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[Iacopo]

my most energetic and most erratic rebounds always come when the top rotor has "side relief" positioned to interact directly with rails or other fixed bumpers. 

Very interesting findings, which makes totally sense to me.
Those holes would seem to me for generating a whistle. But I thought that maybe the protruding rings of those tops could have slightly elliptical shape instead of perfectly circular, and this could produce the same effect as if they had side reliefs.

[Jeremy McCreary]

So the key is a very slightly convex tip and the top should have the right height to interact with the bumpers. Your table is perfectly horizontal.
On an email Cyril confirmed that he checked the table using a level tool.

Forgot to mention that my LEGO experiments are completely consistent with these findings as well. And I get even livelier action when the tip profile includes a central flat.

Those holes would seem to me for generating a whistle.

That was my first thought, too, but now I'm betting that those holes do more than whistle.

...I thought that maybe the protruding rings of those tops could have slightly elliptical shape instead of perfectly circular, and this could produce the same effect as if they had side reliefs.

Ha, never occurred to me but entirely possible! Tops with elliptical rotors can spin quite smoothly. They just need some extra speed to stay up.




The example above has a much lower (CM height) / (maximum rotor radius) ratio than a typical Toupie Hollandaise or skittles top. I'll test it to see if that's important.

Addendum: But wait -- wouldn't elliptical rotor overhangs become a big liability during spin-up?

[Jeremy McCreary]

...I thought that maybe the protruding rings of those tops could have slightly elliptical shape instead of perfectly circular, and this could produce the same effect as if they had side reliefs.

Tops with elliptical rotors can spin quite smoothly. They just need some extra speed to stay up.... The example above has a much lower (CM height) / (maximum rotor radius) ratio than a typical Toupie Hollandaise or skittles top. I'll test it to see if that's important.

Not important -- raising the (CM height) / (maximum rotor radius) ratio on the elliptical LEGO top above increases critical speed significantly, but the top still spins quite smoothly.

[Iacopo]

raising the (CM height) / (maximum rotor radius) ratio on the elliptical LEGO top above increases critical speed significantly, but the top still spins quite smoothly.

One possible way to overcome this problem could be to shape the inner hollow part of the top in a way to compensate for the protruding parts, so to have a symmetrical top from the point of view of the distribution of weight.
I don't know if the toupie hollandaise has some kind of side reliefs. If not, I think you had a great idea for improving the original design.

[Jeremy McCreary]

I don't know if the toupie hollandaise has some kind of side reliefs. If not, I think you had a great idea for improving the original design.

The tops Bert showed definitely do, as the side holes act as flats. Would love to see Cyril's tops up close.

[ta0]

Would love to see Cyril's tops up close.

They will be thoroughly inspected this coming February. 

[Cyril]

Bonsoir,
Le trou dans la toupie sert uniquement à faire siffler la toupie.
La toupie est en acier, très lourde et sa force d'inertie est très importante.
Sa vitesse est très rapide et donc son sifflement est très très puissant.
Bonne soirée à tous.
Cyril

[Cyril]

La toupie mesure 9,2 cm , son diamètre est de 6 cm et son poids set de 182 grammes

[ta0]

Thanks a lot Cyril for the very detailed photos.
I didn't recall that it whistled very loud. I have to try it again! 

So this top is pretty heavy, what contradicts some of what we said before. Therefore, I would guess the top does not "bounce" but just "walks".

Great information!

[Jeremy McCreary]

Many thanks for the photos and data, Cyril!

Reviewed both clips of your tables just now. Can't tell if those side-holes ever come into direct contact with your rails or bumpers during normal play, but if they do, they almost certainly add to the liveliness of the rebounds

In my experiments, it takes very little contact surface relief to transfer significant amounts of energy from spin to travel on impact. This kind of energy transfer is even more important to liveliness with a heavy top.

[Jeremy McCreary]

Therefore, I would guess the top does not "bounce" but just "walks".

Watching the clips of Cyril's tables in action at 1/4 speed shows the tops coming off the rails at high angles approaching 90° -- often even when the angle of incidence is low. In fact, this is quite common when the spin rates are high early on. Seems like the rebound angles would be lower (more tangent to the rails) if the tops were gaining travel speed just by rolling along the rails.

If contact relief isn't involved, we should probably take a closer look at the tip-table interaction triggered by transient tilt at the moment of impact. Those interactions were also crucial to liveliness in my experiments.

[Bert]

Well, thanks a lot all of you guys for sharing your thoughts.

I have been experimenting a bit myself. my conclusions:
-the tip should be just-not flat. The smaller the curvature of the tip, the more it seems to travel.
-I raised the front of the table a little bit, so that it slopes toward the back. The top tends to travel further, but still manages to bounce all the way back to the front.
-the part that bounces against the rail is the upper ridge, not the part with the hole in it (to make it whistle).

I recently bought a third table and this one had the original top with it. It looks like the part that bounces against the guide rails is just in between the upper ridge and the middle part with the hole.

This one is much more bouncy, but the weight is almost half of the one I had made.

[lastcenturygames]

Hello to all, I'm new in this forum, i have two "toupie hollandaise" in my house :  one big (like a billard) and a little another one (Tantet & Manon).
I have a spinning top for toupie hollandaise (see picture below) , the caracteristic is :
- height : 6,5 cm
- Diameter : 4,5 cm
- weight : 85g

If you know a specialist, he can perhaps make the same ?

In my website you'll see another spinning top table.
Have a good week end

[ta0]

Welcome to the board, lastcenturygames from France!

You forgot to post a link to your site: lastcenturygames.free.fr
You have a wonderful collection of antique games there!    The Toupie Hollandaise tables are magnifique!

I hope you can come to the Marines Festival.

[Bert]

Hi
Thanks everybody for the help and advice.
In the mean time, I have been able to buy yet another toupie hollandaise with an original spinning top with it. I am looking for an artinsan who could reproduce the top.
I also bought a couple of English toptafels/skittle tables. The tops are quite different. They are wooden tops with a very high and narrow tip and a top that looks like a disc.

I will upload pictures later.