[OpenSCAD] Mayan calendar

Ronaldo Persiano rcmpersiano at gmail.com
Fri Jan 12 17:12:17 EST 2018

My knowledge of mechanisms is very basic. But, yes, the purpose of Geneva
drive is to produce an intermittent motion from a continuous rotating
motion drive. It is an indexing system that may have its place in your

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. :)

However, I guess the best solution to assign month names to the 365 day
Mayan calendar is found in the Youtube video Mark Peeters referenced here
days ago. In the video, there are three geared wheels: one with 13 numbers,
one with 20 day glyph names and, the year wheel, with 365 days. The year
wheel have 365 combinations of a month day number and a month glyph. There
are 19 month glyphs, one of them appearing just 5 times on the wheel and
the others appearing 20 times. So the months are not in a separate wheel
but in the 365 day year wheel. If you stop the video at 1:38 you will see
the 5 day month in detail.

Each specific combination of one number (first weel), a day glyph (second
weel) and a pair [day number, month glyph] are aligned just once in 18980
days. This is the Calendar Round of 52 years.

2018-01-12 16:23 GMT-02:00 Dan Shriver <tabbydan at gmail.com>:

> I looked up the Geneva drive and see that it would solve an unstated
> problem of mine.  If I used a Geneva drive with one pin and the cross on
> the underside of the "day of the month" wheel, it would change a
> continuously turning motion into discrete movement of the day wheel.
> I believe you have an idea for how to reset the day but I do not
> understand it.  Can you provide a diagram of how it works?
> Maybe if I have a second cross at the top of the solar month day and there
> is pin (not sure if it would need to be on a spring or not) on the "month
> of the year" wheel that causes the "day of the month" wheel to spin back
> from 5 to 1.  The only problem with that is I would have to somehow
> disengage the Geneva drive on the bottom...  I'm sure that's not what you
> are suggesting (since you mentioned "19 pin irregular").  I'm just having
> trouble imaging what you are saying.
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> On Thu, Jan 11, 2018 at 6:38 PM, Ronaldo Persiano <rcmpersiano at gmail.com>
> wrote:
>> A Geneva drive with irregular 19 pin arrangement?
>> 2018-01-11 20:57 GMT-02:00 Dan Shriver <tabbydan at gmail.com>:
>>> Are there any clever tricks I could use to reset the day of the month
>>> wheel after "Dec 5" so it reads "Jan 1" the next day?
>>> [image: Inline image 1]
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