This film does an admirable job of clearly explaining what can be a rather confusing mechanical concept -- the differential gear. It's Tuesday, and you owe it to yourself to learn a little something. If you already know how a differential gear works, I'm sure you'll also enjoy the charming retro qualities of this film!
True, we normally hear differentials in cars, but they've had other some intriguing uses in the past. Take for example the amazing South-pointing chariots created in ancient China. A carved wooden figure standing in a horse-drawn chariot would point South no matter which way the cart turned or how often. This was done with a differential.
Here is where you can get a wooden South-pointing chariot kit!