This latest
ortwin-inspired iteration is squarely in skimpy
suspension top territory: Just the stainless ring, some low-mass, low-stretch kite string, and 4 g of LEGO parts (including the white elastics) for a total mass of 64 g.
The
330 s spin time by hand is up 127% from last time (Reply #100). Still nowhere near the 700 s ortwin got with his Brass Band top (Reply #90), but much closer to my hope for a LEGO-enabled top deriving most of its AMI from a low-drag metal ring.
Unchanged since last time: Ground clearances under the ring and elastics, a very tight 4° scrape angle, and a CM height of ~10 mm. Though much thinner than I usually use for high-AMI tops, had to resort to the 3.2 mm stem to maintain CM height. (It's a LEGO thing.)
After 2+ hours and several rounds of rigging and balancing, was ready to give up on getting wobble down to an acceptable level. Then it just happened. No idea how.
Under blacklight, the white kite string fluoresces nicely in blue. The bright RBG markers around the stem were for a variant of the paintbrush balancing method. No help balancing this top, turned out, but I like the way they mix to white at speed.
Conclusions: The HUGE gain in spin time since Reply #100
must be largely aerodynamic, as critical speed and tip resistance changed little.
Intuitively, I think that if the spokes are a few thin needles, their drag will be negligible. Still, the optimal radius of the wheel and it's shape are things that have to be determined.
Lookin' pretty good here,
ta0! The data accumulated in this thread clearly shows that a
suspension top with a large AMI and very thin lines can make a decent endurance top.
This top's a definitly keeper. The long spin time takes some of the sting out of the annoying scrape angle, and I like the way it looks -- especially under blacklight. But if it were ever to lose its balance, not sure I'd put in the work to get it back.