[Bobolink]

Bobolink,
What happens when the Cubli rotates in zero-g?
Will the outside frame rotate 45 degrees as in the video if the frame is not attached to anything?
Yes, no?
Jano

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ethz.ch/content/dam/ethz/special-interest/mavt/dynamic-systems-n-control/idsc-dam/Research_DAndrea/Cubli/RevisedManuscript.pdf&ved=2ahUKEwiLjYjutP_oAhVFZM0KHcH5DccQFjADegQIBBAB&usg=AOvVaw3Q75p6hREw01NhghV2_P53
Here is the paper written by the inventors of the cubli.  Sad, to say but the conservation of momentum is kind of the basis for the cubli.  But what the heck, why let facts and science get in the way of your fantasy.

[Jaaanosik (OP)]

All blue arrows without red and green are CMGs at a stable state.
The blue arrows are gyro angular velocities pointing away from each other.
The green arrow is in the direction of the string towards the spaceship reel motor.
Reeling in starts and at the same time top gyro and bottom left gyro will increase the angular acceleration to generate the red counter torque to the green torque disturbance.
The CMGs center of mass will not move anywhere, CMGs will not turn anywhere if the load and counter torque are balanced properly, yet the spaceship will be pulled.
There is nothing wrong with this free body diagram,
Jano

Edit: fixing wrong description of the vectors.

[Jaaanosik (OP)]

Bobolink,
What happens when the Cubli rotates in zero-g?
Will the outside frame rotate 45 degrees as in the video if the frame is not attached to anything?
Yes, no?
Jano

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ethz.ch/content/dam/ethz/special-interest/mavt/dynamic-systems-n-control/idsc-dam/Research_DAndrea/Cubli/RevisedManuscript.pdf&ved=2ahUKEwiLjYjutP_oAhVFZM0KHcH5DccQFjADegQIBBAB&usg=AOvVaw3Q75p6hREw01NhghV2_P53
Here is the paper written by the inventors of the cubli.  Sad, to say but the conservation of momentum is kind of the basis for the cubli.  But what the heck, why let facts and science get in the way of your fantasy.

Bobolink,
What happens to Cubli if it is in zero-g and it is not attached to anything and the jump-up impulse is generated.
Will Cubli move? Yes? No?
It could be argued that the inverted pendulum is more difficult to control then rotations in micro-gravity when Cubli is not restricted by gravity/external forces.
Jano

[Jaaanosik (OP)]

It is obvious that I didn't know about Cubli till I found out about it a few days ago.
If I did know it then I would propose this right at the beginning.
This works because it is proven by Cubli that it can generate the angular acceleration also known as torque by breaking the spinning wheel. The breaking generates bigger torque than spin up. Please, don't get fooled by the fact that Cubli is an inverted pendulum in the video.



The setup is in space, 'zero-g'.
1. A simple gyro start up generates 0 net angular momentum.
Let us assume there is a ring within a ring (stator/rotor - an electric motor) when the angular accelerations/torques start they cancel each other in opposite directions. The rings can have high angular velocities even though the velocities are in the opposite directions.
2. The 3 gyros are configured in a triangle layout and the brakes are applied just to one ring (stator) on all gyros.
The brakes are attached to the outside structure (similar to Cubli), they would not be stopping the second ring.
This would be a jump/torque impulse in the up direction. The gyro assembly starts to move up.
3. A steady torque is applied to turn 3 gyros axles 180 degrees.
The brakes are applied to the second ring (rotor) on all gyros.
This would be the second jump/torque impulse in the up direction. The gyro assembly continues to move up even faster.

The cycle can repeat,
Jano

[Colin2B]

....it can generate the angular acceleration also known as torque

Angular acceleration is NOT known as torque

Please, don't get fooled by the fact that Cubli is an inverted pendulum in the video.

No one is getting confused. This device uses conservation of momentum to do what it does. Don’t confuse rotation, inertia, kinetic energy, potential energy, and angular momentum or you will never understand how this and the falling cat work.

[Jaaanosik (OP)]

....it can generate the angular acceleration also known as torque

Angular acceleration is NOT known as torque

Please, don't get fooled by the fact that Cubli is an inverted pendulum in the video.

