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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)
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@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.
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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.
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I think that curtain-ring top is clever and fun. Good work!!!
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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.
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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.
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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.
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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.
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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.
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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.
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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?
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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?
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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!;-)
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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.
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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.
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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).
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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.
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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.
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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.
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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.
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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.
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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?
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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.
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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!!!
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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.
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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)
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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
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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.
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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)
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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.
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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).
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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.
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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.
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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.
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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)
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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.
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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.
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Yes, great job using those materials!
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)
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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. ;)
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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".
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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.
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[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.
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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
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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?
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...
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.
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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!
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....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.)
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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
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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?
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Have to admit, pretty scary.
But we must do the scary things to lead a rich and full life. Unless they kill you first.
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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.
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Tau and Pi tops.
;D ;D ;D
They look great. You made good use of the flywheel.
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Excellent! Basic flywheel dimensions? Which version spins longest so far, given current state of balance?
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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)
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Almost 9 minutes! Nicely centered, too. Bravo!
The flywheel's aluminum and the screws are steel, correct?
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....
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
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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.
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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
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.
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Used this 8-sided flywheel in my original batch of suspension tops...
(https://i.ibb.co/hd8zjnV/20210313-224832.jpg)
Spins for ~60 s.
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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.
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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)
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Maybe so, but you've been making hardware store modular top construction work pretty well so far.
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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?
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... 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.
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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.
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... 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.
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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.
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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.
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So when are we going to see a twisty puzzle top?
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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.
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That looks like lots of fun. I know some people who would go crazy over this!!!
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Well, this is a fidget spinner I might be interesting in getting. But perhaps a tip and stem mod is in order . . . ;)
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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!
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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 ..........
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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.
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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 ?
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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.
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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!
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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)
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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.
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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.
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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!
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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!
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What ta0 said.
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...
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.
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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!
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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?
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@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.
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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)
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Availability helps deciding!
Tell me about it -- the curse of modular topmaking!
Really looking forward to Brass Band.
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"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)
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A truly elegant top. And a great performer, too! Brass Band is my favorite by far — even in prototype. Well done!
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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!
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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.
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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.
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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.
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Really nice! Looks very like StarWars.
Thanks! Really bummed about the spin time, though. What are the specs on your brass ring?
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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.
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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.
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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?
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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
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... 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.
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@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.
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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.
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....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.
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...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.
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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.
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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
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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. ::)
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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.
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Wow, 18:36 with mostly solid spokes! Looks good, too.
How thick are those turnbuckles at their widest?
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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.
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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?
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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!
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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.
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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 t2 ≥ t1, and ω1 ≥ ω2. 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
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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)
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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)
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JBB looks great! Eager to see it in action. Spartan can be forgiven for getting desperate.
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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 . . .
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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.
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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.
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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.
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Since this is the happenin' place for toroidal tops, my latest, in bronze and blue...
(https://i.ibb.co/4JnD906/20210505-101308.jpg)
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Super cool photo !
Will you submit this to our contest?
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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?
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...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"?
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But maybe it would make our corner of the forum more visible to the "sports section"?
Good point! I like "sports section".
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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. :(
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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.
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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?
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You seem to have a Simonelliesque flair for detail. I wonder where this path into ring tops will take you . . . ;)
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Rats, wanted to look at the details of this beauty, but the security app on my phone says they're on a "suspicious site".
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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.
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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.
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It took 86 s to spin down from 93 to 90 RPM??
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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!
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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.
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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 ;)
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...Congratulations in achieving your goal. But I bet you now have a new goal post >:D
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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.
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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 !
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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.
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JBB spinning for 20:02 https://youtu.be/YCSvrZDLTtQ (https://youtu.be/YCSvrZDLTtQ)
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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.
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Ortwin, in the video you bended a sapphire crystal with a sucker to make it slightly concave ?
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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.
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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.
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Step by step inexorably advancing to your goal. 8)
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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.
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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.
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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.
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.... 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.
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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.
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Interesting variability in your speeds at first scrape.
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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.
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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.
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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.
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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 !
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You almost reached your goal of 25 minutes! You can already put the champagne in the ice bucket.
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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?
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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.
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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.
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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)
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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.
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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.
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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.
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...
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.
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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.
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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.
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JBB 24:08
(https://i.ibb.co/HXGzyVj/SONY-DSC.jpg) (https://ibb.co/HXGzyVj)
Only a very marginal improvement by three seconds over the previous best with this top in reply #155.
Start with 668 RPM, first scrape at 86 RPM.
As in reply #145, I used the short knurled stem directly fitted with the ball point pen tip. Although the starting speed and total time is very similar to my old best run, the spin down curve is quite different. In this run I lose about two minutes at the low RPM end, but that time was made good over the total rest of the RPM span.
One of those plastic curtain rings that I so often used before as flywheel, made an appearance here as part of the pedestal:
(https://i.ibb.co/s31py0H/SONY-DSC.jpg) (https://ibb.co/s31py0H) (https://i.ibb.co/4WcMmTJ/SONY-DSC.jpg) (https://ibb.co/4WcMmTJ)(https://i.ibb.co/fN3S93H/01pedestal.jpg) (https://ibb.co/fN3S93H)
The balancing nuts I use here are different from the ones I used before. I can adjust them now easily with my fingers, no need for tools. But they really seem to cost some time: when I had them close to the ring noticeable more even. That is why I moved them towards the stem. That observation leaves hope for further improvement when moving to thin lines as spokes... we will see.
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A very handsome top -- especially in that first photo!
Is this time with lube and multiple twirls?
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almost there: JBB 24:48
Difference: some more balancing, starting speed a bit higher, 702 RPM, topple at 86 RPM
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JBB 25:04
Finally it got past the 25 minutes! In the end it took a mixture of patience, determination, luck and desperation to finally reach that goal.
Started at about 720 RPM and toppled at 85 RPM.
I instantly ordered that "Recording laser Tachometer" it costs me about € 43,- and should arrive by Tuesday. So I really hope I can post a spin decay curve of more than 25 minutes by the end of next week.
It became late, so no more pictures or details today. But the next goal (half an hour) is clear, and I know of a few steps that should bring me towards it.
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Congrats at achieving your goal! :D
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When someone pursues a clear goal with determination, there is a good chance of achieving it.
Congrats!
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Excellent! You first hatched this project shortly after joining the forum. And now it's reached a major milestone. With a recording tachometer to show for it.
Doesn't get much better than that.
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Yes, congratulations!!! You are tops!
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JBB 25:04
Better and better. Bravo, Ortwin !
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Thank you everybody for the congratulations!
Thank you also for the suggestions and inspirations you gave me for reaching this goal.
But I feel I have given too little credit up to now to "Mr. H." who did the work at the lathe. Not only that, he also supplied his ideas not only as ideas but already made to work: like that knurled stem with the ball pen tip directly attached, that finally did the trick. I never asked for it to be made that way, I even disliked the feel of it at first, but now it lead to my best performing top (so far). Thank you.
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SUPER GREAT SPIN TIME
BRAVO
jim
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Is this time with lube and multiple twirls?
Forehead lube.
I can't do multiple twirls. The top has jumped off the table those few times when I tried.
I would need a totally different stem for that. So I prefer to play in the single twirl league - I would not stand a chance in Iacopo's multi twirl league anyways.
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Some technical details: Total weight of JBB for the 25:04 spin 132 g. The contact point is 2 mm below the lowest point of the flywheel.
And a video I made after that 25:04 spin:
https://youtu.be/dr56UAQABMY (https://youtu.be/dr56UAQABMY)
Questions on further details are welcome.
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A most elegant top, my friend.
Enjoyed watching the dynamics of the prolonged fall. I see the same style in my tops with low critical speeds: A series of quick dips between small and large tilts in progressive directions, a brief recovery to 0° tilt, repeat.
The transition between dead sleep and this mode is often quite abrupt. This may mark point at which critical speed is actually crossed, but hard to say.
In the absence of whirl due to unbalance, it should be possible to resolve this periodic instability into a series of precessions and (cuspidal?) nutations, but I often have a hard time seeing it that way.
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And a video I made after that 25:04 spin:
https://youtu.be/dr56UAQABMY (https://youtu.be/dr56UAQABMY)
When I want to cancel the precession, I blow against the stem of my tops in the instant when they are tilted towards my left, this makes them rise in sleeping position. In the past I used to kick the stem of the top with a pencil but now I feel that blowing is more gentle and accurate, so this has become my habit.
I observed the wobble of your top spinning slowly. I believe that at the beginning you have a mix of the three basic wobbles together, (precession, unbalance and nutation), because the wobble is irregular, (a kind of wobble I like to observe). Later, the wobble becomes more regular, and intermittent, which tells that there is the superposition of two basic wobbles. My gut tells me that these two basic wobbles are nutation and unbalance, while precession seems disappeared. With a slow motion I could judge this for sure.
The presence of unbalance wobble doesn't mean that the balance of the top is not good; at the decreasing of the spin speed, the top becomes more and more sensible to unbalance, and the unbalance wobble becomes more and more evident, and at very slow speed even a top with good balance wobbles at least a bit because of unbalance. Practically there is always at least a tiny bit of residual unbalance in spinning tops, it is impossible impossible to eliminate it really completely, in this real world.
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...
When I want to cancel the precession, I blow against the stem of my tops in the instant when they are tilted towards my left, this makes them rise in sleeping position. In the past I used to kick the stem of the top with a pencil but now I feel that blowing is more gentle and accurate, so this has become my habit....
I need to try that blowing, but with my short stem it might not work as well as with your longer stems. Also it matters which technique is faster or rather costs less RPM. Of course I start the stopwatch only after the last interference with the top.
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I observed the wobble of your top spinning slowly. I believe that at the beginning you have a mix of the three basic wobbles together, (precession, unbalance and nutation), because the wobble is irregular, (a kind of wobble I like to observe). Later, the wobble becomes more regular, and intermittent, which tells that there is the superposition of two basic wobbles. My gut tells me that these two basic wobbles are nutation and unbalance, while precession seems disappeared. With a slow motion I could judge this for sure....
