iTopSpin

Current Posts => Collecting, Modding, Turning and Spin Science => Topic started by: ortwin on February 08, 2021, 09:36:13 AM

Title: Curtain Ring tops + follow ups
Post by: ortwin on February 08, 2021, 09:36:13 AM
Curtain-Ring-Top Nr.1 - PERIOD.
 
It has been my guess for a while that a platinum wheel with 3 needle spokes would have the absolute longest duration possible.
Now that was an inspiring remark for me! Especially the word "needle". I remembered these pins with the yellow glass head my wife has in her sewing set. When I looked for them I also found these white plastic rings - they are used for curtains or something.
(https://i.ibb.co/nsWvwwv/needle-ring-euro-quarter.jpg) (https://ibb.co/nsWvwwv) (https://i.ibb.co/vkGWNXF/quickringneedletop.jpg) (https://ibb.co/vkGWNXF)
It is not a well balanced top, still it is spinning for a bit more then a minute. If one considers the low density of the plastic and the quick and dirty execution in building the top ... . Probably even with a brass ring  10 minutes should be possible with a more careful setup.
https://youtu.be/B9uJO5Z89mc (https://youtu.be/B9uJO5Z89mc)
Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on February 08, 2021, 12:14:25 PM
@ortwin: Love your curtain-ring top! If you look beyond the high-performance category, a minute of spin time is quite good for a finger top. Nice demo of the value of the down-and-out mass distribution and designing with air resistance in mind.

I think you've set a fun but difficult challenge for yourself. I'd encourage you to keep an open mind about best solution for each spin-time benchmark. Engineering-wise, tops are way more complicated than they look, as many competing but coupled nonlinear processes are in play. And the sweet spots aren't always where you expect them.

Easier said than done with scratch-built tops, of course, but repeated guess-and-check cycles will serve you well.

Since my LEGO tops will never win spin-time contests against high-performance metal tops, I usually go for play value (including visual effects at speed) instead. Once a design is sufficiently entertaining, I then maximize its spin time as best I can.

Despite the wobble and spin time, your curtain-ring top's a lot of fun. Spin time isn't everything.
Title: Re: Curtain Ring tops
Post by: ortwin on February 08, 2021, 12:15:59 PM
Actually I just found something that could act as tip as well as a spoke:

(https://i.ibb.co/b3mFqgv/Messeinsatz.jpg)
Messeinsatz D.2mm Kugel L.35,7mm Gewinde M1,6 HM für Fühlhebelmessgerät 

Do not know what to call it in English. But you can get the ball (tip) in various hard materials that sound as if they were suited as a tip for a top. Also there are various ball diameters available. It is a part of an instrument used for example with e lathe to do precision measurements of contours. The shaft has a diameter of 2 mm in this case. So it is a lot more rigid then a pin of 0.6 mm diameter.

Title: Re: Curtain Ring tops
Post by: the Earl of Whirl on February 08, 2021, 12:17:52 PM
I think that curtain-ring top is clever and fun.  Good work!!!
Title: Re: Curtain Ring tops
Post by: Iacopo on February 08, 2021, 04:08:50 PM
Actually I just found something that could act as tip as well as a spoke:

You are ingenious !  I am sure you will make interesting things.
Title: Re: Curtain Ring tops
Post by: ortwin on February 11, 2021, 03:00:39 PM
Curtain-Ring Top  Nr. 2 - two spokes
(https://i.ibb.co/LzVGzfj/curtainring-two-spokes-1.jpg)   (https://ibb.co/LzVGzfj)(https://i.ibb.co/hWnG9tD/curtainring-two-spokes-2.jpg)  (https://ibb.co/hWnG9tD)
(https://i.ibb.co/hVYr8WF/curtainring-two-spokes-4.jpg)   (https://ibb.co/hVYr8WF)
This is the concept I suggested in my last post:
... two  [spokes] would be enough: thread a ball bead on your string, tension the string across the diameter of the flywheel, fix the ball bead on the string so that is sits right in the middle of the flywheel. ....

 

video (https://youtu.be/3OUUrS8tdwU)

Actually this "curtain ring top" thing is becoming a little series of presentations of concept tops. Can anyone guess how many spokes my next curtain ring top will feature? And how many spokes the one after that?
I am happy with the stability of the spokes of this one. For the tip  I took a gold colored plastic pearl from the DIY jewelery kit of my  daughter. The hole is far too big. I still am happy enough with the outcome. I see the concept as having potential! Just chose the right materials and introduce the features I have in mind for better adjustment of the tip position, and there you go. Don't forget the setscrews though for static and dynamic balancing!
The reason I am making this series of concept tops is to find out what I will have somebody make for me on a lathe from proper top material. I hope you don't mind too much that I do not put much time and effort in the presentation and videos. I think the concepts can be understood from these and that is what I want to share at this point.
Title: Re: Curtain Ring tops
Post by: ortwin on February 14, 2021, 02:55:47 AM
Curtain-Ring-Top Nr. 0


(https://i.ibb.co/hCxG5SL/Nr-0.jpg) (https://ibb.co/hCxG5SL)

Very quick build!
https://youtu.be/me9pU8aCG_8 (https://youtu.be/me9pU8aCG_8)

Not much of a top it seems. More like spinning a coin or Euler's disk. Actually this should have come first in this series, but at the time I presented the first Curtain-Ring-Top I did not know it would become a series. For completeness this spokeless top is necessary. Still it is not serious!

But actually I really want to incorporate it in the design of a metal stemless top. I mean I want to have a stemless top that I can use as Euler's disk when turned upside down. It seems the exact curvature of the rim is  crucial. Does somebody here  know what that curvature would be for a 4 cm diameter ring? It would not have to be the best Euler's disk ever, but spolling for 2 minutes while the top part could spin for 20 minutes would be nice. Also I want to approach this dual use thing from the other side: put my Euler disk (the original one) to a lathe and have a 2 mm hole drilled into the very center of its upper side, so it can be used as a stemless top after I put a ceramic ball (3 mm) to it.
Title: Re: Curtain Ring tops
Post by: ortwin on February 15, 2021, 03:51:55 AM
Curtain-Ring-Top Nr. 3

(https://i.ibb.co/mbt8xPG/CRT3-material.jpg) (https://ibb.co/mbt8xPG) (https://i.ibb.co/jvyjfhq/CRT3-almost-ready.jpg) (https://ibb.co/jvyjfhq)
(https://i.ibb.co/6JNGttL/CRT3-almost-ready-sideways.jpg) (https://ibb.co/6JNGttL) (https://i.ibb.co/dtS8kDK/CRT3-ready.jpg) (https://ibb.co/dtS8kDK)

 This is the top  that most literally is like the one in the remark that inspired this whole "Curtain-Ring-Top" series:

 
It has been my guess for a while that a platinum wheel with 3 needle spokes would have the absolute longest duration possible.

 
Alright, it is not exactly a platinum wheel yet, but hey, I think you get the idea.
The fourth needle serves as tip as well as a stem. And the drop of glue that keeps the four yellow spheres together is not shown in the picture with the material.
https://youtu.be/wpePFjOLaWw (https://youtu.be/wpePFjOLaWw)
The performance of this poorly made top is not that great. The very thin stem is hard to spin. It would be probably better to cut it off and just go stemless. Also I need you to excuse the video where the focus goes just somewhere. I admit that I was just too lazy to make a better video, but I promise to put more effort in the next tops of this series.
 

Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on February 15, 2021, 10:29:22 AM
Clever prototype!

With such little ground clearance, not much room for wobble. But guessing this design would be very hard to center and balance, including keeping the spokes evenly spaced. Agree about the stem.

No need to apologize for the videos. It's fun to watch your experiments, and still way better than stills.
Title: Re: Curtain Ring tops
Post by: ortwin on February 18, 2021, 05:53:55 AM
Curtain-Ring-Top Nr. 4 - four spokes


(https://i.ibb.co/StKnNb3/Material.jpg) (https://ibb.co/StKnNb3) (https://i.ibb.co/G36vTj6/half-done.jpg) (https://ibb.co/G36vTj6)  (https://i.ibb.co/0q6cdxC/stringing.jpg) (https://ibb.co/0q6cdxC) (https://i.ibb.co/XjChCpr/done.jpg) (https://ibb.co/XjChCpr)

Air drag is a bit higher than of Nr. 2 since it has more spokes, but it also has some advantages:

- the pebble or pearl or bead or what you might call it (plastic again from my daughters jewelry kit), does not need to be fixed to the center of the string, it stays there automatically

- adjustment of the pebble position (in one dimension) is possible by adjusting the relative tension of the two strings

The little pieces of wire visible in the first photo are shoved into the same holes as the strings  fastening them there. 

 https://youtu.be/MVqGClHYE-g 



With a proper start with two hands it is spinning, without the ring touching the surface, for more than a minute.




Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on February 18, 2021, 10:53:10 AM
Best one yet in terms of wobble! Decent spin time, too.

I have a number of self-centering tops with various moving or loose or floppy parts onboard. Still trying to understand exactly how it works.

Is the video age-restricted to keep your daughter from finding out you're taking her stuff?

Title: Re: Curtain Ring tops
Post by: ortwin on February 23, 2021, 02:35:06 PM
Curtain-Ring-Top Nr. 1.5 - colon top
This is the symmetric version of Nr. 1 :

 
(https://i.ibb.co/JQGb0Zf/Mat-CRT1-5.jpg) (https://ibb.co/JQGb0Zf) (https://i.ibb.co/89g9gY5/CRT1-5-colon-top.jpg) (https://ibb.co/89g9gY5)
It has some more air drag then Nr.1, but it has the advantage that tip positioning and top balancing can be performed independent of each other:

After the tip of the lower pin is adjusted by radial shifting and by tilting of the spoke so that is on the axis of the ring, the upper pin can radially shifted and tilted until the top is balanced.

https://youtu.be/Lgjgga5xaw8 (https://youtu.be/Lgjgga5xaw8)

Besides the commercially available "exclamation mark top"and the PERIOD top (curtain rin top nr. 1) this "colon top" is the third punctuation top I know of, can you think of any other ones?


Title: Re: Curtain Ring tops
Post by: ortwin on March 01, 2021, 03:29:42 PM
Curtain-Ring-Top Nr. 6 - three double spokes, interchangeable tip


(https://i.ibb.co/KwLh75K/CRT6-Mat.jpg) (https://ibb.co/KwLh75K) (https://i.ibb.co/X3tS6d2/CRT6-stringing.jpg) (https://ibb.co/X3tS6d2) (https://i.ibb.co/BCfHRrS/CRT6a.jpg) (https://ibb.co/BCfHRrS) (https://i.ibb.co/4Ffw4x4/CRT6-b-ready.jpg) (https://ibb.co/4Ffw4x4)

In principle the tip can be positioned precisely in the center by tensioning  the three double spokes accordingly. In this simple plastic version though it is not so easy once the top is completed.
 If the single lines are arranged properly next to each other, a double spoke can have the appearance of wide spoke which we said could possibly deliver an aerodynamic advantage. 
Even with only three (double) spokes, there are quite some different possibilities one  could arrange the strings/spokes: more complicated then the one shown here and also more simple possibilities.

The ceramic ball is glued to the inner small tube, the ball pen tip is just stuck into it. I have no idea if it has a steel ball or a tungsten carbide ball, but at this level  of refinement it will not matter at all. 

https://youtu.be/5mA4SOTyE2o (https://youtu.be/5mA4SOTyE2o)
 The centering of the tip was only roughly done by eye judgement, no further balancing. Both versions Nr. 6a and 6b can spin for about a minute. Does that mean a brass version will spin for 10 minutes ? I could probably  spin it to the same starting RPM, that means almost ten times as much energy due to density difference. But then the loss of energy over time due to aerodynamics is roughly the same as in the plastic case, so ............I know this is not so easy, and also not completely correct, but 5 minutes should be possible with a brass Curtain_Ring_Top of similar (but  a bit more careful) build .
 As "spokes", thinner and stronger strings can be found in fishing supply stores.


(https://i.ibb.co/MBYbMZg/fishing-line.jpg) (https://ibb.co/MBYbMZg)
0.03 mm sounds thin, the ones I used here measure 0.3 mm.There is even a fishing line called "Platinum". I am afraid it's only the name, otherwise we  would just take a reel of that stuff as flywheel....

This is the first of the Curtain-Ring-Tops that I am thinking of taking it up a step and build as a metal version. I really consider investing in a brass curtain ring! Well, maybe  after I make one or two other plastic Curtain-Ring-Tops. When I start with the brass ring tops, I will call it the "golden series". Just for the heck of it!;-)

Title: Re: Curtain Ring tops
Post by: ta0 on March 01, 2021, 05:42:48 PM
Your ring tops look pretty good considering the materials you use.

Yeah, I think you can hit 5+ minutes with the brass ring if you build it carefully.
Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on March 01, 2021, 06:55:03 PM
Curtain-Ring-Top Nr. 6 - three double spokes, interchangeable tip
Both versions Nr. 6a and 6b can spin for about a minute. Does that mean a brass version will spin for 10 minutes ? I could probably spin it to the same starting RPM, that means almost ten times as much energy due to density difference. But then the loss of energy over time due to aerodynamics is roughly the same as in the plastic case, so ............I know this is not so easy...

