Mechanical Foamcore Models

I’ve been asked a lot about how to get started building mechanical contraptions and I always mention Keisuke Saka’s excellent book Karakuri, how to make mechanical paper models that move. The book has actual printed template pages that are meant to be torn out and used as building materials. The first time I encountered this book it was on loan from a friend that had built most of the models already, so I set out to replicate the basic mechanisms using materials that I was comfortable with, and that were quick and easy. Foam core, paper clips, skewers, paper, and plastic bits from yogurt containers.

I like this approach because paper craft can be intimidating for new makers as it requires patience an precision, and when it comes to working mechanical models it is sometimes easier to take a more forgiving approach.

These pieces are not new work. They were the precursors to the one month of small machines project so I wanted to document them even though they aren’t pretty. Page 6 of the books offers a summary of the basic mechanisms:

Most of the models are built on a foam core base that is roughly 2.75″ x 2.75″ by 2″. And for the completists out there, I didn’t build a Crank B.

Cam A – The rod makes a repetitious vertical motion
Cam B – Two rods make a vertical movement alternately.
Cam C – The rod makes a repetitious horizontal movement.
Cam D – The rod slides repeatedly in a linear motion.
Crank A – The rod sways repeatedly in a circular motion.
Crank C – The turning of the crank is converted into vertical motion.
Gear A – The gear turns horizontally to the handle.
Gear B – the gear turns perpendicularly to the handle.
Geneva Stop – A wheel makes turns in a discontinuous rhythm.

For making the gears I used I printed them on paper, glued on the foam core and then cut by hand. The Gear B needs some beveling to make it work.

This is a really good set of mechanisms to get started. Each mechanism will have a set of problems to solve, and solving these problems in whatever material you choose will translate to other materials. I like foam core and hot glue, but you might choose cardboard or wood. Good luck with your builds!

Also if you want an easy way to share these, grab them from my giphy channel here: Cam A, Cam B, Cam C, Cam D, Crank A, Crank C, Gear A, Gear B, Geneva Stop.

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

Warm Heart Automata

A little story about how not to steal like an artist first. Sometimes I seek inspiration in social media. One day I found this awesome illustration by Instagram user @you_just_illusion and decided to use it as the base for this drawing. I sincerely though I had made it different enough and imbued it with my own style but that’s not how he felt and he let me know in a polite direct message. I apologized and we agreed that a shout out to his work would be enough atonement.

I think sometimes there is a fine line between inspiration and copying and it seems like I crossed the line in this case. I wasn’t trying to be malicious but sometimes this happens. Originality is not very important to me. I subscribe to the “Everything is a remix” idea. And almost everything I do came out from somewhere else. Sometimes the influences get lost, mixed with the others. And sometimes you make the wrong judgement about how far you actually mixed something. In this case no one got seriously hurt and we had a good interaction. And I’m also satisfied with how this piece turned out.

The first version I drew was for a zine project I was working on, which you can see in the background here:


I’m on a quest to unite my visual output with my maker spirit. Making drawings that move seems like a great way to do that. I started by cutting the outlines out of 1/4 in plywood and attaching the flames to a couple of dowels.

My initial idea was a simple crank and some wavy motion but I wasn’t entirely sure about how the mechanism was going to work, so I made a prototype out of scrap wood and wire:

And here is what the final version looks like with the two cranks:

After I had the mechanism figured out I moved onto painting. I started with a few coats of white acrylic ink. I sanded that with 600 grit sandpaper to get a nice even surface and applied a coat of workable fixative. The fixative helps with bleeding. I applied the black ink with a brush and and quill for the fine details.

warm_heart_progressI like how you can still see the grain of the wood on the white areas.

Before the final assembly I coated the main surface of the box with superglue. It acts as a hard clean finish. The other parts were coated with a matte finish. The moving sections were lubricated with bee’s wax. I made the handle out of some ebony scavenged from the keys of and old piano a friend found in the street.

One final detail is the wall mount. This system with two matching pieces of wood cut at a 45 degree angle is called a “french cleat”. The screw on the side is for added stability when using the crank.