It surely is interesting and rewarding to understand how the wobble is happening and which part is which, but the way it behaved in that video is not typical for an endurance spin: precession I try to get rid of as good as possible in the beginning, nutation should also have gone long before the slow period - that should leave only unbalance with your comments related to that part. Maybe I manage to get a video at the same time with a good speed decay curve from the "Recording laser Tachometer" of a >25 minute spin. I try not to take the top apart until then.
In some of my latest experiments I got the impression, that the 1 mm ball pen tip is somewhat less sensitive to the surface it spins on than the 4 mm ceramic ball tip. And generally the friction is lower with the small ball pen tip, but the topple speed is higher which costs around two minutes.
Did I gather that correctly Jeremy and Iacopo that those are also experiences you made?
I want to continue to explore the route with the ball point pen tips. My question for you is, which ball size do you think is most promising?I found there are mines available with 0.3 mm , 0.7 mm, 1.0 and 1.2 mm diameter tungsten carbide ball tips. To check all sizes in depth seems a bit much.
And another question to you Iacopo: How do you know in a top that unbalance is not only good, but almost perfect? What tells you that it is not worth trying to balance a top better still? There must be something more then "oh I am tired of all this tedious balancing, I just say that this is the best possible balancing."
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On my 25:04 spin I recorded the data for the spin down curve by hand still:
|
| RPM | t |
| ~720 | 00:00 |
| 650 | 00:42 |
| 600 | 01:21 |
| 550 | 02:03 |
| 500 | 02:54 |
| 400 | 05:00 |
| 300 | 08:06 |
| 200 | 13:07 |
| 190 | 13:48 |
| 180 | 14:30 |
| 170 | 15:16 |
| 160 | 16:05 |
| 150 | 16:59 |
| 140 | 17:57 |
| 130 | 19:02 |
| 120 | 20:11 |
| 110 | 21:26 |
| 100 | 22:49 |
| 90 | 24:15 |
| 85 | 25:04 |
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I need to try that blowing, but with my short stem it might not work as well as with your longer stems. Also it matters which technique is faster or rather costs less RPM.
I use the blowing technique mainly when I check my tops with the brush and paint, for to fine tune the balance.
When I spin the tops for longest spins I prefer to continue twirling until the top is vertical enough, (multitwirl spins), or maybe I spin the top again, (single twirl), but this is not too important for me because my tops can spin in tilted position without problems. There is just a little advantage if I can start a top in vertical position because in my tops the spin decay is slightly more rapid when the top precesses, so for longest spins it is a bit better if I can avoid precession.
In your case, if you want to try, you could blow on the flywheel, not on the stem.
precession I try to get rid of as good as possible in the beginning, nutation should also have gone long before the slow period - that should leave only unbalance with your comments related to that part.
Anyway, if you see intermittent wobble, like in the end of your video, you can be certain that there are two basic wobbles at the same time, unbalance alone cannot produce that kind of movement.
My question for you is, which ball size do you think is most promising?I found there are mines available with 0.3 mm , 0.7 mm, 1.0 and 1.2 mm diameter tungsten carbide ball tips. To check all sizes in depth seems a bit much.
Maybe the 0.3 mm. In my experience littler diameters, with lubricant, have the lowest friction, and the advantage of the lowest friction seems bigger than the disadvantage of the decreased stability, and the spin times seem a bit longer. But I have not much experience with ball tips. If I had to choose two diameters to test, I would go with 0.3 and 1.2.
And another question to you Iacopo: How do you know in a top that unbalance is not only good, but almost perfect? What tells you that it is not worth trying to balance a top better still? There must be something more then "oh I am tired of all this tedious balancing, I just say that this is the best possible balancing."
When the top spins without any wobble at medium or low-medium speed, I am satisfied and I stop to further improve the balance.
Correcting the tiny unbalance visible at low speed is tedious, it can take much time and patience, and also it is not very useful, because I noticed that that almost perfect balance is temporary, maybe because of the wear out of the tip, and/or micro dents in the contact point of the tip which could happen when the top is spun.
A shift of 1/1000 mm of the effective contact point of the tip produces visible effects on the balance of the top at low speed, in my tops.
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... If I had to choose two diameters to test, I would go with 0.3 and 1.2.
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Thank you, that is what I also am in favor of this morning. :D
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When I want to cancel the precession, I blow against the stem of my tops in the instant when they are tilted towards my left, this makes them rise in sleeping position. In the past I used to kick the stem of the top with a pencil but now I feel that blowing is more gentle and accurate, so this has become my habit.
Nice trick -- probably with negligible braking of the spin. Dangling a loop of low-friction string against the stem can also put a top to sleep if your timing is right. But it may take more than one pass to get all the way to vertical.
Guessing a soft feather might work, too.
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But it may take more than one pass to get all the way to vertical.
Blowing too takes more passes, usually.
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But it may take more than one pass to get all the way to vertical.
Blowing too takes more passes, usually.
Yes, that what I also think after trying with not so much success a few times. I am not so sure what the best method is: at the stage when I would do it, the top is at its highest speed and the precession at the lowest speed. That means using more passes then one also takes quite some time in which the top slows down as well. So putting the fingertip on the top as I do in the video might be almost as effective in the end. I think that was the suggestion how to do it in the "Quark Top" manual.Of course the best way is, to start the top upright to start with. Practice and a longer stem should help to achieve that?
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On my 25:04 spin I recorded the data for the spin down curve by hand still:
|
| RPM | t |
| ~720 | 00:00 |
| 650 | 00:42 |
| 600 | 01:21 |
| 550 | 02:03 |
| 500 | 02:54 |
| 400 | 05:00 |
| 300 | 08:06 |
| 200 | 13:07 |
| 190 | 13:48 |
| 180 | 14:30 |
| 170 | 15:16 |
| 160 | 16:05 |
| 150 | 16:59 |
| 140 | 17:57 |
| 130 | 19:02 |
| 120 | 20:11 |
| 110 | 21:26 |
| 100 | 22:49 |
| 90 | 24:15 |
| 85 | 25:04 |
I had a bit of time, I played with these numbers.
I made a graph of the spin decay out of them:
(https://i.imgur.com/BHRAY1n.jpg)
Then I obtained from the graph the data for to calculate the efficiency:
In the first minute the top went from 720 to about 625 RPM,
the efficiency in the first minute of spinning, (percentage RPM retained after one minute spinning), is 625 : 720 = 0.868 = 86.8 %
I calculated the efficiency data for some other speeds and put them in the graph below.
The dotted line is the JBB top.
The dark green line is my Nr. 25, with ruby tip, spinning on a large flat mirror.
The blue line is the Nr. 14, with carbide tip, spinning on its pedestal.
(https://i.imgur.com/T8QHl5G.jpg)
I was especially interested in comparing the Nr. 25 to JBB, their spin times are similar, and they both have external tip and they are spun by a single twirl.
JBB is a very stable top and topples down at only 85 RPM while Nr. 25 topples down at about 235 RPM. JBB wins by far here.
JBB has also a very good efficiency at low speed: this is typical of tops which are relatively light, with large radius of gyration.
Ortwin, what are the weight and the diameter of JBB ?
The lower efficiency of JBB at high speed should be due to aerodynamics, I think to the spokes, which probably have a high air drag.
The higher air drag, together with the short stem, should limit the starting speed.
I think that JBB should spin for very long in the vacuum, where there is not air drag.
The top Nr. 14, (light blue line), can spin for more than 40 minutes, this is not due to its efficiency, (lower than that of the Nr. 25), but to a high starting speed, (multitwirl spin + long stem), and to a low toppling down speed, (recessed tip).
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These are the tops Nr. 25 and 14.
Diameter Weight
Nr. 25 55 mm 187 grams
Nr. 14 52 mm 165 grams
(https://i.imgur.com/ahPAiyu.jpg) (https://i.imgur.com/7KKg50v.png)
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...
I calculated the efficiency data for some other speeds and put them in the graph below.
...
Ortwin, what are the weight and the diameter of JBB ?
...
Thank you for taking the time to analyze my data!
The diameter of JBB is about 91 mm and it weighs 132 g.
......
The lower efficiency of JBB at high speed should be due to aerodynamics, I think to the spokes, which probably have a high air drag.
The higher air drag, together with the short stem, should limit the starting speed.
I think that JBB should spin for very long in the vacuum, where there is not air drag.
The top Nr. 14, (light blue line), can spin for more than 40 minutes, this is not due to its efficiency, (lower than that of the Nr. 25), but to a high starting speed, (multitwirl spin + long stem), and to a low toppling down speed, (recessed tip).
Well, it does not work well without the spokes. ;D But I am working on reducing the spoke cross section by a factor of two. I think I wrote, somewhere above, that already moving the balancing weights from the outside to the inside made a difference of, I would guess, two minutes. I will also try again without those weights on the spokes. I tried only briefly to have JBB in the vacuum chamber. It became quickly unstable. I need to try again with a little more time and effort.
Regarding the tungsten carbide tips, I ordered mines that have 0.5 mm ball. I was wrong before when I said that I saw 0.3 mm ones.
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Well, it does not work well without the spokes. ;D
As we saw here (http://www.ta0.com/forum/index.php/topic,6408.msg69527.html#msg69527) with my von Braun spoked flywheel, thinning the spokes helped a little.
But as we saw here (http://www.ta0.com/forum/index.php/topic,6408.msg70008.html#msg70008), hiding them from the air with smooth solid fairings above and below helped dramatically, and even a single fairing above helped a lot.
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Thank you Jeremy for reminding me of those tests with the fairings I still needed to perform.
So now I cut a sheet of thin foil and placed it on top of the spokes. It came from a protective cover of a protective cover for tablet PC.