No one is getting confused. This device uses conservation of momentum to do what it does. Don’t confuse rotation, inertia, kinetic energy, potential energy, and angular momentum or you will never understand how this and the falling cat work.

Colin,
thank you, I am glad you are paying attention.
I used the term in a 'loose way' to see who is going to pick it up.
Torque is rotational inertia multiplied by the angular acceleration. The relationship is the same as F=ma for the linear systems.




This is how it works.
When the gyro is built as a motor and it will start to rotate by the EM field than mechanical parts will rotate in opposite directions. This angular acceleration combine with the mass of the gyro rings that have rotational inertia gives us the torque.
The torque, angular acceleration and the end result, the angular velocity, are vectors in the same direction along the axle because that is where the center of mass is located for a well centered gyro rings.
Let us assume there is uneven distribution of the rotational inertia, the stator - outside part is a bigger ring compared to rotor - the inner part.
Two things can happen. We can compensate by mass or if we do not compensate with mass then the angular velocity will be different so the net angular momentum is conserved, in opposite directions, it will give us 0.
Either way the result is 0 net angular momentum.
The torques are equal in opposite directions but acceleration and angular velocities might be different based on the solution.
The gyro rings center of mass will not change the position during the acceleration startup.
The gyro is attached to a housing/cage/spaceship and this outside structure will not change its position as well.
When we are in steady state, there is no more angular acceleration, no more torque, even though there are angular velocities of they gyro rings.
Now we decide to brake one gyro ring.
The deceleration will cause the torque impulse, the gyro system moves in the direction of the torque.
If this is a spaceship in the interstellar space then it will move in regards to the stars.
Now we rotate the gyro 180 degrees in regards to the stars.
Is it possible to rotate gyro 180 degrees. Yes, if we assume the symmetrical numbers then gyro will rotate 180 degrees and the spaceship will rotate 180 degrees because of 0 net angular momentum in regards to the stars.
Now we brake the second gyro ring.
The deceleration will cause the torque impulse of the gyro system in the direction of the torque.
This is the same direction as the first impulse in regards to the stars even though it appears the spaceship is going backwards in the spaceship reference frame.

It is time to pause, ... to think, ... to think more, ...
Jano

[Colin2B]

I used the term in a 'loose way' to see who is going to pick it up.

Yeah, yeah, of course you did 

By the way, I'm not paying attention, I just skim sample posts to check spamming etc

Torque is rotational inertia multiplied by the angular acceleration. The relationship is the same as F=ma for the linear systems.

yes, we all know these relationships, but I noticed further back you get very confused about quite a few of them.

We also know how the device works

[Jaaanosik (OP)]

I used the term in a 'loose way' to see who is going to pick it up.

Yeah, yeah, of course you did 

By the way, I'm not paying attention, I just skim sample posts to check spamming etc

Torque is rotational inertia multiplied by the angular acceleration. The relationship is the same as F=ma for the linear systems.

yes, we all know these relationships, but I noticed further back you get very confused about quite a few of them.

We also know how the device works

Colin,
whatever suits you,
Jano

[Jaaanosik (OP)]

Kryptid,
can I ask the following question at the physics forum?

Let us assume an astronaut pushes to the right inside the ISS (the green force vector) and the ISS CMG's compensate with the opposite torque (red arrow).
Is the ISS center for mass going to be disturbed (moved out of position) in the ECI? (Erath Center Inertial reference frame)
Jano

[Colin2B]

Kryptid,
can I ask the following question at the physics forum?

No, keep them here.

[Jaaanosik (OP)]

Kryptid,
can I ask the following question at the physics forum?

No, keep them here.

Colin,
is there anything wrong with the question?
Jano

[Halc]

is there anything wrong with the question?

The problem is more with the asker, not as much with the question.  Yes, keep it here.

The question also has problems. Your description suggests the addition of a force vector to a torque vector, which is adding different things.

