I got an email from a high school engineering student who was looking for advice on ow to make his catapult the absolute best it could be.

I responded to him with a few ideas. And one of the ideas was to put a ball bearing in the axle. This would significantly reduce the friction and improve the performance of the catapult.

I was creating web page with three ideas for making catapult improvements and of course one of the things was to add a ball bearing. And this tweaked at me. I remember seeing somewhere drawings that Leonardo Da Vinci had made of the ball bearing concept.

And I remembered seeing some ball bearing machines at the Da Vinci Museum in Florence Italy. ( I visited that museum. You can see pictures here)

This picture here is one of the ball bearing machines at the Da Vinci museum.

Well, he didn't invent the ball bearing. There are recorded instances that pre-date him. But he did have a hand in the development of the ball bearing. He was evidently fascinated by the concept. For him it was all about the study of minimizing friction. And that's what a ball bearing does so well.

Ball bearings are an incredibly important thing in our world. They are in just about every thing that has moving parts! So, Da Vinci's passion for the ball bearing is still being felt today.