I measured the time it takes now to spin down from 500 RPM to 250 RPM: 5:13 .Then I took that fairing off again and did the measurement again: 7:18
That time is in the range what I had for my 25:04 spin.
So the fairing does not help in my case. Sure the fairing could have been done a bit better: more careful cutting, sticking it tighter to the brass flywheel and so on. But it was not that bad that I think that would make such a big difference as to change the sign of the effect.
I noted three more times between 500 and 250 for these measurements but all of them point consistently into this direction: JBB does better without the fairing.
I guess it is on the other side of the crossover region I mentioned here (http://www.ta0.com/forum/index.php/topic,6408.msg70092.html#msg70092).
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Yes, a very interesting result. Which underscores my sense that we're still far from understanding top aerodynamics. Simple toys, eh?
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So the fairing does not help in my case.
I would like if you could try with two fairings, to shield the spokes completely, because with one fairing alone the spokes are still free to move the air like a fan.
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The diameter of JBB is about 91 mm and it weighs 132 g.
JBB is more similar to my Nr. 33, which too is a large and light top:
(https://i.imgur.com/mInkz4U.jpg)
Large and light tops generally are more sensible to the air drag and have poor efficiency at high speed.
I am not sure if it is better to have the spokes or a closed surface like the Nr. 33.
JBB is more efficient than the Nr. 33 but this could be due to the Nr. 33 being quite lighter, (77 grams vs. 132 grams).
The diameter of the Nr. 33 is 76 mm.
(https://i.imgur.com/aNsopUA.png)
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So the fairing does not help in my case.
I would like if you could try with two fairings, to shield the spokes completely, because with one fairing alone the spokes are still free to move the air like a fan.
Sure, I applied the upper fairing again and made one for below the spokes.
(https://i.ibb.co/7C5LRZ7/SONY-DSC.jpg) (https://ibb.co/7C5LRZ7)
With the fairing below, it could no longer spin well on that mirror on the pedestal where it got past the 25 minutes.
So I had to perform these experiments on a completely flat mirror. It is one on which it is losing speed a bit faster, so to be able to compare, I did a run without fairings directly after the spin with upper and lower fairing.
| RPM | t |
| 500 | 00:00 |
| 450 | 00:37 |
| 400 | 01:15 |
| 300 | 02:33 |
| 250 | 04:54 |
| above is the spin with upper and lower fairings
|
| |
500
| 00:00
|
450
| 00:43
|
400
| 01:32
|
300
| 04:27
|
250
| 06:26
|
| above is the spin with no fairings
|
| |
| |
| |
| Fairings are not good for JBB
|
| |
| |
| |
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How many runs each, with and without fairings?
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Fairings are not good for JBB
Thank you for trying.
It is interesting to see that you have clearly more air drag with the fairings than with the naked spokes, I didn't expect it.
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How many runs each, with and without fairings?
Only one of each for this test.
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You're happy with so few data points?
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You're happy with so few data points?
As they say around here:
"Happiness runs in a circular motion!!!"
But yes, I think I am fine with that for now.
The wrong reason for this is that I expected it due to my former fairing experiments.
Another reason is, that to me it makes sense: Large area of fairing surface makes lots of friction. The surface goes with the square of the radius.
On the other hand spokes create drag. But the spokes length (surface) goes only linear with the radius of the flywheel. So the spokes will eventually win.Surely a over simplification, but not counterintuitive.
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Alright, here come some more data points: JBB spinning for 24:17
Full spin video plus spin decay curve as recorded with that new tachometer I received yesterday.
(https://i.ibb.co/PDxHxLT/overview.jpg) (https://ibb.co/PDxHxLT)
(https://i.ibb.co/3cqXHQZ/SDC-JBB-24-17.jpg) (https://ibb.co/3cqXHQZ)
This is a graph of the raw date minus quite a few values that where high above the curve. I set those to zero by hand.Not all values are lying on the curve. Mostly this is due to precession and to the traveling of the top, the laser did not always hit it properly. Especially in the later phase of the spin this becomes a problem. So this is another reason why precession in the beginning is not good.I am not happy with the data handling program I am using. That is why I did not put much effort in preparing a better graph. I have Libre Calc. Similar to Excel which I also do not like much for this kind of task. I need to get something similar to "Origin" again.I put the date in an attachment for the hardcore fans.
https://youtu.be/YD-jRBq6TUY (https://youtu.be/YD-jRBq6TUY)
Another Q&D production - Although as spin times become longer and longer you almost can't call it quick any longer.
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https://m.youtube.com/watch?v=8eJXMzvDovI
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Yes, I copied that line into my post directly from the signature of "the Earl of Whirl" without asking, so you have every right to throw this video at me. For me that woman is a bit scary, sorry, I liked the video that flew around here a few weeks ago with the original performer (Donavan?) a lot better.
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You're happy with so few data points?
Another reason is, that to me it makes sense....
Science is a way of trying not to fool yourself.
— Richard Feynman
Sometimes fairings reduce overall braking torque, sometimes they don't. How to predict for a given flywheel on spokes? Who knows? Not me.
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Alright, here come some more data points: JBB spinning for 24:17.... This is a graph of the raw date minus quite a few values that where high above the curve. I set those to zero by hand.... I am not happy with the data handling program I am using. That is why I did not put much effort in preparing a better graph. I have Libre Calc. Similar to Excel which I also do not like much for this kind of task. I need to get something similar to "Origin" again.
Excel works well for me, but I've been using it for decades. Most of all, I want (1) easy mathematical analysis, (2) easy plotting of the raw SDCs, and (3) easy addition of exponential trendlines. Why the last? Because I find the exponential best fit useful as a measurable reference curve providing an easy way to compare our empirical SDCs. The exponential lifetime (reciprocal of the trendline's decay constant) is a very handy figure of merit for decay rate prior to the SDC tail.
Excel does plotting and exponential trendlines well enough, and with pain I'm willing to live with. Just got Google Sheets to do all 3 things, too, but much more painful and much less flexible.
Not all values are lying on the curve. Mostly this is due to precession and to the traveling of the top, the laser did not always hit it properly. Especially in the later phase of the spin this becomes a problem. So this is another reason why precession in the beginning is not good.
I also had to hand-cull some obvious outliers due to precession and travel. And I can relate to the trouble you had twirling JBB straight into quiet sleep. I get around that with a starter. If I'm just capturing an SDC, why not?
In my experience, the larger the AMI, the smaller scrape angle, the shorter the stem, the larger the tip radius of curvature, or the more concave the support surface, the more tries it takes. It's also important to hold your mouth just right during the twirl. ;D
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.... I get around that with a starter. If I'm just capturing an SDC, why not?
...
Why not? Because you waste a chance for practicing your hand start abilities!
Alright, I might use the ribbon method with two strings if you want a better SDC.
...
Excel does plotting and exponential trendlines well enough, and with pain I'm willing to live with. Just got Google Sheets to do all 3 things, too, but much more painful and much less flexible.
...
For this kind of thing Excel is giving me personally too much pain. I used to be used to "Origin" because I used it a lot. I am trying to look into similar freeware at the moment.
...
In my experience, the larger the AMI, the smaller scrape angle, the shorter the stem, the larger the tip radius of curvature, or the more concave the support surface, the more tries it takes. It's also important to hold your mouth just right during the twirl. ;D
Yes, but I try to see that as a good thing. You can look at it as positive play value, it keeps you busy like adjusting all those screws and things to get it balanced. If you would have bought a ready made top for cheap, and you would be able to spin it for half an hour with a single twirl almost effortless and without adjusting or lubing anything, you would be bored by it after a few days, not?
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JBB 26:22
The improvement here came mainly from the fact that I took the balancing weights off the spokes and luckily I could balance it well enough by tensioning the spokes.
That there is less air drag now is best seen at the higher speed end.
The contact point is also a bit closer to the center of mass. It extends now only about 1 mm below the ring, before that was about 2 mm. I think that was a little advantage bringing the topple speed down to 82 RPM from 85 RPM.
The starting speed might have been a bit higher ~730 instead of ~720 RPM but that does not make a big difference.
(https://i.ibb.co/DCpNHYk/26-22.jpg) (https://ibb.co/DCpNHYk)
Sometimes it is easier to record the data for the spin down curve by hand still:
|
| RPM | t |
| ~730 | 00:00 |
| 650 | |
| 600 | 01:42 |
| 550 | |
| 500 | 03:20 |
| 400 | 05:35 |
| 300 | 08:51 |
| 200 | 14:06 |
| 190 | 14:48 |
| 180 | 15:34 |
| 170 | 16:21 |
| 160 | 17:12 |
| 150 | 18:07 |
| 140 | 19:05 |
| 130 | 20:08 |
| 120 | 21:15 |
| 110 | 22:27 |
| 100 | 23:46 |
| 90 | 25:09 |
| 82 | 26:22 |
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Why not? Because you waste a chance for practicing your hand start abilities! Alright, I might use the ribbon method with two strings if you want a better SDC.
You could get in 20+ practice starts in the time it takes to do one JBB time trial. And with the benefit of instant feedback from the top's behavior and a single speed measurement.
I recommend an inline starter that effectively extends the stem during spin-up. That allows the clean release and tilt control needed to avoid unwanted precession and travel.
If you would have bought a ready made top for cheap, and you would be able to spin it for half an hour with a single twirl almost effortless and without adjusting or lubing anything, you would be bored by it after a few days, not?
Couldn't agree more. The chase is usually most of the fun. The main exception in my case: A pesky wobble that drives me nuts.
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JBB hardware update
Today the mailman brought me some new modules for Junior Brass Band directly from the lathe.
