Perpetual calendar with mechanically automatic day of the week

thingiverse

- This calendar automatically keeps the day of the week correct for a year, from March 1st to the end of February in the next year. Contrary to the incremental mechanism of perpetual calendar in fancy mechanical watch, any drum can be rotated arbitrarily to any direction (CW and CCW), endlessly. It is useful to check the day of the week on a particular date. - This calendar consists of three planetary gear sets to keep the relationships among four drums. - You need 3D printed parts only to make the calendar except paint. All parts can be printed out without supports. - You can scale this calendar up or down. Original size is a bit bulky. It is possible to downscale to 60% with well tuned FDM printers. With SLA printer, 14mm gear version can be scaled down to tiny 40%. Of course, larger is easier to make. Update info (see descriptions at the end of this page) - Nov 02, 2020 : Raised letter version is added. It is easy to paint. - Nov 05, 2020 : Thicker gear version (14mm-gear) is added. It has extremely loose gears and only for very small version (40% or around) with SLA printers, not for normal FDM printers. - Nov. 27, 2020 : Blank drums are added for 10mm version. You can stick printed paper on the drums. - Dec 02, 2020 : Kanji version (narrow width) is added. Shorten main-axis and foot are also supplied. The one shown in the picture above is 60% scale. - Dec 03, 2020 : For the users of precise 3D printers, tight clearance version is added. It might cause fusion of neighboring parts or unsmooth rotation if the printer does not have sufficient preciseness. Axis of each planetary gear is changed to be thicker than the old design.