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[James]

Hi there!

I've managed to break the one hour barrier with a positive cog top, started with multiple twirls, without a shroud! I believe Iacopo has done this as well but I am none the less thrilled!! With Mk.22, I have set a new personal best by over 14 minutes. I am still perfecting it (balance, finish etc) and believe there may be a little room for an even better performance, but this morning I achieved (and filmed) a 1:02:29 spin.

Yesterday, before lowering the cog and properly balancing it, I achieved a 52 minute spin (which I filmed) and used for taking RPM decay measurements. I am attaching the data.

Raw Time   Time (s)   Time (min)   RPM   Efficiency (RPM retention over 1 minute)
511   0   0.00   2370   
571   60   1.00   2217   93.54%
639   128   2.13   2082   93.91%
690   179   2.98   1991   95.63%
750   239   3.98   1880   94.42%
814   303   5.05   1789   95.16%
873   362   6.03   1719   96.09%
934   423   7.05   1626   94.59%
993   482   8.03   1551   95.39%
1055   544   9.07   1475   95.10%
1114   603   10.05   1409   95.53%
1175   664   11.07   1336   94.82%
1229   718   11.97   1282   95.96%
1293   782   13.03   1218   95.01%
1354   843   14.05   1164   95.57%
1410   899   14.98   1118   96.05%
1473   962   16.03   1065   95.26%
1545   1034   17.23   1003   94.18%
1597   1086   18.10   965   96.21%
1658   1147   19.12   922   95.54%
1711   1200   20.00   881   95.55%
1774   1263   21.05   838   95.12%
1834   1323   22.05   799   95.35%
1899   1388   23.13   758   94.87%
1952   1441   24.02   724   95.51%
2017   1506   25.10   687   94.89%
2075   1564   26.07   651   94.76%
2137   1626   27.10   618   94.93%
2192   1681   28.02   597   96.60%
2260   1749   29.15   558   93.47%
2312   1801   30.02   536   96.06%
2378   1867   31.12   500   93.28%
2438   1927   32.12   470   94.00%
2494   1983   33.05   450   95.74%
2559   2048   34.13   420   93.33%
2616   2105   35.08   397   94.52%
2679   2168   36.13   375   94.46%
2732   2221   37.02   345   92.00%
2795   2284   38.07   334   96.81%
2855   2344   39.07   307   91.92%
2912   2401   40.02   289   94.14%
2972   2461   41.02   272   94.12%
3031   2520   42.00   248   91.18%
3092   2581   43.02   224   90.32%
3155   2644   44.07   206   91.96%
3217   2706   45.10   188   91.26%
3282   2771   46.18   167   88.83%
3331   2820   47.00   150   89.82%
3394   2883   48.05   133   88.67%
3450   2939   48.98   116   87.22%
3510   2999   49.98   100   86.21%
3584   3073   51.22   83   83.00%
3670   3159   52.65   60   72.29%

And here are some basic graphs to visualise it:





The decay does not seem to be exponential or low-order polynomial. I suspect it is a combination of exponential decay and linear.





I have zoomed into the 70-100% efficiency range but really, the efficiency looks quite constant [measured as ((RPM at min 2) - (RPM at min 1 ))/ RPM at min 1]
It peaks at around 96%

I'll do another post about this top soonish but was too keen to share this good news!
Thanks for reading and let me know if you have any comments or suggestions.

James

[Iacopo]

I've managed to break the one hour barrier with a positive cog top, started with multiple twirls, without a shroud! I believe Iacopo has done this as well but I am none the less thrilled!!

This sounds fantastic ! Congratulations, James !
I never reached one hour without a shroud. My Nr. 54 would have been able, I believe, but I never tried.

What did you improve in the mk.22 ?  It is a larger size top ? Did you use tungsten ? Did you find better contact points ? I would like to see it.

[James]

Behold Mk.22!









Here are the specs:

Weight - 386g
Diameter - 70mm
Height - 76mm
Flywheel Height - 13mm
Flywheel wall thickness - 9mm
Flywheel material - 90/10 Tungsten Copper
Core material - Aluminium
Tip - Conical Tungsten Carbide
Base - Concave Tungsten Carbide

The geometry was determined using an equation I have been developing which relates a load of variables to spin duration. It is a work in progress but this good result gives me hope!

[Iacopo]

It's a nice top, with nice proportions.

How much hard was to work with the 90/10 tungsten alloy ?  I remember the 80/20 was already quite difficult, and I never worked with a material harder than that.