(https://i.ibb.co/Mphh5Xc/SONY-DSC.jpg) (https://ibb.co/Mphh5Xc)
A : three axes of different lengths with tips from ball point pens. The balls have a diameter of 0.5 mm and are made of tungsten carbide
B : knurled knobs for better twirls
C : counter nuts, spacer
An assembled the new version of JBB looks like this:
(https://i.ibb.co/Mk2wG8F/SONY-DSC.jpg) (https://ibb.co/Mk2wG8F)still spinning(https://i.ibb.co/HgTMc1k/SONY-DSC.jpg) (https://ibb.co/HgTMc1k)
For looks it is an improvement, performance-wise I can't say anything yet, but it feels good! Of course I hope for improvement in spin time.
Maybe by one minute caused by the smaller tip diameter and another minute caused by higher starting speed due to a better knob?
Only wild guesses fueled by hope.
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A handsome and capable piece of gyroscopic equipment you have there, Mr. Ortwin.
What is the diameter of the knurled knob?
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...
What is the diameter of the knurled knob?
The knurled knob has a diameter of 10.5 mm - dictated by availability. I wanted a larger diameter, 12 to 13 mm.
That number is based on the diameter of the stem of my "Quark Top". With that I can reach starting speeds of above 1500 RPM.
Therefore I think the smaller torque I can apply with the thinner stem/knob is limiting my starting speed with JBB to the observed values of below 800 RPM, mostly.
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JBB 28:07
The new hardware I mentioned in a post above is doing well, but that was not the cause for this improvement in spin time.
With the "JBB hardware update" my best time improved only by three seconds to 26:25. It was clear that further better balancing would be needed to get to the improvement of about 2 minutes I was expecting from that hardware update.
But then on Monday, the two sapphire watch glasses arrived that I ordered for cheap from China a few weeks ago.
(https://i.ibb.co/GF04R6Y/Sapphire.jpg) (https://ibb.co/GF04R6Y)
They are flat and too thick to be made concave with the vacuum trick. That means the base has to be leveled carefully for the top not to wander off the sapphire. The tungsten carbide ball tip with the 0.5 mm small diameter helps in that respect because the top is not moving around too much. Nevertheless, I had to adjust the leveling of the base during that 28:07 run once, at around two minutes to keep JBB from going for a hike. (I guess that disqualifies that spin from being a "legit" one, in my book at least.)
But the combination of a tungsten carbide ball tip and sapphire really seems to work well! More tests are needed regarding the lubing and so on....
First I will try to get JBB really good balanced, that is why I put those nuts back on the spokes. If I manage to get back to that nearly perfect balance, I am confident that JBB can spin past the half hour barrier on sapphire.
(https://i.ibb.co/DQvbKk0/JBB-28-07.jpg) (https://ibb.co/DQvbKk0)
The starting speed for the 28:07 run was ~800 RPM, toppling at ~88 RPM . I did not record a full spin decay curve for this, I just noted some values on paper. On a glass mirror surface I have a SDC of 26:25 should any one be interested. Since there is still some clear progress on the spin times without close inspection of the spin decay curves, that is not my major focus for now.
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They are flat and too thick to be made concave with the vacuum trick. That means the base has to be leveled carefully for the top not to wander off the sapphire. The tungsten carbide ball tip with the 0.5 mm small diameter helps in that respect because the top is not moving around too much. Nevertheless, I had to adjust the leveling of the base during that 28:07 run once, at around two minutes to keep JBB from going for a hike. (I guess that disqualifies that spin from being a "legit" one, in my book at least.)
Good progress!
In my book slowly adjusting the base so it doesn't spin out is legit.
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In my book slowly adjusting the base so it doesn't spin out is legit.
I agree. You're just suppressing travel dynamically. Any effect on spin decay rate would be upward. No regeneration involved.
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In my book slowly adjusting the base so it doesn't spin out is legit.
I agree. You're just suppressing travel dynamically. Any effect on spin decay rate would be upward. No regeneration involved.
Not everything that is not regeneration is fine. For example: I could start the top and at the same time the stop watch. But then I realize that the top is precessing too much for a good end result. I touch the top somehow to kill most of the precession. This certainly only slows the top down. Do I let the stop watch running? Do I start it at zero again after the last touch to the top? Should I just stop the run and try a better one?
Yes, it is fine for now. I will be happy to reach the 30 minutes goal with some leveling in between. But after that the next goals will not be a longer spin time, it will be to go past the half hour in a clean way: no leveling or otherwise messing around with the base (lubing, pumping vacuum ) during the spin. No touching the top after the initial twirl. Recording a video of the whole spin. Recording a spin decay curve of the whole spin. No pedestal, make sure that the contact point is always the lowest point of the top. Except for the spin decay curve that video of the Kemner "top" that spins for almost 50 minutes provides all that.
In the meantime JBB has taken a spin for 28:36 , with quite some leveling of the base and some vacuum pumping to keep the sapphire fixed in place. during that time.
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JBB 28:59
Today a double domed sapphire watch glass of 30 mm in diameter arrived.It works great as base for JBB! The friction seems to be as small as with the flat sapphire. But with this I don't have to work on the leveling screws during the spin any longer. And in addition to that, it is more forgiving with twirls that give the top some lateral momentum at the start: instead of sliding straight off the base, the top just comes back to the center. That leads to a higher average starting velocity. For the 28:59 run the start was at about 820 RPM, topple speed around 79 RPM.
The minute that is missing to the half hour, I hope to get from still better balancing (~1/2 minute) and from a higher starting speed (~1/2 minute). I might need a different stem of larger diameter though, to reach a higher starting speed.
Since the sapphire does not look that much different in a photo from the flat one in reply #212, and on JBB basically only the positions of the balancing nuts changed a bit, I am not posting any pictures here.
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Congrats on the continued progress!
Your current 10.5 mm knurled stem is already quite thick. By all means, keep some kind of knurling. But given JBB's substantial but not extreme AMI, you might also experiment with thinner stems -- especially if you're allowing multiple twirls.
Or better yet, try some tapered or stepped stems. All of my high-AMI tops have stems stepping down from about 7 to 5 mm, with my fingers starting on the thicker part and moving up to finish on the thinner. Without the thinner step, their release speeds are considerably lower.
Iacopo's stems taper down to 3 mm.
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....you might also experiment with thinner stems ...
Thinner ? Should my reasoning from reply #211 be so terribly wrong?...
The knurled knob has a diameter of 10.5 mm - dictated by availability. I wanted a larger diameter, 12 to 13 mm.
That number is based on the diameter of the stem of my "Quark Top". With that I can reach starting speeds of above 1500 RPM.
Therefore I think the smaller torque I can apply with the thinner stem/knob is limiting my starting speed with JBB to the observed values of below 800 RPM, mostly.
To my understanding the diameter of the stem sets an upper limit to the max. attainable speed. The thinner the stem, the higher the possible speed. Since I reach above 1500 RPM on a top with smaller AMI than JBB, and a 12 mm stem, that diameter can't be too large to reach the goal of 1000 RPM with a top of larger AMI (JBB). Therefore the acceleration I can provide for the top over the short time of a twirl must be too small if I can only get to about 820 RPM. For larger acceleration a need a stem of larger diameter. Tomorrow I want to look for something with a 15 mm diameter - unless someone is telling me where I am wrong.
... By all means, keep some kind of knurling. ...
If possible yes, but the trick with the rough sandpaper glued to the stem is also working very well.
...-- especially if you're allowing multiple twirls....
Multiple finger twirls don't work for me as I said, also that is Iacopo's territory ;) .But I am considering -as a different endurance category- multiple twirls with two palms. It is easy to attach the according stem to JBB. But what is the "according" stem for that type of start? About 10 cm long I would guess. But what thickness? Which material? Maybe some carbon fibre, maybe wood?
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....you might also experiment with thinner stems ...
Thinner ?
I agree with Jeremy and I think it is worth to experiment with different diameters, also thinner ones.
In fact, even if a larger knurl diameter provides a larger acceleration, the acceleration phase lasts less time with it, so it is not certain that the starting speed will be higher with a larger knurl.
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I've found the topmaking biz quite humbling. It's always good to plan your next design iteration carefully. But top dynamics are highly non-linear. So are twirling dynamics. Even the most educated guesses may not pan out in practice.
So it's also a good idea to test outside your expectations.
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With JBB I used basically three different stem diameters: 7.5 mm, 10.5 mm and ~12.5 mm.
The 7.5 mm stem brought JBB across the 25 minutes by providing a starting speed of 720 RPM. In reply #207 (https://toolineo.de/kipp-raendelknopf-innengewindegroesse-m5-form-a-material-duroplast-messing-farbe-schwarz-p!100000001745347.html?h=0000130&chn=gads&utm_medium=cpc&utm_source=google&cpkey=uhmGdn0rnLyQKTZUyJi0HVqvdSZ1FWDao_KUZC1JzJTULqYZKyNyevxtLSmkOgDktGAnKFuiXSC-8mYccLenOw~~&gclid=Cj0KCQjw_8mHBhClARIsABfFgpiV9pwyM5lJK__3EvbJlQCkLUW8UoJOaJdXb3EKC7UCWc6_4izx61MaAkIBEALw_wcB)I then reported with the same stem 730 RPM.
With the 10.5 mm knurled stem I saw starting speeds up to 820 RPM as in reply #216 (http://www.ta0.com/forum/index.php/topic,6419.msg71524.html#msg71524).
With the stem of ~12.5 mm and the sand paper glued to it I reached as well about up to 820 RPM. But this stem seems too tall for being in good balance with JBB. It always loses at the low RPM end a lot of time.
So for me things are pointing at the moment to a short stem with a diameter of about 15 mm.
I go and look for something like this now:
(https://i.ibb.co/9vZHqnV/Kipp-R-ndel.jpg) (https://ibb.co/9vZHqnV)
It might not be the right path, but I need to try.
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In my personal experience, I have better starting speeds with less large stems, even with single twirl spins.
Maybe it is not the same for everybody. Maybe there are persons with hands that are more agile and less strong that the mine, and who can find easier to spin a top with a larger stem. Probably the optimal stem diameter for tops with a larger AMI than the one I tested here, could be a bit larger.
