Sunday, December 18, 2011

The Differential

When I was about six years old, I remember playing with my Matchbox toys and noticing that, on a curve, the outside wheels had to spin faster than the inside wheels.  Matchbox toys at the time were connected by a simple axle, and the little bit of skidding had no impact on those smooth, plastic wheels.

I asked my Dad how it worked on real cars.  My Dad, a lawyer, had no idea, and just responded, "It's very complicated machinery in there."  (Well, to be honest, he could very well have been tired with my questioning and did not want to get into the inner workings of a the gears.)

The complicated machinery is now known as a differential, and I've always thought it was a little piece of magic.  (The other impressive piece of magic is the now old-style planetary gear system used on automatic transmissions, but that's for another day.)  So, I present to you, for your enjoyment, a 1937 movie about differentials and how they work.  It's very impressive and very instructive. (Skip ahead to the 3:30 mark to jump over the repetitive, long introduction material.)

I only wish I had YouTube when I was six.

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