Invented & drawn by Bob Knetzger

TOY INVENTOR’S NOTEBOOK

Gnome Math Required!

A few years ago, I had to come up with a batch of gifts to give to friends and family — fast! Our backyard garden gnome was the inspiration: I’d make felt gnome hats for everyone. All I needed to make the pattern was a little math and a piece of string.

I knew the basic shape was a cone that could be “rolled” from a circular piece of felt — but what should its dimensions be?

I made a quick orthographic sketch with an auxiliary view to find out. I envisioned a cone, not too squat or too pointy, about 10½” high. In the frontal view (Figure A) this vertical dimension is not really the radius (it’s foreshortened), but the edge of the cone does represent the radius. So by ...

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