A Fortuitous Computer Error

Karina and I went to the pregnancy center last week for a routine checkup. Somebody had hit "logout" on the check-in tablet, preventing us from using it, so we had to ignore the signs and talk to somebody at the desk to let him know we were there. On his desk was a paper circular object which was unmistakably a volvelle. Karina lit up. "What is that on your desk?" she asked.

"Oh, we use this for scheduling," the man replied, sounding amused that we'd noticed it.

"It's a volvelle," she said. "My husband makes those. For cryptography. That's super cool."

At this he laughed out loud. "The things that people find interesting," he said, maybe to himself.

A Proprietary Ecosystem

When we got home, of course I searched the Internet to find a printout of the wheels. Unfortunately, the majority of search results for "pregnancy wheel" provided Javascript scheduling widgets, which didn't even resemble wheels. An image search found some actual volvelles, but these were all sold as complete units, and the source material could not be downloaded (except perhaps as low-resolution pictures).

Curiously the only version I was able to find, in my brief search, that seemed reasonable to print at home, was from a misoprostol provider, informing me how late an abortion the pills were good for. That's capitalism for you, I guess.

So I Made My Own

Anyway, since my job does in fact involve making volvelles for cryptography, I was able to quickly whip up my own version. The source (in hand-written PostScript) is hosted on Github here or you can download it in PostScript or PDF form here.

In case I update this, the Github source is more likely to be up-to-date.