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Alan24
18
Jul 26, 2018
The video is misleading. After it's twirled, it appears to speed up, but that's a stroboscopic effect of the video frame rate. It's the same effect that makes wagon wheels appear as if they are rotating backwards in movies and videos.
This perforated structure is somewhat of a two-edged sword. The perforations allow it to respond to blowing, but they also have more aero drag than a solid top, and thus a shorter spin time.
K.T.N
1264
Jul 30, 2018
Alan24This is a little off topic, but here’s an explanation of what’s going on with that “Wagon Wheel“ effect.
The illusion of slow, slowing, stopped, or reverse spinning due to coinciding frequency rates between the rotating spokes and the frame capture rate of a camera, or the strobe rate of a light, are well understood.
More interesting is when you see this in real life, where there is no frame capture rate or flickering or strobing light.
You can often, for example, see this effect in real life on car wheels when driving down the freeway. That’s in plain, continuous sunlight.
An explanation is provided here:
https://io9.gizmodo.com/why-do-wheels-sometimes-appear-to-spin-backwards-1593807400
Very cool top, by the way.