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[ta0]

As I continue to digest it, would love to know which directions the flywheel and shell are actually spinning before and after the the main transitions in behavior. Don't trust the directions I'm seeing in the video, and  and especially the reversals, as some could easily be frame-rate artifacts.

The flywheel never reverses and you can just observe with the naked eye the reversals of the shell. But when I have time I could try to measure again the flywheel speed. I believe the motor must be changing speeds at the beginning. I don't know why, as I wait until it appears to have reached the final speed before I let it go. 

the flywheel spins counterclockwise. 
When you release the top, by the time, the motor seems to run faster, and the shell spins clockwise, faster and faster.
This could be explained as the flywheel pushing the shell backwards as it accelerates.

One strange thing is that, once the motor goes at a relatively constant speed, the shell seems to maintain its speed, instead of gradually slowing down, as I would expect, because of the tip friction and also the air drag on the shell. Maybe the tip friction is very low because of vibration ?  Or there is something mysterious which continues to push the top clockwise ?  It could be interesting to know if the shell maintains its speed in a longer lapse of time, with motor at constant speed, maybe 10 minutes.

This part I don't find too mysterious. The flywheel would lose speed because of friction if it wasn't because of the motor pushing on it. And the motor pushes with the same force against the shell. If the shell didn't see any air drag (I think it's much bigger than the tip friction) it would eventually acquire the same momentum but backwards, canceling the flywheel rotational momentum and the top would fall. But because of the air drag it never reaches that speed.

Another mistery is that the top, in the beginning, rises, in spite of the rolling resistance in the wrong direction. 
In fact, if I've got this right, the flywheel and the shell spin in the opposite directions.
The flywheel seems to drive the gyroscopic motion, and not the shell, because the top precesses counterclockwise.
As for what I understand, the top shouldn't rise in these conditions, my top doesn't, but the Hart top does.

This I also find mysterious.

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I remember vaguely that there was another motorized top with a similar behaviour we discussed about, it had an asymmetrical flywheel, so there was something particular.  If the flywheel is asymmetrical, it could cause vibration.  Maybe this is a clue.

Actually, that is from the Hart patent, as discussed here:
https://www.ta0.com/forum/index.php/topic,1383.msg55486.html#msg55486
This might be the biggest mystery of all of this!

[Iacopo]

This part I don't find too mysterious. The flywheel would lose speed because of friction if it wasn't because of the motor pushing on it. And the motor pushes with the same force against the shell. If the shell didn't see any air drag (I think it's much bigger than the tip friction) it would eventually acquire the same momentum but backwards, canceling the flywheel rotational momentum and the top would fall. But because of the air drag it never reaches that speed.

This is a very good explanation.  I agree with it.

Actually, that is from the Hart patent, as discussed here:
https://www.ta0.com/forum/index.php/topic,1383.msg55486.html#msg55486

I just realized that when the motor is on, as the shell (with the tip) rotates opposite to the flywheel, the walking of the tip would increase the lean, not make the top stand up!  Indeed, in mine when the switch is on, it cannot recover from any appreciable lean: it will just precess in place like a gyro if the shell is spinning slowly or fall if it's spinning fast (I'd like to get one in better condition to confirm this). On the other hand, with the motor off it can do some spectacular recoveries.

Perhaps the vibrations due to the unbalance of the flywheel help delay the effect of tip walking.

I see we observed the same things. My motorized top too behaves like so.
I believe that the vibration is the cause of the otherwise impossible rise, I have a vague idea how it could work, but I have to think a bit more about its kinematics, then I will add something here.

[Iacopo]

I think I found something.

In the first drawing there is the tip of a top spinning, (the top is very tilted for more clarity), the top spins clockwise and the top moves to the left.
This is the normal situation.



Below instead we have the tip of the Hart top. 
The tip spins clockwise, as the tip above.  In the meanwhile it vibrates.
Vibration is due to the center of mass of the flywheel and the center of mass of the shell misaligned and spinning around the center of mass of the whole top.
So the vibration of the shell is a tiny and rapid circular motion in the same direction of the flywheel, (counterclockwise).
If the speed and intensity of the vibration are important enough relatively to the spin speed of the shell, it happens that, in the instants when the tip touches the dish, the contact point of the tip will be moving towards the left instead of towards the right, and consequently the tip will be pushed towards the right.



In fact, looking at your second video of the Hart top at 1:30, it can be seen that the top walks in the opposite direction than it should if we just consider the spin direction of the shell. The vibration reverses the direction of the push of the tip on the dish.

[ta0]

That's a novel and interesting theory.
The axis of the top in reality is almost vertical, so it's not obvious to me that the flywheel unbalance will make it jump like that.

In fact, looking at your second video of the Hart top at 1:30, it can be seen that the top walks in the opposite direction than it should if we just consider the spin direction of the shell.

That's a good observation. More filming and experiments are required.

PS: I want to make my green Hart spin as well as my red one. I wonder if I should let it fall and break a little so it's more unbalanced 

[Iacopo]

If you observe the top spinning in a bit tilted position and see that the backwards walking behaviour is consistent and not random, I would say that this can only be caused by the vibration.  I agree that the vibration of the tip on the dish becomes weaker and weaker as the top rises vertically, but if this is sufficient for cancelling the forwards walking of the top, this could at least partly explain the stability of the top.

[Jeremy McCreary]

Another electric top using the motor shaft itself as the tip...

https://youtu.be/migvUpWKB0U

[ta0]

Another electric top using the motor shaft itself as the tip...

