ball bearings Definition and 2 Threads

Hello fellow members! First and foremost I'll start by saying I couldn't be farther from a Physics connoisseur, I barely remember high school Physics/Maths. I love to know about mechanical systems and I'm an avid DIYer though. I'm trying to design a floating center cap system for my car's...

I made a waters turbine CAD design and make prototype with a 3D printer. I first tested the turbine by putting it at the tip of a ball point pen. At the tip of the ball point pen, the turbine rotates well. I made a video but there is no option by which I can upload the video. Later I attached a...