Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Jeremy McCreary]

Your design goals seem to be headed in the direction of Maxwell's dynamical top -- a laboratory top that ended up making significant contributions to both rigid body dynamics and the modern theory of color vision.

Maxwell never tired of toys and used them in his experiments whenever he could. The spinning top was a favorite.

Jeremy: great link to that picture of an original Maxwell dynamical top and the video from Aberdeen University Museum. 

Another page about Maxwell's experimental tops -- this one with a photo of a Simonelli as well!

https://philipganderton.com/personal-pages/going-for-a-spin/maxwells-dynamical-top/

Iacopo, your tops are famous!

[ortwin]

... LEGO tip holder duly noted. ...

I am glad that you still talk to me even though I put four holes into that LEGO piece and even applied a drop of crazy glue to stabilize the tip.
I could have used something else instead of the LEGO piece, but I wanted to shock you. 

Excellent find that  Maxwell top! But ta0 did a good job of dampening my hopes now! First he drew me into the direction of the flywheels, and now leaves me there standing alone in the open! Thank you! - No, just kidding of course: even if this spooky spokes business does not lead to reaching any of the goals I set myself for a long spinning top, there are still some nice concepts that came out of this series: the punctuation "mini sub-series",  the topological top, the winder included top, the multiple reversible top....

[Iacopo]

Another page about Maxwell's experimental tops -- this one with a photo of a Simonelli as well!

https://philipganderton.com/personal-pages/going-for-a-spin/maxwells-dynamical-top/

Iacopo, your tops are famous!

To be famous among the makers maybe is not the best thing because they may imitate what I do, for commercial purposes, which I don't like very much, even if these are simple spinning tops, nothing really important.
Nobody made finger tops with a recessed tip like the mine, before me.  Now, from time to time, I see someone else making them.  Cami Lewis is the only maker who gently asked me to copy my design, which I sincerely appreciated.
Mr. Philip Ganderton, (Drphilgandini on Instagram), who posted my photo on that Maxwell top page, is too a maker, and he too replicated my design, (recessed tip, dedicated base, long stem, metal flywheel and light core), making many tops in this way.
He also seemed to like my idea of using a sea urchin shell for making a top because soon after having made the mine, he started making tops with sea urchin shells, and he made many of them.

[Joah]

Cool build! It's really satisfying to watch spin.

[Iacopo]

even if this spooky spokes business does not lead to reaching any of the goals I set myself for a long spinning top,

I too have come to believe that very probably the design with the spokes does not help the top to spin longer.

The reason, I believe, is that, while with the spokes there is the advantage of less surface for the air drag, on the other side there is the disadvantage that the "ground effect" is lost, because the air fuelling the Von Karman flow under the flywheel passes through the big hole in the center of the top, and this increases the air drag.

I don't have tops suitable for a demonstration, but Jeremy has the yellow one with thin black spokes, which could be perfect.
If Jeremy could spin that top, with the big hole in its center closed by a sheet of paper, probably he would see that the top spins longer than with the hole open.

I already suggested him this but he didn't try, maybe because a sheet of paper is not a Lego piece... or maybe this test in not interesting for him.

[Iacopo]

But if one doesn't care about tip friction (and therefore how heavy the top is) and only cares about air drag, a compact top with the mass against the axle may be ideal.

I would not be able to predict this theoretically because of my ignorance about mathematics, but I reached the same conclusion after this test. 
The tops below have the same AMI but different weights/diameters.

The three tops were timed starting from 1250 RPM; the most compact one, (Nr. 28, red line), is the most efficient at high speed, where air drag is important;
after ten minutes, it was still spinning at almost 700 RPM.
The other two tops are less efficient and after ten minutes they were spinning at about 650 RPM, (Nr. 27), and 550 RPM, (Nr. 26).

In the second halves of the curves things reverse because of the tip friction becoming more and more important relatively to the air drag, and the tip friction punishes especially the Nr. 28 because it is the heavier top.
Still, after 20 minutes of spinning, the Nr. 28 is the best one.

