Educational Clock

An educational clock meant to be a helping aid for learning how to read an analog clock.
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updated October 4, 2023

Description

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Background

I wanted to make my own simple variant of an educational clock that my kindergarten teacher had when I was little. I clearly remember it being very fun to just play with, seeing the planetary gear mechanism move the hands. It made it easier to understand the relation between the hour hand and the minute hand, and the fact that it was a physical clock that you were allowed to touch was also such a satisfying feeling. Every other clock in the room was off limits for kids.

It is made primarily for educational purposes, but it's also a fun toy.

 

Recommended settings

  • Material: PLA
  • Nozzle: Ø0.4 mm
  • Layer height: 0.2 mm
  • Infill: 15% minimum
  • Perimeters: 2 minimum

Print area: 205x200 mm original size. It should scale down well to a Prusa Mini size, but I haven't tried (at some point a smaller nozzle is needed).

Total weight: 108 g (∓ some amount depending on infill density)

No supports or glue is needed!

Materials such as PETG or ABS with more warping can be a challenge for the clock hands. Tolerances can also be a bit tight with those materials.

Note the print orientation on each part's description!

The Minute Hand is particularly thin and may require a brim to be used.

For aesthetic purposes I recommend printing the Clock Stand using 0 top and bottom layers to reveal the infill pattern. Just keep in mind that a too low infill percent can make the “feet” parts on the Clock Stand Base become hard to print properly! I used Honeycomb 15%.

 

Assembly instructions

  1. Place the Center Pin in the center hole of the Clock Face.

     
  2. Orient the flat surface so it faces the “12” mark.

     
  3. Assemble the Hour Hand and the Planetary Gear. Make sure that they can rotate (a slight resistance is OK).

     
  4. Place the Planetary Gear with the Hour Hand on the Clock Face. Engage the gears between the Planetary Gear and the Ring Gear.

     
  5. Orient the Hour Hand at the “12” mark. Note that there should be 2 teeth symmetrical to the center line with the Center Pin.

     
  6. Place the Sun Gear on the Center Pin, the gear end facing the Clock Face.

     
  7. Make sure that the Sun Gear is properly oriented towards the “12” mark. Engage the teeth between the Sun Gear and the Planetary Gear.

     
  8.  Top surface of the Sun Gear should be flush with the Center Pin top surface.

     
  9. Assemble the Minute Hand in the Sun Gear from the “12” mark side.

     
  10. Snap together the Clock Stand Base with the Clock Stand Support.

     
  11. Place the Educational Clock on the Clock Stand.
     

 

Fun fact

The total ratio between the gears is 1:11. Yes, you read that right; it's not 1:12 because of the planetary gear setup.

The small (sun) gear have 9 teeth and the planetary gear 45 teeth. That's a gear ratio of 1:5.

The ring gear have 99 teeth. The relation between that and the planetary gear is 99/45 = 2.2

Now multiply 1:5 with 2.2 you get 1:11.

So why? It's because we get one extra revolution from the planetary gear itself that is moving inside the stationary ring gear.

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Model origin

The author marked this model as their own original creation.

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