Interactive Totoro piece for Giant Robot Show

This year Giant Robot had their 4th annual Totoro Show and I was lucky enough to be invited. I wanted to make an interactive kinetic piece for a while and this was a good opportunity. If you want to see an in depth video about the process check out my talk with Donald Bell from Maker Project Lab on youTube. He was very kind to have me on the show and we had a wonderful conversation that went over many details of this piece and the small automata I made last year for makevember.

The piece is 8.5 in wide, 6.75 in tall and 2.25 in deep. Mostly constructed with laser cut 1/8″ birch plywood with some small parts cut out from 1/16″ birch plywood. It uses a single 30 rpm gear motor powered by an 18650 lithium ion battery housed in a case that includes a USB plug and charging circuit. Most of the axles where parts pivot are made with sewing pins and the wire for the mechanism is very similar to piano wire except I extracted from the bead of bicycle tires. It’s stiff wire with a thickness of about 0.9mm. The switch is wired to provide power to the motor whenever it’s actuated. The characters are hand-painted with acrylic paint.

I really liked the scene where the Totoros and the girls are making the acorns grow at night. I didn’t include the humans in the final moving piece for sake of simplicity.

First hand-cut prototype with paper pinned on foam core
Working out the mechanism

I usually start this kind of project with some sketches and paper prototypes. First hand-cut, and then laser cut when I have some ideas on how to make it work. These pieces are pinned to foam core to work out the movement.

Making the mount for the tiny 30 rpm gear motor
Assembly after laser cutting the pieces

Here is the initial assembly after cutting most of the parts, the orange stuff is masking tape .

Rear view of the mechanism
Close up of the crank followers and guides

I didn’t have a solid mechanical plan from the beginning. I started with the box and an idea and went from there. A lot of parts like the wire wide were added as the need arose, in this case the wire was drifting back and forth on the crank so I had to add a guide to keep it vertical. The sliders are lubricated with graphite powder which explains the grey stain.

I simplified the arm motion compared to the initial prototype
Side view, little Totoro has no arms

I wrapped the switch cord in black para-cord to give it a less plasticky feel.

Acorn switch assembly
Acorn Switch

It was important to me that the switch would be pleasant to the touch so I put some effort into making the acorn case and figuring out a good “clicky” feel.

Finished back view
Charging port hatch – slides to reveal a microUSB port for charging the 18650 battery
Packed for Delivery
Final Piece