[James]

It was actually not bad because I did most of the machining for it on my university's lathe - it is a LOT better than mine at home (very solid). Some sharp carbide tools, coolant and decent RPMs and it cut similar to brass!

Thanks

[ortwin]

Excellent James! Congratulations!!!!

Just need some details for my understanding:
What exactly do you mean by "positive cog top" ?
Does that top have a recessed tip? If so, by how much.
Out of curiosity, what is the RPM you reach with a single twirl (I know it makes not much sense with this top, its weight and all is designed for multiple twirls)?


I'm looking forward to more pictures and videos!

[the Earl of Whirl]

Very cool!!!

[James]

Thank you!!

What exactly do you mean by "positive cog top" ?
Does that top have a recessed tip? If so, by how much.
Out of curiosity, what is the RPM you reach with a single twirl (I know it makes not much sense with this top, its weight and all is designed for multiple twirls)?

I mean the centre of gravity is above the contact point, it can topple so it isn't a "true" maxwell style top.
Yes, it has a deeply recessed tip around 6mm above flat ground.
It seems I achieve about 400rpm, however my single-spin technique is not that good and I specifically under-knurled for aero reasons!

[James]

I have made a video about this spinning top! It gives some of my thoughts and more details and clips. I will release the full spin as a separate video perhaps next week.



I claim it to hold the world record, though in the description I explain the specifics (no shroud, vacuum, batteries etc). I have given credit where I think it is due (Iacopo and LIMBO) but do let me know if you think you or someone else should be included or if I should change my wording. I did it partially for the content but also I am very proud haha.

I am considering making a small batch of tops similar to this design. I think it would be fun and good experience. I am considering a tapered replaceable tip design such that the customer can use either a spike tip which they will have to manually balance (higher performance) or a small ball tip (lower maintenance). I'll keep you updated if there are interesting developments!

I was originally going to make this another post but I don't think thats necessary lol
Thanks for reading!

[ta0]

Great achievement, James! You worked hard to accomplish this!

The video summarizes very well design compromises to achieve a long duration. However, you say that the stem is slightly milled to decrease air drag: I don't think this has been proven.

I do however have a complaint. I don't think you give Iacopo enough credit. The design is very much the same that Iacopo originally developed. Not only that, but he personally gave you advice all the way. Your advantage is that you made it out of tungsten instead of brass. It was always clear that if Iacopo made it out of tungsten it would spin longer. The debate of what is acceptable for a world record finger top duration is unlimited: shroud or no shroud, one twirl or multiple twirls, countersunk tip or protruding tip, etc. You certainly did excellent work and I congratulate you, but your are a disciple of the Master.

[Iacopo]

I don't think you give Iacopo enough credit. The design is very much the same that Iacopo originally developed. Not only that, but he personally gave you advice all the way.

Honestly, he gave me credit various times, in the past.
But recently something seems changed, in his mind, maybe because he wants to sell them.
He started acting like wanting people to believe that this is totally his own work and merit, which is not, obviously.
But it's my fault, because even at my not so young age, still I don't get how the world works.
I used to say too much...



 

[Jeremy McCreary]

Congrats on your new top and spin time, James. A very elegant profile from the side. The video was also nicely done.

Looking forward to hearing more about your spin time equation. For a theoretical top with a spin decay described by

dw/dt = -k wⁿ,

where w is angular speed, t is time, k is a positive constant, and n is a positive exponent, it's easy to do a separation of variables. You can then solve for w(t) and also integrate on t to get spin time. But even for real tops with empirical decay curves with excellent fits to various exponents, the predicted spin times are way off.

Finally, I have to agree with ta0. The Mk.22 is clearly a Simonelli top with important enhancements and should be identified as such in the video narration and description. Nothing wrong with building on the work of others as long as the extent of the debt is clearly acknowledged.

[Iacopo]

Looking forward to hearing more about your spin time equation.

I am a bit skeptical about it, especially because of the problem of the lacking data about the tip friction and air drag, which make these kind of equations approximative and not very useful.
What is certain is that he knew the numbers from me; I suggested him to make the flywheel 70 mm, and he did.
And the weight of his top is almost the same of my longest spin top, which he knew.
   

The Mk.22 is clearly a Simonelli top with important enhancements and should be identified as such in the video narration and description. Nothing wrong with building on the work of others as long as the extent of the debt is clearly acknowledged.

Thank you, Jeremy. 
Well, important enhancements... I see just one, the use of tungsten instead of brass.

 

[Iacopo]

I will try to beat James' record.
I just made a new top for the aim, the Simonelli 73.
Now I am balancing it, tomorrow I will see how long it can spin.