opposite in every moment of time...

Edited by savata71
Posted
But what changes it? - The reaction.

And what the Law says? - For every action there is an equal and opposite reaction.

If the reaction was opposite there would be no change in direction.

 

 

P.S. Ok I wrote it too fast... I am thinking now if the changeing of direcion of toorque means that the reaction is not opposite in every moment of time...

 

Newton's third law always involves two different objects that feel the reaction force (or torque) It's not clear to me if you are using it properly here.

Posted (edited)

The question about Newton’s laws and how they appear, especially when we talk about gyroscopes, is too hard for me. There are many things involved here. I just have to learn more.

 

For now I can give advice to those who will make computer simulations (like sterologist said before):

 

You saw how I made mistake in my suppositions and how simulating software confirm these wrong suppositions (unbelievable coincidence of mistakes).

 

So, be very careful when you make deductions based on computer simulations!

Edited by savata71

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