[OpenSCAD] Mayan calendar

Ronaldo Persiano rcmpersiano at gmail.com
Sun Jan 14 17:11:51 EST 2018


Hi, Dan.

I have worked a bit on the idea of using sectional gears to solve your
quest about the month wheel in the Mayan Calendar Round. I designed two
sectional gears: one for the month wheel and one for the year wheel. The
first one has 76 teeth (one for each 5 days) with 7 missing teeth. The year
wheel has 73 teeth (one for each 5 days as well) with no missing teeth. The
missing teeth of the month gear allow that the wheel rotates 4 times faster
them usually during the short month transition. The included animated gif
shows the transition of 5 "unlucky days". Another pair of sectional gears
would be responsible for this transition (I haven't designed them). The
design of the two shown gears is not correct yet because of a small tooth
crash at the beginning and ending of the transition but some "light
filling" of two teeth of the month gear would solve that.

Animation: MonthTransition.gif
Animation code: mayanSGears.scad
Month gear: monthGear76_7.svg
Year gear: yearGear73.svg

In this design, the two wheels have approximately the same big diameter. I
don't see any way to avoid that.


2018-01-12 20:12 GMT-02:00 Ronaldo Persiano <rcmpersiano at gmail.com>:

> I tried to design my idea but failed: I don't think Geneva drive would do
> the trick. In fact, I think now a better solution for your quest would be
> to consider a variable sectional gear mechanism like the one is found in Gearwheels
> from Hell <http://www.douglas-self.com/MUSEUM/POWER/gear/gear.htm>. Those
> mechanisms allow to have two or more gear transmission ratio during the
> rotation. But don't ask how, at least not now. :)
>
>
>
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