Anyway, the Nr. 28, being the one with the highest CM on the tip, and having the shortest radius of gyration, is the less stable and topples down first.  The Nr. 26, which has the lowest CM on the tip and the largest radius of gyration, is the more stable, and it spun for the longest time, in spite of losing more RPM at the start, for higher air drag, (larger diameter).

So things are a bit complicated because we have to consider the air drag, the tip friction, (at least with tops of this weight tip friction is significative), and the toppling down speed.   

     

[Jeremy McCreary]

I don't have tops suitable for a demonstration, but Jeremy has the yellow one with thin black spokes, which could be perfect.
If Jeremy could spin that top, with the big hole in its center closed by a sheet of paper, probably he would see that the top spins longer than with the hole open.

I already suggested him this but he didn't try, maybe because a sheet of paper is not a Lego piece... or maybe this test in not interesting for him.

This test is definitely of interest, as I share your hunch now. And it's still on my to-do list. Just got side-tracked with some other projects.

Using non-LEGO or modified LEGO components doesn't bother me. Found a thin clear plastic cover from a store-bought pie that should work quite well as a bottom fairing. Good pie, too.

[Jeremy McCreary]

So things are a bit complicated because we have to consider the air drag, the tip friction, (at least with tops of this weight tip friction is significative), and the toppling down speed.

Complicated is an understatement! When spin time is all that matters, you become locked in an inescapable trade-off involving air resistance, tip resistance (including weight), and critical speed. And nothing increases critical speed like raising a top's CM.

Unfortunately, the only practical way to find the sweet spot, given all the things we don't know, is to test. And the test matrix needed to find the very best combination of parameters would be quite formidable.

Which is a good argument for giving other design goals higher priority. Just make a top you like for its static appearance, its visual effects at speed, its surprising behaviors, its improbable construction, or the story it tells. Then tweak it for spin time as best you can.

I think this approach makes the life of a topmaker simpler and a lot more fun.

[ta0]

Mr. Philip Ganderton, (Drphilgandini on Instagram), who posted my photo on that Maxwell top page, is too a maker, and he too replicated my design, (recessed tip, dedicated base, long stem, metal flywheel and light core), making many tops in this way.
He also seemed to like my idea of using a sea urchin shell for making a top because soon after having made the mine, he started making tops with sea urchin shells, and he made many of them.

I checked his Instagram. He calls the pedestal tops Maxwell tops. The original Maxwell top had the recessed tip and dedicated base, but was not a finger top. Anyway, the ones I saw at least have a somewhat different look than yours, without the smooth curve between the flywheel and the stem. But he really ran with your idea of the sea urchin and made many of those. It's very difficult to keep a good idea to oneself.

I found an interested blog post he made about the efficiency of finger tops with respect to weight. He defined the Zen ratio as the ratio between the spin time in minutes and the weight in grams. This is the table from that post:



The smallest tungsten tops tend to have the best Zen ratio. By the way, I met Tom Griffin at the Texas TopCon and he does have a strong spinning snap.

[ortwin]

The reason, I believe, is that, while with the spokes there is the advantage of less surface for the air drag, on the other side there is the disadvantage that the "ground effect" is lost, because the air fuelling the Von Karman flow under the flywheel passes through the big hole in the center of the top, and this increases the air drag.

That may be correct for a range of ratios of sl/fw. (sl = spoke lenght, fw = flywheel width), but as the spokes get longer in comparison to the width of the flywheel, the "less surface on upper side" effect should win over the "lost ground effect".  In my next top for example the three thin spokes will be about five times as long as the flywheel is wide and   high ( it is a torus with a square generator).

[ortwin]

...

I found an interested blog post he made about the efficiency of finger tops with respect to weight. He defined the Zen ratio as the ratio between the spin time in minutes and the weight in grams. ....

