Print

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

[Iacopo]

Did you ever consider making versions where that energy loss is compensated by some external source like candles or the sun?

Once I thought to make a top with blades like an anemometer, in a windy day the top could spin never stopping. If the tip is recessed, probably it could work.

A top based on the Christmas pyramid principle, moved by the hot air of the candles, I believe that too could work. Even in this case, I suppose that the CM should be very low on the tip, for the top to be sufficiently stable to spin slowly enough without falling down.

But generally I prefer to look for long spin times by reducing the frictions, without adding energy, and keeping the design as simple as possible.

[jim in paris]

Bravissimo
cum'ellu passa u tempu !

Jim

[Jeremy McCreary]

(Lately I keep thinking that at least you, Jeremy and myself should get something like this:https://www.reichelt.com/ch/de/drehzahlmesser-digital-usb-ut-372-p141795.html
A speed meter with an USB interface. We would have the full data of a spin without having to write down anything. Those things are not so expensive either. Any experiences with a specific model anybody?)

This non-contact tachometer has the kind of data logging I'd want, but at $310, it's a lot more expensive...

https://www.amazon.com/gp/aw/d/B015J3L9HA/ref=ox_sc_act_image_1?smid=ATVPDKIKX0DER&psc=1

The most useful data would be a stream of (time,speed) pairs suitable for spreadsheet analysis. Not sure that's what the one you linked puts out.

[ortwin]

...
A top based on the Christmas pyramid principle, moved by the hot air of the candles, I believe that too could work. Even in this case, I suppose that the CM should be very low on the tip, for the top to be sufficiently stable to spin slowly enough without falling down.
But generally I prefer to look for long spin times by reducing the frictions, without adding energy, and keeping the design as simple as possible.

I like those design principles as well, never the less I think I will try something with the flywheel of "Easy Listening". In recessed mode it can go as slow as about 70 RPM. I hope I can get it working before next Christmas! But Christmas comes every year very sudden and fast!

[the Earl of Whirl]

Amazing!  Just simply amazing!!!

[Iacopo]

Is it possible to get to 1 hour with one twirl using a tungsten top and a shroud? Is it possible to get to 1 hour with multiple twirls but an external tip? I'm guessing both are not possible, but I wouldn't bet against your skill.

My best spin with a very basic finger top, (brass flywheel, external tip, single twirl), is 29 m 38 s, about half an hour.

Some things that can be used for to have longer spins:


-  Recessed tip. Advantage 34 %

-  Multiple twirls.  Advantage 16 %

-  Optimizing the size of the top for multiple twirls, making it heavier and larger.  Advantage 38 %

-  Tungsten instead of brass.  Advantage 22 %

-  Shroud.  Advantage 11 %


The estimate of the advantages is rough and very approximately valid for the design of my tops.
The advantages are cumulative.

For example:
If I add the recessed tip to the basic top, I can expect it to spin with a single twirl for about:
30 x 1.34 = 40 minutes
If I use the recessed tip and multiple twirls, the spin time could be:
30 x 1.34 x 1.16 = 46 minutes
Basic top with tungsten instead of brass:
30 x 1.22 = 36 minutes
Recessed tip, multiple twirls, size optimized for multiple twirls, shroud:
30 x 1.34 x 1.16 x 1.38 x 1.11 = 71 minutes

As for the tops you have asked about:
Single twirl, external tip, tungsten and shroud:
30 x 1.22 x 1.11 = 40 minutes
Single twirl, recessed tip, tungsten and shroud:
30 x 1.34 x 1.22 x 1.11 = 54 minutes
External tip, multiple twirls, size optimized for multiple twirls, tungsten:
30 x 1.16 x 1.38 x 1.22 = 58 minutes

All the advantages together:
30 x 1.34 x 1.16 x 1.38 x 1.22 x 1.11 = 87 minutes

[Iacopo]

These are the spin dacays:

Red line:  Top Nr. 54, (68.5 mm, 364 grams), with shroud
Orange line:  Top Nr. 55, (60 mm, 291 grams), with shroud
Brown line:  Top Nr. 55 without shroud
Green line:  Top Nr. 23, (60 mm, 298 grams)

[ortwin]

...
All the advantages together:
30 x 1.34 x 1.16 x 1.38 x 1.22 x 1.11 = 87 minutes

So you are saying with platinum one and a half hour is within reach?

[Iacopo]

[quote author=Iacopo
...
All the advantages together:
30 x 1.34 x 1.16 x 1.38 x 1.22 x 1.11 = 87 minutes

So you are saying with platinum one and a half hour is within reach?

