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[ta0]

My secret to get the long spinners is to blow hard, then hold the top until the speed has decreased to what I feel I want and only then let it free. The release is not rushed, so it's pretty vertical and smooth.
I cannot discount a random factor in some range of transition speeds, but I know for sure that if I release it at the larger speeds it would flip in 2 seconds or less and continue spinning side-wise, but at low speeds it will go quite longer and then just fall with almost no rotation left. The 6 seconds spinners were much more typical than the 10 to 12 seconds: I had to release it just barely below the flipping speed to go that long.

[Jeremy McCreary]

My secret to get the long spinners is to blow hard, then hold the top until the speed has decreased to what I feel I want and only then let it free. The release is not rushed, so it's pretty vertical and smooth.
I cannot discount a random factor in some range of transition speeds, but I know for sure that if I release it at the larger speeds it would flip in 2 seconds or less and continue spinning side-wise, but at low speeds it will go quite longer and then just fall with almost no rotation left. The 6 seconds spinners were much more typical than the 10 to 12 seconds: I had to release it just barely below the flipping speed to go that long.

Very helpful! That takes care of Q1 and Q2 from my last post. But no good deed goes unpunished: Would love to hear your answers to Q3 and Q4 if you have time.

So we have some solid data points: In your hands, no evidence of release quality factoring into sleeper vs. sidewinder behavior. But a clear and reliable dependence on starting turbine speed. And all this probably at my highest speeds and above.

Getting better at maximizing starting speed and releasing vertically and smoothly. Today, got ~2/3 sleepers and ~1/3 sidewinders at my top speeds, which probably don't vary more than 25%. Saw no consistent differences in release speed or quality.

Sounds like I'm operating well below your transition speed range, and perhaps even near the bottom of your sleeper speed range. But could be in some kind of transition zone of my own. Could our tops differ somehow? A small difference in CM height could have a huge impact on behavior.

Q5, for ta0 and Renee: The O-ring accurately marks my top's CM level ~15 mm above the ground. Same with yours?

Guessing this arrangement is by design. LEGO tops with sidewinder-like modes like those below spin about the overall CM when sideways. Give them a good footing for that, as I did here with the thin blue and white disks, and you'll get longer and smoother sideways spins.



Renee tried starting with compressed air from a can. She shared a video showing only spin-up and maybe 1 s after release. From the way the top hopped around, guessing that the speed vastly exceeded anything I can muster. Top was still upright when it skittered off the screen.

Q6, for Renee: What followed in the video -- sleeper, sidewinder, or some other behavior?

[Renee]

Q6, for Renee: What followed in the video -- sleeper, sidewinder, or some other behavior?

It flew off the table and ricocheted around the chair legs.  Not much useful from that observation.

I will try to get it out again today and test some spin speed, and release positions.  Seems like it was more likely to flip on a smooth glass surface.  On the tablecloth, it would sleep more often, although with shorter spin times. 

[Jeremy McCreary]

Q6, for Renee: What followed in the video -- sleeper, sidewinder, or some other behavior?
It flew off the table and ricocheted around the chair legs.  Not much useful from that observation.
I will try to get it out again today and test some spin speed, and release positions.  Seems like it was more likely to flip on a smooth glass surface.  On the tablecloth, it would sleep more often, although with shorter spin times.

Thanks, Renee! I have tops that react to my fastest starters in much the same way. For various reasons, every top has its own min and max operating speeds for a particular kind of play. The trick is to match it to the right starting method, which may or may not be your bare hand.

I've also observed that blow-top sidewinders are more likely when it's easier for the tip to slip out from under the top's CM. In my experience, same is true for other tops that like to end by spinning on their sides. Tip sinkage may be more important than simple friction in this regard. (Sinkage favors sleep in many if not most tops.)

However, the top still has to want to go sideways for that to matter. So it's just another layer in the puzzle.

[ta0]

I tried to recorded at 240 fps with a GoPro but it was not enough to freeze the spin. I don't have anymore the camera that could take 1000 fps. Then I remembered that my phone had a Super Slo Mo I had never tried. To my surprise it records at 960 fps, but only in short bursts of 0.4 seconds. In multi-take mode you can record a normal video and manually start slow-mode sections. Here is an example:



You can see there are 3 slo-mo bursts. On the first one the inner top is spinning about 5.5 times faster than the outside casing. On the second one the casing has already reached 95% of the inner speed. On the last one they are completely in sync and the top about to drop. On a video I took with the GoPro, I calculated the falling RPM at 1200 RPM.
It's pretty amazing how fast the casing is accelerated from zero. I need to record more video.

The shell has 3 different moments of inertia and just by looking at it I believe the vertical one is the intermediate, what would make it unstable. If it's spinning fast enough it overcomes the inner top and makes it spin along the axis of maximum moment of inertia.

Sounded good to me at first, but now I'm struggling with the idea of speed-dependent principal axes in a coax top. I'd like to come back to this issue after dealing with the preliminaries above.

Yeah, now it doesn't sound as good to me either. It would seem to me that even with this explanation it would be independent of the absolute spin rate and only depend on the difference between the inner and out top. So, for the explanation to work, the faster the inner top is spinning, the less time would the outer top need to catch up. This is somewhat counter-intuitive, but perhaps not impossible.

[Jeremy McCreary]

Excellent video, ta0! Do you recall how many seconds it took for your cage to catch up with the turbine? Based on bearing noise, seems to be no more 2 s at my starting speeds.

[ta0]

Excellent video, ta0! Do you recall how many seconds it took for your cage to catch up with the turbine? Based on bearing noise, seems to be no more 2 s at my starting speeds.

Well, on the video above, after 4 seconds the cage has almost caught up, at about 95% the turbine speed.

Q5, for ta0 and Renee: The O-ring accurately marks my top's CM level ~15 mm above the ground. Same with yours?

If I lie it on the side it has a tendency to fall towards the tip, so the center of mass is very slightly towards the tip with respect to the O-ring.