When I start with the brass ring tops, I will call it the "golden series". Just for the heck of it!;-)

Love this curtain-ring series -- especially the last one with the pen tip! My gut tells me that the spin time isn't going to end up proportional to ring density, but I'll think about it.
Title: Re: Curtain Ring tops
Post by: ta0 on March 01, 2021, 10:33:05 PM
Love this curtain-ring series -- especially the last one with the pen tip! My gut tells me that the spin time isn't going to end up proportional to ring density, but I'll think about it.

My gut also told me that it should be something more complicated than linear, but that's not what I got.

If we assume the air drag is proportional to the spin w then we previously got (https://www.ta0.com/forum/index.php/topic,6404.msg69332.html#msg69332) an exponential decay of the spin:

w = w0 exp(-k/I t)

where I is the moment of inertia, w0 the initial spin and the drag torque = k w.
If we set w to the critical spin at which the top falls, wc, and we solve for the time tc to get there:

tc= I 1/k ln(w0/wc)

So the time it takes to fall is indeed proportional to the moment of inertia and therefore to the density, if you keep the dimensions constant and you also manage to keep the initial spin constant.   :)

Edit: This seems to be a general result, not just for an exponential decay. We found before: I dw/dt = - T, where T is the torque produced by air drag and tip friction and may be an arbitrary function of the spin, T(w), but does not depend on I. It can be re-written as  - 1/T(w) dw = 1/I dt.  Integrating both sides: F(w) = 1/I t, where F(w) can be a complicated function of w, but does not depend on I or t. Then tc = I F(wc).


Title: Re: Curtain Ring tops
Post by: Iacopo on March 02, 2021, 03:28:46 AM
Using brass instead of plastic with the same shape/dimensions will not change the air drag but will change the tip friction, being brass denser, so the advantage as for spin time should be not proportional to the flywheel density, but a bit less.
If brass is about 7 times denser than plastic, the brass top could spin maybe 4-6 times longer than the plastic one, at parity of all other factors.
Title: Re: Curtain Ring tops
Post by: ta0 on March 02, 2021, 09:17:07 AM
Good point on the dependence of tip friction on weight, what I did not consider. Tip friction torque is proportional to weight and independent of rotational speed. The question is how big it is with respect to air drag. Given that the tip and mirror are hard surfaces and even the brass ring would be relatively light, plus the critical spinning speed not very low, I expect the air drag to be dominant.
Title: Re: Curtain Ring tops
Post by: Iacopo on March 02, 2021, 01:59:06 PM
The question is how big it is with respect to air drag. Given that the tip and mirror are hard surfaces and even the brass ring would be relatively light, plus the critical spinning speed not very low, I expect the air drag to be dominant.

I too expect the air drag to be dominant, even if I guess that there could be still some influence of the tip friction, but I might be wrong, because I have no data for so light/little tops.
Title: Re: Curtain Ring tops
Post by: ortwin on March 02, 2021, 04:18:34 PM
Curtain-Ring-Top Nr.7 


(https://i.ibb.co/bFtC9rc/Curtain-Ring-Top-Nr-7a-Mat.jpg) (https://ibb.co/bFtC9rc) (https://i.ibb.co/nLfSDCJ/Curtain-Ring-Top-Nr-7a-in-the-making.jpg) (https://ibb.co/nLfSDCJ) (https://i.ibb.co/L52gk1C/Curtain-Ring-Top-Nr-7a-1.jpg) (https://ibb.co/L52gk1C) (https://i.ibb.co/ZTXbq10/Curtain-Ring-Top-Nr-7a-2.jpg) (https://ibb.co/ZTXbq10)

This is another quick one.  I just thought of this possibility today. One of the best things about it, is the material to build it: The curtain ring, the bead and the rubber ring have all quite different functions in the spinning top, but they are topologically equivalent. - And hereby I finally had the chance to use the words "spinning top" and "topology" in the same sentence. Has any one of you ever been asked if topology is the science of spinning tops?
https://youtu.be/O9X5b0DmPt4 (https://youtu.be/O9X5b0DmPt4)
Since there is no need for a hole in the curtain ring for this one, I could also build it using my wedding ring without harming it.

(https://i.ibb.co/q7YVPTM/Curtain-Ring-Top-Nr-7b-Mat.jpg) (https://ibb.co/q7YVPTM) (https://i.ibb.co/Y20QJDz/Curtain-Ring-Top-Nr-7b-1.jpg) (https://ibb.co/Y20QJDz) (https://i.ibb.co/gMhfwCt/Curtain-Ring-Top-Nr-7b-2.jpg) (https://ibb.co/gMhfwCt)

But actually I think it was the other way around: I thought of a way how I could use my wedding ring with its high density as a flywheel for a top without drilling holes into it. Since it was easier, I still did the curtain ring model first.
Now if you take real expensive pearl as the bead here, and some fancy material instead of the rubber band, you would have a nice way to propose - if your partner is into tops at all.
https://youtu.be/kwP3nI03G8A (https://youtu.be/kwP3nI03G8A)
Although I used gold with four Platinum points as a flywheel, the spinning times are not great. Oh well, that was to be expected and not really the goal in this one.

Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on March 02, 2021, 04:40:05 PM
Love this latest version! But the dog's giving me the stink-eye. Will look at videos after her walk...

And hereby I finally had the chance to use the words "spinning top" and "topology" in the same sentence. Has any one of you ever been asked if topology is the science of spinning tops?

Some guys have all the the luck!

By now, tens of thousands of all ages have seen my LEGO tops at various exhibitions. Usually get lots of questions, some technical, but never that one. Kinda glad, too. Have you ever tried to explain what topology really deals with? Besides, most it's way above my pay grade.

Lucky for us math geeks, though, topology does come up in both top design and modular construction.
Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on March 02, 2021, 06:07:22 PM
Curtain-Ring-Top Nr.7 
One of the best things about it, is the material to build it: The curtain ring, the bead and the rubber ring have all quite different functions in the spinning top, but they are topologically equivalent.

Thought I understood that at first, but on 2nd thought, maybe not.

Now if you take real expensive pearl as the bead here, and some fancy material instead of the rubber band, you would have a nice way to propose - if your partner is into tops at all....

Although I used gold with four Platinum points as a flywheel, the spinning times are not great.

Strong argument for a simple wedding band! Question is, how does the recipient of your last proposal feel about these experiments?

Q: Why do you think the gold ring performed under expectations in this configuration?
Title: Re: Curtain Ring tops
Post by: ortwin on March 02, 2021, 06:39:48 PM
Curtain-Ring-Top Nr.7 
One of the best things about it, is the material to build it: The curtain ring, the bead and the rubber ring have all quite different functions in the spinning top, but they are topologically equivalent.


Thought I understood that at first, but on 2nd thought, maybe not.

https://www.britannica.com/science/topological-equivalence
 (https://www.britannica.com/science/topological-equivalence)
Basically all three parts of the top are some things with exactly one hole in them and one type of substance around that hole. To my understanding that makes them topological equivalent. But probably subconsciously the goal was to create that sentence with "spinning top" and "topologically" in it.



Strong argument for a simple wedding band! Question is, how does the recipient of your last proposal feel about these experiments?

Q: Why do you think the gold ring performed under expectations in this configuration?

 

She was very worried and skeptical when she saw how I was playing with the wedding band. But then again I conducted experiments with it before to check for its diamagnetic properties. So she knows that my wedding band is being abused from time to time.

The gold ring did not really perform under expectation in this configuration. The rubber band is really soft and wiggly and unstable here. No comparison to the nylon line used in CRT Nr. 6 for example. Positioning the tip in the center of the ring is therefore not only a matter of luck, it also very unstable even if you by chance have it in the center at one point.
Title: Re: Curtain Ring tops
Post by: the Earl of Whirl on March 02, 2021, 06:52:39 PM
I have always enjoyed spinning my gold wedding ring, but that is just on its side.  Still, it is moving and makes the Earl of Whirl happy!!!
Title: Re: Curtain Ring tops
Post by: ta0 on March 02, 2021, 07:32:52 PM
That was an ingenious way of making a top without having to cut or glue anything but just stretching and deforming. No doubt a very topological top.  8)

In Don Olney's 1994 book (The Tops Book, not to be confused with The Little Book of Tops) he calls his classification of tops Top-ology.
Title: Re: Curtain Ring tops
Post by: ortwin on March 06, 2021, 03:15:33 PM
Curtain-Ring-Top Nr. 8 - 4 spokes, tungsten carbide tip, wind up starter included

(https://i.ibb.co/4KGqdrX/CRT8-1.jpg) (https://ibb.co/4KGqdrX) (https://i.ibb.co/4TZt768/CRT8-2.jpg) (https://ibb.co/4TZt768)

I bought a ball pen that had a 1 mm tungsten carbide tip. The ink is still all over the top as you can see in the pictures. It is also still on my fingers. Of course it makes no difference in this top, here a pencil would work at least as well. Anyways, it is the "wind up starter mechanism" I wanted to test. It is not great, a traditional finger start works a lot better.  With a little bit more complication, something that works much better would be possible.

https://youtu.be/T1_KO_fuqOU (https://youtu.be/T1_KO_fuqOU)
Title: Re: Curtain Ring tops
Post by: ta0 on March 06, 2021, 03:52:57 PM
This curtain-ring-top collection is getting quite big!  8) I might separate it into its own thread.

I'm trying to think if I have a top where the starting spring/elastic mechanism stays with the top and I cannot think of one. That's a very nice compact design that adds practically no mass to the top. Nice!

PS: What are you spinning it on? It looks like the front glass of a tablet, over some adjustable base, over a board game.  :D

Title: Re: Curtain Ring tops
Post by: ortwin on March 06, 2021, 04:24:47 PM
This curtain-ring-top collection is getting quite big!  8) I might separate it into its own thread.

PS: What are you spinning it on? It looks like the front glass of a tablet, over some adjustable base, over a board game.  :D
I think there is only one more to come, I had planned to make a separate thread after that , starting with a presentation of all of them. But I follow your suggestions, what ever you think works best.
I am actually glad you are asking about the base! 
What you see as a board game is just a place mat. 
The adjustable base is a left over of a phase of the levitron experiments.
The front glass of the tablet I chose for different reasons : The mirror bases I also use I find sometimes too concave. Here I make the surface a bit concave with the  suction cup you see on the back side. With heavy tops even that is not needed, the weight of the top makes the surface concave by itself.

Actually I want to test a sapphire base at some stage. This is the test before the test: there are sapphire screen protectors for some smart phone models available (around € 50,-). They seem to be flexible enough from what I see on pics in the net, to make them a bit concave like I tested with this tablet touch screen. I suggested the sapphire screen protectors to Iacopo somewhere in this(?) thread.


Title: Re: Curtain Ring tops
Post by: ortwin on March 06, 2021, 05:37:27 PM
I'm trying to think if I have a top where the starting spring/elastic mechanism stays with the top and I cannot think of one. That's a very nice compact design that adds practically no mass to the top. Nice!
Do we think a starting mechanism like this would be "legit" for  a long spin record? No, of course not! But how would we word the rules that exclude it? "Moving parts" can become quite a relative expression when one thinks of spokes that are somewhat flexible.

 It just might be that this picture I saw a few days ago gave me the idea for this "wind up mechanism".
(https://i.ibb.co/bQY5XPL/ideagiver.jpg) (https://ibb.co/bQY5XPL)
or maybe this one?

(https://i.ibb.co/2nxrX9B/anotherideagiver.jpg) (https://ibb.co/2nxrX9B)
Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on March 06, 2021, 09:32:26 PM
This curtain-ring-top collection is getting quite big!
I think there is only one more to come....

No, no, please don't stop! I'm enjoying these. That built-in elastic starter is pretty cool.
Title: Re: Curtain Ring tops
Post by: ortwin on March 07, 2021, 09:07:39 AM
fidget spinner wind up top
An improved version of the wind up top without curtain-ring can be found in this other thread (https://www.ta0.com/forum/index.php/topic,6392.msg69590.html#msg69590).
Title: Re: Curtain Ring tops
Post by: ortwin on March 13, 2021, 03:53:25 PM
Curtain-Ring-Top Nr. 9 - simple reversing top - shows its name, but then decides to change it!


(https://i.ibb.co/RNRzffW/CRT9.jpg) (https://ibb.co/RNRzffW)

Just a piece of wire from a paperclip roughly shaped into a figure 9 and stuck into a curtain ring.
https://youtu.be/YJ9rEtX1-0Y (https://youtu.be/YJ9rEtX1-0Y)

Since this one was not planned before today, there is at least another one to come that I had planned before. Some of you following my other posts of today might guess that there is also a plan for a multiple reversing curtain ring top. The first try on that was a fail, but I have ideas what should be improved. So if that works, there are two more curtain ring tops to come for now. But every day you guys seem to inspire new ideas, so we'll see.
Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on March 13, 2021, 05:17:12 PM
Curtain-Ring-Top Nr. 9 - simple reversing top - shows its name, but then decides to change it!
Just a piece of wire from a paperclip roughly shaped into a figure 9 and stuck into a curtain ring.

