Hmmm. I wonder why neither team decided to lower the center of gravity below the contact point, since they would be spinning on the tiny raised cylinders? It seems it would be easy to make the outer ring hang below the point, so it would stay upright at 0 rpm. Does that somehow make it unstable when you spin it?
*quality craftsmanship and design

Boosting this quality contribution up in the Hot Listing - declared quality by newtboy.

Serious geek video. That was cool

Really great to see a TV show celebrating real skill. Both were excellent.

Oh man, I really want to buy those tops... and start them spinning on the skulls of the voice-over narrators, until the tops drill all the way down into their speech centers.

Good question. I think that the entire device is unstable no matter what, its impossible to keep it straight no matter where the point of gravity as long as it needs to balance on a single tip. So zero speed would mean tip over in all cases unless you make a more stable tip (square) which would mean it cant spin very well which means you havent made a spinning top.

You can find more about the physics of the spinning top here:
http://hyperphysics.phy-astr.gsu.edu/hbase/top.html
and here:
http://physics.stackexchange.com/questions/271/why-dont-spinning-tops-fall-over

So what is the optimal distance of the center of gravity to the tip?

There are several things working at the same time. Most importantly is the energy. You need to store as much energy as possible so that the top can spin for as long as possible. When the top slows spinning the friction at the tip becomes larger (the precession becomes bigger) so it starts to lose more energy and slows the spinning even more. You store energy by adding weight with a center of mass that is further away from the tip. When the top then "falls" the center of gravity moves down and reduces potential energy. Due to energy conservation kinetic energy goes up meaning speed of precession or of spinning goes up and creates a force pushing the top back up.

Off course, more mass means more friction at the tip, so there is for sure an optimal here, most likely depending on mass, size and shape of spinning top, etc.

Last but not least, more rotation speed I assume also means more friction, so its a trade-off.

If you move the center of mass down below the tip, well, if you move it as far off as you would above, the energy you can save is about the same, but the entire thing would be harder to build and you would need to make sure the sides fit around the ground plateau. Also, when the precessions become bigger the sides will hit the plateau, meaning game over.

In the end you are better of keeping the center of gravity above the tip point.

?
If it's balanced, with the center of gravity below the balance point, why would it become unstable at any rpm? The lower the CG, the more stable it would be...even when stationary.

What I'm describing would 'hang' from the contact point, like the difference between a gyroscope on the table and one hanging by a string, the one hanging would never 'fall over' because gravity works to keep it upright.

Built the same as they built them here, but with the outer ring much lower, there should be no contact until it wobbles, which in my mind it never should.

Yes, I didn't think it would spin more, or faster, just be more stable, because lowering the CG ALWAYS makes things more stable, no? My design should self right if it gets off balance, gravity should pull it back into balance, rather than off balance like a normal top.

I just wondered if, somehow, centrifugal force coupled with some other forces might make it try to flip over....or maybe if the CG isn't above the contact point, it's not a 'top'?

*dead But I cannot invoke that.

Invocations (dead) cannot be called by ForgedReality because ForgedReality is not privileged - sorry.

*dead

This video has been declared non-functional; embed code must be fixed within 2 days or it will be sent to the dead pool - declared dead by newtboy.

@newtboy I think you are right if the spinning top would hang, ie its tip would be inverted (pointing upward, stuck to the plateau in some manner). Any movement away from center for the CG would be pulled back by gravity. No spinning required. However that is not a spinning top but a pendulum. As long as the tip is on top of the ground (pointing down) and not hanging the spinning top will be unstable and the only way to balance the top is to spin it no matter where the CG is.

I think you still misunderstand. I don't mean it would hang from above, it would balance on it's contact point. In that way, it would 'hang', but the point of contact would be pointing down in contact with the top of the 2cm cylinder and the bulk of the mass in a ring hanging below that point. To exaggerate for clarity, think of a soda can with the top cut off, turned upside down, and balanced on a pin touching the exact center of the inner can 'bottom'...then spin it.
My idea is a top EXACTLY as they made it, except the weighted ring is much lower, so the CG is below the point. Then, when set on the pedestal, it would be stable when stationary (when set on a counter, the point would not touch). I can't see why that would change when spun as long as the CG stays below the point and balanced/centered.
It would balance when stationary, no question. My only question is what might happen when you spin it, would the rotation make the CG 'want' to be above the contact point for some reason, or would nothing happen. I don't have a lathe to make one myself to try, so I thought someone well versed in rotational physics might know.

@newtboy ah finally see what you mean. And yes you are right a Coke can would be stable and it could rotate. It is no longer considered a spinning top I think, so that is why the contestants didn't make it that way but for sure it would work.

If the can rotates I think the torque (force due to rotation) is in the same direction as gravity. (Where in the normal spinning top case gravity pulls the cg off center and torque back on.) In the can case both would move the cg back to equilibrium, Ie on center. there would be no precession at all. Every time some small Bump would make the cg move of the center axis it would be pulled back instantly.

I think it would work, and that it would take away the challenge ;-)

Awarding eric3579 with one Power Point for fixing this video's dead embed code.