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Author Topic: Seeking tops that spin indefinitely with proper surface tilting (regeneration)  (Read 6012 times)

Jeremy McCreary

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Just posted a video of my LEGO version of "plate regeneration" here.

After looking closely at the regeneration process, I've decided to call it "rock 'n roll regeneration" (RRR) -- partly cuz it works even better in bowls, and partly cuz that's what actually goes on: You keep rockin' the arena, flat or concave, just so, and the top keeps rollin' downhill, picking up speed along the way.

Still not very good at RRR, but it's a very enjoyable multisensory experience with interesting things to see, hear, touch, and sense with your whole body. Highly recommended, and something you can engineer on your own.
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ta0

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Partly cuz it works even better in bowls . . .
Are you sure? I have not tried it myself and I know it's in the 1965 patent, but my guess is that it will force you to lean the top even more, making it harder. But a bowl should help with the counter-spin/precession regens. I'm away from most of my tops this weekend, so I cannot check it.
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Jeremy McCreary

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Partly cuz it works even better in bowls . . .
Are you sure? I have not tried it myself and I know it's in the 1965 patent, but my guess is that it will force you to lean the top even more, making it harder. But a bowl should help with the counter-spin/precession regens. I'm away from most of my tops this weekend, so I cannot check it.

Warning: This is way too long a reply, but it's complicated stuff -- at least to me. It'll all make more sense when you see the video (coming soon).

Maybe I should clarify "works better". Let's generalize to "rolling regeneration" (RR), wherein you boost spin rate by somehow manipulating the arena, flat or otherwise, to force the tip to roll while the top is free (i.e., not held in your hand, as it would be with a wizzzer). We'll come back to how you move the arena to make that happen.

In the RR in a circular bowl I've tested, you give the top a good vertical twirl on the bottom of the bowl and then coax it into orbiting the vertical through the bowl's center without trying to lean it over at all. Looking down from above, the orbital direction will be opposite that of spin, as the rolling contact will be outside the top's spin axis. (You clearly anticipated this dynamic, as it corresponds to the "counter-spin/precession" you mentioned.)

You get into a state of pure rolling almost immediately with this method. When you pump the bowl for constant orbital speed, the tip rolls along a circle of fixed radius inside the bowl. Otherwise, it rolls along a slowly opening or closing spiral with little radial velocity. (Think fast car on a banked circular track.)

If you gave the top enough angular momentum at the outset, gyroscopic action will keep it more or less vertical the whole time. This gyroscopic "stiffening" of the top's orientation means that when centrifugal force (CF) pushes the top's CM outward, it also presses the tip onto the bowl's inner surface, thus increasing the normal reaction force on the tip at the point of contact.

Since friction and rolling resistance both grow with normal force, the CF effectively boosts traction -- which boosts the maximum regenerating torque achievable by pumping the bowl -- which boosts the spin acceleration rate (if you pump correctly) -- which boosts both orbital radius and speed (since we're now rolling without slipping on a banked track) -- which boosts the CF and normal force even more.

This neat positive feedback loop is broken only (a) when the user backs off on pumping the bowl, or (b) when the tip climbs over the rim. In the latter case, the top flies off, still spinning upright, and the bowl's become a top launcher! And a pretty powerful one, too. (To control launch direction, you just spill the bowl before the top escapes on its own.)

Hence, RR "works better" in a bowl than on a flat arena in that it's much more effective at accelerating spin rate and also capable of achieving much higher spin rates. And the bowl's at least as much fun.

But now I'm thinking that I shouldn't have called RR in a bowl "rock n' roll regeneration". Yes, in RR on a flat arena, you move the arena with a rocking or combined rocking+circular motion with a definite vertical component either way. But RR in a bowl works only when you move the bowl horizontally in a circular or back-and-forth motion with no vertical component.

So if "rocking" necessarily implies vertical motion, we should either reserve "rock n' roll regeneration" for flat arenas or just use "rolling regeneration" to cover flat arenas and bowls alike. I plan to do the latter from now on.
« Last Edit: August 18, 2019, 04:43:48 AM by Jeremy McCreary »
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ta0

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So, with the bowl you are achieving counter-precession regenerations. But are they easier than the forward-precession regenerations on a flat plate? Can you achieve at all forward regens in a bowl? Is there an ideal shallow bowl in which forward and counter regens are equally easy? I need to re-read the 1965 patent and see what it says. Note that you can replace "precession" by "spin" in the name, but counter-spin regenerations sounds paradoxical.
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Jeremy McCreary

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Behold my gyrocyclotron -- a gyroscopically stabilized high-energy rolling top accelerator. Here you see my only workable bowl and one of my best LEGO gyrocyclotron tops...



Before answering your questions, wondering if the top's orbiting motion about the bowl's vertical centerline is really a gyroscopic precession in the usual sense? The top's nearly constant small inward tilt while orbiting is surely maintained gyroscopically. But the orbiting itself seems more like just rolling tip travel around a banked circular track.

So to be safe, I'm sticking with "orbiting" for now.

So, with the bowl you are achieving counter-precession regenerations.... Can you achieve at all forward regens in a bowl?

Exclusively, and really doubt it, resp. But if anyone could pull off high-speed forward regens in a bowl, it would be you.

If the top is to orbit the bowl by rolling without scraping at high speed, I think the rolling contact pretty much has to be outboard of the spin axis. And that means an orbital direction opposite spin. In my hands, trying to make the top orbit the other way instantly kills its spin, and it goes down with a thud.

But are [regenerations in the bowl] easier than the forward-precession regenerations on a flat plate?

