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[Iacopo]

This is my latest spinning top, a little one with tungsten alloy flywheel and titanium stem.
The little egg case, 84 mm tall, contains both the top and the pedestal for the top, (the tip is recessed).



Two days ago I was here, at Prati di Sara, (Apennins), for making the video of the new top:





I find this place very beautiful. Here you can find free horses, I love to see them too.
Sara is also the name of the only one girl I loved in my life, but this is not a factor, (perhaps).



This is the video of the top:

https://youtu.be/R2Hz-M4eh9g

[Texture]

BEAUTIFUL TOP!!!  The egg case is nice too! 

[ta0]

The legend goes on . . . 

A beautiful landscape to showcase another exquisite top!

Is this tungsten top an exception or do you plan to use this metal again?

[Jeremy McCreary]

ta0 took the words right out of my typing finger!

Aside from test tops, don't recall seeing a straight-edged flywheel from you before. Special commission?

[Iacopo]

BEAUTIFUL TOP!!!  The egg case is nice too! 

Thank you, Texture.  The egg is a lot of work and it doesn't cost much less than the top itself, so I don't make the cases often, they are nice but clients usually give up.

[Iacopo]

Is this tungsten top an exception or do you plan to use this metal again?

Thanks for the compliments, Ta0.

At present, I am not planning to make other tungsten tops in the future.

The biggest problem with tungsten is that my fiscal expert says that I must have an invoice for every material I use for things to be sold.
But I can't find tungsten for sale in Italy and it is difficult to have a regular invoice when purchasing from abroad.

Another problem is that tungsten alloys seem to have dishomogeneous density, and tops made with it need to be balanced, (I seem to remember that this was stated in this Forum too);  in my case, I made two tungsten tops, (the tungsten alloy I used is W80CU20), and they both were badly unbalanced when I made them. 
Usually I fine tune the balance of my tops, (if there are not the screws), by sanding a bit the outer part of the flywheel, where needed;
very little sanding is generally needed.
But my tungsten tops were so much unbalanced that I should have sanded enough to make the shape of the flywheel clearly asymmetrical, which is not acceptable.
In this new top, instead of sanding, I drilled a hole at one side of the flywheel to remove weight there, and closed it with a piece of titanium.

Another problem is that tungsten is very hard to machine, and difficult to sand and polish.
But the most important problem by far is the first one I mentioned. 

[Iacopo]

ta0 took the words right out of my typing finger!

Aside from test tops, don't recall seeing a straight-edged flywheel from you before. Special commission?

Thank you, Jeremy.

The shape of the flywheel was dictated by the facts that the tungsten plate I have here has only 8 mm of thickness, and I was not willing to buy new tungsten.  Then the client wanted a little diameter.  But also he wanted long spins.  The straight-edged flywheel is a trick for to maintain more moment of inertia, which is important for long spins, in spite of the limits of thickness and diameter.
This 120 grams top, with 41.4 mm of diameter, can spin for up to 30 minutes with a single twirl.

My tops Nr. 18 and 19 too have straight-edged flywheels, but not so much like this new top.

[ortwin]

...
This 120 grams top, with 41.4 mm of diameter, can spin for up to 30 minutes with a single twirl.

...

Beautiful!
But why do you call it a EDC top? To me that sounds a few leagues below yours.
 
30 minutes you say? But still less than the tungsten top you mentioned in reply #236 in the curtain ring top topic?
I can't watch the video here in holidays, not such good internet connection, so maybe you gave the information aheady there: starting speed? Topple speed?

[the Earl of Whirl]

I want to touch it!!!  I want to hold it!!!  I can’t stand not having my hands on it!!!

[Joah]

That is an absolutely beautiful top!

[Jeremy McCreary]

I want to touch it!!!  I want to hold it!!!  I can’t stand not having my hands on it!!!

This is known in medicine as fulminant Simonellitis. I have a relapsing case.

[Iacopo]

30 minutes you say? But still less than the tungsten top you mentioned in reply #236 in the curtain ring top topic?
I can't watch the video here in holidays, not such good internet connection, so maybe you gave the information aheady there: starting speed? Topple speed?

Yes, I made another tungsten top in the past, the Nr. 30.

The two tungsten tops have practically the same weight, (119 grams the old one, 120 grams this new one), but the new one is much more compact and littler, (diameter 41.4 mm vs 57.5 mm).

Here is a comparison between the spin data of the two tops, spun by a single twirl:

                                 Nr. 30      Nr. 57

Starting speed            1225        1120
Speed after 10 m         629          612
Speed after 20 m         360          336
Speed after 30 m         211          150
Topple speed               140          130
Time                       36m 11s    31m 00s

The starting speed is higher in the old top, in spite of its quite higher moment of inertia, (little more than double of that of the new top);  this is due to the long stem of the old top that allows for more aggressive spinning without losing control and risking to exit from the little spinning surface.

At high speed the Nr. 57 loses RPM more slowly than the Nr. 30.
But below 550-600 RPM things reverse and the Nr. 30 becomes more efficient in keeping RPM.
For the longest time the two tops spin below 550-600 RPM and in the whole the efficiency of the Nr. 30 is better.

   
 

[ortwin]

.
.
Topple speed               140          130
Time                       36m 11s    31m 00s

But why are the topple speeds for these  tops so high?
 
I mean the new one has even a recessed tip right? JBB with external tip, I have seen spin for eight more minutes when down to 130 RPM.

[Iacopo]

But why are the topple speeds for these  tops so high?

Because the radius of gyration also matters for the topple speed, and in my tops this radius is little compared to that of JBB.
There is a formula which predicts the topple speed of tops, Ta0 and Jeremy know it.

The Nr. 57 has the tip recessed, not deeply, and a little radius of gyration.
The spiked tip too doesn't help in this regard.
But if I want, I can easily replace the tip and use a shorter one, this would lower the CM on the tip and improve the topple speed.
With a deeply recessed tip the topple speed can be drastically reduced, but the problem with it is that, when a microscopical flattened area forms in the contact point of the tip, because of wear out, the top could end spinning in vertical position, without toppling;
I don't like this very much, so I prefer not to recess the tip too much. 

[ortwin]

...
I don't like this very much, so I prefer not to recess the tip too much.

Ah, that explains it! Somehow I thought, when you go with a recessed tip, it would always be deeply recessed so that the contact point is very close to the center of mass.
So, you did observe that what I call 'Kemner effect' in your tops also?