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Author Topic: "Limbo" Gyro Top  (Read 14178 times)

Iacopo

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Re: "Limbo" Gyro Top
« Reply #45 on: May 16, 2020, 08:48:34 AM »

I made a short video to make it a bit clearer than the drawing.

The ball represents the vibrating tip of the top.
Imagine the top very tilted and leaned towards the inside of the screen.
The black arrow at the beginning of the video is the vibration of the axis of the shell/tip.
The shell/tip is vibrating but it is not spinning.

When the tip touches the ground it becomes pushed towards the left, so the top walks towards the left, (blue arrow).

At the same time, the vibrating tip touching the ground makes the shell/tip spin, (green arrow).

Note that in a normal spinning top, the spin in the direction of the green arrow would make the top to go towards the right, not the left;
the vibration "reverses" the direction of the walking of the top.
"Reverses" is not very correct probably, because the walk is not generated by the rolling tip;
the vibration generates both the walk and the spin.

https://www.youtube.com/watch?v=gbUicXQkcJU


This is still valid also for little angles of tilting of the top. 
Only when the top is vertical, the effects of the vibration on the shell/tip would be neutral.
« Last Edit: May 16, 2020, 08:55:38 AM by Iacopo »
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ta0

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Re: "Limbo" Gyro Top
« Reply #46 on: May 16, 2020, 09:19:24 AM »

Also still puzzled by the eccentric gyro rotor. At the claimed 10,000 RPM, the resulting vibration could well be negligible. So the rotor shape could have more to do with the motor design than the top control strategy per se. Is that what you meant by "half-armature"?
Yes, that's what I meant. Sorry, armature is the wrong term in this case because this is a DC motor.
The rendering of the motor on that video is very schematic. If it's in fact a half rotor, it's for sure a cell phone vibrator motor.

This is how the vibration could reverse the walk direction:
I already posted this explanation but after some more thinking I am understanding better how it should work so I have updated this explanation.
In fact THE VIBRATION CAUSES BOTH THE BACKWARDS WALKING AND THE SPIN OF THE SHELL/TIP.
Yours is an intriguing and original theory. Intuitively, I'm not convinced it would be enough to straighten the top, but I don't have another theory at this time.
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #47 on: May 16, 2020, 10:07:23 AM »

I don't think resonance is necessary.  Resonance happens between two different vibrations, here instead we have one vibration, which seems what is needed.

The vast engineering literature on vibration in rotating machinery looks at vibration and resonance very differently than you do. The literature's viewpoint applies in this situation, and I just can't reconcile it with your statement above. The.eccentric rotor resonance I spoke of is primarily an inertial phenomenon having nothing to do with interactions between coexisting vibrations.

But no matter. I'd be astounded if the asymmetric Limbo rotor ran anywhere near its resonanrt speed in routine operation.

Bottom line: We'll never resolve these issues without careful experiments on a real Limbo. I'm not ready to assume that its strategy for beating spin decay is identical to that of the Hart top.

PS: Unfortunately, production's on hold now due to COVID-related motor procurement issues...

https://limbo-igg.backerkit.com/hosted_preorders/project_updates#updates
« Last Edit: May 16, 2020, 11:38:55 AM by Jeremy McCreary »
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Art is how we decorate space, music is how we decorate time ... and with spinning tops, we decorate both.
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Iacopo

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Re: "Limbo" Gyro Top
« Reply #48 on: May 16, 2020, 12:13:05 PM »

Yours is an intriguing and original theory. Intuitively, I'm not convinced it would be enough to straighten the top, but I don't have another theory at this time.