Since this one was not planned before today...

Excellent! You're a born modular topmaker!

One of the best things about quick prototyping is the ability to turn an impulse into a working top in short order. That often gets me farther than my best-laid plans.
Title: Re: Curtain Ring tops
Post by: ortwin on March 13, 2021, 06:09:40 PM
Curtain-Ring-Top Nr. 10 - multiple reversing top


(https://i.ibb.co/RPvntby/CRT10.jpg) (https://ibb.co/RPvntby)

The transparent bluish bead can freely slide along a wire fixed across the ring. The two solid blue beads ad some AMI. One part of the ring got some black marker on it so one can sometimes follow the flips.
https://youtu.be/0AVngQ67ADk (https://youtu.be/0AVngQ67ADk)

It is working somehow. Hard to see clearly, but I think in some of the spins it is visible that it really flips more then once.
Title: Re: Curtain Ring tops
Post by: ta0 on March 13, 2021, 06:24:24 PM
Very nice!
I love how on the normal tippe top it looks like the eye climbs the inner wall.  8)

There are some clear rapid flips on the flippe top around 0:35. By going frame by frame I can even see the bead falling on one of those. But it would be worth filming in slow motion.

You have achieved quite a bit using curtain rings!  8)
Title: Re: Curtain Ring tops
Post by: ortwin on March 15, 2021, 12:17:26 PM
Curtain-Ring-Top Nr. 11 - triple tribute top
(https://i.ibb.co/qYyWt9s/CRT11-1-material.jpg) (https://ibb.co/qYyWt9s)  (https://i.ibb.co/QDHKrTC/CRT11-3-spokes-in-hub.jpg) (https://ibb.co/QDHKrTC) (https://i.ibb.co/4Ygz24j/CRT11-4-spokes-hub-flywheel.jpg) (https://ibb.co/4Ygz24j)
(https://i.ibb.co/YQdXBJj/CRT11-finished-tip-side.jpg) (https://ibb.co/YQdXBJj) (https://i.ibb.co/h8Bth62/CRT11-finished.jpg) (https://ibb.co/h8Bth62) (https://i.ibb.co/JHLv5wV/CRT11-finished2.jpg) (https://ibb.co/JHLv5wV) 
It does not look much different then some other tops in this series. But there are some details about it that point to future metal (non curtain ring ) versions I am planning to build.
But lets get to the letters in the next pic:

(https://i.ibb.co/hHpMcPT/CRT11-2-material-letters.jpg)  (https://ibb.co/hHpMcPT)

T : spokes and needle are a tribute to ta0 who prompted this series by a remark about his guess on the longest running tops.
I :  the torus flywheel is a tribute to Iacopo and his tops of unsurpassed elegance.
J : the hub is a tribute to Jeremy - for obvious reasons if you can see it well in a close up.




The paperclip visible in the material picture ended up cut to little pieces of wire. Every piece stands for setscrew in metal tops to come later. The setscrews I am thinking of look similar to this:

(https://i.ibb.co/6PddBhK/setscrew.jpg) (https://ibb.co/6PddBhK)

The pieces of wire are marked with different letters in the following picture:

A : stands for the three setscrews that tension the spokes and center the tip
B : stands for the three setscrews that are used for static balancing of the top
C : stands for the three setscrews that are used for dynamic balancing of the top
(https://i.ibb.co/7Wbt2C2/CRT11-ABC.jpg) (https://ibb.co/7Wbt2C2)
The wire of the needle represents the 10th setscrew that enables the adjustment of tip height. 


https://youtu.be/t6-UDhIYLPY 
 (https://youtu.be/t6-UDhIYLPY)
The performance is not that great, but after all it is just build from plastic and all the possibilities for adjustment are more or less symbolic.I hope to see some improvement when turning to metal flywheels next. It wil not be heavy metal for starters, more like easy listening.





Title: Re: Curtain Ring tops
Post by: Jeremy McCreary on March 15, 2021, 06:50:15 PM
Curtain-Ring-Top Nr. 11 - triple tribute top...
The performance is not that great, but after all it is just build from plastic and all the possibilities for adjustment are more or less symbolic.I hope to see some improvement when turning to metal flywheels next. It wil not be heavy metal for starters, more like easy listening.

I'd call that a success! LEGO tip holder duly noted. Amazingly well centered and balanced considering all those paperclip fragments.

Your design goals seem to be headed in the direction of Maxwell's dynamical top (https://www.nms.ac.uk/explore-our-collections/stories/science-and-technology/james-clerk-maxwell-inventions/james-clerk-maxwell/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.
Title: Re: Curtain Ring tops
Post by: ta0 on March 15, 2021, 09:40:07 PM
Yes, great job using those materials!

Quote
T : spokes and needle are a tribute to ta0 who prompted this series by a remark about his guess on the longest running tops.
Well, I have somewhat changed my opinion. If tip friction was the limiting factor, this would be ideal. 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. It may be an inefficient use of the material to reach the desired moment of inertia but will probably provide the least air drag. Not good news to those wanting to make a top out of gold or platinum  ::)

Jeremy: great link to that picture of an original Maxwell dynamical top and the video from Aberdeen University Museum.  8)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 17, 2021, 03:54:54 PM
Preview of the first "follow up" to the curtain ring tops
Not that I think anybody is waiting anxiously for  the follow up, but I planned to have it ready by today and to present something.

The problem I ran into were the setscrews: I meant to drill small axial holes into three of them so I could thread my nylon spokes through those holes and secure them by knots.
But the screws I had, turned out to be too hard. I broke my 0.5 mm and my 0.6 mm drill on them. My friend with the lathe is going to make brass screws now for me, but that will take a few days until I get them.

So I just show the hub (the hex nut) and the one end of the three nylon spokes. They run through three holes I put into the nut and are secured by simple knots. The tip, a 4 mm ceramic ball from a ball bearing is glued with a drop of crazy glue to a setscrew. 
(https://i.ibb.co/BZWkytY/SONY-DSC.jpg) (https://ibb.co/BZWkytY) (https://i.ibb.co/SvBKG7d/SONY-DSC.jpg) (https://ibb.co/SvBKG7d)
See, I have the equipment to post better close ups than I usually do. ;)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 20, 2021, 06:15:02 PM
Curtain-Ring-Top Nr. 12 - The Link - soon to be called  "The Missing Link"
The transition in moving on from the plastic curtain ring tops to metal tops should not be tooooo hard and sudden. So this should be the link between the curtain ring tops and the follow ups. Of the "follow up" I showed a preview in the last post of this thread, it was basically the tip and the hub plus one end of the nylon spokes.  Since I still don't have those three special grub screws that I need for precisely centering the tip I am doing other stuff like this curtain ring top.
The flywheel I am going to use was a very lucky find a few days ago after I had the idea for it ready in my mind.
I saw that this part of old adjustable base I had made long time ago for some diamagnetic levitation experiment. It had already all holes in the right places where I needed them and almost all threads. So  that was easy, that is where the "easy" comes from in "easy listening", the name for the follow up.  It is made from aluminum and it is quite big, but the larger size makes setting up also somewhat easier.
(outer diameter: 90 mm, inner diameter: 68 mm, height 12 mm,  weight:  about 85 g )

(https://i.ibb.co/4Vcyf4C/Material.jpg) (https://ibb.co/4Vcyf4C) 
A curtain ring like the one used in the other tops of this series serves here as hub and as tip at the same time. Some inspiration came definitely from Jeremy's second batch of STs (suspension tops), mostly from what he calls  "Top 4", "Hercules wheel in chains".  There are also some strong features of "communication towers kept upright by guy lines" that Jeremy mentioned in the "Suspension Tops" thread.
 
(https://i.ibb.co/rxvMdbw/Curtain-Ring-Top-12-on-wood.jpg) (https://ibb.co/rxvMdbw) (https://i.ibb.co/NrjCSG3/Curtain-Ring-Top-12.jpg) (https://ibb.co/NrjCSG3)
(https://i.ibb.co/2jk8r2B/Curtain-Ring-Top-12-spinning.jpg) (https://ibb.co/2jk8r2B)
The following video shows actually the first spin of which I measured the duration. It ended after about 2 minutes I think. In the meantime I had a few spins with 2:45 abouts.
As I said there is still no precise centering possible here, so I did not bather to really balance anything here. Also the PING in the nylon is not  at the level I aim for. It is mostly just like what you can do with knots when doing your shoe laces.
https://youtu.be/YzGxFKhchZE (https://youtu.be/YzGxFKhchZE)
Bu what is that upper part of the curtain ring good for? Okay, I can spin by it as if it where a stem, but really .....
Lets just get rid of that half! Good bye my precious Curtain Ring!
(https://i.ibb.co/r5bCQKr/DSC-0015.jpg) (https://ibb.co/r5bCQKr)  (https://i.ibb.co/S3ZMJ3f/Curtain-Ring-Top-12-rigging.jpg) (https://ibb.co/S3ZMJ3f) rigging indicated in colors

At the beginning of this post I explained the "link" part of the name. Since the flywheel will soon be incorporated in the follow up that has no curtain ring, this top will not exist any longer and that's why I will soon call it "The Missing Link".

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 20, 2021, 10:24:32 PM
You cut off my last hope of a stem!!

Very interesting line rigging to hold the curtain ring upright. Surprised at how smoothly the top spins given that there are lines crossing between the curtain ring and tbe mirror.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 21, 2021, 03:39:05 AM


[size=78%]. Surprised at how smoothly the top spins given that there are lines crossing between the curtain ring and tbe mirror.[/size]


Ah, no. No  crossing between curtain ring and mirror. There are four tiny holes visible in the material picture in the curtain ring. I used the two central ones of those.
I should have made the rigging clearer. I might insert a clarifying sketch.



Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 21, 2021, 10:18:02 AM
You cut off my last hope of a stem!!
But  if I would have cut off a little less, you would have been left again with the two stems I designed for you before! :P
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 21, 2021, 12:40:47 PM
So the metal flywheel will ultimately be your starting torque input -- presumably with the two-hand shear method.

At my skill level, I think I'd need a good 10-15⁰ of scrape angle to get a fast, scrape-free release without a stem for fine tilt control.

If G = ground clearance with no tilt, and R = max flywheel radius at its base, then

CORRECTED: scrape angle = arctan(G / R) ~ 90°  45° G / R

to a very good approximation for G / R < 40% 90%.

Which brings us to ground clearance G. How much are you planning to get with the metal flywheel on the nut+bolt core with white tip?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 21, 2021, 03:18:24 PM
...
Which brings us to ground clearance G. How much are you planning to get with the metal flywheel on the nut+bolt core with white tip?
 

To me that sounds as if you took all the date I gave about the flywheel, put everything in the appropriate formulae and are ready to give me the ground clearance you would start with, what critical speed I can expect and what starting speed with the typical energy one can put into a twirl (Iacopo's numbers). That would be all very welcome, go ahead give me those numbers and if you dare even your estimate for spin time. I will go about it the playful way and play around with all the ten grub screws once I have it ready and try to get to the values you calculated as good as possible. If we get into the same ballpark with our values, both of us could call it a success. 

Should we get that far, a recalculation for  a flywheel made from brass with a square generator would be the next logical step. Either keeping AMI or mass the same. What new diameters would we get? What would the new, lower,  ground clearance be and what the new lower critical speed? What would we estimate as the spin  time, would we think its worth getting it build?

In my play-around approach, I plan to start with a ground clearance of about 5 mm with the option to change it either way by about 3 mm.





Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 21, 2021, 05:33:39 PM
I'm all for the play-around approach. No predicting spin time -- even for the simple geometry you're planning. Just wanted to raise a design issue I run into all the time...

At parity of air and tip resistances and top geometry other than CM height, you're often left with a tricky trade-off between scrape angle and the release speed you can attain without scraping.

Often, spin time is best served by upping the scrape angle so you can really crank on the top -- despite the resulting increase in critical speed. Where's the sweet spot? Test, test, test!
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 22, 2021, 03:45:17 AM
....No predicting spin time -- even for the simple geometry you're planning. ...
No prediction of spin time is fine, I can understand. But  starting speed should be easy. Also a simple plot of critical speed versus ground clearance of this specific flywheel. ( So if I think it is so easy and simple why do I not do it myself? Just because I am such a sloth or because I fear I will fail? No easy answer to this one.)

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 22, 2021, 11:00:29 AM
Clearly time for the tough love approach. You're on your own now, my friend. Looking forward to that plot! It'll be easy with the equations I've given you.

Now off to make a video having nothing to do with tops.

MfG, Jeremy
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 22, 2021, 11:50:21 AM
Now off to make a video having nothing to do with tops.
I know that doing something like that is possible! But is it worth it?
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 22, 2021, 12:02:50 PM
Have to admit, pretty scary.

