Another Interesting Possibility

Two weekends ago, I did a small update on things going on in my shop, both Saturday and Sunday (with more pictures).  The two general directions are either a more complicated and functional internal combustion engine vs. something more beautiful but still functional, like an orrery.  

Much of the intervening two weeks have been spent doing grown-up or homeowner shit, as we're speeding into summer and there are things that need the attention.  The exception has been something I stumbled across while doing something else.  It's called the Antikythera mechanism.

I'd heard of the Antikythera mechanism before, but hadn't thought about it in longer than I can recall.  It turns out to be rather interesting for a few reasons.  It's an ancient Greek device recovered in 1901 from a shipwreck in the Greek Islands dated to approximately 100 BCE give or take 30 years.  The most succinct description of it might be that it's the world's oldest analog computer.  The "world's oldest" by a thousand years.  If you'd like to be more specific, the kind of analog computer that best describes it is that it's an orrery.  

To borrow from the online Encyclopedia Britannica:

The Antikythera mechanism had the first known set of scientific dials or scales, and its importance was recognized when radiographic images showed that the remaining fragments contained 30 gear wheels. No other geared mechanism of such complexity is known from the ancient world or indeed until medieval cathedral clocks were built a millennium later.

The Antikythera mechanism was fabricated out of bronze sheet, and originally it would have been in a case about the size of a shoebox. The doors of the case and the faces of the mechanism are covered with Greek inscriptions, enough of which survive to indicate clearly much of the device’s astronomical, or calendrical, purpose. It is believed that a hand-turned shaft (now lost) was connected by a crown gear to the main gear wheel, which drove the further gear trains, with each revolution of the main gear wheel corresponding to one solar year. On the front of the mechanism is a large dial with pointers for showing the position of the Sun and the Moon in the zodiac and a half-silvered ball for displaying lunar phases. The drive train for the lunar position is extremely sophisticated, involving epicyclic gearing and a slot-and-pin mechanism to mimic subtle variations (known as the “first anomaly”) in the Moon’s motion across the sky. (See Hipparchus and Ptolemaic system.)

With something as famous as this, you might expect to find many pictures of reconstructions of it in everything from wood, to plastics (including in Legos) to intricate metal versions of it.  Some of those make the effort to recreate the final form and function of the Antikythera mechanism while others just emulate the functions.  This is a deep, deep rabbit hole to dive into.  

An example.  You can be sure the 100 BC Greeks didn't have plexiglass (or whatever that clear plastic is), but it's an impressive model.

Image Credit: Eternal Gadgetry  

There's this metal model on Instructables (design sharing), a 3D Printed model at Printables (Prusa), and another 3D printable on Thingiverse.  

And this illustrates only the gearing:

Image credit:  Communications of the ACM - figure 14 here.  Not that I could sit down with this and figure out what it should look like.  Besides, it shows you there are 65 gears but nothing about their sizes and numbers of teeth.  

Is this the next project?  I honestly don't know.  I like it, but 65 gears of unknown sizes strikes me as a lot for a first project cutting gears.  What's cool about this is the historical aspect.  That first orrery video I posted Saturday the 12th still seems pretty good (that links to the full video, not just the last few seconds).  I need to start looking closer at options.  Once I get my sprinkler system fixed.  And the other stuff.