The smallest tungsten tops tend to have the best Zen ratio. By the way, I met Tom Griffin at the Texas TopCon and he does have a strong spinning snap.

I am afraid we have to disregard most of what you say in this post! Since "Zen factor" goes so well with "Tao" you must be highly biased!


 
https://en.m.wikipedia.org/wiki/The_Tao_of_Zen
(I have no idea what all that means)

[ta0]

I am afraid we have to disregard most of what you say in this post! Since "Zen factor" goes so well with "Tao" you must be highly biased!
https://en.m.wikipedia.org/wiki/The_Tao_of_Zen
(I have no idea what all that means)

The only book about Taoism I have ever read was The Tao of Pooh  . I still have pending in my reading list another classic: The Tao of Physics . . .

[Iacopo]

He calls the pedestal tops Maxwell tops.

He is not the only one calling them in this way. 
This is George Sherwood on instagram:
"Finished this Maxwell style top up a week or so ago. It’s very similar to the @simonellispinningtops designs. I’m trying to find ways to make my designs different."
Me: " Thank you for the credit, George."
George: "@simonellispinningtops absolutely! Finding ways to@make them@different@but in the same style is challenging for sure!"
I like the honest persons. In fact he added the decorative moldings, like Gandini does, which is something purely aesthetical, but the basic features are the same of my design, (recessed tip, dedicated base, long stem, metal flywheel, and light core/stem, made of wood in this case).

This is the first one made by Gandini in this style:

A design from someone else.  I don't keep track of all but it seems like I started a trend.

An original Simonelli spinning top, for comparison.
 

[ta0]

Iacopo: you are still the master and recognized as such.

"Imitation is the sincerest form of flattery,"  Charles Caleb Colton 1820
or if you prefer:
"Imitation is the sincerest form of flattery that mediocrity can pay to greatness," Oscar Wilde
or for a positive twist:
"Imitation is not just the sincerest form of flattery - it's the sincerest form of learning," George Bernard Shaw.

[Jeremy McCreary]

Iacopo: you are still the master and recognized as such.
"Imitation is not just the sincerest form of flattery - it's the sincerest form of learning," George Bernard Shaw.

Amen to both statements!

In music, we have the "cover", wherein one artist or group puts their own spin on an "original" written or famously first performed by others. Sometimes the covers are even better than the originals. Covers are a valued tradition in jazz, and classical performances are pretty much all covers. To make sure the original artist(s) get the credit they deserve, the cover still goes by the original title.

Case in point: Marvin Gaye gave us many cherished originals. But I'm also grateful for the way Teddy Swims covers some of them...

youtube.com/watch?v=0XQ6M6eyO5A&t=1s

Then we have "new" genres like jazz and rock and roll. The early artists surely inspired each other and probably covered each other on stage. Was there ever a single inventor? Definitely not. These genres crystallized out of a heady mix of innovation and cross-fertilization based on pre-existing trends.


Iacopo's tops are now drawing the covers they deserve among topmakers. Some of the covering topmakers may not even know about the Simonelli originals at this point. But all of the really close covers should be crediting somebody.

In topmaking, we must also acknowledge the intertwined roles of independent (re)discovery and convergent evolution. Design and make enough tops, and some design directions like the down-and-out mass distribution just become inevitable. Taken to its ultimate conclusion, down-and-out leads directly to the recessed tip and the dense flywheel on a much lower density core. And once you have a recessed tip, you of course need a secure pedestal shaped to let the top do its thing.

I've said this many times, but it bears repeating here: Look at large collections of vintage tops dating back centuries, and you'll find similar designs popping up over and over again. To the point that truly novel designs are now few and far between. Independent (re)discovery, convergent evolution, homage, intellectual property theft? Very hard to say in most cases.

Bet you'll even find some Simonelli precursors besides Maxwell's. But one thing's for sure: The Simonelli top has (re)invigorated a genre worthy of much more exploration.