This is a test I made;
I turned an extension for the stem, and I turned its diameter progressively more and more narrow, from 12.5 mm to 3 mm.
I spun the top hard with the extension, many times, these are the highest starting speeds I had with the different diameters of the extension:
(https://i.imgur.com/UdISJdZ.jpg)
The grip of the extension for the fingers was perfect for the larger diameters but a bit slippery for the littler ones.
So, adding a knurl would further favour the littler diameters.
3 mm is very thin and I have two problems with it: little surface in contact with the fingers, (so it slips more easily), and also the fingers coming in contact to each other, so part of the energy is lost for friction between the two fingers. 4 mm works best for me, even for single twirl spins, so I make my tops with about this diameter of the knurl.
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Not necessarily a contradiction to my findings. I would guess JBB has an AMI about as three times as your test top? So things are a bit different.
I will keep you updated on my results. By the end of the week I should receive the knurls with 16 mm diameter.
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@Iacopo: Actually your findings go well together with my plans and my simple model for the optimum stem diameter: The optimal stem diameter scales directly with the AMI of the top. Since JBB has about three times the AMI of your test top, the optimal stem diameter should be three times your optimal stem diameter. Your optimal stem diameter is 5 mm, so it will 15 mm for JBB, as I plan at the moment.
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Your optimal stem diameter is 5 mm.
My optimal stem is 4 mm, not 5.
Without knurl, the 4 mm tends to slip between my fingers so 5 mm seems better.
With the knurl, 4 mm is best for my tops.
I am not sure that 3 mm could be even better than 4 mm, because I have particular problems with it. Maybe I should make thimbles of some hard rubber to overcome those problems, and test, so I could know it.
Anyway, it makes sense to me that with a larger AMI, the optimal diameter of the stem increases.
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...
My optimal stem is 4 mm, not 5.
...
Ah, I took 5 mm because in reply #222 you gave the highest speed to the stem with 5 mm.
3 mm to 4 mm is the range where I want to start experiments with the multiple twirl technique with two palms.
But right now I want to do a run in vacuum.
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Alright, JBB took a spin in the vacuum. It lasted well over one hour. Maybe one hour and 11 minutes. I did not watch it all the time, but that is what I get from the video footage I took and the spin decay curve ( available upon request). Starting speed something above 600 RPM. Toppling seems to be above 100 RPM, no proper balancing, contact point to CM distance quite big in comparison to the best spins of JBB in air.
The video is showing only about the first two minutes and the last two minutes. Next time I need to place a clock visibly in the video.
https://youtu.be/xT7hbJAms90 (https://youtu.be/xT7hbJAms90)
Another Q&D production ... I hope you don't mind...
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That darn air -- can't live with it, can't live without it!
Well done!
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3 mm to 4 mm is the range where I want to start experiments with the multiple twirl technique with two palms.
...
It turned out to start at more like 6 mm. I cut the head of a M5 screw and put some black heat shrink tube over most of it.
JBB could also stand for "Japanese Brass Band"
To me it is the most elegant looking version of JBB so far. As others said before: brass and black go together well.
(https://i.ibb.co/QHTFssQ/SONY-DSC.jpg) (https://ibb.co/QHTFssQ)
Did I get it right, that palm shear starting technique is particularly common in Japan?
https://youtu.be/e004ExGA0pQ (https://youtu.be/e004ExGA0pQ)
I got JBB up to more then 1700 RPM this way, in the video it is 1250 RPM. So at that end I win at least three minutes but I lose a lot more at the low RPM end so far:
-can't do it on the sapphire yet
- contact point to CM distance is a lot higher
- not properly balanced yet
...
So it is still below 20 minutes in both timed spins it performed so far.
It is a totally different category anyways than the single twirl with one hand. I think if I come back to this in more seriousness, the goal should be 45 minutes.
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Very nice!
Do you have any idea what is the vacuum that you can get with the hand pump? I wonder if the decay is now completely determined by the tip friction or if there is still some residual air drag.
Did I get it right, that palm shear starting technique is particularly common in Japan?
It's common with Kyukogoma tops.
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Do you have any idea what is the vacuum that you can get with the hand pump? I wonder if the decay is now completely determined by the tip friction or if there is still some residual air drag.
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I did not measure the pressure directly but my guess is something like 3 -7 mbar. It is from an "Ice-Quick" set
Ice Quick (https://www.dailymotion.com/video/x2srea6).
Since it works in freezing the water, the pump must be able to make a vacuum better than 6 mbar which is the saturation vapor pressure of water at the freezing point.There is certainly still plenty of air drag! 6 mbar is very good for a hand pump, but it actually more at the upper end of "medium vacuum".There is a measurement method for vacuum that makes use of exactly that air drag on a levitating ball. Martin (Levitron) Simon pointed that out to me when I was fooling around with that levitating magnetic sphere:
"
Nice try. With that pump I think you are still in the heavy
air friction dominated damping region. Maglev rotatingspheres are used as pressure gauges. Measure the dampingrate and you know your pressure, from 1 - 10^-6 mbar(Torr).
https://www.mksinst.com/product/product.aspx?ProductID=283 (https://www.mksinst.com/product/product.aspx?ProductID=283) "
You see, that method is applied at some orders of magnitude lower pressure than we deal with here.
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The aerodynamic braking torque in the von Karman case is proportional to air density and the square root of the air's kinematic viscosity.
The good news: The density is proportional to pressure at constant temperature.
The bad news: To get a significant reduction in the kinematic viscosity, you'd need to approach the kind of vacuums used in particle accelerators.
ortwin, how far are you from CERN?
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...
ortwin, how far are you from CERN?
If I travel the distance I am away from CERN not to Switzerland but straight upwards, I should also reach some decent vacuum.But the vacuum is only another silly diversion, I mean we all know that things can spin quite long when there is nothing braking them. Take our mother planet: 4.7 billion years or something?
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JBB 29:19
Not much changed from reply #216 or #212, tiny bit faster start (comes from all that practicing I guess) ~825 RPM. Topple at ~79 RPM since I took more time and care balancing the top while making sure those balancing nuts where as much as possible inward on the spokes. That reduction in air drag resulting from the position change of those tiny nuts really seems to make a difference of a few seconds (that is why I plan a next version with even thinner spokes and better balancing and centering options).
So if those larger diameter knurls, that I am expecting by the end of the week, really help me to get starting speeds of up to 900 RPM as I hope for, I should be able to report some time above the half hour next week.
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Your coming upgrades sound promising.
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JBB 29:19
Congratulations !
Now you are very near to my best spin of a brass top/external tip/single twirl, (with carbide contact points):
29m 38s
Better than this with a single twirl/external tip I have only the spin obtained with my tungsten top, (36m 11s).
You are doing very well !
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...
Congratulations !
Now you are very near to my best spin of a brass top/external tip/single twirl, (with carbide contact points):
...
Thank you Iacopo!
Please send me your postal address via private message. I want to mail one of those flat sapphire watch glasses to you. I am curios how your tops will perform on that surface.
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I got JBB up to more then 1700 RPM this way [palm twirl], in the video it is 1250 RPM. So at that end I win at least three minutes but I lose a lot more at the low RPM end so far:
-can't do it on the sapphire yet
- contact point to CM distance is a lot higher
- not properly balanced yet
...
So it is still below 20 minutes in both timed spins it performed so far.
Tough trade-off. Unfortunately, that long metal stem increased both central TMI/AMI ratio and CM height to the detriment of critical speed, as you observed. Also put more weight on the tip.
Following the teachings of Iacopo-san, you might try a low-density wooden stem instead. For single finger twirls, the wooden stem could be as short as 24-32 mm, preferably tapering upward.
The tapering end of a cheap disposable chopstick comes to mind. Not so elegant, but the unfinished texture should be good for grip.
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... For single finger twirls, ...
I would like to see that performance! Can you make Q&D video? Which finger are you using? >:D
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... For single finger twirls, ...
I would like to see that performance! Can you make Q&D video? Which finger are you using? >:D
Pinkie. No video -- top-secret technique.
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...
Following the teachings of Iacopo-san, you might try a low-density wooden stem instead.
...
I think I will come back to this palm shear start only in a next version of the top, with the thinner spokes, because the lower air drag will pay off especially with the higher RPMs I can reach. With this JBB version I hope to get the half hour done, and then it will be time for the next family member to take over.
At the moment I envision a carbon pipe for the palm shear start.
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JBB starts with 880 RPM
That was the good news.
To achieve this, I glued some rough sand paper to the knurled brass I used before as a stem. The diameter increased thereby from 10.5 mm to maybe 11.5 mm. But the main contribution to the higher starting speed, is the better grip I get to the sandpaper surface than to the knurled stem.I was happy when I noticed that and thought now it is time to try to get past the half hour. I took time to balance JBB once again as carefully as I could and got everything ready for a time trial. - But then I noticed that my double domed sapphire watch glass that worked so well as a surface is now terribly scratched in the central area!!! And that was also clearly visible in the spin decay values! Oh, no! What happened?
This was a hard way to learn a bit more about hardness! Sapphire is a hard material (9), and then there is diamond (10), but I clearly don't have many diamonds around. But in between 9 and 10 there are more numbers, like for example 9.6. The hardness of Silicon Carbide is 9.6 and that material is often used as abrasive in sandpaper.
That means my theory on this now is, that some SiC "sand" fell from my stem through the spokes onto the sapphire surface and the tungsten carbide ball tip rubbed it in! Now I have to shop (and wait) for another double domed sapphire. :(
And of course I need a better alternative to the knurls than sand paper.
Since I still have those flat sapphire plates I tried one of those, hoping to get a good run with that without the need of leveling the base during the spin.