I tried to imbalance the flywheel of my motorized top to see how it behaves.
I have not been able to make the top rise.  Whatever weight I add to the side of the flywheel, when I release the top, the top sinks down, as when there is not added weight.  So I am not so sure anymore. 
It is something interesting to investigate, anyway.
---------------------------
I just ordered the Toupie Lumineuse. 
« Last Edit: May 16, 2020, 01:51:37 PM by Iacopo »
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ta0

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Re: "Limbo" Gyro Top
« Reply #49 on: May 18, 2020, 11:45:42 AM »

PS: Unfortunately, production's on hold now due to COVID-related motor procurement issues...
I think it's more serious than that. Estimated delivery for the first Kickstarter project was December 2018! I'm glad I did not pledge. They are being called scammers on the Kickstarter comments . . .
The latest update is that it works with some motors and not others and that they have devised a test for the Chinese motor manufacturer to use. It seems to me that they don't understand how it really works.

I just ordered the Toupie Lumineuse.

Good move! Everyone should have one of those.

https://www.youtube.com/watch?v=7DlEWEwe-9M

I look forward to your experiments.
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #50 on: May 18, 2020, 12:11:29 PM »

I just ordered the Toupie Lumineuse.
Good move! Everyone should have one of those.... I look forward to your experiments.

OK, OK, I'll order one, too. From Grand Illusions?

Iacopo's our best experimentalist. I'm also eager to see his observations.
« Last Edit: May 18, 2020, 01:14:03 PM by Jeremy McCreary »
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #51 on: May 18, 2020, 01:12:59 PM »

Against my better judgment, went to Grand Illusions to order a Toupie Lumineuse. And of course ordered 5 3 more tops, including a deceptively simple mechanical top I hadn't seen...

https://www.grand-illusions.com/spin-top-c2x27904612
(Have to watch the video to see the appeal.)

Really disappointed that the Vortex Dome was out of stock, but probably better for my marriage -- especially now that we're home together 24x7.

Feel good about supporting Tim and his videos, though.
« Last Edit: May 18, 2020, 07:31:38 PM by Jeremy McCreary »
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ta0

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Re: "Limbo" Gyro Top
« Reply #52 on: May 18, 2020, 01:34:40 PM »

Against my better judgment, went to Grand Illusions to order a Toupie Lumineuse. And of course ordered 5 more tops, including a deceptively simple mechanical top I hadn't seen...

https://www.grand-illusions.com/spin-top-c2x27904612
(Have to watch the video to see the appeal.)

Really disappointed that the Vortex Dome was out of stock, but probably better for my marriage -- especially now that we're home together 24x7.

Feel good about supporting Tim and his videos, though.
Ha! You won't be able to hide the arrival of the package from your wife!

You had actually seen that Naef spherical top before, as we discussed it here: link:D But that's one I haven't got.
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #53 on: May 18, 2020, 03:10:27 PM »

You had actually seen that Naef spherical top before, as we discussed it here...

Don't forget to enjoy your memory while you can.
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ta0

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Re: "Limbo" Gyro Top
« Reply #54 on: May 18, 2020, 05:55:54 PM »

Don't forget to enjoy your memory while you can.
I have been caught before forgetting something I had already posted about . . .  ::)

I'm curious what other tops you got. I'm guessing the non toppling top (taorenado) and the Pirouetto.
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #55 on: May 18, 2020, 07:51:11 PM »

I'm curious what other tops you got. I'm guessing the non toppling top (taorenado) and the Pirouetto.

Well, another memory lapse: At one point, had 8 tops in my cart, then 6, and at the last minute, pared that down to just 4 total.

Taorenado, definitely. Also, the small Al tippe top, as none of mine work well. And the motorized and self-splitting tops already mentioned.

For next time, Pirouetto, "Spin on Finger" recessed-tip bell top, and above all, the Vortex Dome if back in stock. (The only thing better than spin is spin + fluid dynamics made visible.)
« Last Edit: May 18, 2020, 08:25:13 PM by Jeremy McCreary »
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #56 on: May 19, 2020, 12:58:11 PM »

Wow, if DHL really delivers my Grand Illusions tops on 5/21 as claimed, that'll be just 3 days from ordering. And that's with standard shipping!

