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[zaggernut]

It isn't just the flat spot, the tip friction with ball tips is noticeably lower during the precession in any case, flat spot or no flat spot:

https://www.ta0.com/forum/index.php/topic,5248.msg56154.html#msg56154

Another interesting experiment thread! Interesting how the almost 5mm ruby ball tip exhibited even less tip friction on standard glass than the spiked carbide tip did on carbide, when the RPM is sufficiently high. Yet the ruby top's tip losses soon exceeded that of the carbide top's even before the ruby top stopped walking. Of course, there are too many differences between the tops and bases you used and an EDC top, mass being an important one, so I will be well served experimenting with material/tip shape on my own.

Hmm, that comment disappeared. Are there rules that you can not put an address/link in a youtube comment? Anyone her knows?

Video publishers can choose to automatically hold comments with hyperlinks for manual review, as a way to reduce spam/scams. Whether they actually check them is another matter.

[zaggernut]

If I understand correctly, I've been using the reverse of this contact in my LEGO tops and really like it for certain purposes when spin time isn't paramount.

Pretty sure that my "ball-on-ring" contacts generate more braking torque than my conventional "point" contacts. But that's with ABS plastic on ABS. Definitely worth investigating with other materials.

That is a fun contraption! Lot of ideas to be had with 2 tops, such as trying to spin one on the flywheel of a more massive top. I suppose it would be similar to spinning a top on a turntable, but I have not seen either been done.

I am not sure what you understood, but my idea (if we are going the spintime optimzation using flatspot route that lowers topple RPM) is to hollow out the flatspot created on a large ruby ball, in order to reduce the contact area of the tip while retaining the potential benefits of having a tiny flatspot.




PS if anyone knows how to embed non-square image previews

Code: [Select]

[img]https://i.ibb.co/PDyzy4s/image.png[/img]doesn't seem to work

[ta0]

PS if anyone knows how to embed non-square image previews

Code: [Select]

[img]https://i.ibb.co/PDyzy4s/image.png[/img]doesn't seem to work

You can link to the full image and limit the width if you want it smaller, like this:

Code: [Select]

[img width=400]https://i.ibb.co/VwGpGD0/image.png[/img]


but do this only if the image is not more than 800x800 or at most 1000x1000 pixels. For larger images, upload two images, a smaller one to embed and the full size to link to it. You can do that with the same "add image to post" and then combining the codes.

Note that when you upload an image there is the option to resize it (click on the pen icon):





What I generally do is to resize the image to 800 pixels in it's maximum direction. From the preview I navigate to the the image and copy the link to the full size image and replace the code for the thumbnail image.

PS: Please, do not just resize a large image just by using the width or height codes: the browser will still download the full image and slow down the page.

[Jeremy McCreary]

I am not sure what you understood, but my idea (if we are going the spintime optimzation using flatspot route that lowers topple RPM) is to hollow out the flatspot created on a large ruby ball, in order to reduce the contact area of the tip while retaining the potential benefits of having a tiny flatspot.

Ah, should have guessed that you had a flat support in mind. Change the flat support in your drawing to a ball with a diameter larger than that of the divot in the ball tip, and you have to contact I thought you meant — basically, my ball-on-ring contact upside down. In that case, there would be nothing to keep the top from falling over.

An endurance top with the drawn contact would be fine for your own entertainment/experimentation. The only rules in effect would then be the ones you make for yourself.

But if the goal were to compete with others' tops on spin time, I'd disqualify that tip. Ditto for a tip designed to develop a flat after release.

And for a world-record spin time, I'd want to examine the tip afterward for a flat that might have prolonged spin time artificially.

[ortwin]

...
But if the goal were to compete with others' tops on spin time, I'd disqualify that tip. Ditto for a tip designed to develop a flat after release.

And for a world-record spin time, I'd want to examine the tip afterward for a flat that might have prolonged spin time artificially.

So what would be  the world record by your/our rules in the no pedestal class at the moment? Do you think it can be found in that youtube channel of the spinning top enthusiast ? Or do you have a serious candidate at least prior to examitation of the tips?

[Jeremy McCreary]

...
But if the goal were to compete with others' tops on spin time, I'd disqualify that tip. Ditto for a tip designed to develop a flat after release.

And for a world-record spin time, I'd want to examine the tip afterward for a flat that might have prolonged spin time artificially.

So what would be  the world record by your/our rules in the no pedestal class at the moment? Do you think it can be found in that youtube channel of the spinning top enthusiast ? Or do you have a serious candidate at least prior to examitation of the tips?

To be honest, no clue, as I have little interest in spin time records beyond the STEM (science, technology, engineering, math) principles involved. No chance of competing on spin time with LEGO as a medium, but I have many other design space dimensions to keep me busy — many more than you get with tops made on lathes. Of course, I make every design spin as long as it can using the same STEM principles.

You can have a competition on any set of rules as long as the rules are explicitly and clearly stated. Iacopo can tell us the rules for a Guiness world record on spin time. But I bet they say nothing about small flats on tips.

[ortwin]

I took a look at the endings of the videos with spin times of more than 45 minutes on that channel. This one looks to me as if it could be a candidate:



A Plier top with a spintime of 52 minutes.

[Iacopo]

Interesting how the almost 5mm ruby ball tip exhibited even less tip friction on standard glass than the spiked carbide tip did on carbide, when the RPM is sufficiently high.