Much easier, and I am to skill toys as canaries are to mines: The smallest challenges trip me up. :o

The only tricky part is sustaining max orbital speed -- and hence max spin rate. This occurs just before the tip climbs over the rim, and that's best avoided by listening closely to the whining sound made by the tip on the bowl.

Is there an ideal shallow bowl in which forward and counter regens are equally easy?

You're right in thinking that the bowl can't be too deep for its diameter. But too shallow is just as problematic. I'm having a hard time imagining a bowl that would make forward regens possible while containing the top well enough to achieve the high orbital speeds I'm getting.

This circular serving bowl works beautifully. The other 9 I found around the house didn't work at all. For starters, most had inner bottom flats. The initial transition from spinning top to spinning+orbiting top is almost spontaneous when the bowl's inner bottom is curved but fails with even a small flat.



The inner surface closely approximates part of a sphere of radius R = 126 mm, and its depth is only 54% of that. The aperture is 224 mm across. The slope at the inside rim is ~25° from vertical, and any workable top must have a scrape angle a good bit smaller than that. That means a rotor packing a lot of AMI into a relatively small maximum radius with a lot of clearance underneath. Hence the wide but thin high-density rubber tire and long black tip holder to its right.

You need a ball tip with some grip, and the larger the top's AMI, the larger its maximum radius of curvature must be. This small hard rubber tire makes a perfect tip for the high-AMI top shown. The tread lets you gauge orbital speed by ear, and that helps you bring the tip right up to the rim without going over.


« Last Edit: August 18, 2019, 07:46:52 PM by Jeremy McCreary »
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the Earl of Whirl

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Interesting bowl.  We have been using IKEA bowls for a number of these activities.
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Jeremy McCreary

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Interesting bowl.  We have been using IKEA bowls for a number of these activities.

Dug this fine vintage Melmac bowl out of some old camping gear boxes in the garage. Gotta be at least 30 years old.

What do your IKEA bowls look like, and how do you use them?
« Last Edit: August 18, 2019, 07:44:11 PM by Jeremy McCreary »
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the Earl of Whirl

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We got started on this bowl from this classic spinning top circus video.  I think johnm was the one who pointed me to the IKEA sale.....

https://m.youtube.com/watch?v=LDXAhwhsZ9k
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ta0

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This is interesting. Unfortunately, I discovered that I don't have suitable bowls. Ikea opened a shop over here several months ago. It's time I give it a visit.

I re-read Martin's patent:



It covers both bowls and flat plates. However, it explicitly mentions that the spin and orbit directions have to be the same. So it only covers forward regens.

Quote
Before answering your questions, wondering if the top's orbiting motion about the bowl's vertical centerline is really a gyroscopic precession in the usual sense? The top's nearly constant small inward tilt while orbiting is surely maintained gyroscopically. But the orbiting itself seems more like just rolling tip travel around a banked circular track.

So to be safe, I'm sticking with "orbiting" for now.
I was mentioning precession just to define the direction of the orbit as forward or counter. For the counter the top mostly remains vertical and precesses little. However for forward regen I am guessing that if you match the orbit period with the precession period you get the smoother movement.
« Last Edit: August 19, 2019, 12:22:33 AM by ta0 »
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Jeremy McCreary

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This is interesting. Unfortunately, I discovered that I don't have suitable bowls. Ikea opened a shop over here several months ago. It's time I give it a visit.

I re-read Martin's patent: It covers both bowls and flat plates. However, it explicitly mentions that the spin and orbit directions have to be the same. So it only covers forward regens.

Martin's bowl looks like it's shallower than mine. I'll have to try to find one like it. Does the patent give measurements?

Wonder how fast he got his top to orbit and spin in the bowl? In one video I timed, the black and white top above turned in maximums of ~1.3 m/s in orbital speed and ~1,200 RPM in spin rate with the tip as close to the rim as I dared. The initial spin rate was maybe 40% of that. A skilled player could have sustained these speeds indefinitely.

For the counter the top mostly remains vertical and precesses little. However for forward regen I am guessing that if you match the orbit period with the precession period you get the smoother movement.

Just what I've observed, both on flat arenas and in the bowl.
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Jeremy McCreary

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We got started on this bowl from this classic spinning top circus video.  I think johnm was the one who pointed me to the IKEA sale.....

https://m.youtube.com/watch?v=LDXAhwhsZ9k

Thanks, Mike! Never tire of this video. Will be ordering one of those bowls. Maybe it's shallow enough for the forward rolling regens ta0's interested in. Just hope it's steep enough to contain the high-speed reverse rolling regens I've been doing with my steeper bowl...

https://www.youtube.com/watch?v=WA67H3hJAY0


« Last Edit: August 20, 2019, 03:08:11 AM by Jeremy McCreary »
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Jeremy McCreary

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Anyone: Confused now about the IKEA bowl's inner surface. How smooth is it?
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andydecleyre

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Are you sure there was a Top-no-sis with a different shape than the Mushroom?

I found an old board for the top-no-sis with a photo of the old-style LSX:





EDIT: Just ordered the Taorenado, woohoo!
« Last Edit: February 26, 2020, 12:55:08 AM by andydecleyre »
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ta0

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The first top I really appreciated was the "top-no-sis" / "LSX" -- meant to spin as long as someone properly tilts a surface underneath it. The older models had a more normal top shape, which I preferred, but the newer ones have a tulip-like shape. I can't find any photos of the original. In order to work like this, it's spun on (what at least appears to be) the handle (upside-down).
Thanks for sharing that photo. I can see that it had to be spun on the "handle" for regenerating, as the other side is too pointy.

I think you'll like the Taorenado.
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