I was expecting at least a week from the UK.
« Last Edit: May 19, 2020, 01:52:17 PM by Jeremy McCreary »
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Iacopo

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Re: "Limbo" Gyro Top
« Reply #57 on: May 30, 2020, 01:09:02 PM »

I received the mine !   :)



Well, it does not work as I supposed.
And I don't understand yet how it works exactly.  There is vibration in the top and I still believe that vibration makes it work, but I don't understand in which way.

Some observations:

- The top does not walk backwards as I believed, at the countrary, it consistently walk in the direction it should, given the spin direction.
So the vibration does not reverse the walk direction.  At least not in this top.  But I suppose that all the tops of this kind behave in a similar way.

- When the top is spun, the motor starts going, and, slowly, the shell/tip spins faster and faster, in the same direction it was spun, (clockwise), until reaching a permanent stable speed.  It seems that the top could spin until there is electricity.

- The top does not work counterclockwise.  If spun counterclockwise, the motor starts going normally, but the top vibrates a lot, moves irregularly, never accelerates, decelerates instead, until stopping, in no more than maybe 30 seconds. At times, the top walks backwards; there is counterclockwise spin and counterclockwise precession, but the stem is tilted towards the outside of the precession circle, so there is backwards walking, certainly due to the vibration.

- The motor changes speed by the time, it goes slowly if the top spins slowly, and it goes faster and faster as the top accelerates.  It seems like the motor tries to synchronize its speed with that of the top, in some way.

- Spin direction and precession direction are the same. So maybe the top rises like normal tops.  Sometimes, not always, when it is very tilted, the top vibrates a lot, then it rises, maybe the vibration helps the rise.

- The vibrating motor is little and placed very near to the tip.
« Last Edit: May 30, 2020, 01:55:40 PM by Iacopo »
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #58 on: May 30, 2020, 03:19:40 PM »

I received the mine !   :)

Ditto, and I've seen exactly the same behaviors. Who knew I was ordering a toy with a split personality? Calm, collected, and competent clockwise. But spin it the other way, and it totally loses its cool. Which may be even more entertaining. See now why ta0 recommended it so highly.

The top even has a 3rd side -- as a fine reverse engineering puzzle. Looks to me like it might be a close mechanical cousin to the Limbo. Also looks like we won't be getting our hands on a  Limbo anytime soon.

So, I'm compiling a list of all the solid observations we now have on both tops to see what the total body of evidence has to tell us. Including the Limbo video evidence. Just the facts, ma'am.

Think they can fool iTopSpin, do they?




« Last Edit: May 30, 2020, 03:29:27 PM by Jeremy McCreary »
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Jeremy McCreary

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Re: "Limbo" Gyro Top
« Reply #59 on: May 30, 2020, 06:41:26 PM »

Meanwhile, keep a close ear on the top as you spin it on a glass platter or other resonant surface. Listen especially to how it responds when you mess with it -- either directly or by moving the platter.

When undisturbed, you hear a steady high-freqency internal hum/buzz with no discernable a slight vibration against the glass or in the stem. Sounds like the motor inside is running smoothly at constant speed.

The real vibration comes when you force the top to tilt or slow its spin in any way, or when you start it counterclockwise-- all things an onboard accelerometer could easily detect. You can hear a loud vibration against the glass and feel it with your fingers on the stem.

During the vibratory responses, the internal hum/buzz gets louder and lower in frequency, as if the internal motor were slowing down and perhaps straining to respond.

All of this could come from a single eccentric speed-controlled motor just like the one shown and clearly described for the Limbo. The Limbo also has an accelerometer. Tim says that the manufacturer of our top says that it uses a phone vibrator motor. And the Limbo updates seem to imply the same thing.

Question is, is the clearly variable vibration a weapon against spin decay, a tolerated side-effect of reduced motor speed for whatever reason, or some of both?

Can't yet decide. But I do know that large high-speed machines usually have to contend with some residual mass eccentricity. And that many have to be nursed past vibration-inducing resonances on the way to and from operating speed. Nothing beneficial about the vibration there.
« Last Edit: June 01, 2020, 08:33:59 AM by Jeremy McCreary »
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