[OpenSCAD] Mayan calendar

Parkinbot rudolf at parkinbot.com
Wed Jan 3 11:40:16 EST 2018

If you arrange it like this
you'll have two rings and a sun and can use coaxial planetary gearing (PG)
with fixed planetary carriers (giving good stability and providing all
bearing points,necessary). From gold(13) to blue(20) you need i=20, which
you get by a two stage PG system with i1 = 5, i2 = 4. It will be hidden
behind the sun. From blue to red, you need i = 365/260, which you get by
coaxially adding an outer single stage PG system that connects a sun gear
with 260 theeth to the blue ring and a ring gear with 365 teeth to the red

If you use properly designed herringbone gears they'll stay well meshed
after assembly, without further means. For assembly the elastic properties
of the rings will be you friend. Don't worry about clearance, if you don't
have to save energy. With this ratios and speeds clearance can be 0. 

It is not difficult to use a lego-or puzzle-like connection system to
compose the rings/ring gears from different parts. They can be adjusted for
final glue when operating the system itself, of course starting from inside.  

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