But we must do the scary things to lead a rich and full life. Unless they kill you first.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 24, 2021, 12:45:37 PM
Pick a number!
Since I still don't have those specially made screws to connect the nylon string spokes to the flywheel for the top I am actually planning, I am just screwing around a bit with that (big) flywheel:


(https://i.ibb.co/hYQ05h1/one-spoke.jpg)  (https://i.ibb.co/2Wcggs8/one-spoke-spinning.jpg)  (https://ibb.co/hYQ05h1)(https://i.ibb.co/5YD2HM2/two-spokes.jpg) (https://ibb.co/5YD2HM2) Tau and Pi tops.
    (https://i.ibb.co/QjwGf7M/three-spokes-sideways.jpg) (https://ibb.co/QjwGf7M) (https://i.ibb.co/KKyD2js/threespokes-from-above.jpg) Mercedes top
 (https://ibb.co/KKyD2js) (https://i.ibb.co/9t92jJm/six-spokes-upper-side.jpg)   (https://ibb.co/9t92jJm)(https://i.ibb.co/hXLQTJq/six-spokes-bottom-side.jpg)  (https://ibb.co/hXLQTJq)(https://i.ibb.co/27vB29m/six-spokes-spinning.jpg)  (https://ibb.co/27vB29m) Waggon wheel top
 (https://ibb.co/hXLQTJq)
Just shows the versatility of that "found" flywheel. Better centering of the tip static and dynamic balancing would still be possible and also badly needed for good performance but for now I did not do any of that. Maybe once the suspension top with this flywheel is up I'll do it for comparing the performance of the different  spokes.
 
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on March 24, 2021, 01:19:23 PM
Quote
Tau and Pi tops.
;D ;D ;D

They look great. You made good use of the flywheel.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 24, 2021, 03:25:04 PM
Excellent! Basic flywheel dimensions? Which version spins longest so far, given current state of balance?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 24, 2021, 04:30:14 PM
Curtain-Ring-Top Nr. 12 - ....
....
(outer diameter: 90 mm, inner diameter: 68 mm, height 12 mm,  weight:  about 85 g )
...
 

In the meantime I centered/balanced a bit a further version. This version has three spokes. Starting speed 420 RPM gave a spin time of 8:35 toppling at around 100 RPM.
https://youtu.be/eJovDKG9wu8 (https://youtu.be/eJovDKG9wu8)
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 24, 2021, 06:28:31 PM
Almost 9 minutes! Nicely centered, too. Bravo!

The flywheel's aluminum and the screws are steel, correct?

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 25, 2021, 02:31:32 AM
....
The flywheel's aluminum and the screws are steel, correct?



Affirmative! And the steel ball (1/2 inch) tip comes from a GEOMAG set.

And yet another one: The PEACE TOP
(https://i.ibb.co/SRcN5Gc/peace-top.jpg)     (https://ibb.co/SRcN5Gc)

Edit: Oh, this last one was a bit of  misunderstanding: one of my inner voices screamed: "Please stop!" (meaning "stop making silly tops"). But my conscious self misunderstood it for "Peace Top". And this is what came from that...... 
But wait, how about a STOP TOP? Stop signs around here  are octagonal, would not work with this flywheels threads....

https://www.google.com/search?q=stop+sign&tbm=isch&sclient=img
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 25, 2021, 09:45:41 AM
In my experience, given how far gone you are already, if you have the parts to make more iterations of this top, you will.

Resistance is futile.
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on March 25, 2021, 10:57:25 AM
Quote
Edit: Oh, this last one was a bit of  misunderstanding: one of my inner voices screamed: "Please stop!" (meaning "stop making silly tops"). But my conscious self misunderstood it for "Peace Top". And this is what came from that...... 
;D ;D ;D

Quote
But wait, how about a STOP TOP? Stop signs around here  are octagonal, would not work with this flywheels threads....
Sure. It would only have half the sides of Jeremy's hexadecagonal top.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 25, 2021, 11:08:51 AM
Used this 8-sided flywheel in my original batch of suspension tops...

(https://i.ibb.co/hd8zjnV/20210313-224832.jpg)

Spins for ~60 s.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 25, 2021, 12:10:13 PM
In my experience, given how far gone you are already, if you have the parts to make more iterations of this top, you will.

Resistance is futile.


But it seems you are better off: in the LEGO world the number of possibilities is denumerable, otherwise possibilities are innumerable.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 25, 2021, 12:14:23 PM
Used this 8-sided flywheel in my original batch of suspension tops...

Spins for ~60 s.


So are you going to change the colors and call it STOP TOP ?


Edit: never mind. I just realized that I made the STOP TOP already. Curtain ring top Nr. 1 is called "period".
Another word for that would be "full stop". So, there you have it.

Some time ago, I was involved in the design of the STOP CUBE
 http://www.randelshofer.ch/rubik/virtual_cubes/rubik/picture_cubes/stop_cube_big.html (http://www.randelshofer.ch/rubik/virtual_cubes/rubik/picture_cubes/stop_cube_big.html)
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 25, 2021, 01:48:09 PM
Maybe so, but you've been making hardware store modular top construction work pretty well so far.
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on March 25, 2021, 02:06:47 PM
Some time ago, I was involved in the design of the STOP CUBE
 http://www.randelshofer.ch/rubik/virtual_cubes/rubik/picture_cubes/stop_cube_big.html (http://www.randelshofer.ch/rubik/virtual_cubes/rubik/picture_cubes/stop_cube_big.html)
Nice! At first glance I thought it was a trivial cube, but then I realized each little cube is unique and the difficulty is the same that for the original cube (actually more difficult as colors are easier to follow). Are you into cubing?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 25, 2021, 02:47:23 PM
... Are you into cubing?
Yes I would say so. But definitely not speed cubing. Sometimes solving, sometimes collecting, at other times modding (like the Stop Cube), sometimes thinking about some theoretical aspects. I hang out in the http://twistypuzzles.com/forum and admire what people come up with.

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 25, 2021, 03:07:08 PM
So are you going to change the colors and call it STOP TOP ?

Some time ago, I was involved in the design of the STOP CUBE
http://www.randelshofer.ch/rubik/virtual_cubes/rubik/picture_cubes/stop_cube_big.html (http://www.randelshofer.ch/rubik/virtual_cubes/rubik/picture_cubes/stop_cube_big.html)

I like gag tops, and your "stop top" idea is a good one.

Problem is, red solutions exist, but all come with other design departures I'm at best ambivalent about at the moment. So I'll keep red in mind as a future color scheme.

Very cool stop cube. Had to quit when my brain turned to jelly. Nicely stoplights spotlights your sadistic side, though.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 25, 2021, 04:37:44 PM
... At first glance I thought it was a trivial cube, but then I realized each little cube is unique and the difficulty is the same that for the original cube (actually more difficult as colors are easier to follow)....
   

Ah, sorry, can't let that go by like this. It is not completely wrong what you observed, but NOT "each little cube is unique" . The centers are all the same. In the original cube you have six different centers. Looking only at that point it would mean that the STOP CUBE has 24 times less positions then the original one.
BUT in the STOP cube the orientation of the centers is visible, four orientation for every center can be distinguished.  In the original cube the center orientation is not visible. If you put marks on the centers so you can distinguish their orientation the number of possible permutations increases by a factor of 1024 if I recall correctly. (Edit:it is 2048; (4^6)/2 )
If you weigh these factors correctly against each other you end up with more possibilities on the Stop Cube than on the original one. I forget by which factor  exactly, but If somebody is really interested, I could redo the calculation.
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on March 25, 2021, 07:17:19 PM
Ah, sorry, can't let that go by like this.
Au contraire. I love it.
I forgot about the centers. It's an interesting complication.
I know that you cannot rotate a single cube in the normal Rubik without also rotating at least one (or two) more. I wonder if that's true for the center cubes or not.

EDIT: I noticed that there are actually two different types of center cubes, 3 with the wording parallel to the side of the cube and 3 at 45 degrees.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 26, 2021, 02:21:09 AM


EDIT: I noticed that there are actually two different types of center cubes, 3 with the wording parallel to the side of the cube and 3 at 45 degrees.



Now you are the one who is right! Yes, there are some details like the one you mention I forgot about, I just typed what I thought I remember. That with the two types of centers works towards the Stop Cube regarding the number of permutations. With the centers you can  rotate a single one, but if you want to rotate a single one without changing anything else, it has to be a 180 degree rotation.  But the proof for that fact is a bit longer than two lines I think. That leads to the factor 2048 ((4^6)/2 ) for the so called "supercube" in comparison to the normal cube.


Here is the link to where I presented the Stop Cube amongst others.
http://twistypuzzles.com/forum/viewtopic.php?f=15&t=33350&p=379854&hilit=Stop#p379854 (http://twistypuzzles.com/forum/viewtopic.php?f=15&t=33350&p=379854&hilit=Stop#p379854)
Here  (https://twistypuzzles.com/forum/viewtopic.php?f=1&t=18534&p=225922&hilit=supercube#p225922)are some ways I found to make supercubes from normal cubes. Other people found different ways long before me.

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on March 26, 2021, 02:43:14 AM
So when are we going to see a twisty puzzle top?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 26, 2021, 03:01:29 AM
So when are we going to see a twisty puzzle top?
I have one of these (https://speedcubeshop.com/products/qiyi-1x3x3-spinner):

video (https://youtu.be/KI6KxEjOga4)
 
I could convert it to a wind up top similar to the one I showed before.But that would not be all the way: I like magnets, spinning tops and twisty puzzles (and of course some other things).But what is a good way to put all three together? Magnets are often used these days in twisty puzzles, so that is trivial. The fidget spinner cube I can turn into a spinning top, easy. Levitrons are magnetic tops, old. But how to put all three together that makes some sense? Of course it is possible to put some magnets in a Fidget Cube Top, but not really useful or really funny. I wait a bit longer until inspiration hits me.

Title: Re: Curtain Ring tops + follow ups
Post by: the Earl of Whirl on March 26, 2021, 05:38:06 AM
That looks like lots of fun.  I know some people who would go crazy over this!!!
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on March 26, 2021, 10:10:12 AM
Well, this is a fidget spinner I might be interesting in getting. But perhaps a tip and stem mod is in order . . .  ;)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on March 26, 2021, 10:21:24 AM
Well, this is a fidget spinner I might be interesting in getting. But perhaps a tip and stem mod is in order . . .  ;)


Only if you include the wind up starter and show a video of it here!
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 03, 2021, 05:53:45 PM
Easy Listening on bottle cap with recessed tip.

https://www.youtu.be/8BmOLwAvf3c (https://www.youtu.be/8BmOLwAvf3c)

With this I got a spin time of 15:08 

"Edit: Update, 04.04.2021 - Spin time 19:05 - some basic centering and balancing did much. This is my best time I reached with any top so far."

The tip is not perfectly centered yet, I did not find a good way how to do it. So I didn't even bather to balance it, because the reflecting surface for the laser method is also a bit poor.
On a large concave mirror (tip not recessed in that case) I had it spinning for 8:51, but then I tried to make improvements centering the tip and tensioning the spokes - the a nylon spoke  broke,  I could not get it back to that time with protruding tip. So I moved to this recessed tip for now.

Still want to find a better rigging method and a material suited better for spokes. Might take a trip to the fishing supply store next week - if it is not closed to to a Corona lock down.

Looked at that video again: almost by chance, it resembles the von Braun space station parking close to the orbit of Saturn ..........

 
 
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 03, 2021, 08:07:41 PM
Excellent! I'd say you're well on your way to your stated goal. And with the epitome of a suspension top, no less!

Q: Any idea how far the contact is below the top's overall CM (including core) when on the bottle cap?

Careful, the cops on Saturn love to give out parking tickets.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 04, 2021, 06:26:48 AM
Q: Any idea how far the contact is below the top's overall CM (including core) when on the bottle cap?
Hard to say, somewhere between one and two millimeters ?
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 04, 2021, 11:34:39 AM
Still want to find a better rigging method and a material suited better for spokes.

The thiinest guitar string? Takes a lot of tension with little stretch.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 04, 2021, 12:17:58 PM
Still want to find a better rigging method and a material suited better for spokes.

The thiinest guitar string? Takes a lot of tension with little stretch.


Yes, but at the same time I have to find a way to fasten the ends. Currently I make a knot in the nylon string. Like in that picture of the hub I posted earlier in this topic. 
(https://i.ibb.co/BZWkytY/SONY-DSC.jpg) (https://ibb.co/BZWkytY)
Still need to find out if such little knots are possible with wire, or if there are even better possibilities. SUGGESTIONS ARE WELCOME!
Title: Re: Curtain Ring tops + follow ups
Post by: the Earl of Whirl on April 05, 2021, 12:40:20 AM
Here is a picture of guitar strings.  It shows the end that is secured at the bottom of the guitar, nearest the sound hole.  Would this “knot/hub” do the trick?  If so, it is not too hard to take the pieces and put one on the other end of the string.


