Saturdays are time to take a break from databases and look at other things that amuse me.
This week: non-circular gears.
This guy supposedly hand-makes these things out of paper:
There's a great series of videos on old Navy analog computers, which are basically complex gear systems: part 1, 2, 3, 4, 5, 6, 7.
This is probably the best explanation I've ever seen of how differential gears work:
And of course, no discussion of differentials would be complete without mention of the South-pointing Chariot, rumored to have been invented by the Chinese over 4500 years ago. South-facing chariots use a series of gears to keep a figure pointing south no matter which way the wagon turns. These days geeks can't resist building their own out of legos or whatnot, and in looking for links I came across a kit you can buy for $59 and I think I might just have to.
Lastly, here's some random gear-related links:
The Kentucky Do-Nothing Machine
The German Do-Nothing Machine
The Eames (yes, that Eames) Do-Nothing Machine
A wooden orrery!