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[Iacopo]

I designed and made this particular finger top aimed for very long spin times in absence of air.  Started at 2200 RPM, it kept spinning for 4 hours and 16 minutes. Details in the video.

[jim in paris]

salute à tutti !

Avanti Professore !

really trippy !
thank you for showing this incredible experience
i like the decay time chart : such a smooth curve ;--)

à piu tarde
jim

[Iacopo]

Thank you, Jim.

This top was not extreme, it could be made lighter and/or larger, without much difficulty, and it would certainly spin even longer.

[Neff]

Exellent! I am curious what a typical spin might be without the vacuum.

[Iacopo]

Exellent! I am curious what a typical spin might be without the vacuum.

Thanks.  Without vacuum it spins for about little less than half an hour.
The same reasons that make this top efficient in vacuum conditions, (lightness and large diameter), make it inefficient relatively to air drag.   

[Jeremy McCreary]

Thanks.  Without vacuum it spins for about little less than half an hour.

Strong experimental work as usual. As I said on YouTube, this simple but elegant top may be my favorite of yours from a visual standpoint. Spin time under air isn't everything.

[the Earl of Whirl]

That is quite a video.  And the spin time is incredible, even if it is in a vacuum!!!

I am intrigued by your style of snap start.  Your constant twisting really gives it a powerful start.

[Iacopo]

Strong experimental work as usual. As I said on YouTube, this simple but elegant top may be my favorite of yours from a visual standpoint. Spin time under air isn't everything.

I didn't want to make anything sophisticated here.  I have little free time so I made this top very simple and unrefined, because this was just an experiment.  Even, the design is not extreme; it would be possible to make the top lighter and larger, (it would spin longer).
I didn't care about spin time under air, this one was specifically made only for vacuum conditions.   

[Iacopo]

Your constant twisting really gives it a powerful start.

Yes, true.  Generally by a constant twisting the starting speed is doubled, or little more than doubled, in my tops.
I can start this top at 1100 RPM, by a single twirl.  In this case it would spin for about 2^h 50^m, in the vacuum.

[ta0]

Fantastic! I'm so glad that you did this! 

Newton's first law: an object moving continues to move unless something (like resistance) stops it. There's the proof! 

You still have to spin it in air and then it takes a little time to close it and pump out the air. I'm thinking that with magnets it could be spun when it's already in vacuum. While you are starting it, it's hanging (or just stands up) and once it spins well you raise the driving magnet until the top falls into the base.

[Aerobie]

Wowwwwweeeee!   Congratulations Iacopo on an amazing twirl.

Tell us more:

Tip design (shape, size)?
Surface material, shape?
Lubricant type?

In a vacuum, the possibilities are enormous.  A few months ago I stumbled on a video of a very large diameter top which was "un-weighted" by a magnet pulling it upward on its steel stem, reducing tip weight.

Best regards,

Alan

[Aerobie]

It appears to me, that diameter is nearly irrelevant at higher speeds in air. 

At a given RPM the surface velocity at the perimeter of a top is proportional to diameter and aero drag (at very low Reynold's numbers) is proportional to velocity.  So the aero drag at the perimeter would be proportional to D^2.  Then the surface area of the perimeter increases with diameter, so we have aero drag at the perimeter proportional to D^3.   Furthermore, the perimeter's braking torque at the axis is proportional to D.  So we have total braking torque = D^4.  This is only countered by inertia, which equals diameter squared.  This leads to D^4 / D^2 = D^2 as a decay factor for diameter.  That is larger decays faster.

Despite that, when I compared two 48 gram tops, both on 3/8" balls, with diameters of 1" and 2", their decays in the range of 800 to 1,000 RPM were about equal.

I also compared 1" and 1.25" tops of the same weight and ball diameter, but closer in configuration than the 2" above.  In the range of 1,000 to 1,400 RPM, the 1.25" top has slightly lower decay.

Of course diameter helps at low speed.

Alan

[Iacopo]

You still have to spin it in air and then it takes a little time to close it and pump out the air. I'm thinking that with magnets it could be spun when it's already in vacuum.

Clever idea, Ta0 !
In fact, one reason why I didn't make the top even larger and lighter, is that it would lose too much speed because of air drag, before the air is pumped out.

[Iacopo]

Tip design (shape, size)?
Surface material, shape?
Lubricant type?

It is a carbide spiked tip.  It is the tip with the lesser friction I know, when spun on a carbide spinning surface.
The tip friction of the top you sent me, spinning on a glass mirror, is about three times higher than that of spiked carbide tips spinning on carbide.
 
I used the turntable bearing lubricant which is sold together with this ruby ball:

https://www.amazon.co.uk/IsoKinetik-ISObear-Bearing-Upgrade-Turntables/dp/B01D6MX1SG/ref=sr_1_3?ie=UTF8&qid=1520160466&sr=8-3&keywords=ruby+turntable

I put about 0.2 mm of oil in the spinning surface. It is a thin layer of oil, but the quantity is enough to form a meniscus of oil around the tip.  So the tip is submerged in the oil and there is no possibility for the oil to be dislodged as it can happen with a very thin layer of oil.
This oil is good but not very different from other oils I used.  Motor oil too is good.
 

 

[Aerobie]

Interesting.  My experience is that a thick layer of oil increases drag.

Alan