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2023-04-22
I built a japanese abacus, a Soroban.
I spent a couple of hours today with a small woodsaw and my powerdrill to finally make a Soroban that I had planned to build for a while now. It consists of simple soft wood for the frame, wooden beads and brass rods for the beads to slide on.
For those curious: The brass rods are 2mm thick and 12mm apart. The beads are 10mm diameter with a 3mm hole. The wood for the top and bottom beams are 10x15mm, the middle beam is 10x2mm.
It was pretty straight forward to build and what I like about it is that it is all press-fit. No glue, no nothing. The brass beams hold everything together and the holes drilled into the wood are tight enough that this won't come apart by accident.
One mistake I made is that I should have gotten 15x15mm wood for the top and bottom beams. As it is, I had to prop up the frame with upholstery nails so that the beads float. Minor inconveniences.
The whole thing looks roughly like this:
══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤══ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ │ │ │ │ │ │ │ │ │ │ │ ══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪══ │ │ │ │ │ │ │ │ │ │ │ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧══
My soroban has twenty rods. This is purely because I got the counting beads in a pack of one hundred, so that is the most rods I could make.
It is imensely satisfying to have made a physical thing, more or less from scratch, that serves a purpose.
I probably won't abandon the calculator on my phone anytime soon but I want to hone my calculation skills on the Soroban. Right now I know how to do addition and substraction on it. I had started to learn multiplication when I stopped practicing, by now I forgot completely how that works. Oh well.
I'm not going to pretend that I'm knowledgable enough to talk about doing math on a Soroban yet but I want to shed a dim light on how it works:
The right-most rod represents the one's digit of a number. The one to the left of that represents the ten's digit and so on.
The four bottom beads are called “earth beads”, when pushed toward the center beam each count one, or ten, or hundred, ... depending on which rod they are.
The single bead on top is called the “heaven bead”, when pushed toward the center beam it counts for five, fifty, five hundred, ...
So if you'd represent the number 5917 on a Soroban, you'd need the four right-most rods and it would look like this:
══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤══ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ │ │ ◀■▶ │ │ │ │ │ │ │ │ ◀■▶ ◀■▶ │ ◀■▶ ══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪═══╪══ │ │ │ │ │ │ │ │ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ │ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ │ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ ◀■▶ │ ◀■▶ ◀■▶ ══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧═══╧══ 0 0 0 0 0 0 0 5 9 1 7
I'm in a happy place right now.
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