That should work the same as the Infini-Top.
Very simple construction. But with the tip of the rotor touching the ground, it's less mysterious as its rotation will accelerate the precession and make it stand up. Air drag should be very important and my guess is that in vacuum it wouldn't work.
I don't believe this top needs any vibration to work, but the way it was built some unbalance is automatically built in, so we cannot be sure 

[Jeremy McCreary]

Another electric top using the motor shaft itself as the tip...

That should work the same as the Infini-Top.
Very simple construction. But with the tip of the rotor touching the ground, it's less mysterious as its rotation will accelerate the precession and make it stand up. Air drag should be very important and my guess is that in vacuum it wouldn't work.
I don't believe this top needs any vibration to work, but the way it was built some unbalance is automatically built in, so we cannot be sure 

Wondering how different these really are from Iacopo's, mechanically speaking?

His effectively spins on its motor casing, while these 2 spin on their shafts. An electric motor just generates relative torque between casing and shaft. If you hold it by the shaft, the casing spins.

[ta0]

Wondering how different these really are from Iacopo's, mechanically speaking?
His effectively spins on its motor casing, while these 2 spin on their shafts. An electric motor just generates relative torque between casing and shaft. If you hold it by the shaft, the casing spins.

The standard explanation of why free tops with round tips spinning on a surface rise is because the friction of the tip accelerates the precession. Because of air drag, in all these electric tops the inside rotor rotates faster than the shell and determines the net momentum of the top. It the tip directly connects to the motor rotor, the friction with the surface will be in the same direction as a pegtop. But if the tip is part of the shell, it will be in the opposite direction.

[Iacopo]

Wondering how different these really are from Iacopo's, mechanically speaking?

In the mine I cancelled the air drag by enclosing the flywheel so there is no torque on the tip and the tip does not spin.

In the video you posted the air drag brakes the case while the motor supposedly makes the tip to spin in opposite direction, so practically the air drag would maintain the tip spinning. 

Anyway it is not clear what it is happening in the video exactly; theorically if the tip spins in the opposite direction of that of the top, the top should be unstable.
My top in fact is unstable.
But I am not sure that the tip spins in opposite direction in the video.

In fact the tip of the blue top walks clockwise, suggesting that it is spinning clockwise.
The precession is clockwise, so it seems that the top too is spinning clockwise.
If so, the top is behaving like a normal top.  The top should gradually slow down and topple down. 
If so, the motor is not keeping the top spinning.  Difficult to judge because we see only a few seconds of the top spinning.
 

[ta0]

I now realize that the Infini-Top is a third case as the inner part of the motor (rotor) is attached with a gear to the outer shell of the top, while the motor casing spins in between.





As you can see, the motor is eccentric and because of the gear the shell will rotate at a lower speed (8/30) in the opposite direction than the rotor. Due also to the gear, the full motor will orbit around the axis of the top, so the black casing will spin in the opposite direction to the outer bluish shell.
Here is a video spinning without the lower part of the shell.

https://www.youtube.com/watch?v=1k9fckLuZ5k

[Jeremy McCreary]

Anyway it is not clear what it is happening in the video exactly...

Yes, more questions than answers here. Wish we saw how the top was started, how long it stayed up, and how it fell. Guessing that the rough concrete floor provided a good bit of "tip resistance" (total braking torque due all contact processes involved). Enough to eliminate slip at the floor contact in the steady state long after starting, or at all times (as in your motorized top)? No way to know.

...theorically if the tip spins in the opposite direction of that of the top, the top should be unstable.

There are important shades of gray here. A coax top with oppositely spinning coaxial components will still be stable if its net angular momentum exceeds a critical value. And that depends on the speed, mass, AMI, central TMI, and CM height of each component.

In fact the tip of the blue top walks clockwise, suggesting that it is spinning clockwise.
The precession is clockwise, so it seems that the top too is spinning clockwise.

Valuable observations, but still not quite sure what to make of them. As I think you're suggesting, the motor in the "Electric Spinning Top" could serve more as a built-in starter than as a long-term counter to spin decay. Seeing how it was started would be helpful.

[Jeremy McCreary]

I now realize that the Infini-Top is a third case as the inner part of the motor (rotor) is attached with a gear to the outer shell of the top, while the motor casing spins in between.

Thanks for these valuable data points. Studied the photos and video and your comments but still have some questions...

Q1: How does the metal tip connect to the rest of the Infini-Top? Fixed to the round black chassis fixed to the motor casing?

Q2: Same question for the triangular black part with the large white nylon gear at its center? Is the big gear keyed to the upper blue shell half, or do they connect through a frictional pivot bearing with potential slip? And what other connections to the black part itself -- besides the gears?

[Iacopo]

In fact the tip of the blue top walks clockwise, suggesting that it is spinning clockwise.
The precession is clockwise, so it seems that the top too is spinning clockwise.

Valuable observations, but still not quite sure what to make of them.

If tip and top spin in the same direction, I believe that it is behaving like a normal spinning top, or like the toupie lumineuse spinning counterclockwise:
the motor can't keep the top spinning so the top slows down and topples down. Why to have a motor if it doesn't work ?
Unless vibration changes something, the blue top vibrates a lot in fact.  But the top seems rough, we don't know if this is a real and working motorized top.

[Iacopo]

I now realize that the Infini-Top is a third case as the inner part of the motor (rotor) is attached with a gear to the outer shell of the top, while the motor casing spins in between.

The Infini-Top precesses clockwise or counterclockwise ?