Quartz-movement Based Perpetual Calendar Clock

A clock with a perpetual calendar mechanism that correctly handles all types of months, including February in a leap year, has been developed. Despite the weak torque of a quartz clock movement, an improved mechanism has been designed to mechanically realize this complicated function.

Features

• The calendar advances automatically, so you do not need to adjust it until March 2100. In the morning at March 1st, 2100, this clock will show Feb. 29th. So please raise the main arm once and all set, if you will be still alive and remember it.
• It uses a commercial clock movement, so it can work for a long time without an external power supply.
• The calendar is easy to adjust by directly rotating the clock hands.
• The rear surface is flat, making it easy to hang on a wall beautifully.
• The skeleton design exposes the mechanism inside, making it easy to assemble.
• There are no visible screw heads on the front side.
• This clock is easy to print, as all parts can be printed without support structures.
• You can make this clock using popular 3D printers that can print objects up to 180mm x 180mm (use the square back plate and separate main arm).

Contrary to the former design with stepper motor, it uses not rubber bands but a weight and the gravity. Therefore, the calendar mechanism works only when the clock is upright on the wall.

• "High torque type" quartz clock movement commonly sold in online stores such as amazon.com. It comes with a long minute hand which is attached to the shaft using a cap nut. I used this one.
• An assortment of 2mm tapping screws. It is also sold in online stores. This clock uses relatively short tapping screws.
• A M8 nut made of steel or stainless.
• Double sided adhesive tape.

• disassemble the movement and shorten the thread using hacksaw. Ideal length of the thread is around 5mm, because the thread to mount the movement to the clock face is usually too long.
• Shave the shaft for the hour hand to form two flat sides. It is necessary to engage the gear to the shaft securely .
• Make sure that the clock movement properly works after reassemble.

• Print the parts with supplied posture. No support structure needed.
• If your printer can not print the circular-back-plate.stl (diameter = 250mm), use "square-back-plate.stl" instead. It is within 180 x 180mm.
• Remove blob and debris on gears carefully. It is very important to make the clock driven by very weak torque.
• Assemble the parts using 2mm tapping screws. Please take a look at the assembly guide video. The parts list below is listed in a same order to the video.

• Print the parts with supplied posture. No support structure needed.
• Remove blob and debris on gears carefully. It is very important to make the clock driven by very weak torque.
• Assemble the parts using 2mm tapping screws. Please take a look at the assembly guide video. The parts list below is listed in a same order to the video.
• When you attach the "week-driven-gear.stl" to the "week-hand.stl", align the notch towards the hand.
• "month-gear.stl" is 90degree rotation symmetric (12 teeth) and you do not need to care about the direction.

• Print the parts with supplied posture. No support structure needed.
• main-arm.stl has a print-in-place hinge. It works well when the arm is installed in the clock that restricts the degrees of freedom. However, it may separate each other when moving part is twisted. It can be re-assembled by the manner of easy puzzle.
• If you use small printers with the build table of 180x180mm, print the main arm separately using “main-arm1.stl” and “main-arm2.stl”, then assemble it by twisting motion. The separate models would be useful if they fuses each other with print-in-place method.
• Stick M8 nut to the weight space of the main arm.
• Place the program wheel on the base plate.
• Engage the front and back unit each other.
• Align the angle of the month hand. Set the program wheel to February (main arm is inserted to the deepest part), then rotate the month hand to the desired angle.
• Align the angle of the "week-drive-gear.stl" so that the week hand rotates at midnight.
• Fix two units using 2mm tapping screws. Please take a look at the assembly guide video.
• Confirm that the calendar advancement mechanism is working properly.

• Print the parts of minute and hour hands with supplied posture. No support structure needed.
• Attach the movement to the clock.
• Align the two hands of 12hours and 24hours when attaching the hour hand.
• Attach the minute hand using a cap nut comes with the clock movement.
• If the shaft of your clock movement is too short and the hands interfere each other, use "min-hand-for-shorter-shaft.stl" and/or "hour-hand-for-shorter-shaft.stl".

• Print the parts of dials with supplied posture. No support structure needed.
• Select the month dial from two candidates.
• To give different color to the letters and indices, use "pause at height" function of your slicer, and change the material during the pause. Change the material at height=1.5mm.
• Stick sub dials to the front frame with double sided adhesive tape.

Dials in non-English languages are at https://www.thingiverse.com/thing:5986655 ,versions for the other languages would be added on request. Alphabetical characters only.

Confirm that the clock is working properly.

How to adjust the calendar

• The calendar can be advanced a day by raising the main arm (at the weight)
• The date hand can be rotated manually to quickly set the date. From 31st to 1st, the main arm should be retracted from the program wheel. It can be rotated clockwise only.
• The month hand can be rotated manually. The main arm should be retracted by raising the weight. It can be rotated to the both direction.
• The week hand can be rotated manually also. At midnight, the drive gear is engaged to the driven gear, so avoid operating it at midnight.

The calendar is updated around 22:00. If you want to change the time to update to around 0:00, use "24h-hand-30deg.stl" that has 30 degrees (= 2 hours) twisted hand.

Troubleshooting

• If the date advancement is not working properly (for example, it advances 2 steps per day), tune the length of the "date-spring.stl" by slightly scale up or down of this parts with your slicer.