[OpenSCAD] Mayan calendar

Chris Camacho chris at bedroomcoders.co.uk
Mon Jan 15 07:17:17 EST 2018


it might be worth your while to research the antikythera mechanism 
especially the fractional gears

I never knew you could half a gear tooth... with different ratios with 
fractions you should be able to reduce the need to have long sectional 
gears (hopefully)


On 14/01/18 22:11, Ronaldo Persiano wrote:
> 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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