(https://i.ibb.co/m68wfN6/90515655-8-B04-4858-8117-A184-F4-B409-FB.png) (https://ibb.co/m68wfN6)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 05, 2021, 02:49:06 AM
Here is a picture of guitar strings.  It shows the end that is secured at the bottom of the guitar, nearest the sound hole.  Would this “knot/hub” do the trick?  If so, it is not too hard to take the pieces and put one on the other end of the string.
Thanks, keep those ideas coming!
This one is very big in comparison to a tiny knot in a 0.3 mm nylon string. Remember, if I go from this aluminum flywheel to brass or to something with even higher density, things become smaller still.
Also, as I do the rigging at the moment, the line is under some tension already while I apply the securing knot on the second end. That doesn't help of course putting it at a precise position.

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 06, 2021, 03:14:51 PM
The Easy Listening Top was fun, I will still continue to give it a spin, but the major development with it I consider done.
I learned something about some problems that are specific to suspension tops and hope I can use those findings for improvements in the next top.
I think I want to move from Easy Listening to Brass Band music.  I tried different ways of arranging the lines, every way had its problems, the position and the angle where the threads in the flywheel are, need to be modified for a next version.

Best results with Easy listening: on concave mirror: 9:51 , on dedicated base with recessed tip 19:05.
Moving to brass keeping the mass of the flywheel and AMI constant, I dream of 20 minutes on a concave mirror and over 30 minutes with the recessed tip.

This last rigging became a bit complicated, a sign to move forward I guess.


(https://i.ibb.co/j4sJ9gg/SONY-DSC.jpg) (https://ibb.co/j4sJ9gg) (https://i.ibb.co/YddpdZg/SONY-DSC.jpg) (https://ibb.co/YddpdZg) (https://i.ibb.co/4sgDFRS/SONY-DSC.jpg) (https://ibb.co/4sgDFRS) (https://i.ibb.co/7RLngz7/SONY-DSC.jpg) (https://ibb.co/7RLngz7) (https://i.ibb.co/McyWMCf/SONY-DSC.jpg) (https://ibb.co/McyWMCf)

Yes, as you can see in the video, there is an A-side and a B-side to Easy Listening.

https://youtu.be/DLnGT0wQ5Ms (https://youtu.be/DLnGT0wQ5Ms)

In playing around with the recessed tip and the dedicated base, I came to think that those are not necessarily features my tops are not allowed to have. After all, all those concave mirrors are also quite special bases and also a lot larger/heavier/more expensive than that simple bottle screw cap I used. I don't know for sure yet, so I will probably make tops that can do both modes. The possibility of longer spin times is of course also tempting.
 




Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 06, 2021, 06:27:53 PM
Best results with Easy listening: on concave mirror: 9:51 , on dedicated base with recessed tip 19:05.
In playing around with the recessed tip and the dedicated base, I came to think that those are not necessarily features my tops are not allowed to have.

Don't worry, checked with Mistress von Karman. She said that as long as the top's overall CM is above the contact in operating configuration, you can have those features.

But she's watching you!
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on April 06, 2021, 08:01:33 PM
Those are great times for Easy Listening!

You are very good at making good tops out of common things you find around.

I look forward to Brass Band!
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 06, 2021, 09:42:35 PM
What ta0 said.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 07, 2021, 09:07:45 AM
...
You are very good at making good tops out of common things you find around.
...
Thank you. That is a very polite way to say that my tops look shabby.
But that is alright, the Levitrons I build usually also did not look that great at first, but with the last  one, you see in my first post here in the forum I am happy.  That means I still hope that one of these ugly ducklings I presented so far will turn one day into a sleeping beauty.
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on April 07, 2021, 10:26:13 AM
Thank you. That is a very polite way to say that my tops look shabby.
On the contrary! I'm amazed how good they look!
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 07, 2021, 10:59:55 AM
Thank you. That is a very polite way to say that my tops look shabby.
On the contrary! I'm amazed how good they look!
Ah, this fishing for compliments is still working  ;) .
But now I started thinking about the Brass Band. First thing I noticed, was that "Band" also has a meaning that makes a bit of sense in this context here. 
Good enough.
Then I measured the starting speed of "Easy Listening". I got it up to around 600 RPM which is about the same of what I can do with the modified Euler disk weighing 440 g and having a diameter of 75 mm.
That leads to the question of the dimensions of the flywheel for Brass Band : Should it be the same dimensions as Easy Listening ? Or should I keep the mass and AMI constant? It is far from clear for now for me what would be the best. Gut feeling tells me to go with a square generator of 8 by 8 mm and an outer diameter of 80 mm. Somehow in between.
Still guesswork, maybe I should calculate AMI of three square generators within reach and then decide somehow from there.  Ans better suggestions from the crowd?






Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 07, 2021, 01:25:18 PM
@ortwin: I'm not familiar with the ergonomics of your starting method, but you might make some wooden dummies to see what diameter gives the fastest release speed. Since your aerodynamics are pretty much set, you could then focus on minimizing critical speed using a spreadsheet and the formulas I gave you.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 10, 2021, 03:37:15 PM
Availability helps deciding! I received the brass ring on the right in the photo today. I want to try to turn that into "Brass Band".
(https://i.ibb.co/QFYb7y0/quartercurtaineasybrass.jpg) (https://ibb.co/QFYb7y0)

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 10, 2021, 05:53:01 PM
Availability helps deciding!

Tell me about it -- the curse of modular topmaking!

Really looking forward to Brass Band.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 12, 2021, 03:37:19 AM
"Kindergarten Brass Band" 
(https://i.ibb.co/WkFPr3p/Kindergarten-Brass-Band-1.jpg) (https://ibb.co/WkFPr3p) (https://i.ibb.co/CJ8jjsy/Kindergarten-Brass-Band-2.jpg) (https://ibb.co/CJ8jjsy)
Just a quick update, because I am so surprised and excited that "Brass Band" was able to beat "Easy Listening" that quick and effortless, even in this Kindergarten version:
On the concave mirror base it spun already on its second timed run for 11:40 . Where Easy Listening was struggling to get to 9:50 .
No holes made into the ring, no screws. Only strings attached. The two 0.3 mm nylon strings hold some arbitrary bead (glass or plastic?) from my daughters jewelry kit more or less in the center. The brass thingy visible in the center, is just clamped there between the lines. Its function is to push the bead down a bit to have sufficient ground clearance. The rigging is similar, but not identical to the wedding band top of reply #20 in this topic.
https://i.ibb.co/gMhfwCt/Curtain-Ring-Top-Nr-7b-2.jpg (https://i.ibb.co/gMhfwCt/Curtain-Ring-Top-Nr-7b-2.jpg) 
I can't even tell you what my starting RPM was because I did not apply the reflector tape yet.
The bead can easily be pushed around, that is how I tried to align it with the center.  But it is not very stable and satisfying to do the adjustments this way, so there will be more versions to come.
Edit/Update: reflector applied, starting at 500 RPM, toppling after 10 minutes at 84 RPM.
https://youtu.be/2liqEhLR4dM (https://youtu.be/2liqEhLR4dM)




Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 12, 2021, 01:37:08 PM
A truly elegant top. And a great performer, too! Brass Band is my favorite by far — even in prototype. Well done!
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on April 12, 2021, 04:15:25 PM
I cannot believe that you can keep the lines tense and centered to get it balance enough for close to a 12 minutes spin! No drilling, cutting or gluing! :o
Good work!
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 13, 2021, 03:55:04 AM
I cannot believe that you can keep the lines tense and centered to get it balance enough for close to a 12 minutes spin! No drilling, cutting or gluing! :o
...

Keeping the lines tense is not so hard, but I can make it sound  complicated:
Knot two ends of line together so that you get a loop with a circumference a bit less than four times the radius of the brass ring.  :-\ ??? :-[
Pull this loop over the diameter of the brass ring. Here you make use of the fact that nylon can stretch. 
Do the same thing with a second piece of nylon line, this time you push it over the diameter of the ring at a 90 degree angle to the first one.
You end up with crossed pretty stiff spokes if you chose the length of the lines correctly.
But this is the point when you realize that you forgot to put the bead at its place where it can serve as tip.
So you start all over again with new nylon string (after you convinced yourself that there is no topological way to get the bead where you want it to be without breaking the loops. This might take a while though, and YOU might even find a way, if so then tell me please!).
So you thread the bead on the two strings, knot them to loops, and so on. 


Balancing I did by pushing the bead to whatever direction the top was leaning to, when sitting on a flat, leveled surface. It is still moving quite easily on those strings, even if they are cross and tensioned - of course too easy for good stability sometimes. Still, I had spin times of over 12 minutes in the meantime.



Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 18, 2021, 10:43:40 PM
ortwin inspired me to try a LEGO spoked flywheel top with a metal ring for the flywheel. Best attempt so far...

(https://i.ibb.co/Kzgr4Vr/20210418-165300.jpg)

The welded stainless steel ring has a mass of 62 60 g and inside and outside radii of 40 and 46 mm, resp. The LEGO parts in the red 4-spoke ring carrier brought the top's total mass to 75 g. Centering the ring securely was the hard part.

Best spin times with the red carrier were quite disappointing: Only 110 s by hand and 125 s with the 1:16 overdrive starter above. And with the yellow 3-spoke carrier below, they were ~5 s worse! Without the metal ring, these carriers stayed up 2 s at most.

(https://i.ibb.co/4ttKy7n/20210418-165427.jpg)(https://i.ibb.co/zVPvzR8/20210418-170011.jpg)

Once I installed the round red spoke weights at far left below, the red version wobbled very little at high speed. But a significant low-speed wobble remained. Balancing the top with the yellow carrier was less successful.

(https://i.ibb.co/bWZ5QPp/20210418-170142.jpg)

Wow, knew spoke drag could be bad, but not that bad!

Based on ortwin's spin times with Brass Band, expected to get at least 300 s here. Instead, I got 125 s at best. Two lines of evidence point to severe spoke drag as the main culprit:

1. Release speeds were ~600 RPM by hand and ~1,300 RPM with the starter. Yet the starter bumped spin time by only 14%. Only one thing can chew up added release speed like that: Severe air resistance.

2. CM height was ~14 mm in the red carrier and ~22 mm in the yellow. Should have been a big spin-time advantage for red, but the added drag produced by its extra spoke largely offset that advantage.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 19, 2021, 01:35:30 AM
Really nice! Looks very like StarWars.
Also your post gives me additional arguments to push my coworker towards the thin nylon spokes - he is favoring metal rods.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 19, 2021, 01:50:02 AM
Really nice! Looks very like StarWars.

Thanks! Really bummed about the spin time, though. What are the specs on your brass ring?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 19, 2021, 02:56:13 AM
...
Thanks! Really bummed about the spin time, though. What are the specs on your brass ring?
I really would have guessed five to six minutes spin time would easily be possible when I first saw your ring.
But as I heard someone say again and again:  "spin time is not everything"! Now who said that again?
You are right, I really forgot to give the details on my brass ring, very sorry about that. Depending on the mood of our kitchen scale it weighs in at 119 g up to 124 g.  Inner diameter ~77 mm, outer diameter ~93 mm. Height ~8 mm. 


Would it not be possible to build it so that the spokes are above, not below the ring? CM would be further down.
You could also try to get rid of most of that stem stuff, 600 RPM can be reached by gripping the metal ring.If none of this can be done, you could still build it like my "Kindergarten Brass band". Maybe you could use your wedding band as tip with a different rigging. With that you wouldn't need a spacer as I did. I did not try my wedding band as tip because it is concave.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 19, 2021, 10:34:47 AM
But as I heard someone say again and again:  "spin time is not everything"! Now who said that again?

OK, OK, you got me there. Maybe I should have said that I was shocked and horrified that spoke drag is really that bad. Two minutes is a good but not great spin time by LEGO standards.

Thanks for the specs. Your metal ring has WAY more AMI than mine about twice as much AMI as mine.

Would it not be possible to build it so that the spokes are above, not below the ring? CM would be further down.
You could also try to get rid of most of that stem stuff, 600 RPM can be reached by gripping the metal ring.

Yes, all good suggestions and easily done. The stem was at worst a minor offender, but I'll try paring it down.

Seldom mentioned fact: Adding a little TMI by beefing up a stem can reduce residual wobble with little adverse effect on CM height. Hence the beefy stem here.

Funny, Plan A was to use gravity and friction to hold the ring in place. Worked pretty well, too. But sometimes the ring would turn out of alignment with the balancing weights during spin-up.

Hence the little white elastics. Why I failed to go the next step and flip the rotor upside down once gravity was no longer needed is beyond me. ::) (This forum really needs a dope-slap emoji.)

Let's see what happens with these tweaks before abandoning a LEGO ring carrier altogether.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 19, 2021, 11:28:04 AM
...

Let's see what happens with these tweaks before abandoning a LEGO ring carrier altogether.
You could use nylon fishing line, and one of those LEGO helmets as tip. Would that still satisfy your LEGO contract?
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 19, 2021, 01:26:32 PM
You could use nylon fishing line, and one of those LEGO helmets as tip. Would that still satisfy your LEGO contract?

May well end up there, but I have a few more intermediate steps to try, as my doctrine of selective impurism requires.

