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[Jeremy McCreary]

The shape-shifters of science fiction can be pretty scary. And the last thing you'd want would be a shape-shifting partner who could take moody to a whole new level.



But these folding centrifugal shape-shifter tops are just pure fun. Spin times are severely limited by air resistance and lack of rigity, and I usually don't tolerate this much low-speed wobble. But way too much play value here to scrap.

Centrifugal tops are surprisingly good at self-balancing, but too much floppiness can lead to wobble-inducing structural oscillations worst at low speeds. I believe we're seeing some of that here.

At rest, the tops can be posed in many different 3D forms. At speed, they unfurl under centrifugal force to form illusory surfaces and colors via the persistence of vision. These optical effects are best by far in person, but stills taken at speed capture some of the flavor. Video only hints at these illusions but introduces some interesting frame-rate and rolling-shutter artifacts.

[Iacopo]

Centrifugal tops are surprisingly good at self-balancing...

In some way they might self-balance like the tops with the balls or the water inside...
Something to think about.

[ta0]

Nice organic-looking tops.

I feel centrifugal shape-shifting tops haven't been exploited as they could commercially. I only know a few examples. The most successful, and a favorite of mine and others, is the Sakura top we have already discussed:

[Jeremy McCreary]

Centrifugal tops are surprisingly good at self-balancing...

In some way they might self-balance like the tops with the balls or the water inside...
Something to think about.

Self-balancing in tops is a very interesting process. In otherwise rigid tops containing loose balls or other granular materials like small LEGO parts, the "particles" will space themselves evenly around the periphery of the container — even when there aren't enough particles to be in direct contact with each other at equilibrium. Very strange — and not full explainable with centrifugal force and direct particle-particle interactions.

I've experimented with quite a few such tops. Structural oscillations or vibrations appear to play an important role, too.

The same may be true of tops like the shape-shifters with independently moving swing-arms. But in these tops, my sense is that structural oscillations can also interfere with self-balancing. Very complicated stuff.

[Jeremy McCreary]

Nice organic-looking tops.

I feel centrifugal shape-shifting tops haven't been exploited as they could commercially. I only know a few examples. The most successful, and a favorite of mine and others, is the Sakura top we have already discussed:

The Sakura is a favorite of mine, too. Agree, much more could be done with centrifugal tops. I've made dozens of different kinds with LEGO and am still just getting started.

[Iacopo]

Very strange — and not full explainable with centrifugal force and direct particle-particle interactions.

I have an idea about it, related to the your about unbalance and "whirling":
when the unbalanced top spins in counter-phase, staying tilted towards the light side, if there are loose balls inside, the balls will go towards the light side, because that side is protruding outwards more than the heavy side, and the centrifugal force will push the balls there.
But, as the balls go in the light side, that side will become the heavy side, so the top will tilt towards the opposite side now. 
There should be a feed back relationship between the direction of tilting of the top and the position of the balls, and the balls should stop rolling only when the top becomes balanced.

Something similar could happen in your shape-shifting tops; instead of the rolling balls, there are tilting elements that could tilt less or more depending on their distance from the spin axis and the related amount of centrifugal force;  the element that tilts more would extend more outwards, making that side of the top heavier, so the top can self balance, (but only if the top is spinning in counter-phase, otherwise the moving parts could only worsen the unbalance).

[ortwin]

For the balls the interact mainly with the rim of a round top, I still think my explanation in an older thread is not too bad.

[Jeremy McCreary]

Very strange — and not full explainable with centrifugal force and direct particle-particle interactions.

I have an idea about it, related to the your about unbalance and "whirling":
when the unbalanced top spins in counter-phase, staying tilted towards the light side, if there are loose balls inside, the balls will go towards the light side, because that side is protruding outwards more than the heavy side, and the centrifugal force will push the balls there.
But, as the balls go in the light side, that side will become the heavy side, so the top will tilt towards the opposite side now. 
There should be a feed back relationship between the direction of tilting of the top and the position of the balls, and the balls should stop rolling only when the top becomes balanced.

Something similar could happen in your shape-shifting tops; instead of the rolling balls, there are tilting elements that could tilt less or more depending on their distance from the spin axis and the related amount of centrifugal force;  the element that tilts more would extend more outwards, making that side of the top heavier, so the top can self balance, (but only if the top is spinning in counter-phase, otherwise the moving parts could only worsen the unbalance).

I like the idea that whirl with a 180° phase angle could couple the motions of balls that were otherwise too sparse to interact much with each other directly.

Makes me wonder how many of my centrifugal tops actually operate in the 180° phase regime. In industrial rotor dynamics, you have to spin up through the 0° phase regime and the first (lowest) resonant speed to get there. Spinning up or down through that first resonance isn't subtle and has to be done very carefully, as the whirl amplitude can get out of hand and damage the machine.

Don't recall passing through resonances with my centrifugal tops. But they're spun up by the stem, either by hand or with a starter, and that stem support could potentially mask or damp out any whirl present during spin-up.

Very complicated stuff, as damping also affects resonant speeds directly. That means that first resonant speeds in a finger top are likely different in spin-up and spin-down. Will have to think about this more

[Jeremy McCreary]

For comparison, below is a much larger blacklight swing-arm centrifugal top I made 7 years ago. Start at 1:09 for a good look at the centrifugal shaping in action.



One of my trippier creations — especially in person. The 8 swing-arms are indepently configurable for both shape and color at speed. Two of my favorite configurations come at 7:15 and 13:20.

[Iacopo]

Don't recall passing through resonances with my centrifugal tops.

In many tops I don't see resonance, and when I see it, it is not evident nor spectacular;
did you see something that could be resonance in your other tops ?
Generally, as far as I could observe, when there is resonance, it happens towards the end of the spin, when the top is already wobbling by itself, before to topple, so the wobble hides a bit the resonance. 
I could see more evident resonances in spindulums, than in spinning tops.
I thought to make a spinning top with the best proportions for to make the resonance the most evident possible.. but I never made it..