08 June 2019
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 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 geargenerator.com. 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!