This iteration stays up 146 s by hand, a 33% improvement.

(https://i.ibb.co/ngpcTj8/20210419-100125.jpg)

To balance the top with this yellow 3-spoke ring carrier, had to resort to using a small metal washer as a balancing weight.  Wobble's now minimal at high speed but still unacceptable at low speed, suggesting significant residual unbalance rather than flexure as the cause. Wobble's a big turn-off for me, so not done yet.

(https://i.ibb.co/GQkKSk8/20210419-100150.jpg)

Ground clearance below the ring and elastic are now 4 and 3 mm, resp. CM height ~ 10 mm -- a 29% reduction from last time's lowest.

At my current proficiency with stemless starts, I get the fastest scrape-free release speeds with this small residual 2-torque stem.

The Zen Index, however, is now unacceptably low. With scrape angle down to 4°, generally takes 4+ tries to get a fast scrape-free start with the stem and several more without. Very frustrating when you just want to bask in the gyroscopic zen of it all.

As the great Zen masters remind us,

Scape and wobble, yuck!
Spin time isn't everything
Chant previous line

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 19, 2021, 02:14:05 PM
... scrape-free start ....
Maybe I did not read these unwritten rules often enough, do they really ask for a "scrape-free start" ?
Am I doing everything wrong?
If there is a bit of scraping for the first two seconds or so, that is not a completely lost run in my book. I just start the stopwatch after the last scrape I hear and stop it again at the first one I notice. The scraping takes away a lot of speed so I try to avoid it but not for "spiritual" reasons.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 19, 2021, 05:53:50 PM
@ortwin: You have a very rational view of scrape during spin-up. Not wrong, just to your own taste.

Over the years, my best spin times have consistently come when scrape is gone. Doubt it's just a LEGO thing, but LEGO construction could make it worse. I attribute this correlation more to reduced release speed than to energy lost to transient wobble, but it could be some of both.

Hence, I've become more than a little scrape-phobic. And using a stem to improve tilt control generally helps me avoid it. However, have to concede that a practiced hand might get faster stemless releases by allowing some scrape beforehand.

Question is, which path is ultimately faster? Which excites less transient wobble? Which delivers the longest spin times? And which the most play value?

Who knows? Let's do some tests.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 19, 2021, 11:18:57 PM
This latest ortwin-inspired iteration is squarely in skimpy suspension top (http://www.ta0.com/forum/index.php/topic,6432.0.html) territory: Just the stainless ring, some low-mass, low-stretch kite string, and 4 g of LEGO parts (including the white elastics) for a total mass of 64 g.

(https://i.ibb.co/Yhvkgn8/20210419-183555.jpg)

The 330 s spin time by hand is up 127% from last time (Reply #100). Still nowhere near the 700 s ortwin got with his Brass Band top (Reply #90), but much closer to my hope for a LEGO-enabled top deriving most of its AMI from a low-drag metal ring.

(https://i.ibb.co/KGCq3br/20210419-190017.jpg)

Unchanged since last time: Ground clearances under the ring and elastics, a very tight 4° scrape angle, and a CM height of ~10 mm. Though much thinner than I usually use for high-AMI tops, had to resort to the 3.2 mm stem to maintain CM height. (It's a LEGO thing.)

(https://i.ibb.co/jfpHV87/20210419-190903.jpg)

After 2+ hours and several rounds of rigging and balancing, was ready to give up on getting wobble down to an acceptable level. Then it just happened. No idea how.

(https://i.ibb.co/b3CdBwf/20210419-183347.jpg)

Under blacklight, the white kite string fluoresces nicely in blue. The bright RBG markers around the stem were for a variant of the paintbrush balancing method. No help balancing this top, turned out, but I like the way they mix to white at speed.

(https://i.ibb.co/sq3y0CB/20210419-191026.jpg)



Conclusions: The HUGE gain in spin time since Reply #100 must be largely aerodynamic, as critical speed and tip resistance changed little.

Intuitively, I think that if the spokes are a few thin needles, their drag will be negligible. Still, the optimal radius of the wheel and it's shape are things that have to be determined.

Lookin' pretty good here, ta0! The data accumulated in this thread clearly shows that a suspension top (http://www.ta0.com/forum/index.php/topic,6432.0.html) with a large AMI and very thin lines can make a decent endurance top.

This top's a definitly keeper. The long spin time takes some of the sting out of the annoying scrape angle, and I like the way it looks -- especially under blacklight. But if it were ever to lose its balance, not sure I'd put in the work to get it back.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 20, 2021, 02:55:49 AM
....330 s spin time by hand is up 127% from last time (Reply #100). Still nowhere near the 700 s ortwin got with his Brass Band top (Reply #90), ...
CONGRATS! Very well done! Even better when considering the AMI disadvantage (factor two roughly?) you had to cope with.
The black light pictures are very cool. Did you get to filming "Skimpy String Top" in the same black light session?

In one of the pictures it looks to me as if you had used only one string and one knot. I had thought about that possibility, but found it too hard to balance with that setup. It is of course a lot easier if you can tension/position the different spokes somewhat independently.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 20, 2021, 03:07:37 AM
...
...a practiced hand might get faster stemless releases by allowing some scrape beforehand.

..
Just a note on the spin up technique  I am using at the moment with "Easy Listening" and "Brass Band".
I grip the ring at the outside with all my five fingers of the (right) hand. I find I get best results when my arm is stretched downward. So I put the base with the top on the floor and either bend over it or sit on a chair next to it. Trying to start them on a table I find I have less control and speed.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 20, 2021, 03:30:03 AM
CONGRATS! Very well done! Even better when considering the AMI disadvantage (factor two roughly?) you had to cope with.
The black light pictures are very cool. Did you get to filming "Skimpy String Top" in the same black light session?
In one of the pictures it looks to me as if you had used only one string and one knot. I had thought about that possibility, but found it too hard to balance with that setup. It is of course a lot easier if you can tension/position the different spokes somewhat independently.

Thanks! Yes, just one continuous string, but no knots. When the rigging's complete, the ends of the string pass through 2 adjacent holes in the lower black disk forming the core. They're fixed to the disk by jamming the studs on those translucent 1x1 plates into these holes. That way, I can pop out the appropriate plate and re-rig as needed -- e.g., to replace the elastic that's about to break-- without having to remove the whole string. Then I can re-tension, lock the freed end of the string back down, and re-center. As you found, the last is much easier said than done.

You and Iacopo have kept me too busy to shoot the skimpy all-chain blacklight top. Decided to show it along with some other blacklight tops made since my last video on this subject. Have the stills under visible light (to reveal at the end), but no video yet.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 26, 2021, 04:12:29 AM
 Primary Brass Band
 Since “Kindergarten Brass Band” is gone out to get some nice piercings and stuff, and wants to come back as some sort of “Junior Brass Band”, its elder sibling took its chance to show off:
 So here is, “Primary Brass Band”!

(https://i.ibb.co/phk8ZSp/SONY-DSC.jpg) (https://ibb.co/phk8ZSp) (https://i.ibb.co/SVM6d41/SONY-DSC.jpg) (https://ibb.co/SVM6d41) (https://i.ibb.co/M88dZy8/SONY-DSC.jpg) (https://ibb.co/M88dZy8)

Still no holes or anything in the flywheel,
home build. The length-adjustable-brass-spokes are tightened with nylon line to the flywheel as well as to the central hub borrowed from “Easy Listening”.  It is still a real suspension top by the definition of Jeremy I would say. The knotting of nylon lines was not so easy for me. The knots I made first, slipped, opened, broke… You know, I am not into fishing or such. Finally I found knots on the internet that worked for my purpose.
 Now I do not even need a screwdriver to center the tip, just turn the spokes with the fingers. The spokes are actually tensioning screws. They come from a model building supply. My guess is, that they are usually used in building models of ships.
 The balancing is still interdependent on the centering of the tip. Meaning that I can normally not adjust both precisely at the same time. Still I reached some very good spin times already, with the best time of 18:36 in normal mode. By normal mode I mean the tip is not recessed, it spins on a slightly concave surface larger than the top.
 It is possible to have it spin in recessed mode on something like a bottle cap, but I have not timed any spin in that mode. What is also still lacking in this “Primary Brass Band” version is a reflective surface that could be used for the laser balancing method.


The times are better then my best times with the “Spartan Top” or the “Quark top”.
So I am happy with how this is developing and I am having hopes of even longer spin times with further improved versions on the way.


(https://i.ibb.co/jhRwB52/Primary-Brass-Band.gif) (https://ibb.co/jhRwB52) click to animate

 
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on April 26, 2021, 09:55:09 AM
You beat the Spartan top!  :o I wasn't expecting that! 18:36!  :o 8)

I cannot believe that you made it just by tying fishing line and no drilling.  ::)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 26, 2021, 10:04:27 AM
You beat the Spartan top!  :o I wasn't expecting that! 18:36!  :o 8)

I cannot believe that you made it just by tying fishing line and no drilling.  ::)


Well, in the nut that makes the hub, are 3 small holes I made with a 0.6 mm drill. The hub I used for "Easy Listening" before.
Once I break the 20 minutes barrier I will post a video of a full length spin, before that maybe not.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 26, 2021, 11:15:43 AM
Wow, 18:36 with mostly solid spokes! Looks good, too.

How thick are those turnbuckles at their widest?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 26, 2021, 02:17:50 PM
...
How thick are those turnbuckles at their widest?

"Turnbuckle", nice word, seems to be the correct technical term for what I am using.
3 mm at their widest.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 26, 2021, 06:26:53 PM
Depending on the mood of our kitchen scale it weighs in at 119 g up to 124 g.  Inner diameter ~77 mm, outer diameter ~93 mm. Height ~8 mm. 

Just to confirm, the 18:36 spin time was with the brass ring above?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 27, 2021, 01:30:21 AM
Depending on the mood of our kitchen scale it weighs in at 119 g up to 124 g.  Inner diameter ~77 mm, outer diameter ~93 mm. Height ~8 mm. 

Just to confirm, the 18:36 spin time was with the brass ring above?
Affirmative!
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on April 30, 2021, 04:02:08 PM
Maybe I should ad a stem after all?
I am seriously considering adding a stem to a future version of "Brass Band" (I know Jeremy, you thought that all along).
The thought came to me after I dared comparing my results to a top of Iacopo: Nr. 26
On his YouTube channel he has a video up where I took this screenshot is from:

(https://i.ibb.co/xD3Hst6/iacopo-26-28.jpg) (https://ibb.co/xD3Hst6)
Nr. 26 has just very roughly similar dimension and weight as my "Brass Band". With quite some effort I get it to start at about 500 RPM. From that point I had it running 18:36. Now if I look at the screenshot, Nr. 26 spins for roughly the same time after it is down to 500 RPM. So it seems at least two data points are comparable in Iacopo's and my top! That would mean the main difference is the starting speed? Nr. 26 ran already for about 11 minutes when down to 500 RPM, starting at around 1250 RPM.
So why can I not reach those speeds? Some quick experiments with the flywheel of easy listening (90 mm diameter, 85 g) convinced me that it is easier to reach higher speeds with a stem! So I will try to ad a (detachable) stem in one of the next versions.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on April 30, 2021, 09:12:11 PM
Handy way to assess the spin time changes you can expect from a given change in either release or critical speed in a given top:

Δt = t2 - t1 = T1/e ln(ω1 / ω2)

where (t1,ω1) and (t2, ω2) are any 2 points on a purely exponential spin decay curve (SDC) such that t2t1, and ω1ω2. The "lifetime" T1/e is the time needed for the top to lose 63.2% percent of any given starting speed.

NB: All times should be in seconds, but the speeds can be in either rad/s or RPM as long as they have the same units.

First measure any 2 (time,speed) points (t1,ω1) and (t2, ω2) for the top of interest. Then rearrange the formula to determine its lifetime T1/e. Then do the what-ifs with the formula as written above.

Case 1: Your current release speed is ω2, but you hope to increase it to ω1.
Case 2: Your current critical speed is ω1, but you hope to reduce it to ω2.

Note that when you double release speed or halve critical speed, ω1 / ω2 = 2, and ln(ω1 / ω2) = ln 2 = 0.693. So either way, you'll extend spin time by 0.693 T1/e seconds. For example, if T1/e = 1,000 s (on the low side for a classic Simonelli), then doubling release speed or halving critical speed will add 693 s.

If you'd rather think in half-lives instead of lifetimes, the conversion is

T1/2 = T1/e ln 2 = 0.693 T1/e
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 04, 2021, 02:36:49 AM
A sneak preview of JBB (Junior Brass Band)
JBB sent  a picture so I would know how it looks like when it comes back,  and how much "Kindergarten Brass Band" changed since it left.

