Turning Archive 2004

Subject:
Spinning Top Mystery *LINK* *PIC*

Brad Vietje
>I make quite a few tops of various sorts. This question is about throwing tops, or peg tops -- the sort you wrap a string around and toss side-arm to spin...

I make a design like those sold by The Toycrafter (link below) and the mystery is that they seem to be difficult to scale down. Let me explain:

These tops are thrown with the string wrapped first around the top of the top, and then around the tip, though this not shown correctly in the photo below. (If you haven't used this sort of top, follow the FAQ on the Toycrafter web site where this is described and illustrated.) The top is released upside-down, that is, with the tip up, and the top inverts as it winds off the string. I've made a few dozen roughly 2" wide by 3" tall, and so long as the shape and weight distribution are correct, they invert and spin beautifully.

Now the mystery: when I make them a little smaller, say 1.6" by 2.4", and as close as possible to the exact same shape, they don't throw the same. If you wind them and throw them like their larger cousins, they land on their sides, and don't quite get up on the tip. By adjusting the release by 90 degrees, so the tip faces me instead of facing upward, they work perfectly.

So the question is, What's going on here ? I know there are many things that cannot be scaled up or down in a linear fashion, like a column, for example, since the strength is proportional to the cross sectional area (a linear dimension squared), while the mass is proportional to the volume (a linear dimension cubed), and similar phenomena. Not knowing much about how the top rights itself, I'm struggling to understand why a smaller top of the same shape will not do so.

Can someone explain this, or suggest a modification of the shape that will toss like a larger one ?

Safe Spinning,

Brad Vietje
Thetford, VT

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Spinning Top Mystery *LINK* *PIC*
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