The answer to the question is trivial:  The ISS is moving at over 7 km/s relative to 'ECI', so of course it is going to change its position in this frame regardless of what minor pushes the astronauts and gyros decide to perform.  If it were stationary in that frame, it would immediately fall to the ground like any other dropped rock.

Secondly, Earth Center (like any real object I can think of) is always accelerating, and thus does not define an inertial frame.  For thought experiments that take away other objects like the sun, there is an inertial frame defined by the center of gravity of the full system being considered, but you didn't reference that.

[Jaaanosik (OP)]

is there anything wrong with the question?

The problem is more with the asker, not as much with the question.  Yes, keep it here.

The question also has problems. Your description suggests the addition of a force vector to a torque vector, which is adding different things.

The answer to the question is trivial:  The ISS is moving at over 7 km/s relative to 'ECI', so of course it is going to change its position in this frame regardless of what minor pushes the astronauts and gyros decide to perform.  If it were stationary in that frame, it would immediately fall to the ground like any other dropped rock.

Secondly, Earth Center (like any real object I can think of) is always accelerating, and thus does not define an inertial frame.  For thought experiments that take away other objects like the sun, there is an inertial frame defined by the center of gravity of the full system being considered, but you didn't reference that.

Halc,
good points. I wanted to have the question real, I did not describe it in the best way.

Let us make it unrealistic. The ISS is in the intergalactic space, the ISS center of mass is stationary in the reference frame of the surrounding galaxies. The flat space-time as we can get.
The interstellar space-time has too much curvature compared to the intergalactic one.

Let us assume an astronaut pushes to the right inside the ISS (the green force vector) and the ISS CMG's compensate with the opposite torque (red arrow).
Is the ISS center for mass going to be disturbed (moved out of position) in in the reference frame of the surrounding galaxies?
Jano

[Bobolink]

It is time to pause, ... to think, ... to think more, ...

If only you could take your own advice...

By the way, the answer to the OP is still no.

[Halc]

I wanted to have the question real, I did not describe it in the best way.

Let us make it unrealistic. The ISS is in the intergalactic space, the ISS center of mass is stationary in the reference frame of the surrounding galaxies. The flat space-time as we can get.
The interstellar space-time has too much curvature compared to the intergalactic one.

Short story: We're defining a stable environment to keep outside influences from messing with the answer. That's good.

Let us assume an astronaut pushes to the right inside the ISS (the green force vector) and the ISS CMG's compensate with the opposite torque (red arrow).
Is the ISS center for mass going to be disturbed (moved out of position) in in the reference frame of the surrounding galaxies?

Conservation of momentum says it cannot be disturbed, so that's the easy answer. You've been told this in countless posts but you continue to ignore it all. Hence the discussion staying here in lighter-side.

BTW, you're still making the mistake of comparing two vectors of different units.  Force and torque cannot compensate for each other.

Force/momentum: Astronaut pushes with F for a second, sending astronaut one way and the rest of the ISS the other way. Those balance, both in force and momentum. Astronaut hits the far wall and both stop, and the center of mass has moved not a bit.The gyros have no effect on this.

Torque: Astronaut applies torque T for 1 second to the ISS structure and the gyros (which can be anywhere) compensate.  Assuming the thing has zero angular momentum before (you didn't specify that), then the angular momentum of the astronaut relative to the system is exactly compensated by the opposite angular momentum now acquired by the gyros, until he hits the far wall and the gyros are forced to give it back. At no point was there a nonzero total angular momentum.

[Jaaanosik (OP)]

I wanted to have the question real, I did not describe it in the best way.

Let us make it unrealistic. The ISS is in the intergalactic space, the ISS center of mass is stationary in the reference frame of the surrounding galaxies. The flat space-time as we can get.
The interstellar space-time has too much curvature compared to the intergalactic one.

Short story: We're defining a stable environment to keep outside influences from messing with the answer. That's good.

Let us assume an astronaut pushes to the right inside the ISS (the green force vector) and the ISS CMG's compensate with the opposite torque (red arrow).
Is the ISS center for mass going to be disturbed (moved out of position) in in the reference frame of the surrounding galaxies?