Promising I'd say!
(https://i.ibb.co/nwLYR04/JBB-preview.jpg) (https://ibb.co/nwLYR04)


Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 06, 2021, 04:16:33 AM
Primary Brass Band
 ....
The times are better then my best times with the “Spartan Top” ...
The Spartan fought back!
It managed to spin for 27:45   (Edit 32:02  in another try).
But it was disqualified for cheating badly! Should be lucky that it is not banned for lifetime!
It was done in vacuum.
(https://i.ibb.co/dW6fRT9/vacuum-detail.jpg) (https://ibb.co/dW6fRT9) (https://i.ibb.co/thqQCqL/vacuum-overview.jpg) (https://ibb.co/thqQCqL)
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 06, 2021, 10:46:36 AM
JBB looks great! Eager to see it in action. Spartan can be forgiven for getting desperate.
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on May 06, 2021, 12:20:08 PM
Nice!  8)

I guess you have to spin it and then rush to cover it and pump out the air as fast as possible. It should be possible to start one inside a vacuum chamber using magnets. My idea would be to have the top hanging from the chamber ceiling because of a rotating spinning magnet above. The top would either have a magnet or a non circular stem so as to rotate with the driving magnet. After it reaches the necessary speed, you take away the external magnet and the top falls on the surface.

I would like to have a vacuum setup. Perhaps one day . . .
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 06, 2021, 03:18:31 PM
JBB looks great! Eager to see it in action. Spartan can be forgiven for getting desperate.
Since I asked for some "ad ons" and some little changes it will be at least another week until it comes back.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 06, 2021, 03:32:50 PM
...
I guess you have to spin it and then rush to cover it and pump out the air as fast as possible. It should be possible to start one inside a vacuum chamber using magnets. My idea would be to have the top hanging from the chamber ceiling because of a rotating spinning magnet above. The top would either have a magnet or a non circular stem so as to rotate with the driving magnet. After it reaches the necessary speed, you take away the external magnet and the top falls on the surface.

I would like to have a vacuum setup. Perhaps one day . . .
Yes I have to do it like you suspect. There surely are different ways to start tops in a vacuum chamber. I would like purely mechanical ones best, but then again why exactly would you want  that?
With Something like "top secret" you can start the top, then close the vacuum chamber while the base sits outside and drives the top until you pumped down as far as you like (or can do it) . After that you can observe how it spins down when you take away the base.

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 07, 2021, 03:09:18 AM
Since this is the happenin' place for toroidal tops, my latest, in bronze and blue...

(https://i.ibb.co/4JnD906/20210505-101308.jpg)

If I pack all 5 metal rings downward in their hangers before twirling, this top spins ~30 s by hand without visible wobble. Pretty happy with that considering the rotten aerodynamics and all the opportunities for unbalance.

(https://i.ibb.co/FDVm70R/20210505-101201.jpg)(https://i.ibb.co/G5jPXgN/20210505-101222.jpg)

Compared to the stainless ring I used before (left), the bronze rings are significantly smaller in all dimensions. The stainless ring has 4 times the AMI of the 5 bronze rings put together, and its top spins 11 times longer due to the added AMI, a much lower CM, and much cleaner aerodynamics.

But to give the bronze rings their due, note that their low-AMI, high-drag plastic "chassis" stays up a mere 1 s by itself. By adding many times the AMI of the chassis alone and reducing CM height from 33 to 25 mm, the rings greatly reduce critical speed.

I think the rings are also likely to reduce air resistance. If so, then the added AMI further reduces the slope of the top's spin decay curve from release to fall. Result: A 30-fold increase in spin time.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 07, 2021, 03:40:01 AM
Since this is the happenin' place for toroidal tops, my latest, in bronze and blue...

(https://i.ibb.co/4JnD906/20210505-101308.jpg)
...


Super cool photo !


Will you submit this to our contest?
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 07, 2021, 11:13:15 AM
Super cool photo !
Will you submit this to our contest?

Thanks! The chance of a non-throwing top winning is slim to none, but why not?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 07, 2021, 11:38:08 AM
...The chance of a non-throwing top winning is slim to none, but why not?
Let me tell you, winning is not everything !  ;)
But maybe it would make our corner of the forum more visible to the "sports section"?
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 07, 2021, 11:51:46 AM
But maybe it would make our corner of the forum more visible to the "sports section"?

Good point! I like "sports section".
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 17, 2021, 10:35:58 AM
Update on Junior Brass Band:  "comeback postponed - important part of my friends lathe broke"  :'(

That lathe is probably older than the oldest member in this forum, so replacement parts need to be specially manufactured.  :(

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 30, 2021, 06:42:22 AM
The return of JBB (Junior Brass Band) - Listen up!
https://youtu.be/Kss7hw6yaEA (https://youtu.be/Kss7hw6yaEA)
There is still a little part missing, but the main components are there.
Being at the age it/she/he is at, it is probably normal to have an identity crisis.
"Am I a stemless top? Do I want to be a top with this stem and a ballpoint pen tip or do I prefer this other one?"

(https://i.ibb.co/ScqK3KY/stemless-JBB.jpg) (https://ibb.co/ScqK3KY) (https://i.ibb.co/rpgCh7R/stem-and-ball-point-pen-tip.jpg)  (https://ibb.co/rpgCh7R)(https://i.ibb.co/MpyL1ZD/JBB-with-stem.jpg) (https://ibb.co/MpyL1ZD) 
Via the screw spokes the tip can be centered. The nuts on the spokes are for (static) balancing. At the moment centering and balancing needs still to be worked on, but I wanted to post this update first.
The best time so far with this version (stemless) is 18:44. So already a small improvement of 5 seconds in comparison to an earlier version. I am quite confident that when I can get rid of most of the wobble times of over 20 minutes are realistic.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 30, 2021, 12:02:40 PM
Wow, looks and sounds great, and 18 mintes is very impressive.

Love the stem options. Eager to see time trials with and without! Which of the 2 stems feels better for single twirls?
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on May 30, 2021, 12:50:49 PM
You seem to have a Simonelliesque flair for detail. I wonder where this path into ring tops will take you . . .  ;)
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 30, 2021, 01:06:10 PM
Rats, wanted to look at the details of this beauty, but the security app on my phone says they're on a "suspicious site".
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 30, 2021, 03:00:21 PM
You seem to have a Simonelliesque flair for detail. I wonder where this path into ring tops will take you . . .  ;)
Thank you, that is a very big compliment. Although I am not sure what detail exactly you mean. There really is not much. The screws/spokes are stainless steel, there were none available in brass. The nuts for balancing are not so great looking I think. I consider having same changed for round brass parts that are longer so they can manipulated just by the fingers.
The hub, yes that is were I asked for it to have about the same curvature as the flywheel ring. The ring itself has now a flattened top and bottom. I hope I can use that area for some laser balancing.The stems don't fit in the whole design package so far, at this point they are basically just to check  if they improve over all performance.

Wow, looks and sounds great, and 18 mintes is very impressive.

Love the stem options. Eager to see time trials with and without! Which of the 2 stems feels better for single twirls?
The smaller thin stem that is knurled does not feel great. That was one I never asked for though. The larger stem has a much better feel to it. I wanted it that flat on the outside. I will try applying sand paper to it for better grip, or a piece of rubber/silicon hose that fits.
With the stemless version I reached 520 RPM to start with and after those 18:44 it fell with 90 RPM.
With the bare larger stem (same scraping angle) 630 RPM at start, after 17:18 falling with about 93 RPM.
As a base I used that large concave mirror that came with the original Euler's Disk.
So besides the centering and balancing the stem business can use some improvement. The stem surface, its length and its diameter need optimization. With less than 750 RPM at the start I will not be happy.The one part that is still missing, is a longer axle to which that ceramic ball is glued. It should be so long that its upper end is flush  with the upper end of that larger stem. Since the stem screws on the axle, I will be able to vary the stem length from about 2.5 cm to 4.5 cm (there will be a counter nut). That range should be  enough to find a good value for the stem length.




Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on May 30, 2021, 03:49:49 PM
It took 86 s to spin down from 93 to 90 RPM??

For a given top, higher release speed should yield longer spin times -- unless the longer stemless spin in this case just happened to hang in a metastable state between spinning down through critical speed and actually falling. It happens.

Nice that you can swap out stems, cuz the only way to optimize stem diameter, length, and texture for this particular top is to test, test, test.

A Simonelli-like low-density stem would have less of an adverse effect on critical speed.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on May 30, 2021, 05:09:55 PM
It took 86 s to spin down from 93 to 90 RPM??
...

No, no, with the stem it seems to lose its speed faster over the whole range. I can't prove that with data I recorded and I do not know why exactly but I suspect that more wobble with the stem leads to a faster loss of energy. Of course I also expected longer times with the higher starting speed using the stem - especially after I saw that critical speed did not go up by so much - BUT it turned out to be different! Maybe we should not try too hard to explain this, since no proper balancing was performed for these cases, differences could also stem from that side?

..
A Simonelli-like low-density stem would have less of an adverse effect on critical speed.
The effect on critical speed does not seem to be sooo bad. With all the runs I performed over the last two days, I would judge it to worsen only by about 6 RPM on average.  The Simonelli low density stem would not make such a big difference: It is solid wood, but my brass stem is hollowed out.

I think the main thing for me should be the centering, balancing and thereby wobble reducing adjustments.Just before I applied some sand paper wrapped around  that stem with double sided sticky tape. I really had one start at around 730 RPM, so a big improvement there, but it "only" led to 18:29.  The big problem in this specific run was the sand paper: one end came a bit off the stem so it could act almost like a braking parachute!

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 02, 2021, 08:03:49 AM
More than 20 minutes 


(https://i.ibb.co/VVXzhSW/past-20-minutes.jpg) (https://ibb.co/VVXzhSW) 
JBB did it!
Now I have to film it as I promised I would, once I get passed the 20 minutes.
 
Before this, I got very very close to 20 minutes with  quite a few tip and stem configurations. 
The one I used here has a 4 mm ceramic ball as tip and a short stem.
Starting at 698 RPM taking 20:16 until the first scrape on the very slightly concave base with about 90 RPM left.
If you should be interested in further details you can either hope I will mention some in that video to come ( I did not film this run, need to get another one past 20 on film), or just ask directly, which will prove faster I think. 
The balancing is still poor, still need to tackle that more seriously. Up to now it is a bit of laser balancing, a bit of a kind of paintbrush method, a bit of just changing something and check if that is an improvement. But I followed none of these methods with  a real strategy up to now.
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on June 02, 2021, 11:16:02 AM
Wonderful! Congratulations in achieving your goal. But I bet you now have a new goal post    >:D

Maybe one day I'll have an ortwin ring top in my collection   ;)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 02, 2021, 11:26:12 AM
...Congratulations in achieving your goal. But I bet you now have a new goal post    >:D

...
Not really, looking back at the post where I stated my goals (http://www.ta0.com/forum/index.php/topic,6392.msg69155.html#msg69155) . 25 minutes is the goal with this type of top. 20 minutes was for a modified commercial top, so maybe I get the Spartan with prostetics one day to do it.
Title: Re: Curtain Ring tops + follow ups
Post by: Iacopo on June 02, 2021, 01:54:23 PM
More than 20 minutes 


You made a nice top, Ortwin, I like it.
It is so simple, essential, and still it allows you to fine tune both the balance and the centering of the tip.
It's an intelligent design, bravo !
 
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 02, 2021, 02:36:47 PM
...
You made a nice top, Ortwin, I like it.
It is so simple, essential, and still it allows you to fine tune both the balance and the centering of the tip.
.....
Thank you Iacopo, yes,  it turned out very versatile. I think I mentioned somewhere that also different stems can be used and tips can easily be exchanged for one of different material or radius . The contact point position can be moved from far  external to recessed,  even spindulum (non top) mode is possible when a needle tip is used as a base and the concave surface of a grub screw as the counterpart in the "top".
So what I want to say by all that, if I don't get lost with all the possibilities I see chances to reach my 25 minutes goal with this top. If neccessary with dedicated base and/or recessed tip. The three of you (Jeremy, ta0, Iacopo) will hopefully continue to share their experiences, ideas and knowledge, thereby making valuable contributions to my progress towards my goals. - But really its the discussions we are having, the little and sometimes large diversions, the possibility to share ideas - all that is, I think,  of more value than the goals themselves expressed in just simple numbers.

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 02, 2021, 06:34:00 PM
JBB spinning for 20:02 https://youtu.be/YCSvrZDLTtQ (https://youtu.be/YCSvrZDLTtQ)
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on June 03, 2021, 01:19:53 AM
I will withold all congratulations and further compliments until you've reached your 25-minute goal.

But really its the discussions we are having, the little and sometimes large diversions, the possibility to share ideas - all that is, I think,  of more value than the goals themselves expressed in just simple numbers.

Diversions? On this forum? Surely you jest!

