Technical LEGO: Spinning French parachutes

OK, spin isn't exactly what you want in a parachute. But LEGO recently introduced a large round parachute canopy. And I had 2 more canopies in orange to turn into — what else? — spinning tops! Plan A: Cover a suitable frame with a parachute canopy above and below to reduce air resistance. Result: A 288 mm, 190 g "paratoupie" finger top that stays up 45 s with very little wobble. ("Toupie" = French for spinning top.) Removing the upper canopy cuts spin time by 50%. But those blue tires generate some pretty trippy visuals at speed! Plan B: The "parapluie", a centrifugal umbrella top. ("Parapluie" = French for umbrella.) The parapluie's single orange canopy attaches to 6 independently folding "stays" hinged to a rigid "core" (stem+hub+tip assembly). The core defines the intended spin axis. At speed, centrifugal force and gravity try to open the canopy against an elastic band trying to close it. The 204-288 mm, 94 g parapluie plays in both umbrella and top modes. Initial unbalance causes whirl in need of damping during spin-up in umbrella mode, but the canopy eventually self-balances under centrifugal force. In top mode, best spin time = 5 s with too much wobble. And even with my practiced hand, it's hard to get the parapluie above critical speed without a starter. Why such a short spin time? Air resistance is severe. Divergent core and canopy rotations add internal frictional losses. And as the canopy closes, overall center of mass rises while critical speed grows to meet the rapidly decaying spin rate. Frankly, I'm surprised the parapluie stays up at all! But the top has redeeming qualities. One of the best is the oddly satisfying 1:1 relationship between canopy angle and angular speed set up by the band's elasticity. Maximum operating speed is just shy of a canopy angle of 90°. Go beyond that, and the canopy will invert when the top slows. Go to 6:34 to see the action at 1/8 speed (240 fps). Varying speed during spin-up helps the canopy open evenly, as it prods the band to even out its tension between stays. The band hooks have rollers to make it easier for the band to adjust itself as canopy angle changes. The canopy and core axes tend to diverge on release. If they ever realign, it's usually right before the top falls. The elastic band's stiffness has a big impact on operation and play value. Had to try many different bands to find one that works as well the default band shown first. The thicker, stiffer band at 8:54 makes the canopy less responsive to changes in speed and therefore harder to open. However, the stiffer band also makes it impossible to invert the canopy with the default starter. Conclusions The paratoupie is a large, smoothly spinning finger top with a decent spin time — in part because its upper and lower canopies effectively hide its high-drag frame from the surrounding air. Removing the upper canopy cuts spin time in half, but I really like the frame-related visual effects it reveals (see 1:02). The folding parapluie, in contrast, needs a starter, wobbles too much, and is lucky to stay up 5 s for reasons explained at 3:43. But it has decent play value all the same. Making the canopy open and close by varying the top's speed is oddly satisfying. The top's interesting to watch in action (slo-mo at 6:34). And the complex mechanics are fun to ponder. Then there's umbrella mode.3 This unusual novelty top also deserves a spot in my collection as well. Thanks to fellow top-fancier Jorge for the idea! See also... Centrifugal blacklight top @ https://youtu.be/tG-szSIt84A More centrifugal tops @ https://youtu.be/nTNyuuhw04s Hartnell steam governor @ https://youtu.be/FIEjP8qWA08 Centrifugal tachometer @ https://youtu.be/zOgJ3XkvCkg Expanding ring tops @ https://youtu.be/jEMUGFQTux0 Music: Quincas Moreira, Love or Lust