So it seems.

[ta0]

Thanks a lot Iacopo!
This is a very valuable contribution to the knowledge base of the spinning top art.
You are tops!

[ortwin]

...
My best spin with a very basic finger top, (brass flywheel, external tip, single twirl), is 29 m 38 s, about half an hour.....

That is the category I am going for!
In fact not exactly, I think you use a dedicated base where the rim of the flywheel can sometimes be below the height of the tip. I want to try to get to the half hour on a slightly concave base like the one I used for the 18:36 of "Primary Brass Band". With the next version (solid spokes, maybe a stem) I am confident to go past 25 minutes - we will see.
So, tell us Iacopo, how does it feel to have broken that magical barrier of one hour twice within 24 hours? Even with  two different new tops?What will you do next? Will you go to Disneyland?

[Iacopo]

I show you something:

this is a graph about the efficiency of three my tops.
This efficiency is calculated as the percentage of RPM retained after one minute of spinning.
For example, these are the data of the first five minutes of spinning of my new record:

Minutes     RPM      Efficiency
0              2917
1              2759       94.6%
2              2607       94.5%
3              2469       94.7%
4              2339       94.7%
5              2220       94.9%

The calculation is made in this way:
2759 : 2917 = 94.6, percentage of RPM retained after the first minute of spinning.
2607 : 2759 = 94.5, the same for the second minute of spinning,
and so on.

These data, (efficiency vs. RPM), plotted in a graph help comparing the performances of different tops. 





I start comparing these three old tops, (then I will add the data of the new tops):
the most efficient one of these three is the biggest one, the Nr. 9.
The least efficient one is the littlest one, the Nr. 14.

At parity of starting speed and toppling down speed the most efficient top would be the one which spins longer.

But heavier tops are more difficult to spin fast so they are started at a lower speed; the Nr. 9 is so heavy that I couldn't even reach 1000 RPM starting speed with it, and the best spin of this top is only 41 m 25 s, in spite of its excellent efficiency, (this top also has an external tip so it topples down soon, at about 135 RPM, this too shortens the spin; the external tip does not deteriorate the efficiency of the top, in any case).

On the other hand, the Nr. 14 is the lighter top, the easiest to spin fast.
I can start this top at 2760 RPM by multiple twirls, many more than with the Nr. 9.
But being littler/lighter/with less AMI, its efficiency is lower,and slows down more rapidly.  Its best spin is 46 m 15 s.

The Nr. 23 has an efficiency in between.  In spite of being quite heavier/bigger than the Nr. 14, I can start it at almost the same RPM, (2717);  so it has the best compromise between efficiency and starting speed, and its best spin by multiple twirls is 58 m 19 s.

The problem with the Nr. 14 is that there is a limit in the speed of the fingers. Whatever the weight of the top, I never have been able to spin a finger top to much more than 3000 RPM. So, reducing the weight/size/AMI of the top, over a certain limit, will reduce its efficiency without the advantage of a significant faster starting speed, and the spin times will be reduced.
   

[Jeremy McCreary]

Strong work as always, Iacopo! Totally agree with ta0.

Would you be willing to share the data behind those earlier spin decay curves for Nr. 55, 54, and 23? Among other things, I'd like to see how exponential they are -- especially in their low-speed tails.

You've given masses and diameters for these 3 tops. Any other specs you have time to share would be great -- especially estimated CM height,  flywheel axial length and inner diameter, and measured AMI if you have it.

Thanks!

ortwin found an affordable laser tachometer with data logging to a laptop via USB cable and included software. I'll let him share the details.

Once mine comes, I hope to be posting high-quality decay data and curves on selected tops in my collection, LEGO and otherwise -- including the peg tops and komas I can launch upright with one of my starters.

[ortwin]

...and the best spin of this top is only 41 m 25 s.......

Poor Iacopo !  It might comfort you when I cite a wise person once (or twice) saying: "Spin time is not everything!"   

No seriously, thank you for sharing these results and the deeper insights.

The tachometer I suggested earlier and that Jeremy mentioned is this one:UNI-T, UT 372 with USB interface and software. At amazon Germany

A video about the software.


I don't have it, I let Jeremy do the testing for us!

[Jeremy McCreary]

Which of these has the greatest overall play value for you personally? The least?

One way to assess that: If all 3 were on a table, ready to spin, and you had a few minutes to kill but could only play with one, which, on impulse, would it  be? Why?

Same questions for the Nr. 54, 55, 23 trio.