When the RPM is high, yes, but, what it matters, it is when the angle of tilting is large. The best condition for the ball tip is when the top is quite tilted and the spinning surface has a thin oil film; the problem is that, while spinning, the top rises so the tip friction increases.
The oil, which gives the advantage of a decreased rotational sliding friction at the tip, (and of the total friction at the tip), also gives the disadvantage of an increased rolling resistance, which, in turn, accelerates the rise of the top.
By the way, grease used as a lubricant, which makes the rolling resistance even higher, makes the rise even faster.
If you find a way to use ball tips and oil without making the top to rise, you could have found the way to have the lowest average total tip friction for a top.
 

Of course, there are too many differences between the tops and bases you used and an EDC top, mass being an important one, so I will be well served experimenting with material/tip shape on my own.

In this test I always used the same top, with the two different tips. The spinning surfaces are different but the spiked carbide tip digs too rapidly a concavity in the glass, not even a ruby base is wear resistant enough for it, it needs the carbide base; and ball tips wear more rapidly on a carbide base so I normally use them on glass, not on carbide.

[Jeremy McCreary]

I took a look at the endings of the videos with spin times of more than 45 minutes on that channel. This one looks to me as if could be a candidate:

A Plier top with a spintime of 52 minutes.

That's a very impressive time for a single twirl! Very rough estimate of speed right after 51:30 = 20 RPM.

Makes me suspect a flat on the tip. As I recall, Iacopo's slowest topple speed is ~30 RPM. And a very rough best-case critical speed estimate for this top is well above 60 RPM.

[Iacopo]

Iacopo can tell us the rules for a Guiness world record on spin time.

I don't know them, I didn't investigate after knowing that finger tops are considered by them in the same category of whip tops, and at that time the record was that of a whip top, about 8 hours, if I remember correctly, an impossible spin time for a finger top; practically, they do not consider finger tops, (unless things changed in these last years, but probably not).

[Jeremy McCreary]

Iacopo can tell us the rules for a Guiness world record on spin time.

I don't know them, I didn't investigate after knowing that finger tops are considered by them in the same category of whip tops, and at that time the record was that of a whip top, about 8 hours, if I remember correctly, an impossible spin time for a finger top; practically, they do not consider finger tops, (unless things changed in these last years, but probably not).

If not Guinness rules, then what rules were in effect for your most recent world record?

[ta0]

I took a look at the endings of the videos with spin times of more than 45 minutes on that channel. This one looks to me as if could be a candidate:

A Plier top with a spintime of 52 minutes.

That's a very impressive time for a single twirl! Very rough estimate of speed right after 51:30 = 20 RPM.

Makes me suspect a flat on the tip. As I recall, Iacopo's slowest topple speed is ~30 RPM. And a very rough best-case critical speed estimate for this top is well above 60 RPM.

I measured 50 RPM. You can move frame by frame on a Youtube video using the comma and point keys and this video has 25 frames per second. From what appears as a brighter spot I measured 30 frames on the last turn before falling. A few seconds before it was spinning at 60 RPM (25 frames per turn).

I think the video is a good candidate for the record. The wobbling at the end looks natural to me.

[Jeremy McCreary]

I measured 50 RPM. You can move frame by frame on a Youtube video using the comma and point keys and this video has 25 frames per second. From what appears as a brighter spot I measured 30 frames on the last turn before falling. A few seconds before it was spinning at 60 RPM (25 frames per turn).

I think the video is a good candidate for the record. The wobbling at the end looks natural to me.

Great YouTube trick! I'll go with your speed estimates and give the benefit of the doubt on the terminal wobble.

Am I the only one who thinks a smaller stem OD might give a faster release speed? Might also reduce knurl-related drag.

[ortwin]

...
Am I the only one who thinks a smaller stem OD might give a faster release speed? Might also reduce knurl-related drag.

Well it "might" give a faster release speed, but maybe not. The optimum stem diameter for maximum release speed, depends, as you know, strongly on the AMI of the top. For a top with a given AMI a smaller stem diameter corresponds to a "higher gear", which might not be optimal for highest release speed. Imagine you put the chain on your bicycle to a certain gearwheel and you want to determine how fast you can be after the first initial half step starting the bicycle. If the gearwheel (connected to the wheel) is very small,  you hardly move the bike. If the gearwheel is  very large it is easy to move at first but the speed after half a "step" will also be small because there is so small a length where the force is acting. What is optimal depends also on your strength, or rather your weight in the bicycle example.
So for a given flywheel/AMI and person to operate the top, it would be best to have a modular system where you can test all stem diameters from 3 mm to say 15 mm in steps of 1 mm.
We had similar discussions before, like this one , there are a few posts before and after the actual link also.

[Iacopo]

If not Guinness rules, then what rules were in effect for your most recent world record?

These are the RecordSetter rules, for the longest non-mechanical top spin:

Rules
- must follow form of current world record holder
- spinning top may not have bearings, zip starters, or moving parts
- top may be whipped while spinning to build up speed
- timing starts when fingers pull away and stop when top comes to complete rest
- use of magnets not permitted
- must follow form of current world record holder
- must provide video evidence

https://recordsetter.com/world-record/spinning-non-mechanical-spinning-top/57270
On this page, click on the link "challenge it" for to see the rules.