And yes, I got a good and fast start of 870 RPM. JBB remained on the sapphire for a long time, close to the rim, but on the sapphire. When down to 100 RPM it had spun already for 26min 18sec , clearly on the way foe a new personal best. - But then at 27min 20sec it went over the rim! :-\
I am not sad, I learned something and it will only take a bit longer until JBB reaches the half hour mark.
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JBB 29m 52s
Of course I can not just wait until the replacement for the scratched double domed sapphire glass arrives. I fiddle around and try to get to the 30 minutes on the flat sapphire, even though it means quite a bit of leveling during a spin. I get practice starting the top, leading to higher useful start velocities. For this 29:52 spin the start was at 855 RPM. Toppling in the lower eighties or upper seventies, I couldn't get a proper reading in the last minute of spin time. I had a 29:29 the other day, but I don't want to bore you with a post for every tiny improvement.
I moved the contact point now a bit upward towards CM but it is still an external tip, JBB can spin in principle on a flat mirror that is well leveled.
So maybe the category for it would be something like:
brass top/external tip/pedestal/single twirl/sapphire - tungsten carbide contact point
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So close!
Do you really think the sapphire helps?
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So close!
Do you really think the sapphire helps?
Only close. I think JBB feels that it will loose attention once it is is past the half hour mark and another family member is taking over. That is why it is putting on this show.
My estimate is, that the sapphire is getting me about 3 minutes on the half hour. That is based on the multiple observation that on my best glass mirrors it takes close to 10 minutes to spin down from 200 to 100 RPM, with the sapphires I get to eleven minutes.
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Some data on the 29:52 spin.
(https://i.ibb.co/KbLXXWQ/Data-JBB-29-52.jpg) (https://ibb.co/KbLXXWQ)
The mildly interesting thing I want to point out is the highlighted line:
Half of the rotational energy JBB had at the start is gone (converted to heat) after less then three minutes. That means if JBB is started with only 600 RPM (which is really easy in comparison to a start with more then 800 RPM) it will still spin for 27 minutes. i.e. 90 % of its total spin time.
If you look at it the other way around, half of the effort is needed to get the last 10% (or 3 minutes) of spin time.
This is typical for this type of decay curve, nothing new or special with this top I think. Still it is worth remembering and maybe a part of the explanation why the last mile is so hard to get and the last (reached) goal feels almost ridiculously easy.
(https://i.ibb.co/3776mk2/Diagramm-JBB-29-52.jpg) (https://ibb.co/3776mk2)
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Short of regeneration, there are 5 basic ways to improve a top's spin time:
1. Minimize wobble.
2. Increase release speed.
3. Reduce critical speed.
4. Reduce air resistance.
5. Reduce tip resistance.
When you're really serious about endurance, you have to attack on all 5 fronts while playing the inevitable trade-offs just so.
Of the 5 strategies, #2 is often the easiest to implement (as it involves no modification of the top) but the least effective, as you just demonstrated. In high-drag tops (like most of mine), #3 is clearly the place to start.
In a top like JBB, hard to say where to concentrate your efforts.
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...
1. Minimize wobble.
2. Increase release speed.
3. Reduce critical speed.
4. Reduce air resistance.
5. Reduce tip resistance.
...
Nice condensed version of what needs to be done!
I try to answer with my further efforts for JBB.
1. Minimize wobble.
Still potential there, but I do not have a good strategy, mostly hoping to be lucky. (Being lucky is not a crime!)
2. Increase release speed.
This can involve some changes in hardware in my case. Different knurled stems of different diameter.
More practice when my bruced fingers allow it again should also help.
3. Reduce critical speed.
A shorter lighter stem is the main thing I can do here.
4. Reduce air resistance.
I will try to cover the outer holes where the spokes go through the brass ring. Thinner spokes are reserved for a past JBB version.
5. Reduce tip resistance.
The small tungsten carbide ball will be the tip that I don't plan to change. Except the domed sapphire I am waiting for, I ordered a ceramic bearing pan, we will see how that performs.
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A very rational approach. As they say, better to be lucky than good! And you're going for both.
Hope your fingers get well soon. Maybe some kind of fancy athletic glove would improve grip and protect your fingers at the same time?
Plus, you'd look like a serious athlete ready for fierce twirling competition. The white gloves the Japanese use with their komas certainly give that impression.
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...
Hope your fingers get well soon....
Ah, it is nothing serious. Just a bit sore so that I can't get to the top speeds I need for the half hour. Today I got 29:25 with a start of 830 RPM.
As soon as the callus has developed on the fingers that are sore now, they will be better suited for the task than before. And since we are away for two weeks now and no spinning tops are traveling along, the fingers have time to recover. Its just like practicing a lot when you are new to guitar, only the other hand.
... Maybe some kind of fancy athletic glove would improve grip and protect your fingers at the same time?...
No gloves are allowed by my personal rules. If gloves would be allowed it would be hard to argue why a simple string should not be allowed. - And we know that starting speed can be easily doubled (energy four fold!) by using a string.
... The white gloves the Japanese use with their komas certainly give that impression.
So the gloves protect them, should they fall into a koma? >:D
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... The white gloves the Japanese use with their komas certainly give that impression.
So the gloves protect them, should they fall into a koma? >:D
Where's that groan emoji when you need it?
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JBB meets LEGO !!!
(https://i.ibb.co/Bg7v9Df/SONY-DSC.jpg) (https://ibb.co/Bg7v9Df)
There are two LEGO tires slid over the knurled stem.
I get starting speeds similar to those with the sand paper glued to to the stem, but with this LEGO tires I don't have to worry about them scratching my precious sapphire surface and also they are friendly on my fingers.
My fingers feel well again, but I did not receive the proper replacement yet for that scratched double domed sapphire glass, so no better times to report than the 29m 52s from earlier.
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In LEGOspeak, that's an NPU (nice parts usage). Generally considered a high compliment.
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What an excellent idea!
Yes, I'm going to give this a try.
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Junior Brass Band
30min 27sec
(https://i.ibb.co/GHMbR3V/SONY-DSC.jpg) (https://ibb.co/GHMbR3V) (https://i.ibb.co/Gs9yjJj/SONY-DSC.jpg) (https://ibb.co/Gs9yjJj) (https://i.ibb.co/9HdBTbm/SONY-DSC.jpg) (https://ibb.co/9HdBTbm)
Very happy now that a spin top of mine passed the half hour mark!
The category would be something like:
- single twirl
- external tip
- pedestal use
- brass flywheel
Some more technical details:
total weight: 128 g
diameter: 92 mm
height: 21 mm
tip: 0.5 mm tungsten carbide ball in ball point pen tip
spokes: stainless steel M2 screws, two nuts per spoke for balancing
stem: knurled plastic nuts on hollow M5 brass axle covered with a piece of a little balloon (this time it really is a regular balloon ta0!).
spin surface: flat sapphire watch glass, diameter 32 mm
Start with ~760 RPM 00min 00sec
200 RPM after 14min 40sec
80 RPM after 29min 07sec
First scrape with ~74 RPM after 30min 27sec
Frequent adjustment of the levelling screws on the base was necessary during the spin, to keep the top from travelling off the sapphire and fall.
I did not take a full spin down curve for this run and filmed only a short piece of it:
https://youtu.be/FKLUkyrN_G0 (https://youtu.be/FKLUkyrN_G0)
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Congrats! Well done!
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Half-hour barrier broken! Congratulations!
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Congrats on a very long spin! 8)
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Congratulations from me too !
I see that the starting speed is 760 RPM, but in the past you reached even 855 RPM.
You just spun the top less hard, this time, or this top is more difficult to be spun fast ?
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Congratulations from me too !
I see that the starting speed is 760 RPM, but in the past you reached even 855 RPM.
You just spun the top less hard, this time, or this top is more difficult to be spun fast ?
Thank you everybody!
And Iacopo, you mentioned the point I meant to explain before, but somehow missed it:
The stem is a compromise. The best stem for high starting speeds that I tried unfortunately weighs a bit much since it is from brass and is too long. This leads to CM moving upwards, increased TMI and more unbalance (I can correct the static unbalance with the nuts on the spokes, but it is more a transformation to couple unbalance I am afraid).So all these points lead to a worse performance at low speeds.The optimal performance at low speeds I got with no added stem at all, just by starting it as a stemless top by gripping the flywheel with all five fingers of my hand. The best run that way, was a starting speed of 540 RPM that resulted in a spin time of 27min 23 sec.
The knurled M5 plastic nuts I found at the hardware store, they weigh a lot less then the brass stem and finally were the compromise that brought me across the 30 minute line when I added part of a balloon for better grip and higher starting speed.
With the next version I have to look into a solution similar to yours, using wood or maybe CFK pipe for the stem.
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The stem is a compromise.
I too never had very good starting speeds with too short stems. But the stem being long and heavy is bad too.
I thought also that maybe the diameter of that plastic nut with the balloon could be a bit too large, but I am not sure;
I agree with your statement about the relationship between AMI and diameter of the knurl, so that tops with a larger AMI should need proportionally larger knurls for to be spun at the fastest speed with a single twirl, approximately.
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...
It's surprising how little finger tops can go for half-an-hour. Some physical law must be broken :P
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@ta0: since my last success in the field, I have some increased interest in tops that also reach half an hour spin time. Do you have details on those tops you referred to in the line above?
Other than Iacopos tops and that Kemner top, what other finger tops reached half an hour spin time? I know I asked this question in similar way half a year ago...
Didn't Aerobie (Alan Adler?) reach half an hour with some of his tops?
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...
It's surprising how little finger tops can go for half-an-hour. Some physical law must be broken :P
...
@ta0: since my last success in the field, I have some increased interest in tops that also reach half an hour spin time. Do you have details on those tops you referred to in the line above?
Other than Iacopos tops and that Kemner top, what other finger tops reached half an hour spin time? I know I asked this question in similar way half a year ago...
Didn't Aerobie (Alan Adler?) reach half an hour with some of his tops?
Well, at the Texas TopCon 2019 I attended, the record was 26 minutes 27 seconds with a Plier brand tungsten top.
