From a spin-time perspective, this beauty does almost everything right:
Thank you, Jeremy ! By "almost everything" you mean that there is something you think it could be made better... ?
New ideas are always welcome.
I said "almost" only because I'm still sorting out the relationship between spin time and absolute size -- say, as scaled by maximum radius
R. It's possible that a copy of Nr. 30 with a smaller or larger
R might stay up longer.
As you know, small decreases in critical speed can yield large gains in spin time. It's easy to show that for a symmetric top of uniform density, critical speed is proportional to 1 / sqrt(
R) over a wide range of common top shapes. Beyond that, only the top's proportions count.
All other things being equal, that result favors tops of greater absolute size. Absolute mass, on the other hand, has no effect on critical speed.
But air resistance, another powerful limit on spin time, may well favor smaller tops. Many tops have disk-like rotors. Consider, then, the swirling air flow induced by a thin smooth spinning disk of radius
R.
The resulting aerodynamic braking torque generated by the disk face grows with
R4. Empirically, the braking torque from the disk's edge seems to be negligible up to thicknesses approaching
R/10.
Where the sweet spot in
R might be for a given top design is ultimately an empirical question. But my experience with tops of many shapes and sizes makes me think that a smaller copy of Nr. 30
might stay up longer.