I like seeing and hearing about tops of all kinds.  And I really like the many e-friends I've made here. But it's the exchange of ideas around topmaking that I enjoy the most.
Title: Re: Curtain Ring tops + follow ups
Post by: Iacopo on June 03, 2021, 02:06:31 AM
Ortwin, in the video you bended a sapphire crystal with a sucker to make it slightly concave ?
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 03, 2021, 04:29:36 AM
Ortwin, in the video you bended a sapphire crystal with a sucker to make it slightly concave ?
No, Iacopo, I am not at the sapphire stage yet. Actually I don't even find those sapphire protectors I talked of before any longer on the net.
This is just an arbitrary touchscreen of an old and broken tablet computer. I must admit I do not even know what its surface is made off. Glass?
But yes it is made slightly concave with vacuum.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 03, 2021, 11:46:54 AM
21:46 - after some more serious centering. Up to now I had left the centering screws alone, at the setting they were put at using the lathe. Now I took it apart  and reassembled it. Adjusted the centering after the tip was fixed in place. Just pulled the tip towards the side it was leaning to. But as we learned in the "offset top" topic, centering the tip is not that important in itself.  So some more fine adjustment with the balancing nuts. 
This time I used that short knurled stem that is directly fitted to a ball point pen tip of unknown material. So the stem I said would not feel good, turned out to work very good after all!

Start with 700 RPM, scrape around 100 RPM. But still room for improvement. One minute at the starting end with speed I achieved before with top. Another minute at the lower end, I've seen it topple at 90 RPM. And another minute in between, it is still not spinning very smoothly.


Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on June 03, 2021, 12:14:36 PM
Step by step inexorably advancing to your goal.  8)
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on June 03, 2021, 01:52:24 PM
You're getting there!

Have you tried a flat spinning surface? My tops generally spin longer that way.

For one thing, a concave surface reduces effective scrape angle for a given ground clearance. And Hertzian contact theory suggests that a concave surface might generate more tip resistance, all other things being equal.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 03, 2021, 02:44:01 PM
...
Have you tried a flat spinning surface? My tops generally spin longer that way.

For one thing, a concave surface reduces effective scrape angle for a given ground clearance. And Hertzian contact theory suggests that a concave surface might generate more tip resistance, all other things being equal.
The curvature is very small really. But for safety reasons I want some curvature. If it should start to wander off, I don't want to interfere during the spin (not legit).
But I said before that I am preparing a post on that base. I prepared some of the text but I need to make more different pictures and maybe short (Q&D) videos.  But I am going slow there, maybe because bases are not as sexy as tops?
Since you are kind of asking I can as well talk about it a bit here:
The topic will be called "My VACU-MO-VACU  base". Just a bit shorter than "My variable curvature modular vacuum base". 
So by setting the vacuum, choose different surfaces, different sealing rings and so on I can influence the curvature I have.  It seems also possible to have it completely flat in the center area with safety curbs toward the outside. That would serve both purposes, right?At the moment though, that does not seem to be the limiting factor. I think that because I get quite similar results with different tip diameters and material.  I might do an experiment with a different hardened glass used as protective screen cover.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on June 03, 2021, 03:50:52 PM
The curvature is very small really. But for safety reasons I want some curvature. If it should start to wander off, I don't want to interfere during the spin (not legit).
But I said before that I am preparing a post on that base. I prepared some of the text but I need to make more different pictures and maybe short (Q&D) videos.  But I am going slow there, maybe because bases are not as sexy as tops?
Since you are kind of asking I can as well talk about it a bit here:
The topic will be called "My VACU MO VACU  base". Just a bit shorter than "My variable curvature modular vacuum base". 
So by setting the vacuum, choose different surfaces, different sealing rings and so on I can influence the curvature I have.  It seems also possible to have it completely flat in the center area with safety curbs toward the outside. That would serve both purposes, right?At the moment though, that does not seem to be the limiting factor. I think that because I get quite similar results with different tip diameters and material.  I might do an experiment with a different hardened glass used as protective screen cover.

Well, you're so close, and all you can do now is nibble away at the small opportunities for improvement. So a flat surface would seem worth at least few tries without assumptions. All you have to lose are the test runs. Just lay a cord inboard of the edge of the table as a safety fence and bring a book.

Besides, with the smaller ball tips, the tendency to travel might be pretty minimal to begin with.

Wow, that "variable curvature modular vacuum base" sounds pretty clever! But knowing how much ta0 enjoys a good acronym, I'd just go with VCMVB. Has a nice rhythm to it.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 04, 2021, 12:04:52 PM
.... So a flat surface would seem worth at least few tries without assumptions. All you have to lose are the test runs. Just lay a cord inboard of the edge of the table as a safety fence and bring a book.

Besides, with the smaller ball tips, the tendency to travel might be pretty minimal to begin with.
...
I gave it a few tries on a flat area, no clear difference to spot yet. Little differences i  other parameters seem to matter more at this point.
 
The stemless version seems to be back in  business:  not a record, but 20:23  . Starting at 573 RPM scraping at around 80 RPM.

Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on June 04, 2021, 12:42:53 PM
Interesting variability in your speeds at first scrape.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 04, 2021, 01:53:58 PM
Interesting variability in your speeds at first scrape.

Since balancing is not perfect and not exactly the same each time, plus the scraping angle varies and also the distance from contact point to CM, it is not THAT surprising.
Well, I guess that is what you get for free if that many adjustments and changes are possible in a modular system.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 07, 2021, 10:55:45 AM
JBB 22:57
 
(https://i.ibb.co/q7R2dzP/22-57-close-up.jpg) (https://ibb.co/q7R2dzP) (https://i.ibb.co/NC2C8Rm/22-57-overview.jpg) (https://ibb.co/NC2C8Rm) (https://i.ibb.co/bmhXw9k/22-57-table.jpg) (https://ibb.co/bmhXw9k) 
 
You can see that I took the balancing nuts off. That is certainly not why the time improved, but I got it balanced pretty good only by adjusting the spokes. In fact I don't think balancing could be much better now. Since there was some luck involved getting to that point, I think I won't touch those screws for a few days now. Critical speed is now consistently 71 +/- 1 RPM.
Visually it is still not running perfectly smooth. The reason for that is, that the stem is not perfectly at a right angle to the plane of the ring. But that does not seem to hurt much, the principal axis of inertia is running through the contact point, and that is the main thing!
Now that JBB is running stable, I could test different surfaces. I have different concave mirrors, that touch screen from a tablet computer, the bottom of jars, jar lids, bottle caps. As lube I used that "forehead lube" recommended here in the forum. The tip is a 4 mm (white) ceramic ball from a ball bearing.
And I was surprised to find these big differences: On most "good surfaces" it took about eight minutes to spin down from 170 RPM to 72 RPM when it toppled. But one little (only very slightly ) concave mirror stood out, here it took a whole 2 minutes longer!
With that one I got that 22:57. It is visible in the photo sitting on a larger mirror that has  a blue frame. The problem is to get the top to high starting speeds on this small area. It is not so much the scraping that is the problem, the problem is that if it has too much tilt or lateral speed upon release, it will wander off the mirror: the brass ring will touch the rim of the mirror and the run is over. So with the setting as it is, I get get to about 600 RPM spinning stable on the little mirror, with lets say trying ten times, but on different surfaces I had it already running for two minutes when speed was down to 600 RPM.
That means for me that I look around for larger surfaces that behave as well as that specific mirror. If I get those two extra minutes at the high speed end, a goal is reached.
Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on June 07, 2021, 11:32:12 AM
Wow, only 2:03 away from your goal!

I've also found that not all glass is created equally when it comes to tip resistance. No clue why or how to tell the good stuff short of testing.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 08, 2021, 06:16:37 AM
JBB 24:05
(https://i.ibb.co/28DksQx/SONY-DSC.jpg) (https://ibb.co/28DksQx) (https://i.ibb.co/pj4g9Nk/SONY-DSC.jpg) (https://ibb.co/pj4g9Nk)
No substantial changes done to the equipment this time. The improvement in spin time came mostly from the the higher starting speed. It must have been about 650 RPM. I could not get a good measurement of speed in the first few seconds. When speed was down to 600 RPM, the clock (and the top) was running for 48 seconds already.
I will try bit further, before I change much with the top itself. Maybe I get a lucky start with more than 750 RPM !
Title: Re: Curtain Ring tops + follow ups
Post by: ta0 on June 08, 2021, 09:17:07 AM
You almost reached your goal of 25 minutes! You can already put the champagne in the ice bucket.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 08, 2021, 09:39:31 AM
It will not be champagne! I promised myself as reward, that I will order that "Recording laser Tachometer" that Jeremy reviewed in the other topic.
And of course I start thinking of how I tackle the next obvious goal: nylon spokes again? 0.7 mm tungsten carbide ball as tip? Recessed tip?
Title: Re: Curtain Ring tops + follow ups
Post by: Iacopo on June 08, 2021, 12:32:24 PM
JBB 24:05


This is a very good spin, better than 23:56, which is my longest spin on a glass surface, (brass, single twirl and external tip).
But I use glass rarely, I almost always spin on tungsten carbide spinning surfaces.
 
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 08, 2021, 02:04:34 PM
IACOPO: Maybe one of these days I will ask you for advice on how to get that tungsten carbide surface, or maybe we can make some deal and you send me one.
But before that I try with different glass, hardened glass as in display protectors or even sapphire if I can get hold of something reasonable.



Title: Re: Curtain Ring tops + follow ups
Post by: Iacopo on June 08, 2021, 04:09:32 PM
IACOPO: Maybe one of these days I will ask you for advice on how to get that tungsten carbide surface, or maybe we can make some deal and you send me one.

I buy tungsten carbide rods, diameter 5 mm, which I cut in pieces and attach to my inox steel horns. 
I use a diamond ball bit diameter 8 mm for to shape the concavity in it, then I polish the surface with diamond pastes.

(https://i.imgur.com/exa0A4Q.jpg)
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 10, 2021, 02:44:49 AM
With what I have now, I will not get past the 25 minutes.  :( The glass surface of that small mirror that gave me the best times, is deteriorating faster than I can improve the starting velocity! Small scratches accumulate and that slows  down my top faster. 
 
But let me quote Jeremy : "Spin time is not everything." and: "The good news is:" That type of mirror is still available and it is not expensive. So if I get another one and prepare it with the knowledge I gained with the current mirror, this top configuration might still prove suited to spin longer than 25 minutes.

...

I've also found that not all glass is created equally when it comes to tip resistance. No clue why or how to tell the good stuff short of testing.

Maybe that is the case, but with my equipment it could also just be that the different glass surfaces experienced different wear: That little mirror, my best performer, I have hardly ever used until a week ago. The other surfaces I compared it to, had to endure a lot of spins already by than. So that could be an explanation of the differences and also why the performance differences become smaller now.
I am looking forward to get another new mirror of the same type as well as to some display covers that I ordered: Those claim to be scratch resistant, "hardness 9", but no sapphire yet.
We will see, I mean I will see and then report for you to read.



Title: Re: Curtain Ring tops + follow ups
Post by: Jeremy McCreary on June 10, 2021, 12:14:04 PM
Hardness 9 sounds like a good idea, because digging or drilling into the support during the spin could be a more important contibutor to total tip resistance than simple sliding friction or rolling resistance.

Concave lenses are also good sources of glass concave surfaces. They're very precise and, if coated, could be quite scratch-resistant. The longer the focal length, the smaller the curvature.

Best of all, if the diameter of the lens is significantly smaller than the rotor's, the lens will just be a pedestal, and your scrape angle and spin times will increase accordingly.
Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 10, 2021, 02:53:23 PM
...
Concave lenses are also good sources of glass concave surfaces. They're very precise and, if coated, could be quite scratch-resistant....
Yes I saw you use those concave lenses sometimes. I could not get a hold of one up to now. Maybe if I manage to take that old large camera lens apart, I can find a concave lens in there. But up to now it does not want to be opened with my unsuited tools. And I do not really want to use saw and hammer!
The coating is usually for the minimization of reflection losses, not for hardness or scratch resistivity, so it could be counter productive.  That is also why usually sapphire glasses of watches are only anti-reflection coated on the  inner side.

 
...
Best of all, if the diameter of the lens is significantly smaller than the rotor's, the lens will just be a pedestal, and your scrape angle and spin times will increase accordingly.
That is how that mirror you see in replies #155 and #153 acts already. And it is important to get those good times. Ultimately I want to reach my goals without that helpful "pedestal" or "dedicated base" effect, but for now it would be fine with me.  By the way, the contact point in those runs is about 2 mm downwards from the lowest point of the ring.

Title: Re: Curtain Ring tops + follow ups
Post by: ortwin on June 16, 2021, 06:08:48 AM
No further improvement.
JBB lost its almost perfect balance, and I was not so lucky this time in re-establishing it.
I got a few more (new) mirrors and a protective smartphone cover as base surfaces, I have different lubes that I can try, I improved the stem so I could even start it with more than 800 RPM - but all that is nothing  if you want more than 25 minutes and the balance is poor.
 The problem might be one that can not be solved with this version of the top, maybe only  another lucky punch in setting it up is possible.
The skew stem, with respect to the ring, is where I think the main problem is. Plus the direction of where the stem/tip is pointing to, changes every time I twist one of the centering crews/spokes with the screwdriver. That means I still do not have enough independent control of the settings in the top: it seems I need to be able to control both, the position of the axle as well as the direction it is pointing to.
I will try that in a next version with the aluminum flywheel of "Easy Listening" using six adjustable nylon spokes. But I doubt the spokes will be stable enough to allow for a good fast start by a stem.