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Author Topic: Curtain Ring tops + follow ups  (Read 3193 times)

ortwin

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Re: Curtain Ring tops + follow ups
« Reply #105 on: April 20, 2021, 03:07:37 AM »

...
...a practiced hand might get faster stemless releases by allowing some scrape beforehand.

..
Just a note on the spin up technique  I am using at the moment with "Easy Listening" and "Brass Band".
I grip the ring at the outside with all my five fingers of the (right) hand. I find I get best results when my arm is stretched downward. So I put the base with the top on the floor and either bend over it or sit on a chair next to it. Trying to start them on a table I find I have less control and speed.
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Jeremy McCreary

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Re: Curtain Ring tops + follow ups
« Reply #106 on: April 20, 2021, 03:30:03 AM »

CONGRATS! Very well done! Even better when considering the AMI disadvantage (factor two roughly?) you had to cope with.
The black light pictures are very cool. Did you get to filming "Skimpy String Top" in the same black light session?
In one of the pictures it looks to me as if you had used only one string and one knot. I had thought about that possibility, but found it too hard to balance with that setup. It is of course a lot easier if you can tension/position the different spokes somewhat independently.

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

You and Iacopo have kept me too busy to shoot the skimpy all-chain blacklight top. Decided to show it along with some other blacklight tops made since my last video on this subject. Have the stills under visible light (to reveal at the end), but no video yet.
« Last Edit: April 20, 2021, 04:11:23 AM by Jeremy McCreary »
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Playing with the physical world through LEGO

ortwin

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Re: Curtain Ring tops + follow ups
« Reply #107 on: April 26, 2021, 04:12:29 AM »

 Primary Brass Band
 Since “Kindergarten Brass Band” is gone out to get some nice piercings and stuff, and wants to come back as some sort of “Junior Brass Band”, its elder sibling took its chance to show off:
 So here is, “Primary Brass Band”!



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.


click to animate

 
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ta0

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Re: Curtain Ring tops + follow ups
« Reply #108 on: April 26, 2021, 09:55:09 AM »

You beat the Spartan top!  :o I wasn't expecting that! 18:36!  :o 8)

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

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Re: Curtain Ring tops + follow ups
« Reply #109 on: April 26, 2021, 10:04:27 AM »

You beat the Spartan top!  :o I wasn't expecting that! 18:36!  :o 8)

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


Well, in the nut that makes the hub, are 3 small holes I made with a 0.6 mm drill. The hub I used for "Easy Listening" before.
Once I break the 20 minutes barrier I will post a video of a full length spin, before that maybe not.
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Jeremy McCreary

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Re: Curtain Ring tops + follow ups
« Reply #110 on: April 26, 2021, 11:15:43 AM »

Wow, 18:36 with mostly solid spokes! Looks good, too.

How thick are those turnbuckles at their widest?
« Last Edit: April 26, 2021, 11:19:39 AM by Jeremy McCreary »
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ortwin

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Re: Curtain Ring tops + follow ups
« Reply #111 on: April 26, 2021, 02:17:50 PM »

...
How thick are those turnbuckles at their widest?

"Turnbuckle", nice word, seems to be the correct technical term for what I am using.
3 mm at their widest.
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Jeremy McCreary

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Re: Curtain Ring tops + follow ups
« Reply #112 on: April 26, 2021, 06:26:53 PM »

Depending on the mood of our kitchen scale it weighs in at 119 g up to 124 g.  Inner diameter ~77 mm, outer diameter ~93 mm. Height ~8 mm. 

Just to confirm, the 18:36 spin time was with the brass ring above?
« Last Edit: April 26, 2021, 10:32:18 PM by Jeremy McCreary »
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ortwin

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Re: Curtain Ring tops + follow ups
« Reply #113 on: April 27, 2021, 01:30:21 AM »

Depending on the mood of our kitchen scale it weighs in at 119 g up to 124 g.  Inner diameter ~77 mm, outer diameter ~93 mm. Height ~8 mm. 

Just to confirm, the 18:36 spin time was with the brass ring above?
Affirmative!
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ortwin

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Re: Curtain Ring tops + follow ups
« Reply #114 on: April 30, 2021, 04:02:08 PM »

Maybe I should ad a stem after all?
I am seriously considering adding a stem to a future version of "Brass Band" (I know Jeremy, you thought that all along).
The thought came to me after I dared comparing my results to a top of Iacopo: Nr. 26
On his YouTube channel he has a video up where I took this screenshot is from:


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.
« Last Edit: April 30, 2021, 04:21:02 PM by ortwin »
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Jeremy McCreary

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Re: Curtain Ring tops + follow ups
« Reply #115 on: April 30, 2021, 09:12:11 PM »

Handy way to assess the spin time changes you can expect from a given change in either release or critical speed in a given top:

Δt = t2 - t1 = T1/e ln(ω1 / ω2)

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

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

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

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

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

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

T1/2 = T1/e ln 2 = 0.693 T1/e
« Last Edit: April 30, 2021, 09:17:41 PM by Jeremy McCreary »
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ortwin

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Re: Curtain Ring tops + follow ups
« Reply #116 on: May 04, 2021, 02:36:49 AM »

A sneak preview of JBB (Junior Brass Band)
JBB sent  a picture so I would know how it looks like when it comes back,  and how much "Kindergarten Brass Band" changed since it left.

Promising I'd say!



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ortwin

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Re: Curtain Ring tops + follow ups
« Reply #117 on: Today at 04:16:33 AM »

Primary Brass Band
 ....
The times are better then my best times with the “Spartan Top” ...
The Spartan fought back!
It managed to spin for 27:45   (Edit 32:02  in another try).
But it was disqualified for cheating badly! Should be lucky that it is not banned for lifetime!
It was done in vacuum.

« Last Edit: Today at 05:44:19 AM by ortwin »
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Jeremy McCreary

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Re: Curtain Ring tops + follow ups
« Reply #118 on: Today at 10:46:36 AM »

JBB looks great! Eager to see it in action. Spartan can be forgiven for getting desperate.
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ta0

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Re: Curtain Ring tops + follow ups
« Reply #119 on: Today at 12:20:08 PM »

Nice!  8)

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

I would like to have a vacuum setup. Perhaps one day . . .
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