Moon Rabbit Mechanical Toy

Video tutorial

Production/design motivation

The Mid-Autumn Festival is coming, so I’ve decided to make something festive. Recently, I met up with mechanical toy designers Kazuaki Harada and Rob Ives, so this time I tried to make something along those lines. At first, I designed two toys based on the moon rabbit and Wu Gang, but afterwards I decided to just stick to the moon rabbit toy.

Materials

  1. One 3mm fiberboard
  2. Superglue or wood glue
  3. Four M3 x 12–15 mm hex bolts
  4. Four M3 nuts or nylon nuts
  5. Design plan

Tools

1. Universal VLS6.60

2. Hex key

Procedure

Define the targets; check and design the mechanisms

First design your moving targets. I wanted the pestle to move up and down and the rabbit to sway a little, so I divided the parts into four categories: mortar, pestle, arms and body.

(Below is the initial draft.)

After designing the targets, I started going through existing products and mechanisms looking for similar bar or cam designs. Moving targets like these are quite simple, so I didn’t spend too much time on this step. I borrowed the pestle idea from Kazuaki Harada’s Laugh out Loud, and the moon rabbit from the common rocker mechanism. Once everything looked OK, I began making 3D graphics and simulating moving paths using the software.

(Below is Grinding Moon Rabbit V1 made in Fusion 360.)

2. Laser cutting

Once the computer simulation is done, it’s time to make the toy! I made all 25 parts using laser cutting. It may seem a lot of work, but it didn’t take long.

3. Assembly and attachment

As a quick test, I temporarily attached the parts with superglue. (For the end product, I suggest using wood glue instead: It’s stronger and has a nicer color than superglue.) I attached the shaft at the bottom, the bowl at the top and all other parts on the main shaft.

Once everything’s attached, it’s time to put in the nuts and bolts. My toy is bolted together at four different points, all fixed with ordinary nuts. If you want to display your product for a long time, I would suggest nylon nuts.

4. Finishing the test

During the first round of tests, the rabbit wouldn’t go back to its original position. The unbalanced torque of the mechanism should be enough to bring it back to its original position as it makes the rabbit spin counter-clockwise. However, the bottom shaft was encountering too much friction, which offset the torque and stopped the rabbit from resetting. So, I used sandpaper to sand down the bar under the rabbit, and now it works fine!

5. Improvements

  • My moon rabbit moves but in an awkward way. This is because I didn’t measure proportions when I was doing the graphics, which meant I ended up with a long movement but a short grinding action.
  • Wood looks nice, but some more colors would make it look even better.
  • The bolts could be replaced with plastic bolts or something smaller, to bring the final product closer to the original design.

Made @D-School, NTU   @New Taipei Makerspace and Tool Library

For more projects, please visit the author’s YouTube channel: https://www.youtube.com/c/不務正業

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