Conservation of momentum says it cannot be disturbed, so that's the easy answer. You've been told this in countless posts but you continue to ignore it all. Hence the discussion staying here in lighter-side.

BTW, you're still making the mistake of comparing two vectors of different units.  Force and torque cannot compensate for each other.

Force/momentum: Astronaut pushes with F for a second, sending astronaut one way and the rest of the ISS the other way. Those balance, both in force and momentum. Astronaut hits the far wall and both stop, and the center of mass has moved not a bit.The gyros have no effect on this.

Torque: Astronaut applies torque T for 1 second to the ISS structure and the gyros (which can be anywhere) compensate.  Assuming the thing has zero angular momentum before (you didn't specify that), then the angular momentum of the astronaut relative to the system is exactly compensated by the opposite angular momentum now acquired by the gyros, until he hits the far wall and the gyros are forced to give it back. At no point was there a nonzero total angular momentum.

Halc,
there are two scenarios that need to be analyzed.

1. With the CMGs   NOT RUNNING/ACTUATED
2. With the CMGs   RUNNING/ACTUATED

Here is the video:

1. is shown at 50s of the video
2. is shown at 56s of the video

1. The center of CD players (ISS) mass moves on a straight line and the CD players rotate when CD players are OFF (CDs inside do not rotate).
2. The center of CD players (ISS) mass does not move on a straight line and the CD players do not rotate, they just wobble when CD players are ON (CDs inside rotate).

Do you see the difference?
This is what is at the core of the problem I am trying to point out,
Jano

[Jaaanosik (OP)]

...
BTW, you're still making the mistake of comparing two vectors of different units.  Force and torque cannot compensate for each other.
...

Halc, is torque a force vector?
This is a little bit tricky question, because of the well balanced accelerating wheel.
What is a torque for the accelerating wheel?
Jano

[Halc]

Halc,
there are two scenarios that need to be analyzed.

1. With the CMGs   NOT RUNNING/ACTUATED
2. With the CMGs   RUNNING/ACTUATED

OK, but 3 CD players taped together is not a CMG.  Nothing in there attempts to stop its own motion. The object has entirely passive behavior.

1. The center of CD players (ISS) mass moves on a straight line and the CD players rotate when CD players are OFF (CDs inside do not rotate).
2. The center of CD players (ISS) mass does not move on a straight line and the CD players do not rotate, they just wobble when CD players are ON (CDs inside rotate).

Do you see the difference?
This is what is at the core of the problem I am trying to point out,

Fine, I see the difference.  The guy applies a little torque to the running object and that changes its angular momentum, causing it to wobble. Same thing with a toy top on its side, which precesses due to torque applied to it.  The top orientation never rotates in the direction the torque is applied.

Halc, is torque a force vector?

No. Force is measured in Newtons, torque in Newton-meters. They're different animals.
Your red torque vector should A) come from the center of mass, not the point of force application, and B) point towards the point of view, not to the left. Torque vectors are along the axis of rotation.

This is a little bit tricky question, because of the well balanced accelerating wheel.
What is a torque for the accelerating wheel?

It can be expressed as tangential force component multiplied by perpendicular offset from the center of rotation.

[Jaaanosik (OP)]

Halc,
here is a wheel, top view and the side view:



The wheel and the brakes calipers have friction less bearings.
The wheel and the calipers can move up along the axles without any obstruction.
The setup is here on the Earth, the axles point up, the wheel is horizontal to the ground.
The wheel is rotating clock wise, omega points down.
Let us apply an instantaneous breaking to the wheel.
The angular acceleration (actually deceleration) is in upward direction.
Is the wheel going to jump up due to the angular acceleration/deceleration, assuming angular acceleration is bigger than gravitational acceleration?
Jano

[Halc]

Is the wheel going to jump up due to the angular acceleration/deceleration, assuming angular acceleration is bigger than gravitational acceleration?

You know it will not.
The fact that you got the α and ω vectors correct suggests you're not completely uneducated, and yet you ask a question like that. Now why is that?

For the third time, you are adding vectors of different units (bold above), meaning you're ignoring everything I say and intend to continue to do so. Hence I see no reason to continue this troll discussion.