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[Iacopo]

... coaxial tops with multiple independently spinning rotors...

I don't figure out what they are exactly...  did you make them with Lego ?

[Jeremy McCreary]

... coaxial tops with multiple independently spinning rotors...

I don't figure out what they are exactly...  did you make them with Lego ?

Sorry, should've explained "coaxial top". For lack of a better term, that's what I call a top with independently spinning coaxial components. Angular momentum then "flows" from faster- to slower-spinning components via bearing frictions. This gives rise to some interesting behaviors and unconventional play modes but isn't a recipe for long spin times.

Got the idea from a combo of playing around with LEGO tops and dual-spin spacecraft. But it's surely been used in tops many times before.

A whizzzer is a coaxial top with a flywheel rotating freely inside a coaxial outer shell. So is a classic toy-store gyroscope — basically a flywheel within an independently rotating coaxial cage.

Wish I had a video to show. Such tops are far outside your usual design space, but I know you'd make some amazing coaxial and centrifugal tops if so inclined.

[Iacopo]

..a top with independently spinning coaxial components.

I see what you mean... this could lead to some interesting designs..
If a good idea comes to my mind, I will consider to make something out of it.

[Iacopo]

My submission for Longest Non-Mechanical Top Spin has gone live on RecordSetter.
So now this is an official world record:

http://rec.st/o3S

[ortwin]

Did they make a mistake? They put only the short video up, not the full spin as for all the older records.

[ta0]

Congratulations!

I saw that you asked that the whip top record is separated, but the rules posted still low it.

Personally, I would like to see a record for the longest spin of a finger top with a protruding tip, on a flat surface and with one twirl.

[Iacopo]

Did they make a mistake? They put only the short video up, not the full spin as for all the older records.

I don't know what it happened. I sent them the long video and not the short one. 
It seems like they found the short version by themselves and used it instead.

[Iacopo]

Congratulations!

I saw that you asked that the whip top record is separated, but the rules posted still low it.

Personally, I would like to see a record for the longest spin of a finger top with a protruding tip, on a flat surface and with one twirl.

I too would like that.  I would like that some different categories of spinning tops were considered, each one with its clear rules, and its endurance records, instead of having all of them in one broader category.   

[Jeremy McCreary]

Personally, I would like to see a record for the longest spin of a finger top with a protruding tip, on a flat surface and with one twirl.

Me, too! @Iacopo, what's your personal record in this category, and with which top? What would you change to make it spin longer?

[Iacopo]

Personally, I would like to see a record for the longest spin of a finger top with a protruding tip, on a flat surface and with one twirl.

Me, too! @Iacopo, what's your personal record in this category, and with which top? What would you change to make it spin longer?

It is 23m 56s, with this top, the Nr. 25, (2017), with an external ruby ball tip, (topple speed 210 RPM), on a flat mirror:



But I almost never use flat surfaces for my tops, and I could improve that spin time easily.

A better shape would be that of the Nr. 29, (photo below), the tip is external, (I never tried it on a flat surface).
The topple speed is 165 RPM, and it spun for 29m 38s with a single twirl on the dedicated base.



Then I have the Nr. 30, which is like the Nr. 29, but with a tungsten flywheel. 
It spun for 36m 11s on the dedicated base, tip external, (topple speed 140 RPM), single twirl.

If I wanted a longest spin in this category, with a flat surface, I would start trying with a top like the Nr. 30, maybe with a thinner and longer stem.

[ortwin]

...
Personally, I would like to see a record for the longest spin of a finger top with a protruding tip, on a flat surface and with one twirl.

As pointed out multiple times before, that is also my favorite category - at least for my own tops. In Nov. 2021 I reported here 22 minutes with LaBrassBanda and thought I could go to past 30 minutes in a few weeks from then. But that was not the case. The day before yesterday I reached 20 minutes without pedestal, but now using again the thicker 2mm spokes.
On youtube one can find videos of finger tops that spin for more than 25 minutes with a single twirl without pedestal, but I did not find one that goes longer than 30 minutes. Actually there is that Kemner top that spins for about 50 minutes (does not fall at the end), but Iacopo has his doubts about that.
So Iacopo generously let me try my luck in this category for almost three years now without making serious attempts to enter it also. I think now is the time where you also should give it another shot, it will relatively easy for you to go past 30 minutes, flat surface, one twirl.


Still we should agree with a bit more precision what we mean when we say "flat surface". Most people use not flat surfaces, but concave ones, and that is fine by me. With a complete flat surface the "wandering off" becomes problematic.
My base that I see fit for this category is flat but has a concave part inset in the center. I showed it here.
Maybe we could agree on something like: "the lower tip of the stem should be the lowest point of the top during the whole time of the spin" ?

[Jeremy McCreary]

For comparing these tops on endurance, I'd vote for flat spinning surfaces for several reasons.
 
First is the adverse effect of concavity on spin time. My LEGO tops turn in consistently shorter spin times on concave surfaces. And the greater the curvature, the shorter the spin times.

I know this from testing on optical-grade convex glass lenses of varying focal lengths with well-defined curvatures. Don't recall numbers now, but I think I've seen spin time losses of up to 10%. All my tops have spherical ABS plastic tips with 1.6 to 5.5 mm radii of curvature.

I attribte this effect to increased tip resistance. Might be less with tip materials harder than my ABS plastic, but probably still a factor. Recall a fairly sophisticated article with a formula for the braking torque due to simple rotary sliding friction using Hertzian contact theory. A concave spinning surface definitely increased the torque at constant load and friction coefficient.

If spin time is counted as time to first scrape — as I think it must from a practical standpoint — a typical concave cosmetic mirror also reduces spin time by reducing effective scrape angle for tops smaller than the mirror. Since these mirrors generally have unknown curvatures, this introduces an uncontrolled factor that makes small diiferences in spin time hard to interpret.

[ortwin]

For comparing these tops on endurance, I'd vote for flat spinning surfaces for several reasons.
 
...

For testing/academic reasons, when one compares slopes of spin-down curves using relative short time spans this makes lots of sense.
When comparing absolute spin times or trying to set records lasting more than say 5 minutes, than flat surfaces won't work. I found the tops tend to wander off the  surface no matter how well I tried to level it beforehand. So for valid records we need a different rule.