Perpetual calendar mechanical meter

I wanted to develop a mechanical calendar solution that I initially imagined to be made up of a multitude of gears before finally being inspired by a mechanical counter mechanism such as the one used by hostesses to recount the number of passengers.

After many prototypes and some complete design reversals, here is a functional mechanical calendar solution that can be realized with your 3D printer. The date is incremented by simply pressing the "One More Day" pedal. The month is incremented either on the 30th or the 31st depending on the length of the month. A small drawback of this mechanism is that it does not handle the special case of the month of February. So you'll have to press the pedal 3 times to go from February 28th to March 1st (or twice on February 29th if the year is leap year!).

The mechanism consists of 15 parts made in 3D printing to which you will have to add :

• 2 nails of diameter 3.1 mm x length 70 mm

• 2 nails of diameter 3.1 mm x length 70 mm cut to 35 mm

• 2 elastic bracelets (desk elastic type for backrest)

• 2 wood / chipboard screws diameter 2.5 mm x length 16 mm

For the assembly of this calendar, please also consider :

• Sandpaper

• Oil (e.g. bicycle chain oil)

• A 3.5 mm diameter drill bit to take up the bores, especially of the selector and the hooks guided by the nails

The proper functioning of the calendar depends on the sliding of the selectors and cams, so the surfaces in contact will have to be sanded before being lubricated in order to reduce the roughness induced by 3D printing.

You can also customize the housing and pedal of this meter from the following files :

https://cults3d.com/en/3d-model/gadget/pedale-et-boitier-personnalisable-pour-compteur-calendrier-mecanique

Here is a link to a first video that will give you first information on the assembly procedure.

https://youtu.be/ERKXG97c4Sg

I offer this model at a reduced price for the first daredevils who venture to make it.

I have only had the opportunity to print this model on my Alfawise U20, as the relative size of the parts determines how well the mechanism works. It is likely that the length of one of the selectors needs to be adjusted. If you notice a malfunction, please let me know in a commentary so that I can suggest a variant of the appropriate selector switch. I have already added a shortcut selector in the updated file.

Design update V125 :

• Addition of an assembly manual

• Increase the angle of the arms by 2° to make sure that the hook falls back into the next notch.

• Adding a shortened version of the month and/or day selector by 0.5 mm

Here are the parameters I used for information:

• Material: PLA

• Thickness per 0.15 mm layer

• Wall thickness of 1.2 mm

• 10% Filling

• Printing with support

The internal support and the tens wheel include functions such as leaf spring, be sure to orient these parts when printing so that the springs are in the XY plane of your printer to have a better rigidity. So the internal support (MainBody_V99.stl) should be printed on its right side even if it will require more support when printing.

I don't have experience in 3D resin printing (SLA) and I don't know if this technology is suitable for MainBody_V99 and TenWheel_V99 parts because of the presence of these spring functions.