I just looked them up, and somebody posted this:
(https://i.ibb.co/TkmSyKT/image.png) (https://www.etsy.com/shop/PlierSpinningTops)
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Half of the rotational energy JBB had at the start is gone (converted to heat) after less then three minutes.
I get similar results for spins in air, 50% energy is lost after about 3 minutes in a 20 minute spin. For same top in vacuum, 50% energy is lost after about 8 minutes.
(https://i.ibb.co/ZxDmJyW/Energy-spin.jpg) (https://ibb.co/ZxDmJyW)
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Short of regeneration, there are 5 basic ways to improve a top's spin time:
3. Reduce critical speed.
Jeremy, what is "critical speed"?
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I am sure Jeremy will give you an answer to this question ! He has been asked this many times before.
Here (http://www.ta0.com/forum/index.php/topic,6408.msg69608.html#msg69608) is a discussion where he explained it to me.
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Short of regeneration, there are 5 basic ways to improve a top's spin time:
3. Reduce critical speed.
Jeremy, what is "critical speed"?
Critical speed is the total angular speed needed to sustain sleep or steady precession against gravity in the face of small perturbations. Once a top spins down below this stability threshold, it's in a metastable state and will begin its fall at the slightest provocation.
As the formulas at the link ortwin gave show, critical speed depends only on the top's mass distribution. Its total mass completely cancels out.
Obviously, for a given release speed, the lower the critical speed, the longer the top will stay up. Conversely, for a given critical speed, the faster the release speed, the longer the spin time.
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Didn't Aerobie (Alan Adler?) reach half an hour with some of his tops?
He reached 26:05, with one of his tops:
My longest twirl was achieved with a 2.25" (57.15mm) diameter, 145g spinning on a .5" (12.7mm) ball. An 860 RPM twirl ran for 26:05. But the lube may have been "just right" because a 923 RPM twirl ran 24:27 and a 909 RPM twirl ran 25:28. With balls one can have too much lube. As I've mentioned before, I lube with forehead skin oil, wiped hard on the mirror with my thumb. This top falls at about 133 RPM.
I think 145g may be optimum for a 2.25" top and my personal twirl ability. I haven't measured the rotational inertia of my tops, but they are all fairly similar geometry with brass or bronze rims and lightweight hubs.
For a long time I thought the tip drag of big balls was not a worry. I even went larger to achieve no topple. But lately, I'm seeing longer twirls with smaller balls (.25" and .312"). Iacopo's tips are so sharp that his tip drag must be very low. What's their topple RPM?
As I've mentioned before, the no-topple tops don't spin quite as long because of their big balls.
Today I've been looking at RPM decay rate. Surprisingly, it's a fairly constant 8% to 10% per minute over the entire twirl period for my better 2" and 2.25" tops. I expected a more rapid decay at high speed due to aero drag. But it appears that my twirl ability doesn't get me into the speed range of substantial aero drag.
Alan
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.. . I've made tops that spin over 30 minutes. After launching a few long spins like that, my incentive to do more is pretty low. But keeping it spinning by rocking the base might be more entertaining....Best,Alan
I found the post of Alan again where he mentions the tops that spin over 30 minutes.
So to the best of your knowledge it is you and me and that Kemner top? (Well mine isn't even documented with a video.)
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I found the post of Alan again where he mentions the tops that spin over 30 minutes.
So to the best of your knowledge it is you and me and that Kemner top? (Well mine isn't even documented with a video.)[/font]
I didn't remember this claim of Alan. Probably he never showed those tops and he never talked about them anymore.
The tungsten Kemner top usually spins for up to about 20 minutes, so I would consider with some caution the 50 minutes spin of this top on YouTube.
I know throw tops that can spin for more than half an hour but not other finger tops.
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a metastable state
Jeremy, I tried for years to achieve a metastable state. Finally gave that up. :)
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a metastable state
Jeremy, I tried for years to achieve a metastable state. Finally gave that up. :)
Funny, I've been trying to go the other way -- also without much success. Grass is always greener on the other side of stability, I guess.
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Junior Brass Band spins for 30 minutes and 47 seconds -video- (http://youtube.com/watch?v=ckFUpKy82Qg)
After the replacement for the scratched double domed sapphire arrived, I wanted to make a video of a spin that lasts more than half an hour. In this video (http://youtube.com/watch?v=ckFUpKy82Qg) the time in between 2 and 28 minutes of the run is condensed by choosing 16x speed, but the full length version is available here (http://youtube.com/watch?v=IRoOteksntc).
The spin decay curve is also recorded but I do not know what I want to use it for. Anyone interested in that data, please ask.
Start with about 790 RPM.
200 RPM after 15:00 minutes
First scrape after 30min 47sec, with an RPM in the lower seventies probably.
@tao: hiding the screenshots did not work for me so far..... ...seems to work now, it is the first time I checked what that "toggle view" button does.
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The spin decay curve is also recorded but I do not know what I want to use it for. Anyone interested in that data, please ask.
Wow, looks great, Ortwin!
Yes I would like to see the spin decay curve.
The "double domed sapphire" is the base that keeps the top centered? And what tip do you use?
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As I've said before, a very handsome top. And such a smooth spin now! Well done!
Let me know when my copy is ready. >:D
I'd like to play with the spin decay data. Will be interesting to see where the speed exponent lands.
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The spin decay curve is also recorded but I do not know what I want to use it for. Anyone interested in that data, please ask.
...
Yes I would like to see the spin decay curve.
The "double domed sapphire" is the base that keeps the top centered? And what tip do you use?
In reply #255 (http://www.ta0.com/forum/index.php/topic,6419.msg72084.html#msg72084) of this thread I summed up some technical details of this top, only the knurl changed a bit.
There I used a flat sapphire that made it neccesarry to frequently level the base during the spin.
In reply #216 I (http://www.ta0.com/forum/index.php/topic,6419.msg71524.html#msg71524)mention this type of double domed sapphire. Some more details are spread all over the thread, I don't expect you to collect them, just ask what you are interested in.
I will make the spin decay curve available, I am just trying to think what would be the easiest way (for me), maybe I will ask Jeremy to assist, he is using the same RPM-meter.
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...
Let me know when my copy is ready. >:D
...
As "Junior" part of the name implies, this is supposed to be just a transitional version, I have hopes for the next (and probably last?) version to look better and work better in some respects. But you know the work on the lathe I do not do myself, so I am not too confident that there will be copies available.
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I'd like to play with the spin decay data. Will be interesting to see where the speed exponent lands.
Since you really seem to like to play with data and you know the file format, I just dumped the raw data on you in the attachment to this post. I never even looked at it, I hope it works. I took one data point per second. There is more than one hour worth of data since I recorded the data (and the video ) of another run just before the one with 30:47. That one ended after 29 minutes. The difference was the lubing: prior to this session I cleaned the sapphire with alcohol, but then I forgot to apply the forehead lube before I started the top. Only after that 29 minutes run I lubed the sapphire.
If that data should make no sense at all to you, tell me and I will force myself to look into making something visible.
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ortwin: Yikes, 1,847 data points in a single spin decay curve!
Will play with the data next week.
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ortwin: Yikes, 1,847 data points in a single spin decay curve!...
But the computers these days don't mind! For the people operating them it is the same time they would need for lets say 100 data points. Since sometime a data point is missing or obviously wrong, I thought it would be better to have more points to start with.
During that 30:47 spin I also wrote some data down by hand. From that I made the curve below:
(https://i.ibb.co/Kwv4Z0n/manual-spin-down-values.jpg) (https://ibb.co/Kwv4Z0n)
(You have to click on the figure to make the data also visible.)
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Dis-assambling - re-assambling - ba-lancing - test-run
This was filmed a few days before that 30min 47sec spin. It shows in more detail what JBB is composed of, some steps of the balancing I perform on it to get it to spin for a while and some other stuff.
There is not much edited in this video, only some captions added and sometimes the audio is taken away so that you don't hear me and my family talking nonsense. I trust it that everybody can make use of that function that lets you skip the 98% of the video that are not of interest to them.
https://youtu.be/MRbt0bzm4tE (https://youtu.be/MRbt0bzm4tE)
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LaBrassBanda (https://www.labrassbanda.com/media.html?lang=en)
is a Bavarian music band. The first time I heard of it was only a few month ago, but I kind of like what they are doing. You can browse a bit through this long video:
https://youtu.be/gNYFyritpRY (https://youtu.be/gNYFyritpRY)
I do not understand more then 20% of what they are singing: its is very fast and at the same time a heavy Bavarian dialect.
I mention this band here because I like to adopt the name for the next (and final?) member of the brass band spinning top family. Maybe Jeremy likes to call it LBB for short. I think La Brass Banda is Italian for brass band. Is that true Iacopo?
Yesterday I sent the parts it should be made of to my friend. There is some work on the lathe and some hot air welding soldering to be done.
The main difference with respect to my current top, will be the spokes.
(https://i.ibb.co/xGCQSDJ/SONY-DSC.jpg)
In the foreground the three spokes JBB (Junior Brass Band) is using, the six brass needles in the background are the type of spokes that will go into LaBrassBanda.
So finally I arrive at the thin needles that ta0 suggested as optimal quite a while back (although he changed his mind in the meantime).
There should be 12 (!) grub screws in the brass flywheel for centering the tip, tilting the stem, static balancing and couple unbalance reduction.
As with JBB the position of the tip can be changed vertically to allow for different scrape angles. The stem by which the top is started can be exchanged, that is a part I still expect some changes.
It will be at least a week or two before LaBrassBanda will be back and ready to play with, but I wanted to briefly share the plans already.
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I think La Brass Banda is Italian for brass band. Is that true Iacopo?
"La banda" is italian. Brass band in italian can be translated "La banda di ottoni".
With the much thinner new spokes I believe that you will establish a new record.
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With the much thinner new spokes I believe that you will establish a new record.
