Perhaps you would like to be more specific as to what "light" and "effective" mean. Also you might want to think about cost and size. People on this forum tend to be extremely helpful, but few are successful mind readers.
Patricia Lougheed
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Is weight really the issue? Don't you really want lots of inertia so that there's lots of stored energy to be dissipated by at the bearing point from friction? So, for a given weight on the bearing point and a given rotation rate, putting all the weight as far as possible from the centerline maximizes the stored energy.
I think he can't give us any more details or show us a sketch because he is trying to recreate the top from "Inception." If we all knew exactly what it looked and felt like, it would defeat the purpose.
I'd focus on an extremely sharp point, and highest inertia (will allow you to impart more energy with the initial spin) with low mass and reasonable geometry. If it's too large diameter and disc shaped, a strong and even spin (no wobbles) will be hard to achieve.
As negligible as it may be, wind resistance may also be a factor in determining the shape (large thin disc is not ideal) and this will limit the high inertia / low mass concept from becoming too prevalent.
Or you could just cheat and do something with a magnetic base.
My suggestions for single material top would be things like Tungsten or Gold (though probably a bit soft for the tip aspect) with a hollow center. Lead or DU are tempting except for the environmental/health & safety type implications.
However, a more complex multi component/material approach may have performance and even cost advantages.
Of course, given your other post about the top obeying commands I assume it needs a void in it somewhere for the actuators/demons/mexican jumping bean or whatever it is that is going to make it jump.
So, a nice carbon fiber body with a diamond or saphire or similar hard tip and then a 'ring' of tungsten or similar around the OD. If it must be alloy then substitute something nice like magnesium, titanium or (more boringly) aluminum & their alloys.
However given you've given a ridiculously vague requirement any answers we give are likely to have little merit.
What exactly does material composition have to do with the moment of gyration? I can have a simple rim with a few spokes to the hub and still answer the problem.
Look at gyroscopes and do the research on the mathematics.
Heavier (denser) materials will have a higher ballistic coefficient, friction due to air drag will not slow them as quickly as for a lighter material, for the same shape.
I think you need a hypoloidal-axiometrically gyro-optimized shape of revolution, because they produce uplift in a direction opposite their direction of spinning motion or any change in rotary acceleration. And, once you get it tuned properly so that the RPM/mass and diametral/inertial dynamousity match, the darn thing essentially floats, in effect a perpetual motion device, and you can use any language, very softly spoken, to direct it. But, once it gets going you have to be really careful when you are around it, because if you ever even whisper get screwed, you better run like hell. You know the expression CYA.
They are too busy looking up and studying all the good ideas we’ve given them. From our good advice, they know that once they get this thing worked out and patented, they will be on easy street. They just don’t have time for us any longer, they have all the info they need, and they are just to busy. And, I’ll bet when they get rich, they won’t give us a nickle for all our good advice.
BTrueBlood, correct the weight distribution is important, but not what it is made of. I can put a lot od light weight stuff on the rim of my wheel for example, or an equivalent amount of less heavy stuff. What that stuff is is not important. Material composition would prop ably weigh into the build (machining) or economics of the assembly. But yes, there is a practical advantage to using denser materials.
