Marble ball bearing

This ball bearing uses 6 marbles that are 16 mm in diameter. I got a bag of 50 marbles for a dollar at Toys R Us. This is in three pieces (two of the `cage` piece, and one `shaft` piece). I managed to put the thing together, including marbles.

I'm not a mechanical engineer, and the movement is a bit rough, and catches a little in places. If you drive it with a cordless drill, it rattles because things aren't all perfectly aligned. But it does rotate.

Here's a little video: https://www.youtube.com/watch?v=ie1mtN5CR90

After making the video, I took it apart and sanded the inside surfaces that touch the marbles, and the motion became a lot smoother. I used the cordless drill to help sand the surfaces on the axle.