Actually the goal for LaBrassBanda is to do just the half hour without pedestal. That is just my personal taste that I prefer spin tops where the contact point is always the lowest point of the whole top. Also with this thinner more fragile spokes a pedestal could be dangerous to the spokes if they can touch the edge of the pedestal.
And yes they are a lot thinner, only 0.5 mm instead of 2 mm, but I will use 6 of them. I did not find anything useful that makes predictions on air drag where number of spokes and thickness of spokes is considered.
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LaBrassBanda is not finished yet, but the base on which it is supposed to spin is here! Junior Brass Band got a cosmetic update and is presenting the new base:
(https://i.ibb.co/cYSwkNK/JBB-on-new-base.jpg)
The base is just a black acrylic plate which is prepared so, that the double domed sapphire sits in it flush to the surface. No more pedestal. The hole visible in the very center allows the sapphire to be pushed out, should it need to be replaced.
JBB got a red aluminum knurl as stem and the threads in the screws that make the spokes are now covered with black heat shrink tube.
Some more impressions:
(https://i.ibb.co/PzVhTmX/SONY-DSC.jpg) (https://ibb.co/PzVhTmX) (https://i.ibb.co/48Pm4t9/SONY-DSC.jpg) (https://ibb.co/48Pm4t9) (https://i.ibb.co/0j08wy1/SONY-DSC.jpg) (https://ibb.co/0j08wy1) (https://i.ibb.co/kJ4zJKj/SONY-DSC.jpg) (https://ibb.co/kJ4zJKj) (https://i.ibb.co/8gbCnsd/SONY-DSC.jpg) (https://ibb.co/8gbCnsd) (https://i.ibb.co/p1LrBtg/SONY-DSC.jpg) (https://ibb.co/p1LrBtg)
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That's a pro spinning base! And Junior Band looks great!
Great work!
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Preview of LaBrassBanda
(https://i.ibb.co/FVzk547/Preview-of-La-Brass-Banda.jpg) (https://ibb.co/FVzk547)
LaBrassBanda is not back yet, there was a misunderstanding and some of the many threads I asked for did not run the direction I wanted them to run, so it will be a few more days until I can play with it. The general look will be like this picture. The red plastic that makes the knurled stem is the cap of a tube of (Italian) tomato paste.
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LaBrassBanda is here!
(https://i.ibb.co/Phpmspk/SONY-DSC.jpg) (https://ibb.co/Phpmspk) (https://i.ibb.co/wM9V1K5/SONY-DSC.jpg) (https://ibb.co/wM9V1K5)(https://i.ibb.co/vjntgtZ/SONY-DSC.jpg) (https://ibb.co/vjntgtZ)
(https://i.ibb.co/BGy2vV6/von-unten-mit-pfeilen-und-legende.jpg)
Some of the newer details can be seen in the big picture, the legend describes their function.
As I said in another post the spokes are 0.5 mm brass pins/needles. They are inserted from the one side through a hole in the hub that is large enough for the pinhead to pass. Then before the needle almost reaches the opposite side of the hub, the hole becomes smaller so that only the bin can pass not the pinhead. The pin can rotate in that position.
After the pins of the correct length were fed through their respective hole, the tip was soldered into holes in the center of grub screws. Then the whole thing could be assembled. All this work, including the fabrication of the adapter and all the threads in the ring, was done not by me but my friend Mr.H. following roughly the ideas I gave him.
Three of the spokes go to the lower end of the hub, the other three spokes to the upper end. This allows not only to center the hub but also to adjust the direction the axle is pointing. This is one advantage over the three spoke design of "Junior Brass Band".
Soooo, now I have a lot of screws to play with but no good strategy how to reach the best dynamic balance possible. I did not take the time yet to seriously balance this top (too busy with intuitive precession stuff ;) ). Up to now I arrived at the point where it spins for 22 minutes before scraping the pedestal free base. Again I am confident that I can break the half hour barrier with this setup before Marines Festival.
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LaBrassBanda looks like it means business! 8)
Again I am confident that I can break the half hour barrier with this setup before Marines Festival.
Do you mean that you going to Marines? :)
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Do you mean that you going to Marines? :)
What can I say, Jim invited me to come and set up a table with some tops.
I feel very honored!
So I accepted the invitation. Hopefully the corona situation will allow it to happen.
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Do you mean that you going to Marines? :)
What can I say, Jim wrote invited me to come and set up a table with some tops.
I feel very honored!
So I accepted the invitation. Hopefully the corona situation will allow it to happen.
8) 8)
Oh, my! It's crazy, my spintop travel budget is going through the roof, but I might have no other option that to also come to this one! :-\ ::) ;D
By the way, I updated the list on the festivals page: https://spintops.org/fests/
(but I have not yet included any in Asia)
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...my spintop travel budget is going through the roof, but I might have no other option that to also come to this one! :-\ ::) ;D
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Marines is only beginning next year! So you will still have most of the budget available for 2022!
Es freut mich, dich dann persönlich zu treffen!
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Es freut mich, dich dann persönlich zu treffen!
Ich würde dich auch gerne zu treffen.
Mareike Schwarz, Mermouy's friend and top player, should also be there. I guess at least I'll hear some German :P
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Iacopo, I copied your reply from the other thread to this one so we can discuss (later) the things related to the ring tops here without having to go about the design problems in my tops in the thread of your beautiful tops.
Two further exquisite Simonelli tops! Congratulations Iacopo!
Thank you, Ortwin !
I also like it that you present this new balancing method.
The new part of the method is the use of the laser pen.
I have been using this method for years, both for static and couple balance. I explained it in a video on my YouTube channel six years ago, a bit more in detail.
With your statements that static balance can best be treated at low speed and couple unbalance at high speed and so on, I am not completely happy. It might be perfectly valid for practical purposes especially with your type of tops with the really sharp pointed tip and if you can statically balance it almost perfectly at low speed first - but if I consider my tops with the 0.5 mm tungsten carbide ball tip things could look different.
I haven't much experience with ball tips but I don't see why it shouldn't work with them, especially with a 0.5 mm ball tip, which is so little and not so different from a pointed tip.
When I used this method with tops having an external 3/16" tip, it worked.
I understand that it is more difficult to use the paint and brush if the top, because of the ball tip, walks on the spinning surface.
Having a short stem, like in your tops, too, doesn't seem to help.
But the difficulty to detect the direction of leaning of the unbalanced top doesn't mean that the method is wrong.
..if you can statically balance it almost perfectly at low speed first..
This is desirable but not always possible, and not so much important anyway.
In the case of these my latest two tops, due to the glass balls, which are empty inside, and with uneven thickness, when I tried to balance them, I found that there was a lot of couple unbalance. For this reason I added the vertical screws, which were not part of the design in the beginning.
After having added the vertical screws, I started balancing the tops at low speed, using only the horizontal screws, until the tops seemed balanced and they didn't wobble anymore. Then I spun the tops at high speed and they didn't appear balanced anymore, there was evident wobble, I corrected it using only the vertical screws. After an important correction of the position of the vertical screws, it is normal that the static balance does not appear so accurate anymore, so at that point I had to check again for the static balance, there was a bit of wobbling, I corrected it with the horizontal screws at low speed, and at that point the overall, (dynamic), balance was good.
You have your top with all those screws, both horizontal and vertical, it is perfect for to experiment with these notions, if you want.
For example, you could adjust the horizontal screws so to make the top statically unbalanced on purpose.
Then you could move the vertical screws and produce a couple unbalance with opposite direction to that of the static unbalance, so that the top could spin apparently balanced. I can show you in which direction to rotate the screws, if you want.
If you try it, you will see that you will be able to make the top to spin apparently balanced, in fact, but only at a certain speed.
Above that speed, the top will wobble, leaned towards the light side, dominated by the couple unbalance.
Below that speed, the top will wobble, leaned towards the heavy side, dominated by the static unbalance.
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I miss your experiments for longest spins, I followed them with interest, and your space station tops were great !
Again I copied this comment from you to this thread because it should not mess up your impressive world record thread.
But you are right Iacopo, I am not very active in the endurance tops experiments lately. At least not to the extend that I could report anything new really.
After I reached that goal of going past 30 minutes with video and spin decay curve and all, my motivation was definitely not as high as it takes to make further progress.
I still have the goal to go past the 30 minutes on a base without pedestal with a single finger twirl, but the first attempts with the ideas I had to reach that goal did not work as well as I hoped: The very thin spokes were not as stable as they should be, the soldering that fixed them to the grub nuts came lose a few times. Since I can't repair that part myself that is a problem.
The other idea that came from Bill Wells, using the vibration sensor of a cell phone for the balancing process, did not work as well as I hoped with the apps I have available.
But really it basically takes more determination and time than I invest to make some progress. My spintop related interest shifted in part to throwing pegtops after my first visit to Marines, so that is part of my lame excuse.
Maybe your new world record inspires and motivates me to continue again with endurance tops.
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Thank you for re-posting this, Ortwin.
I am re-reading it, there are parts that I didn't even remember.
I will reply here, later.
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Have you ever tried to spin this top with multiple twirls ?
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Have you ever tried to spin this top with multiple twirls ?
I have a stem that should allow in principle multiple finger twirls. But when I tried I noticed very soon that the technique requires quite some practice and that it can be dangerous for the top. So I gave up on that telling myself that I prefer for my tops the single twirls start .
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Have you ever tried to spin this top with multiple twirls ?
I have a stem that should allow in principle multiple finger twirls. But when I tried I noticed very soon that the technique requires quite some practice and that it can be dangerous for the top. So I gave up on that telling myself that I prefer for my tops the single twirls start .
I thought that, accelerating gradually the top, would have posed less stress on the spokes.
Also, the higher speed obtained with multiple twirls could make more evident the aerodynamic advantage of your design.
But I understand that you developed it for single twirl spins, and the size of your ring, by itself, seems more suitable for single twirl tops.