Extracting energy from gyroscope precession

[Precision99]

No, leaning back should not cause swinging unless there is friction.

I disagree. But it is hard to argue against such hand-waving statements that give no reasons or reasoning as to why the writer believes the statement to be true. Do you believe there is some fundamental reason why leaning back should not cause swinging? Do you believe there is a fundamental reason why swinging cannot be started, regardless of what the person does, without friction being involved? And if you believe there is such a fundamental reason, then you need to explain what that reason is. In other words, you need to justify your statement, otherwise you are just pulling your statement clean out of thin air.

For myself, I have the great advantage of owning a swing, and can thus report as observed fact that leaning back as I have described results in a small but entirely unambiguous swinging motion. Maybe I should get a mate to video this, and post the video.

And on top of that, I see no fundamental reason why this cannot happen (with a swing, but not with a frictionless rotatable office chair), and from an analysis of the forces and torques, I would broadly expect it to happen, though I admit that the exact details of what happens dynamically when you lean back are very complex.

If the chains were rigid rods, do you still believe that leaning back should not cause swinging?

And what does "should not" even mean? Does it mean that, off the top of your head, you reckon it "should not" happen but you are not really sure, or do you mean "cannot", which would mean you have some firm basis in physics for making your statement?

As matters stand, your unevidenced statement has little if any value.

 

[Precision99]

If the chains were rigid rods, do you still believe that leaning back should not cause swinging?

I set up a small experiment simulating a rigid rod swing. A single 6mm dia brass rod, 500 mm long was suspended from a thin thread - that is the rigid swing rod. The human upper torso is a 150 mm length of 10mm dia steel rod. The lower end of the "torso" can pivot about the lower end of the brass rod, except this pivot is a short length of 1 mm thick copper wire, which provides some damping by way of some resistance to being bent. The torso starts off sitting upright, ie, almost vertical, with a short length of cotton from the top of the torso rod to the brass bar, to initially stop the torso from "leaning back". In this "sitting up" position, the swing is made to hang perfectly still, no oscillation or swinging motion at all.

Then a match flame is used to burn through the cotton, and the torso "leans back", at a controlled rate of fall, due to the bending resistance of the thick copper wire pivot at the bottom of the torso. The torso finally comes to rest about 30 degrees below horizontal.

So the burning question is, after the torso has leaned back and stays leaned back, is the swing swinging or not?

Anyone care to predict the outcome?

 

[Precision99]

I set up a small experiment simulating a rigid rod swing. A single 6mm dia brass rod, 500 mm long was suspended from a thin thread - that is the rigid swing rod. The human upper torso is a 150 mm length of 10mm dia steel rod. The lower end of the "torso" can pivot about the lower end of the brass rod, except this pivot is a short length of 1 mm thick copper wire, which provides some damping by way of some resistance to being bent. The torso starts off sitting upright, ie, almost vertical, with a short length of cotton from the top of the torso rod to the brass bar, to initially stop the torso from "leaning back". In this "sitting up" position, the swing is made to hang perfectly still, no oscillation or swinging motion at all.

Then a match flame is used to burn through the cotton, and the torso "leans back", at a controlled rate of fall, due to the bending resistance of the thick copper wire pivot at the bottom of the torso. The torso finally comes to rest about 30 degrees below horizontal.

So the burning question is, after the torso has leaned back and stays leaned back, is the swing swinging or not?

Anyone care to predict the outcome?

And the result, is that after the torso has leaned back and stays leaned back, the swing is swinging with an amplitude of about +- 15 mm. I repeated the experiment half a dozen times and the result was always the same.

This is in agreement with experiments with my back yard swing. Starting off stationary with no swinging, when I simply lean back and stay leaned back, the swing is then found to be swinging with an amplitude of about +- 80 mm. And from there, it's a piece of cake to pump it to larger and larger amplitude. No laws or principles of physics have been violated, and friction with the external environment is not involved. Is anyone still not convinced?

 

[BradtheRad]

I believe your observation which demonstrates that moving the center of gravity starts a swinging motion. The apparatus must obey the force of gravity so its greatest mass is closest to earth.

 

[Precision99]

I believe your observation which demonstrates that moving the center of gravity starts a swinging motion. The apparatus must obey the force of gravity so its greatest mass is closest to earth.

Well at least someone agrees with me .....