A nice little bit of fun on Friday. You’ll see, pretty often, illustrations of gears for some sciencey or engineering-invoking illustration or logo, and they’ll be all shiny and pretty and stuff, right?

Problem is, those gears can’t turn. They’re wedged together. Play with it in your head, you’ll see one gear is forced to turn in two directions at the same time, and of course can’t.

So Numberphile – who has a youtube channel – decided to come up with some three-gear systems that actually work. They’re really cool. Enjoy: