Vintage "Perpetual" Flip Calendar

by otvinta3d, published

Vintage "Perpetual" Flip Calendar by otvinta3d Sep 22, 2016
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31154Views 4143Downloads Found in Mechanical Toys



Inspired by vintage flip calendars of the 60's, this desktop calendar will show you the current date and month. Flip it, and it will show you the next date. You will hear a gentle thud as a number card falls into the lower chamber to make room for the next card.

This calendar requires no batteries, the force of gravity does all the work. See the video!

UPDATE: We now have the month rings in Spanish, Italian and Russian. Please visit http://www.otvinta.com/download04.html to download them.

Print Settings

Printer Brand:









While Simplify3D offers to create support for the number cards, they seem to print fine without support, so we recommend switching off support generation when slicing the number squares.

The only piece that may benefit from a raft is the pinion -- for better meshing with inner teeth of the month ring.


The 17 number cards are 3 mm thick but in reality they come off the printer slightly thicker due to printing artifacts. Therefore you need to give each side of each number card a gentle but thorough scraping (we used a scissor blade for that.) If you have a digital caliper, make sure the thickness of the entire stack of cards does not exceed 51 mm (17x3) by more than 1 mm.

Hardware required: 4 metric countersunk Phillips head screws M3x12, and 4 metric nuts M3.

Assembly instructions:

  1. Place the number cards into the two chambers of box. The correct sequence and orientation of the cards is shown on the image.
  2. Slide box cover into the box's grooves.
  3. Mount month ring onto bottom, secure with washer.
  4. Insert pinion into the hole in base from the inside. Screw knob onto the pinion's threads tightly.
  5. Attach leg to base with two screws and nuts. Insert the leg's round peg into the box's side hole. The window in the box's cover with the number card 01 showing must face forward, away from the knob.
  6. Insert the other leg into the box and attach the leg to the base with two screws and nuts.
  7. Mount base onto bottom.

How I Designed This

The design is very straightforward except for the meshing internal and external gears used in the month display ring. The Planetary Gear tutorial we have created explains, among other things, how to design an external/internal gear pair in Blender 3D. For this calendar we used the following settings:

External Gear: z = 15, x = 0.5
Internal Gear: z = 60, x = 0

This video explains how to design internal/external gears, such as those used in the calendar's month display ring, in Blender 3D.

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Great design, but mine is running backwards! I've put the cards in as per the last image, but it is counting down from 31 to 1 rather than counting up!

You may be looking at the calendar from the wrong side then. The window through which the numbers are showing should be at the bottom, not at the top.

Yes, numbers at the bottom and rotating the same as shown in the video! I've opened it back up and checked the layout of the cards too.
I must have done something wrong, I'll check it again!

I’m assuming the calendar is not “smart” enough to know which months have 31 days, 30 days, and 28 days, right?

That's correct.

The model for the calendar base (cal_base.stl) was uploaded upside down. We just fixed it.

That really ingenues. I like it :)
Given your passion for mechanisms i'm supersized u haven't done your own automated remix version with gears and stuff. Although I guess you'ed have to employ a micro-controller to deal with time keeping to reducing the mechanical complexity and power consumption.

Did u come up with the day counting mechanism or was it already a thing?

Back in the 60s and 70s they made those out of metal. Do a Google image search on "metal perpetual flip calendar" to see some pictures.

ah yeah i guess i have seen them around but never really payed them any attention. I used to have one of those flip clocks but that's a slightly different mechanism. There's just something very pleasing about the simplicity of the flip calendar.

I love this! Once I print it, I will post a picture of it. Thank you!

What a fantastic thing.
Thanks very much I've made it as a gift for Valentine's Day.
What a romantic I am. :)

Glad you liked it. If you can, please post a photo of your make here.

I love this toy... Is there some easy way to have the months name in Italian, like GEN FEB MAR APR MAG GIU LUG AGO SET OTT NOV DIC ?
My wife doesn't speak English and gets confused (we're both 70...); I'm struggling to make changes by myself, but with Tinkercad it'd take weeks of work and headache!
P.S. The numbers are OK in Italian too... 8-))

Although it may be a bit late, but I did create an Italian version of the month ring, and also a Spanish and Russian ones. You can download them from http://www.otvinta.com/download04.html.

Thanks a lot! It's a Xmas gift for me...

Please post the photo of your make if you can.

Please email us at [email protected] DOT com (remove the dashes) to discuss.

Did you print the cards on edge or did you lay them down flat on the print bed?

You have to print them vertically (on edge) since they are double-sided.

i think the box needs a little modification. I have just printed it and there is no enough room for all the numbers.. i had to left two cards outside so the box could work... maybe i can fix that by modifiy the height on cura.... adding 3mm more

No, everything should work the way it is, but you do need to give each side of each number card a good scraping. We used a scissor blade for that.

If you have a digital caliper, measure the whole stack. 17 x 3 = 51, but right off the printer, the stack will probably measure 2 or 3 mm thicker. You need to bring this difference down to 1 mm or less. It may take a good 15 to 20 minutes of scraping.

Or in my case, 4mm thicker.. yikes.

definetely wont be fixed by modify height... holes for legs will be affected as well as the hole for the card.... maybe you need to fix the file

I started printing this and noticed that the pictures and description calls for M2 screw and nuts, the STL for the leg doesn't have any mounting holes. Did the design change to use self-tapping screws?

Apologies, and thanks for pointing it out. The fixed leg has just been uploaded. Thanks again.